Secretory and circulating bacterial small RNAs: a mini-review of the literature

Abstract

Background: Over the past decade, small non-coding RNAs (sRNAs) have been characterized as important posttranscriptional regulators in bacteria and other microorganisms. Secretable sRNAs from both pathogenic and nonpathogenic bacteria have been identified, revealing novel insight into interspecies communications. Recent advances in the understanding of the secretory sRNAs, including extracellular vesicle-transported sRNAs and circulating sRNAs, have raised great interest. Methods: We performed a literature search of the database PubMed, surveying the present stage of knowledge in the field of secretory and circulating bacterial sRNAs. Conclusion: Extracellular bacterial sRNAs play an active role in host-microbe interactions. The findings concerning the secretory and circulating bacterial sRNAs may kindle an eager interest in biomarker discovery for infectious bacterial diseases.

Small RNAs in the Antarctic bacterium Pseudomonas extremaustralis responsive to oxygen availability and oxidative stress

“…The size distribution of these sRNAs ranged between 60 and 400 nucleotides, with most of them presenting a length of 60–200 nucleotides (Supporting information Fig. S1A), similar to those observed in other bacterial species (Wang and Fu, 2019). sRNA sequences were analysed using the RNAcentral Database (https://rnacentral.org), which allowed the identification of non‐coding RNAs previously described in bacteria and their classification according to the biological processes in which they are involved.…”

Potential Mechanisms Linking Food-Derived MicroRNAs, Gut Microbiota and Intestinal Barrier Functions in the Context of Nutrition and Human Health

“…Extracellular vesicles of bacterial origin are not only involved in bacteria-bacteria communication, but also in bacteria-host cell communication, being able to elicit phenotypic changes in host cells altering their function with both detrimental and beneficial actions (107)(108)(109). Characterization studies of their cargo showed that they can contain several types of molecules, including structural and soluble proteins such as enzymes, secondary metabolites, virulence factors, glycolipids, lipopolysaccharides, bacterial antigens and a wide range of nucleic acids, including DNA and microRNA-like molecules, which have been extensively summarized in other reviews (110)(111)(112). Remarkably, gut microbiota can release extracellular vesicles that can influence host physiology, playing part in processes such as digestion (by carrying digestive enzymes), intestinal permeability regulation, metabolism or gut immunity (113)(114)(115).…”

Extracellular Vesicles and Host–Pathogen Interactions: A Review of Inter-Kingdom Signaling by Small Noncoding RNA

“…OMVs and BEVs mediate the inter-kingdom transfer of sRNA and tRNA fragments between bacteria and mammalian cells without requiring direct contact [ 4 , 30 , 31 , 32 , 41 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. For example, Pseudomonas aeruginosa , residing in the mucus layer overlying lung epithelial cells, secretes OMVs that diffuse through the mucus, fuse with lipid rafts in the apical membrane of airway epithelial cells and deliver a 23 nt tRNA fragment (sRNA-52320) into host cells.…”

“…In this review, the terms EVs, OMVs and BEVs will be used to describe EVs secreted by non-microbial cells, Gram-negative bacteria, and Gram-positive bacteria, respectively. Many recent studies have shown that OMVs and BEVs secreted by bacteria deliver sRNA and tRNA fragments (~18 to 50 nucleotides (nt) long) to mammalian (human) cells and, although many details are lacking, it has been suggested that the sRNA and tRNA fragments regulate target cell gene expression by sequestering regulatory proteins and/or by base pairing with target mRNAs [ 4 , 18 , 22 , 30 , 31 , 32 , 41 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. sRNAs are heterogeneous in size (~20 to 500 nt) and regulate gene expression by base-pairing with the translation initiation region or coding sequence of target mRNAs or by acting as sRNA sponges, which are produced by transgenes and have complementary binding sites to specific miRNAs [ 13 ].…”