Ferriphaselus amnicola strain GF-20, a new iron- and thiosulfate-oxidizing bacterium isolated from a hard rock aquifer

Ferriphaselus amnicola GF-20 is the first Fe-oxidizing bacterium isolated from the continental subsurface. It was isolated from groundwater circulating at 20 m depth in the fractured-rock catchment observatory of Guidel-Ploemeur (France). Strain GF-20 is a neutrophilic, iron- and thiosulfate-oxidizer and grows autotrophically. The strain shows a preference for low oxygen concentrations, which suggests an adaptation to the limiting oxygen conditions of the subsurface. It produces extracellular stalks and dreads when grown with Fe(II) but does not secrete any structure when grown with thiosulfate. Phylogenetic analyses and genome comparisons revealed that strain GF-20 is affiliated with the species F. amnicola and is strikingly similar to F. amnicola strain OYT1, which was isolated from a groundwater seep in Japan. Based on the phenotypic and phylogenetic characteristics, we propose that GF-20 represents a new strain within the species F. amnicola.

Parabacteroides faecalis sp. nov. Isolated from Swine Faeces

A Gram-negative, obligate anaerobic, non-motile, non-spore-forming, rod-shaped bacterial strain designated AGMB00274^T was isolated from swine faeces. An 16S rRNA gene analysis indicated that strain AGMB00274^T belonged to the genus Parabacteroides, with the highest similarity to Parabacteroides johnsonii (P. johnsonii) DSM 18315^T (sequence similarity of 94.9%). The genome size of strain AGMB00274^T was 4,308,683 bp, with a DNA G+C content of 42.5 mol%. The biochemical analysis of strain AGMB00274^T showed that it was positive for gelatin hydrolysis and α-fucosidase, but negative for the acid production from D-glucose, D-mannitol, D-maltose, salicin, glycerol, D-cellobiose, D-mannose, D-melezitose, D-sorbitol, D-trehalose, and negative for α-arabinosidase, glutamic acid decarboxylase, and pyroglutamic acid arylamidase. The dominant cellular fatty acids (> 10%) of the isolate were anteiso-C_{15: 0} (23.2%), iso-C_{15: 0} (16.6%), C_{18: 1} ω9c (16.4%), summed feature 11 (iso-C_{17: 0} 3-OH and/or C_{18: 2} DMA) (12.5%), and C_{16: 0} (11.3%). The major respiratory quinones of strain AGMB00274^T were MK-9 (55.4%) and MK-10 (44.6%). The major polar lipid was phosphatidylethanolamine. Based on phylogenetic, genetic, physiological, and chemotaxonomic analyses, as a novel species of the genus Parabacteroides, strain AGMB00274^T was proposed with the name Parabacteroides faecalis sp. nov. The type strain used was AGMB00274^T (= KCTC 25286^T = GDMCC 1.2742^T).

Gut Microbiota Serves a Predictable Outcome of Short-Term Low-Carbohydrate Diet (LCD) Intervention for Patients with Obesity

To date, much progress has been made in dietary therapy for obese patients. A low-carbohydrate diet (LCD) has reached a revival in its clinical use during the past decade with undefined mechanisms and debatable efficacy. The gut microbiota has been suggested to promote energy harvesting. Here, we propose that the gut microbiota contributes to the inconsistent outcome under an LCD. To test this hypothesis, patients with obesity or patients who were overweight were randomly assigned to a normal diet (ND) or an LCD group with ad libitum energy intake for 12 weeks. Using matched sampling, the microbiome profile at baseline and end stage was examined. The relative abundance of butyrate-producing bacteria, including Porphyromonadaceae Parabacteroides and Ruminococcaceae Oscillospira, was markedly increased after LCD intervention for 12 weeks. Moreover, within the LCD group, participants with a higher relative abundance of Bacteroidaceae Bacteroides at baseline exhibited a better response to LCD intervention and achieved greater weight loss outcomes. Nevertheless, the adoption of an artificial neural network (ANN)-based prediction model greatly surpasses a general linear model in predicting weight loss outcomes after LCD intervention. Therefore, the gut microbiota served as a positive outcome predictor and has the potential to predict weight loss outcomes after short-term LCD intervention. Gut microbiota may help to guide the clinical application of short-term LCD intervention to develop effective weight loss strategies. (This study has been registered at the China Clinical Trial Registry under approval no. ChiCTR1800015156). IMPORTANCE Obesity and its related complications pose a serious threat to human health. Short-term low-carbohydrate diet (LCD) intervention without calorie restriction has a significant weight loss effect for overweight/obese people. Furthermore, the relative abundance of Bacteroidaceae Bacteroides is a positive outcome predictor of individual weight loss after short-term LCD intervention. Moreover, leveraging on these distinct gut microbial structures at baseline, we have established a prediction model based on the artificial neural network (ANN) algorithm that could be used to estimate weight loss potential before each clinical trial (with Chinese patent number 2021104655623). This will help to guide the clinical application of short-term LCD intervention to improve weight loss strategies.

Pontibacter flavimaris sp. nov., of the family Hymenobacteraceae, isolated from marine sediment

A Gram-stain-negative, ovoid or rod-shaped, non-flagellated, motile-by-gliding and aerobic bacteria, designated S10-8^T, was isolated from marine sediment of the Yellow Sea. Colonies of strain S10-8^T had a pink-red pigmentation and its cells were approximately 0.5-0.8 μm×1.0-2.5 μm in size. Growth occurred at 10-45 °C (optimally at 33-37 °C), in the presence of 0-12.0 % NaCl (optimally at 2.0-5.0 %, w/v) and at pH 5.0-8.5 (optimally at pH 7.0-7.5). Phylogenetic analysis of the 16S rRNA gene indicated that strain S10-8^T is a member of the genus Pontibacter within the family Hymenobacteraceae, and the 16S rRNA gene sequence similarity of strain S10-8^T to its closest relative Pontibacter actiniarum KCTC 12367^T was 96.9 %. Strain S10-8^T contained MK-7 as the predominant menaquinone and summed feature 4 (iso-C_17:1 I and/or anteiso-C_17:1 B) and iso-C_15:0 as the major fatty acids. The major polar lipids were phosphatidylethanolamine, an unidentified aminophospholipid and an unidentified lipid. The size of the draft genome was 4 623 791 bp and the G+C content was 53.5 mol%. There were low DNA-DNA hybridization values (<48.3±5.2 %) and average nucleotide identity values (<86.5 %) between strain S10-8^T and the most closely related recognized Pontibacter species. Therefore, we propose a novel species in the genus Pontibacter to accommodate the novel isolate: Pontibacter flavimaris sp. nov. (type strain S10-8^T=KCTC 42769^T=ACCC 19859^T).

Patterns of the fecal microbiota in the Juan Fernández fur seal (Arctocephalus philippii)

As apex predators, pinnipeds are considered to be useful bioindicators of marine and coastal environments. Endemic to a small archipelago in the South Pacific, the Juan Fernandez fur seal (JFFS) is one of the less-studied members of the pinniped family Otariidae. This study aimed to characterize the fecal microbiome of the JFFS for the first time, to establish a baseline for future studies of host-microbial-environment interactions and monitoring programs. During two consecutive reproductive seasons, 57 fecal samples were collected from seven different JFFS colonies within the Juan Fernandez Archipelago, Chile. Bacterial composition and abundance were characterized by sequencing the V4 region of the 16S rRNA gene. The overall microbiome composition was dominated by five phyla: Firmicutes (40% ±24), Fusobacteria (30% ±17), Bacteroidetes (22% ±10), Proteobacteria (6% ±4), and Actinobacteria (2% ±3). Alpha diversity was higher in Tierras Blancas. However, location was not found to be a dominant driver of microbial composition. Interestingly, the strongest signal in the data was a negative association between the genera Peptoclostridium and Fusobacterium, which explained 29.7% of the total microbial composition variability between samples. The genus Peptoclostridium has not been reported in other pinniped studies, and its role here is unclear, with interpretation challenging due to a lack of information regarding microbiome functionality in marine mammals. As a first insight into the JFFS fecal microbiome, these results contribute towards our understanding of the natural microbial diversity and composition in free-ranging pinnipeds.

mbImpute: an accurate and robust imputation method for microbiome data

A critical challenge in microbiome data analysis is the existence of many non-biological zeros, which distort taxon abundance distributions, complicate data analysis, and jeopardize the reliability of scientific discoveries. To address this issue, we propose the first imputation method for microbiome data-mbImpute-to identify and recover likely non-biological zeros by borrowing information jointly from similar samples, similar taxa, and optional metadata including sample covariates and taxon phylogeny. We demonstrate that mbImpute improves the power of identifying disease-related taxa from microbiome data of type 2 diabetes and colorectal cancer, and mbImpute preserves non-zero distributions of taxa abundances.

Pseudoprevotella muciniphila gen. nov., sp. nov., a mucin-degrading bacterium attached to the bovine rumen epithelium

A Gram-negative, strictly anaerobic mucin-degrading bacterium, which we designated strain E39^T, was isolated from the rumen epithelium of Korean cattle. The cells were non-motile and had a coccus morphology. Growth of strain E39^T was observed at 30–45°C (optimum, 39°C), pH 6.5–8.5 (optimum, pH 7.5), and in the presence of 0.0–1.0% (w/v) NaCl (optimum, 0.0–0.5%). Strain E39^T contained C_16:0, C_18:0, C_18:1ω9c, iso-C_15:0, and anteiso-C_15:0 as the major fatty acids. The major polar lipids were phosphatidylethanolamine, unidentified aminophospholipid, and unidentified lipids. The major respiratory isoprenoid quinones were MK-8 and MK-9. The major fermented end-products of mucin were acetate and succinate. The G+C content of the genomic DNA was 46.4 mol%. Strain E39^T was most closely related to Alloprevotella rava 81/4-12^T with an 87.3% 16S rRNA gene sequence similarity. On the basis of phenotypic, chemotaxonomic, and molecular properties, strain E39^T represents a novel genus of the family Prevotellaceae; as such, the name Pseudoprevotella muciniphila gen. nov., sp. nov. is proposed. A functional annotation of the whole genome sequences of P. muciniphila E39^T revealed that this bacterium has a putative mucin-degrading pathway and biosynthetic pathways of extracellular polymeric substances and virulence factors which enable bacteria to adhere to the epithelial cells and avoid the host’s immune responses.

