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Halorhodospira (Hlr.) halophila strain BN9622 is an extremely halophilic and alkaliphilic phototrophic purple sulfur bacterium isolated from a hypersaline lake in the Libyan Desert whose total salinity exceeded 35% at pH 10.7. Here we present a cryo-EM structure of the native LH1–LH2 co-complex from strain BN9622 at 2.22 Å resolution. Surprisingly, the LH1–LH2 co-complex consists of a double-ring cylindrical structure with the larger LH1 ring encircling a smaller LH2 ring. The Hlr. halophila LH1 contains 18 αβ-subunits and additional bacteriochlorophyll a (BChl a) molecules that absorb maximally at 797 nm. The LH2 ring is composed of 9 αβ-subunits, and the BChl a molecules in the co-complex form extensive intra- and inter-complex networks to allow near 100% efficiency of energy transfer to its surrounding LH1. The additional LH1-B797 BChls a are located in such a manner that they facilitate exciton transfer from monomeric BChls in LH2 to the dimeric BChls in LH1. The structural features of the strain BN9622 LH1–LH2 co-complex may have evolved to allow a minimal LH2 complex to maximize excitation transfer to the core complex and effectively harvest light in the physiologically demanding ecological niche of this purple bacterium. The major photosynthetic apparatus of purple phototrophic bacteria comprises two distinct complexes: the light-harvesting (LH) complex and the reaction center (RC). Here, the authors report a cryo-EM structure of a distinct conjoined LH1–LH2 complex from extremophile Hlr. halophila. [ABSTRACT FROM AUTHOR]

The genome of the mildly thermophilic hot spring purple sulfur bacterium, Allochromatium (Alc.) tepidum, contains a multigene pufBA family that encodes a series of α- and β-polypeptides, collectively forming a heterogeneous light-harvesting 1 (LH1) complex. The Alc. tepidum LH1, therefore, offers a unique model for studying an intermediate phenotype between phototrophic thermophilic and mesophilic bacteria, particularly regarding their LH1 Qy transition and moderately enhanced thermal stability. Of the 16 α-polypeptides in the Alc. tepidum LH1, six α1 bind Ca2+ to connect with β1- or β3-polypeptides in specific Ca2+-binding sites. Here, we use the purple bacterium Rhodospirillum rubrum strain H2 as a host to express Ca2+-bound and Ca2+-free Alc. tepidum LH1-only complexes composed of α- and β-polypeptides that either contain or lack the calcium-binding motif WxxDxI; purified preparations of each complex were then used to test how Ca2+ affects their thermostability and spectral features. The cryo-EM structures of both complexes were closed circular rings consisting of 14 αβ-polypeptides. The Qy absorption maximum of Ca2+-bound LH1 (α1/β1 and α1/β3) was at 894 nm, while that of Ca2+-free (α2/β1) was at 888 nm, indicating that Ca2+ imparts a Qy transition of 6 nm. Crucially for the ecological success of Alc. tepidum, Ca2+-bound LH1 complexes were more thermostable than Ca2+-free complexes, indicating that calcium plays at least two major roles in photosynthesis by Alc. tepidum—improving photocomplex stability and modifying its spectrum. [ABSTRACT FROM AUTHOR]

[Display omitted] • AOB and SOB reduced NH 3 and H 2 S by 38.90 % and 46.24 %, respectively. • Combined addition of microbial agents could reduce the sulfur loss by 34.69%. • The abundance of soxB gene was increased by 1.72 times in the coupling treatment. • Microbial inoculation enhanced the correlation between bacteria and soxB gene. Ammonia (NH 3) and hydrogen sulfide (H 2 S) are the main odor components in the composting process. Controlling their emissions is very important to reduce environmental pollution and improve the quality of composting products. This study explored the effects of functional bacteria on nitrogen and sulfur metabolism in the composting process of food waste (FW) by adding ammonia-oxidizing bacteria (AOB, A treatment), sulfur-oxidizing bacteria (SOB, S treatment), and combined AOB and SOB (AS treatment), respectively. The key bacterial species involved in nitrogen and sulfur transformation were identified, and the intrinsic mechanisms by which ammonia oxidation drove sulfur oxidation during composting were deciphered. Compared with control treatment (CK), the combined addition of functional microorganisms increased the maximum of soxB gene abundance by 1.72 times, thus resulting in the increase in the SO 4 2- content by 44.00 %. AS treatment decreased the cumulative H 2 S emission and total sulfur (TS) loss by 40.24 % and 34.69 %, respectively, meanwhile lowering NH 3 emission. Correlation network analysis showed that the simultaneous addition of AOB and SOB enhanced the correlation between microorganisms and sulfur oxidation genes, and Acinetobacter , Aeribacillus , Brevibacterium and Ureibacillus might be involved in the ammonia oxidation-promoted sulfur oxidation process. In summary, the optimized inoculation strategy of AOB and SOB could drive biological transformation of nitrogen and sulfur by regulating microbial community, ultimately reducing odor emissions and improving sulfur conservation. [ABSTRACT FROM AUTHOR]

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Elemental sulfur is a common product of hydrogen sulfide oxidation in the photic zone of meromictic basins due to the anoxigenic oxidation of hydrogen sulfide by photosynthetic bacteria. The photic zone in the Black Sea is limited to 50–60 m, which is much higher than the upper limit of the hydrogen sulfide zone interface, which is at a depth of 90–100 m in the center of the sea. In peripheral areas of the Black Sea, the depth of the redox interface reaches 150–170 m, where, as expected, photoautotrophic bacteria are rare and in an inactive state. A study of the distribution of elemental sulfur in the Black Sea anoxic zone showed that waters from depths of 180–300 m are light sensitive. This leads to a sharp increase in sulfur concentrations up to 11.3 µmol/kg with background values of 0.15–0.18 µmol/kg under strictly anaerobic conditions. It was found that such a significant increase in elemental sulfur is associated with the activity of photoautotrophic bacteria. The conditions for the existence of photoautotrophic bacteria at depths of 180–300 m in the Black Sea in the absence of light remain unclear. [ABSTRACT FROM AUTHOR]

Features like solar cyclicities and trends as well as grand solar minima are used to attribute natural climate variability to solar forcing on decadal to millennial time scales. Here we focus on ecological responses of a Grand Solar Minimum on annually- laminated lake sediments from Holzmaar (Germany) covering the Homeric Climate Anomaly (HCA). Diatom assemblages and pigments of purple sulphur bacteria (Bphe a) analysed at decadal resolution document well-stratified conditions with relatively low lacustrine productivity prior to the HCA (2950–2750 cal. BP). Colder temperatures, a well-mixed water column and higher primary aquatic productivity established during the HCA (2750–2680 cal. BP) as indicated for Holzmaar by dominance of the planktonic diatom Stephanodiscus minutulus, decreasing Bphe a and peaking total chloropigment concentrations. The termination of the HCA after 2680 cal. BP is marked by additional anthropogenic signals related to deforestation that changed the catchment at the contemporaneous Bronze Age/Iron Age transition. Our high-resolution and well-dated multiproxy study based on varved sediments contributes to a better understanding of decadal-scale responses of aquatic ecosystems to solar forcing and compares well with hypotheses suggested by other investigations indicating colder and more windy climatic conditions as the consequences of a Grand Solar Minimum for mid-latitudes of the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Oil seeds sector is one of the major dynamic components of the agriculture world. Oil seeds such as canola (Brassica napus) require a higher quantity of sulfur (S), which is supplied through inorganic fertilizers. However, the overapplication of agro‐chemicals to get higher yields of crops is harming the soil health. Therefore, the application of bacterial cultures with plant growth‐promoting activity as biofertilizers ensures soil health maintenance and enhances crop productivity. To achieve this aim, the present research was initiated by procuring three sulfur‐oxidizing bacteria (SOBs), namely, SOB 5, SOB 10, and SOB 38, from the Microbiology Department, PAU. In the initial assessment, all three SOB cultures showed resilience to pesticide toxicity at the recommended dosage, with the exception of ridomil. These cultures were later characterized morphologically, biochemically, and at the molecular level using 16s rRNA resulting in their identification as Enterobacter ludwigii strain Remi_9 (SOB 5), Enterobacter hormaechei strain AUH‐ENM30 (SOB 10), and Bacillus sp. 5BM21Y12 (SOB 38). Functional characterization of these SOB cultures revealed their ability to exhibit multifarious plant growth‐promoting traits. Bacillus sp. 5BM21Y12 showed greater functional activity, including high P solubilization (14.903 µg/mL), IAA production (44.28 µg/mL), siderophore production (13.89 µg/mL), sulfate ion production (0.127 mM), ammonia excretion (2.369 µg/mL), and Zn solubilization (22.62 mm). Based on the results of functional and molecular characterization, Bacillus sp. 5BM21Y12 was selected for field trials by formulating different treatments. Composite treatment, T8 (100% S + Bacillus sp. + pesticides) significantly enhanced growth parameters (plant height, root, and shoot biomass), yield attributes (siliqua length, test weight, number of siliqua/plant), yield parameter (total biomass and seed yield), quality parameter (crude protein and oil) as compared to all other sole treatments employed in the field. A combined application of non‐pathogenic Bacillus sp. 5BM21Y12, with good functional activity enhanced yield of crop due to synergistic and additive interaction with fertilizer/pesticides. As biofertilizer application reduces the input of pesticides/fertilizers new inoculant formulations with cell protectors and the development of compatible pesticides should be searched to assure the benefits of integrated treatment. [ABSTRACT FROM AUTHOR]

