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Cereibacter sphaeroides strains S3W10 and SS15, isolated from shrimp ponds, exhibit potential probiotic benefits for aquaculture. In this study, the genomic features of S3W10 and SS15 were thoroughly characterized to evaluate their probiotic properties and safety for aquaculture use. The genomes of S3W10 and SS15 consist of 130 and 74 contigs, with sizes of 4.6 Mb and 4.4 Mb and GC contents of 69.2%. Average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and phylogenomic analyses confirmed that these strains belong to C. sphaeroides. Genome annotation predicted 4260 coding sequences (CDS) in S3W10 and 4086 CDS in SS15, including genes associated with stress tolerance, nutrient absorption, and antioxidant activity. Notably, genes related to vitamin B12 synthesis, digestive enzyme production, and carotenoid biosynthesis, which support shrimp health, were identified in both genomes. CAZyme analysis identified 116 and 115 carbohydrate-active enzymes in S3W10 and SS15, respectively, supporting adaptation to gastrointestinal environments and the host immune response. Pan-genome analysis across C. sphaeroides strains revealed 7918 gene clusters, highlighting the open pan-genome structure of this species and its high genetic diversity. Further bioinformatic analyses assessing mobile genetic elements, antibiotic-resistance genes, and virulence factors demonstrated the safety of both strains for aquaculture, as no plasmids or virulence genes were identified. The genomic insights in this study provide a deeper understanding of the strains' adaptability and functional potential, aligning with previous in vitro and in vivo studies and highlighting their potential for use in shrimp cultivation. [ABSTRACT FROM AUTHOR]

Rhodothalassium (Rts.) salexigens is a halophilic purple nonsulfur bacterium and the sole species in the genus Rhodothalassium, which is itself the sole genus in the family Rhodothalassiaceae and sole family in the order Rhodothalassiales (class Alphaproteobacteria). The genome of this phylogenetically unique phototroph comprises 3.35 Mb and is highly chimeric, with nearly half of its genes originating from families other than the Rhodothalassiaceae, many of which lack phototrophic species. Photosynthesis genes in Rts. salexigens are not arranged in a typical photosynthesis gene cluster but are scattered across the genome, suggesting an origin from horizontal transfers. Despite an encoded RuBisCO, autotrophy has not been observed in Rts. salexigens, and enzymes that oxidize common inorganic electron donors are not encoded. Phospholipid biosynthesis in Rts. salexigens is restricted, and phosphoglycerolipids are the only phospholipids present in its intracytoplasmic membranes. Rts. salexigens fixes nitrogen using a Mo-containing nitrogenase and uses ammonia despite previous results that indicated it was a glutamate auxotroph. Glycine betaine is the sole osmolyte in Rts. salexigens, and enzymes are encoded that facilitate both its uptake and its biosynthesis from glycine. The genomic data also support chemotactic swimming motility, growth over a range of salinities, and the production of membrane-strengthening hopanoids. [ABSTRACT FROM AUTHOR]

Soluble phosphorus (P) and P uptake are heavily affected by adverse conditions, such as salinity and acidity. The study aimed to evaluate the effects of P-solubilizing purple nonsulfur bacteria (PSPNSB) Cereibacter sphaeroides on soil characteristics, P uptake, growth, and yield of rice planted in saline soil in Thoi Binh – Ca Mau under greenhouse conditions. The pot experiment was completely randomized in blocks with two factors. Factor A was the rate of phosphorus chemical fertilization at 0, 25, 50, 75, and 100% P according to the recommendation. Factor B was the PSPNSB including a single strain of C. sphaeroides ST16 or C. sphaeroides ST26 and a mixture of them. The soluble P in soil increased by 16.4–18.2% when C. sphaeroides ST16 and ST26 were supplied singly or in the mixture, leading to the increase in total P uptake in rice by 19.2–30.1% in two continuous crops. Moreover, the growth and yield components of rice were also improved, leading to an increase in rice grain yield by 7.20–17.7%. Moreover, supplying the C. sphaeroides strains reduced Na+ in soil and Na content in stem, leaves, and grains, leading to the reduction in proline content in rice. Supplying the C. sphaeroides ST16 and ST26 or their mixture replaced 100% P fertilizer but still ensured the rice grain yield. Further approaches should be made to investigate the possibility of the potent strains replacing chemical P fertilizers under field conditions.

Phosphorus (P) is one of the essential macronutrients for crops. It is present in soil in two forms: soluble and insoluble. However, plants cannot absorb the insoluble forms, including Al-P, Fe-P, and Ca-P; thus, the phosphorus use efficiency is reduced. Therefore, the biological approaches should focus more on sustainable agriculture to overcome this constraint. This article cites publications relating to the biological P solubilizer group of bacteria, which have a highly potential adaptation to many conditions in soils. Among the biological approaches, purple nonsulfur bacteria (PNSB) are a potent group of bacteria according to their adaptability in acidic, saline, and toxic conditions based on their mechanisms in producing exopolymeric substances and siderophores under such adverse environments like acid-sulfate and saline soils. PNSB can solubilize P in soil to have more P availability for soil microbes and plants. This particular group of bacteria has been widely applied in liquid and solid forms from agricultural waste to promote plant growth under submerged conditions. Moreover, this article summarized the P-solubilizing mechanisms of P-solubilizing bacteria and introduced future research perspectives on patterns of PNSB in aspects of nutrient-providing potency, plant growth-promoting capability, and biological control capacity. However, the specific mechanisms of P solubilization by PNSB have not been well documented since the P-solubilizing mechanisms have been investigated on general P-solubilizing bacteria. Thus, specific pathways and metabolites relating to the P-solubilizing PNSB should be investigated, and attention should be addressed to them soon.

The presence of acid sulfate soils is such an obstacle for pineapple cultivation in Vietnam due to their low pH, high toxicity and poor nutrient availability, especially phosphorus (P), which is immobilized by cations in the soils. Therefore, the study occurred to select purple nonsulfur bacteria (PNSB) strains that can solubilize P under toxic and acidic conditions. There were 33 strains that can tolerate the acidic condition, and they were selected and tested for viability and P solubilization under conditions containing Al3+, Fe2+, and Mn2+ toxins. Four strains, including W15, W39, W42 and W48 suffered from growth inhibition by Al3+, Fe2+ and Mn2+ less than the other strains under both microaerobic light and aerobic dark conditions (ML and AD conditions). In addition, there were four strains (W15, W25, W42 and W48) solubilizing Al-P well (21.4-25.2 mg L-1), two strains (W23 and W42) solubilizing Fe-P well (15.9-17.3 mg L-1), and two strains (W17 and W42) solubilizing Ca-P well (23.0-36.4 mg L-1) under both ML and AD conditions. Ultimately, there were five strains selected (W17, W23, W25, W42 and W48) and identified as Rhodopseudomonas palustris strain W17 and W23, Cereibacter sphaeroides strain W23, W42 and W48 based on the 16S rRNA technique. The selected strains also produced ALA, EPS and siderophores at 1.31-2.19 mg L-1, 0.78-1.89 mg L-1, and 16.2-55.6%, respectively. Therefore, these strains were promising in providing nutrients for pineapples in the form of biofertilizer. [ABSTRACT FROM AUTHOR]

