scholarly journals Stability of Microbial Community Profiles Associated with Compacted Bentonite from the Grimsel Underground Research Laboratory

mSphere ◽  
2019 ◽  
Vol 4 (6) ◽  
Author(s):  
Katja Engel ◽  
Sian E. Ford ◽  
Sara Coyotzi ◽  
Jennifer McKelvie ◽  
Nikitas Diomidis ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Relative Abundance ◽  
Corrosion Test ◽  
Research Laboratory ◽  
Bentonite Clay ◽  
Rrna Gene ◽  
Deep Geological Repository ◽  
Geological Repository ◽  
Underground Research Laboratory

ABSTRACT To assess the microbiology and corrosion potential of engineered components of a deep geological repository for long-term storage of high-level nuclear waste, the Materials Corrosion Test is being conducted at the Underground Research Laboratory in Grimsel, Switzerland. Modules containing metal coupons surrounded by highly compacted MX-80 bentonite, at two dry densities (1.25 and 1.50 g/cm3), were emplaced within 9-m-deep boreholes, and the first modules were retrieved after 13 months of exposure. Bentonite and associated module materials were sampled, and microbial communities and their distributions were assessed using 16S rRNA gene sequencing and phospholipid fatty acid (PLFA) analysis. Borehole fluid was dominated by amplicon sequence variants (ASVs) affiliated with Desulfosporosinus and Desulfovibrio, which are putatively involved in sulfate reduction. The relative abundance of these ASVs was lower for samples from inside the borehole module, and they were almost undetectable in samples of the inner bentonite layer. The dominant ASV in case and filter sample sequence data was affiliated with Pseudomonas stutzeri, yet its relative abundance decreased in the inner layer samples. Streptomyces sp. ASVs were relatively abundant in all bentonite core sample data both prior to emplacement and after 13 months of exposure, presumably as metabolically inactive spores or extracellular “relic” DNA. PLFA concentrations in outer and inner layer bentonite samples suggested cellular abundances of 1 × 106 to 3 × 106 cells/g, with similar PLFA distributions within all bentonite samples. Our results demonstrate consistent microbial communities inside the saturated borehole module, providing the first evidence for microbial stability under conditions that mimic a deep geological repository. IMPORTANCE The Materials Corrosion Test in Grimsel Underground Research Laboratory, Switzerland, enables an evaluation of microbiological implications of bentonite clay at densities relevant for a deep geological repository. Our research demonstrates that after 13 months of exposure within a granitic host rock, the microbial 16S rRNA gene signatures of saturated bentonite clay within the modules were consistent with the profiles in the original clay used to pack the modules. Such results provide evidence that densities chosen for this emplacement test are refractory to microbial activity, at least on the relatively short time frame leading to the first time point sampling event, which will help inform in situ engineered barrier system science. This study has important implications for the design of deep geological repository sites under consideration for the Canadian Shield.

scholarly journals Soil Depth Determines the Composition and Diversity of Bacterial and Archaeal Communities in a Poplar Plantation

Forests ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 550 ◽  
Author(s):  
Huili Feng ◽  
Jiahuan Guo ◽  
Weifeng Wang ◽  
Xinzhang Song ◽  
Shuiqiang Yu
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Microbial Communities ◽  
Relative Abundance ◽  
Rrna Gene ◽  
Poplar Plantation ◽  
Plantation Forest ◽  
Bacterial And Archaeal Communities ◽  
Different Depths ◽  
Archaeal Communities

