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In temperate regions, an organism's ability to rapidly adapt to seasonally varying environments is essential for its survival. In response to seasonal changes in selection pressure caused by variation in temperature, humidity, and food availability, some organisms exhibit plastic changes in phenotype. In other cases, seasonal variation in selection pressure can rapidly increase the frequency of genotypes that offer survival or reproductive advantages under the current conditions. Little is known about the relative influences of plastic and genetic changes in short‐lived organisms experiencing seasonal environmental fluctuations. Cold hardening is a seasonally relevant plastic response in which exposure to cool, but nonlethal, temperatures significantly increases the organism's ability to later survive at freezing temperatures. In the present study, we demonstrate seasonal variation in cold hardening in Drosophila melanogaster and test the extent to which plasticity and adaptive tracking underlie that seasonal variation. We measured the post‐cold hardening freeze tolerance of flies from outdoor mesocosms over the summer, fall, and winter. We bred outdoor mesocosm‐caught flies for two generations in the laboratory and matched each outdoor cohort to an indoor control cohort of similar genetic background. We cold hardened all flies under controlled laboratory conditions and then measured their post‐cold hardening freeze tolerance. Comparing indoor and field‐caught flies and their laboratory‐reared G1 and G2 progeny allowed us to determine the roles of seasonal environmental plasticity, parental effects, and genetic changes on cold hardening. We also tested the relationship between cold hardening and other factors, including age, developmental density, food substrate, presence of antimicrobials, and supplementation with live yeast. We found strong plastic responses to a variety of field‐ and laboratory‐based environmental effects, but no evidence of seasonally varying parental or genetic effects on cold hardening. We therefore conclude that seasonal variation in post‐cold hardening freeze tolerance results from environmental influences and not genetic changes. [ABSTRACT FROM AUTHOR]

Plankton diversity acts as an ecological indicator of aquatic ecosystems due to their rapid response to environmental changes. Plankton samples were collected monthly for a period of 24 months. A total of 35 genera of phytoplankton belonging to three classes, Bacillariophyceae (21 genera), Chlorophyceae (9 genera) and Cyanophyceae (5 genera) were found. The abundance of phytoplankton was in the order, Bacillariophyceae (83%) followed by Chlorophyceae (9%) and Cyanophyceae (8%). Maximum phytoplankton density in winter season was attributed to the low water temperature, gentle water velocity, high transparency, availability of sufficient nutrients and most stable substratum. Eight genera of zooplankton belonging to three major groups, Protozoa (2 genera), Rotifera (5 genera) and Copepoda (1 genus) was recorded. Shannon-Wiener diversity index of phytoplankton and zooplankton was computed maximum to be 2.61 and 1.56 respectively in the winter season. PCA indicates Cymbella, Navicula, Synedra, Cocconeis, Achnanthidium, Amphora, Nitzschia, Tabellaria, Fragilaria, Ulothrix, Spirogyra and Phormidium to be most dominant genera in the Mandakini river. Total alkalinity, water temperature, transparency, velocity, dissolved oxygen, free carbon dioxide, turbidity, phosphate and nitrate were found to be the most important factors affecting plankton diversity in the Mandakini river. [ABSTRACT FROM AUTHOR]

Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is the number 1 pathogen of the important economic crop soybean. Bacteria represent potential biocontrol agents of the SCN, but few studies have characterized the dynamics of bacterial communities associated with cysts under different crop rotation sequences. The bacterial communities in SCN cysts in a long-term soybean–corn crop rotation experiment were investigated over 2 years. The crop sequences included long-term soybean monoculture (Ss), years 1–5 of soybean following 5 years corn (S1–S5), years 1 and 2 of corn following 5 years soybean (C1 and C2), and soybean–corn annual rotation (Sa and Ca). The bacterial 16S rRNA V4 region was amplified from DNA isolated from SCN cysts collected in spring at planting, midseason (2 months later), and fall at harvest and sequenced on the Illumina MiSeq platform. The SCN cyst microbiome was dominated by Proteobacteria followed by Actinobacteria, Bacteroidetes, and Verrucomicrobia. The bacterial community composition was influenced by both crop sequence and season. Although differences by crop sequence were not significant in the spring of each year, bacterial communities in cysts from annual rotation (Sa and Ca) or crop sequences of early years of monoculture following a 5-year rotation of the alternate crop (S1 and C1) became rapidly differentiated by crop over a single growing season. In the fall, genera of cyst bacteria associated with soybean crop sequences included Rhizobacter , Leptothrix , Cytophaga , Chitinophaga , Niastella , Streptomyces , and Halangium. The discovery of diverse bacterial taxa in SCN cysts and their dynamics across crop rotation sequences provides invaluable information for future development of biological control of the SCN. [ABSTRACT FROM AUTHOR]

