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 E39T, was isolated from the rumen epithelium of Korean cattle. The cells were non-motile and had a coccus morphology. Growth of strain E39T 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 E39T contained C16:0, C18:0, C18:1 ω9c, iso-C15:0, and anteiso-C15:0 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 E39T was most closely related to Alloprevotella rava 81/4-12T with an 87.3% 16S rRNA gene sequence similarity. On the basis of phenotypic, chemotaxonomic, and molecular properties, strain E39T 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 E39T 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.

Refuting the ideas advocated by Yuly et al. (PNAS, Sep. 2020): ‘Universal free energy landscapes’ and ‘deterministic electron-relay circuitry’ are unsustainable within membrane-embedded cytochrome b protein complexes involved in bioenergetic routines

This communication discusses the interactions/outcomes of isoprenoid quinones/quinols (Q/QH2) and membrane-bound cytochromes involved in bioenergetic routines. Particularly, we use qualitative and quantitative arguments to counter the idea that highly deterministic electron relays are triggered within Complex III of mitochondria, resulting from the donation of two electrons by QH2 (Yuly et al., PNAS, 2020). In this regard, we propose that murburn concept explains the role(s) of membrane-embedded Q/QH2 in vital metabolic processes such as mitochondrial oxidative phosphorylation (OxPhos) and chloroplastid/cyanobacterial photophosphorylations (PhotoPhos), without invoking highly fastidious universal free energy landscapes or deterministic electron circuitry.

Nesterenkonia muleiensis sp. nov., a novel actinobacterium isolated from sap of Populus euphratica

A novel, Gram-stain-positive, aerobic, non-endospore-forming, non-motile and rod-shaped bacterium designated RB2T was isolated from sap of Populus euphratica collected in Mulei county, Xinjiang province, PR China. RB2T was able to grow at 10–45 °C (optimum 35 °C), pH 6.0–12.0 (optimum 8.0) and with 0–12 % (w/v) NaCl (optimum 1 %). The genomic DNA G+C content was 63.5 % (from the genome sequence). The results of the chemotaxonomic analysis indicated that the predominant isoprenoid quinones were MK-8 and MK-9. The major fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. The major polar lipids of RB2T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two glycolipids. The peptidoglycan type of RB2T was A4α, l-Lys–Gly–l-Glu. The results of the phylogenetic analysis, along with the phenotypic and chemotaxonomic characteristics, indicate that strain RB2T represents a novel species of the genus Nesterenkonia , for which the name Nesterenkonia muleiensis sp. nov. is proposed. The type strain is RB2T (=MCCC 1K03528T=KCTC 49017T).

Phragmitibacter flavus gen. nov., sp. nov. a new member of the family Verrucomicrobiaceae

The Gram-stain-negative, aerobic, non-motile, oxidase- and catalase-positive, rod-shaped yellow-coloured bacterial strain MG-N-17T was isolated from a water sample of Lake Fertő/Neusiedler See (Hungary). Results of phylogenetic analysis based on the 16S rRNA gene sequence revealed that the strain forms a distinct linage within the family Verrucomicrobiaceae of the phylum Verrucomicrobia , and its closest relatives are Verrucomicrobium spinosum DSM 4136T (94.38 %) and Roseimicrobium gellanilyticum DC2a-G7T (91.55 %). The novel bacterial strain prefers a weak alkaline environment and grows optimally between 22–28 °C in the absence of NaCl. The major isoprenoid quinones are MK-10, MK-11, MK-12 and MK-9. The major cellular fatty acids are anteiso-C15 : 0, C16 : 0, C16 : 1ω5c and iso-C14 : 0. The polar lipid profile contains phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids and four unidentified glycolipids. The assembled draft genome of strain MG-N-17T had 44 contigs with an N50 value 348255 nt, 56.5× genome coverage, total length of 5 910 933 bp and G+C content of 56.9 mol%. Strain MG-N-17T (=DSM 106674T=NCAIM B.02643T) is proposed as the type strain of a new genus and species in the family Verrucomicrobiaceae , for which the name Phragmitibacter flavus gen. nov., sp. nov. is proposed.