Effect of Trilobatin from Lithocarpus polystachyus Rehd on Gut Microbiota of Obese Rats Induced by a High-Fat Diet

Trilobatin was identified as the primary bioactive component in the Lithocarpus polystachyus Rehd (LPR) leaves. This study explored the antiobesity effect of trilobatin from LPR leaves and its influence on gut microbiota in obese rats. Results showed that trilobatin could significantly reduce body and liver weight gain induced by a high-fat diet, and the accumulation of perirenal fat, epididymal fat, and brown fat of SD (Male Sprague–Dawley) obese rats in a dose-independent manner. Short-chain fatty acids (SCFAs) concentrations increased, especially the concentration of butyrate. Trilobatin supplementation could significantly increase the relative abundance of Lactobacillus, Prevotella, CF231, Bacteroides, and Oscillospira, and decrease greatly the abundance of Blautia, Allobaculum, Phascolarctobacterium, and Coprococcus, resulting in an increase of the ratio of Bacteroidetes to Firmicutes (except the genera of Lactobacillus and Oscillospira). The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway predicted by the Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) indicated the different relative metabolic pathways after trilobatin supplementation. This study may reveal the contribution of gut microbiota to the antiobesity effect of trilobatin from LPR leaves and predict the potential regulatory mechanism for obesity induced by a high-fat diet.

Foetidibacter luteolus gen. nov., sp. nov., isolated from the rhizosphere of Salvia miltiorrhiza

A polyphosphate-producing bacterium, YG09^T, was isolated from the rhizosphere of Salvia miltiorrhiza. Its colonies were 2.0-3.0 mm in diameter, smooth, circular, convex and yellow after growth on R2A at 28 °C for 72 h, with aerobic, Gram-stain-negative, non-motile and rod-shaped bacteria. The strain was found to grow at 10-40 °C (optimum 37 °C), pH 5.5-8.0 (optimum 6.0), with 0-0.6% (w/v) NaCl (optimum 0). Chemotaxonomic analysis showed menaquinone-7 as the only quinone present; C15: 1 iso G, C15: 1 iso, C16: 0, C16: 0 3OH, C17: 0 iso 3OH, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) as the major fatty acids (> 5%), and phosphatidylethanolamine, three unidentified phospholipids, four unidentified polar lipids, three unidentified aminolipids, and one unidentified amino phospholipid as the polar lipids. The DNA G + C content was 44.6 mol%. The 16S rRNA gene sequences of the isolate showed highest similarities to Panacibacter ginsenosidivorans Gsoil 1550^T (93.6%), Filimonas endophytica SR2-06^T (93.4%), Parasegetibacter terrae SGM2-10^T (92.8%), and Arvibacter flaviflagrans C-1-16^T (92.7%), within the family Chitinophagaceae of the phylum Bacteroidetes. The ANI values between strain YG09^T and Panacibacter ginsenosidivoran Gsoil 1550^T, Filimonas endophytica SR2-06^T and Filimonas lacunae YT21^T were 69.4, 68.3 and 68.7%, respectively. Based on phenotypic, genotypic and phylogenetic analyses, strain YG09^T represents a novel genus in the family Chitinophagaceae, for which the name Foetidibacter luteolus gen. sp. nov. is proposed. The type strain is Foetidibacter luteolus YG09^T (= MCCC 1K04042^T = KCTC 72595^T).

Structural rearrangement of native and processed pea starches following simulated digestion in vitro and fermentation characteristics of their resistant starch residues using human fecal inoculum

Pea starches, in both native (NPS) and retrograded-autoclaved forms (RAPS), were subjected to simulated gastrointestinal (GI) digestion in vitro, their multi-scale structural characteristics, morphological features, molecular distribution and thermal properties were characterized. A gradual increase in the short-/long-range crystallinity, melting enthalpy of gelatinization on increasing digestion time was observed for both the native and retrograded-autoclaved pea starch samples based on the X-ray diffraction, Fourier-transform infrared spectra, solid-state 13CNMR and differential scanning calorimetry measurements. It was especially noticed that the growth rate of crystallinity and double helices, as well as the decrease in Mw values were evidently greater for RAPS than for NPS. To investigate how different molecular fine structure of pea starch substrate affects the gut microbiota shifts and dynamic short-chain fatty acid profile, their resistant starch residues obtained from both native and retrograded-autoclaved pea starch after 8 h of simulated GI tract digestion was used as the fermentation substrate. The levels of acetate, propionate and butyrate gradually increased with the increasing fermentation time for NPS and RAPS. In comparison to the blank control (i.e., the group without the addition of carbohydrate), the fermented NPS and RAPS obviously resulted in an increased abundance of Firmicutes and Bacteroidetes, accompanied by a decrease in Proteobacteria, Actinobacteria and Verrucomicrobia. Both NPS and RAPS promoted different shifts in the microbial community at the genus level, with an increase in the abundance of Bacteroides, Megamonas and Bifidobacterium, as well as a reduction in the abundance of Fusobacterium, Faecalibacterium and Lachnoclostridium in comparison to the blank control samples.

Short-Term Exposure to High-Temperature Water Causes a Shift in the Microbiome of the Common Aquarium Sponge Lendenfeldia chondrodes

Marine sponges harbor diverse microbiomes that contribute to their energetic and metabolic needs. Although numerous studies on sponge microbial diversity exist, relatively few focused on sponge microbial community changes under different sources of environmental stress. In this study, we assess the impact of elevated seawater temperature on the microbiome of cultured Lendenfeldia chondrodes, a coral reef sponge commonly found in marine aquaria. Lendenfeldia chondrodes exhibits high thermal tolerance showing no evidence of tissue damage or bleaching at 5 °C above control water temperature (26 °C). High-throughput sequencing of the bacterial 16S rRNA V4 region revealed a response of the microbiome of L. chondrodes to short-term exposure to elevated seawater temperature. Shifts in abundance and richness of the dominant bacterial phyla found in the microbiome of this species, namely Proteobacteria, Cyanobacteria, Planctomycetes, and Bacteroidetes, characterized this response. The observed resilience of L. chondrodes and the responsiveness of its microbiome to short-term increases in seawater temperature suggest that this holobiont may be capable of acclimating to anthropogenic-driven sublethal environmental stress via a re-accommodation of its associated bacterial community. This sheds a new light on the potential for resilience of some sponges to increasing surface seawater temperatures and associated projected regime shifts in coral reefs.

Composition of the North American Wood Frog (Rana sylvatica) Bacterial Skin Microbiome and Seasonal Variation in Community Structure

While a number of amphibian skin microbiomes have been characterized, it is unclear how these communities might vary in response to seasonal changes in the environment and the corresponding behaviors that many amphibians exhibit. Given recent studies demonstrating the importance of the skin microbiome in frog innate immune defense against pathogens, investigating how changes in the environment impact the microbial species present will provide a better understanding of conditions that may alter host susceptibility to pathogens in their environment. We sampled the bacterial skin microbiome of North American wood frogs (Rana sylvatica) from two breeding ponds in the spring, along with the bacterial community present in their vernal breeding pools, and frogs from the nearby forest floor in the summer and fall to determine whether community composition differs by sex, vernal pond site, or temporally across season (spring, summer, fall). Taxon relative abundance data reveals a profile of bacterial phyla similar to those previously described on anuran skin, with Proteobacteria, Bacteroidetes, and Actinobacteria dominating the wood frog skin microbiome. Our results indicate that sex had no significant effect on skin microbiota diversity; however, this may be due to our limited female frog sample size. Vernal pool site had a small but significant effect on skin microbiota, but skin-associated communities were more similar to each other than to the communities observed in the frogs' respective pond water. Across seasons, diversity analyses suggest that there are significant differences between the bacterial skin microbiome of frogs from spring and summer/fall groups while the average α-diversity per frog remained consistent. These results illustrate seasonal variation in wood frog skin microbiome structure and highlight the importance of considering temporal trends in an amphibian microbiome, particularly for species whose life history requires recurrent shifts in habitat and behavior.

Effects of Supplement of Marichromatium gracile YL28 on Water Quality and Microbial Structures in Shrimp Mariculture Ecosystems

The elevated NH₃-N and NO₂-N pollution problems in mariculture have raised concerns because they pose threats to animal health and coastal and offshore environments. Supplement of Marichromatium gracile YL28 (YL28) into polluted shrimp rearing water and sediment significantly decreased ammonia and nitrite concentrations, showing that YL28 functioned as a novel safe marine probiotic in the shrimp culture industry. The diversity of aquatic bacteria in the shrimp mariculture ecosystems was studied by sequencing the V4 region of 16S rRNA genes, with respect to additions of YL28 at the low and high concentrations. It was revealed by 16S rRNA sequencing analysis that Proteobacteria, Planctomycete and Bacteroidetes dominated the community (>80% of operational taxonomic units (OTUs)). Up to 41.6% of the predominant bacterial members were placed in the classes Gammaproteobacteria (14%), Deltaproteobacteria (14%), Planctomycetacia (8%) and Alphaproteobacteria (5.6%) while 40% of OTUs belonged to unclassified ones or others, indicating that the considerable bacterial populations were novel in our shrimp mariculture. Bacterial communities were similar between YL28 supplements and control groups (without addition of YL28) revealed by the β-diversity using PCoA, demonstrating that the additions of YL28 did not disturb the microbiota in shrimp mariculture ecosystems. Instead, the addition of YL28 increased the relative abundance of ammonia-oxidizing and denitrifying bacteria. The quantitative PCR analysis further showed that key genes including nifH and amoA involved in nitrification and nitrate or nitrite reduction significantly increased with YL28 supplementation (p < 0.05). The supplement of YL28 decreased the relative abundance of potential pathogen Vibrio. Together, our studies showed that supplement of YL28 improved the water quality by increasing the relative abundance of ammonia-oxidizing and denitrifying bacteria while the microbial community structure persisted in shrimp mariculture ecosystems.

