A cryptic plasmid is among the most numerous genetic elements in the human gut.

Plasmids are extrachromosomal genetic elements that often encode fitness-enhancing features. However, many bacteria carry "cryptic" plasmids that do not confer clear beneficial functions. We identified one such cryptic plasmid, pBI143, which is ubiquitous across industrialized gut microbiomes and is 14 times as numerous as crAssphage, currently established as the most abundant extrachromosomal genetic element in the human gut. The majority of mutations in pBI143 accumulate in specific positions across thousands of metagenomes, indicating strong purifying selection. pBI143 is monoclonal in most individuals, likely due to the priority effect of the version first acquired, often from one's mother. pBI143 can transfer between Bacteroidales, and although it does not appear to impact bacterial host fitness in vivo, it can transiently acquire additional genetic content. We identified important practical applications of pBI143, including its use in identifying human fecal contamination and its potential as an alternative approach to track human colonic inflammatory states.

Strain-level fitness in the gut microbiome is an emergent property of glycans and a single metabolite.

The human gut microbiota resides within a diverse chemical environment challenging our ability to understand the forces shaping this ecosystem. Here, we reveal that fitness of the Bacteroidales, the dominant order of bacteria in the human gut, is an emergent property of glycans and one specific metabolite, butyrate. Distinct sugars serve as strain-variable fitness switches activating context-dependent inhibitory functions of butyrate. Differential fitness effects of butyrate within the Bacteroides are mediated by species-level variation in Acyl-CoA thioesterase activity and nucleotide polymorphisms regulating an Acyl-CoA transferase. Using in vivo multi-omic profiles, we demonstrate Bacteroides fitness in the human gut is associated together, but not independently, with Acyl-CoA transferase expression and butyrate. Our data reveal that each strain of the Bacteroides exists within a unique fitness landscape based on the interaction of chemical components unpredictable by the effect of each part alone mediated by flexibility in the core genome.

Transient Osmotic Perturbation Causes Long-Term Alteration to the Gut Microbiota.

Osmotic diarrhea is a prevalent condition in humans caused by food intolerance, malabsorption, and widespread laxative use. Here, we assess the resilience of the gut ecosystem to osmotic perturbation at multiple length and timescales using mice as model hosts. Osmotic stress caused reproducible extinction of highly abundant taxa and expansion of less prevalent members in human and mouse microbiotas. Quantitative imaging revealed decimation of the mucus barrier during osmotic perturbation, followed by recovery. The immune system exhibited temporary changes in cytokine levels and a lasting IgG response against commensal bacteria. Increased osmolality prevented growth of commensal strains in vitro, revealing one mechanism contributing to extinction. Environmental availability of microbiota members mitigated extinction events, demonstrating how species reintroduction can affect community resilience. Our findings (1) demonstrate that even mild osmotic diarrhea can cause lasting changes to the microbiota and host and (2) lay the foundation for interventions that increase system-wide resilience.

Extensive strain-level copy-number variation across human gut microbiome species.

Within each bacterial species, different strains may vary in the set of genes they encode or in the copy number of these genes. Yet, taxonomic characterization of the human microbiota is often limited to the species level or to previously sequenced strains, and accordingly, the prevalence of intra-species variation, its functional role, and its relation to host health remain unclear. Here, we present a comprehensive large-scale analysis of intra-species copy-number variation in the gut microbiome, introducing a rigorous computational pipeline for detecting such variation directly from shotgun metagenomic data. We uncover a large set of variable genes in numerous species and demonstrate that this variation has significant functional and clinically relevant implications. We additionally infer intra-species compositional profiles, identifying population structure shifts and the presence of yet uncharacterized variants. Our results highlight the complex relationship between microbiome composition and functional capacity, linking metagenome-level compositional shifts to strain-level variation.

Structural color in the bacterial domain: The ecogenomics of a 2-dimensional optical phenotype.

