Tuft cells utilize taste signaling molecules to respond to the pathobiont microbe Ruminococcus gnavus in the proximal colon.

Tuft cells are a type of rare epithelial cells that have been recently found to utilize taste signal transduction pathways to detect and respond to various noxious stimuli and pathogens, including allergens, bacteria, protists and parasitic helminths. It is, however, not fully understood how many different types of pathogens they can sense or what exact molecular mechanisms they employ to initiate targeted responses. In this study, we found that an anaerobic pathobiont microbe, Ruminococcus gnavus (R. gnavus), can induce tuft cell proliferation in the proximal colon whereas the microbe's lysate can stimulate these proximal colonic tuft cells to release interleukin-25 (IL-25). Nullification of the Gng13 and Trpm5 genes that encode the G protein subunit Gγ13 and transient receptor potential ion channel Trpm5, respectively, or application of the Tas2r inhibitor allyl isothiocyanate (AITC), G protein Gßγ subunit inhibitor Gallein or the phospholipase Cß2 (PLCß2) inhibitor U73122 reduces R. gnavus-elicited tuft cell proliferation or IL-25 release or both. Furthermore, Gng13 conditional knockout or Trpm5 knockout diminishes the expression of gasdermins C2, C3 and C4, and concomitantly increases the activated forms of caspases 3, 8 and 9 as well as the number of TUNEL-positive apoptotic cells in the proximal colon. Together, our data suggest that taste signal transduction pathways are not only involved in the detection of R. gnavus infection, but also contribute to helping maintain gasdermin expression and prevent apoptotic cell death in the proximal colon, and these findings provide another strategy to combat R. gnavus infection and sheds light on new roles of taste signaling proteins along with gasdermins in protecting the integrity of the proximal colonic epithelium.

Pichia nanzhaoensis sp. nov. and Pichia paraexigua f.a., sp. nov., two yeast species isolated from rotting wood.

Four yeast strains were isolated from rotting wood samples collected in the Baotianman Nature Reserve in Henan Province, Central China. On the basis of sequence analysis of the D1/D2 domains of the large subunit rRNA gene and the internal transcribed spacer regions, they were suggested to be two novel species of the genus Pichia. Pichia nanzhaoensis sp. nov. produces one to four spherical ascospores per ascus, and is most closely related to Candida pseudolambica. Pichia paraexigua f.a., sp. nov. is a sister taxa to Pichia exigua, but the formation of ascospores was not observed on various sporulation media. P. nanzhaoensis sp. nov. can weakly assimilate inulin, whereas P. paraexigua sp. nov. can weakly assimilate d-glucosamine. The type strain of Pichia nanzhaoensis is NYNU 178136T (=CICC 33279T=CBS 15346T) and the type strain of Pichia paraexigua is NYNU 178135T (=CICC 33278T=CBS 15237T).

Yarrowia brassicae f.a., sp. nov., a new yeast species from traditional Chinese sauerkraut.

Two strains of a novel yeast species were isolated from traditional Chinese sauerkraut samples collected in Nanyang, Henan Province, central China. Phylogenetic analysis based on the concatenated sequences of the D1/D2 domains of the large subunit rRNA gene and the internal transcribed spacer (ITS) regions showed that these strains belong to the Yarrowia clade, with seven clones of uncultured Yarrowia as their closest phylogenetic neighbours. They differed from their closest known species, Yarrowia divulgata CBS 11013T, by 3.2 % sequence divergence (14 substitutions and 2 gaps) in the D1/D2 domains and by 5.4 % sequence divergence (12 substitutions and 5 gaps) in the ITS regions. The two strains of novel species reproduced asexually, and no ascospores could be found. The name Yarrowia brassicae f.a., sp. nov. is proposed to accommodate these strains, with NYNU 17218T (=CICC 33263T=CBS 15225T) as the type strain.

Deakozyma yunnanensis sp. nov., a novel yeast species isolated from rotten wood.

Three strains representing a novel yeast species were isolated from rotten wood samples collected in Xishuangbanna Tropical Rainforest in Yunnan Province, PR China. Sequence analysis of the D1/D2 domains of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) regions indicated that the novel species represented a member of the genus Deakozyma. The novel species was related most closely to the type strain of Deakozyma indianensis but they differed by 5.8 % sequence divergence (20 substitutions and 5 gaps) in the D1/D2 domain and by 12.2 % sequence divergence (27 substitutions and 15 gaps) in the ITS region. Interestingly, the novel yeast species was able to ferment glucose and sucrose in Durham tubes, a clear difference from its closest relative D. indianensis, the type species of the genus Deakozyma. The species name of Deakozyma yunnanensis sp. nov. is proposed to accommodate these strains, with NYNU 16742T (=CICC 33160T=CBS 14688T) designated the type strain. As the current description of the genus does not allow the inclusion of sugar fermenting species, the emendation of the diagnosis of the genus Deakozyma Kurtzman and Robnett is proposed.