Monitoring the Diversity and Metabolic Shift of Gut Microbes during Green Tea Feeding in an In Vitro Human Colonic Model

The human gut microbiome plays an important role in human health, and many factors such as environment, host genetics, age, and diet have been found to influence the microbial composition. Tea, as one of the widely consumed beverages, has been known for centuries to have antioxidant, anti-inflammatory, and anticancer effects. To investigate the impact of green tea polyphenol on the diversity and metabolic functions of human gut microbes, we applied an in vitro human colonic model (HCM) in this study to mimic a short-term green tea ingestion event and investigate its related changes to gut microbial composition and their metabolic functions. The pH, temperature, anaerobic environment, feeding nutrient, and time point in each compartment of the HCM were tightly controlled to simulate the intestinal system, and pooled human fecal samples of two healthy volunteers were used for the colon microbiota inoculation within the colonic model. By adding green tea extract (GTE) to the growth medium, the detailed impacts of GTE polyphenol on gut microbial population/diversity, gut microbial metabolites, metabolic pathways, and their associations were investigated via 16 S ribosomal DNA sequencing and liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) analyses. Our data indicated that the treatment of green tea extract applied to gut microbiota can induce a significant decrease in the abundance of Firmicutes and a slight decrease in the abundance of Bacteroidetes, and these changes result in a decreased Firmicutes/Bacteroidetes ratio, which can be an effective indicator for successful GTE intervention, which may generate beneficial health effect to human. Meanwhile, the relative abundances of many detected bacteria genera among three HCM vessels changed through the GTE intervention. The overall effects of GTE on gut microbial beta-diversity were observed by multivariate statistical analyses, and the differences in metabolic profiles from different GTE treatment stages were detected. Moreover, we identified several associations between microbial population and microbial metabolites, which may assist us in establishing new hypotheses for future related studies. In summary, our study suggested that the microbial compositional changes induced by GTE also changed their metabolic functions, and consequentially, may change the host metabolism and impact human health.

Impact of a Model Used to Simulate Chronic Socio-Environmental Stressors Encountered during Spaceflight on Murine Intestinal Microbiota

During deep-space travels, crewmembers face various physical and psychosocial stressors that could alter gut microbiota composition. Since it is well known that intestinal dysbiosis is involved in the onset or exacerbation of several disorders, the aim of this study was to evaluate changes in intestinal microbiota in a murine model used to mimic chronic psychosocial stressors encountered during a long-term space mission. We demonstrate that 3 weeks of exposure to this model (called CUMS for Chronic Unpredictable Mild Stress) induce significant change in intracaecal β-diversity characterized by an important increase of the Firmicutes/Bacteroidetes ratio. These alterations are associated with a decrease of Porphyromonadaceae, particularly of the genus Barnesiella, a major member of gut microbiota in mice and humans where it is described as having protective properties. These results raise the question of the impact of stress-induced decrease of beneficial taxa, support recent data deduced from in-flight experimentations and other ground-based models, and emphasize the critical need for further studies exploring the impact of spaceflight on intestinal microbiota in order to propose strategies to countermeasure spaceflight-associated dysbiosis and its consequences on health.

Pontibacter fetidus sp. nov. and Pontibacter burrus sp. nov., isolated from the soil

Two novel strains, BT213^T and BT327^T, were isolated from the soil collected in Uijeongbu city, Korea. Cells of strains were Gram negative, aerobic, and non-motile. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains BT213^T and BT327^T formed two distinct lineages within the family Hymenobacteraceae (order Cytophagales, class Cytophagia). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain BT213^T and BT327^T belonged to the genus Pontibacter. Strain BT213^T showed the highest similarities of 97.8% with Pontibacter deserti JC215^T. Strain BT327^T showed the highest sequence similarity of 96.5% with Pontibacter mucosus PB3^T. Optimal growth occurred at 25 °C, pH 7, and in the absence of NaCl. The major cellular fatty acid of strains BT213^T and BT327^T were iso-C_15:0 and summed feature 4 (iso-C_17:1 I/anteiso-C_17:1 B). Strains BT213^T and BT327^T had MK-7 as major respiratory quinone and phosphatidylethanolamine as major polar lipids. The genome size of strains BT213^T and BT327^T were 4,072,018 bp and 4,314,171 bp, respectively. The genomic G + C mol% of strains BT213^T and BT327^T are 45.6% and 46.1%, respectively. Based on biochemical, chemotaxonomic, and phylogenetic analysis, two novel species Pontibacter fetidus BT213^T (KCTC 72345^T = NBRC 114379^T) and Pontibacter burrus BT327^T (KCTC 72412^T = NBRC 114376^T) are proposed as type strains.

Biological observations in microbiota analysis are robust to the choice of 16S rRNA gene sequencing processing algorithm: case study on human milk microbiota

BACKGROUND

In recent years, the microbiome field has undergone a shift from clustering-based methods of operational taxonomic unit (OTU) designation based on sequence similarity to denoising algorithms that identify exact amplicon sequence variants (ASVs), and methods to identify contaminating bacterial DNA sequences from low biomass samples have been developed. Although these methods improve accuracy when analyzing mock communities, their impact on real samples and downstream analysis of biological associations is less clear.

RESULTS

Here, we re-processed our recently published milk microbiota data using Qiime1 to identify OTUs, and Qiime2 to identify ASVs, with or without contaminant removal using decontam. Qiime2 resolved the mock community more accurately, primarily because Qiime1 failed to detect Lactobacillus. Qiime2 also considerably reduced the average number of ASVs detected in human milk samples (364 ± 145 OTUs vs. 170 ± 73 ASVs, p < 0.001). Compared to the richness, the estimated diversity measures had a similar range using both methods albeit statistically different (inverse Simpson index: 14.3 ± 8.5 vs. 15.6 ± 8.7, p = 0.031) and there was strong consistency and agreement for the relative abundances of the most abundant bacterial taxa, including Staphylococcaceae and Streptococcaceae. One notable exception was Oxalobacteriaceae, which was overrepresented using Qiime1 regardless of contaminant removal. Downstream statistical analyses were not impacted by the choice of algorithm in terms of the direction, strength, and significance of associations of host factors with bacterial diversity and overall community composition.

CONCLUSION

Overall, the biological observations and conclusions were robust to the choice of the sequencing processing methods and contaminant removal.

Draconibacterium mangrovi sp. nov., isolated from mangrove sediment

A marine bacterial strain, designated GM2-18^T, was isolated from mangrove sediment sampled at Luoyang River estuary, Quanzhou, PR China. Cells were Gram-stain-negative, slightly curved long rod-shaped and facultatively anaerobic with no flagellum. Catalase activity was found to be weak-positive and oxidase-positive. It had no ability to degrade or hydrolyse substrates including skimmed milk, cellulose, starch and Tweens (40, 60 and 80). The 16S rRNA gene sequence of strain GM2-18^T had maximum similarity values to 'Draconibacterium filum' F2^T, Draconibacterium sediminis JN14CK-3^T and Draconibacterium orientale FH5^T of 98.0, 97.8 and 97.4 %, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain GM2-18^T was affiliated to the genus Draconibacterium and formed a clade with an uncultured bacterium clone identified from mangrove environment. Average nucleotide identity values and DNA-DNA hybridization estimates of strain GM2-18^T compared to its Draconibacterium relatives strongly supported that it belonged to a new species. The respiratory quinone was menaquinone MK-7. The major fatty acids (>10 %) consisted of iso-C_15 : 0, anteiso-C_15 : 0 and C_17 : 1  ω6c. The polar lipids were phosphatidylethanolamine, a phospholipid and several unidentified lipids. The genomic size of strain GM2-18^T was 5.9 Mb and the G+C content was 40.8 mol%. Gene prediction and annotation of strain GM2-18^T indicated that there was a nitrogen-fixing gene cluster encoding nitrogenase molybdenum-iron protein and related proteins responsible for nitrogen fixation. Based on the above characteristics, strain GM2-18^T represents a novel species within the genus Draconibacterium. Thus, Draconibacterium mangrovi sp. nov. is proposed with type strain GM2-18^T (=MCCC 1K04382^T=KCTC 72879^T), isolated from mangrove sediment.

Description of Maribellus sediminis sp. nov., a marine nitrogen-fixing bacterium isolated from sediment of cordgrass and mangrove

Two marine bacterial strains designated Y2-1-60^T and GM1-28 were isolated from sediments of cordgrass and mangrove along the Luoyang estuary in Quanzhou Bay, China, respectively. Both strains were Gram-staining-negative, straight rod-shaped, non-flagellum, facultatively anaerobic, nitrogen-fixing, and did not contain carotenoid pigment. Catalase activities were found to be weak positive and oxidase activities negative. The 16S rRNA gene sequences of the two strains were identical and had maximum similarity of 98.0% with Maribellus luteus XSD2^T, and of <94.5% with other species. ANI value (96.9%) and DDH estimate (71.5%) between the two strains supported that they belonged to the same species. ANI value and DDH estimate between the two strains and M. luteus XSD2^T was 74.3% and 19.4%, respectively, indicating that they represent a novel species. Phylogenetic analysis based on 16S rRNA gene and phylogenomic analysis indicated that strains Y2-1-60^T and GM1-28 formed a monophyletic branch within the genus Maribellus. The respiratory quinone was menaquinone MK-7. The major fatty acid (>10%) consisted of iso-C_15:0, and iso-C_17:0 3-OH. The polar lipids consisted of phosphatidylethanolamine and several unidentified lipids. The genomic G+C contents were 41.9-42.0mol%. Gene annotation revealed that strains Y2-1-60^T and GM1-28 contained a set of nif gene cluster (nifHDKENB) responsible for nitrogen fixation. Based on the above characteristics, strains Y2-1-60^T and GM1-28 represent a novel species within the genus Maribellus. Thus, Maribellus sediminis sp. nov. is proposed with type strain Y2-1-60^T (=MCCC 1K04285^T=KCTC 72884^T), isolated from cordgrass sediment and strain GM1-28 (=MCCC 1K04384=KCTC 72880), isolated from mangrove sediment.