Knowledge in aquatic virology has been greatly improved by cultureindependent methods, yet there is still a critical need for isolating novel phages to identify the large proportion of "unknowns" that dominate metagenomes and for detailed analyses of phage-host interactions. Here, 54 phages infecting Rheinheimera sp. strain BAL341 (Gammaproteobacteria) were isolated from Baltic Sea seawater and characterized through genome content analysis and comparative genomics. The phages showed a myovirus-like morphology and belonged to a novel genus, for which we propose the name Barbavirus. All phages had similar genome sizes and numbers of genes (80 to 84 kb; 134 to 145 genes), and based on average nucleotide identity and genome BLAST distance phylogeny, the phages were divided into five species. The phages possessed several genes involved in metabolic processes and host signaling, such as genes encoding ribonucleotide reductase and thymidylate synthase, phoH, and mazG. One species had additional metabolic genes involved in pyridine nucleotide salvage, possibly providing a fitness advantage by further increasing the phages' replication efficiency. Recruitment of viral metagenomic reads (25 Baltic Sea viral metagenomes from 2012 to 2015) to the phage genomes showed pronounced seasonal variations, with increased relative abundances of barba phages in August and September synchronized with peaks in host abundances, as shown by 16S rRNA gene amplicon sequencing. Overall, this study provides detailed information regarding genetic diversity, phage-host interactions, and temporal dynamics of an ecologically important aquatic phage-host system. [ABSTRACT FROM AUTHOR]

In the present study, 13 endocrine disrupting compounds (EDCs) and their transformation products (TPs) were monitored in Jiulong River and its estuary, China in different seasons. The analytes included antimicrobials [triclosan (TCS) and triclocarbon (TCC)]; estrogens [estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2)]; alkylphenol ethoxylates [4-n-nonylphenol (NP) and 4-n-octylphenol (OP)] and the TPs [methyl triclosan (MeTCS), carbanilide (NCC), dichlorocarbanilide, 4-hydroxy estrone (4-OH E1) and 4-hydroxy estradiol (4-OH E2)]. A significant seasonal variation was observed for most EDCs. Approximately, 79% of the total E2 residues were detected in the normal season in comparison with the wet season to indicate recalcitrant behavior of E2 during the normal season. Risk assessment revealed that E2 was most potent among the EDCs to cause highest risk to both vertebrate and invertebrate aquatic species, whereas, E1, EE2, MeTCS and TCS also showed relatively high risk for some surface water aquatic species. Unlabelled Image • 13 endocrine disrupting compounds were investigated in Jiulong river & estuary. • The occurrence and detection frequency of the antimicrobials was highest. • Significant seasonal variation was observed for most of the compounds. • Estradiol (E2) was most potent among these compounds to cause highest risk. [ABSTRACT FROM AUTHOR]

The community of anoxygenic phototrophic bacteria (APB) from the water column of the meromictic Lake Trekhtsvetnoe (Kandalaksha Bay, White Sea, Russia) was studied in March 2012 and 2013 and in September 2013 and 2014. The community structure below the chemocline was shown to restore during three years after partial mixing resulting from seawater admixture into the lake in autumn 2011; a dense layer (at least 108 cells mL–1) of green-colored (g/c) sulfur bacteria (GSB) was formed. During winter, development of low numbers of brown colored (b/c) GSB was observed in the upper layer of green water. During summer seasons, b/c GSB were found to be located in the oxic zone above the green water layer, which was unusual for these organisms. The APB community was found to contain purple bacteria. Four APB strains were isolated from the upper part of the sulfide zone. The b/c and g/c GSB strains were phylogenetically close to each other and to the type species Chlorobium phaeovibrioides DSM 265 (99% similarity gene sequences). One strain of purple bacteria was phylogenetically related to the brackish sulfur bacteria Thiocapsa marina, while the other was related to freshwater bacteria Rhodopseudomonas palustris. The strains of sulfur bacteria were phylogenetically close to the chemocline bacteria from the stratified Lake Kislo-Sladkoe, also located in the coastal zone of the Kandalaksha Bay, White Sea. [ABSTRACT FROM AUTHOR]

ABSTRACT: Chiggers were collected from the central and southern parts of South Korea between April and November, 2009 with the aim of investigating the seasonal and geographical distribution of Or. A total of 1136 chiggers were identified. They included eight species belonging to four genera, as follows: Leptotrombidium scutellare (27.2%, n = 309), L. pallidum (54.6%, n = 621), L. orientale (6.25%, n = 71), L. palpale (1.59%, n = 18), L. zetum (2.0%, n = 23), Euschoengastia koreaensis (1.5%, n = 17), Cheladonta ikaoensis (0.08%, n = 1) and Neotrombicula japonica (1.05%, n = 12). The density of L. pallidum was high from April to May, whereas L. scutallare was not found in spring, being observed from October. Serotype‐specific nested PCR targeting the 56 kDa protein gene and sequencing analysis identified that the strains of 1136 O. tsutsugamushi in the chiggers as Boryong (6.8%), Kanda (0.4%), Oishi (0.3%), Jecheon (0.1%), Youngworl (0.1%) and Wonju (0.1%). Our findings indicate that L. pallidum and L. scutellare are dominant species in Korea and have geographical and seasonal variations. [ABSTRACT FROM AUTHOR]