Understanding the composition and diversity of soil microorganisms that typically mediate the soil biogeochemical cycle is crucial for estimating greenhouse gas flux and mitigating global changes in plantation forests. Therefore, the objectives of this study were to investigate changes in diversity and relative abundance of bacteria and archaea with soil profiles and the potential factors influencing the vertical differentiation of microbial communities in a poplar plantation. We investigated soil bacterial and archaeal community compositions and diversities by 16S rRNA gene Illumina MiSeq sequencing at different depths of a poplar plantation forest in Chenwei forest farm, Sihong County, Jiangsu, China. More than 882,422 quality-filtered 16S rRNA gene sequences were obtained from 15 samples, corresponding to 34 classified phyla and 68 known classes. Ten major bacterial phyla and two archaeal phyla were found. The diversity of bacterial and archaeal communities decreased with depth of the plantation soil. Analysis of variance (ANOVA) of relative abundance of microbial communities exhibited that Nitrospirae, Verrucomicrobia, Latescibacteria, GAL15, SBR1093, and Euryarchaeota had significant differences at different depths. The transition zone of the community composition between the surface and subsurface occurred at 10–20 cm. Overall, our findings highlighted the importance of depth with regard to the complexity and diversity of microbial community composition in plantation forest soils.

Impact of a probiotic, inulin, or their combination on the piglets’ microbiota at different intestinal locations

2015 ◽  
Vol 6 (4) ◽  
pp. 473-483 ◽  
Author(s):  
V.A. Sattler ◽  
K. Bayer ◽  
G. Schatzmayr ◽  
A.G. Haslberger ◽  
V. Klose
Keyword(s):  
16S Rrna ◽  
Gut Microbiota ◽  
16S Rrna Gene ◽  
Real Time ◽  
Relative Abundance ◽  
Real Time Pcr ◽  
Denaturing Gradient Gel Electrophoresis ◽  
Feed Additives ◽  
Rrna Gene ◽  
16S Rrna Gene Pyrosequencing

Natural feed additives are used to maintain health and to promote performance of pigs without antibiotics. Effects of a probiotic, inulin, and their combination (synbiotic), on the microbial diversity and composition at different intestinal locations were analysed using denaturing gradient gel electrophoresis (DGGE), real-time PCR, and 16S rRNA gene pyrosequencing. Bacterial diversity assessed by DGGE and/or pyrosequencing was increased by inulin in all three gut locations and by the synbiotic in the caecum and colon. In contrast, the probiotic did only affect the microbiota diversity in the ileum. Shifts in the DGGE microbiota profiles of the caecum and colon were detected for the pro- and synbiotic fed animals, whereas inulin profiles were more similar to the ones of the control. 16S rRNA gene pyrosequencing revealed that all three additives could reduce Escherichia species in each gut location, indicating a potential beneficial effect on the gut microbiota. An increase of relative abundance of Clostridiaceae in the large intestine was found in the inulin group and of Enterococcaceae in the ileum of probiotic fed pigs. Furthermore, real-time PCR results showed that the probiotic and synbiotic increased bifidobacterial numbers in the ileum, which was supported by sequencing results. The probiotic and inulin, to different extents, changed the diversity, relative abundance of phylotypes, and community profiles of the porcine microbiota. However, alterations of the bacterial community were not uniformly between gut locations, demonstrating that functionality of feed additives is site specific. Therefore, gut sampling from various locations is crucial when investigations aim to identify the composition of a healthy gut microbiota after its manipulation through feed additives.

scholarly journals Complementing 16S rRNA Gene Amplicon Sequencing with Total Bacterial Load To Infer Absolute Species Concentrations in the Vaginal Microbiome

mSystems ◽  
2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Florencia A. Tettamanti Boshier ◽  
Sujatha Srinivasan ◽  
Anthony Lopez ◽  
Noah G. Hoffman ◽  
Sean Proll ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Relative Abundance ◽  
Bacterial Species ◽  
Bacterial Load ◽  
Amplicon Sequencing ◽  
Individual Species ◽  
Rrna Gene ◽  
Vaginal Microbiome ◽  
Bacterial Concentrations