Structural color is an optical phenomenon resulting from light interacting with nanostructured materials. Although structural color (SC) is widespread in the tree of life, the underlying genetics and genomics are not well understood. Here, we collected and sequenced a set of 87 structurally colored bacterial isolates and 30 related strains lacking SC. Optical analysis of colonies indicated that diverse bacteria from at least two different phyla (Bacteroidetes and Proteobacteria) can create two-dimensional packing of cells capable of producing SC. A pan-genome-wide association approach was used to identify genes associated with SC. The biosynthesis of uroporphyrin and pterins, as well as carbohydrate utilization and metabolism, was found to be involved. Using this information, we constructed a classifier to predict SC directly from bacterial genome sequences and validated it by cultivating and scoring 100 strains that were not part of the training set. We predicted that SCr is widely distributed within gram-negative bacteria. Analysis of over 13,000 assembled metagenomes suggested that SC is nearly absent from most habitats associated with multicellular organisms except macroalgae and is abundant in marine waters and surface/air interfaces. This work provides a large-scale ecogenomics view of SC in bacteria and identifies microbial pathways and evolutionary relationships that underlie this optical phenomenon.

Arsenate reductase of Rufibacter tibetensis is a metallophosphoesterase evolved to catalyze redox reactions.

An arsenate reductase (Car1) from the Bacteroidetes species Rufibacter tibetensis 1351T was isolated from the Tibetan Plateau. The strain exhibits resistance to arsenite [As(III)] and arsenate [As(V)] and reduces As(V) to As(III). Here we shed light on the mechanism of enzymatic reduction by Car1. AlphaFold2 structure prediction, active site energy minimization, and steady-state kinetics of wild-type and mutant enzymes give insight into the catalytic mechanism. Car1 is structurally related to calcineurin-like metallophosphoesterases (MPPs). It functions as a binuclear metal hydrolase with limited phosphatase activity, particularly relying on the divalent metal Ni2+. As an As(V) reductase, it displays metal promiscuity and is coupled to the thioredoxin redox cycle, requiring the participation of two cysteine residues, Cys74 and Cys76. These findings suggest that Car1 evolved from a common ancestor of extant phosphatases by incorporating a redox function into an existing MPP catalytic site. Its proposed mechanism of arsenate reduction involves Cys74 initiating a nucleophilic attack on arsenate, leading to the formation of a covalent intermediate. Next, a nucleophilic attack of Cys76 leads to the release of As(III) and the formation of a surface-exposed Cys74-Cys76 disulfide, ready for reduction by thioredoxin.

Human gut bacteria contain acquired interbacterial defence systems.

The human gastrointestinal tract consists of a dense and diverse microbial community, the composition of which is intimately linked to health. Extrinsic factors such as diet and host immunity are insufficient to explain the constituents of this community, and direct interactions between co-resident microorganisms have been implicated as important drivers of microbiome composition. The genomes of bacteria derived from the gut microbiome contain several pathways that mediate contact-dependent interbacterial antagonism1-3. Many members of the Gram-negative order Bacteroidales encode the type VI secretion system (T6SS), which facilitates the delivery of toxic effector proteins into adjacent cells4,5. Here we report the occurrence of acquired interbacterial defence (AID) gene clusters in Bacteroidales species that reside within the human gut microbiome. These clusters encode arrays of immunity genes that protect against T6SS-mediated intra- and inter-species bacterial antagonism. Moreover, the clusters reside on mobile elements, and we show that their transfer is sufficient to confer resistance to toxins in vitro and in gnotobiotic mice. Finally, we identify and validate the protective capability of a recombinase-associated AID subtype (rAID-1) that is present broadly in Bacteroidales genomes. These rAID-1 gene clusters have a structure suggestive of active gene acquisition and include predicted immunity factors of toxins derived from diverse organisms. Our data suggest that neutralization of contact-dependent interbacterial antagonism by AID systems helps to shape human gut microbiome ecology.

Transcriptomic analysis of polysaccharide utilization loci reveals substrate preferences in ruminal generalists Segatella bryantii TF1-3 and Xylanibacter ruminicola KHP1.

Bacteria of the genera Xylanibacter and Segatella are among the most dominant groups in the rumen microbiota. They are characterized by the ability to utilize different hemicelluloses and pectin of plant cell-wall as well as plant energy storage polysaccharides. The degradation is possible with the use of cell envelope bound multiprotein apparatuses coded in polysaccharide utilization loci (PULs), which have been shown to be substrate specific. The knowledge of PUL presence in rumen Xylanibacter and Segatella based on bioinformatic analyses is already established and transcriptomic and genetic approaches confirmed predicted PULs for a limited number of substrates. In this study, we transcriptomically identified additional different PULs in Xylanibacter ruminicola KHP1 and Segatella bryantii TF1-3. We also identified substrate preferences and found that specific growth rate and extent of growth impacted the choice of substrates preferentially used for degradation. These preferred substrates were used by both strains simultaneously as judged by their PUL upregulation. Lastly, ß-glucan and xyloglucan were used by these strains in the absence of bioinformatically and transcriptomically identifiable PUL systems.