Coastal lagoons are highly productive ecosystems, which are experiencing a variety of human disturbances at increasing frequency. Bacteria are key ecological players within lagoons, yet little is known about the magnitude, patterns and drivers of diversity in these transitional environments. We carried out a seasonal study in the Venice Lagoon (Italy) and the adjacent sea, to simultaneously explore diversity patterns in different domains (pelagic, benthic) and their spatio-temporal variability, and test the role of environmental gradients in structuring assemblages. Community composition differed between lagoon and open sea, and between domains. The dominant phyla varied temporally, with varying trends for the two domains, suggesting different environmental constraints on the assemblages. The percentage of freshwater taxa within the lagoon increased during higher river run-off, pointing at the lagoon as a dynamic mosaic of microbial taxa that generate the metacommunity across the whole hydrological continuum. Seasonality was more important than spatial variability in shaping assemblages. Network analyses indicated more interactions between several genera and environmental variables in the open sea than the lagoon. Our study provides evidences for a temporally dynamic nature of bacterial assemblages in lagoons and suggests that an interplay of seasonally influenced environmental drivers shape assemblages in these vulnerable ecosystems. [ABSTRACT FROM AUTHOR]

As a newly emerging persistent environmental contaminant, perchlorate (ClO ) has adverse effects on thyroid function by inhibiting iodide uptake and could result in neurodevelopment deficits. Our study was performed to investigate the concentration of perchlorate in size-segregated airborne particulate matter (APM) and evaluate its human exposure for children and adults. In this study, 45 size-segregated APM samples were collected from Changsha, China, during July 20 to July 31, 2016. The total APM concentrations ranged from 93.367 to 253.271 μg/m (mean 154.651 ± 59.175 μg/m), and a bimodal size distribution was observed during the sampling period. The concentrations of perchlorate in size-segregated APM were in the range of 0.05-4.99 ng/m (mean 2.03 ng/m). Exposure evaluation indicated that the ingestion was the predominant exposure pathway for daily intake of perchlorate via size-segregated APM, and children are more likely to intake more perchlorate via APM than adults. We suggested that the risk of exposure to perchlorate for children is worthy of attention, and a further study is required, especially for seasonal variations. [ABSTRACT FROM AUTHOR]

Spore-forming bacteria, principally Bacillus species, are important contaminants of milk. Because of their high heat resistance, Bacillus species spores are capable of surviving the heat treatment process of milk and lead to spoilage of the final product. To determine the factors influencing the contamination of milk, sporeforming bacteria occurrence throughout the UHT milk production line during winter, spring, and summer was studied. The obtained results confirm that the total viable rate decreases rapidly throughout the production line of UHT milk showing the efficiency of thermal treatments used. However, the persistent high rate of spore-forming bacteria indicates their high heat resistance, especially in spring and summer. In addition, a significant variation of the quality of raw milk according to the location of the collecting centers was revealed. The molecular identification showed a high degree of diversity of heat-resistant Bacillus species, which are isolated from different milk samples. The distribution of Bacillus species in raw milk, stored milk, bactofuged milk, pasteurized milk, and UHT milk were 28, 10, 16, 13, and 33%, respectively. Six Bacillus spp. including Bacillus licheniformis (52.38%), Bacillus pumilus (9.52%), Bacillus sp. (4.76%), Bacillus sporothermodurans (4.76%), Terribacillus aidingensis (4.76%), and Paenibacillus sp. (4.76%) were identified in different milk samples. [ABSTRACT FROM AUTHOR]