Mountain lakes are sensitive indicators of anthropogenically driven global change, with lake sediment records documenting increased primary production during the twentieth century. Atmospheric nutrient deposition and warming have been attributed to changes in other Western mountain lakes, however, the intensity of these drivers varies. We analyzed a sediment core representing a 270-year record from Santa Fe Lake, New Mexico, to constrain the southern margin of Rocky Mountain lakes and quantify patterns of change in lake biogeochemistry, production, and diatoms since 1750. Lake sediments were dated using 210Pb and analyzed for carbon (C), nitrogen (N), stable isotopes (δ13C, δ15N), diatoms, and phototrophic pigments. The abundance of cyanobacteria, purple sulfur-reducing bacteria, and diatom pigments were elevated during the stable conditions of the Little Ice Age; these phototrophic groups declined in the late 1800s and reached a minimum by 1950. From 1950 to 2020, sediments recorded an increased abundance of cryptophyte, diatom, and chlorophyte groups. The C and N (percentage dry mass) increased after 1950, whereas δ15N and δ13C values declined. Changes since the mid-twentieth century are contemporaneous with warming trends in the Southwest and modest deposition of atmospheric N. Our findings highlight the geographic variability of mountain lake responses to changing environmental conditions. Highlights: Fossil phototrophic and diatom pigments revealed elevated primary production resulting from increases in cyanobacteria, purple sulfur bacteria, and diatoms during the stable conditions of the Little Ice Age. Primary production declined from the end of the Little Ice Age into the mid-twentieth century. The warming climate after ca. 1950 and, to a lesser extent regional N deposition, drove primary productivity to a historic maximum due to increased chlorophyte and cryptophyte groups. Unlike other Rocky Mountain lakes, regional human activities had little effect on the phototrophic composition and productivity of Santa Fe Lake. [ABSTRACT FROM AUTHOR]

Wheat is one of the primary cereals in most countries, and in recent decades, its cultivation has been significantly impacted by environmental conditions due to climate change. Therefore, an experiment was conducted during the 2020-2021 agricultural year to examine the response of photosynthetic pigments and the yield of different wheat cultivars to the combined application of bacteria and sulfur under rainfed conditions. This factorial experiment was conducted in a randomized complete block design with three replications. The experimental factors included four wheat cultivars: Eivan, Sardari, Homa, and Azar 2, sulfur treatment at two levels: foliar spray with distilled water as a control and foliar spray with sulfur and bacterial treatment at two levels: without inoculation (control) and inoculation with Azospirillum bacteria. The results showed that the highest grain yield (3030 kg/ha) was observed in the Eivan cultivar with the application of Azospirillum bacteria. Inoculation with Azospirillum bacteria increased the grain yield of the Eivan and Sardari cultivars by 17.9% and 42%, respectively, while no statistically significant effect was observed on the grain yield of the Homa and Azar 2 cultivars. The results indicated that sulfur spraying and bacterial application improved photosynthesis. Under rainfed conditions, the Eivan cultivar had significantly higher grain yield compared to the Sardari, Homa, and Azar 2 cultivars and produced a higher yield with bacterial application. Azospirillum bacteria increased leaf photosynthesis. Plant nutrition management and the use of growth-promoting bacteria, with their physiological effects, can be considered strategies for improving yield under rainfed conditions. [ABSTRACT FROM AUTHOR]

Isolating microorganisms from natural environments for cultivation under optimized laboratory settings has markedly improved our understanding of microbial ecology. Artificial growth conditions often diverge from those in natural ecosystems, forcing wild isolates into distinct selective pressures, resulting in diverse eco-physiological adaptations mediated by modification of key phenotypic traits. For motile microorganisms we still lack a biophysical understanding of the relevant traits emerging during domestication and their mechanistic interplay driving short-to-long-term microbial adaptation under laboratory conditions. Using microfluidics, atomic force microscopy, quantitative imaging, and mathematical modeling, we study phenotypic adaptation of Chromatium okenii, a motile phototrophic purple sulfur bacterium from meromictic Lake Cadagno, grown under laboratory conditions over multiple generations. Our results indicate that naturally planktonic C. okenii leverage shifts in cell-surface adhesive interactions, synergistically with changes in cell morphology, mass density, and distribution of intracellular sulfur globules, to suppress their swimming traits, ultimately switching to a sessile lifeform. A computational model of cell mechanics confirms the role of such phenotypic shifts in suppressing the planktonic lifeform. By investigating key phenotypic traits across different physiological stages of lab-grown C. okenii, we uncover a progressive loss of motility during the early stages of domestication, followed by concomitant deflagellation and enhanced surface attachment, ultimately driving the transition of motile sulfur bacteria to a sessile state. Our results establish a mechanistic link between suppression of motility and surface attachment via phenotypic changes, underscoring the emergence of adaptive fitness under laboratory conditions at the expense of traits tailored for natural environments. [ABSTRACT FROM AUTHOR]

Halorhodospira (Hlr.) halochloris is a triply extremophilic phototrophic purple sulfur bacterium, as it is thermophilic, alkaliphilic, and extremely halophilic. The light‐harvesting‐reaction center (LH1–RC) core complex of this bacterium displays an LH1‐Qy transition at 1,016 nm, which is the lowest‐energy wavelength absorption among all known phototrophs. Here we report the cryo‐EM structure of the LH1–RC at 2.42 Å resolution. The LH1 complex forms a tricyclic ring structure composed of 16 αβγ‐polypeptides and one αβ‐heterodimer around the RC. From the cryo‐EM density map, two previously unrecognized integral membrane proteins, referred to as protein G and protein Q, were identified. Both of these proteins are single transmembrane‐spanning helices located between the LH1 ring and the RC L‐subunit and are absent from the LH1–RC complexes of all other purple bacteria of which the structures have been determined so far. Besides bacteriochlorophyll b molecules (B1020) located on the periplasmic side of the Hlr. halochloris membrane, there are also two arrays of bacteriochlorophyll b molecules (B800 and B820) located on the cytoplasmic side. Only a single copy of a carotenoid (lycopene) was resolved in the Hlr. halochloris LH1–α3β3 and this was positioned within the complex. The potential quinone channel should be the space between the LH1–α3β3 that accommodates the single lycopene but does not contain a γ‐polypeptide, B800 and B820. Our results provide a structural explanation for the unusual Qy red shift and carotenoid absorption in the Hlr. halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known. [ABSTRACT FROM AUTHOR]

The large leakage accidents of heavy metals from industrial facilities pose a serious environmental problem; however, not enough studies have been conducted to assess the long-term ecological risk associated with such accidents. This study evaluated changes in the bacterial communities within river sediment and identified the key functional microorganisms responding to the 2012 cadmium contamination incident in the Long River, Guangxi Province, China. Results revealed that after a prolonged period of pollution accidents, cadmium pollution still had a discernible effect on the bacterial communities of the river sediment. In comparison to the control site (S1), the bacterial α-diversity in sediments from the accident area (S3) and its downstream (S5) showed a significant increase following the incident. In the control site, Burkholderiaceae was dominant, while in S3 and S5, Pedosphaeraceae, Nitrosomonadaceae, Nitrospiraceae and Geobacteraceae were significantly increased. Sulfur bacteria were found to be more responsive to this cadmium contamination than other bacteria. At site S3, the abundances of Sulfuricurvum, Sulfurifustis, Thioalkalispira, Desulfobacteraceae and Desulfarculaceae were hundreds of times higher than at site S1, indicating an intensification of sulfur cycling processes. The functional prediction implied that cadmium pollution may promote methane oxidation coupled with sulfate reduction reactions and altered the processes of nitrification and denitrification. Environmental factors influencing the microbial community included the levels of metals (cadmium, arsenic, iron) in sediment, as well as other sediment characteristics like temperature and electrical conductivity. These findings contribute to our understanding of the long-term ecological consequences of environmental pollution in river ecosystems. [ABSTRACT FROM AUTHOR]