Engineering isoprenoid quinone production in yeast

Isoprenoid quinones are bioactive molecules that include an isoprenoid chain and a quinone head. They are traditionally found to be involved in primary metabolism, where they act as electron transporters, but specialized isoprenoid quinones are also produced by all domains of life. Here, we report the engineering of a baker's yeast strain, Saccharomyces cerevisiae EPYFA3, for the production of isoprenoid quinones. Our yeast strain was developed through overexpression of the shikimate pathway in a well-established recipient strain (S. cerevisiae EPY300) where the mevalonate pathway is overexpressed. As a proof of concept, our new host strain was used to overproduce the endogenous isoprenoid quinone coenzyme Q6, resulting in a final four-fold production increase. EPYFA3 represents a valuable platform for the heterologous production of high value isoprenoid quinones. EPYFA3 will also facilitate the elucidation of isoprenoid quinone biosynthetic pathways.

Unusual features of the c-ring of F1FO ATP synthases

Membrane integral ATP synthases produce adenosine triphosphate, the universal “energy currency” of most organisms. However, important details of proton driven energy conversion are still unknown. We present the first high-resolution structure (2.3 Å) of the in meso crystallized c-ring of 14 subunits from spinach chloroplasts. The structure reveals molecular mechanisms of intersubunit contacts in the c14-ring, and it shows additional electron densities inside the c-ring which form circles parallel to the membrane plane. Similar densities were found in all known high-resolution structures of c-rings of F1FO ATP synthases from archaea and bacteria to eukaryotes. The densities might originate from isoprenoid quinones (such as coenzyme Q in mitochondria and plastoquinone in chloroplasts) that is consistent with differential UV-Vis spectroscopy of the c-ring samples, unusually large distance between polar/apolar interfaces inside the c-ring and universality among different species. Although additional experiments are required to verify this hypothesis, coenzyme Q and its analogues known as electron carriers of bioenergetic chains may be universal cofactors of ATP synthases, stabilizing c-ring and prevent ion leakage through it.

Isoprenoid Quinones Resolve the Stratification of Redox Processes in a Biogeochemical Continuum from the Photic Zone to Deep Anoxic Sediments of the Black Sea

ABSTRACTThe stratified water column of the Black Sea serves as a model ecosystem for studying the interactions of microorganisms with major biogeochemical cycles. Here, we provide detailed analysis of isoprenoid quinones to study microbial redox processes in the ocean. In a continuum from the photic zone through the chemocline into deep anoxic sediments of the southern Black Sea, diagnostic quinones and inorganic geochemical parameters indicate niche segregation between redox processes and corresponding shifts in microbial community composition. Quinones specific for oxygenic photosynthesis and aerobic respiration dominate oxic waters, while quinones associated with thaumarchaeal ammonia oxidation and bacterial methanotrophy, respectively, dominate a narrow interval in suboxic waters. Quinone distributions indicate highest metabolic diversity within the anoxic zone, with anoxygenic photosynthesis being a major process in its photic layer. In the dark anoxic layer, quinone profiles indicate the occurrence of bacterial sulfur and nitrogen cycling, archaeal methanogenesis, and archaeal methanotrophy. Multiple novel ubiquinone isomers, possibly originating from unidentified intra-aerobic anaerobes, occur in this zone. The respiration modes found in the anoxic zone continue into shallow subsurface sediments, but quinone abundances rapidly decrease within the upper 50 cm below the sea floor, reflecting the transition to lower energy availability. In the deep subseafloor sediments, quinone distributions and geochemical profiles indicate archaeal methanogenesis/methanotrophy and potentially bacterial fermentative metabolisms. We observed that sedimentary quinone distributions track lithology, which supports prior hypotheses that deep biosphere community composition and metabolisms are determined by environmental conditions during sediment deposition.IMPORTANCEMicroorganisms play crucial roles in global biogeochemical cycles, yet we have only a fragmentary understanding of the diversity of microorganisms and their metabolisms, as the majority remains uncultured. Thus, culture-independent approaches are critical for determining microbial diversity and active metabolic processes. In order to resolve the stratification of microbial communities in the Black Sea, we comprehensively analyzed redox process-specific isoprenoid quinone biomarkers in a unique continuous record from the photic zone through the chemocline into anoxic subsurface sediments. We describe an unprecedented quinone diversity that allowed us to detect distinct biogeochemical processes, including oxygenic photosynthesis, archaeal ammonia oxidation, aerobic methanotrophy, and anoxygenic photosynthesis in defined geochemical zones.