The study was conducted to (i) isolate, select, and identify strains of purple nonsulfur bacteria (PNSB), which can fix nitrogen (N), from soil and water in a rice-shrimp integrated system, (ii) to determine the capacity of the selected potent PNSB strains in producing plant growth promoting substances. The isolation resulted in 57 pure PNSB strains from 36 soil samples and 36 water samples of rice-shrimp paddy fields in Thanh Phu - Ben Tre. Among them, 49 strains survived under pH 5.0 conditions, 24 of which grew well under microaerobic light (ML) and aerobic dark (AD) conditions in a basic isolation medium (BIM) containing NaCl 5‰. Two strains (S01 and S06) with the greatest N fixation were identified by 16S rRNA techniques as Rhodobacter sphaeroides. Their N production was 16.9 mg L-1 under the ML condition and 32.1 mg L-1 under the AD condition. Moreover, two R. sphaeroides S01 and S06 strains performed P solubilization at 0.382-2.954 mg L-1 from Al-P, 3.81-4.28 mg L-1 from Fe-P, and 3.87-4.74 mg L-1 from Ca-P, and production of plant growth promoting substances, such as IAA (12.3-15.5 mg L-1), EPS (1.09-1.58 mg L-1), siderophores (10.7-53.6%) and ALA (1.68-2.82 mg L-1) under both the incubating conditions.

The study was aimed to assess the potency of nitrogen (N)-fixing purple non-sulfur bacteria (NF-PNSB) on ameliorating soil quality, N uptake, and yield of pineapple in acid sulfate soil. The experiment, following a completely randomized block design, had two factors: (i) supplementation of biofertilizers containing the NF-PNSB (No applied bacteria, Rhodobacter sphaeroides W15, W39, and a mixture of both W15 and W39) and (ii) levels of N fertilizer [0, 50, 75, and 100% N of recommended fertilizer formula (RFF)]. Results demonstrated that supplying biofertilizers containing the mixture of both W15 and W39 increased the values of pHH2O and NH4+, and decreased the values of EC, Al3+, and Fe2+ at a soil depth of 0-20 cm, in comparison with the no supplied biofertilizers, by 15.8, 39.9, 26.9, 17.8, and 52.9%, respectively. Applying biofertilizers enhanced the total N uptake by 28.9%, resulting in greater growth and a 22.9% increase in pineapple yield, in comparison with the no biofertilizers supplied treatments. Supplying the two strains W15 and W39 not only contributed to reducing 25% N of RFF but also preserved the pineapple yield, compared to the fertilizing 100% N of RFF. Both W15 and W39 are potent for use as crop yield enhancers. [ABSTRACT FROM AUTHOR]

Increasing volumes of produced antiseptics and disinfectants, which are widely used in medicine, veterinary medicine, the food industry, and everyday life, can pose a serious environmental problem after use. Previously, when studying the action of a number of antiseptics at micromolar concentrations, the authors identified disturbances in the functioning of photosynthetic membranes and phototransforming pigment-protein complexes isolated from them in various representatives of photosynthetic organisms. In this work, to determine the sensitivity of photosynthetic membranes to the action of the cationic antiseptic octenidine, chromatophores of the purple nonsulfur bacteria Rhodobacter sphaeroides labeled with the fluorescent dye 10-N-nonyl acridine orange (NAO) were used. It was shown that the binding of NAO to chromatophores is accompanied by a shift in the maximum emission of the dye from 525 to 640 nm. The "red" fluorescence of NAO associated with chromatophores turned out to be sensitive to the effect of increasing concentrations of octenidine on photosynthetic membranes. Concentrations of the antiseptic at which it leads to degradation of chromatophore structures and a change in the aggregative state of NAO, which can be detected by enhanced "green" fluorescence in the emission spectra of the dye, were established. The properties of NAO as a fluorescent indicator of the functional state of photosynthetic membranes and potential changes that can occur in such systems under the influence of the cationic antiseptic are discussed. [ABSTRACT FROM AUTHOR]

Utilization of unsustainable fossil fuels as energy resources releases greenhouse gases into the atmosphere leading to global warming and environmental pollution. An eye-catching solution would be the production of biological liquids like hydrogen, which is a clean renewable fuel using dark/light fermentative approach. A brief insight into the effect of parameters that could enhance H 2 production is the major focus of this review. Although dark/light fermentative approaches for H 2 production is known for quite long, scaling up this technology has seen major hurdles. The review thus throws light on the need for novel tactics such as microbial immobilization, nanotechnologies, and genetic engineering to varying the microbial genomes for improvement of H 2 yield. Further, thoughts on the difficulties that could be faced and potential solutions about the prospects for H 2 technology to be commercially used as a sustainable fuel in the near future are also emphasized. [Display omitted] • Mechanisms of photo and dark fermentation for hydrogen - simplified. • Factors influencing fermentative hydrogen production. • Tactics to enhance biohydrogen production. • Possible hurdles and future prospects – large scale implementation. [ABSTRACT FROM AUTHOR]

The present study was aimed to evaluate the effects of nitrogen (N) fixing Rhodopseudomonas palustris strains, VNW64, VNS89, TLS06 and VNS02 on soil fertility, growth and yield of hybrid maize cultivated on in-dyke alluvial soil (IDAS). The pot experiment followed a completely randomized block design with 10 treatments, 4 replicates for each treatment. The treatments comprised of (i) fertilization with 100% N following recommended fertilizer formula (RFF), (ii) fertilization with 85% N, (iii) fertilization with 70% N, (iv) fertilization with 55% N, (v) treatment i plus a mixture of four purple nonsulfur bacteria (MFPNSB), (vi) treatment ii plus MFPNSB, (vii) treatment iii plus MFPNSB, (viii) treatment iv plus MFPNSB, (ix) no chemical fertilization, and (x) Treatment ix plus MFPNSB. The result indicated that treatments supplied with MFPNSB enhanced soil properties, including soil pHWater, NH4+ content and total N uptake, in comparison with no supplemented bacteria, 6.11–6.15, 16.4–17.7 mg NH4+ kg-1 and 1.43–5.02 mg N pot-1 in comparison with 5.74–5.99, 11.3–12.7 mg NH4+ kg-1 and 0.82–3.11 mg N pot-1, respectively, for hybrid maize cultivated on IDAS. Inoculation of MFPNSB on maize seeds contributed to reduce 45% N of RFF, but still caused no decline in the grain yield of maize. At 100% N of RFF, the treatment supplemented MFPNSB possessed a grain yield of 20.2% higher than the treatment without supplemented MFPNSB. Additionally, the treatment fertilized with 85% N of RFF plus MFPNSB, the maize grain yield was increased by 12.5% compared to the treatment fertilized with 100% N of RFF. [ABSTRACT FROM AUTHOR]