Since the dawn of civilization, sandstone has been a fantastic building material. Numerous causes have been observed in the past for sandstone damage or deterioration, one of which is sulphur-oxidizing bacteria (SOB) and cyanobacteria. In general, SOB is present in the soil, air, water, humidity, and human activity. The oxidation of sulphur compounds, such as hydrogen sulphide, thiosulphate, or elements of sulphur, provides energy for SOB. These microorganisms contribute to the decay of buildings materials, especially those made of stone, metal, or concrete. The sulphur oxidizing process affects the mechanical properties of sandstone. Mechanical properties are related to strength. Losses of mechanical properties may be the reason for deflection, cracking, collapse, and catastrophic failure of sandstone. Monitoring and evaluation gives an idea about the behavior of structure and the prevention of catastrophic failure. This research paper contains the application of electromechanical impedance with surface bonded Piezoelectric Lead Zirconate Titanate. The sandstone samples and soil samples have been collected from the historical site. Two sets of cylindrical types of sandstone specimens have been used in experimental work. The conductance signature and susceptance signature have been measured every six months. The variation and shifting of the signature curve have been used to identify the structural behavioral change. Statistical methods like the root mean square deviation have been used for the quantification of damage. An equitation has been generated on the basis of the percentage root mean square deviation to quantify the prediction of damages. [ABSTRACT FROM AUTHOR]

Anoxygenic phototrophic bacteria (green and purple sulfur bacteria) thrive in anoxic environments where light penetrates a sulfide-containing (euxinic) water column. Genomic data and photosynthetic bacterial carotenoid pigments should provide complementary information on the spatio-temporal dynamics of anoxygenic phototrophs in modern euxinic environments. In turn, these contemporary depositional settings often serve as analogues for ancient counterparts. However, in some modern environments, DNA-informed patterns of phototrophic sulfur bacteria occurrence do not match distributions of their carotenoid inventories. One possible explanation for these seemingly incompatible observations is that the rapid sulfurization of carotenoids and incorporation into macromolecules via multiple carbon–sulfur bonds prevents or confounds their detection by conventional means. Here, to evaluate this conundrum, we revisit some representative contemporary euxinic environments where anoxygenic phototrophic bacteria have mostly been detected based on genomic analyses. Although free intact carotenoids are sporadically detected in surface sediments, their distributions do not reveal a complete picture. Exogenously sourced fossil carotenoids (e.g., paleorenieratane) is an additional complication. Carotenoid inventories obtained by desulfurization with Raney nickel, on the other hand, stand in stark contrast to those present as free lipids. In particular, sulfur-linked carotenoids present in euxinic lake sediments provide a more complete picture of compositions of anoxygenic sulfur bacterial communities and account for discrepancies reported in previous studies. We observe a closer alignment between genomic data and patterns of sulfurized carotenoids and, importantly, our results highlight how sulfurization serves as a pathway for the rapid modification of highly functionalised lipids and their sequestration into the macromolecular component of sediment extracts. [ABSTRACT FROM AUTHOR]

Background: Sulphur (S) is an essential macronutrient required for growth and development of plants. This study was carried out to investigate the effect of Bio Sulphur Granules (BSG) developed with elemental sulphur and sulphur oxidizing bacteria (SOB) on the antioxidative defense system in blackgram under sulphur deficient calcareous soil. Methods: Bio Sulphur Granule (BSG) was developed using ES plus SOB and its efficacy was tested in a pot experiment with blackgram as a test crop from April to June 2022. Plant samples were collected and analyzed in the laboratory for anti-oxidant status of blackgram, how sulphate stress affects the physiological and metabolic processes of plants, which in- turn affects crop yield. Result: Photo assimilatory pigments were decreased and carbohydrates (sugar and starch) were accumulated in leaves of no sulphur treated plants. Hydrogen peroxide in without S supplied plant caused oxidative damage in plants, which also evident by the increase in activity of super oxide dismutase, catalase, peroxidase and ascorbate. The findings showed that by applying S as BSG granules (ES @ 40 kg S ha-1 + Methylobacterium thiocyanatum VRI7-A4) to S-deficient calcareous vertisols might prevent the oxidative damage of plant cells there by improve the growth of blackgram by S-oxidation. [ABSTRACT FROM AUTHOR]

Chemosynthetic microorganisms facilitate microbialite development in many caves throughout the world. In Youqin Cave and Tian'e Cave, located in the Carboniferous–Triassic carbonates on the South China Block, five Quaternary speleothems (stalagmite, stalactite and cave pearl) that are 2.3 to 11.0 cm long were examined for their petrographic, geochemical and microbiological features to reveal how chemotrophs contribute to microbialite growth. In the speleothems, millimetre‐sized stromatolites, thrombolites and calcified microbial mats are characterized by alternating light, calcitic microlaminae and dark, clay and organic‐rich calcite microlaminae. Filamentous (reticulate, smooth, nodular and helical), coccoid and bacilliform microbes, originally carried into the caves from surface soils, are more common in the dark microlaminae/clots than in the light microlaminae. 16S rRNA gene sequencing shows that the biotas in the microbialites are dominated by chemoorganotrophic heterotrophic bacteria, including primarily Sphingomonas, Crossiella and Acinetobacter, and rare Archaea. Diverse metabolic pathways of these prokaryotes, including ureolysis, denitrification and nitrite ammonification, contributed to increases in localized pH and/or dissolved inorganic carbon in these microenvironments, prompting carbonate precipitation. Development of the cave microbialites was probably controlled by the evolution of the cave microbial community as environmental conditions changed. Microbialite growth was probably mediated by the microorganisms that flourished on the speleothem surfaces during periods of low drip water rates and slow calcite precipitation. The change from microstromatolites to microthrombolites was probably linked to a decrease in cell populations in the microbial communities. These cave microbialites provide clear insights regarding the biogenicity and growth mechanisms of chemosynthetic microbialites. Given their association with chemolithotrophic activities that can date back to the Meso‐Archean, cave microbialites provide insights into the biogenicity and growth mechanisms of chemosynthesis‐based microbialites throughout geological history. [ABSTRACT FROM AUTHOR]

Sulfur oxidizing bacteria (SOB) play a key role in sulfur cycling in mine tailings impoundment (TI) waters, where sulfur concentrations are typically high. However, our understanding of SOB sulfur cycling via potential S oxidation pathways (sox, rdsr, and S4I) in these globally ubiquitous contexts, remains limited. Here, we identified TI water column SOB community composition, metagenomics derived metabolic repertoires, physicochemistry, and aqueous sulfur concentration and speciation in four Canadian base metal mine, circumneutral-alkaline TIs over four years (2016 - 2019). Identification and examination of genomes from nine SOB genera occurring in these TI waters revealed two pH partitioned, metabolically distinct groups, which differentially influenced acid generation and sulfur speciation. Complete sox (csox) dominant SOB (e.g., Halothiobacillus spp., Thiomonas spp.) drove acidity generation and S2O32- consumption via the csox pathway at lower pH (pH ~5 to ~6.5). At circumneutral pH conditions (pH ~6.5 to ~8.5), the presence of non-csox dominant SOB (hosting the incomplete sox, rdsr, and/or other S oxidation reactions; e.g. Thiobacillus spp., Sulfuriferula spp.) were associated with higher [S2O32-] and limited acidity generation. The S4I pathway part 1 (tsdA; S2O32- to S4O62-), was not constrained by pH, while S4I pathway part 2 (S4O62- disproportionation via tetH) was limited to Thiobacillus spp. and thus circumneutral pH values. Comparative analysis of low, natural (e.g., hydrothermal vents and sulfur hot springs) and high (e.g., Zn, Cu, Pb/Zn, and Ni tailings) sulfur systems literature data with these TI results, reveals a distinct TI SOB mining microbiome, characterized by elevated abundances of csox dominant SOB, likely sustained by continuous replenishment of sulfur species through tailings or mining impacted water additions. Our results indicate that under the primarily oxic conditions in these systems, S2O32- availability plays a key role in determining the dominant sulfur oxidation pathways and associated geochemical and physicochemical outcomes, highlighting the potential for biological management of mining impacted waters via pH and [S2O32-] manipulation. [ABSTRACT FROM AUTHOR]

The bacterial light-dependent energy metabolism can be divided into two types: oxygenic and anoxygenic photosynthesis. Bacterial oxygenic photosynthesis is similar to plants and is characteristic for cyanobacteria. Bacterial anoxygenic photosynthesis is performed by anoxygenic phototrophs, especially green sulfur bacteria (GSB; family Chlorobiaceae) and purple sulfur bacteria (PSB; family Chromatiaceae). In anoxygenic photosynthesis, hydrogen sulfide ( H2S) is used as the main electron donor, which differs from plants or cyanobacteria where water is the main source of electrons. This review mainly focuses on the microbiology of GSB, which may be found in water or soil ecosystems where H2S is abundant. GSB oxidize H2S to elemental sulfur. GSB possess special structures—chlorosomes—wherein photosynthetic pigments are located. Chlorosomes are vesicles that are surrounded by a lipid monolayer that serve as light-collecting antennas. The carbon source of GSB is carbon dioxide, which is assimilated through the reverse tricarboxylic acid cycle. Our review provides a thorough introduction to the comparative eco-physiology of GSB and discusses selected application possibilities of anoxygenic phototrophs in the fields of environmental management, bioremediation, and biotechnology. [ABSTRACT FROM AUTHOR]

