Microbial Community of a Sandy Beach Subterranean Estuary is Spatially Heterogeneous and Impacted by Winter Waves.

Subterranean estuaries (STEs) are critical ecosystems at the interface of meteoric groundwater and subsurface seawater that are threatened by sea level rise. To characterize the influence of tides and waves on the STE microbial community, we collected porewater samples from a high-energy beach STE at Stinson Beach, California, USA, over the two-week neap-spring tidal transition during both a wet and dry season. The microbial community, analyzed by 16S rRNA gene (V4) amplicon sequencing, clustered according to consistent physicochemical features found within STEs.

Benchmarking informatics approaches for virus discovery: caution is needed when combining identification methods.

Unlabelled: Understanding the ecological impacts of viruses on natural and engineered ecosystems relies on the accurate identification of viral sequences from community sequencing data. To maximize viral recovery from metagenomes, researchers frequently combine viral identification tools. However, the effectiveness of this strategy is unknown.

The virulence regulator VirB from Shigella flexneri uses a CTP-dependent switch mechanism to activate gene expression.

The transcriptional antisilencer VirB acts as a master regulator of virulence gene expression in the human pathogen Shigella flexneri. It binds DNA sequences (virS) upstream of VirB-dependent promoters and counteracts their silencing by the nucleoid-organizing protein H-NS. However, its precise mode of action remains unclear.

Pilotins are mobile T3SS components involved in assembly and substrate specificity of the bacterial type III secretion system.

In animal pathogens, assembly of the type III secretion system injectisome requires the presence of so-called pilotins, small lipoproteins that assist the formation of the secretin ring in the outer membrane. Using a combination of functional assays, interaction studies, proteomics, and live-cell microscopy, we determined the contribution of the pilotin to the assembly, function, and substrate selectivity of the T3SS and identified potential new downstream roles of pilotin proteins. In absence of its pilotin SctG, Yersinia enterocolitica forms few, largely polar injectisome sorting platforms and needles.

Cytosolic sorting platform complexes shuttle type III secretion system effectors to the injectisome in Yersinia enterocolitica.

Bacteria use type III secretion injectisomes to inject effector proteins into eukaryotic target cells. Recruitment of effectors to the machinery and the resulting export hierarchy involve the sorting platform. These conserved proteins form pod structures at the cytosolic interface of the injectisome but are also mobile in the cytosol.