Denitrification is a form of anaerobic respiration wherein nitrate (NO3 -) is sequentially reduced via nitrite (NO2 -), nitric oxide, and nitrous oxide (N2O) to dinitrogen gas (N2) by four reductase enzymes. Partial denitrifying bacteria possess only one or some of these four reductases and use them as independent respiratory modules. However, it is unclear if partial denitrifiers sense and respond to denitrification intermediates outside of their reductase repertoire. Here, we tested the denitrifying capabilities of two purple nonsulfur bacteria, Rhodopseudomonas palustris CGA0092 and Rhodobacter capsulatus SB1003. Each had denitrifying capabilities that matched their genome annotation; CGA0092 reduced NO2 - to N2, and SB1003 reduced N2O to N2. For each bacterium, N2O reduction could be used both for electron balance during growth on electron-rich organic compounds in light and for energy transformation via respiration in darkness. However, N2O reduction required supplementation with a denitri fication intermediate, including those for which there was no associated denitrification enzyme. For CGA0092, NO3 - served as a stable, non-catalyzable molecule that was sufficient to activate N2O reduction. Using a β-galactosidase reporter, we found that NO3 - acted, at least in part, by stimulating N2O reductase gene expression. In SB1003, NO2 - but not NO3 - activated N2O reduction, but NO2 - was slowly removed, likely by a promiscuous enzyme activity. Our findings reveal that partial denitrifiers can still be subject to regulation by denitrification intermediates that they cannot use. [ABSTRACT FROM AUTHOR]

Saline soils negatively affect and cause serious problems for rice cultivation. This study aimed to evaluate the efficacy of the purple nonsulfur bacteria (PNSB) capable of secreting 5-aminolevulinic acid (ALA) to reduce soil salinity, improve soil fertility, and enhance rice growth and yield. A two-factorial experiment was conducted in a randomized complete block design with four replications. Factor one was the salinity of the irrigated water, and factor two was the supplementation of the ALA-producing PNSB. The results indicated that watering with saline water above 3‰ led to decreases in plant growth and rice yield compared to the treatments watered with tap water. Application of either an individual strain or the mixture of W01, W14, and W22 ameliorated soil properties and increased total NPK uptake, whereas treatments supplied with the mixed strains reduced total Na uptake (9.50 mg Na pot−1). Supplying the W01, W14, and W22 strains individually or in a mixture enhanced the plant height by 3.51–5.45% and rice grain yield by 14.7–26.2%, compared with those of the control treatment. From the study, the combination of the L. sphaeroides W01, W14, and W22 strains is promising for application in saline or salt-contaminated regions to aid the damages caused by salinity on cultivars there, especially rice. Furthermore, this is a biological approach to ease an environmental problem and improve crop performance, which is supposed to be a trend in the sustainable agriculture. [ABSTRACT FROM AUTHOR]

Abstract Background Microbially produced bioplastics are specially promising materials since they can be naturally synthesized and degraded, making its end-of-life management more amenable to the environment. A prominent example of these new materials are polyhydroxyalkanoates. These polyesters serve manly as carbon and energy storage and increase the resistance to stress. Their synthesis can also work as an electron sink for the regeneration of oxidized cofactors. In terms of biotechnological applications, the co-polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), or PHBV, has interesting biotechnological properties due to its lower stiffness and fragility compared to the homopolymer poly(3-hydroxybutyrate) (P3HB). In this work, we explored the potentiality of Rhodospirillum rubrum as a producer of this co-polymer, exploiting its metabolic versatility when grown in different aeration conditions and photoheterotrophically. Results When shaken flasks experiments were carried out with limited aeration using fructose as carbon source, PHBV production was triggered reaching 29 ± 2% CDW of polymer accumulation with a 75 ± 1%mol of 3-hydroxyvalerate (3HV) (condition C2). Propionate and acetate were secreted in this condition. The synthesis of PHBV was exclusively carried out by the PHA synthase PhaC2. Interestingly, transcription of cbbM coding RuBisCO, the key enzyme of the Calvin-Benson-Bassham cycle, was similar in aerobic and microaerobic/anaerobic cultures. The maximal PHBV yield (81% CDW with 86%mol 3HV) was achieved when cells were transferred from aerobic to anaerobic conditions and controlling the CO2 concentration by adding bicarbonate to the culture. In these conditions, the cells behaved like resting cells, since polymer accumulation prevailed over residual biomass formation. In the absence of bicarbonate, cells could not adapt to an anaerobic environment in the studied lapse. Conclusions We found that two-phase growth (aerobic-anaerobic) significantly improved the previous report of PHBV production in purple nonsulfur bacteria, maximizing the polymer accumulation at the expense of other components of the biomass. The presence of CO2 is key in this process demonstrating the involvement of the Calvin-Benson-Bassham in the adaptation to changes in oxygen availability. These results stand R. rubrum as a promising producer of high-3HV-content PHBV co-polymer from fructose, a PHBV unrelated carbon source.

Although several species of purple sulfur bacteria inhabit soda lakes, Rhodobaca bogoriensis is the first purple nonsulfur bacterium cultured from such highly alkaline environments. Rhodobaca bogoriensis strain LBB1T was isolated from Lake Bogoria, a soda lake in the African Rift Valley. The phenotype of Rhodobaca bogoriensis is unique among purple bacteria; the organism is alkaliphilic but not halophilic, produces carotenoids absent from other purple nonsulfur bacteria, and is unable to grow autotrophically or fix molecular nitrogen. Here we analyze the draft genome sequence of Rhodobaca bogoriensis to gain further insight into the biology of this extremophilic purple bacterium. The strain LBB1T genome consists of 3.91 Mbp with no plasmids. The genome sequence supports the defining characteristics of strain LBB1T, including its (1) production of a light-harvesting 1–reaction center (LH1–RC) complex but lack of a peripheral (LH2) complex, (2) ability to synthesize unusual carotenoids, (3) capacity for both phototrophic (anoxic/light) and chemotrophic (oxic/dark) energy metabolisms, (4) utilization of a wide variety of organic compounds (including acetate in the absence of a glyoxylate cycle), (5) ability to oxidize both sulfide and thiosulfate despite lacking the capacity for autotrophic growth, and (6) absence of a functional nitrogen-fixation system for diazotrophic growth. The assortment of properties in Rhodobaca bogoriensis has no precedent among phototrophic purple bacteria, and the results are discussed in relation to the organism’s soda lake habitat and evolutionary history. [ABSTRACT FROM AUTHOR]