Metatranscriptomic identification of polyamine-transforming bacterioplankton in the Gulf of Mexico

The importance of short-chained aliphatic polyamines (PAs) to bacterioplankton-mediated carbon and nitrogen cycles has been repeatedly proposed. However, bacterial taxa and genes involved in the transformations of different PA compounds and their potential spatial variations remain unclear. This study collected surface bacterioplankton from nearshore, offshore, and open ocean stations in the Gulf of Mexico and examined how metatranscriptomes responded to additions of three single PA model compounds (i.e. putrescine, spermidine, or spermine). Our data showed an overrepresentation of genes affiliated with γ-glutamylation and spermidine cleavage pathways in metatranscriptomes received PA amendments and the expression level of each pathway varied among different PA compounds and sampling locations. PA-transforming taxa were affiliated with Actinobacteria, Bacteroidetes, Cyanobacteria, Planctomycetes, and Proteobacteria and their relative importance was also compound and location specific. These findings suggest that PAs are transformed via multiple pathways and by a diversity of marine bacterioplankton in the Gulf of Mexico. The relative importance of different PA transforming pathways and composition of functional microbial communities may be regulated by nutrient status of local environments.

Sex-dependent associations between addiction-related behaviors and the microbiome in outbred rats

BACKGROUND

Multiple factors contribute to the etiology of addiction, including genetics, sex, and a number of addiction-related behavioral traits. One behavioral trait where individuals assign incentive salience to food stimuli ("sign-trackers", ST) are more impulsive compared to those that do not ("goal-trackers", GT), as well as more sensitive to drugs and drug stimuli. Furthermore, this GT/ST phenotype predicts differences in other behavioral measures. Recent studies have implicated the gut microbiota as a key regulator of brain and behavior, and have shown that many microbiota-associated changes occur in a sex-dependent manner. However, few studies have examined how the microbiome might influence addiction-related behaviors. To this end, we sought to determine if gut microbiome composition was correlated with addiction-related behaviors determined by the GT/ST phenotype.

METHODS

Outbred male (N=101) and female (N=101) heterogeneous stock rats underwent a series of behavioral tests measuring impulsivity, attention, reward-learning, incentive salience, and locomotor response. Cecal microbiome composition was estimated using 16S rRNA gene amplicon sequencing. Behavior and microbiome were characterized and correlated with behavioral phenotypes. Robust sex differences were observed in both behavior and microbiome; further analyses were conducted within sex using the pre-established goal/sign-tracking (GT/ST) phenotype and partial least squares differential analysis (PLS-DA) clustered behavioral phenotype.

RESULTS

Overall microbiome composition was not associated to the GT/ST phenotype. However, microbial alpha diversity was significantly decreased in female STs. On the other hand, a measure of impulsivity had many significant correlations to microbiome in both males and females. Several measures of impulsivity were correlated with the genus Barnesiella in females. Female STs had notable correlations between microbiome and attentional deficient. In both males and females, many measures were correlated with the bacterial families Ruminocococcaceae and Lachnospiraceae.

CONCLUSIONS

These data demonstrate correlations between several addiction-related behaviors and the microbiome specific to sex.

Arsenic and the gastrointestinal tract microbiome

Arsenic is a toxin, ranking first on the Agency for Toxic Substances and Disease Registry and the Environmental Protection Agency Priority List of Hazardous Substances. Chronic exposure increases the risk of a broad range of human illnesses, most notably cancer; however, there is significant variability in arsenic-induced disease among exposed individuals. Human genetics is a known component, but it alone cannot account for the large inter-individual variability in the presentation of arsenicosis symptoms. Each part of the gastrointestinal tract (GIT) may be considered as a unique environment with characteristic pH, oxygen concentration, and microbiome. Given the well-established arsenic redox transformation activities of microorganisms, it is reasonable to imagine how the GIT microbiome composition variability among individuals could play a significant role in determining the fate, mobility and toxicity of arsenic, whether inhaled or ingested. This is a relatively new field of research that would benefit from early dialogue aimed at summarizing what is known and identifying reasonable research targets and concepts. Herein, we strive to initiate this dialogue by reviewing known aspects of microbe-arsenic interactions and placing it in the context of potential for influencing host exposure and health risks. We finish by considering future experimental approaches that might be of value.

The microbiome of modern microbialites in Bacalar Lagoon, Mexico

Microbialites are highly diverse microbial communities that represent modern examples of the oldest life forms, stromatolites (dated >3.7 Ga). Bacalar Lagoon, in Mexico, harbors the largest freshwater microbialite occurrences of the world; yet diverse anthropogenic activities are changing the oligotrophic conditions of the lagoon. The objective of this work was to perform a spatial exploration of the microbialites of Bacalar Lagoon, analyze their prokaryote diversity, following a high throughput sequencing approach of the V4 region of the 16S rDNA, and correlate to the environmental parameters that influence the structure of these communities. The results indicate the presence of microbialites throughout the periphery of the lagoon. The microbiome of the microbialites is composed primarily of Proteobacteria (40-80%), Cyanobacteria (1-11%), Bacteroidetes (7-8%), Chloroflexi (8-14%), Firmicutes (1-23%), Planctomycetes (1-8%), and Verrucomicrobia (1-4%). Phylogenetic distance analyses suggests two distinct groups of microbialites associated with regions in the lagoon that have differences in their environmental parameters, including soluble reactive silicate (in the north), bicarbonates and available forms of nitrogen (ammonium, nitrates and nitrites) (in the south). These microbialite groups had differences in their microbiome composition associated to strong anthropogenic pressure on water quality (agriculture, landfill leachate, lack of water treatment infrastructure and intensive tourism), which were related to a loss of microbial diversity.

Most dominant roles of insect gut bacteria: digestion, detoxification, or essential nutrient provision?

BACKGROUND

The insect gut microbiota has been shown to contribute to the host's digestion, detoxification, development, pathogen resistance, and physiology. However, there is poor information about the ranking of these roles. Most of these results were obtained with cultivable bacteria, whereas the bacterial physiology may be different between free-living and midgut-colonizing bacteria. In this study, we provided both proteomic and genomic evidence on the ranking of the roles of gut bacteria by investigating the anal droplets from a weevil, Cryptorhynchus lapathi.

RESULTS

The gut lumen and the anal droplets showed qualitatively and quantitatively different subsets of bacterial communities. The results of 16S rRNA sequencing showed that the gut lumen is dominated by Proteobacteria and Bacteroidetes, whereas the anal droplets are dominated by Proteobacteria. From the anal droplets, enzymes involved in 31 basic roles that belong to 7 super roles were identified by Q-TOF MS. The cooperation between the weevil and its gut bacteria was determined by reconstructing community pathway maps, which are defined in this study. A score was used to rank the gut bacterial roles. The results from the proteomic data indicate that the most dominant role of gut bacteria is amino acid biosynthesis, followed by protein digestion, energy metabolism, vitamin biosynthesis, lipid digestion, plant secondary metabolite (PSM) degradation, and carbohydrate digestion, while the order from the genomic data is amino acid biosynthesis, vitamin biosynthesis, lipid digestion, energy metabolism, protein digestion, PSM degradation, and carbohydrate digestion. The PCA results showed that the gut bacteria form functional groups from the point of view of either the basic role or super role, and the MFA results showed that there are functional variations among gut bacteria. In addition, the variations between the proteomic and genomic data, analyzed with the HMFA method from the point of view of either the bacterial community or individual bacterial species, are presented.

CONCLUSION

The most dominant role of gut bacteria is essential nutrient provisioning, followed by digestion and detoxification. The weevil plays a pioneering role in diet digestion and mainly digests macromolecules into smaller molecules which are then mainly digested by gut bacteria.

It's the fiber, not the fat: significant effects of dietary challenge on the gut microbiome

BACKGROUND

Dietary effects on the gut microbiome play key roles in the pathophysiology of inflammatory disorders, metabolic syndrome, obesity, and behavioral dysregulation. Often overlooked in such studies is the consideration that experimental diets vary significantly in the proportion and source of their dietary fiber. Commonly, treatment comparisons are made between animals fed a purchased refined diet that lacks soluble fiber and animals fed a standard vivarium-provided chow diet that contains a rich source of soluble fiber. Despite the well-established critical role of soluble fiber as the source of short chain fatty acid production via the gut microbiome, the extent to which measured outcomes are driven by differences in dietary fiber is unclear. Further, the interaction between sex and age in response to dietary transition is likely important and should also be considered.

RESULTS

We compared the impact of transitioning young adult and 1-year aged male and female mice from their standard chow diet to a refined low soluble fiber diet on gut microbiota community composition. Then, to determine the contribution of dietary fat, we also examined the impact of transitioning a subset of animals from refined low-fat to refined high-fat diet. We used a serial sampling strategy coupled with 16S rRNA marker gene sequencing to examine consequences of recurrent dietary switching on gut microbiota community dynamics. Analysis revealed that the transition from a chow diet to a refined diet that lacks soluble fiber accounted for most of the variance in community structure, diversity, and composition across all groups. This dietary transition was characterized by a loss of taxa within the phylum Bacteroidetes and expansion of Clostridia and Proteobacteria in a sex- and age-specific manner. Most notably, no changes to gut microbiota community structure and composition were observed between mice consuming either refined low- or high-fat diet, suggesting that transition to the refined diet that lacks soluble fiber is the primary driver of gut microbiota alterations, with limited additional impact of dietary fat on gut microbiota.