The nitrogen (N) cycle is highly dependent on microbial processes. Distribution of these communities is one of the most important factors in the variation of the N cycling in warm-monomictic lakes. However, the effects of the alternation of water stratification and mixing periods on the ecology of microbial communities involved in these processes are rarely studied in this type of aquatic ecosystem., We explored vertical and seasonal patterns of picoplankton and the genetic potential for ammonium oxidation ( amoA gene for bacteria and archaea), denitrification ( nirS and nirK), anammox ( hzsA), and DNRA ( nrfA) and their relationships with the main limnological variables in Lake Alchichica (Central Mexican Plateau) to provide insight into the distribution and importance of these planktonic communities in warm-monomictic tropical lakes. Ten depths were sampled during late stratification (November 2015) and mixing (February 2016) periods, covering the epilimnion, metalimnion (oxycline), and hypolimnion layers in the first case., We showed that temperature and oxygen stratification shaped the distribution of picoplankton and functional N genes in this lake. These communities also varied in relation to nutrient availability and underwent temporal changes throughout the water column. The amoA genes, along with autotrophic picoplankton, were more abundant during the stratification, indicating that nitrification could be potentially more important during this period, mainly at the oxycline layer. Denitrifying genes showed strong variations during the stratification period, with highest gene copy numbers at the oxycline and hypolimnion layers. Anoxic conditions were characterised by a relative increase in the abundance of the nrfA gene with depth, which was positively correlated with NH4+ concentration. On the other hand, the hzsA gene was not detected in any sample., Our findings highlight the importance of thermal stratification as one of the main factors influencing the genetic potential for N transformations within the water column in warm-monomictic tropical lakes. [ABSTRACT FROM AUTHOR]

Cyanobacteria associated with biological soil crusts (BSCs) have important attributes, such as nitrogen fixation and soil stabilisation. However, research on these organisms has been minimal, and their diversity and distribution throughout temperate Europe is currently unknown. The SCIN (Soil Crust International) project is a multidisciplinary research initiative that aims to achieve improved understanding of the BSCs of Europe, one facet being an investigation into the cyanobacterial communities of BSCs across a latitudinal gradient. Cyanobacteria assemblages were analysed by both morphological and molecular analysis. Two treatments were applied prior to DNA extraction, continued sample wetting and a dry sample process, and 16S ribosomal RNA (rRNA) amplicons were processed by Illumina MiSeq sequencing. The results reveal high and variable cyanobacterial diversity with each site showing a unique assemblage. Many common cyanobacterial genera, for example Nostoc and Microcoleus, were found in all sites but the abundances of different genera varied considerably. The polyphasic approach was found to be essential in recording the presence of important cyanobacteria that a single method itself did not highlight. The wet and dry treatments showed some differences in diversity, but mainly in abundance, this may suggest how cyanobacterial composition of BSCs changes with seasonal variability. [ABSTRACT FROM AUTHOR]

The present study investigated the relationship between accumulations of heavy metals and the concentration of chlorophyll, as well as the number, secondary production and enzymatic activity of bacteria in the surface microlayer (SML) and subsurface waters of a coastal Baltic lake. Concentration of heavy metals was measured by mass spectrometry, chlorophyll by spectrophotometry, bacteria abundance by DAPI staining, secondary production by 3H-thymidine incorporation into DNA and enzymatic activities using fluorescence-labelled substrate methods. Concentrations of all the analysed heavy metals, chlorophyll, as well as the number of heterotrophic bacteria and the level of enzymatic activity were higher in the SML than in subsurface water. No differences in the total number of bacteria in both the studied layers were noted. The rate of secondary production of planktonic bacteria was found to be higher than that of neustonic bacteria. Seasonal variability was observed in the studied chemical and microbiological parameters. It was found that in SML heavy metal concentrations increased in relation to those in subsurface water. However, this did not reduce the level of chlorophyll, heterotrophic bacteria, or the enzymatic activity. In contrast, increased heavy metal concentrations in SML reduced total number of bacteria and the level of secondary productivity. [ABSTRACT FROM AUTHOR]

Aerobic nitrite oxidation in marine environments plays a key role in the nitrification process. Marine bacteria involved in this nitrate-producing process have however been seldom studied compared with the ammonia-oxidizing community. Here, we report for the first time the community structure of aerobic nitrite-oxidizing bacteria ( NOB) in the seasonal upwelling and oxygen-deficient area off Central Chile. Analysis of 16 S rRNA by tag pyrosequencing was combined with specific quantitative polymerase chain reaction ( qPCR) and reverse transcription qPCR in summer and wintertime. N itrospina-like bacteria were the only known NOB detected by means of pyrosequencing between 30 and 80 m depth, accounting for up to 5% of total bacteria. This guild was represented by 11 and 7 operational taxonomic units (97% cut-off) in winter and summertime respectively. N itrospina-like bacteria were phylogenetically related to sequences retrieved from coastal upwelling, oxygen minimum zones and deep-sea environments. This group was also detected by qPCR with abundances that increased with depth throughout the water column. Importantly, N itrospina from surface layers showed low abundances but high 16 S rRNA : rDNA ratios and mainly in summertime. Overall, our results highlight the seasonal variability between the structure and physiological state of this community and suggest a significant role of N itrospina in the nitrogen cycle of seasonal upwelling areas. [ABSTRACT FROM AUTHOR]

