Global distribution and diversity of marine euendolithic cyanobacteria

Differences in Microbial Community Structure Determine the Functional Specialization of Gut Segments of Ligia exotica

Ligia feed on seashore algae and remove organic debris from the coastal zone, thereby playing an important role in the intertidal ecosystem. Nevertheless, the specific roles of distinct gut segments in the gut transit remain unclear. We collected and identified Ligia exotica specimens in the coast of Aoshanwei, Qingdao, Shandong Province, and analyzed their foreguts and hindguts for 16S rRNA, metagenomics, metabolomics, and proteomics. The concentrations of common metabolites, NO3--N and NH4+-N, and the contents of C and N were measured. The gut transit decreased the abundances of the dominant phyla Cyanobacteria but increased Proteobacteria, Firmicutes, and Actinobacteria, and Planctomycetes and Bacteroidetes remained relatively constant. The foregut gut microbiota is involved in the carbohydrates and amino acids metabolism, as well as the decomposition of polysaccharides. The hindgut gut microbiota performs a variety of functions, including carbohydrate and amino acid metabolism, fermentation, cell motility, intracellular transport, secretion, and vesicular translocation, and the decomposition of polysaccharides, disaccharides, and oligosaccharides. The results of omics analyses and molecular experiments demonstrated that the metabolic processes involving amino acids and carbohydrates are more active in the foregut, whereas the fermentation, absorption, and assimilation processes are more active in the hindgut. Taken together, the differences in microbial community structure determine the functional specialization of different gut segments, i.e., the foregut appears to be the primary site for digesting food, while the hindgut further processes and absorbs nutrients and then excretes them.

Searching for microbial contribution to micritization of shallow marine sediments

Micritization is an early diagenetic process that gradually alters primary carbonate sediment grains through cycles of dissolution and reprecipitation of microcrystalline calcite (micrite). Typically observed in modern shallow marine environments, micritic textures have been recognized as a vital component of storage and flow in hydrocarbon reservoirs, attracting scientific and economic interests. Due to their endolithic activity and the ability to promote nucleation and reprecipitation of carbonate crystals, microorganisms have progressively been shown to be key players in micritization, placing this process at the boundary between the geological and biological realms. However, published research is mainly based on geological and geochemical perspectives, overlooking the biological and ecological complexity of microbial communities of micritized sediments. In this paper, we summarize the state-of-the-art and research gaps in micritization from a microbial ecology perspective. Since a growing body of literature successfully applies in vitro and in situ 'fishing' strategies to unveil elusive microorganisms and expand our knowledge of microbial diversity, we encourage their application to the study of micritization. By employing these strategies in micritization research, we advocate promoting an interdisciplinary approach/perspective to identify and understand the overlooked/neglected microbial players and key pathways governing this phenomenon and their ecology/dynamics, reshaping our comprehension of this process.