Background: Microbially produced bioplastics are specially promising materials since they can be naturally synthesized and degraded, making its end-of-life management more amenable to the environment. A prominent example of these new materials are polyhydroxyalkanoates. These polyesters serve manly as carbon and energy storage and increase the resistance to stress. Their synthesis can also work as an electron sink for the regeneration of oxidized cofactors. In terms of biotechnological applications, the co-polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), or PHBV, has interesting biotechnological properties due to its lower stiffness and fragility compared to the homopolymer poly(3-hydroxybutyrate) (P3HB). In this work, we explored the potentiality of Rhodospirillum rubrum as a producer of this co-polymer, exploiting its metabolic versatility when grown in different aeration conditions and photoheterotrophically. Results: When shaken flasks experiments were carried out with limited aeration using fructose as carbon source, PHBV production was triggered reaching 29 ± 2% CDW of polymer accumulation with a 75 ± 1%mol of 3-hydroxyvalerate (3HV) (condition C2). Propionate and acetate were secreted in this condition. The synthesis of PHBV was exclusively carried out by the PHA synthase PhaC2. Interestingly, transcription of cbbM coding RuBisCO, the key enzyme of the Calvin-Benson-Bassham cycle, was similar in aerobic and microaerobic/anaerobic cultures. The maximal PHBV yield (81% CDW with 86%mol 3HV) was achieved when cells were transferred from aerobic to anaerobic conditions and controlling the CO2 concentration by adding bicarbonate to the culture. In these conditions, the cells behaved like resting cells, since polymer accumulation prevailed over residual biomass formation. In the absence of bicarbonate, cells could not adapt to an anaerobic environment in the studied lapse. Conclusions: We found that two-phase growth (aerobic-anaerobic) significantly improved the previous report of PHBV production in purple nonsulfur bacteria, maximizing the polymer accumulation at the expense of other components of the biomass. The presence of CO2 is key in this process demonstrating the involvement of the Calvin-Benson-Bassham in the adaptation to changes in oxygen availability. These results stand R. rubrum as a promising producer of high-3HV-content PHBV co-polymer from fructose, a PHBV unrelated carbon source. [ABSTRACT FROM AUTHOR]

Saline soils negatively affect and cause serious problems for rice cultivation. This study aimed to evaluate the efficacy of the purple nonsulfur bacteria (PNSB) capable of secreting 5-aminolevulinic acid (ALA) to reduce soil salinity, improve soil fertility, and enhance rice growth and yield. A two-factorial experiment was conducted in a randomized complete block design with four replications. Factor one was the salinity of the irrigated water, and factor two was the supplementation of the ALA-producing PNSB. The results indicated that watering with saline water above 3‰ led to decreases in plant growth and rice yield compared to the treatments watered with tap water. Application of either an individual strain or the mixture of W01, W14, and W22 ameliorated soil properties and increased total NPK uptake, whereas treatments supplied with the mixed strains reduced total Na uptake (9.50 mg Na pot−1). Supplying the W01, W14, and W22 strains individually or in a mixture enhanced the plant height by 3.51–5.45% and rice grain yield by 14.7–26.2%, compared with those of the control treatment. From the study, the combination of the L. sphaeroides W01, W14, and W22 strains is promising for application in saline or salt-contaminated regions to aid the damages caused by salinity on cultivars there, especially rice. Furthermore, this is a biological approach to ease an environmental problem and improve crop performance, which is supposed to be a trend in the sustainable agriculture.

The genus Rhodobacter consists of purple nonsulfur photosynthetic alphaproteobacteria known for their diverse metabolic capabilities. Here, we report the genome sequence and initial characterization of a novel Rhodobacter species, strain M37P, isolated from Mushroom hot spring runoff in Yellowstone National Park at 37 °C. Genome-based analyses and initial growth characteristics helped to define the differentiating characteristics of this species and identified it as an aerobic anoxygenic phototroph (AAP). This is the first AAP identified in the genus Rhodobacter. Strain M37P has a pinkish-red pigmentation that is present under aerobic dark conditions but disappears under light incubation. Whole genome-based analysis and average nucleotide identity (ANI) comparison indicate that strain M37P belongs to a specific clade of recently identified species that are genetically and physiologically unique from other representative Rhodobacter species. The genome encodes a unique xanthorhodopsin, not found in any other Rhodobacter species, which may be responsible for the pinkish-red pigmentation. These analyses indicates that strain M37P is a unique species that is well-adapted to optimized growth in the Yellowstone hot spring runoff, for which we propose the name Rhodobacter calidifons sp. nov. [ABSTRACT FROM AUTHOR]

Purple nonsulfur bacteria ( PNSB ) reportedly have probiotic effects in fish, but whether they are indigenous in the digestive tract of fish is a question that requires answering. We attempted to isolate PNSB from the digestive tract of ayu ( Plecoglossus altivelis ) from the Kuma River ( Kumamoto, Japan ) and successfully isolated 12 PNSB strains. All the isolated PNSB belonged to the genus Rhodopseudomonas . Five Rhodopseudomonas strains were also isolated from the soil samples collected along the Kuma River. The phylogenetic tree based on the partial sequence of pufLM gene indicated that the PNSB from ayu and soil were similar. The effects of NaCl concentration in growth medium on growth were also compared between the PNSB from ayu and soil. The PNSB from ayu showed a better growth performance at a higher NaCl concentration, suggesting that the intestinal tract of ayu, a euryhaline fish, might provide suitable environment for halophilic microorganisms. [ABSTRACT FROM AUTHOR]

The genus Rhodobacter consists of purple nonsulfur photosynthetic alphaproteobacteria known for their diverse metabolic capabilities. Here, we report the genome sequence and initial characterization of a novel Rhodobacter species, strain M37P, isolated from Mushroom hot spring runoff in Yellowstone National Park at 37 °C. Genome-based analyses and initial growth characteristics helped to define the differentiating characteristics of this species and identified it as an aerobic anoxygenic phototroph (AAP). This is the first AAP identified in the genus Rhodobacter. Strain M37P has a pinkish-red pigmentation that is present under aerobic dark conditions but disappears under light incubation. Whole genome-based analysis and average nucleotide identity (ANI) comparison indicate that strain M37P belongs to a specific clade of recently identified species that are genetically and physiologically unique from other representative Rhodobacter species. The genome encodes a unique xanthorhodopsin, not found in any other Rhodobacter species, which may be responsible for the pinkish-red pigmentation. These analyses indicates that strain M37P is a unique species that is well-adapted to optimized growth in the Yellowstone hot spring runoff, for which we propose the name Rhodobacter calidifons sp. nov.

