Protein Interactome Analysis of the Type IX Secretion System Identifies PorW as the Missing Link between the PorK/N Ring Complex and the Sov Translocon

The T9SS is a newly identified protein secretion system of the Fibrobacteres - Chlorobi - Bacteroidetes superphylum used by pathogens associated with diseases of humans, fish, and poultry for the secretion and cell surface attachment of virulence factors. The T9SS comprises three known modules: (i) the trans-envelope core module comprising the PorL/M motor and the PorK/N ring, (ii) the outer membrane Sov translocon, and (iii) the cell surface attachment complex.

In Silico analysis of PE_PGRS20 (Rv1068c) protein in Mycobacterium tuberculosis H37Rv

The genetic makeup of Mycobacterium tuberculosis reveals the presence of an unknown repeat sequence of PE_PGRS family proteins that are responsible for antigenic variations and many unknown functions that includes necrosis of macrophage and apoptosis. The structure and function of these glycine-rich proteins can be predictable by homology modeling, the Ab-initio method, or by using different tools of bioinformatics. In this study, we selected, PE_PGRS20 (Rv1068c) an unknown PE_PGRS protein. We suggest that the PE_PGRS20 gene is linked with the others genes of the espACD operon which are the virulence factors in the M. tuberculosis H37Rv strain. The genes associated with this protein secretion system can perform the synthesis of a special type of fatty acid known as phthioceroldimycocerates (PDIM).Docking with different anti TB drugs shows binding with PE_PGRS20 protein which suggests that the target protein may involve in the drug resistance.

The Type VII Secretion System of Staphylococcus

The type VII protein secretion system (T7SS) of Staphylococcus aureus is encoded at the ess locus. T7 substrate recognition and protein transport are mediated by EssC, a membrane-bound multidomain ATPase. Four EssC sequence variants have been identified across S. aureus strains, each accompanied by a specific suite of substrate proteins. The ess genes are upregulated during persistent infection, and the secretion system contributes to virulence in disease models. It also plays a key role in intraspecies competition, secreting nuclease and membrane-depolarizing toxins that inhibit the growth of strains lacking neutralizing immunity proteins. A genomic survey indicates that the T7SS is widely conserved across staphylococci and is encoded in clusters that contain diverse arrays of toxin and immunity genes. The presence of genomic islands encoding multiple immunity proteins in species such as Staphylococcus warneri that lack the T7SS points to a major role for the secretion system in bacterial antagonism. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Identification and architecture of a putative secretion tube across mycobacterial outer envelope

Tuberculosis-causing mycobacteria have thick cell-wall and capsule layers that are formed from complex structures. Protein secretion across these barriers depends on a specialized protein secretion system, but none has been reported. We show that Mycobacterium tuberculosis Rv3705c and its homologous MSMEG_6251 in Mycobacterium smegmatis are tube-forming proteins in the mycobacterial envelope (TiME). Crystallographic and cryo-EM structures of these two proteins show that both proteins form rotationally symmetric rings. Two layers of TiME rings pack together in a tail-to-tail manner into a ring-shaped complex, which, in turn, stacks together to form tubes. M. smegmatis TiME was detected mainly in the cell wall and capsule. Knocking out the TiME gene markedly decreased the amount of secreted protein in the M. smegmatis culture medium, and expression of this gene in knocked-out strain partially restored the level of secreted protein. Our structure and functional data thus suggest that TiME forms a protein transport tube across the mycobacterial outer envelope.

Engineered Type Six Secretion Systems Deliver Active Exogenous Effectors and Cre Recombinase

Delivery of protein-based drugs, antigens, and gene-editing agents has broad applications. The type VI protein secretion system (T6SS) can target both bacteria and eukaryotic cells and deliver proteins of diverse size and function.

The type VI secretion system of Xanthomonas phaseoli pv. manihotis is involved in virulence and in vitro motility

