Majority Of Operational Taxonomic Units Research Articles

Comparison of the Peel-Associated Epiphytic Bacteria of Anthocyanin-Rich "Sun Black" and Wild-Type Tomatoes under Organic and Conventional Farming.

Tomatoes are among the most consumed vegetables worldwide and represent a source of health-beneficial substances. Our study represents the first investigating the peel-associated epiphytic bacteria of red and purple (anthocyanin-rich) tomatoes subjected to organic and conventional farming systems. Proteobacteria was the dominant phylum (relative abundances 79-91%) in all experimental conditions. Enterobacteriaceae represented a large fraction (39.3-47.5%) of the communities, with Buttiauxella and Atlantibacter as the most represented genera. The core microbiota was composed of 59 operational taxonomic units (OTUs), including the majority of the most abundant ones. The occurrence of the most abundant OTUs differed among the experimental conditions. OTU 1 (Buttiauxella), OTU 2 (Enterobacteriales), and OTU 6 (Bacillales) were higher in red and purple tomatoes grown under organic farming. OTU 5 (Acinetobacter) had the highest abundance in red tomatoes subjected to organic farming. OTU 3 (Atlantibacter) was among the major OTUs in red tomatoes under both farming conditions. OTU 7 (Clavibacter) and OTU 8 (Enterobacteriaceae) had abundances ≥1% only in red tomatoes grown under conventional farming. PCA and clustering analysis highlighted a high similarity between the bacterial communities of red and purple tomatoes grown under organic farming. Furthermore, the bacterial communities of purple tomatoes grown under organic farming showed the lowest diversity and evenness. This work paves the way to understand the role of nutritional superior tomato genotypes, combined with organic farming, to modulate the presence of beneficial/harmful bacteria and supply healthier foods within a sustainable agriculture.

Differential oral microbiome in nonhuman primates from periodontitis-susceptible and periodontitis-resistant matrilines.

Rhesus monkeys (n=36) exhibiting a healthy periodontium at baseline were used to induce progressing periodontitis through ligature placement around premolar/molar teeth. Bacterial samples were collected at baseline, 0.5, 1, and 3 months of disease and at 5 months for disease resolution. The animals were distributed into two groups (18/group): 3-7 years (young) and 12-23 years (adult) and stratified based upon matriline susceptibility to periodontitis (PDS, susceptible; PDR, resistant). A total of 444 operational taxonomic units (OTUs) with 100 microbes representing a core microbiome present in ≥75% of the samples were identified. Only 48% of the major phylotypes overlapped in the PDS and PDR samples. Different OTU abundance patterns were seen in young animals from the PDS and PDR matrilines, with qualitative similarities during disease and the relative abundance of phylotypes becoming less diverse. In adults, 23 OTUs were increased during disease in PDS samples and 24 in PDR samples; however, only five were common between these groups. Greater diversity of OTU relative abundance at baseline was observed with adult compared to young oral samples from both the PDS and PDR groups. With disease initiation (2weeks), less diversity of relative abundance and some distinctive increases in specific OTUs were noted. By 1 month, there was considerable qualitative homogeneity in the major OTUs in both groups; however, by 3 months, there was an exacerbation of both qualitative and quantitative differences in the dominant OTUs between the PDS and PDR samples. These results support that some differences in disease expression related to matriline (familial) periodontitis risk may be explained by microbiome features.

Municipal Wastewaters Carry Important Carbapenemase Genes Independent of Hospital Input and Can Mirror Clinical Resistance Patterns.