One of the greatest challenges encountered by enteric pathogens is responding to rapid changes of nutrient availability in host. However, the mechanisms by which pathogens sense gastrointestinal signals and exploit available host nutrients for proliferation remain largely unknown. Here, we identified a two-component system in Vibrio parahaemolyticus, TtrRS, which senses environmental tetrathionate and subsequently activates the transcription of the ttrRS-ttrBCA-tsdBA gene cluster to promote V. parahaemolyticus colonization of adult mice. We demonstrated that TsdBA confers the ability of thiosulfate oxidation to produce tetrathionate which is sensed by TtrRS. TtrRS autoregulates and directly activates the transcription of the ttrBCA and tsdBA gene clusters. Activated TtrBCA promotes bacterial growth under micro-aerobic conditions by inducing the reduction of both tetrathionate and thiosulfate. TtrBCA and TsdBA activation by TtrRS is important for V. parahaemolyticus to colonize adult mice. Therefore, TtrRS and their target genes constitute a tetrathionate-responsive genetic circuit to exploit the host available sulfur compounds, which further contributes to the intestinal colonization of V. parahaemolyticus. Author summary: Access to host nutrients is regarded as a critical step for the pathogen infection. However, the human gastrointestinal tract is colonized by an enormous number of microbes, which limits pathogens' access to nutrient supplies. Sulfur is one of the most abundant elements on Earth and is also essential to all living organisms. The mechanisms by which bacteria, especially intestinal pathogens, regulate the bioavailability of utilizable sulfur in the host are poorly understood. Here, we characterized a tetrathionate-responsive genetic circuit, which was involved in the utilization of sulfur compounds including tetrathionate and thiosulfate in V. parahaemolyticus, and thus contributed to the bacterial intestinal colonization. Our study provides new insight into the ability of bacterial pathogens to sense gastrointestinal signals and exploit host nutrients for their colonization, which contributes to a better understanding of the pathogenesis of enteric pathogens. [ABSTRACT FROM AUTHOR]

The climate change and consequent degradation of soil and water resources have led to difficult conditions for farmers; thus, they should make intelligent decisions to face these statuses. Managing soil nutrient and mineral uptake by plants and its feasibility under harsh environment must be considered. Therefore, the present research was conducted to investigate the response of pomegranate variety Shishe Kab to Thiobacillus bacteria (B) and sulfur (S) fertilization. Treatments included sulfur fertilization (three levels: 0, 500 and 1000 g−1 tree) and inoculation with Thiobacillus bacteria (two levels: inoculated and non-inoculated). Totally, sulfur fertilization and inoculation with bacteria improved physiological and biochemical aspects and fruit production of pomegranate. Supplying S decreased soil pH, which the lowest value (5.2) was recorded in 500 g S tree−1 when accompanied with bacteria. Soil electrolyte leakage (EL) increased, when sulfur incorporated or when bacteria added to the soil. The interactive effects of B × S was significant on fruit diameter and weight, chlorophyll (Chl), carotenoid and potassium content, which were improved, although non-inoculated plants also showed high values of potassium content. Anthocyanin and total carbohydrate improved when bacteria inoculation was done; however, total acidity (TA) and total soluble solids (TSS) showed a significant decrease. The EL variable significantly decreased and tissue water content increased in this experiment, when inoculation or sulfur fertilization was used. The results obtained from present study emphasized on the necessity of using sulfur and Thiobacillus bacteria in increasing growth and yield and also chilling tolerance of pomegranate trees. From the experiment we found that supplying sulfur alone or accompanied with Thiobacillus bacteria gave the amazing results, lead to increase plant growth and development, yield increase and biochemical changes that are helpful under harsh environmental conditions, specifically cold and freezing stresses. [ABSTRACT FROM AUTHOR]

A study was conducted in sandy clay loam soils in a subtropical zone of Bihar to evaluate the effect of frequent application of organic amendments on sulphur fractions. Different organic amendments, including farmyard manure (FYM), vermicompost, azotobacter, phosphate solubilizing bacteria (PSB), panchagawya, and neem cake, were applied through nine treatments that resulted in a significant increase of water-soluble S, available S, heat-soluble S, adsorbed S, and organic S in organic treatment compared to the recommended dose of fertilizer (RDF) and control treatment. The maximum increment was observed in the treatment where the recommended dose of nitrogen was replaced by 75% recommended dose of nitrogen substituted farmyard manure + 25% recommended dose of nitrogen (vermicompost) along with azotobacter + PSB + one foliar spray of panchagawya. The total S content varied widely from 382 to 736 mg kg-1. Increment in all the forms of sulphur is observed as a result of the application of different organic nutrient sources. All the forms of sulphur share a mutual positive and significant correlation with each other. Regression analysis suggested that the availability of sulphur was dominated by organic sulphur, which alone can explain 97.8% of the variation in availability of available sulphur in soil. [ABSTRACT FROM AUTHOR]

Purple sulfur bacteria (PSB) are capable of anoxygenic photosynthesis via oxidizing reduced sulfur compounds and are considered key drivers of the sulfur cycle in a range of anoxic environments. In this study, we show that Allochromatium vinosum (a PSB species) is capable of autotrophic growth using pyrite as the electron and sulfur source. Comparative growth profile, substrate characterization, and transcriptomic sequencing data provided valuable insight into the molecular mechanisms underlying the bacterial utilization of pyrite and autotrophic growth. Specifically, the pyrite-supported cell cultures ("py"') demonstrated robust but much slower growth rates and distinct patterns from their sodium sulfide-amended positive controls. Up to ~200-fold upregulation of genes encoding various c- and b-type cytochromes was observed in "py," pointing to the high relevance of these molecules in scavenging and relaying electrons from pyrite to cytoplasmic metabolisms. Conversely, extensive downregulation of genes related to LH and RC complex components indicates that the electron source may have direct control over the bacterial cells' photosynthetic activity. In terms of sulfur metabolism, genes encoding periplasmic or membrane-bound proteins (e.g., FccAB and SoxYZ) were largely upregulated, whereas those encoding cytoplasmic proteins (e.g., Dsr and Apr groups) are extensively suppressed. Other notable differentially expressed genes are related to flagella/fimbriae/pilin(+), metal efflux(+), ferrienterochelin(-), and [NiFe] hydrogenases(+). Characterization of the biologically reacted pyrite indicates the presence of polymeric sulfur. These results have, for the first time, put the interplay of PSB and transition metal sulfide chemistry under the spotlight, with the potential to advance multiple fields, including metal and sulfur biogeochemistry, bacterial extracellular electron transfer, and artificial photosynthesis. [ABSTRACT FROM AUTHOR]

Microorganisms have inhabited the oceans since the dawn of Earth. Some of them have organic walls and some produce mineral tests that are usually composed of carbonate minerals or silica. They can therefore be preserved with original parts during sedimentary deposition or fossilized through permineralization or carbonization processes. The most common marine fossil groups studied by micropaleontologists are cyanobacteria, coccolithophores, dinoflagellates, diatoms, silicoflagellates, radiolarians, foraminifers, red and green algae, ostracods, and pteropods. Dormant or reproductive cysts can also be used for determinations of the fossil microbiota. Microfossils can be studied in petrographic slides prepared from rocks or separated from loosely consolidated rocks by disaggregation or dissolution and wet sieving. Their presence is sometimes recognized by biomarkers. Transmitted light microscopy and reflected light stereomicroscopy are necessary for micropaleontological studies whereas scanning electronic microscopy (SEM) aids research on the tiniest fossils and reveals fine skeletal details. Microorganisms have influenced the oxygenation of water and the atmosphere, as well as Earth's carbon cycle and have contributed to the formation of sedimentary rocks. By studying microfossils, paleontologists depict the age of the rock and identify depositional environments. Such studies help us recognize periods of stress in Earth's history and understand their influence on living organisms. Biogenic rocks, made of microfossils, can be used as raw materials, such as fossil fuels, building stone, or additives for the food industry, agricultural, or cosmetic purposes. [ABSTRACT FROM AUTHOR]

The relic Lake Mogilnoe, separated from the Barents Sea by a sand and pebble dam, is located in the high Arctic on the Kildin island (Murmansk region). This lake is a classic example of a meromictic basin of marine origin. The data obtained during the 2018 expedition showed changes in the hydrochemical regime of the lake that have occurred over the past 20 years. Sulfide concentration in the monimolimnion of the lake was as high as 140 mg/L. A tendency for salinization of the surface waters to 7 g/L has been noted. The Lake Mogilnoe is characterized by a discrepancy between the halocline and thermocline levels. The chemocline zone in the lake is below the halocline level. In a narrow oxygen-containing layer between 3 and 7.5 m, aerobic microflora of the marine type and marine fauna were present. The bacterial plate was formed at the boundary of the sulfide layer at ~8 m and mainly consisted of green sulfur bacteria (GSB). Brown-colored GSB species containing bacteriochlorophyll e were predominant. The previously formed concept of anaerobic phototrophic bacteria (APB) biodiversity based on morphological characteristics was modified using metagenomic data obtained by analyzing DNA from two samples of lake water in the chemocline zone, and was also supplemented by identifying new GSB species. Molecular diagnostic data confirmed the absolute dominance of the brackish species of GSB Chlorobium phaeovibrioides. This is the first isolation and identification of brown- and green-colored Prosthecochloris aestuarii morphotypes from Lake Mogilnoe, as well as of bacteriochlorophyll c-containing Prosthecochloris sp. The taxonomic position of Pelodyction phaem, which was constantly present in the Lake Mogilnoe, is discussed in detail. Despite the partial isolation of the ecosystem of Lake Mogilnoe from the Barents Sea, the main properties of the dominant GSB species and Prosthecochlori aestuarii turned out to be similar to those of the phylotypes living in lakes on the White Sea coast. [ABSTRACT FROM AUTHOR]