Tetrodotoxin (TTX) is a well-known marine toxin, which is widely distributed in marine animals and originates from marine bacteria. To compare seasonal characteristics of aerobic bacteria in the toxic gastropod Oliva hirasei, the muscle and digestive gland of O. hirasei were collected from New Taipei City, and plated on ORI agar for aerobic plate count. Bacterial counts of the digestive gland were 7.10 and 8.89 log (CFU/g) from O. hirasei in August 2011 and March 2012, respectively, and those of the muscle were 6.84 and 8.20 log (CFU/g) in August 2011 and March 2012, respectively. The total bacterial counts in the March samples were higher than those in the August samples, but the amount of toxin showed an inverted pattern. The predominant genera from the muscle and digestive gland of O. hirasei were Vibrio, Pseudomonas, Shewanell, Pasteurella, Aeromonas, and others. Virio was 43 and 46% of the genera in August from the muscle and the digestive gland of O. hirasei and 70 and 82% in March. In addition, to detect the TTX-producing ability of isolated bacteria, the bacterial strains were cultured, extracted, and analyzed by HPLC and LC-MS/MS. The results showed that Vibrio, Pseudomonas, and Shewanella certainly produced TTX. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the impact of urbanization and seasonal changes on the prevalence of antibiotic-resistant bacteria in different aqueous environments. To this end, bacteria were isolated from three different water sources: the River Hooghly in Kolkata, River Kangsabati and groundwater from Kharagpur, West Bengal over three seasons: post-monsoon, winter and summer in 2012-2013. A total of 163 Gram-negative bacteria were isolated from the River Hooghly ( n = 138), River Kangsabati ( n = 13) and groundwater ( n = 12). Antibiotic susceptibility testing was done using 12 antibiotic discs. The percentages of multiple antibiotic-resistant (MAR) bacteria at the three sampling locations were found to be 71.01 % (98/138) for River Hooghly, 15.38 % (2/13) for River Kangsabati and 8.33 % (1/12) for groundwater. Prevalence of MAR bacteria with respect to the three seasons were the following: 73.58 % in post-monsoon, 59.26 % in winter and 53.57 % in summer. Antibiotic resistance index (ARI) was calculated for each location and each season. In general, ARI values for all the River Hooghly samples were >0.2 while those for the River Kangsabati and groundwater in Kharagpur were always <0.2 indicating greater exposure to antibiotics and subsequent resistance in bacteria from the River Hooghly compared to the other two locations. In addition, percentage of MAR and ARI values followed the trend: post-monsoon > winter > summer. This may be due to the additional terrestrial resistants that get swept along with surface runoff during the monsoons. [ABSTRACT FROM AUTHOR]

Background: We investigated the relationship between average monthly temperature and the most common clinical pathogens causing infections in intensive care patients. Methods: A prospective unit-based study in 73 German intensive care units located in 41 different hospitals and 31 different cities with total 188,949 pathogen isolates (102,377 Gram-positives and 86,572 Gram-negatives) from 2001 to 2012. We estimated the relationship between the number of clinical pathogens per month and the average temperature in the month of isolation and in the month prior to isolation while adjusting for confounders and long-term trends using time series analysis. Adjusted incidence rate ratios for temperature parameters were estimated based on generalized estimating equation models which account for clustering effects. Results: The incidence density of Gram-negative pathogens was 15% (IRR 1.15, 95%CI 1.10–1.21) higher at temperatures ≥20°C than at temperatures below 5°C. E. cloacae occurred 43% (IRR = 1.43; 95%CI 1.31–1.56) more frequently at high temperatures, A. baumannii 37% (IRR = 1.37; 95%CI 1.11–1.69), S. maltophilia 32% (IRR = 1.32; 95%CI 1.12–1.57), K. pneumoniae 26% (IRR = 1.26; 95%CI 1.13–1.39), Citrobacter spp. 19% (IRR = 1.19; 95%CI 0.99–1.44) and coagulase-negative staphylococci 13% (IRR = 1.13; 95%CI 1.04–1.22). By contrast, S. pneumoniae 35% (IRR = 0.65; 95%CI 0.50–0.84) less frequently isolated at high temperatures. For each 5°C increase, we observed a 3% (IRR = 1.03; 95%CI 1.02–1.04) increase of Gram-negative pathogens. This increase was highest for A. baumannii with 8% (IRR = 1.08; 95%CI 1.05–1.12) followed by K. pneumoniae, Citrobacter spp. and E. cloacae with 7%. Conclusion: Clinical pathogens vary by incidence density with temperature. Significant higher incidence densities of Gram-negative pathogens were observed during summer whereas S. pneumoniae peaked in winter. There is increasing evidence that different seasonality due to physiologic changes underlies host susceptibility to different bacterial pathogens. Even if the underlying mechanisms are not yet clear, the temperature-dependent seasonality of pathogens has implications for infection control and study design. [ABSTRACT FROM AUTHOR]