ABSTRACTThe spatiotemporal variation of several carbapenemase-encoding genes (CRGs) was investigated in the influent and effluent of municipal WWTPs, with or without hospital sewage input. Correlations among gene abundances, bacterial community composition, and wastewater quality parameters were tested to identify possible predictors of CRGs presence. Also, the possible role of wastewaters in mirroring clinical resistance is discussed. The taxonomic groups and gene abundances showed an even distribution among wastewater types, meaning that hospital sewage does not influence the microbial diversity and the CRG pool. The bacterial community was composed mainly of Proteobacteria, Firmicutes, Actinobacteria, Patescibacteria, and Bacteroidetes. Acinetobacter spp. was the most abundant group and had the majority of operational taxonomic units (OTUs) positively correlated with CRGs. This agrees with recent reports on clinical data. The influent samples were dominated by blaKPC, as opposed to effluent, where blaIMP was dominant. Also, blaIMP was the most frequent CRG family observed to correlate with bacterial taxa, especially with the Mycobacterium genus in effluent samples. Bacterial load, blaNDM, blaKPC, and blaOXA-48 abundances were positively correlated with BOD5, TSS, HEM, Cr, Cu, and Fe concentrations in wastewaters. When influent gene abundance values were converted into population equivalent (PE) data, the highest copies/1 PE were identified for blaKPC and blaOXA-48, agreeing with previous studies regarding clinical isolates. Both hospital and non-hospital-type samples followed a similar temporal trend of CRG incidence, but with differences among gene groups. Colder seasons favored the presence of blaNDM, blaKPC and blaOXA-48, whereas warmer temperatures show increased PE values for blaVIM and blaIMP.IMPORTANCE Wastewater-based epidemiology has recently been recognized as a valuable, cost-effective tool for antimicrobial resistance surveillance. It can help gain insights into the characteristics and distribution of antibiotic resistance elements at a local, national, and even global scale. In this study, we investigated the possible use of municipal wastewaters in the surveillance of clinically relevant carbapenemase-encoding genes (CRGs), seen as critical antibiotic resistance determinants. In this matter, our results highlight positive correlations among CRGs, microbial diversity, and wastewater physical and chemical parameters. Identified predictors can provide valuable data regarding the level of raw and treated wastewater contamination with these important antibiotic resistance genes. Also, wastewater-based gene abundances were used for the first time to observe possible spatiotemporal trends of CRGs incidence in the general population. Therefore, possible hot spots of carbapenem resistance could be easily identified at the community level, surpassing the limitations of health care-associated settings.

New insights into Danube’s macroinvertebrate communities from DNA metabarcoding as part of the Joint Danube Survey 4 (JDS4)

The Joint Danube Survey (JDS) is a multinational effort in monitoring Danube’s water quality, including its major tributaries. The Danube river stretches over a distance of 2,800 km and flows through or borders 10 different countries to which it is of utter importance as a source of potable water and hydrodynamic power. The JDS is conducted every 6 years and provides a unique opportunity to collect comprehensive data on both abiotic parameters and organisms and to raise awareness of the importance of water as a natural resource. As part of JDS and as a biological quality element in many monitoring programs worldwide, macroinvertebrates are monitored as indicators for various environmental conditions. However, due to their diverse taxonomic composition, associated difficulties with their morphology-based identification as well as their sheer abundance, macroinvertebrates are often analysed with a low taxonomic resolution (i.e., above species level). As an alternative, DNA metabarcoding offers a promising approach to capture this species diversity more accurately. Here, we used DNA metabarcoding to investigate the macrozoobenthic diversity of 46 sites from the latest JDS sampling campaign in 2019. To analyse macroinvertebrate diversity, bulk samples were taken by kick-net sampling and analysed using two different approaches, analysing the bulk sample fixative and analysing homogenised organisms from complete bulk samples. DNA metabarcoding of the sample fixative revealed 1,146 Operational Taxonomic Units (OTUs) and 231 species compared to 833 OTUs and 333 species from homogenised sample analysis. While more dipterans, in particular Chironomidae, were detected in fixative (136 species) than homogenised bulk (90 species) analyses, the latter picked up more Trichoptera (19 vs. 2), Amphipoda (10 vs. 4) and Bivalvia species (13 vs. 5). Even though these results of a DNA-based assessment deliver new insights into species richness and composition of Danube’s macroinvertebrate communities from the Danube source to its delta already, it is evident that the majority of OTUs was not assigned to species. While filling this lack of reference sequences poses a major challenge, the JDS consortium also offers a unique opportunity to complement reference databases in a multinational effort towards a more comprehensive Danube assessment and monitoring.

From Forest Soil to the Canopy: Increased Habitat Diversity Does Not Increase Species Richness of Cercozoa and Oomycota in Tree Canopies.