The family Beggiatoaceae is currently represented by 25 genera in the Genome Taxonomy Database, of which only 6 have a definite taxonomic status. Two metagenome-assembled genomes (MAGs), WS_Bin1 and WS_Bin3, were assembled from metagenomes of the sulfur mats coating laminaria remnants in the White Sea. Using the obtained MAGs, we first applied phylogenetic analysis based on whole-genome sequences to address the systematics of Beggiatoaceae, which clarify the taxonomy of this family. According to the average nucleotide identity (ANI) and average amino acid identity (AAI) values, MAG WS_Bin3 was assigned to a new genus and a new species in the family Beggiatoaceae, namely, 'Candidatus Albibeggiatoa psychrophila' gen. nov., sp. nov., thus providing the revised taxonomic status of the candidate genus 'BB20'. Analysis of 16S rRNA gene homology allowed us to identify MAG WS_Bin1 as the only currently described species of the genus 'Candidatus Parabeggiatoa', namely, 'Candidatus Parabeggiatoa communis', and consequently assign the candidate genus 'UBA10656', including four new species, to the genus 'Ca. Parabeggiatoa'. Using comparative whole-genome analysis of the members of the genera 'Candidatus Albibeggiatoa' and 'Ca. Parabeggiatoa', we expanded information on the central pathways of carbon, sulfur and nitrogen metabolism in the family Beggiatoaceae. [ABSTRACT FROM AUTHOR]

This study investigates the impact of conserved histidine (His) residue mutations on the adenosine 5′-phosphosulfate (APS) reductase enzymes Pseudomonas aeruginosa APR (PaAPR) and Enteromorpha intestinalis APR (EiAPR), focusing on the effects of His-to-alanine (Ala) and His-to-arginine (Arg) substitutions on enzyme activity, iron–sulfur [4Fe-4S] cluster stability, and APS binding affinity. Using recombinant His-tagged wild-types (WTs) and variants expressed in Escherichia coli, analyses revealed that both PaAPR and EiAPR enzymes exhibit a distinct absorption peak associated with their [4Fe-4S] clusters, which are critical for their catalytic functions. Notably, the His-to-Ala variants displayed reduced enzymatic activities and lower iron and sulfide contents compared to their respective WTs, suggesting alterations in the iron–sulfur cluster ligations and thus affecting APS reductase catalysis. In contrast, His-to-Arg variants maintained similar activities and iron and sulfide contents as their WTs, highlighting the importance of a positively charged residue at the conserved His site for maintaining structural integrity and enzymatic function. Further kinetic analyses showed variations in Vmax and Km values among the mutants, with significant reductions observed in the His-to-Ala variants, emphasizing the role of the conserved His in enzyme stability and substrate specificity. This study provides valuable insights into the structural and functional significance of conserved His residues in APS reductases, contributing to a better understanding of sulfur metabolism and its regulation in bacterial and plant systems. Future investigations into the structural characterization of these enzymes and the exploration of other critical residues surrounding the [4Fe-4S] cluster are suggested to elucidate the complete mechanism of APS reduction and its biological implications. [ABSTRACT FROM AUTHOR]

The metabolic process of purple sulphur bacteria's anoxygenic photosynthesis has been primarily studied in Allochromatium vinosum, a member of the Chromatiaceae family. However, the metabolic processes of purple sulphur bacteria from the Ectothiorhodospiraceae and Halorhodospiraceae families remain unexplored. We have analysed the proteome of Halorhodospira halophila, a member of the Halorhodospiraceae family, which was cultivated with various sulphur compounds. This analysis allowed us to reconstruct the first comprehensive sulphur‐oxidative photosynthetic network for this family. Some members of the Ectothiorhodospiraceae family have been shown to use arsenite as a photosynthetic electron donor. Therefore, we analysed the proteome response of Halorhodospira halophila when grown under arsenite and sulphide conditions. Our analyses using ion chromatography‐inductively coupled plasma mass spectrometry showed that thioarsenates are chemically formed under these conditions. However, they are more extensively generated and converted in the presence of bacteria, suggesting a biological process. Our quantitative proteomics revealed that the SoxAXYZB system, typically dedicated to thiosulphate oxidation, is overproduced under these growth conditions. Additionally, two electron carriers, cytochrome c551/c5 and HiPIP III, are also overproduced. Electron paramagnetic resonance spectroscopy suggested that these transporters participate in the reduction of the photosynthetic Reaction Centre. These results support the idea of a chemically and biologically formed thioarsenate being oxidized by the Sox system, with cytochrome c551/c5 and HiPIP III directing electrons towards the Reaction Centre. [ABSTRACT FROM AUTHOR]

A high concentration of hydrogen sulfide (H2S) released from pig farming is one of the major environmental problems affecting surrounding communities. In modern pig farms, the bioscrubber is used to eliminate H2S, which is found to be driven mainly by the sulfuroxidizing bacteria (SOB) community. Therefore, in this study, molecular biology techniques such as next-generation sequencing (NGS) and DNA microarray are proposed to study the linkage between enzyme activity and the abundance of the SOB community. The starting sludge (SFP1) and recirculating sludge (SFP2) samples were collected from the bioscrubber reactor in the pig farm. The abundance of microbial populations between the two sampling sites was considered together with the gene expression results of both soxABXYZ and fccAB. Based on the NGS analysis, the members of phylum Proteobacteria such as Halothiobacillus, Acidithiobacillus, Thiothrix, Novosphingobium, Sulfuricurvum, Sulfurovum, Sulfurimonas, Acinetobacter, Thiobacillus, Magnetospirillum, Arcobacter, and Paracoccus were predominantly found in SFP2. The presence of Cyanobacteria in SFP pig farms is associated with increased biogas yields. The microarray results showed that the expression of soxAXBYZ and fccAB genes involved in the oxidation of sulfide to sulfate was increased in Halothiobacillus, Paracoccus, Acidithiobacillus, Magnetospirillum, Sphingobium, Thiobacillus, Sulfuricurvum, Sulfuricurvum, Arcobacter, and Thiothrix. Both NGS and DNA microarray data supported the functional roles of SOB in odor elimination and the oxidation of H2S through the function of soxABXYZ and fccAB. The results also identified the key microbes for H2S odor treatment, which can be utilized to monitor the stability of biological treatment systems and the toxicity of sulfide minerals by oxidation. [ABSTRACT FROM AUTHOR]

Calcium ions play a dual role in expanding the spectral diversity and structural stability of photocomplexes from several Ca2+-requiring purple sulfur phototrophic bacteria. Here, metal-sensitive structural changes in the isotopically labeled light-harvesting 1 reaction center (LH1-RC) complexes from the thermophilic purple sulfur bacterium Thermochromatium (Tch.) tepidum were investigated by perfusion-induced attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy. The ATR-FTIR difference spectra induced by exchanges between native Ca2+ and exogenous Ba2+ exhibited interconvertible structural and/or conformational changes in the metal binding sites at the LH1 C-terminal region. Most of the characteristic Ba2+/Ca2+ difference bands were detected even when only Ca ions were removed from the LH1-RC complexes, strongly indicating the pivotal roles of Ca2+ in maintaining the LH1-RC structure of Tch. tepidum. Upon 15N-, 13C- or 2H-labeling, the LH1-RC complexes exhibited characteristic 15N/14N-, 13C/12C-, or 2H/1H-isotopic shifts for the Ba2+/Ca2+ difference bands. Some of the 15N/14N or 13C/12C bands were also sensitive to further 2H-labelings. Given the band frequencies and their isotopic shifts along with the structural information of the Tch. tepidum LH1-RC complexes, metal-sensitive FTIR bands were tentatively identified to the vibrational modes of the polypeptide main chains and side chains comprising the metal binding sites. Furthermore, important new IR marker bands highly sensitive to the LH1 BChl a conformation in the Ca2+-bound states were revealed based on both ATR-FTIR and near-infrared Raman analyses. The present approach provides valuable insights concerning the dynamic equilibrium between the Ca2+- and Ba2+-bound states statically resolved by x-ray crystallography. [ABSTRACT FROM AUTHOR]