ABSTRACT Whereas 16S rRNA gene amplicon sequencing quantifies relative abundances of bacterial taxa, variation in total bacterial load between samples restricts its ability to reflect absolute concentrations of individual bacterial species. Quantitative PCR (qPCR) can quantify individual species, but it is not practical to develop a suite of qPCR assays for every bacterium present in a diverse sample. We sought to determine the accuracy of an inferred measure of bacterial concentration using total bacterial load and relative abundance. We analyzed 1,320 samples from 20 women with a history of frequent bacterial vaginosis who self-collected vaginal swabs daily over 60 days. We inferred bacterial concentrations by taking the product of species relative abundance (assessed by 16S rRNA gene amplicon sequencing) and bacterial load (measured by broad-range 16S rRNA gene qPCR). Log10-converted inferred concentrations correlated with targeted qPCR (r = 0. 935, P < 2.2e–16) for seven key bacterial species. The mean inferred concentration error varied across bacteria, with rarer bacteria associated with larger errors. A total of 92% of the >0.5-log10 errors occurred when the relative abundance was <10%. Many errors occurred during early bacterial expansion from or late contraction to low abundance. When the relative abundance of a species is >10%, inferred concentrations are reliable proxies for targeted qPCR in the vaginal microbiome. However, targeted qPCR is required to capture bacteria at low relative abundance and is preferable for characterizing growth and decay kinetics of single species. IMPORTANCE Microbiome studies primarily use 16S rRNA gene amplicon sequencing to assess the relative abundance of bacterial taxa in a community. However, these measurements do not accurately reflect absolute taxon concentrations. We sought to determine whether the product of species’ relative abundance and total bacterial load measured by broad-range qPCR is an accurate proxy for individual species’ concentrations, as measured by taxon-specific qPCR assays. Overall, the inferred bacterial concentrations were a reasonable proxy of species-specific qPCR values, particularly when bacteria are present at a higher relative abundance. This approach offers an opportunity to assess the concentrations of bacterial species and how they change in a community over time without developing individual qPCR assays for each taxon.

scholarly journals Corn oil supplementation enhances hydrogen use for biohydrogenation, inhibits methanogenesis, and alters fermentation pathways and the microbial community in the rumen of goats

2019 ◽  
Vol 97 (12) ◽  
pp. 4999-5008 ◽  
Author(s):  
Xiu Min Zhang ◽  
Rodolfo F Medrano ◽  
Min Wang ◽  
Karen A Beauchemin ◽  
Zhi Yuan Ma ◽  
...  
Keyword(s):  
Fatty Acids ◽  
16S Rrna ◽  
16S Rrna Gene ◽  
Relative Abundance ◽  
Unsaturated Fatty Acids ◽  
Corn Oil ◽  
Nutrient Digestibility ◽  
Rrna Gene ◽  
Ch4 Emissions ◽  
Gene Copies

Abstract Enteric methane (CH4) emissions are not only an important source of greenhouse gases but also a loss of dietary energy in livestock. Corn oil (CO) is rich in unsaturated fatty acid with &gt;50% PUFA, which may enhance ruminal biohydrogenation of unsaturated fatty acids, leading to changes in ruminal H2 metabolism and methanogenesis. The objective of this study was to investigate the effect of CO supplementation of a diet on CH4 emissions, nutrient digestibility, ruminal dissolved gases, fermentation, and microbiota in goats. Six female goats were used in a crossover design with two dietary treatments, which included control and CO supplementation (30 g/kg DM basis). CO supplementation did not alter total-tract organic matter digestibility or populations of predominant ruminal fibrolytic microorganisms (protozoa, fungi, Ruminococcus albus, Ruminococcus flavefaciens, and Fibrobacter succinogenes), but reduced enteric CH4 emissions (g/kg DMI, −15.1%, P = 0.003). CO supplementation decreased ruminal dissolved hydrogen (dH2, P &lt; 0.001) and dissolved CH4 (P &lt; 0.001) concentrations, proportions of total unsaturated fatty acids (P &lt; 0.001) and propionate (P = 0.015), and increased proportions of total SFAs (P &lt; 0.001) and acetate (P &lt; 0.001), and acetate to propionate ratio (P = 0.038) in rumen fluid. CO supplementation decreased relative abundance of family Bacteroidales_BS11_gut_group (P = 0.032), increased relative abundance of family Rikenellaceae (P = 0.021) and Lachnospiraceae (P = 0.025), and tended to increase relative abundance of genus Butyrivibrio_2 (P = 0.06). Relative abundance (P = 0.09) and 16S rRNA gene copies (P = 0.043) of order Methanomicrobiales, and relative abundance of genus Methanomicrobium (P = 0.09) also decreased with CO supplementation, but relative abundance (P = 0.012) and 16S rRNA gene copies (P = 0.08) of genus Methanobrevibacter increased. In summary, CO supplementation increased rumen biohydrogenatation by facilitating growth of biohydrogenating bacteria of family Lachnospiraceae and genus Butyrivibrio_2 and may have enhanced reductive acetogenesis by facilitating growth of family Lachnospiraceae. In conclusion, dietary supplementation of CO led to a shift of fermentation pathways that enhanced acetate production and decreased rumen dH2 concentration and CH4 emissions.