Tree canopies provide habitats for diverse and until now, still poorly characterized communities of microbial eukaryotes. One of the most general patterns in community ecology is the increase in species richness with increasing habitat diversity. Thus, environmental heterogeneity of tree canopies should be an important factor governing community structure and diversity in this subsystem of forest ecosystems. Nevertheless, it is unknown if similar patterns are reflected at the microbial scale within unicellular eukaryotes (protists). In this study, high-throughput sequencing of two prominent protistan taxa, Cercozoa (Rhizaria) and Oomycota (Stramenopiles), was performed. Group specific primers were used to comprehensively analyze their diversity in various microhabitats of a floodplain forest from the forest floor to the canopy region. Beta diversity indicated highly dissimilar protistan communities in the investigated microhabitats. However, the majority of operational taxonomic units (OTUs) was present in all samples, and therefore differences in beta diversity were mainly related to species performance (i.e., relative abundance). Accordingly, habitat diversity strongly favored distinct protistan taxa in terms of abundance, but due to their almost ubiquitous distribution the effect of species richness on community composition was negligible.

Do inferences about freshwater phytoplankton communities change when based on microscopy or high‐throughput sequencing data?

Abstract Microscopy and high‐throughput sequencing (HTS) detect and quantify algae differently. It is not known if microscopy‐based abundance or biomass better compare to HTS data or how methodological differences affect ecological inferences about the phytoplankton communities studied. We investigated methodological (abundancemicroscopy vs. abundanceHTS, biomassmicroscopy vs. abundanceHTS), habitat (littoral, pelagic, deep hypolimnion), and year (2014 vs. 2017) differences for phytoplankton communities of Lake Tovel (Italy) using ANOVA. Specifically, we tested the hypothesis that depending on comparing abundancemicroscopy or biomassmicroscopy to abundanceHTS different effects would be indicated; we called this the metric effect. Furthermore, using samples from 2014 to 2017, we investigated environment–community relationships by a redundancy analysis based on abundancemicroscopy, biomassmicroscopy, and abundanceHTS, and compared the results. Approximately 9 times more operational taxonomic units were reported with HTS (n2014 = 819, n2017 = 891) than algal taxa with microscopy (n2014 = 90, n2017 = 109) in 2014 and 2017. While microscopically assessed algal taxa were evenly distributed among phyla, the vast majority of operational taxonomic units were attributed to Chrysophyta (2014 = 54%, 2017 = 62%) and Bacillariophyta (2014 = 19%, 2017 = 17%). A metric effect for method differences was generally observed comparing abundancemicroscopy to abundanceHTS with Chlorophyta, Cryptophyta, and Dinophyta showing higher % abundance with microscopy while richness and Chrysophyta showed higher values with HTS. Almost no metric effects were found in 2014, but they were common across phyla in 2017. Bacillariophyta and Eustigmatophyta showed the same habitat differences when comparing biomassmicroscopy to abundanceHTS. Dinophyta showed habitat differences only with microscopy, while Chyrsophyta showed habitat differences only with HTS; these results were probably related to technical bias and strengths of HTS, respectively. Habitat differences of phyla were reasonably related to their ecological niche and linked to factors such as temperature and feeding preferences; furthermore, phyla often showed a significant 2014‐versus‐2017 year effect. The year 2014 was very wet while 2017 had a dry winter, and we attributed the patterns found to allochthonous nutrient input by rain and decreased turbulence. Redundancy analyses based on phytoplankton communities assessed with microscopy and HTS, respectively, equally indicated the importance of hydrology, nutrients, and temperature for phytoplankton communities and discriminated the littoral from the deep hypolimnion. However, variance explained was higher with HTS, and the pelagic was similar to the deep hypolimnion with microscopy but to the littoral with HTS. Despite the different strengths of microscopy and HTS for biodiversity assessment, both datasets outlined similar large‐scale patterns linked to strong environmental control of phytoplankton communities as they related to habitat and year differences. According to our hypothesis, metric effects were common; however, no general rule was found as to whether abundancemicroscopy or biomassmicroscopy should be compared to abundanceHTS. Notwithstanding metric effects, HTS‐based data provided similar and more detailed information than microscopy, supporting the promise of HTS becoming the tool of the future for biodiversity research.

Relationship between the bacterial community structures on human hair and scalp.

In this study, we investigated and compared characteristics of the bacterial community structures on hair (scalp hair) and scalp in 18 individuals. Significant differences were found between the sites, in terms of cell density, alpha and beta diversity, and relative abundance of the phyla, Firmicutes and Proteobacteria, whereas no difference was found in relative abundance of the phylum Actinobacteria. Bacteria of the genus Cutibacterium showed similar relative abundance at both sites, whereas those of genus Pseudomonas were highly abundant on hair, and those of genus Staphylococcus were significantly lesser in abundance on hair than on scalp. Statistical correlations between the sites were high for the individual relative abundance of five major operational taxonomic units (OTUs). This suggests that the bacterial community structure on hair is composed of hair-specific genus, Pseudomonas, and skin-derived genera, Cutibacterium and Staphylococcus, and is distinguishable from other human skin microbiomes.