Abstract: The abundance and structure of Bacteroidetes populations at diverse temporal and spatial scales were investigated in the Northwestern Mediterranean Sea. At a temporal scale, their relative abundance exhibited a marked seasonality, since it was higher in spring and decreased in winter. Similarly, Bacteroidetes community structure encompassed three main groups (winter, spring and summer-fall), which mimicked global bacterioplankton seasonality. At the spatial scale, relative abundances were similar in all surface samples along an inshore–offshore transect, but they decreased with depth. Analysis of the community structure identified four markedly different groups mostly related to different depths. Interestingly, seasonal changes in abundance and community structure were not synchronized. Furthermore, richness was higher when Bacteroidetes were less abundant. The variability of Bacteroidetes contributions to community structure in the temporal and spatial scales was correlated with different environmental factors: day length was the most important factor at the temporal scale, and salinity at the spatial scale. The community composition in terms of phylotypes changed significantly over time and along the depth gradients, but season or depth-specific phylogenetic clusters were not identified. Delineation of coherent Bacteroidetes sub-clusters should help to uncover higher resolution patterns within Bacteroidetes, and explore associations with environmental and biological variables. [Copyright &y& Elsevier]

Highlights: [•] The optimal conditions of AORs were investigated according to seasonal changes. [•] The optimum temperature and pH of specific AORs showed seasonal variations. [•] There were no seasonal changes in AOB communities. [•] Variations in optimal conditions relied on the acclimation of a stable AOB community. [Copyright &y& Elsevier]

Genomic approaches to characterizing bacterial communities are revealing significant differences in diversity and composition between environments. But bacterial distributions have not been mapped at a global scale. Although current community surveys are way too sparse to map global diversity patterns directly, there is now sufficient data to fit accurate models of how bacterial distributions vary across different environments and to make global scale maps from these models. We apply this approach to map the global distributions of bacteria in marine surface waters. Our spatially and temporally explicit predictions suggest that bacterial diversity peaks in temperate latitudes across the world's oceans. These global peaks are seasonal, occurring 6 months apart in the two hemispheres, in the boreal and austral winters. This pattern is quite different from the tropical, seasonally consistent diversity patterns observed for most macroorganisms. However, like other marine organisms, surface water bacteria are particularly diverse in regions of high human environmental impacts on the oceans. Our maps provide the first picture of bacterial distributions at a global scale and suggest important differences between the diversity patterns of bacteria compared with other organisms. [ABSTRACT FROM AUTHOR]

Seasonal and spatial variations of both levels and characteristics of airborne bacteria and fungi in various types of non-complaint indoor environments and their outdoors were investigated. Bioaerosol samples were collected by the single-stage Andersen sampler during the winter and summer seasons in Ankara, Turkey. Indoor and outdoor temperature, relative humidity (RH) and CO2 concentrations were also monitored online during the sampling. Bacteria levels in apartments were found to be considerably elevated when people were present. Significant relationships between bioaerosol levels and RH and CO2 concentrations (p<0.05) were found. Bacteria levels exhibited a seasonal variation, while fungi levels did not, probably due to lower fungi concentrations occurrence as a result of lower RH values (median: 30%). Measured low levels of fungi in this study may be due to geographical conditions, climatic factors, and other environmental conditions. The indoor to outdoor (I/O) ratio for bacteria levels were found to be significantly higher than 1.0, while indoor and outdoor fungi levels were similar. Winter to summer (W/S) ratios in the sampling site groups varied on a large scale for both culturable fungi concentrations (0.24–19.59) and total bacteria count (0.16–6.59). The most prominent bacteria were Micrococcus spp., Staphylococcus spp. and Bacillus spp., while the most predominant fungi were Penicillium spp., Aspergillus spp. and Cladosporium spp. [ABSTRACT FROM AUTHOR]

A seasonal variation study was performed on the chemical composition of the essential oil of Agathosma ovata (Rutaceae). In addition, this study looked at how variations may impact the antimicrobial activity of A. ovata. The chemical composition of 10 monthly samples, as determined by GC and GC/MS, were found to differ qualitatively and quantitatively and the analysis resulted in the identification of 144 compounds. Sabinene was the major compound in the oil and ranged between 25-44% over the year. The antimicrobial activity was evaluated using the minimum inhibitory concentration (MIC) method on four pathogens, i.e. Staphylococcus aureus, Bacillus cereus, Klebsiella pneumoniae and Candida albicans. Most of the samples had MIC values of 8 mg/mL. The activity for Staphylococcus aureus showed the greatest fluctuation (1.5-14 mg/mL) over the seasonal period. [ABSTRACT FROM AUTHOR]