Unveiling the role of novel carbohydrate-binding modules in laminarin interaction of multimodular proteins from marine Bacteroidota during phytoplankton blooms.

Laminarin, a ß(1,3)-glucan, serves as a storage polysaccharide in marine microalgae such as diatoms. Its abundance, water solubility and simple structure make it an appealing substrate for marine bacteria. Consequently, many marine bacteria have evolved strategies to scavenge and decompose laminarin, employing carbohydrate-binding modules (CBMs) as crucial components. In this study, we characterized two previously unassigned domains as laminarin-binding CBMs in multimodular proteins from the marine bacterium Christiangramia forsetii KT0803T, thereby introducing the new laminarin-binding CBM families CBM102 and CBM103. We identified four CBM102s in a surface glycan-binding protein (SGBP) and a single CBM103 linked to a glycoside hydrolase module from family 16 (GH16_3). Our analysis revealed that both modular proteins have an elongated shape, with GH16_3 exhibiting greater flexibility than SGBP. This flexibility may aid in the recognition and/or degradation of laminarin, while the constraints in SGBP could facilitate the docking of laminarin onto the bacterial surface. Exploration of bacterial metagenome-assembled genomes (MAGs) from phytoplankton blooms in the North Sea showed that both laminarin-binding CBM families are widespread among marine Bacteroidota. The high protein abundance of CBM102- and CBM103-containing proteins during phytoplankton blooms further emphasizes their significance in marine laminarin utilization.

Environmental control and metabolic strategies of organic-matter-responsive bacterioplankton in the Weddell Sea (Antarctica).

Heterotrophic microbial communities play a significant role in driving carbon fluxes in marine ecosystems. Despite their importance, these communities remain understudied in remote polar oceans, which are known for their substantial contribution to the biological drawdown of atmospheric carbon dioxide. Our research focused on understanding the environmental factors and genetic makeup of key bacterial players involved in carbon remineralization in the Weddell Sea, including its coastal polynyas. Our experiments demonstrated that the combination of labile organic matter supply and temperature increase synergistically boosted bacterial growth. This suggests that, besides low seawater temperature, carbon limitation also hinders heterotrophic bacterial activity. Through the analysis of metagenome-assembled genomes, we discovered distinct genomic adaptation strategies in Bacteroidia and Gammaproteobacteria, both of which respond to organic matter. Both natural phytoplankton blooms and experimental addition of organic matter favoured Bacteroidia, which possess a large number of gene copies and a wide range of functional membrane transporters, glycoside hydrolases, and aminopeptidases. In contrast, the genomes of organic-matter-responsive Gammaproteobacteria were characterized by high densities of transcriptional regulators and transporters. Our findings suggest that bacterioplankton in the Weddell Sea, which respond to organic matter, employ metabolic strategies similar to those of their counterparts in temperate oceans. These strategies enable efficient growth at extremely low seawater temperatures, provided that organic carbon limitation is alleviated.

Metagenome-derived SusD-homologs affiliated with Bacteroidota bind to synthetic polymers.

Starch utilization system (Sus)D-homologs are well known for their carbohydrate-binding capabilities and are part of the sus operon in microorganisms affiliated with the phylum Bacteroidota. Until now, SusD-like proteins have been characterized regarding their affinity toward natural polymers. In this study, three metagenomic SusD homologs (designated SusD1, SusD38489, and SusD70111) were identified and tested with respect to binding to natural and non-natural polymers. SusD1 and SusD38489 are cellulose-binding modules, while SusD70111 preferentially binds chitin. Employing translational fusion proteins with superfolder GFP (sfGFP), pull-down assays, and surface plasmon resonance (SPR) has provided evidence for binding to polyethylene terephthalate (PET) and other synthetic polymers. Structural analysis suggested that a Trp triad might be involved in protein adsorption. Mutation of these residues to Ala resulted in an impaired adsorption to microcrystalline cellulose (MC), but not so to PET and other synthetic polymers. We believe that the characterized SusDs, alongside the methods and considerations presented in this work, will aid further research regarding bioremediation of plastics. IMPORTANCE: SusD1 and SusD38489 can be considered for further applications regarding their putative adsorption toward fossil-fuel based polymers. This is the first time that SusD homologs from the polysaccharide utilization loci (PUL), largely described for the phylum Bacteroidota, are characterized as synthetic polymer-binding proteins.