scholarly journals Handling of Spurious Sequences Affects the Outcome of High-Throughput 16S rRNA Gene Amplicon Profiling

2020 ◽  
Author(s):  
Thomas Clavel ◽  
Sandra Reitmeier ◽  
Thomas CA Hitch ◽  
Nicole Treichel ◽  
Nikolaos Fikas ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Data Processing ◽  
Relative Abundance ◽  
Large Scale ◽  
Peat Soil ◽  
Rrna Gene ◽  
Dnase Treatment

Abstract Background: 16S rRNA gene amplicon sequencing is a very popular approach for studying microbiomes. However, varying standards exist for sample and data processing and some basic concepts, such as the occurrence of spurious sequences, have not been investigated in a comprehensive manner. Methods: Using defined communities of bacteria in vitro and in vivo, we searched for sequences not matching the expected species (i.e., spurious taxa) and determined a minimum threshold of occurrence suitable for robust data analysis. The presence and origin of spurious taxa were investigated via large-scale amplicon queries and gut samples from germfree mice spiked with target mock DNA. We also assessed the effect of varying sequence-filtering stringency on diversity readouts in human fecal and peat soil communities. Our findings are based on data generated in three sequencing facilities and analyzed via both operational taxonomic units (OTUs) and amplicon sequence variants (ASVs) approaches.Results: 16S rRNA gene amplicon data-processing based on OTUs clustering and singleton removal, a commonly used approach that discards any taxa represented by only one sequence across all samples, delivered an average approximately 50% (mock communities) to 80% (gnotobiotic mice) spurious taxa. The fraction of spurious taxa was generally lower based on ASV analysis, but varied depending on the gene region targeted and the barcoding system used. A relative abundance of 0.25% was found as an effective threshold below which the analysis of spurious taxa can be prevented to a large extent in both OTU- and ASV-based analysis approaches. Most spurious taxa (approx. 70%) detected in simplified communities occurred in samples multiplexed in the same sequencing run and were present in only one of ten runs. DNase treatment of gut content from germfree mice partly helped to exclude spurious taxa from the analysis of spiked mock DNA, but was not necessary when applying the 0.25% relative abundance threshold. Using this cut-off improved the reproducibility of analysis, i.e., specifically by reducing variation in richness estimates by 38% compared with singleton filtering in a benchmarking experiment using six human fecal samples across seven sequencing runs. Beta-diversity analyses of human fecal communities was markedly affected by both the filtering strategy and the type of phylogenetic distances used for comparing samples, highlighting the importance of carefully analyzing data before drawing conclusions. Conclusions: Handling of artifact sequences during bioinformatic processing of 16S rRNA gene amplicon data requires careful attention to avoid the generation of misleading findings. Applying a minimum relative abundance threshold between 0.10 and 0.30% is superior to the singleton removal approach, although study-specific analysis strategies may be needed depending on, for instance, the type of samples analyzed and the sequencing depth achieved. Additionally, we propose the concept of effective richness to facilitate the comparison of results across studies.

