A Widespread Bacterial Secretion System with Diverse Substrates

The microbial constituency of a host-associated microbiome emerges from a complex physical and chemical interplay of microbial colonization factors, host surface conditions, and host immunological responses. To fill unique niches within a host, bacteria encode surface and secreted proteins that enable interactions with and responses to the host and cooccurring microbes.

Soil causes gut microbiota to flourish and total serum IgE levels to decrease in mice

Background Traditional farm environments provide protection from allergic diseases. In this study, farm environmental factors were classified into three categories: environmental microbes, soil, and organic matter. To explore the impact of soil and environmental microorganisms on gut microbiota and immune function, mice were fed sterilized soil, soil microbes (in lieu of environmental microbes), or non-sterilized soil. Results Metagenomic sequencing results showed that the intake of sterile soil while inhaling a small amount of soil microbes in the air, increased gut microbial diversity and the abundance of type III secretion system (T3SS) genes and decreased total serum IgE levels induced by 2-4-dinitrofluorobenzene. The intake of soil microbes increased the abundance of genes involved in the metabolism of short-chain fatty acids and amino acid biosynthesis. By contrast, the intake of soil increased gut microbial diversity, the abundance of T3SS genes and related infectious elements, and genes associated with the metabolism of short-chain fatty acids and amino acid biosynthesis and decreased serum IgE levels. The immune function was positively and significantly correlated with the bacterial secretion system genes, especially with that of T3SS. Conclusions An important mechanism through which farm environments exert a protective effect against allergic diseases could be by serving as a “prebiotic” promoting the reproduction and growth of some intestinal microorganisms that harbor bacterial secretion system genes, especially those of T3SS, whose abundance was positively and significantly correlated with innate immune function of mice.

Soil causes gut microbiota to flourish and total serum IgE levels to decrease in mice

BackgroundTraditional farm environments provide protection from allergic diseases. In this study, farm environmental factors were classified into three categories: environmental microbes, soil, and organic matter. To explore the impact of soil and environmental microorganisms on gut microbiota and immune function, mice were fed sterilized soil, soil microbes (in lieu of environmental microbes), or non-sterilized soil.ResultsMetagenomic sequencing results showed that the intake of sterile soil while inhaling a small amount of soil microbes in the air, increased gut microbial diversity and the abundance of type III secretion system (T3SS) genes and decreased total serum IgE levels induced by 2-4-dinitrofluorobenzene. The intake of soil microbes increased the abundance of genes involved in the metabolism of short-chain fatty acids and amino acid biosynthesis. By contrast, the intake of soil increased gut microbial diversity, the abundance of T3SS genes and related infectious elements, and genes associated with the metabolism of short-chain fatty acids and amino acid biosynthesis and decreased serum IgE levels. The immune function was positively and significantly correlated with the bacterial secretion system genes, especially with that of T3SS.ConclusionsAn important mechanism through which farm environments exert a protective effect against allergic diseases could be by serving as a “prebiotic” promoting the reproduction and growth of some intestinal microorganisms that harbor bacterial secretion system genes, especially those of T3SS, whose abundance was positively and significantly correlated with innate immune function of mice.

Could the Next Antibiotic Emerge from Bacteria?

An intrinsic bacterial mechanism could play a fundamental role in the future of antibiotics. Using cryo-EM, the structural resolution of the effector protein complexed with its chaperone and other accessory proteins reveals the mechanism of action of type VI bacterial secretion system. The importance of the chaperone protein, used to prime the toxic effector protein, was previously identified. Future research efforts should encompass the immunity protein that may allow bacteria to evade the lethal effects of this mechanism.

SecA—a New Twist in the Tale

ABSTRACT A paper published in this issue of the Journal of Bacteriology (D. Huber, M. Jamshad, R. Hanmer, D. Schibich, K. Döring, I. Marcomini, G. Kramer, and B. Bukau, J Bacteriol 199:e0622-16, 2017, https://doi.org/10.1128/JB.00622-16 ) provides us with a timely reminder that all is not as clear as we had previously thought in the general bacterial secretion system. The paper describes a new mode of secretion through the Sec system—“uncoupled cotranslocation”—for the passage of proteins across the bacterial inner membrane and suggests that we might rethink the nature and mechanism of the targeting and transport steps toward protein export.