Biological nitrogen fixation catalyzed by Mo-nitrogenase of symbiotic diazotrophs has attracted interest because its potential to supply plant-available nitrogen offers an alternative way of using chemical fertilizers for sustainable agriculture. Phototrophic purple nonsulfur bacteria (PNSB) diazotrophically grow under light anaerobic conditions and can be isolated from photic and microaerobic zones of rice fields. Therefore, PNSB as asymbiotic diazotrophs contribute to nitrogen fixation in rice fields. An attempt to measure nitrogen in the oxidized surface layer of paddy soil estimates that approximately 6–8 kg N/ha/year might be accumulated by phototrophic microorganisms. Species of PNSB possess one of or both alternative nitrogenases, V-nitrogenase and Fe-nitrogenase, which are found in asymbiotic diazotrophs, in addition to Mo-nitrogenase. The regulatory networks control nitrogenase activity in response to ammonium, molecular oxygen, and light irradiation. Laboratory and field studies have revealed effectiveness of PNSB inoculation to rice cultures on increases of nitrogen gain, plant growth, and/or grain yield. In this review, properties of the nitrogenase isozymes and regulation of nitrogenase activities in PNSB are described, and research challenges and potential of PNSB inoculation to rice cultures are discussed from a viewpoint of their applications as nitrogen biofertilizer.

A new taxon is created for the thermophilic purple nonsulfur bacterium previously designated as Rhodopseudomonas strain GI. Strain GI was isolated from a New Mexico (USA) hot spring microbial mat and grows optimally above 40 °C and to a maximum of 47 °C. Strain GI is a bacteriochlorophyll b-containing species of purple nonsulfur bacteria and displays a budding morphology, typical of species of the genus Blastochloris. Although resembling the species Blc. viridis in many respects, the absorption spectrum, carotenoid content, and lipid fatty acid profile of strain GI is distinct from that of Blc. viridis strain DSM133T and other recognized Blastochloris species. Strain GI forms its own subclade within the Blastochloris clade of purple nonsulfur bacteria based on comparative 16S rRNA gene sequences, and its genome is significantly larger than that of strain DSM133T; average nucleotide identity between the genomes of Blc. viridis and strain GI was below 85%. Moreover, concatenated sequence analyses of PufLM and DnaK clearly showed strain GI to be distinct from both Blc. viridis and Blc. sulfoviridis. Because of its unique assortment of properties, it is proposed to classify strain GI as a new species of the genus Blastochloris, as Blc. tepida, sp.n., with strain GIT designated as the type strain (= ATCC TSD-138 = DSM 106918). [ABSTRACT FROM AUTHOR]

The current research focuses on anaerobic respiration of arsenic and other toxic metals by purple nonsulfur bacteria (PNSB). Among the optimization assays performed were carbon utilization, cross metal resistance, and metal respiration, along with a comparison of each assay in photoheterotrophic and chemoheterotrophic growth. The bacteria were identified by the classification of 16S ribosomal RNA gene sequences. Rhodobacter sp. PI3 proved to be more versatile in carbon source utilization (acetate, lactate, citrate, and oxalate), whereas Rhodopseudomonas palustris PI5 proved to be more versatile in metal resistance (arsenate, arsenite, cobalt, lead, selenium, and nickel). Both the strains were found to be positive for photofermentative hydrogen production along with arsenic respiration. This study reveals that anaerobic conditions are more appropriate for better efficiency of PNSB. Our study demonstrates that R. palustris PI5 and Rhodobacter sp. PI3 can be promising candidates for the biohydrogen production along with metal detoxification using heavy metal‐polluted effluents as a substrate. [ABSTRACT FROM AUTHOR]

ABSTRACT In bacteria and eukaryotes alike, proper cellular physiology relies on robust subcellular organization. For the phototrophic purple nonsulfur bacteria (PNSB), this organization entails the use of a light-harvesting, membrane-bound compartment known as the intracytoplasmic membrane (ICM). Here we show that ICMs are spatially and temporally localized in diverse patterns among PNSB. We visualized ICMs in live cells of 14 PNSB species across nine genera by exploiting the natural autofluorescence of the photosynthetic pigment bacteriochlorophyll (BChl). We then quantitatively characterized ICM localization using automated computational analysis of BChl fluorescence patterns within single cells across the population. We revealed that while many PNSB elaborate ICMs along the entirety of the cell, species across as least two genera restrict ICMs to discrete, nonrandom sites near cell poles in a manner coordinated with cell growth and division. Phylogenetic and phenotypic comparisons established that ICM localization and ICM architecture are not strictly interdependent and that neither trait fully correlates with the evolutionary relatedness of the species. The natural diversity of ICM localization revealed herein has implications for both the evolution of phototrophic organisms and their light-harvesting compartments and the mechanisms underpinning spatial organization of bacterial compartments. IMPORTANCE Many bacteria organize their cellular space by constructing subcellular compartments that are arranged in specific, physiologically relevant patterns. The purple nonsulfur bacteria (PNSB) utilize a membrane-bound compartment known as the intracytoplasmic membrane (ICM) to harvest light for photosynthesis. It was previously unknown whether ICM localization within cells is systematic or irregular and if ICM localization is conserved among PNSB. Here we surveyed ICM localization in diverse PNSB and show that ICMs are spatially organized in species-specific patterns. Most strikingly, several PNSB resolutely restrict ICMs to regions near the cell poles, leaving much of the cell devoid of light-harvesting machinery. Our results demonstrate that bacteria of a common lifestyle utilize unequal portions of their intracellular space to harvest light, despite light harvesting being a process that is intuitively influenced by surface area. Our findings therefore raise fundamental questions about ICM biology and evolution.

Aims: Purple nonsulfur bacteria (PNSB), Rhodopseudomonas palustris strains (TLS06, VNW02, VNW64 and VNS89), were investigated to increase rice growth and grain yield in acid sulfate soils (ASS) with low available phosphorus (Pavail).Methods: P-solubilizers were tested in vitro. A 4 × 3 factorial design consisted of PNSB at 5.4 × 104 cells g−1 dry soil weight (mixture of 4 strains, VNW64 singly, or no-PNSB) and P fertilizer levels (0, 30, 45 and 60 kg P2O5 ha−1) that were used with the rice variety OM5451in pots with two types of ASS (Hon Dat and Phung Hiep).Results: The four PNSB mixture had the ability to dissolve insoluble P from variscite and strengite. The combination of mixed culture with 45 P was the most effective, increasing grain yield by 34%. Enhancement of rice growth and yield in both soils corresponded to the maximal levels of Pavail, total P and NH4+, and the lowest levels of Alexch and Fe2+. Soil health with this treatment was significantly improved, with a strong positive correlation between PNSB population and phosphatase activity in both soil types.Conclusions: The combination of PNSB mixture with P fertilizer reduced the amount of chemical fertilizer needed for maximal grain yield, provided safe rice, and maintained soil health. [ABSTRACT FROM AUTHOR]