Characteristics of gut microbiota in patients with asthenozoospermia: a Chinese pilot study.

BACKGROUND: Identification of intestinal flora composition is significant for exploring the cause and pathogenic mechanisms of the gut-testis axis and clarifying the relationship between microbiota and infertility. Our study aimed to examine the alternation in gut microbiota composition and identify potential microbes associated with development of Asthenozoospermia (AS). METHOD: A total of 580 males were recruited in the outpatient department of Tianjin Medical University General Hospital between September 2021 and March 2023. Sperm parameters were analyzed according to the WHO laboratory manual. The 16 S rRNA gene high-throughput sequencing was performed to detect the gut microbiota composition in fecal samples. LEfSe analysis was used to screen key microbiota. PICRUSt2 software was utilized to predict relevant pathways. RESULTS: After rigorous screening, 60 isolated AS patients (AS group) and 48 healthy men (NC group) were enrolled. No significant differences were observed in demographic characteristics (p > 0.05), semen volume (p = 0.718), sperm concentration (p = 0.109), or total sperm count (p = 0.200). Sperm total motility and progressive motility were significantly decreased in the AS group (p < 0.001). AS patients had significantly lower alpha diversity indices (Chao1, observed OTUs, and PD Whole-tree; p < 0.05). The beta-diversity of gut microbiota in AS patients significantly differed from NC men (PCoA analysis, p = 0.001). Firmicutes, Bacteroidota, Proteobacteria, and Actinobacteria were the primary phyla, with the dominant genera including Bacteroides, Prevotella, and Blautia. Eleven key genera such as Escherichia_Shigella and Prevotellaceae_UCG_001 were identified by LEfSe analysis. Most of these genera were negatively correlated with sperm mobility. Eighty-eight KEGG pathways, including steroid biosynthesis and meiosis, were significantly enriched between the two groups. CONCLUSIONS: It appears that gut microbiota composition in AS patients significantly differed from that in healthy men, and the development of AS might be associated with intestinal flora dysbiosis.

Comparative genome analysis of the genus Marivirga and proposal of two novel marine species: Marivirga arenosa sp. nov., and Marivirga salinae sp. nov.

BACKGROUND: The phylum Bacteroidota represents a significant proportion of heterotrophic bacteria found in marine ecosystems. Members of the phylum Bacteroidota are actively involved in the degradation of biopolymers such as polysaccharides and proteins. Bacteroidota genomes exhibit a significant enrichment of various enzymes, including carbohydrate-active enzymes (CAZymes), carboxypeptidases, esterases, isomerases, peptidases, phosphatases, and sulfatases. The genus Marivirga, a member of the family Marivirgaceae within the phylum Bacteroidota, comprises six documented species. During a microbial diversity study, three novel Marivirga strains (BKB1-2 T, ABR2-2, and BDSF4-3 T) were isolated from the West Sea, Republic of Korea. RESULTS: To explore the taxonomic status and genomic characteristics of the novel isolates, we employed a polyphasic taxonomic approach, which included phylogenetic, chemotaxonomic and comprehensive genome analysis. The three isolates were Gram-stain-negative, aerobic, rod-shaped, moderately halophilic, and had a gliding motility. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values among the two isolates, BKB1-2 T and BDSF4-3 T, and the six reference strains were 70.5-76.5% for ANI and 18.1-25.7% for dDDH. Interestingly, the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the strains harbor genes for a comprehensive pathway for dissimilatory nitrate reduction to ammonium (DNRA), as well as other nitrogen pathways for the reduction of nitrite, nitric oxide, and nitrous oxide. Additionally, the antiSMASH analysis indicated that the strains contained three to eight biosynthetic gene clusters (BGCs) associated with the synthesis of secondary metabolites. Furthermore, the strains carried a high number of CAZyme ranging from 53 to 152, which was also demonstrated by an in vitro analysis of degradation of the polysaccharide cellulose, chitin, laminarin, starch, and xylan. Additionally, all the strains carried genes for the metabolism of heavy metals, and exhibited tolerance to heavy metals, with minimum inhibitory concentrations (MICs) in millimoles (mM) in ranges of Co2+ (3-6), Cu2+ (0.2-0.4), Ni2+ (3-5), Zn2+ (2-4), Mn2+ (20-50), and Hg2+ (0.3). CONCLUSIONS: Based on polyphasic taxonomic approach, the three isolated strains represent two novel species names Marivirga arenosa sp. nov. (BKB1-2 T = KCTC 82989 T = InaCC B1618T), and Marivirga salinae sp. nov. (BDSF4-3 T = KCTC 82973 T = InaCC B1619T).

