Microbiology

Soil bacteria have been investigated for more than a century, but one of the most dominant terrestrial groups on Earth, “ Candidatus Udaeobacter,” remains elusive and largely unexplored. Its natural habitat is considered a major reservoir of antibiotics, which directly or indirectly impact phylogenetically diverse microorganisms. Here, we found that “ Ca. Udaeobacter” representatives exhibit multidrug resistance and not only evade harmful effects of antimicrobials but even benefit from antibiotic pressure in soil. Therefore, “ Ca. Udaeobacter” evidently affects the composition of soil resistomes worldwide and might represent a winner of rising environmental pollution with antimicrobials. In addition, our study indicates that “ Ca. Udaeobacter” representatives utilize H 2 and thereby contribute to global hydrogen cycling. The here-reported findings provide insights into elementary lifestyle features of “ Ca. Udaeobacter,” potentially contributing to its successful global dissemination.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

We here present annotated lists of names ofCandidatustaxa of prokaryotes with ranks between subspecies and class, proposed between the mid-1990s, when the provisional status ofCandidatustaxa was first established, and the end of 2018. Where necessary, corrected names are proposed that comply with the current provisions of the International Code of Nomenclature of Prokaryotes and its Orthography appendix. These lists, as well as updated lists of newly published names ofCandidatustaxa with additions and corrections to the current lists to be published periodically in theInternational Journal of Systematic and Evolutionary Microbiology, may serve as the basis for the valid publication of theCandidatusnames if and when the current proposals to expand the type material for naming of prokaryotes to also include gene sequences of yet-uncultivated taxa is accepted by the International Committee on Systematics of Prokaryotes.

Recently, we isolated two marine strains, F1T and F21T, which together with Kiritimatiella glycovorans L21-Fru-ABT are the only pure cultures of the class Kiritimatiellae within the phylum Verrucomicrobiota. Here, we present an in-depth genome-guided characterization of both isolates with emphasis on their exopolysaccharide synthesis. The strains only grew fermentatively on simple carbohydrates and sulfated polysaccharides. Strains F1T, F21T and K. glycovorans reduced elemental sulfur, ferric citrate and anthraquinone-2,6-disulfonate during anaerobic growth on sugars. Both strains produced exopolysaccharides during stationary phase, probably with intracellularly stored glycogen as energy and carbon source. Exopolysaccharides included N-sulfated polysaccharides probably containing hexosamines and thus resembling glycosaminoglycans. This implies that the isolates can both degrade and produce sulfated polysaccharides. Both strains encoded an unprecedently high number of glycoside hydrolase genes (422 and 388, respectively), including prevalent alpha-L-fucosidase genes, which may be necessary for degrading complex sulfated polysaccharides such as fucoidan. Strain F21T encoded three putative glycosaminoglycan sulfotransferases and a putative sulfate glycosaminoglycan biosynthesis gene cluster. Based on phylogenetic and chemotaxonomic analyses, we propose the taxa Pontiella desulfatans F1T gen. nov., sp. nov. and Pontiella sulfatireligans F21T sp. nov. as representatives of the Pontiellaceae fam. nov. within the class Kiritimatiellae.