This experiment aimed to decolorize Reactive Red 159 using a high potential of a consortium of purple nonsulfur bacteria (PNSB) with an application of response surface methodology through a central composite design in open system. The three factors of hydraulic retention time (HRT), sludge retention time (SRT) and dye concentration were applied to the design. The decolorization was operated in an anaerobic sequencing batch reactor until the system reached to a pseudosteady state for 30 cycles in each experiment. The optimal condition was 6,500 mg/L of Reactive Red 159 concentration with 20 days of SRT and 8 days of HRT, achieving dye effluent of 142.62 ± 5.35 mg/L, decolorization rate of 264.54 ± 7.13 mg/L/h and decolorization efficiency of 97.68 ± 0.74%. The results revealed that PNSB efficiently decolorized the high concentration of Reactive Red 159 and they were a high potential of microorganisms for dyes contaminated wastewater treatment. [ABSTRACT FROM AUTHOR]

This research aimed to evaluate the capacity of acid-resistant purple nonsulfur bacteria, Rhodopseudomonas palustris strains VNW02, TLS06, VNW64, and VNS89, to resist Al3+ and Fe2+ and to investigate their potential to remove both metals from aqueous solutions using exopolymeric substances (EPS) and biomasses. Based on median inhibition concentration (IC50), strain VNW64 was the most resistant to both metals under conditions of aerobic dark and microaerobic light; however, strain TLS06 was more resistant to Al3+ under aerobic dark conditions. High metal concentrations resulted in an altered cellular morphology, particularly for strain TLS06. Metal accumulation in all tested PNSB under both incubating conditions as individual Al3+ or Fe2+ was in the order of cell wall > cytoplasm > cell membrane. This was also found in a mixed metal set only under conditions of aerobic dark as microaerobic light was in the degree of cytoplasm > cell wall > cell membrane. Of all strains tested, EPS from strain VNW64 had the lowest carbohydrate and the highest protein contents. Metal biosorption under both incubating conditions, EPS produced by strains VNW64 and TLS06, achieved greater removal (80 mg Al3+ L−1 and/or 300 mg Fe2+ L−1) than their biomasses. Additionally, strain VNW64 had a higher removal efficiency compared to strain TLS06. Based on the alteration in cellular morphology, including biosorption and bioaccumulation mechanisms, R. palustris strains VNW64 and TLS06 demonstrated their resistance to metal toxicity. Hence, they may have great potential for ameliorating the toxicity of Al3+ and Fe2+ in acid sulfate soils for rice cultivation. [ABSTRACT FROM AUTHOR]

Single cell protein (SCP) is an alternative way to increase nutrients for animal consumption; and purple nonsulfur bacteria (PNSB) should be considered as SCP due to their rich sources of protein, vitamins and photopigments. Hence, the aim of this study was to investigate the potential of promising PNSB to be used as SCP by mixing with commercial shrimp feed for white shrimp cultivation starting from postlarval until early juvenile stages for 60 days. PNSB strains, Rhodobacter sphaeroides SS15 and Afifella marina STW181 were selected, based on high amounts of biologically complete protein and photopigments, to use as SCP at a ratio of 1:1; and their lyophilized cells at 1, 3 and 5% (w/w) were mixed well with commercial shrimp feed to obtain modified shrimp feed recipes; Diet 1, Diet 2 and Diet 3, respectively. Levels of NH 4 + , NO 2 − , NO 3 − and COD in rearing water from Diet 2 and 3 sets were significantly higher than control set. However, Diet 1 set showed the lowest levels of these water parameters among modified diet sets as no significant difference levels of NO 3 − and COD between Diet 1 and control sets. Shrimp growth performance on the basis of relative gain rate and other growth parameters found that Diet 1 set was much better than sets of Diet 2, Diet 3 and control with the lowest found in the control set. In addition, the maximum shrimp survival was observed in Diet 1 set (85%) although no significant difference among them as 80% in control set. No significant difference was found among control and all modified shrimp diets for total hemocyte count in shrimp; however, significant increases of superoxide dismutase activity found in sets of Diet 1, while phenoloxidase activity found in Diet 2 and Diet 3. The results of hepatopancreas (HP) histopathology analysis also showed a good condition of HP as healthy shrimp. PNSB biomass as SCP at optimal level has the potential to be an effective source of a novel protein in shrimp feed to enhance shrimp growth and also to increase shrimp survival as more nutritious with no effect on water quality. [ABSTRACT FROM AUTHOR]

The biodiversity of phototrophic purple nonsulfur bacteria (PNSB) in comparison with purple sulfur bacteria (PSB) in colored blooms and microbial mats that developed in coastal mudflats and pools and wastewater ditches was investigated. For this, a combination of photopigment and quinone profiling, pufM gene-targeted quantitative PCR, and pufM gene clone library analysis was used in addition to conventional microscopic and cultivation methods. Red and pink blooms in the coastal environments contained PSB as the major populations, and smaller but significant densities of PNSB, with members of Rhodovulum predominating. On the other hand, red-pink blooms and mats in the wastewater ditches exclusively yielded PNSB, with Rhodobacter, Rhodopseudomonas, and/or Pararhodospirillum as the major constituents. The important environmental factors affecting PNSB populations were organic matter and sulfide concentrations and oxidation−reduction potential (ORP). Namely, light-exposed, sulfide-deficient water bodies with high-strength organic matter and in a limited range of ORP provide favorable conditions for the massive growth of PNSB over co-existing PSB. We also report high-quality genome sequences of Rhodovulum sp. strain MB263, previously isolated from a pink mudflat, and Rhodovulum sulfidophilum DSM 1374T, which would enhance our understanding of how PNSB respond to various environmental factors in the natural ecosystem.

Occurrences of harmful cyanobacterial blooms are a worldwide environmental problem in most eutrophic lake ecosystems. But what should be noticed is that cyanobacteria can be used as a useful resource due to the wide range of metabolites they produce. Nutrient partitioning using purple nonsulfur bacteria (PNSB) has the potential to biologically concentrate nutrients. The present study evaluated the kinetics of nutrients released from decomposed field blue green algae (BGA) biomasses. The potential of nutrient acquisition from decomposed BGA biomasses for culturing Rhodopseudomonas palustris (R. palustris) was investigated via fed-batch experiments. Results indicated that R. palustris stimulated in algae substrates with algae biomasses ranging from 3.33 to 10 g/L. Removal efficiencies of N and P in the stationary phase of growth were at least 40% and 95%, respectively, of all the nitrogen (N) and phosphorus (P) released. Additionally, the cellular contents like total lipid and poly-β-hydroxybutyrate (PHB), as well as the fatty acids produced by R. palustris, were consistent. Hence, practice based on the bacterial production for the nutrient recovery from BGA biomasses provides a new insight in field algae disposal. It will lower the chances of secondary pollution due to algae decay and produce giant cells of R. palustris and surely will prosper the industries applying R. palustris. [ABSTRACT FROM AUTHOR]