scholarly journals Structure, diversity and potential metabolic activity of prokaryotic communities of Ebro Delta wetlands (Spain) as revealed by 16S rRNA gene amplicon sequencing

2021 ◽  
Vol 4 ◽  
Author(s):  
Javier Miralles-Lorenzo ◽  
Antonio Picazo ◽  
Carlos Rochera ◽  
Daniel Morant ◽  
Antonio Camacho
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Sulfate Reduction ◽  
Relative Abundance ◽  
Methanogenic Archaea ◽  
Methane Emissions ◽  
Rrna Gene ◽  
Saline Wetlands ◽  
Potential Activity ◽  
The Relationship

The monitoring of the structure and potential function of the prokaryotic assemblages of aquatic ecosystems can be used for the assessment of ecosystem health. In this work, we analysed by 16S rRNA gene amplicon massive sequencing the aquatic and sediment prokaryotic communities inhabiting three wetlands located in Ebro river Delta (Spain), which differ in their salinity and trophic status. We extracted the DNA from both matrices and sequenced the V4 region of the prokaryotic 16S rRNA gene by Illumina sequencing. The raw sequences obtained were processed and clustered in ZOTUs, which are sequences at 100% identity that were the basis for the structural and statistical analyses. Our results showed that water communities have less diversity and evenness than sediment communities. Moreover, statistical analyses showed that salinity is the main environmental factor that affects the structuration of sediment prokaryotic communities, while seasonality is also a very additional important environmental driver for aquatic communities. We also studied the relationship between the environmental factors and the potential metabolism of the aquatic and sediment prokaryotic communities, specifically for the main metabolic processes of the C-cycle. Focusing on sediment, we observed that methanogenic archaea are present not only in freshwater environments but also in the saline wetlands, though the observed methane emissions decreased with salinity. To explain this, we studied the potential activity of sulfate-reducing bacteria (SRB) and methanogenic archaea inferring the expression of genes dsrB and mcrA, which are gene markers for dissimilatory sulfate reduction and methanogenesis, respectively. We observed that, in saline wetlands, the potential activity of methanogens decreases because SRB bacteria outcompete them due to the higher sulfate availability enhancing sulfate-reduction. In the sediment communities of low salinity wetlands the relevance of methanogens is lower in terms of relative abundance, but the methane emissions are higher due to the lower sulfate availability. On the other hand, aquatic methanotrophic bacteria are very important in the net balance of methane emissions in Ebro Delta wetlands, as their relative abundance in the water column influences the amount of methane that is finally released to the atmosphere. In conclusion, our study deepens in the relationship between prokaryotic community structure and function in deltaic wetlands, giving a comprehensive overview of factors influencing the ecological health and certain processes, such as methane emissions, in deltaic systems.

scholarly journals Re-evaluating the salty divide: phylogenetic specificity of transitions between marine and freshwater systems

2018 ◽  
Author(s):  
Sara F. Paver ◽  
Daniel J. Muratore ◽  
Ryan J. Newton ◽  
Maureen L. Coleman
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Microbial Communities ◽  
Relative Abundance ◽  
Environmental Changes ◽  
Habitat Type ◽  
Freshwater Ecosystems ◽  
Rrna Gene ◽  
Minimum Entropy ◽  
Habitat Types