CONCLUSION

Collectively, our results show that the choice of control diet has a significant impact on outcomes and interpretation related to diet effects on gut microbiota. As the reduction of soluble fiber may influence synthesis of microbial metabolites that are important for regulating metabolic, immune, behavioral, and neurobiological outcomes, additional studies are now needed to fully delineate the contribution of fat and fiber on the gut microbiome. Video Abtract.

Algoriphagus aquimaris sp. nov., isolated from seashore sand

Strain F21^T, a marine, aerobic, Gram-negative, rod-shaped bacterium, was isolated from seashore sand sampled in Pohang, Republic of Korea. Cells of strain F21^T were non-motile, catalase-positive, oxidase-positive, non-spore-forming and formed pinkish-red colonies on marine agar. The strain grew optimally at 37°C, pH 7 and in the presence of 2-3 % NaCl (w/v). Analysis of the 16S rRNA gene sequence of strain F21^T revealed that it belonged to the genus Algoriphagus, family Cyclobacteriaceae, with similarity values of 98.1 and 96.8 % to Algoriphagus marincola DSM 16067^T and Algoriphagus ornithinivorans IMSNU 14014^T, respectively. When comparing the genome sequence of F21 ^T with those of the type strains of six species of the genus Algoriphagus, the values obtained were below the thresholds for analyses of average nucleotide identity (71.8-92.7 %) and in silico DNA-DNA hybridization using the Genome-to-Genome Distance Calculator (14.7-75.2 %). The DNA G+C content of strain F21^T was 42.0 mol%. The chemotaxonomic characteristics of F21^T included MK-7 as the predominant isoprenoid quinone, iso-C_15 : 0, iso-C_17 : 0 3-OH and summed feature 3 (C_16 : 1ω6c and/or C_16 : 1ω7c) as major cellular fatty acids, and phosphatidylcholine and phosphatidylethanolamine as major polar lipids. On the basis of phenotypic and chemotaxonomic properties, phylogenetic distinctiveness, and genomic data, we named strain F21^T as Algoriphagus aquimaris sp. nov. and proposed that strain F21^T (=KEMB 2250-007^T= KCTC 72106^T=JCM 33187^T) in the genus Algoriphagus represents a novel species.

Characterizations of microbial diversity and machine oil degrading microbes in machine oil contaminated soil

Microbial diversity in machine oil contaminated soil was determined by high-throughput amplicon sequencing technology. The diversity of culturable microbes in the contaminated soil was further characterized using polymerase chain reaction method. Proteobacteria and Bacteroidetes were the most dominant phyla and occupied 52.73 and 16.77%, respectively, while the most abundant genera were Methylotenera (21.62%) and Flavobacterium (3.06%) in the soil. In the culturable microbes, the major phyla were Firmicutes (46.15%) and Proteobacteria (37.36%) and the most abundant genera were Bacillus (42.86%) and Aeromonas (34.07%). Four isolated microbes with high machine oil degradation efficiency were selected to evaluate their characteristics on the oil degradation. All of them reached their highest oil degradation rate after 7 days of incubation. Most of them significantly increased their oil degradation rate by additional carbon or organic nitrogen source in the incubation medium. The oil degradation rate by combination of the four microbes at the same inoculation level was also higher than the rate from each individual microbe. The protocol and findings of this study are very useful for developing micro-bioremediation method to eliminate machine oil contaminants from soil.

Colonisation of the proximal intestinal remnant in newborn infants with enterostomy: a longitudinal study protocol

INTRODUCTION

The gut microbiota plays a main role in the maintenance of host's health. Exposure to different conditions in early life contributes to distinct 'pioneer' bacterial communities in the intestine, which shape the newborn infant development. Newborn infants with congenital malformations of the gastrointestinal tract (CMGIT), necrotising enterocolitis (NEC) and spontaneous intestinal perforation (SIP) commonly require abdominal surgery and enterostomy. The knowledge about the colonisation of these newborns' intestine by microorganisms is scarce. This protocol is designed to explore the microbial colonisation over time of the proximal intestinal remnant in newborn infants who underwent surgery for CMGIT, NEC or SIP and require enterostomy.

METHODS AND ANALYSIS

The literature about microbiota colonisation in newborn infants with enterostomy was reviewed and an observational, longitudinal, prospective study was designed. The infants will be recruited at the Neonatal Intensive Care Unit of the Hospital Dona Estefânia, Centro Hospitalar Universitário de Lisboa Central. Samples of the enterostomy effluent will be collected every 3 days, through 21 days after the first collection. The microorganisms colonising the proximal intestinal remnant will be identified using the 16S rRNA sequence analysis and a subset of microorganisms will be quantified using real-time PCR. This protocol may serve as basis for future observational and interventional studies on the modulation of the intestinal microbiota (eg, probiotics) on short and long-term outcomes in this population.

ETHICS AND DISSEMINATION

This study protocol was approved by the Ethics Committee of Centro Hospitalar Universitário de Lisboa Central (441/2017) and by the Ethics Committee of NOVA Medical School, Universidade Nova de Lisboa (n°50/2018/CEFCM). The results will be spread through peer-reviewed publications and presentations at international scientific meetings.

TRIAL REGISTRATION NUMBER

NCT03340259.

Labilibaculum antarcticum sp. nov., a novel facultative anaerobic, psychrotorelant bacterium isolated from marine sediment of Antarctica

A novel facultative anaerobic and facultative psychrophilic bacterium, designated SPP2^T, was isolated from an Antarctic marine sediment. Cells of the isolate were observed to be long rods (0.5 × 5-10 μm), Gram-stain negative and to have gliding motility. For growth, the optimum NaCl concentration was found to be 2-3% and the optimum temperature to be 18-22 °C. Strain SPP2^T cannot use sulfate and nitrate as electron acceptors in the presence of lactate. The G+C content of the genomic DNA was determined to be 36.0 mol%.. The major cellular fatty acids were identified as anteiso-C_15:0 and iso-C_15:0. MK-7 was found to be the predominant respiratory quinone. Phylogenetic analysis based on the 16S rRNA gene revealed that the novel strain belongs to the family Marinifilaceae and to be closely related to Labilibaculum manganireducens 59.10-2M^T with 16S rRNA gene sequence identity of 98%. The OrthoANI and dDDH values between the genome sequences of strain SPP2^T and its close relative were 84% and 27.3%, which are lower than the threshold values for species delineation. On the basis of phylogenetic and phenotypic characterisation, Labilibaculum antarcticum sp. nov. is proposed with the type strain SPP2^T (= NBRC 111151^T = CECT 9460^T).

Flammeovirga pectinis sp. nov., isolated from the gut of the Korean scallop, Patinopecten yessoensis

A novel Gram-stain-negative, aerobic, rod-shaped, reddish-orange-coloured, gliding bacterial strain, designated L12M1^T, was isolated from the gut of the Korean scallop, Patinopecten yessoensis. Phylogenetic analysis based on 16S rRNA gene sequence revealed that strain L12M1^T formed a monophyletic clade with the strains in the genus Flammeovirga and showed highest 16S rRNA gene sequence similarity to Flammeovirga kamogawensis YS10^T (98.66 %). The major cellular fatty acids of strain L12M1^T were iso-C_15 : 0 and C_20 : 4ω6,9,12,15c. The predominant isoprenoid quinone was MK-7. The major polyamines were spermidine, cadaverine and the minor polyamine was putrescine. The DNA G+C content was 32.1 mol%. The phylogenetic, phenotypic, biochemical, chemotaxonomic and genotypic results indicated that strain L12M1^T represents a novel species of the genus Flammeovirga, for which the name Flammeovirga pectinis sp. nov. is proposed. The type strain is L12M1^T (=KCTC 62750^T=JCM 33169^T).

Global phylogeography and ancient evolution of the widespread human gut virus crAssphage

Microbiomes are vast communities of microorganisms and viruses that populate all natural ecosystems. Viruses have been considered to be the most variable component of microbiomes, as supported by virome surveys and examples of high genomic mosaicism. However, recent evidence suggests that the human gut virome is remarkably stable compared with that of other environments. Here, we investigate the origin, evolution and epidemiology of crAssphage, a widespread human gut virus. Through a global collaboration, we obtained DNA sequences of crAssphage from more than one-third of the world's countries and showed that the phylogeography of crAssphage is locally clustered within countries, cities and individuals. We also found fully colinear crAssphage-like genomes in both Old-World and New-World primates, suggesting that the association of crAssphage with primates may be millions of years old. Finally, by exploiting a large cohort of more than 1,000 individuals, we tested whether crAssphage is associated with bacterial taxonomic groups of the gut microbiome, diverse human health parameters and a wide range of dietary factors. We identified strong correlations with different clades of bacteria that are related to Bacteroidetes and weak associations with several diet categories, but no significant association with health or disease. We conclude that crAssphage is a benign cosmopolitan virus that may have coevolved with the human lineage and is an integral part of the normal human gut virome.

Global phylogeography and ancient evolution of the widespread human gut virus crAssphage

Microbiomes are vast communities of microorganisms and viruses that populate all natural ecosystems. Viruses have been considered to be the most variable component of microbiomes, as supported by virome surveys and examples of high genomic mosaicism. However, recent evidence suggests that the human gut virome is remarkably stable compared with that of other environments. Here, we investigate the origin, evolution and epidemiology of crAssphage, a widespread human gut virus. Through a global collaboration, we obtained DNA sequences of crAssphage from more than one-third of the world's countries and showed that the phylogeography of crAssphage is locally clustered within countries, cities and individuals. We also found fully colinear crAssphage-like genomes in both Old-World and New-World primates, suggesting that the association of crAssphage with primates may be millions of years old. Finally, by exploiting a large cohort of more than 1,000 individuals, we tested whether crAssphage is associated with bacterial taxonomic groups of the gut microbiome, diverse human health parameters and a wide range of dietary factors. We identified strong correlations with different clades of bacteria that are related to Bacteroidetes and weak associations with several diet categories, but no significant association with health or disease. We conclude that crAssphage is a benign cosmopolitan virus that may have coevolved with the human lineage and is an integral part of the normal human gut virome.