The organic-rich mudstones and dolostones of the Permian Fengcheng Formation (Fm.) are typically alkaline lacustrine source rocks, which are typified by impressively abundant β-carotane. Abundant bcarotane has been well acknowledged as an effective indicator of biological sources or depositional environments. However, the specific biological sources of β-carotane and the coupling control of biological sources and environmental factors on the enrichment of β-carotane in the Fengcheng Fm. remains obscure. Based on a comprehensive investigation of the bulk, molecular geochemistry, and organic petrology of sedimentary rocks and the biochemistry of phytoplankton in modern alkaline lakes, we proposed a new understanding of the biological precursors of β-carotane and elucidated the enrichment mechanism of β-carotane in the Fengcheng Fm. The results show that the biological precursors crucially control the enrichment of β-carotane in the Fengcheng Fm. The haloalkaliphilic cyanobacteria are the primary biological sources of β-carotane, which is suggested by a good positive correlation between the 2-methylhopane index, 7- + 8-methyl heptadecanes/Cmax, C29%, and β-carotane/Cmax in sedimentary rocks and the predominance of cyanobacteria with abundant β-carotene in modern alkaline lakes. The enrichment of β-carotane requires the reducing condition, and the paleoredox state that affects the enrichment of β-carotane appears to have a threshold. The paleoclimate conditions do not considerably impact the enrichment of β-carotane, but they have some influence on the water's paleosalinity by affecting evaporation and precipitation. While it does not directly affect the enrichment of β-carotane in the Fengcheng Fm., paleosalinity does have an impact on the cyanobacterial precursor supply and the preservation conditions. [ABSTRACT FROM AUTHOR]

It was generally postulated that when intracellular free iron content is elevated in bacteria, the ferric uptake regulator (Fur) binds its corepressor a mononuclear ferrous iron to regulate intracellular iron homeostasis. However, the proposed ironbound Fur had not been identified in any bacteria. In previous studies, we have demonstrated that Escherichia coli Fur binds a [2Fe-2S] cluster in response to elevation of intracellular free iron content and that binding of the [2Fe-2S] cluster turns on Fur as an active repressor to bind a specific DNA sequence known as the Fur-box. Here we find that the iron--sulfur cluster assembly scaffold protein IscU is required for the [2Fe-2S] cluster assembly in Fur, as deletion of IscU inhibits the [2Fe- 2S] cluster assembly in Fur and prevents activation of Fur as a repressor in E. coli cells in response to elevation of intracellular free iron content. Additional studies reveal that IscU promotes the [2Fe-2S] cluster assembly in apo-form Fur and restores its Fur-box binding activity in vitro. While IscU is also required for the [2Fe-2S] cluster assembly in the Haemophilus influenzae Fur in E. coli cells, deletion of IscU does not significantly affect the [2Fe-2S] cluster assembly in the E. coli ferredoxin and siderophore-reductase FhuF. Our results suggest that IscU may have a unique role for the [2Fe-2S] cluster assembly in Fur and that regulation of intracellular iron homeostasis is closely coupled with iron--sulfur cluster biogenesis in E. coli. [ABSTRACT FROM AUTHOR]

In the present study, three purple non sulphur bacterial strains were isolated from water and soil samples and were characterised. The three bacterial strains were identified as Rhodopsuedomonas palustris RM01, Rhodopsuedomonas rhenobacensis RM02 and Rhodopsuedomonas palustris RM03 strains. All the three Rhodopseudomonas species strains were nonmotile and the absorption spectral characters revealed the presence of bacteriochlorophyll "a" by ultra-visible spectroscopy. Rhodopseudomonas palustris RM01 showed an absorption maxima at 673, 806 and 865 nm) and the type of carotenoids as spirilloxanthin (absorption maxima at 389, 474, 502, 592 and 530 nm), Rhodopseudomonas rhenobacensis RM02 absorption maxima have seen at 806 and 867 nm and the type of carotenoids as spirilloxanthin (absorption maxima at 382, 473, 503, 591 and 530 nm) and Rhodopseudomonas palustris RM03 absorption maxima was at 759, 805 and 874 nm) and the type of carotenoids as spirilloxanthin (absorption maxima at 376, 492 and 591 nm). RM01, RM02, and RM03 strains were shown a dry biomass yield was 12.1grams, 16.8grams and 13.6grams dry weight per litre, respectively. All the isolated PNSB strains could grow in a range of 6-7 pH tested. Sequence data of the strain was deposited in NCBI (National Centre for Biotechnology Information). These three bacteria Rhodopseudomonas palustris RM01, Rhodopseudomonas. Rhenobacensis RM02 and Rhodopseudomonas palustris RM03 have optimal growth at 28°C & 30°C respectively. Further morphological characterization of these three strains were carried out on the basis of microscopic observations, SEM studies, colour of cell suspensions, absorption spectral characters, organic and inorganic substrate utilization, vitamin requirement, temperature growth and biomass production and 16S rRNA gene sequencing analysis. They were identified and named as Rhodopseudomonas palustris RM01, Rhodopseudomonas rhenobacensis RM02 and Rhodopseudomonas palustris RM03. These were further screened for biomass production. [ABSTRACT FROM AUTHOR]

This report describes acidic microbial mats containing cyanobacteria that are strongly associated to precipitated minerals in the source area of Río Tinto. Río Tinto (Huelva, Southwestern Spain) is an extreme acidic environment where iron and sulfur cycles play a fundamental role in sustaining the extremely low pH and the high concentration of heavy metals, while maintaining a high level of microbial diversity. These multi-layered mineral deposits are stable all year round and are characterized by a succession of thick greenish-blue and brownish layers mainly composed of natrojarosite. The temperature and absorbance above and below the mineral precipitates were followed and stable conditions were detected inside the mineral precipitates. Different methodologies, scanning and transmission electron microscopy, immunological detection, fluorescence in situ hybridization, and metagenomic analysis were used to describe the biodiversity existing in these microbial mats, demonstrating, for the first time, the existence of acid-tolerant cyanobacteria in a hyperacidic environment of below pH 1. Up to 0.46% of the classified sequences belong to cyanobacterial microorganisms, and 1.47% of the aligned DNA reads belong to the Cyanobacteria clade. [ABSTRACT FROM AUTHOR]

Biological processes in the Proterozoic Ocean are often inferred from modern oxygen‐deficient environments (MODEs) or from stable isotopes in preserved sediment. To date, few MODE studies have simultaneously quantified carbon fixation genes and attendant stable isotopic signatures. Consequently, how carbon isotope patterns reflect these pathways has not been thoroughly vetted. Addressing this, we profiled planktonic productivity and quantified carbon fixation pathway genes and associated organic carbon isotope values (δ13CPOC) of size‐fractionated (0.2–2.7 and >2.7 μm) particulate matter from meromictic Fayetteville Green Lake, NY, USA. The high‐O2 Calvin‐Benson‐Bassham (CBB) gene (cbbL) was most abundant in the <2.7 μm size fraction in shallow oxic and deep hypoxic waters, corresponding with cyanobacterial and eukaryote algal populations. The low‐O2 CBB gene (cbbM) was most abundant near the lower oxycline boundary in the larger size fraction, coincident with purple sulfur bacteria populations. The reverse citric acid cycle gene (aclB) was equally abundant in both size fractions in the deepest photic zone, coinciding with green sulfur bacteria populations. Methane coenzyme reductase A (mcrA), of anaerobic methane cyclers, was most abundant at the lower oxycline boundary in both size fractions, coinciding with Methanoregula populations. δ13CPOC values overlapped with the high‐O2 CBB fixation range except for two negative excursions near the lower oxycline boundary, likely reflecting assimilation of isotopically‐depleted groundwater‐derived carbon by autotrophs and sulfate‐reducers. Throughout aphotic waters, δ13CPOC values of the large size fraction became 13C‐enriched, likely reflecting abundant purple sulfur bacterial aggregates. Eukaryote algae‐ or cyanobacteria‐like isotopic signatures corresponded with increases in cbbL, cbbM, and aclB, and enrichment of exopolymer‐rich prokaryotic photoautotrophs aggregates. Results suggest that δ13CPOC values of preserved sediments from areas of the Proterozoic Ocean with sulfidic photic zones may reflect a mixture of alternate carbon‐fixing populations exported from the deep photic zone, challenging the paradigm that sedimentary stable carbon isotope values predominantly reflect oxygenic photosynthesis from surface waters. [ABSTRACT FROM AUTHOR]

