Interspecies interactions shape microbial communities; this is central for microbial ecology. Cellulophaga lytica PlyA2 is a marine flavobacterium, which glides over surfaces and forms ordered, structurally coloured colonies, which display angle-dependent reflection of light. Pseudosulfitobacter pseudonitzschiae SW is an apparently nonmotile, nonstructurally coloured marine bacterium. Here, we aim to understand the interaction of both strains at cellular, genomic, optical, and proteomic levels. Cocultivation on agar showed that P. pseudonitzschiae uses gliding C. lytica to spread by microbial hitchhiking in which Pseudosulfitobacter appears to "surf"on basal layers of motile Cellulophaga. This dispersal mechanism was found to be often beneficial for P. pseudonitzschiae, which could maximally expand its population up to 350-fold relative to monoculture. Coculture was often of limited benefit for C. lytica, only in extended cultivation on rich medium was the presence of P. pseudonitzschiae detrimental to its viability. The proteome of P. pseudonitzschiae was strongly impacted by the association with C. lytica. Quorum-sensing signalling, potential exchange of amino acids, vitamins, and other metabolites are likely mediating this hitchhiking interaction. In contrast, C. lytica made minimal adjustments to its proteome composition in coculture. Supported by optical analysis, P. pseudonitzschiae patterned C. lytica by changing how groups of the latter organised to reflect light. Our results underscore the unusual, dynamic interplay between two bacterial species and provide insights on the mechanisms underlying this relationship.

Background and Aim: Over the past years, the gut microbiota and its correlation to health and disease has been studied extensively. In terms of beneficial microbes, an increased interest in Akkermansia muciniphila (A. muciniphila) has been observed since its discovery. Direct evidence for the role of A. muciniphila in host health has been provided in both mice and human studies. However, for human interventions with A. muciniphila cells, industrial-scale fermentations are needed, and hence, the used cultivation media should be free of animal-derived components, food-grade, non-allergenic and allow for efficient growth to high densities to provide cost-effective production platforms. In this study, we assessed the growth and performance of A. muciniphila in batch bioreactors using newly developed plant-based media. Methods: The bioreactors were supplemented with varying carbon sources, including different ratios of N-acetylglucosamine (GlcNAc) and glucose. We monitored the growth of A. muciniphila in the plant-based medium using optical density (OD600) measurements and microscopy. In addition, we used a combination of biochemical analysis as well as transcriptional and proteomics analysis to gain detailed insight into the physiology. Results: Comparisons between growth on these media and that on mucin revealed differences at both transcriptome and proteome levels, including differences in the expression of glycosyltransferases, signaling proteins, and stress response. Furthermore, elongated cells and higher OD600 values were observed using the plant-based media as compared to cultivation media containing mucin. Conclusion: These differences do not hamper growth, and therefore, our data suggest that the food-grade medium composition described here could be used to produce A. muciniphila with high yields for therapeutic purposes.

Methanol is generally metabolized through a pathway initiated by a cobalamine-containing methanol methyltransferase by anaerobic methylotrophs (such as methanogens and acetogens), or through oxidation to formaldehyde using a methanol dehydrogenase by aerobes. Methanol is an important substrate in deep-subsurface environments, where thermophilic sulfate-reducing bacteria of the genus Desulfotomaculum have key roles. Here, we study the methanol metabolism of Desulfotomaculum kuznetsovii strain 17^T, isolated from a 3000-m deep geothermal water reservoir. We use proteomics to analyze cells grown with methanol and sulfate in the presence and absence of cobalt and vitamin B12. The results indicate the presence of two methanol-degrading pathways in D. kuznetsovii, a cobalt-dependent methanol methyltransferase and a cobalt-independent methanol dehydrogenase, which is further confirmed by stable isotope fractionation. This is the first report of a microorganism utilizing two distinct methanol conversion pathways. We hypothesize that this gives D. kuznetsovii a competitive advantage in its natural environment.