Gut microbiota composition and changes in patients with sepsis: potential markers for predicting survival.

BACKGROUND: Sepsis can cause immune dysregulation and multiple organ failure in patients and eventually lead to death. The gut microbiota has demonstrated its precise therapeutic potential in the treatment of various diseases. This study aimed to discuss the structural changes of the gut microbiota in patients with sepsis and to analyze the differences in the gut microbiota of patients with different prognoses. METHODS: We conducted a multicenter study in which rectal swab specimens were collected on the first and third days of sepsis diagnosis. A total of 70 specimens were collected, and gut microbiota information was obtained by 16S rRNA analysis. RESULTS: The relative abundance of Enterococcus decreased in rectal swab specimens during the first three days of diagnosis in patients with sepsis, while the relative abundance of inflammation-associated Bacillus species such as Escherichia coli, Enterobacteriaceae, and Bacteroidetes increased. By comparing the differences in the flora of the survival group and the death group, we found that the abundance of Veillonella and Ruminococcus in the death group showed an increasing trend (p < 0.05), while the abundance of Prevotella_6 and Prevotella_sp_S4_BM14 was increased in surviving patients (p < 0.05). CONCLUSIONS: The Firmicutes/Bacteroidetes ratio, reflecting overall gut microbial composition, was significantly lower on day three of sepsis diagnosis. Changes in the abundance of specific gut microbiota may serve as prognostic markers in patients with sepsis.

Correlation of gut microbial diversity to sight-threatening diabetic retinopathy.

PURPOSE: To determine the association of gut microbiome diversity and sight-threatening diabetic retinopathy (STDR) amongst patients with pre-existing diabetes. METHODS: A cross-sectional study was performed, wherein 54 participants selected in total were placed into cases cohort if diagnosed with STDR and those without STDR but had a diagnosis of diabetes mellitus of at least 10-year duration were taken as controls. Statistical analysis comparing the gut microbial alpha diversity between cases and control groups as well as patients differentiated based on previously hypothesized Bacteroidetes/Firmicutes(B/F) ratio with an optimal cut-off 1.05 to identify patients with STDR were performed. RESULTS: Comparing gut microbial alpha diversity did not show any difference between cases and control groups. However, statistically significant difference was noted amongst patients with B/F ratio ≥1.05 when compared to B/F ratio < 1.05; ACE index [Cut-off < 1.05:773.83 ± 362.73; Cut-off > 1.05:728.03 ± 227.37; p-0.016]; Chao1index [Cut-off < 1.05:773.63 ± 361.88; Cut-off > 1.05:728.13 ± 227.58; p-0.016]; Simpson index [Cut-off < 1.05:0.998 ± 0.001; Cut-off > 1.05:0.997 ± 0.001; p-0.006]; Shannon index [Cut-off < 1.05:6.37 ± 0.49; Cut-off > 1.05:6.10 ± 0.43; p-0.003]. Sub-group analysis showed that cases with B/F ratio ≥ 1.05, divided into proliferative diabetic retinopathy (PDR) and clinically significant macular edema (CSME), showed decreased diversity compared to controls (B/F ratio < 1.05). For PDR, all four diversity indices significantly decreased (p < 0.05). However, for CSME, only Shannon and Simpson indices showed significant decrease in diversity (p < 0.05). CONCLUSIONS: Based on clinical diagnosis, decreasing gut microbial diversity was observed among patients with STDR, although not statistically significant. When utilizing B/F ratio, the decreasing gut microbial diversity in STDR patients seems to be associated due to species richness and evenness in PDR when compared to decreasing species richness in CSME.

Gut microbiota Parabacteroides distasonis enchances the efficacy of immunotherapy for bladder cancer by activating anti-tumor immune responses.