Neutral Processes Dominate Microbial Community Assembly in Atlantic Salmon, Salmo salar.

In recent years, a wealth of studies has examined the relationships between a host and its microbiome across diverse taxa. Many studies characterize the host microbiome without considering the ecological processes that underpin microbiome assembly. In this study, the intestinal microbiota of Atlantic salmon, Salmo salar, sampled from farmed and wild environments was first characterized using 16S rRNA gene MiSeq sequencing analysis. We used neutral community models to determine the balance of stochastic and deterministic processes that underpin microbial community assembly and transfer across life cycle stage and between gut compartments. Across gut compartments in farmed fish, neutral models suggest that most microbes are transient with no evidence of adaptation to their environment. In wild fish, we found declining taxonomic and functional microbial community richness as fish mature through different life cycle stages. Alongside neutral community models applied to wild fish, we suggest that declining richness demonstrates an increasing role for the host in filtering microbial communities that is correlated with age. We found a limited subset of gut microflora adapted to the farmed and wild host environment among which Mycoplasma spp. are prominent. Our study reveals the ecological drivers underpinning community assembly in both farmed and wild Atlantic salmon and underlines the importance of understanding the role of stochastic processes, such as random drift and small migration rates in microbial community assembly, before considering any functional role of the gut microbes encountered.IMPORTANCE A growing number of studies have examined variation in the microbiome to determine the role in modulating host health, physiology, and ecology. However, the ecology of host microbial colonization is not fully understood and rarely tested. The continued increase in production of farmed Atlantic salmon, coupled with increased farmed-wild salmon interactions, has accentuated the need to unravel the potential adaptive function of the microbiome and to distinguish resident from transient gut microbes. Between gut compartments in a farmed system, we found a majority of operational taxonomic units (OTUs) that fit the neutral model, with Mycoplasma species among the key exceptions. In wild fish, deterministic processes account for more OTU differences across life stages than those observed across gut compartments. Unlike previous studies, our results make detailed comparisons between fish from wild and farmed environments, while also providing insight into the ecological processes underpinning microbial community assembly in this ecologically and economically important species.

Molecular Analysis of Selected Resistance Determinants in Diarrheal Fecal Samples Collected From Kolkata, India Reveals an Abundance of Resistance Genes and the Potential Role of the Microbiota in Its Dissemination.

Twenty-five diarrheal fecal samples from Kolkata were examined to determine the relative abundance of antimicrobial resistance genes (ARGs) against eight common classes of antibiotics with polymerase chain reaction (PCR) and Sanger sequencing. Relative abundance of an ARG was calculated as the percentage of fecal samples showing the presence of that particular ARG. The frequency of occurrence of resistance marker against each class of antibiotic was calculated as the percentage of fecal samples carrying at least one resistance marker for that particular class of antimicrobials. Antibiogram of Vibrio cholerae (V. cholerae) O1 strains isolated from four of these samples was obtained by disc diffusion method and was compared with the ARG profile of corresponding fecal samples from which the strains were isolated. A 464 bp amplicon of the V3-V4 region of bacterial 16S rDNA was obtained by PCR from 9 of these 25 samples using the primer pair S-D-Bact-0341-b-S-17 and S-D-Bact-0785-a-A-21 and sequenced to determine the major operational taxonomic unit (OTU). These 9 samples represented diarrhea due to diverse etiology and also unresolved etiology as determined by culture method. We conclude that the diarrheal intestinal microbiome has a common gene pool of ARGs against the major classes of antibiotics and may be serving as a reservoir of ARG dissemination. ARG profile of cholera stool showed that ARGs present in the gut of cholera patients may be transferred to the V. cholerae genome and pose a serious threat to the treatment of cholera by triggering resistance against potential drugs to which contemporary strains of V. cholerae were found to be sensitive in the present study. Fecal samples which were culture negative for diarrheal pathogens we tested also carried ARGs and OTU. Abundance of resistance markers against macrolides, tetracyclines, and aminoglycosides was the highest. Phylum Proteobacteria was the most abundant OTU suggesting proteobacterial blooms characteristic of disturbed gut microflora. Our study is the first comparative study of ARG profile of diarrheal samples with varying etiologic agent revealing the presence of ARGs against the most important classes of antibiotics in the gut of diarrheal patients by common, robust molecular methods, which are easily accessible by molecular epidemiological laboratories worldwide.