Antibiotic residues and antibiotic resistance genes (ARGs) have been found worldwide. Chloramphenicol, one of antibiotics, had been banned for its use in breeding industry in many countries. The status about chloramphenicol resistance genes (CRGs) in mangrove ecosystems is still unknown. In the present study, quantitative PCR was employed to investigate the abundance of CRGs. The residual determination of chloramphenicols was performed via ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Although the concentrations of chloramphenicol residues were at undetectable or relatively low levels, the abundance of CRGs was still alarming. The CRG abundance was dynamically different with the season change, and was highest in the surface layer and gradually decreased with the sampling sites away from the mangrove. The 16S rRNA high-throughput gene sequencing results revealed that cyanobacteria , fusobacteria and planctomycetes were the most dominant phyla co-occurring with CRGs. The results indicated that antibiotic residues could make a long term impacts on the environment eventhough after their degradation. • Chloramphenicol-resistance genes (CRGs) presented in mangrove were firstly reported. • CRGs had obvious temporal and spatial distributions in the mangrove area. • Co-occurrence patterns of bacteria and CRGs were explored by network analysis. [ABSTRACT FROM AUTHOR]

The Nanfei River, located in Hefei City, Anhui Province, subjected to increased nutrient loads from point and/or non-point source. Little is known about the indicators indicating heterogeneity of surface sediments. We aimed to identify the suitable indicators that can reflect the sediment heterogeneity by analyzing the sensitivity of sediment physicochemical properties group, microbial communities and diversity indices group and C, N, S-functional genes group to seasonal and regional changes. River sediments from different areas (urban area, urban-rural fringe and rural area) were collected in the level, dry and wet seasons, respectively. The chemical parameters had most significant regional heterogeneity, but no seasonal differences. Seasons had a greater impact on the overall microbial community structure than the areas. Specifically, the relative abundance of Firmicutes and Bacteroidetes were more sensitive to seasonal changes. Overall, seasonal changes showed the greatest impact on the functional genes group, with the S-functional genes (dsrB and aprA) group providing the clearest seasonal variation. Considering the seasonal distribution of functional genes and their sensitivity to environmental factors, we speculated that the sulfate-reducing gene (dsrB), the methanogenic gene (mcrA) and the anammox gene (hzo) could be identified as sensitive indicators to indicate the seasonal heterogeneity of surface sediments in different river sections of the same river in the short term. We also concluded that environmental variables were more conducive to indicating the regional heterogeneity of sediments. This study provided a valuable reference for assessing the heterogeneity or ecological stress of river sediments. • The chemical properties group had obvious regional heterogeneity. • Region showed a weak effect on sediment microbiota and functional genes groups. • Seasonal changes showed the greatest impact on the functional genes group. • The dsrB , mcrA and hzo genes were sensitive indicators of seasonal heterogeneity. [ABSTRACT FROM AUTHOR]

The episodic monsoon condition in a tropical estuarine environment inputs high allochthonous materials that are rich in carbohydrates and are mainly broken down by enzymatic hydrolysis thus alter both organic matter and microbial community composition of an estuary. β-Glucosidases are one of the enzymes mediating the degradation of carbohydrates and are majorly produced by heterotrophic bacteria. The present study elucidated β-glucosidase-producing culturable bacterial diversity and measured their activity during non-monsoon and monsoon seasons in Zuari estuary. The results revealed that both bacterial abundance and β-glucosidase activity decreased significantly from non-monsoon to monsoon, whereas phylogenetic diversity increased. Majority of β-glucosidase producers during non-monsoon belonged to the members of Bacillales (53%), Pseudomonadales (26%), and Vibrionales (11%) which shifted to the members of Enterobacteriales (51%), Bacillales (14%), Alteromonadales (12%), Aeromonadales (9%), Xanthomonadales (7%), Pseudomonadales (5%), and Flavobacteriales (2%) during the monsoon. The shift in bacterial community structure points out the occurrence of different allochthonous forms with carbohydrate-metabolizing ability during the monsoon, and their relevance in ecology and health of this estuary can be elucidated by studying their functional diversity and is a step ahead. [ABSTRACT FROM AUTHOR]

Studying the composition and structure of bacterial communities in sediments helps to understand the contribution of bacteria to environmental changes and the role of feedback in response to disturbances. However, seasonal changes in bacterial communities of river sediments with different pollution levels and sources have not been clear yet. In this study, we collected sediment samples during the dry season, wet season and level season from 40 sites with various pollution sources in three inflow rivers (Fengle-Hangbu River, Nanfei River and Zhegao River) of Chaohu Lake. Bacterial community compositions were determined based on high-throughput sequencing. The 'Bioenv' in the R package 'Vegan' and redundancy analysis was used to explore the influence of environmental factors on the bacterial community in the river sediments. Results showed that a significant deviation in bacterial communities was found among seasons and rivers. In addition, seasonal dynamics had a greater impact on shaping bacterial communities than rivers with different pollution sources. A higher diversity was found in the wet season as compared to the other seasons. The bacterial diversity was negatively correlated with nutrients (OM, TN, NH 4 +, IP, OP and TP) and metals (Cu and Zn). Bacterial communities were more sensitive to heavy metals pressure than nutrients. We also concluded that heavy metals (Cu and Cd) were the key contributing factors in explaining variations in bacterial communities. This study provided a valuable reference for assessing ecological stress. Image 1 • Higher diversity in wet season was found compared with that in dry and level seasons. • Communities varied more in seasons than in rivers with different pollution sources. • The proportion of Flavobacterium was greater in less polluted river. • Bacterial communities were more sensitive to metals than nutrients. • Cu and Cd were the important driving factors to community differences. [ABSTRACT FROM AUTHOR]