AbstractMarine and freshwater microbial communities are phylogenetically distinct and transitions between habitat types are thought to be infrequent. We compared the phylogenetic diversity of marine and freshwater microorganisms and identified specific lineages exhibiting notably high or low similarity between marine and freshwater ecosystems using a meta-analysis of 16S rRNA gene tag-sequencing datasets. As expected, marine and freshwater microbial communities differed in the relative abundance of major phyla and contained habitat-specific lineages; at the same time, however, many shared taxa were observed in both environments. Betaproteobacteria and Alphaproteobacteria sequences had the highest similarity between marine and freshwater sample pairs. Gammaproteobacteria and Alphaproteobacteria contained the highest number of Minimum Entropy Decomposition nodes shared by marine and freshwater samples. Shared nodes included lineages of the abundant alphaproteobacterial group SAR11 that have not previously been reported in 16S rRNA gene surveys of freshwater lakes. Our results suggest that shared taxa are numerous, but tend to occur sporadically and at low relative abundance in one habitat type, leading to an underestimation of transition frequency between marine and freshwater habitats. Lineages with a high degree of shared taxa or habitat-specific diversification represent targets for genome-scale investigations into microbial adaptations and evolutionary innovations. Rare taxa with abundances near or below detection, including lineages that appear to have crossed the salty divide relatively recently, may have novel adaptations enabling them to exploit opportunities for niche expansion when environments are disturbed or conditions change.ImportanceThe distribution of microbial diversity across environments yields insight into processes that create and maintain this diversity as well as potential to infer how communities will respond to future environmental changes. We integrated datasets from dozens of freshwater lake and marine samples to compare diversity across open water habitats differing in salinity. Our novel combination of sequence-based approaches revealed phyla and proteobacterial classes inferred to include more or less recent transitions across habitat types as well as specific lineages that are shared by marine and freshwater environments at the level of 16S rRNA sequence types. Our findings contribute to understanding the ecological and evolutionary controls on microbial distributions, and open up new questions regarding the plasticity and adaptability of particular lineages.

scholarly journals Complementing 16S rRNA gene amplicon sequencing with estimates of total bacterial load to infer absolute species concentrations in the vaginal microbiome

2019 ◽  
Author(s):  
Florencia Tettamanti Boshier ◽  
Sujatha Srinivasan ◽  
Anthony Lopez ◽  
Noah G. Hoffman ◽  
Sean Proll ◽  
...  
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Bacterial Vaginosis ◽  
Relative Abundance ◽  
Bacterial Species ◽  
Bacterial Load ◽  
Amplicon Sequencing ◽  
Individual Species ◽  
Rrna Gene ◽  
Associated Bacteria

Whereas 16S rRNA gene amplicon sequencing quantifies relative abundances of bacterial taxa, variation in total bacterial load between samples restricts its ability to reflect absolute concentration of individual species. Quantitative PCR (qPCR) can quantify individual species, but it is not practical to develop a suite of qPCR assays for every bacterium present in a diverse sample. We analyzed 1320 samples from 20 women with a history of frequent bacterial vaginosis, who self-collected vaginal swabs daily over 60 days. We inferred bacterial concentrations by taking the product of species relative abundance (assessed by 16S rRNA gene amplicon sequencing) and total bacterial load (measured by broad-range 16S rRNA gene qPCR). Log10-converted inferred concentrations correlated with targeted qPCR (r = 0. 935, p<2.2e-16) for seven key bacterial species. The mean inferred concentration error varied across bacteria, with rarer bacterial vaginosis-associated bacteria associated with larger errors. 92% of errors >0.5 log10 occurred when relative abundance was <10%. Many errors occurred during early bacterial expansion or late contraction. When relative abundance of a species is >10%, inferred concentrations are reliable proxies for targeted qPCR. However, targeted qPCR is required to capture bacteria at low relative abundance, particularly with BV-associated bacteria during the early onset of bacterial vaginosis.