A Type I reaction center (RC) (Fe-S type, ferredoxin reducing) is found in several phyla containing anoxygenic phototrophic bacteria. These include the heliobacteria (HB), the green sulfur bacteria (GSB), and the chloracidobacteria (CB), for which high-resolution homodimeric RC-photosystem (PS) structures have recently appeared. The 2.2-Å X-ray structure of the RC-PS of Heliomicrobium modesticaldum revealed that the core PshA apoprotein (PshA-1 and PshA-2 homodimeric pair) exhibits a structurally conserved PSI arrangement comprising five C-terminal transmembrane α-helices (TMHs) forming the RC domain and six N-terminal TMHs coordinating the light-harvesting (LH) pigments. The Hmi. modesticaldum structure lacked quinone molecules, indicating that electrons were transferred directly from the A0 (81-OH-chlorophyll (Chl) a) acceptor to the FX [4Fe-4S] component, serving as the terminal RC acceptor. A pair of additional TMHs designated as Psh X were also found that function as a low-energy antenna. The 2.5-Å resolution cryo-electron microscopy (cryo-EM) structure for the RC-PS of the green sulfur bacterium Chlorobaculum tepidum included a pair of Fenna–Matthews–Olson protein (FMO) antennae, which transfer excitations from the chlorosomes to the RC-PS (PscA-1 and PscA-2) core. A pair of cytochromes cZ (PscC) molecules was also revealed, acting as electron donors to the RC bacteriochlorophyll (BChl) a' special pair, as well as PscB, housing the [4Fe-4S] cluster FA and FB, and the associated PscD protein. While the FMO components were missing from the 2.6-Å cryo-EM structure of the Zn- (BChl) a' special pair containing RC-PS of Chloracidobacterium thermophilum, a unique architecture was revealed that besides the (PscA)2 core, consisted of seven additional subunits including PscZ in place of PscD, the PscX and PscY cytochrome c serial electron donors and four low mol. wt. subunits of unknown function. Overall, these diverse structures have revealed that (i) the HB RC-PS is the simplest light–energy transducing complex yet isolated and represents the closest known homolog to a common homodimeric RC-PS ancestor; (ii) the symmetrically localized Ca2+-binding sites found in each of the Type I homodimeric RC-PS structures likely gave rise to the analogously positioned Mn4CaO5 cluster of the PSII RC and the TyrZ RC donor site; (iii) a close relationship between the GSB RC-PS and the PSII Chl proteins (CP)43 and CP47 was demonstrated by their strongly conserved LH-(B)Chl localizations; (iv) LH-BChls of the GSB-RC-PS are also localized in the conserved RC-associated positions of the PSII ChlZ-D1 and ChlZ-D2 sites; (v) glycosylated carotenoids of the GSB RC-PS are located in the homologous carotenoid-containing positions of PSII, reflecting an O2-tolerance mechanism capable of sustaining early stages in the evolution of oxygenic photosynthesis. In addition to the close relationships found between the homodimeric RC-PS and PSII, duplication of the gene encoding the ancestral Type I RC apoprotein, followed by genetic divergence, may well account for the appearance of the heterodimeric Type I and Type II RCs of the extant oxygenic phototrophs. Accordingly, the long-held view that PSII arose from the anoxygenic Type II RC is now found to be contrary to the new evidence provided by Type I RC-PS homodimer structures, indicating that the evolutionary origins of anoxygenic Type II RCs, along with their distinct antenna rings are likely to have been preceded by the events that gave rise to their oxygenic counterparts. [ABSTRACT FROM AUTHOR]

We theoretically investigate the possibility to use single-object spectroscopy to probe size variations of the bacteriochlorophyll aggregates inside chlorosomes. Chlorosomes are the light-harvesting organelles of green sulfur and non-sulfur bacteria. They are known to be the most efficient light-harvesting systems in nature. Key to this efficiency is the organization of bacteriochlorophyll molecules in large self-assembled aggregates that define the secondary structure inside the chlorosomes. Many studies have been reported to elucidate the morphology of these aggregates and the molecular packing inside them. It is widely believed that tubular aggregates play an important role. Because the size (radius and length) of these aggregates affects the optical and excitation energy transport properties, it is of interest to be able to probe these quantities inside chlorosomes. We show that a combination of single-chlorosome linear polarization resolved spectroscopy and single-chlorosome circular dichroism spectroscopy may be used to access the typical size of the tubular aggregates within a chlorosome and, thus, probe possible variations between individual chlorosomes that may result, for instance, from different stages in growth or different growth conditions. [ABSTRACT FROM AUTHOR]

Diversity-generating retroelements (DGRs) are used by bacteria, archaea, and viruses as a targeted mutagenesis tool. Through error-prone reverse transcription, DGRs introduce random mutations at specific genomic loci, enabling rapid evolution of these targeted genes. However, the function and benefits of DGR-diversified proteins in cellular hosts remain elusive. We find that 82% of DGRs from one of the major monophyletic lineages of DGR reverse transcriptases are encoded by multicellular bacteria, which often have two or more DGR loci in their genomes. Using the multicellular purple sulfur bacterium Thiohalocapsa sp. PB-PSB1 as an example, we characterized nine distinct DGR loci capable of generating 10282 different combinations of target proteins. With environmental metagenomes from individual Thiohalocapsa aggregates, we show that most of PB-PSB1's DGR target genes are diversified across its biogeographic range, with spatial heterogeneity in the diversity of each locus. In Thiohalocapsa PB-PSB1 and other bacteria hosting this lineage of cellular DGRs, the diversified target genes are associated with NACHT-domain anti-phage defenses and putative ternary conflict systems previously shown to be enriched in multicellular bacteria. We propose that these DGR-diversified targets act as antigen sensors that confer a form of adaptive immunity to their multicellular consortia, though this remains to be experimentally tested. These findings could have implications for understanding the evolution of multicellularity, as the NACHT-domain anti-phage systems and ternary systems share both domain homology and conceptual similarities with the innate immune and programmed cell death pathways of plants and metazoans. [ABSTRACT FROM AUTHOR]

Acidic salt lakes are environments that harbor an array of biologically challenging conditions. Through 16S rRNA, 18S rRNA, and ITS amplicon sequencing of eight such lakes across the Yilgarn Craton of Western Australia, we aim to understand the microbial ecology of these lakes with a focus on iron- and sulfur-oxidizing and reducing microorganisms that have theoretical application in biomining industries. In spite of the biological challenges to life in these lakes, the microbial communities were highly diverse. Redundancy analysis of soil samples revealed sulfur, ammonium, organic carbon, and potassium were significant diversities of the microbial community composition. The most abundant microbes with a hypothetical application in biomining include the genus 9  M32 of the Acidithiobacillus family, Alicyclobacillus and Acidiphilium, all of which are possible iron- and/or sulfur-oxidizing bacteria. It is evident through this study that these lakes harbor multiple organisms with potential in biomining industries that should be exploited and studied further. [ABSTRACT FROM AUTHOR]

Anaerobic pig wastewater treatment commonly generates high sulfide concentrations in the treated wastewater. This study aims to apply phototrophic green sulfur bacteria (PGB) to promote sulfide removal in lighting-anaerobic digestion (lighting-AD) treating pig wastewater. Initially, batch AD tests of pig wastewater with/without PGB addition were carried out under dark (D) and light (L) conditions. The results showed that the lighting-AD with PGB gave a higher growth rate of PGB (0.056 h−1) and the highest COD/sulfide removals as compared to the dark-AD with PGB and lighting-AD solely. More experiments under various light intensities were performed in order to find an optimal intensity for PGB growth concurrently with metagenomic changes concerning treatment performance. It appeared that sulfide removal rates had increased as increasing light intensity up to 473 lx by giving the highest rate of 12.5 mg L−1 d−1 with the highest sulfur element content in the biomass. Contrastingly, many PGB species disappeared at 1350 lx exposure subsequently sharply decreasing the rate of sulfide removal. In sum, the application of low light intensities of 400–500 lx with bioaugmented PGB could promote PGB growth and activity in sulfide removal in pig wastewater in the lighting of the AD process. [ABSTRACT FROM AUTHOR]

The mesophilic purple sulfur phototrophic bacterium Allochromatium (Alc.) vinosum (bacterial family Chromatiaceae) has been a favored model for studies of bacterial photosynthesis and sulfur metabolism, and its core light-harvesting (LH1) complex has been a focus of numerous studies of photosynthetic light reactions. However, despite intense efforts, no high-resolution structure and thorough biochemical analysis of the Alc. vinosum LH1 complex have been reported. Here we present cryo-EM structures of the Alc. vinosum LH1 complex associated with reaction center (RC) at 2.24 Å resolution. The overall structure of the Alc. vinosum LH1 resembles that of its moderately thermophilic relative Alc. tepidum in that it contains multiple pigment-binding α- and β-polypeptides. Unexpectedly, however, six Ca ions were identified in the Alc. vinosum LH1 bound to certain α1/β1- or α1/β3-polypeptides through a different Ca2+-binding motif from that seen in Alc. tepidum and other Chromatiaceae that contain Ca2+-bound LH1 complexes. Two water molecules were identified as additional Ca2+-coordinating ligands. Based on these results, we reexamined biochemical and spectroscopic properties of the Alc. vinosum LH1–RC. While modest but distinct effects of Ca2+ were detected in the absorption spectrum of the Alc. vinosum LH1 complex, a marked decrease in thermostability of its LH1–RC complex was observed upon removal of Ca2+. The presence of Ca2+ in the photocomplex of Alc. vinosum suggests that Ca2+-binding to LH1 complexes may be a common adaptation in species of Chromatiaceae for conferring spectral and thermal flexibility on this key component of their photosynthetic machinery. The cryo-EM structure of the partially Ca2 + -bound light-harvesting 1–reaction center (LH1–RC) complex from Alc. vinosum, the best-studied model purple sulfur bacterium, is presented, characterized and compared to other photosynthetic bacteria. [ABSTRACT FROM AUTHOR]