OBJECTIVE: Bladder cancer(BCa) was a disease that seriously affects patients' quality of life and prognosis. To address this issue, many researches suggested that the gut microbiota modulated tumor response to treatment; however, this had not been well-characterized in bladder cancer. In this study, our objective was to determine whether the diversity and composition of the gut microbiota or the density of specific bacterial genera influence the prognosis of patients with bladder cancer. METHODS: We collected fecal samples from a total of 50 bladder cancer patients and 22 matched non-cancer individuals for 16S rDNA sequencing to investigate the distribution of Parabacteroides in these two groups. Further we conducted follow-up with cancer patients to access the impact of different genera of microorganisms on patients survival. We conducted a Fecal Microbiota Transplantation (FMT) and mono-colonization experiment with Parabacteroides distasonis to explore its potential enhancement of the efficacy of anti-PD-1 immunotherapy in MB49 tumor-bearing mice. Immunohistochemistry, transcriptomics and molecular experiment analyses were employed to uncover the underlying mechanisms. RESULTS: The 16S rDNA showed that abundance of the genus Parabacteroides was elevated in the non-cancer control group compared to bladder cancer group. The results of tumor growth curves showed that a combination therapy of P. distasonis and ICIs treatment significantly delayed tumor growth and increased the intratumoral densities of both CD4+T and CD8+T cells. The results of transcriptome analysis demonstrated that the pathways associated with antitumoral immune response were remarkably upregulated in the P. distasonis gavage group. CONCLUSION: P. distasonis delivery combined with α-PD-1 mAb could be a new strategy to enhance the effect of anti-PD-1 immunotherapy. This effect might be achieved by activating immune and antitumor related pathways.

Alteration of the gut microbiome in patients with heart failure: A systematic review and meta-analysis.

Recent research has revealed that alterations of the gut microbiome (GM) play a comprehensive role in the pathophysiology of HF. However, findings in this field remain controversial. In this study, we focus on differences in GM diversity and abundance between HF patients and non-HF people, based on previous 16 S ribosomal RNA (16rRNA) gene sequencing. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a comprehensive search of PubMed, Web of Science, Embase, Cochrane Library, and Ovid databases using the keyword "Heart failure" and "Gastrointestinal Microbiome". A significant decrease in alpha diversity was observed in the HF patients (Chao1, I2 = 87.5 %, p < 0.001; Shannon index, I2 = 62.8 %, p = 0.021). At the phylum level, the HF group exhibited higher abundances of Proteobacteria (I2 = 92.0 %, p = 0.004) and Actinobacteria (I2 = 82.5 %, p = 0.010), while Bacteroidetes (I2 = 45.1 %, p = 0.017) and F/B ratio (I2 = 0.0 %, p＜0.001) were lower. The Firmicutes showed a decreasing trend but did not reach statistical significance (I2 = 82.3 %, p = 0.127). At the genus level, the relative abundances of Streptococcus, Bacteroides, Alistipes, Bifidobacterium, Escherichia-Shigella, Enterococcus and Klebsiella were increased in the HF group, whereas Ruminococcus, Faecalibacterium, Dorea and Megamona exhibited decreased relative abundances. Dialister, Blautia and Prevotella showed decreasing trends but without statistical significance. This observational meta-analysis suggests that GM changes are associated with HF, manifesting as alterations in GM abundance, disruptions in the production of short-chain fatty acids (SCFAs) bacteria, and an increase in trimethylamine N-oxide (TMAO) producing bacteria.

Impact of wheat processing on growth, serum biochemistry, and ruminal microbiota in sheep (Ovis aries).

This study investigated the impact of wheat processing methods (wheat flour vs wheat pellets) on the growth performance, serum biochemical parameters, and rumen microbiome composition in sheep. Results indicated that feeding of wheat flour resulted in significantly higher terminal weight and average daily gain (P < 0.05) and lower cholesterol and ALP04 levels (P < 0.05) in sheep compared to those fed wheat pellets. Analysis of 16s rDNA high-throughput sequencing data revealed significantly higher microbial richness (Chao1 index) in the rumen of sheep fed wheat flour (P < 0.05), even though the phylum-level composition dominated by Firmicutes, Bacteroidetes, and Proteobacteria was similar in both groups of sheep. Notably, sheep fed wheat flour were found to have a significantly higher relative abundance of Bacteroidetes (P < 0.05). At the genus level, Succinivibrionaceae_UCG-001 and Prevotella_1 were significantly more abundant in the rumen of sheep fed wheat flour (P < 0.05). Correlation analysis identified that both terminal weight and average daily gain were positively correlated with ruminal abundance of Bacteroidetes and Prevotella_1, while ALP04 was negatively correlated with the abundance of these taxa. Functional prediction using PICRUSt2 indicated enrichment of pathways related to the ABC-type glycerol-3-phosphate transport system, and periplasmic components in both wheat flour and pellet fed sheep. Overall, these findings suggest that dietary wheat flour modulates rumen microbiota composition, and improves growth performance in sheep.