To overcome efficiency losses due to overheating in outdoor photobioreactors for microbial hydrogen production, heat-resistant microorganisms are desirable. In this study, the comparative whole genome sequencing analyses of two previously obtained Rhodobacter capsulatus heat-resistant mutants; A52 and B41, with modified hydrogen production capacities, have been performed to identify mutations related to hydrogen production. In comparison with the reference strain DSM1710, the genomes of the mutants A52 and B41 contained 2137 and 2253 mutations, respectively. In the mutant B41 genome, mutations were characterized within the nifD , nifJ , glnD , nifB1 , ccpA, hupD , dmsA, and cbbR1 genes. On the other hand; in the A52 mutant, mutations were characterized in the nifB2 , rnfF, nifJ, cbbO, anfH, amt, moeA, and hupD genes. The effects of nitrogen metabolism and redox-related mutations were tested by quantitative reverse transcription PCR. The most promising mutation was found on the glnD gene of B41 strain with higher hydrogen production capacity. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the potential of a mixed probiotic purple nonsulfur bacteria (PNSB) for controlling water quality and preventing acute hepatopancreatic necrosis disease (AHPND) to promote growth performance and increase survival of white shrimp ( Litopenaeus vannamei ) in postlarval stage during cultivation. Four probiotic PNSB ( Rhodobacter sphaeroides strains SS15, S3W10, TKW17 and Afifella marina STW181) were investigated for controlling water quality using a mixed culture at a ratio of 1: 1 (roughly 1 × 10 8 cells mL − 1 for each, every week 1–7) as follows; T1 (S3W10 + SS15), T2 (S3W10 + TKW17) and T3 (S3W10 + STW181) and found that throughout 8 weeks shrimp cultivation the most effective sets to reduce NH 4 + and promote shrimp growth (based on weight and total length) were T1 and T3, respectively. Hence, PNSB strains (SS15, S3W10 and STW181) were used as a mixed culture (1: 1: 1, roughly 1 × 10 8 cells mL − 1 for each at weeks 1, 2 and 3) assessing their potential to prevent AHPND by challenge test on shrimp with a virulent strain AHPND-causing Vibrio parahaemolyticus SR2 (roughly 1 × 10 5 cells mL − 1 at day 15) during shrimp cultivation for 30 days. Inoculated PNSB sets (positive control: only PNSB inoculation, and treatment: both PNSB and SR2 inoculations) significantly decreased ( P < 0.05) the levels of NH 4 + , NO 2 − , NO 3 − and chemical oxygen demand (COD) with significantly higher ( P < 0.05) of dissolved oxygen (DO) compared to native control (no inoculation) and challenge test (only SR2 inoculation). The maximal growth performance of shrimp was observed in the positive control; while no significant difference ( P > 0.05) was observed for other sets. PNSB survived and colonized in intestinal shrimp tract to prevent AHPND by increasing 11% survival rate of infected shrimp by strain SR2. The correlation coefficient between PNSB population and shrimp survival showed a positive strong correlation, but a negative strong correlation between vibrios population and shrimp survival. Overall results proved that a mixed three probiotic PNSB are a good candidate for applying in white shrimp cultivation to maintain water quality and to protect shrimp diseases for promoting shrimp growth with higher survival rate. [ABSTRACT FROM AUTHOR]

This study aimed to identify arsenic resistant mechanisms in As-resistant purple nonsulfur bacteria (PNSB) by screening them for presence of As-resistance genes and related enzymes. Resistance to As(III) and As(V) of four As-resistant PNSB determined in terms of median inhibition concentration (IC50 values) were in the order of strains Rhodopseudomonas palustris C1 > R. palustris AB3 > Rubrivivax benzoatilyticus C31 > R. palustris L28 which corresponded to the presence of As-resistance genes in these bacteria. The strain C1 showed all As-marker genes; arsC, arsM, aioA, and acr3, while aioA was not detected in strain AB3. Strains C31 and L28 had only Arsenite-transporter gene, acr3. Translation of all these detected gene sequences of strain C1 to amino acid sequences showed that these proteins have vicinal cysteine; Cys126, Cys105, and Cys178 of Acr3, ArsC, AioA, respectively. Tertiary structure of proteins Acr3, ArsC, AioA, and ArsM showed strain C1 exhibits the high activities of arsenite oxidase and arsenate reductase enzymes that are encoded by aioA and arsC genes, respectively. Moreover, strain C1 with arsM gene produced volatile-methylated As-compounds; monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and arsenobetaine (AsB) in the presence of either As(III) or As(V). In conclusion, the strain C1 has great potential for its application in bioremediation of As-contaminated sites. [ABSTRACT FROM AUTHOR]

The objectives of this study were to investigate arsenic (As) contamination in areas surrounding mines in Thailand and to isolate As-resistant purple nonsulfur bacteria (PNSB) for their potential application in microbial As bioremediation. Total As in water and soil samples collected from two As-contaminated sites in Thailand exceeded the standard guidelines. Four strains of As-resistant PNSB were selected from 348 isolates based on their As detoxification mechanisms, including biofilm formation, As redox transformations, glutathione (GSH) production, and production of methylcobalamin (vitamin B12) and S-adenosylmethionine (SAM) for As biomethylation. GSH production in these strains followed the order AB3 > L28 > C1. Strains AB3, C31, and L28 accumulated higher levels of intracellular vitamin B12 than strain C1. However, only strain C1 produced SAM and showed As biovolatilization activity. When strain C1 was incubated under microaerobic light conditions, it produced arsenobetaine [(AsB(V)] in medium with As(III) and monomethylarsonic acid [MMA(V)] in medium with As(V), which were found in the culture supernatants. Volatile methylated As compounds, such as dimethylarsenic acid [DMA(V)] and MMA(V)], were also detected in strain C1 during 30 days of incubation with As(III) and As(V). Strains AB3, C1, and L28 were identified as Rhodopseudomonas palustris and strain C31 as Rubrivivax benzoatilyticus. The resistance of these strains to As [As(III) and As(V)] based on minimum inhibition concentration values under aerobic dark and microaerobic light conditions, respectively, was in the order of C1 > AB3 > C31 > L28. The overall results demonstrate that all four selected strains of PNSB have a great potential for future application in the remediation of As-contaminated areas although R. palustris C1 was the most effective candidate. [ABSTRACT FROM AUTHOR]

