The expanding bacterial type IV secretion lexicon

Abstract

The bacterial type IV secretion systems (T4SSs) comprise a biologically diverse group of translocation systems functioning to deliver DNA or protein substrates from donor to target cells generally by a mechanism dependent on establishment of direct cell-to-cell contact. Members of one T4SS subfamily, the conjugation systems, mediate the widespread and rapid dissemination of antibiotic resistance and virulence traits among bacterial pathogens. Members of a second subfamily, the effector translocators, are used by often medically-important pathogens to deliver effector proteins to eukaryotic target cells during the course of infection. Here we summarize our current understanding of the structural and functional diversity of T4SSs and of the evolutionary processes shaping this diversity. We compare mechanistic and architectural features of T4SSs from Gram-negative and �positive species. Finally, we introduce the concept of the ‘minimized’ T4SSs; these are systems composed of a conserved set of 5–6 subunits that are distributed among many Gram-positive and some Gram-negative species.

A Review of Secretion Systems in Pathogenic and Non-Pathogenic Bacteria

“…The core components have been named as TssA-TssM. However, they have a lot of generic names that are widely used (e.g., Hcp and ClpV) 38,39 . In addition to the core Tss genes, gene clusters T6SS may also include other components that are fixed in most T6SSs, e.g., structural component Fha, proteins regulating PpkA and TagF pre-conversion and actuator of converting the dependent version to s54 VasH 40 .…”

“…These clusters may show system specific substrates and protective or regulatory proteins. Various genomicanalysesindicate that T6SSs are almost present in a quarter of the bacterial genomes of sequencing and have extended among proteobacteria (except epsilon proteobacteria) and at least one third of the bacteria have several T6SSs, and this amount is more than 6 times in Yersinia pestis, Burkholderiapseudomallei [37][38] .These analyses show that T6SSs can be classified to 4 families or phylogenetic groups A, B, C, D 1,6 that are corresponding to the I, II,V,IV 37 , although, a complete structure is not provided for T6SS subcompound like available structures for T3SS and T4SS 38 . It has recently been reported that the antibacterial T6SSs have been invented and effectively used to fight bacterial cells 38,39 .…”

“…It has been proved that T6SSs are necessary in virulence and/or normal reactions with eukaryotic cells in different bacteria especially pathogen bacteria [37][38] . Different bacteria are included a wide variety of species from plant pathogens (such as Pectobacterium atrosepticum) to animal pathogens (such as E. tarda and Salmonella Gallinarum) and even wellrecognized and important human pathogens (such as V. cholerae, Burkholderiasp and P. aeruginosa).…”

“…And although nothing secreted from this T6SS is still determined but it shows molecular results of T6SS activity in eukaryotic cell. Burkholderia cenocepacia survives inside the host cell macrophages within the vacuoles bondable to the membrane (B. cenocepacia-containing vacuole, BcCV) [38][39][40][41][42][43][44] .…”

Scientific Opinion on the evaluation of molecular typing methods for major food‐borne microbiological hazards and their use for attribution modelling, outbreak investigation and scanning surveillance: Part 1 (evaluation of methods and applications)

“…Salmonella bacteriophages are often involved and mediate horizontal transfer of virulence genes among Salmonella strains by transduction and lysogenic conversion (Rabsch et al, 2002b). Integrons, genomic islands and plasmids (which may carry integrons with them) may be involved in transfer of bacterial secretion systems, virulence and antimicrobial resistance genes (Guerra et al, 2001;Dobrindt et al, 2004;Randall et al, 2004;Sandvang et al, 2006, Bhatty et al, 2013) from other organisms to Salmonella, and vice versa (Siebor and Neuwirth, 2013). …”