Microbiome profiling of the onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae)

The gut microbial community structure of adult Thrips tabaci collected from 10 different agro-climatically diverse locations of India was characterized by using the Illumina MiSeq platform to amplify the V3 region of the 16S rRNA gene of bacteria present in the sampled insects. Analyses were performed to study the bacterial communities associated with Thrips tabaci in India. The complete bacterial metagenome of T. tabaci was comprised of 1662 OTUs of which 62.25% belong to known and 37.7% of unidentified/unknown bacteria. These OTUs constituted 21 bacterial phyla of 276 identified genera. Phylum Proteobacteria was predominant, followed by Actinobacteria, Firmicutes, Bacteroidetes and Cyanobacteria. Additionally, the occurrence of the reproductive endosymbiont, Wolbachia was detected at two locations (0.56%) of the total known OTUs. There is high variation in diversity and species richness among the different locations. Alpha-diversity metrics indicated the higher gut bacterial diversity at Bangalore and lowest at Rahuri whereas higher bacterial species richness at T. tabaci samples from Imphal and lowest at Jhalawar. Beta diversity analyses comparing bacterial communities between the samples showed distinct differences in bacterial community composition of T. tabaci samples from different locations. This paper also constitutes the first record of detailed bacterial communities associated with T. tabaci. The location-wise variation in microbial metagenome profile of T. tabaci suggests that bacterial diversity might be governed by its population genetic structure, environment and habitat.

Microbial biofilm formation and community structure on low-density polyethylene microparticles in lake water microcosms

The occurrence of microplastics (MPs) in the environment has been gaining widespread attention globally. MP-colonizing microorganisms are important links for MPs contamination in various ecosystems, but have not been well understood. To partially address this issue, the present study investigated biofilm formation by microorganisms originating from lake water on low-density polyethylene (LDPE) MPs using a cultivation approach and the surface-related effects on the MP-associated microbial communities using 16S rRNA high-throughput sequencing. With the addition of nonionic surfactants and UV-irradiation pretreatment that changed the surface properties of LDPE MPs, more microorganisms were colonized on LDPE surface. Microbial community analysis indicated that LDPE MPs were primarily colonized by the phyla Proteobacteria, Bacteroidetes and Firmicutes, and the surface roughness and hydrophobicity of MP were important factors shaping the LDPE MP-associated microbial community structure. Half of the top 20 most abundant genera colonizing on LDPE were found to be potential pathogens, e.g., plant pathogens Agrobacterium, nosocomial pathogens Chryseobacterium and fish pathogens Flavobacterium. This study demonstrated rapid bacterial colonization of LDPE MPs in lake water microcosms, the role of MPs as transfer vectors for harmful microorganisms in lake water, and provided a first glimpse into the effect of surface properties on LDPE MP-associated biofilm communities.

Durable Long-Term Bacterial Engraftment following Encapsulated Fecal Microbiota Transplantation To Treat Clostridium difficile Infection

Fecal microbiota transplantation (FMT) has become a common rescue therapy for recurrent Clostridium difficile infection, and encapsulated delivery (cFMT) of healthy donor microbiota shows similar clinical efficacy as more traditional routes of administration. In this study, we characterized long-term patterns of bacterial engraftment in a cohort of 18 patients, who received capsules from one of three donors, up to 409 days post-FMT. Bacterial communities were characterized using Illumina sequencing of the V5-V6 hypervariable regions of the 16S rRNA gene, and engraftment was determined by using the Bayesian algorithm SourceTracker. All patients recovered clinically and were free of C. difficile infection following cFMT. The majority of patients (61%) showed high levels of engraftment after the first week following FMT, which were sustained throughout the year. A small subset, 22%, experienced a decline in donor engraftment after approximately 1 month, and a few patients (17%), two of whom were taking metformin, showed delayed and low levels of donor engraftment. Members of the genera Bacteroides, Parabacteroides, and Faecalibacterium were significantly and positively correlated with donor similarity (ρ = 0.237 to 0.373, P ≤ 0.017). Furthermore, throughout the year, patient fecal communities showed significant separation based on the donor fecal microbiota that they received (P < 0.001). Results of this study, which characterize long-term engraftment following cFMT, suggest that numerical donor similarity is not strictly related to clinical outcome and identify a persistent donor-specific effect on patient fecal microbial communities. Furthermore, results suggest that members of the Bacteroidetes may be important targets to improve engraftment via cFMT.IMPORTANCE Recurrent Clostridium difficile infection (rCDI) is the most common cause of hospital- and community-acquired diarrheal infection associated with antibiotic use. Fecal microbiota transplantation (FMT), a treatment that involves administration of fecal bacteria from a healthy donor to a recipient patient, is a highly effective rescue therapy for rCDI that is increasingly being incorporated into standard clinical practice. Encapsulated, freeze-dried preparations of fecal microbiota, administered orally, offer the simplest and most convenient route of FMT delivery for patients (cFMT). In this study, we evaluated the extent of bacterial engraftment following cFMT and the duration of donor bacterial persistence. All patients studied recovered clinically but showed differing patterns in long-term microbial community similarity to the donor that were associated with members of the bacterial group Bacteroidetes, previously shown to be prominent contributors to rCDI resistance. Results highlight long-lasting, donor-specific effects on recipient patient microbiota and reveal potential bacterial targets to improve cFMT engraftment.

Ilyomonas limi gen. nov., sp. nov., a new member of the family Chitinophagaceae isolated from mud

A Gram-strain negative, aerobic, catalase and oxidase positive, non-motile, short rod-shaped bacterium, designated 17mud1-8^T, was isolated from mud collected from Nowon-gu, Seoul, South Korea. The strain was found to be able to grow at 10-40 °C (optimum 28-30 °C), pH 5.0-8.0 (optimum 7.0), and in the absence of NaCl. The nearly full-length 16S rRNA gene of strain 17mud1-8^T exhibits sequence similarity of 94.1% with that of Panacibacter ginsenosidivorans Gsoil 1550^T, followed by 93.6% sequence similarity with Parafilimonas terrae DSM 28286^T. Phylogenetic analysis indicated that strain 17mud1-8^T belongs to the family Chitinophagaceae, sharing approximately 94.1-91.9% sequence similarity with members of closely related genera. The respiratory quinone was identified as MK-7. The predominant fatty acids were found to consist of iso-C_15:0, iso-C_17:1ω5c and iso-C_15:1 G. The polar lipids were identified as phosphatidylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid, ten unidentified aminolipids and seven unidentified lipids. The draft genome of 17mud1-8^T has G+C content of 40.9 mol% and a 5.8 Mb chromosome. On the basis of the phenotypic and genotypic properties, and phylogenetic inference, strain 17mud1-8^T was found to represent a novel genus in the family Chitinophagaceae, for which the name Ilyomonas limi gen. nov., sp. nov. is proposed, with the type strain 17mud1-8^T(=KCTC 52874^T = NBRC 112826^T).

Flavisolibacter nicotianae sp. nov., isolated from rhizosphere soil of Nicotiana tabacum L

A Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated strain X7XT, was isolated from a rhizosphere soil sample of Nicotiana tabacum L. collected from a tobacco factory located in Kunming, south-western China. The cells showed oxidase-positive and catalase-positive reactions. Growth occurred at 20-40 °C and pH 6.0-8.0, with optimal growth at 30 °C and pH 7.0. The predominant respiratory quinone was MK-7. The major fatty acids were identified as iso-C15 : 0, iso-C17 : 0 3OH and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The cellular polar lipids contained phosphatidylethanolamine, an unidentified aminophospholipid, two unidentified glycolipids, four unidentified aminolipids and four unidentified lipids. The genomic DNA G+C content was 49.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain X7XT should be affiliated to the genus Flavisolibacter. Results from further analysis showed that strain X7XT had highest 16S rRNA gene sequence similarity to Flavisolibacter metallilatus TX0661T (96.4 %) and 'Flavisolibacter swuensis' SR2-4-2T (96.4 %), followed by other species of the genus Flavisolibacter. The polyphasic taxonomic characteristics indicated that strain X7XT represents a novel species of the genus Flavisolibacter, for which the name Flavisolibacternicotianae sp. nov. (type strain X7XT=KCTC 62326T=CGMCC 16451T) is proposed.

Hymenobacter oligotrophus sp. nov., isolated from a contaminated agar plate

A taxonomic study of a Gram-stain negative, rod-shaped, motile, asporogenous, catalase- and oxidase-positive bacterium, sh-6^T, forming pink-red colonies, isolated from a contaminated R2A plate in the laboratory was performed. Its optimum growth temperature was determined to be 28 °C in the absence of NaCl on R2A plates. On the basis of 16S rRNA gene sequence analysis, strain sh-6^T belongs to the genus Hymenobacter and is closely related to Hymenobacter deserti ZLB-3^T (95.05%), Hymenobacter paludis KBP-30^T (94.96%), Hymenobacter coalescens WW84^T (94.04%), Hymenobacter gummosus ANT-18^T (93.38%), Hymenobacter ocellatus Myx2105^T (93.70%), Hymenobacter jeollabukensis 1-3-3-8^T (93.48%) and Hymenobacter koreensis GYR3077^T (93.21%). Comparison of the genome of strain sh-6^T and that of H. gummosus ANT-18^T gave digital DNA-DNA hybridization and Average Nucleotide Identity values of 20.6% and 78.4%, respectively. The respiratory isoprenoid quinone and polyamine component were identified as MK-7 and sym-homospermidine, respectively. The major cellular fatty acids identified as iso-C_15:0, summed feature 4 (iso-C_17:1 I/anteiso B), iso-C_16:0, iso-C_17:0 3-OH and iso-C_17:0. The major polar lipid of strain sh-6^T determined to be phosphatidylethanolamine. The DNA G+C content was determined to be 60.5 mol%. On the basis of the evidence presented in this study, a novel species of the genus Hymenobacter, Hymenobacter oligotrophus sp. nov., is proposed, with the type strain sh-6^T (= CCTCC AB 2016064^T = KCTC 62345^T).