The community of anoxygenic phototrophic bacteria (APB) in the water column of Lake Kislo- Sladkoe (Kandalaksha Bay, White Sea), which has recently become separated from the sea, was investigated in March?April 2012, March?April 2013, and in September 2013. The lake, which was previously considered meromictic, was in fact mixed and was strongly affected by the sea. In winter the lake is sometimes washed off with seawater, and this together with the seasonal cycles of succession processes determines the succession of the community. The consequences of the mixing in autumn 2011 could be observed in the APB community as late as autumn 2013. Green-colored green sulfur bacteria (GSB) usually predominated in the chemocline. In winter 2013 stagnation resulted in turbidity of water under the ice, which was responsible for both predominance of the brown GSB forms and the changes ratio of the species of purple sulfur bacteria (PSB) in anoxic water layers. Production of anoxygenic photosynthesis in the lake was at least 240 mg C m day in September and 0-20 mg C m day in March-April, which corresponded to 40 and 69%, respectively, of oxygenic photosynthesis. Okenone-containing purple sulfur bacteria, strain TcakPS12, were isolated in 2012 from lake water. The ells of this strain form filaments of not separated cells. Strain TcakPS12 exhibited 98% similarity with the type strains of Thiocapsa pendens DSM 236 and Thiocapsa bogorovii BBS, as well as with the strains AmPS10 and TcyrPS10, which were isolated from Lake Kislo-Sladkoe in 2010. [ABSTRACT FROM AUTHOR]

A purple nonsulfur anoxygenic phototrophic bacterium, identified as Rhodomicrobium vannielii, was isolated from water sample of a hot spring using glutamate-malate medium (GMM) and Pfennig’s M2 medium. The cells were motile, Gram negative, ovoid to spherical in shape and did not form intracellular sulfur globules. The isolate viewed under transmission electron microscope showed budding filament formation, which is a characteristic of Rm. vannielii. The isolate produced red pigment in both media. The dominant photosynthetic pigment is bacteriochlorophyll a and carotenoids of lycopene and rhodopin. The growth of Rm. vannielii was better in anaerobic-light condition compared to growth in aerobic-dark. Optimum carotenoid production was achieved in 24 hours culture in GMM (pH 7.0) without yeast-extract and incubated in anaerobic-light condition at light intensity of 2000 lux.

The aims of this study were to investigate the presence of mercury (Hg) contamination in shrimp ponds in the south of Thailand and to isolate Hg-resistant purple nonsulfur bacteria (PNSB). Contamination by total mercury (Hg) in water and sediment samples ranged from <0.0002 to 0.037 μg/L and from 30.73 to 398.84 μg/kg dry weight. In all water and sediment samples, the concentration of Hg was less than the Thai, Hong Kong, and Canadian standard guidelines. Of the Hg-resistant PNSB, six strains detoxified Hg by volatilization to Hg using their mercuric reductase enzyme. The ability of PNSB to resist Hg in aerobic dark conditions was better than in microaerobic light, and this corresponded with their Hg reductase activities (dark condition 15.75, 12.62, and 12.16 U/mg protein for strains SSW15-1, SRW1-5, and SSS2-1, respectively). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were the same under both incubating conditions at 2.40 mg/L for SRW1-5 and 1.60 mg/L for SSW15-1. However, both values under light condition of SSS2-1 were 3.20 mg/L while under dark-condition MIC and MBC values were 3.20 and 4.00 mg/L. The half maximal inhibitory concentration (IC) values of Hg on strains SSS2-1, SRW1-5, and SSW15-1 under dark and light conditions were 2.16, 1.23, and 0.90; and 1.66, 1.11, and 0.80 mg/L, respectively. They were identified using 16S ribosomal RNA (rRNA) genes establishing that SSS2-1 and SSW15-1 were Afifella marina, while SRW1-5 was Rhodovulum sulfidophilum. These strains can potentially be used to treat Hg-contaminated shrimp ponds. [ABSTRACT FROM AUTHOR]

Saline soil is one major problem that causes low productivity on rice, while paddy fields are also one source of methane (CH 4 ) emissions that can have a considerable impact on global warming. By using purple nonsulfur bacteria (PNSB) it is possible to overcome both these serious problems because PNSB produce 5-aminolevulinic acid (ALA), a compound that reduces salt stress for plants, and they are also good competitors for methanogens in the paddy fields. Therefore, the objective of this study was to select salt resistant PNSB with an ability to release ALA and reduce CH 4 emissions. The PNSB isolates used were obtained from saline paddy fields in southern Thailand and the best were selected on the basis of their good growth under conditions of aerobic dark and anaerobic light while being salt tolerant, released ALA and reduced CH 4 emissions under microaerobic light conditions. Among the 272 PNSB isolates, TN114 was the best ALA producer while PP803 was the best to reduce CH 4 emissions. Both selected PNSB strains grew well in glutamate acetate (GA) broth containing NaCl up to 6.00% but 0.25% NaCl was their optimal concentration for growth. Under salt stress with 0.25% NaCl, the strain TN114 released 25.63 μM ALA in GA broth. In scaled-up experiments, when it was mixed with native soil flora in rice straw broth the strain TN114 released 13.44 μM ALA and the strain PP803 reduced CH 4 emissions by 88.41%. These two strains were identified as Rhodopseudomonas palustris according to both traditional and 16 S rRNA identifications. Overall the results demonstrated that they had a good potential as plant growth stimulating bacteria under salt stress, due to the release of ALA and also reduce CH 4 emissions. [ABSTRACT FROM AUTHOR]

Latex rubber sheet wastewater (non sterile wastewater: RAW) was treated efficiently using a stimulated Rhodopseudomonas palustris P1 inoculum with added fermented pineapple extract (FPE) under microaerobic light conditions. Optimization of wastewater treatment conditions using a central composite design (CCD) found that a 3 % stimulated P1 inoculum with 0.9 % added FPE and a 4-day retention time (RT) were the most suitable conditions. Calculations from CCD experiments predicted that a chemical oxygen demand (COD) of 3,005 mg/L could be 98 % removed, together with 79 % of suspended solids (SS) and 72 % of total sulfide (TtS). No HS was detected, production costs were low and single cell protein (SCP) was a by-product. The results of the verification test had an error of only 4-8 % and confirmed removal of COD (initial COD 2,742 mg/L), SS and TtS at 94 %, 75 % and 66 %, respectively. These values were less than the best set obtained from the CCD experiment (2 % stimulated P1 inoculum, 0.75 % FPE and 4 days RT); upon repeating, this set could reduce 96 % of the COD, 78 % SS and 71 % TtS. The treated wastewater met the standard guidelines for irrigation use and no HS was detected. The biomass obtaining after wastewater treatment from the best set consisted mostly of R. palustris P1; the biomass of this set had 65 % protein, 3 % fat, 8 % carbohydrate, 14 % ash and 10 % moisture. The results demonstrated that an inoculum of stimulated P1 grew well in RAW supplemented with FPE and could be considered to be an appropriate technology for effectively treating wastewater, with SCP as a by-product. [ABSTRACT FROM AUTHOR]