Corn and Soybean Host Root Endophytic Fungi with Toxicity Toward the Soybean Cyst Nematode.

Although fungal endophytes are commonly investigated for their ability to deter microbial plant pathogens, few studies have examined the activity of fungal root endophytes against nematodes. The soybean cyst nematode (SCN; Heterodera glycines), the most severe yield-limiting pathogen of soybean (Glycine max), is commonly managed through rotation of soybean with corn (Zea mays), a nonhost of the SCN. A total of 626 fungal endophytes were isolated from surface-sterilized corn and soybean roots from experimental plots in which soybean and corn had been grown under annual rotation and under 1, 3, 5, and 35 years of continuous monoculture. Fungal isolates were grouped into 401 morphotypes, which were clustered into 108 operational taxonomic units (OTUs) based on 99% sequence similarity of the full internal transcribed spacer region. Morphotype representatives within each OTU were grown in malt extract broth and in a secondary metabolite-inducing medium buffered with ammonium tartrate, and their culture filtrates were tested for nematicidal activity against SCN juveniles. A majority of OTUs containing isolates with nematicidal culture filtrates were in the order Hypocreales, with the genus Fusarium being the most commonly isolated nematicidal genus from corn and soybean roots. Less commonly isolated taxa from soybean roots included the nematophagous fungi Hirsutella rhossiliensis, Metacordyceps chlamydosporia, and Arthrobotrys iridis. Root endophytic fungal diversity in soybean was positively correlated with SCN density, suggesting that the SCN plays a role in shaping the soybean root endophytic community.

Comparison of pH and bacterial communities in the rumen and reticulum during fattening of Japanese Black beef cattle.

We used castrated and fistulated Japanese Black beef cattle (n=9) to measure the pH and bacterial communities in the rumen liquid, rumen solid, and reticulum liquid during early, middle, and late fattening stages (10-14, 15-22, and 23-30months of age, respectively). The pH was measured in the rumen and reticulum during the last 13days of each fattening stage and was significantly lower in the rumen at the early and middle fattening stage and in the reticulum during the late stage. Sequencing analysis indicated similar bacterial compositions in the rumen and reticulum liquid fractions and stability of bacterial diversity in the rumen and reticulum liquid fractions and rumen solid fraction. By contrast, major operational taxonomic units (OTUs), such as Ruminococcus bromii strain ATCC 27255 (OTU1, OTU10, and OTU15), were differently correlated to the fermentation parameters among the rumen and reticulum liquid fractions. Therefore, the long-term feeding of Japanese Black beef cattle with a high-concentrate diet might reverse the trend of pH in the rumen and reticulum during the late fattening stage, and the bacterial communities adapted to changes in fermentation by preserving their diversity throughout fattening.

Investigation of the Potential Effects of Host Genetics and Probiotic Treatment on the Gut Bacterial Community Composition of Aquaculture-raised Pacific Whiteleg Shrimp, Litopenaeus vannamei

This study presents the potential effects of the genetic background and use of probiotics on the gut bacterial composition of Pacific whiteleg shrimp (Litopenaeus vannamei) grown in an indoor aquaculture facility. The strains investigated were Shrimp Improvement Systems (SIS, Islamorada, FL, USA), a strain genetically selected for disease resistance, and an Oceanic Institute (OI, Oahu, HI, USA) strain, selected for growth performance. BioWish 3P (BioWish Technologies, Cincinnati, OH, USA) was the selected probiotic. The study consisted of two separate trials, where all shrimp were raised under standard industry conditions and fed the same diet. Shrimp were stocked in 2920 L production tanks at a density of 200/m3 and acclimated for 14 days. After the acclimation period, triplicate tanks were supplemented daily for a duration of 28 days with probiotics, while three other tanks did not receive any treatment (controls). During the 28-day trial period, there was no statistically supported difference (p > 0.05) in either performance or health status as a result of genetic background or probiotic treatment. However, differences in gut bacterial composition, as assessed by high throughput sequencing of amplicons generated from the V1-V3 region of the bacterial 16S rRNA gene, were observed. The relative abundance of five major operational taxonomic units (OTUs) were found to vary significantly across experimental groups (p < 0.05). Notably, operational taxonomic unit (OTU) SD_Shr-00006 was at its highest abundance in d43 SIS samples, with levels greater than d71 samples of the same genetic line or any of the OI shrimp samples. OTUs for SD_Shr-00098 displayed a similar type of profile, but with highest abundance in the OI genetic line and lowest in the SIS shrimp. SD_Shr-00004 showed an opposite profile, with highest abundance in the SIS d71 samples and lowest in the SIS d43 samples. Together, these results suggest that host genetic background can be an important determinant of gut bacterial composition in aquaculture-raised whiteleg shrimp and indicate that development of strategies to manipulate the microbiome of this important seafood will likely need to be customized depending on the genetic line.