Comparison of Bacterial Populations in the Ceca of Swine at Two Different Stages and their Functional Annotations

The microbial composition in the cecum of pig influences host health, immunity, nutrient digestion, and feeding requirements significantly. Advancements in metagenome sequencing technologies such as 16S rRNAs have made it possible to explore cecum microbial population. In this study, we performed a comparative analysis of cecum microbiota of crossbred Korean native pigs at two different growth stages (stage L = 10 weeks, and stage LD = 26 weeks) using 16S rRNA sequencing technology. Our results revealed remarkable differences in microbial composition, α and β diversity, and differential abundance between the two stages. Phylum composition analysis with respect to SILVA132 database showed Firmicutes to be present at 51.87% and 48.76% in stages L and LD, respectively. Similarly, Bacteroidetes were present at 37.28% and 45.98% in L and LD, respectively. The genera Prevotella, Anaerovibrio, Succinivibrio, Megasphaera were differentially enriched in stage L, whereas Clostridium, Terrisporobacter, Rikenellaceae were enriched in stage LD. Functional annotation of microbiome by level-three KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis revealed that glycine, serine, threonine, valine, leucine, isoleucine arginine, proline, and tryptophan metabolism were differentially enriched in stage L, whereas alanine, aspartate, glutamate, cysteine, methionine, phenylalanine, tyrosine, and tryptophan biosynthesis metabolism were differentially enriched in stage LD. Through machine-learning approaches such as LEfSe (linear discriminant analysis effect size), random forest, and Pearson's correlation, we found pathways such as amino acid metabolism, transport systems, and genetic regulation of metabolism are commonly enriched in both stages. Our findings suggest that the bacterial compositions in cecum content of pigs are heavily involved in their nutrient digestion process. This study may help to meet the demand of human food and can play significant roles in medicinal application.

Diversity of the microbial community and cultivable protease-producing bacteria in the sediments of the Bohai Sea, Yellow Sea and South China Sea

The nitrogen (N) cycle is closely related to the stability of marine ecosystems. Microbial communities have been directly linked to marine N-cycling processes. However, systematic research on the bacterial community composition and diversity involved in N cycles in different seas is lacking. In this study, microbial diversity in the Bohai Sea (BHS), Yellow Sea (YS) and South China Sea (SCS) was surveyed by targeting the hypervariable V4 regions of the 16S rRNA gene using next-generation sequencing (NGS) technology. A total of 2,505,721 clean reads and 15,307 operational taxonomic units (OTUs) were obtained from 86 sediment samples from the three studied China seas. LEfSe analysis demonstrated that the SCS had more abundant microbial taxa than the BHS and YS. Diversity indices demonstrated that Proteobacteria and Planctomycetes were the dominant phyla in all three China seas. Canonical correspondence analysis (CCA) indicated that pH (P = 0.034) was the principal determining factors, while the organic matter content, depth and temperature had a minor correlated with the variations in sedimentary microbial community distribution. Cluster and functional analyses of microbial communities showed that chemoheterotrophic and aerobic chemoheterotrophic microorganisms widely exist in these three seas. Further research found that the cultivable protease-producing bacteria were mainly affiliated with the phyla Proteobacteria, Firmicutes and Bacteroidetes. It was very clear that Pseudoalteromonadaceae possessed the highest relative abundance in the three sea areas. The predominant protease-producing genera were Pseudoalteromonas and Bacillus. These results shed light on the differences in bacterial community composition, especially protease-producing bacteria, in these three China seas.

Genomic and metatranscriptomic analyses of carbon remineralization in an Antarctic polynya

BACKGROUND

Polynyas in the Southern Ocean are regions of intense primary production, mainly by Phaeocystis antarctica. Carbon fixed by phytoplankton in the water column is transferred to higher trophic levels, and finally, to the deep ocean. However, in the Amundsen Sea, most of this organic carbon does not reach the sediment but is degraded in the water column due to high bacterial heterotrophic activity.

RESULTS

We reconstructed 12 key bacterial genomes from different phases of bloom and analyzed the expression of genes involved in organic carbon remineralization. A high correlation of gene expression between the peak and decline phases was observed in an individual genome bin-based pairwise comparison of gene expression. Polaribacter belonging to Bacteroidetes was found to be dominant in the peak phase, and its transcriptional activity was high (48.9% of the total mRNA reads). Two dominant Polaribacter bins had the potential to utilize major polymers in P. antarctica, chrysolaminarin and xylan, with a distinct set of glycosyl hydrolases. In the decline phase, Gammaproteobacteria (Ant4D3, SUP05, and SAR92), with the potential to utilize low molecular weight-dissolved organic matter (LMW-DOM) including compatible solutes, was increased. The versatility of Gammaproteobacteria may contribute to their abundance in organic carbon-rich polynya waters, while the SAR11 clade was found to be predominant in the sea ice-covered oligotrophic ocean. SAR92 clade showed transcriptional activity for utilization of both polysaccharides and LMW-DOM; this may account for their abundance both in the peak and decline phases. Ant4D3 clade was dominant in all phases of the polynya bloom, implicating the crucial roles of this clade in LMW-DOM remineralization in the Antarctic polynyas.

CONCLUSIONS

Genomic reconstruction and in situ gene expression analyses revealed the unique metabolic potential of dominant bacteria of the Antarctic polynya at a finer taxonomic level. The information can be used to predict temporal community succession linked to the availability of substrates derived from the P. antarctica bloom. Global warming has resulted in compositional changes in phytoplankton from P. antarctica to diatoms, and thus, repeated parallel studies in various polynyas are required to predict global warming-related changes in carbon remineralization.

Bacterial community changes in a glacial-fed Tibetan lake are correlated with glacial melting

Climate change-induced glacial melting is a global phenomenon. The effects of climate change-induced melting on the microbial ecology in different glacial-fed aquatic systems have been well illuminated, but the resolution of seasonal dynamics was still limited. Here, we studied bacterial community composition and diversity in a glacial-fed Tibetan lake, Lake Ranwu, to elucidate how glacial-fed aquatic ecosystems respond to the seasonal glacial melting. Obvious seasonal variations of bacterial dominant groups were found in Lake Ranwu and inlet rivers. In April, the majority of OTUs belonged to the Bacteroidetes, Actinobacteria and Proteobacteria. The Proteobacteria increased to the most abundant phylum in July and November, while the Bacteroidetes and Actinobacteria decreased about 50% over seasons. Most key discriminant taxa of each season's community strongly associated with specific environmental variables, suggesting their adaptation to seasonal environments. Bacterial alpha diversity varied among seasons and exhibited strongly negative correlations with conductivity. Conductivity was the major driving force in determining the seasonal variation of bacterial community composition. Fluctuated conductivity was one of the consequences of seasonal melting of glaciers. This study offered evidence for the unique seasonal dynamics pattern of bacterial communities responding to glacial melting. Moreover, this study may provide a reference for assessing the long-term effects of glacial retreat on glacial-fed aquatic ecosystems.

Marinilabilia rubra sp. nov., isolated from a marine solar saltern

A novel cherry-red-pigmented, Gram-stain-negative, gliding, facultatively anaerobic and rod-shaped bacterium, designated strain WTE16^T, was isolated from a sediment sample taken from a marine solar saltern of Wendeng, China (36° 59' 56.49'' N 122° 1' 38.84'' E). The novel isolate was able to grow at 20-40 °C (optimum 33 °C), at pH 6.0-9.0 (optimum pH 7.0) and with 1.0-12.0 % (w/v) NaCl (optimum 3.0-5.0 %). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the most closely related validly published species is Marinilabilia salmonicolor JCM 21150^T (96.0 % similarity). Average nucleotide identity, average amino acid identity, percentage of conserved proteins and digital DNA-DNA hybridization values between strain WTE16^T and Marinilabilia salmonicolor JCM 21150^T were 73.8 %, 73.5 %, 63.4 % and 19.5-24.2 %, respectively. The genomic DNA G+C content of strain WTE16^T was 40.8 mol%. Chemotaxonomic analysis showed that the sole respiratory quinone was menaquinone 7 (MK-7), and the major fatty acids included iso-C15 : 0 and anteiso-C15 : 0. The polar lipid profile of strain WTE16^T included phosphatidylethanolamine, three unidentified phospholipids and three unidentified lipids. On the basis of its phylogenetic, phenotypic, chemotaxonomic, genotypic and genomic characteristics, strain WTE16^T is suggested to represent a novel species of the genus Marinilabilia, for which the name Marinilabilia rubra sp. nov. is proposed. The type strain is WTE16^T (=KCTC 62599^T=MCCC 1H00311^T).

Evaluation of VITEK MS, Clin-ToF-II MS, Autof MS 1000 and VITEK 2 ANC card for identification of Bacteroides fragilis group isolates and antimicrobial susceptibilities of these isolates in a Chinese university hospital

BACKGROUND AND PURPOSE

Bacteroides fragilis group isolates are most frequently isolated anaerobic pathogens. This study aimed to evaluate the accuracy of VITEK MS, Clin-ToF-II MS, Autof MS 1000 and VITEK 2 ANC card on the identification of clinical B. fragilis group isolates, as well as to determine their antimicrobial susceptibilities.