Detection of Methanogens in Anaerobic Granular Sludge by FISH Targeting for Functional Genes

2012 ◽  
Vol 518-523 ◽  
pp. 299-304 ◽  
Author(s):  
Run Zhang ◽  
Chun Liu ◽  
Liang Li ◽  
Hui Na Yang ◽  
Jing Liang Yang
Keyword(s):  
16S Rrna ◽  
16S Rrna Gene ◽  
Relative Abundance ◽  
Granular Sludge ◽  
Functional Gene ◽  
Rrna Gene ◽  
Fish Analysis ◽  
Anaerobic Granular Sludge ◽  
Sludge Sample ◽  
Starch Wastewater

Methanogens play an important role in the anaerobic digestion and production of methane, and show significant influence on the performance of anaerobic wastewater treatment process. Then the methanogens in anaerobic granular sludge samples from full-scale UASB bioreactors treating avermectin or starch wastewater were detected by FISH using 16S rRNA gene-based probe and functional gene-based probes. The results showed that the hybridization of methanogens in simultaneous FISH with mcrA gene-based and 16S rRNA gene-based probes was high coincident and the coincidence degree was about 60%-80%, implying the preferable hybridization consistency between functional gene-based probe and 16S rRNA gene-based probe. The relative abundance of methanogens obtained in FISH analysis using 16S rRNA gene-based probe seemed higher than that using functional gene-based probes, indicating that functional gene could provide more specific detection of methanogens than 16S rRNA gene probably. For functional gene-based probes, the methanogen-specificity was in the following order: mcrA＜F420＜mtr. During the development process of both granular sludge samples, the maximum relative abundance of methanogens was obtained at its mature phase using all probes. The relative abundance of methanogens in the sludge sample treating avermectin wastewater was lower than that treating starch wastewater, indicating smaller methanogenic population in the sludge sample treating avermectin wastewater due to inhibitory effect of antibiotic residue on methanogens probably.

scholarly journals Different analysis strategies of 16S rRNA gene data from rodent studies generate contrasting views of gut bacterial communities associated with diet, health and obesity

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10372
Author(s):  
Jose F. Garcia-Mazcorro ◽  
Jorge R. Kawas ◽  
Cuauhtemoc Licona Cassani ◽  
Susanne Mertens-Talcott ◽  
Giuliana Noratto
Keyword(s):  
16S Rrna ◽  
Gut Microbiota ◽  
16S Rrna Gene ◽  
Relative Abundance ◽  
Bacterial Communities ◽  
Future Research ◽  
Rrna Gene ◽  
Microbial Composition ◽  
Analysis Strategies ◽  
The Impact

Background One of the main functions of diet is to nurture the gut microbiota and this relationship affects the health of the host. However, different analysis strategies can generate different views on the relative abundance of each microbial taxon, which can affect our conclusions about the significance of diet to gut health in lean and obese subjects. Here we explored the impact of using different analysis strategies to study the gut microbiota in a context of diet, health and obesity. Methods Over 15 million 16S rRNA gene sequences from published studies involving dietary interventions in obese laboratory rodents were analyzed. Three strategies were used to assign the 16S sequences to Operational Taxonomic Units (OTUs) based on the GreenGenes reference OTU sequence files clustered at 97% and 99% similarity. Results Different strategies to select OTUs influenced the relative abundance of all bacterial taxa, but the magnitude of this phenomenon showed a strong study effect. Different taxa showed up to 20% difference in relative abundance within the same study, depending on the analysis strategy. Very few OTUs were shared among the samples. ANOSIM test on unweighted UniFrac distances showed that study, sequencing technique, animal model, and dietary treatment (in that order) were the most important factors explaining the differences in bacterial communities. Except for obesity status, the contribution of diet and other factors to explain the variability in bacterial communities was lower when using weighted UniFrac distances. Predicted functional profile and high-level phenotypes of the microbiota showed that each study was associated with unique features and patterns. Conclusions The results confirm previous findings showing a strong study effect on gut microbial composition and raise concerns about the impact of analysis strategies on the membership and composition of the gut microbiota. This study may be helpful to guide future research aiming to investigate the relationship between diet, health, and the gut microbiota.

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