Tetrathionate hydrolase (TTH) is a unique enzyme found in acidophilic sulfur-oxidizing microorganisms, such as bacteria and archaea. This enzyme catalyzes the hydrolysis of tetrathionate to thiosulfate, elemental sulfur, and sulfate. It is also involved in dissimilatory sulfur oxidation metabolism, the S4-intermediate pathway. TTHs have been purified and characterized from acidophilic autotrophic sulfur-oxidizing microorganisms. All purified TTHs show an optimum pH in the acidic range, suggesting that they are localized in the periplasmic space or outer membrane. In particular, the gene encoding TTH from Acidithiobacillus ferrooxidans (Af-tth) was identified and recombinantly expressed in Escherichia coli cells. TTH activity could be recovered from the recombinant inclusion bodies by acid refolding treatment for crystallization. The mechanism of tetrathionate hydrolysis was then elucidated by X-ray crystal structure analysis. Af-tth is highly expressed in tetrathionate-grown cells but not in iron-grown cells. These unique structural properties, reaction mechanisms, gene expression, and regulatory mechanisms are discussed in this review. [ABSTRACT FROM AUTHOR]

The ecological success of purple sulfur bacteria (PSB) is linked to their ability to collect near‐infrared solar energy by membrane‐integrated, pigment–protein photocomplexes. These include a Core complex containing both light‐harvesting 1 (LH1) and reaction centre (RC) components (called the LH1–RC photocomplex) present in all PSB and a peripheral light‐harvesting complex present in most but not all PSB. In research to explain the unusual absorption properties of the thermophilic purple sulfur bacterium Thermochromatium tepidum, Ca2+ was discovered bound to LH1 polypeptides in its LH1–RC; further work showed that calcium controls both the thermostability and unusual spectrum of the Core complex. Since then, Ca2+ has been found in the LH1–RC photocomplexes of several other PSB, including mesophilic species, but not in the LH1–RC of purple non‐sulfur bacteria. Here we focus on four species of PSB—two thermophilic and two mesophilic—and describe how Ca2+ is integrated into and affects their photosynthetic machinery and why this previously overlooked divalent metal is a key nutrient for their ecological success. [ABSTRACT FROM AUTHOR]

The purple sulfur bacterium Thiocapsa roseopersicina BBS is interesting from both fundamental and practical points of view. It possesses a thermostable HydSL hydrogenase, which is involved in the reaction of reversible hydrogen activation and a unique reaction of sulfur reduction to hydrogen sulfide. It is a very promising enzyme for enzymatic hydrogenase electrodes. There are speculations that HydSL hydrogenase of purple bacteria is closely related to sulfur metabolism, but confirmation is required. For that, the full genome sequence is necessary. Here, we sequenced and assembled the complete genome of this bacterium. The analysis of the obtained whole genome, through an integrative approach that comprised estimating the Average Nucleotide Identity (ANI) and digital DNA-DNA hybridization (DDH) parameters, allowed for validation of the systematic position of T. roseopersicina as T. bogorovii BBS. For the first time, we have assembled the whole genome of this typical strain of a new bacterial species and carried out its functional description against another purple sulfur bacterium: Allochromatium vinosum DSM 180T. We refined the automatic annotation of the whole genome of the bacteria T. bogorovii BBS and localized the genomic positions of several studied genes, including those involved in sulfur metabolism and genes encoding the enzymes required for the TCA and glyoxylate cycles and other central metabolic pathways. Eleven additional genes coding proteins involved in pigment biosynthesis was found. [ABSTRACT FROM AUTHOR]

Recent advances in coupling light-harvesting microorganisms with electronic components have led to a new generation of biohybrid devices based on microbial photocatalysts. These devices are limited by the poorly conductive interface between phototrophs and synthetic materials that inhibit charge transfer. This study focuses on overcoming this bottleneck through the metabolically-driven encapsulation of photosynthetic cells with a bio-inspired conductive polymer. Cells of the purple non sulfur bacterium Rhodobacter sphaeroides were coated with a polydopamine (PDA) nanoparticle layer via the self-polymerization of dopamine under anaerobic conditions. The treated cells show preserved light absorption of the photosynthetic pigments in the presence of dopamine concentrations ranging between 0.05–3.5 mM. The thickness and nanoparticle formation of the membrane-associated PDA matrix were further shown to vary with the dopamine concentrations in this range. Compared to uncoated cells, the encapsulated cells show up to a 20-fold enhancement in transient photocurrent measurements under mediatorless conditions. The biologically synthesized PDA can thus act as a matrix for electronically coupling the light-harvesting metabolisms of cells with conductive surfaces. [ABSTRACT FROM AUTHOR]

Background: Biofilms in sulfide-rich springs present intricate microbial communities that play pivotal roles in biogeochemical cycling. We studied chemoautotrophically based biofilms that host diverse CPR bacteria and grow in sulfide-rich springs to investigate microbial controls on biogeochemical cycling. Results: Sulfide springs biofilms were investigated using bulk geochemical analysis, genome-resolved metagenomics, and scanning transmission X-ray microscopy (STXM) at room temperature and 87 K. Chemolithotrophic sulfur-oxidizing bacteria, including Thiothrix and Beggiatoa, dominate the biofilms, which also contain CPR Gracilibacteria, Absconditabacteria, Saccharibacteria, Peregrinibacteria, Berkelbacteria, Microgenomates, and Parcubacteria. STXM imaging revealed ultra-small cells near the surfaces of filamentous bacteria that may be CPR bacterial episymbionts. STXM and NEXAFS spectroscopy at carbon K and sulfur L2,3 edges show that filamentous bacteria contain protein-encapsulated spherical elemental sulfur granules, indicating that they are sulfur oxidizers, likely Thiothrix. Berkelbacteria and Moranbacteria in the same biofilm sample are predicted to have a novel electron bifurcating group 3b [NiFe]-hydrogenase, putatively a sulfhydrogenase, potentially linked to sulfur metabolism via redox cofactors. This complex could potentially contribute to symbioses, for example, with sulfur-oxidizing bacteria such as Thiothrix that is based on cryptic sulfur cycling. One Doudnabacteria genome encodes adjacent sulfur dioxygenase and rhodanese genes that may convert thiosulfate to sulfite. We find similar conserved genomic architecture associated with CPR bacteria from other sulfur-rich subsurface ecosystems. Conclusions: Our combined metagenomic, geochemical, spectromicroscopic, and structural bioinformatics analyses of biofilms growing in sulfide-rich springs revealed consortia that contain CPR bacteria and sulfur-oxidizing Proteobacteria, including Thiothrix, and bacteria from a new family within Beggiatoales. We infer roles for CPR bacteria in sulfur and hydrogen cycling. 8FE2mu4H1cxgQVBqjGxsC2 Video Abstract [ABSTRACT FROM AUTHOR]

Tarballs are formed from released or discharged crude oil containing sulfur compounds. A considerable amount and variety of sulfate-reducing bacteria (SRB) and sulfur-oxidizing bacteria (SOB) were identified in tarballs collected from the intertidal and supratidal zones of Alabama's Gulf beaches. Amplicon sequencing of the bacterial 16S rRNA gene showed that SRB were more abundantly distributed in the core than on the surface of tarballs, while no significant differences were observed in the distribution of SOB. To our best knowledge, this is the first report on the spatial distribution of diverse SRB and SOB in tarballs. [ABSTRACT FROM AUTHOR]

Viruses rely on host cells to replicate their genomes and assemble new viral particles. Thus, they have evolved intricate mechanisms to exploit host factors. Host cells, in turn, have developed strategies to inhibit viruses, resulting in a nuanced interplay of co-evolution between virus and host. This dynamic often involves competition for resources crucial for both host cell survival and virus replication. Iron and iron-containing cofactors, including iron–sulfur clusters, are known to be a heavily fought for resource during bacterial infections, where control over iron can tug the war in favor of the pathogen or the host. It is logical to assume that viruses also engage in this competition. Surprisingly, our knowledge about how viruses utilize iron (Fe) and iron–sulfur (FeS) clusters remains limited. The handful of reviews on this topic primarily emphasize the significance of iron in supporting the host immune response against viral infections. The aim of this review, however, is to organize our current understanding of how viral proteins utilize FeS clusters, to give perspectives on what questions to ask next and to propose important avenues for future investigations. [ABSTRACT FROM AUTHOR]

The objective of this work is to review the main hydrogeological characteristics and to understand the hydrochemical dynamics of the denitrification process in the gravel aquifer located in the low plain of the Seybouse watershed. The methodology implemented consisted in the identification of physico-chemical indicators characterizing the denitrification phenomenon: groundwater contents in NO , SO , FeO2, and hydrogeological conditions represented by the captivity of the aquifer and the reducing environment, associated with the presence of a support rich in sulfur and denitrifying bacteria. The chemical monitoring carried out on the fourteen drillings along a South-North profile, in the direction of the underground flow, separates globally two different zones, which are positioned from the upstream to the downstream of the gravel aquifer. The first one corresponds to the oxidizing environment, located mainly in the southern part or the deep aquifer and in direct contact with the surface aquifer. [ABSTRACT FROM AUTHOR]