Mining-affected waters are a huge challenge to natural ecosystems. At a mine site in Finnish Lapland, mining-affected waters are purified in two treatment peatlands (TPs) before they are released into downstream waters. The TPs experience long winters and are snow- and partly ice-covered from October to May. Contaminants in inflow waters include nitrogen compounds, sulfate, metals and metalloids (e.g. arsenic, antimony, nickel). The TPs were intensively monitored from 2015 to 2018 (water quality, air and peat temperatures, snow- and ice-cover, groundfrost depth). Snow- and ice-cover thickness as well as ground-frost depth were assessed throughout the winter, and soil temperatures were recorded continuously in different peat layers year-round. Maximal ground-frost depth of up to 30 cm were observed in March and April. Lower peat layers, however, remained unfrozen throughout the winter with temperatures ranging from 1 to 5ºC.Removal of nitrogen and sulfate was higher in summer months while removal of arsenic, antimony and nickel was similar throughout the year. Potential process rates for aerobic respiration, arsenic/antimony turnover and sulfate reduction were assessed at different incubation temperatures in microcosm studies with peat soil. Potential process rates were generally higher at higher incubation temperatures and decreased with decreasing temperatures, but significant rates were also observed at temperatures close to 0ºC. Thus, microbes are potentially active in the deeper layers of the TPs even in cold winter months. The composition of the (active) microbial community was compared in soil samples taken in triplicate at 4-6 weeks intervals from 2 depths (10 cm, 70 cm) from both TPs in winter 2015/2016. The community composition of the samples was compared on DNA and cDNA level by length-heterogeneity PCR (LH-PCR) of the bacterial 16S rRNA gene and samples were selected for additional next-generation sequencing of 16S rRNA gene amplicons based on the LH-PCR results. LH-PCR revealed differences in microbial community composition between the two TPs, the two layers in the TPs and the months while amplicon sequencing identified the active microbial players. Triplicate samples generally clustered closely together and were separated from samples taken at different timepoints, indicating seasonal variations in the (active) microbial community. Based on amplicon sequencing of cDNA the most active taxa included Proteobacteria, Chloroflexi and Acidobacteria, and the relative abundance of individual taxa varied throughout the year.The collective results showed that (i) microorganisms in the studies TPs are subjected to cold temperatures in winter time, (ii) contaminant removal in TPs shows seasonal variations, (iii) peat microorganisms have the potential to catalyze removal-related processes even in the winter time, and (iv) there are seasonal differences in the active microbial communities in TPs. [ABSTRACT FROM AUTHOR]

The quality of the groundwater along the slopes of Mount Meru, Tanzania, is poorly understood. Water access and sanitation practices may pose health risks to communities. This study was undertaken to assess the sources, abundance and seasonal variation of coliform bacteria in groundwater and factors contributing to such variations along slopes of Mount Meru, Tanzania. Water samples collected from 67 randomly selected water sources (springs, shallow wells which ranged from 4 to 35 m deep and Boreholes above 40 m deep) during dry and wet seasons were analysed for total coliform (TC), faecal coliform (FC), Escherichia coli (E. coli) and faecal streptococci (FS), using the membrane filtration method. The fraction of springs and shallow wells contaminated was generally higher compared to the fraction of boreholes. The highest TC, FC, E. coli and FS counts were significantly higher (p < 0.05) during the wet than the dry season owing to rising of water table and leaching during rainy season. Water sources that were located within 10 m of pit latrines had the highest coliform counts relative to those located beyond 10 m. Similarly, the highest coliform counts were observed in all shallow wells that (i) had low well head above the ground, (ii) were not covered, (iii) had casing materials which were not concrete and (iv) utilised traditional pumping (bucket/pulley) systems. This was due to contaminated storm water access, inoculation of microbes by exposed buckets and inefficiency of the casing material. Furthermore, the counts decreased with depths of boreholes and shallow wells during the two seasons probably due to retention and die-off. It is recommended that groundwater in this area be treated against coliform contamination prior to utilisation as portable water. [ABSTRACT FROM AUTHOR]