Bacterial community pattern along the sediment seafloor of the Arctic fjorden (Kongsfjorden, Svalbard).

The Arctic region has been the focus of increasing attention as an ecosystem that is highly sensitive to changes associated with global warming. Although it was assumed to be vulnerable to changes in climate, a limited number of studies have been conducted on the surface sediment bacteria of Arctic fjorden. This study assessed the diversity and distribution pattern of bacterial communities in eight marine sediments along the seafloor in a high Arctic fjorden (Kongsfjorden, Svalbard). A total of 822 operational taxonomic units (OTUs) were identified by Illumina MiSeq sequencing, targeting the V3-V4 hypervariable regions of the 16S rRNA gene. In these surface marine sediments, more than half of the sequences belonged to the phylum Proteobacteria, followed by Bacteroidetes, Verrucomicrobia, Actinobacteria, Chloroflexi and Lentisphaerae. The bacterial genera Marinicella, Desulfobulbus, Lutimonas, Sulfurovum and clade SEEP-SRB4 were dominant in all samples. Analysis of similarity indicated that bacterial communities were significantly different among the inner, central and outer basins (r2 = 0.5, P = 0.03 < 0.05). Canonical correspondence analysis and permutation tests revealed that location depth (r2 = 0.87, P < 0.01), temperature (r2 = 0.88, P < 0.01) and salinity (r2 = 0.88, P < 0.05) were the most significant factors that correlated with the bacterial communities in the sediments. 28 differentially abundant taxonomic clades in the inner and outer basin with an LDA score higher than 2.0 were found by the LEfSe method. The Spearman correlation heat map revealed different degrees of correlation between most major OTUs and environmental factors, while some clades have an inverse correlation with environmental factors. The spatial patterns of bacterial communities along the Kongsfjorden may offer insight into the ecological responses of prokaryotes to climate change in the Arctic ecosystem, which makes it necessary to continue with monitoring.

Beyond the visual: using metabarcoding to characterize the hidden reef cryptobiome.

In an era of coral reef degradation, our knowledge of ecological patterns in reefs is biased towards large conspicuous organisms. The majority of biodiversity, however, inhabits small cryptic spaces within the framework of the reef. To assess this biodiverse community, which we term the ‘reef cryptobiome’, we deployed 87 autonomous reef monitoring structures (ARMS), on 22 reefs across 16 degrees latitude of the Red Sea. Combining ARMS with metabarcoding of the mitochondrial cytochrome oxidase I gene, we reveal a rich community, including the identification of 14 metazoan phyla within 10 416 operational taxonomic units (OTUs). While mobile and sessile subsets were similarly structured along the basin, the main environmental driver was different (particulate organic matter and sea surface temperature, respectively). Distribution patterns of OTUs showed that only 1.5% were present in all reefs, while over half were present in a single reef. On both local and regional scales, the majority of OTUs were rare. The high heterogeneity in community patterns of the reef cryptobiome has implications for reef conservation. Understanding the biodiversity patterns of this critical component of reef functioning will enable a sound knowledge of how coral reefs will respond to future anthropogenic impacts.

Community structures and genomic features of undesirable white colony-forming yeasts on fermented vegetables.

