Sporofaciens musculi gen. nov., sp. nov., a novel bacterium isolated from the caecum of an obese mouse

An Update on Novel Taxa and Revised Taxonomic Status of Bacteria Isolated from Domestic Animals Described in 2018 to 2021

Novel bacterial taxonomy and nomenclature revisions can have significant impacts on clinical practice, disease epidemiology, and veterinary microbiology laboratory operations. Expansion of research on the microbiota of humans, animals, and insects has significant potential impacts on the taxonomy of organisms of clinical interest. Implications of taxonomic changes may be especially important when considering zoonotic diseases. Here, we address novel taxonomy and nomenclature revisions of veterinary significance. Noteworthy discussion centers around descriptions of novel mastitis pathogens in Streptococcaceae, Staphylococcaceae, and Actinomycetaceae; bovine reproductive tract pathogens in Corynebacteriaceae; novel members of Mannheimia spp., Leptospira spp., and Mycobacterium spp.; the transfer of Ochrobactrum spp. to Brucella spp.; and revisions to the genus Mycoplasma.

A Novel Gene Alignment in Dorea sp. AM58-8 Produces 7-Dehydroxy-3β Bile Acids from Primary Bile Acids

Bile acids are essential metabolites and signaling molecules in mammals. Primary bile acids are synthesized from cholesterol in the liver. At the same time, the microbiota in the mammalian gut has many interactions with bile acid, including various biotransformation processes such as 7-dehydroxylation and 3-epimerization. 7-Dehydroxylation is mediated by a bile acid-inducible (bai) operon, while 7-dehydroxylation and 3-epimerization are independently observed in only a few strains. Herein, we describe a novel microbe, Dorea sp. AM58-8, that can accomplish a two-step transformation and turn primary bile acids into both 3α secondary bile acids like deoxycholic acid and lithocholic acid, and 3β secondary bile acids like isodeoxycholic acid and isolithocholic acid. We subsequently characterized BaiA, BaiB, BaiE, and their substrate profiles biochemically. The potential bai gene clusters in the metagenomes were further mined. Their evolution, potential functions, and possible regulatory pathways were predicted using bioinformatics based on our understanding of the 7-dehydroxylation pathway in Dorea sp. AM58-8. This study of Dorea sp. AM58-8 also helps us distinguish the inactive bacteria that seem to have the 7-dehydroxylation pathway proteins and discover the 7-dehydroxylation pathway in other mammalian gut microbes.

Antrihabitans stalagmiti sp. nov., isolated from a larva cave and a proposal to transfer Rhodococcus cavernicola Lee et al. 2020 to a new genus Spelaeibacter as Spelaeibacter cavernicola gen. nov. comb. nov

An actinobacterial strain, designated YC3-6^T, was isolated from a larva cave in Jeju, Republic of Korea. The novel isolate was found to grow at 10-30 °C, pH 5.0-10.0 and 0-4% (w/v) NaCl. The 16S rRNA gene phylogeny showed that the novel isolate formed a distinct subline within the family Nocardiaceae. Levels of 16S rRNA gene similarity indicated that the close relatives are Rhodococcus cavernicola (98.4% sequence similarity) and "Rhodococcus psychrotolerans" (98.2%) followed by Antrihabitans stalactiti (96.8%). However, the core gene-based phylogeny revealed that the novel isolate formed a tight cluster with A. stalactiti and was separated from R. cavernicola and other members of the family Nocardiaceae. The morphological and chemotaxonomic characteristics of strain YC3-6^T are in line with those of the genus Antrihabitans. Strain YC3-6^T showed an average nucleotide identity of 75.5% and a digital DDH of 20.3% with A. stalactiti. In addition, the core gene analysis showed that R. cavernicola formed a distinct subline between an Antrihabitans cluster and Aldersonia kunmingensis, and well separated from members of the genus Rhodococcus. The average amino acid identity values of R. cavernicola to closely related neighbours were 69.3-69.4% with members of the genus Antrihabitans and 67.3% with Ald. kunmingensis, while the POCP values ranged from 56.9 to 63.6%. On the basis of results obtained here, strain YC3-6^T is concluded to represent a novel species of the genus Antrihabitans, for which the name Antrihabitans stalagmiti sp. nov. (type strain, YC3-6^T = KACC 19963^T = DSM 107561^T) is proposed. Based on overall genome relatedness and chemotaxonomic differences, it is also proposed that R. cavernicola Lee et al. 2020 be transferred to a new genus Spelaeibacter as Spelaeibacter cavernicola gen. nov., comb. nov.

Comparative Genomic and Physiological Analysis against Clostridium scindens Reveals Eubacterium sp. c-25 as an Atypical Deoxycholic Acid Producer of the Human Gut Microbiota

The human gut houses bile acid 7α-dehydroxylating bacteria that produce secondary bile acids such as deoxycholic acid (DCA) from host-derived bile acids through enzymes encoded by the bai operon. While recent metagenomic studies suggest that these bacteria are highly diverse and abundant, very few DCA producers have been identified. Here, we investigated the physiology and determined the complete genome sequence of Eubacterium sp. c-25, a DCA producer that was isolated from human feces in the 1980s. Culture experiments showed a preference for neutral to slightly alkaline pH in both growth and DCA production. Genomic analyses revealed that c-25 is phylogenetically distinct from known DCA producers and possesses a multi-cluster arrangement of predicted bile-acid inducible (bai) genes that is considerably different from the typical bai operon structure. This arrangement is also found in other intestinal bacterial species, possibly indicative of unconfirmed 7α-dehydroxylation capabilities. Functionality of the predicted bai genes was supported by the induced expression of baiB, baiCD, and baiH in the presence of cholic acid substrate. Taken together, Eubacterium sp. c-25 is an atypical DCA producer with a novel bai gene cluster structure that may represent an unexplored genotype of DCA producers in the human gut.

Different Reactions in Each Enterotype Depending on the Intake of Probiotic Yogurt Powder

Probiotics can be used as a nutritional strategy to improve gut homeostasis. We aimed to evaluate the intestinal microbiota profile of 18 subjects after ingestion of probiotic yogurt powder (PYP) based on enterotype. The subjects were classified into three enterotypes according to their microbial community: Bacteroides (n = 9, type B), Prevotella (n = 3, type P), and Ruminococcus (n = 6, type R). We performed controlled termination in a transient series that included a control period of three weeks before probiotic intake, PYP intake for three weeks, and a three-week washout period. Fecal microbiota composition was analyzed by sequencing the V3-V4 super variable region of 16S rRNA. Based on the Bristol stool shape scale, abnormal stool shape improved with PYP intake, and bowel movements were activated. The abundance of Faecalibacterium, Eggerthella, and Leuconostoc, which ferment and metabolize glucose, showed a strong correlation with type B Bacteroides, and glucose metabolism improvement was observed in all type B subjects. Alkaline phosphatase was significantly improved only in type B. In addition, the abundance of type B Bacteroides showed a negative correlation with that of Lactobacillus. The abundance of Streptococcus, Agathobacter, and Christensenella, which are involved in lipid metabolism, showed a strong correlation with that of type P Prevotella, and triglyceride metabolism improvement was observed in all type P subjects. The gut microbiota showed only short-term changes after PYP intake and showed resilience by returning to its original state when PYP intake was interrupted. In summary, the different responses to PYP intake may result from the different enterotypes and associated strains; therefore, the probiotic composition should be adjusted based on the individual enterotype.