Splendidivirga corallicola gen. nov., sp. nov. and Agaribacillus aureus gen. nov., sp. nov., two bacteria isolated from coral Porites lutea, and proposal of Splendidivirgaceae fam. nov.

The Bacteroidota is one of the dominant bacterial phyla in corals. However, the exact taxa of those coral bacteria under the Bacteroidota are still unclear. Two aerobic, Gram-stain-negative, non-motile rods, designated strains BMA10T and BMA12T, were isolated from stony coral Porites lutea collected from Weizhou Island, PR China. Global alignment of 16S rRNA gene sequences indicated that both strains are closest to species of Fulvivirga with the highest identities being lower than 93 %, and the similarity value between these two strains was 92.3 %. Phylogenetic analysis based on 16S rRNA gene and genome sequences indicated that these two strains form an monophylogenetic lineage alongside the families Fulvivirgaceae, Reichenbachiellaceae, Roseivirgaceae, Marivirgaceae, Cyclobacteriaceae, and Cesiribacteraceae in the order Cytophagales, phylum Bacteroidota. The genomic DNA G+C contents of BMA10T and BMA12T were 38.4 and 41.9 mol%, respectively. The major polar lipids of BMA10T were phosphatidylethanolamine, unidentified aminophospholipid, four unidentified aminolipids, and five unidentified lipids. While those of BMA12T were phosphatidylethanolamine, two unidentified aminolipids, and five unidentified lipids. The major cellular fatty acids detected in both isolates were iso-C15 : 0 and C16 : 1 ω5c. Carbohydrate-active enzyme analysis indicated these two strains may utilize coral mucus or chitin. Based on above characteristics, these two strains are suggested to represent two new species in two new genera of a new family in the order Cytophagales, for which the name Splendidivirga corallicola gen. nov., sp. nov., Agaribacillus aureus gen. nov., sp. nov. and Splendidivirgaceae fam. nov. are proposed. The type strain of S. corallicola is BMA10T (=MCCC 1K08300T=KCTC 102045T), and that for A. aureus is BMA12T (=MCCC 1K08309T=KCTC 102046T).

Polaribacter ponticola sp. nov., isolated from seawater, reclassification of Polaribacter undariae as a later heterotypic synonym of Polaribacter sejongensis, and emended description of Polaribacter sejongensis Kim et al. 2013.

A Gram-stain-negative, yellow-pigmented, and strictly aerobic bacterium, designated as strain MSW5T, was isolated from seawater of the Yellow Sea in South Korea. The cells were non-motile rods exhibiting oxidase- and catalase-positive activities. Growth was observed at 15-25 °C (optimum, 25 °C) and pH 5.0-9.0 (optimum, pH 7.0-8.0) and in the presence of 1.0-5.0% (w/v) NaCl (optimum, 2.0%). Menaquinone-6 was the sole respiratory quinone, and iso-C15 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), iso-C15 : 0 3-OH, and C15 : 1 ω6c were the major cellular fatty acids. Major polar lipids included phosphatidylethanolamine, two unidentified aminolipids, and three unidentified lipids. Phylogenetic analyses based on 16S rRNA gene sequences and 92 concatenated core protein sequences revealed that strain MSW5T formed a distinct lineage within the genus Polaribacter. The genome of strain MSW5T was 3582 kb in size with a 29.1 mol% G+C content. Strain MSW5T exhibited the highest similarity to Polaribacter atrinae WP25T, with a 97.9% 16S rRNA gene sequence similarity. However, the average nucleotide identity and digital DNA-DNA hybridization values were 79.4 and 23.3%, respectively, indicating that strain MSW5T represents a novel species. Based on its phenotypic, chemotaxonomic, and phylogenetic characteristics, strain MSW5T is proposed to represent a novel species, with the name Polaribacter ponticola sp. nov. The type strain is MSW5T (=KACC 22340T=NBRC 116025T). In addition, whole genome sequence comparisons and phenotypic features suggested that Polaribacter sejongensis and Polaribacter undariae belong to the same species, with P. undariae proposed as a later heterotypic synonym of P. sejongensis. An emended description of Polaribacter sejongensis is also proposed.