White colony-forming yeasts (WCFYs) often appear in fermented foods, depending on the storage method. Despite the ongoing research on fermented foods, the community and genome features of WCFYs have not been well studied. In this study, the community structures of WCFYs on fermented vegetables (kimchi) prepared with various raw materials were investigated using deep sequencing. Only eight operational taxonomic units (OTUs) were detected, indicating that the community structure of WCFYs on kimchi is very simple. The five most abundant OTUs represented Pichia kluyveri, Yarrowia lipolytica, Candida sake, Hanseniaspora uvarum, and Kazachstania servazzii. Using a culture-dependent method, 41 strains representing the five major OTUs were isolated from the surface of the food samples. Whole genomes of the five major yeast strains were sequenced and annotated. The total genome length for the strains ranged from 8.97 Mbp to 21.32 Mbp. This is the first study to report genome sequences of the two yeasts Pichia kluyveri and Candida sake. Genome analysis indicated that each yeast strain had core metabolic pathways such as oxidative phosphorylation; purine metabolism; glycolysis/gluconeogenesis; aminoacyl-tRNA biosynthesis; citrate cycle; but strain specific pathways were also found. In addition, no toxin or antimicrobial resistance genes were identified. Our study provides genome information for five WCFY strains that may highlight their potential beneficial or harmful metabolic effects in fermented vegetables.

Preservation of microbial DNA in marine sediments: insights from extracellular DNA pools.

Marine sediments harbour extracellular DNA (exDNA) not associated with currently living organisms. Including this exDNA in genetic surveys may distort abundance and diversity estimates of living prokaryotic communities. We separately extract exDNA and intracellular DNA (inDNA) from 11 horizons in a 10-m deep sediment core from Aarhus Bay (Denmark) that spans > 9000 years of Holocene sedimentation. We compare depth profiles of bacterial and archaeal 16S rRNA gene compositions to those of macrofaunal activity (bioturbation), sulfate and methane concentrations, sediment age and lithology. Among these variables, bioturbation shows the strongest relationship with the two DNA pools. In bioturbated surface sediments, the majority of Operational Taxonomic Units (OTUs) present in exDNA is absent from inDNA, thus belonging to microorganisms that were not alive at the time of sampling. Below the bioturbation zone, the two DNA pools display a much higher phylogenetic similarity. At all depths, the majority of exDNA and inDNA sequences show highest sequence similarities to sediment microorganisms, a finding that is additionally supported by separate analyses on low- and high-molecular weight exDNA. Our results indicate that in Aarhus Bay the vast majority of prokaryotic exDNA is turned over, thus not contributing to a genetic archive of past environmental change.

3-NOP vs. Halogenated Compound: Methane Production, Ruminal Fermentation and Microbial Community Response in Forage Fed Cattle.

The aim of this study was to investigate the effects of 3-nitrooxypropanol (3-NOP) and chloroform on methane (CH4) and H2 production, ruminal metabolites and microbial community structure in cattle fed a tropical forage diet. Eight rumen-fistulated steers were fed a roughage hay diet (Rhodes grass; Chloris gayana) for 31 days (control period). Four animals received the antimethanogenic compound chloroform (1.6 g chloroform–cyclodextrin/100 kg live weight (LW)) while the other four received 3-NOP (2.5 g 3-NOP/animal/day) for 21 days. Methane decrease compared with control period was similar for both treatments (30–38%) with no differences for expelled H2 between controls and treatments. Daily weight gain (DWG) was significantly increased when animals were treated with 3-NOP compared with chloroform and control. Regarding the ruminal fermentation parameters increases in ammonia, acetate and branched chain fatty acids were observed with both compounds compared with the controls. Also, methylamines, alcohols and dimethyl sulfone (DMSO2) concentrations were significantly increased with the treatments compared with control, being greater with 3-NOP. The rumen microbial analyses revealed a similar profile for both treatments, with a shift in operational taxonomic units (OTUs) assigned to the Prevotellaceae and Campylobacteraceae family. Moreover, major archaeal OTUs associated with Methanobrevibacter and Methanosphaera were significantly affected to varying extents based on the inhibitory treatments compared to the control. The abundance of the Methanobrevibacter spp. was decreased by 3-NOP and chloroform, while the Methanomassiliicoccaceae family was inhibited only by 3-NOP. The results suggest that despite the specific mode of action of 3-NOP on methanogens, inhibition of methanogenesis by both compounds resulted in similar responses in metabolism and microbial community structure in the rumen. We hypothesized that these changes were driven by the redirection of metabolic hydrogen ([H]) by both treatments. Therefore results from previous publications using chloroform as an inhibitor of methanogenesis may be useful in predicting ruminal microbiota and fermentation responses to 3-NOP.