METHODS

A total of 138 isolates of B. fragilis group isolates were identified with the three MALDI-TOF MS systems and VITEK 2 ANC cards. 16S rRNA gene sequencing was used as the reference identification method for comparison. Antimicrobial susceptibilities were determined by agar dilution method to 19 antimicrobial agents recommended by Clinical and Laboratory Standards Institute (CLSI).

RESULTS

Hundred thirty three isolates of Bacteroides spp. and 5 isolates of Parabacteroides spp. were identified by 16S rRNA sequencing. The rates of accurate identification at species level of VITEK MS, Clin-ToF-II MS, Autof MS 1000 and VITEK 2 ANC card were 94.2%, 94.2%, 98.6% and 94.9%, respectively, while that at genus level were 99.3%, 100%, 100% and 97.8%, respectively. Metronidazole and chloramphenicol were the most susceptible agents (99.3% and 92.8%, respectively), followed by meropenem, ertapenem, imipenem and piperacillin/tazobactam to which the susceptible rates ranged from 76.8% to 79.0%. The susceptible rates to carbapenems decreased 12.4-15.3% from 2010-2013 to 2014-2017.

CONCLUSION

All the four systems provided high accurate rate on the identification of B. fragilis group isolates. Metronidazole showed highest activity against these isolates. Attention should be paid to the higher resistant rates to carbapenems, clindamycin, moxifloxacin and tigecycline than the other countries.

Discovery of a Novel Periodontal Disease-Associated Bacterium

One of the world's most common infectious disease, periodontitis (PD), derives from largely uncharacterized communities of oral bacteria growing as biofilms (a.k.a. plaque) on teeth and gum surfaces in periodontal pockets. Bacteria associated with periodontal disease trigger inflammatory responses in immune cells, which in later stages of the disease cause loss of both soft and hard tissue structures supporting teeth. Thus far, only a handful of bacteria have been characterized as infectious agents of PD. Although deep sequencing technologies, such as whole community shotgun sequencing have the potential to capture a detailed picture of highly complex bacterial communities in any given environment, we still lack major reference genomes for the oral microbiome associated with PD and other diseases. In recent work, by using a combination of supervised machine learning and genome assembly, we identified a genome from a novel member of the Bacteroidetes phylum in periodontal samples. Here, by applying a comparative metagenomics read-classification approach, including 272 metagenomes from various human body sites, and our previously assembled draft genome of the uncultivated Candidatus Bacteroides periocalifornicus (CBP) bacterium, we show CBP's ubiquitous distribution in dental plaque, as well as its strong association with the well-known pathogenic "red complex" that resides in deep periodontal pockets.

Consistent responses of soil microbial taxonomic and functional attributes to mercury pollution across China

BACKGROUND

The ecological consequences of mercury (Hg) pollution-one of the major pollutants worldwide-on microbial taxonomic and functional attributes remain poorly understood and largely unexplored. Using soils from two typical Hg-impacted regions across China, here, we evaluated the role of Hg pollution in regulating bacterial abundance, diversity, and co-occurrence network. We also investigated the associations between Hg contents and the relative abundance of microbial functional genes by analyzing the soil metagenomes from a subset of those sites.

RESULTS

We found that soil Hg largely influenced the taxonomic and functional attributes of microbial communities in the two studied regions. In general, Hg pollution was negatively related to bacterial abundance, but positively related to the diversity of bacteria in two separate regions. We also found some consistent associations between soil Hg contents and the community composition of bacteria. For example, soil total Hg content was positively related to the relative abundance of Firmicutes and Bacteroidetes in both paddy and upland soils. In contrast, the methylmercury (MeHg) concentration was negatively correlated to the relative abundance of Nitrospirae in the two types of soils. Increases in soil Hg pollution correlated with drastic changes in the relative abundance of ecological clusters within the co-occurrence network of bacterial communities for the two regions. Using metagenomic data, we were also able to detect the effect of Hg pollution on multiple functional genes relevant to key soil processes such as element cycles and Hg transformations (e.g., methylation and reduction).

CONCLUSIONS

Together, our study provides solid evidence that Hg pollution has predictable and significant effects on multiple taxonomic and functional attributes including bacterial abundance, diversity, and the relative abundance of ecological clusters and functional genes. Our results suggest an increase in soil Hg pollution linked to human activities will lead to predictable shifts in the taxonomic and functional attributes in the Hg-impacted areas, with potential implications for sustainable management of agricultural ecosystems and elsewhere.

Fecal source identification using random forest

BACKGROUND

Clostridiales and Bacteroidales are uniquely adapted to the gut environment and have co-evolved with their hosts resulting in convergent microbiome patterns within mammalian species. As a result, members of Clostridiales and Bacteroidales are particularly suitable for identifying sources of fecal contamination in environmental samples. However, a comprehensive evaluation of their predictive power and development of computational approaches is lacking. Given the global public health concern for waterborne disease, accurate identification of fecal pollution sources is essential for effective risk assessment and management. Here, we use random forest algorithm and 16S rRNA gene amplicon sequences assigned to Clostridiales and Bacteroidales to identify common fecal pollution sources. We benchmarked the accuracy, consistency, and sensitivity of our classification approach using fecal, environmental, and artificial in silico generated samples.

RESULTS

Clostridiales and Bacteroidales classifiers were composed mainly of sequences that displayed differential distributions (host-preferred) among sewage, cow, deer, pig, cat, and dog sources. Each classifier correctly identified human and individual animal sources in approximately 90% of the fecal and environmental samples tested. Misclassifications resulted mostly from false-positive identification of cat and dog fecal signatures in host animals not used to build the classifiers, suggesting characterization of additional animals would improve accuracy. Random forest predictions were highly reproducible, reflecting the consistency of the bacterial signatures within each of the animal and sewage sources. Using in silico generated samples, we could detect fecal bacterial signatures when the source dataset accounted for as little as ~ 0.5% of the assemblage, with ~ 0.04% of the sequences matching the classifiers. Finally, we developed a proxy to estimate proportions among sources, which allowed us to determine which sources contribute the most to observed fecal pollution.

CONCLUSION

Random forest classification with 16S rRNA gene amplicons offers a rapid, sensitive, and accurate solution for identifying host microbial signatures to detect human and animal fecal contamination in environmental samples.

Burn injury alters the intestinal microbiome's taxonomic composition and functional gene expression

Burn patients have a high risk of sepsis-related mortality even after surviving the initial injury. Immunosuppression increases the risk of sepsis after burn injury, as does the disruption of the intestinal epithelial barrier, which allows the translocation of bacteria and bacterial products into the circulation. The integrity of the intestinal epithelial barrier is largely maintained by the intestinal microbiota. Burn injury has been reported to result in significant changes in the intestinal microbiome composition. In this mouse study, we confirm these taxonomic differences in a full-thickness scald injury model using CF-1 mice. For the first time, we also address alterations in functional gene expression of the intestinal microbiota after burn injury to assess the microbiome's physiological capabilities for overgrowth and pathogenic invasion: 38 pathways were differentially abundant between the sham and burn injury mice, including bacterial invasion of epithelial cells and gap- and adherens junction pathways.

Chryseolinea flava sp. nov., a new species of Chryseolinea isolated from soil

A pale yellow bacterial strain, designated SDU1-6^T, was isolated from a soil sample collected in the Jinan campus of Shandong University, Shandong Province, PR China. The strain was aerobic, motile, Gram-stain-negative and rod-shaped. Cellular growth occurred at 13-37 °C, pH 5.0-10.0 and with 0-0.1 % (w/v) NaCl, and the optimal growth was at 25 °C and pH 7.5. SDU1-6^T had the highest 16S rRNA gene similarity of 95.42 % with Chryseolinea serpens DSM 24574^T. The genome was 6 542 746 bp in length with 43.5 mol% DNA G+C content. The major fatty acids of SDU1-6^T were C16 : 1ω5 and iso-C15 : 0, the major menaquinone was menaquinone-7 (MK-7) and the major polar lipid was phosphatidylethanolamine. On the basis of the polyphasic evidence and the 16S rRNA gene sequence, SDU1-6^T represents a novel species of the genus Chryseolinea, for which the name Chryseolineaflava sp. nov. is proposed. The type strain is SDU1-6^T (=CGMCC 1.13492^T=JCM 32520^T).

Metagenomics reveals niche partitioning within the phototrophic zone of a microbial mat

Hypersaline photosynthetic microbial mats are stratified microbial communities known for their taxonomic and metabolic diversity and strong light-driven day-night environmental gradients. In this study of the upper photosynthetic zone of hypersaline microbial mats of Elkhorn Slough, California (USA), we show how metagenome sequencing can be used to meaningfully assess microbial ecology and genetic partitioning in these complex microbial systems. Mapping of metagenome reads to the dominant Cyanobacteria observed in the system, Coleofasciculus (Microcoleus) chthonoplastes, was used to examine strain variants within these metagenomes. Highly conserved gene subsystems indicated a core genome for the species, and a number of variant genes and subsystems suggested strain level differentiation, especially for nutrient utilization and stress response. Metagenome sequence coverage binning was used to assess ecosystem partitioning of remaining microbes to both reconstruct the model organisms in silico and identify their ecosystem functions as well as to identify novel clades and propose their role in the biogeochemical cycling of mats. Functional gene annotation of these bins (primarily of Proteobacteria, Bacteroidetes, and Cyanobacteria) recapitulated the known biogeochemical functions in microbial mats using a genetic basis, and revealed significant diversity in the Bacteroidetes, presumably in heterotrophic cycling. This analysis also revealed evidence of putative phototrophs within the Gemmatimonadetes and Gammaproteobacteria residing in microbial mats. This study shows that metagenomic analysis can produce insights into the systems biology of microbial ecosystems from a genetic perspective and to suggest further studies of novel microbes.