Fungal succession and decomposition of composted aquatic plants applied to soil

Abstract Few studies have documented the pattern of fungal colonization and decomposition of composted aquatic plants applied for amending soil. In the present study, we demonstrated the fungal succession and its relationship with chemical changes in decomposing composted aquatic plants applied to soil, by performing a 6-month litterbag experiment incubating three types of composted aquatic plants differing in the years of composting. A total of 189 operational taxonomic units (OTUs) of fungi were detected, including 115 and 34 OTUs in Ascomycota and Basidiomycota, respectively. The OTU richness generally increased with the progression of decomposition and was not significantly different among the three types of composted aquatic plants. Redundancy analysis indicated the relationships among the fungal assemblages, type of composted aquatic plants, duration of decomposition, and chemical changes in composted aquatic plants. Fungal succession was generally characterized by the cumulative increase of major OTUs and was affected by the contents of extractives, total carbohydrates, total carbon, and total nitrogen in decomposing composted aquatic plants.

Diversity of dehalorespiring bacteria and selective enrichment of aryl halides-dechlorinating consortium from sedimentary environment near an oil refinery

ABSTRACTThis study demonstrated the potential for reductive dechlorination of aryl halides in a sedimentary environment by naturally occurring bacteria. A laboratory sediment microcosm and highly enriched, stable dechlorinating cultures were established using hydrogen as electron donor and 2,3-dichlorophenol (2,3DCP), monochlorophenol (MCP) and dichlorobenzene (DCB) as electron acceptors. 16S rRNA gene sequencing of dominant DGGE bands assigned detected phylotypes in chlorophenols (CPs) amended sediment microcosms to the genera Anaerospora, Pseudomonas, Desulfitobacterium, Clostridium, Mycobacterium, and Peptoclostridium, beside uncultured marine Bacterioplankton, Halochromatium and Sedimentibacter. Chlorobenzene (CB) amended sediments showed the same community in addition to Bacillus sp. Major operational taxonomic units (OTUs) in CPs enrichment cultures were assigned to Anaerospora hongkongensis, Pseudomonas stutzeri, Pseudomonas pseudoalcaligenes, Clostridium sp., Desulfitobacterium dichloroeliminans, beside unidentified marine bacterioplankton. Enrichment on DCB resulted in predominance of the same populations in addition to Peptoclostridium sp. and Dehalococcoides mccartyi. Dechlorination in enrichment cultures was mainly assigned to Desulfitobacterium and Dehalococcoides, which are both known for their ability to couple dechlorination to growth in a halorespiration way. Enrichment cultures containing Desulfitobacterium showed ortho dechlorination activity of 2,3DCP to 2 chlorophenol (2CP) and 3 chlorophenol (3CP). These results provided compelling evidence that sedimentary environments in the vicinity of oil refineries do harbor dehalorespiring bacteria capable of reductive dechlorination of various aryl halides pollutants.

Dynamic bacterial community changes in the autothermal thermophilic aerobic digestion process with cell lysis activities, shaking and temperature increase

Autothermal thermophilic aerobic digestion (ATAD) is conducted for stabilization of sludge waste and is driven by the action of various microorganisms under aerobic conditions. However, the mechanism controlling bacterial community changes during ATAD via three (initial, middle and final) phases is currently unclear. To investigate this mechanism, activity analysis and a microcosm assay with shaking were performed on a bacterial community during the initial, middle, and final phases of incubation. Cell lysis activities toward gram-negative bacteria, but not gram-positive bacteria, were detected in the ATAD samples in the middle and final phases. During shaking incubation in initial-phase samples at 30°C, major operational taxonomic units (OTUs) related to Acinetobacter indicus and Arcobacter cibarius dramatically increased along with decreases in several major OTUs. In middle-phase samples at 45°C, we observed a major alteration of OTUs related to Caldicellulosiruptor bescii and Aciditerrimonas ferrireducens, together with distinct decreases in several other OTUs. Final-phase samples maintained a stable bacterial community with major OTUs showing limited similarities to Heliorestis baculata, Caldicellulosiruptor bescii, and Ornatilinea apprima. In conclusion, the changes in the bacterial community observed during ATAD could be partially attributed to the cell lysis activity toward gram-negative bacteria in the middle and final phases. The microcosm assay suggested that certain physical factors, such as a high oxygen supply and shearing forces, also might contribute to bacterial community changes in the initial and middle phases, and to the stable bacterial community in the final phase of ATAD.