Background The type VI protein secretion system (T6SS) is important in diverse cellular processes in Gram-negative bacteria, including interactions with other bacteria and with eukaryotic hosts. In this study we analyze the evolution of the T6SS in the genus Xanthomonas and evaluate its importance of the T6SS for virulence and in vitro motility in Xanthomonas phaseoli pv. manihotis (Xpm), the causal agent of bacterial blight in cassava (Manihot esculenta). We delineate the organization of the T6SS gene clusters in Xanthomonas and then characterize proteins of this secretion system in Xpm strain CIO151. Results We describe the presence of three different clusters in the genus Xanthomonas that vary in their organization and degree of synteny between species. Using a gene knockout strategy, we also found that vgrG and hcp are required for maximal aggressiveness of Xpm on cassava plants while clpV is important for both motility and maximal aggressiveness. Conclusion We characterized the T6SS in 15 different strains in Xanthomonas and our phylogenetic analyses suggest that the T6SS might have been acquired by a very ancient event of horizontal gene transfer and maintained through evolution, hinting at their importance for the adaptation of Xanthomonas to their hosts. Finally, we demonstrated that the T6SS of Xpm is functional, and significantly contributes to virulence and motility. This is the first experimental study that demonstrates the role of the T6SS in the Xpm-cassava interaction and the T6SS organization in the genus Xanthomonas.

Twin-arginine translocation (Tat) mutants in Salmonella enterica serovar Typhimurium have increased susceptibility to cell wall targeting antibiotics

ABSTRACT The twin-arginine translocation (Tat) system is a protein secretion system that is conserved in bacteria, archaea and plants. In Gram-negative bacteria, it is required for the export of folded proteins from the cytoplasm to the periplasm. There are 30 experimentally verified Tat substrates in Salmonella, including hydrogenase subunits, enzymes required for anaerobic respiration and enzymes involved in peptidoglycan remodeling during cell division. Multiple studies have demonstrated the susceptibility of tat mutants to antimicrobial compounds such as SDS and bile; however, in this work, we use growth curves and viable plate counts to demonstrate that cell wall targeting antibiotics (penicillins, carbapenems, cephalosporins and fosfomycin) have increased killing against a Δtat strain. Further, we demonstrate that this increased killing is primarily due to defects in translocation of critical Tat substrates: MepK, AmiA, AmiC and SufI. Finally, we show that a ΔhyaAB ΔhybABC ΔhydBC strain has an altered ΔΨ that impacts proper secretion of critical Tat substrates in aerobic growth conditions.

The Type VI Secretion System of Xanthomonas phaseoli pv. manihotis is involved in virulence and in vitro motility

Background: The type VI protein secretion system (T6SS) is important in diverse cellular processes in Gram-negative bacteria, including interactions with other bacteria and with eukaryotic hosts. In this study we analyze the evolution of the T6SS in the genus Xanthomonas and evaluate its importance of the T6SS for virulence and in vitro motility in Xanthomonas phaseoli pv. manihotis (Xpm), the causal agent of bacterial blight in cassava (Manihot esculenta). We delineate the organization of the T6SS gene clusters in Xanthomonas and then characterize proteins of this secretion system in Xpm strain CIO151. Results: We describe the presence of three different clusters in the genus Xanthomonas that vary in their organization and degree of synteny between species. Using a gene knockout strategy, we also found that vgrG and hcp are required for maximal aggressiveness of Xpm on cassava plants while clpV is important for both motility and maximal aggressiveness. Conclusion: We characterized the T6SS in 15 different strains in Xanthomonas and our phylogenetic analyses suggest that the T6SS might have been acquired by a very ancient event of horizontal gene transfer and maintained through evolution, hinting at their importance for the adaptation of Xanthomonas to their hosts. Finally, we demonstrated that the T6SS of Xpm is functional, and significantly contributes to virulence and motility. This is the first experimental study that demonstrates the role of the T6SS in the Xpm-cassava interaction and the T6SS organization in the genus Xanthomonas.

The Type VI Secretion System of Xanthomonas phaseoli pv. manihotis is involved in virulence and in vitro motility

Background: The type VI protein secretion system (T6SS) is important in diverse cellular processes in Gram-negative bacteria, including interactions with other bacteria and with eukaryotic hosts. In this study we analyze the evolution of the T6SS in the genus Xanthomonas and evaluate its importance of the T6SS for virulence and in vitro motility in Xanthomonas phaseoli pv. manihotis (Xpm), the causal agent of bacterial blight in cassava (Manihot esculenta). We delineate the organization of the T6SS gene clusters in Xanthomonas and then characterize proteins of this secretion system in Xpm strain CIO151. Results: We describe the presence of three different clusters in the genus Xanthomonas that vary in their organization and degree of synteny between species. Using a gene knockout mutagenesis, we also found that vgrG and hcp are required for maximal aggressiveness of Xpm on cassava plants while clpV is important for both motility and maximal aggressiveness. Conclusion: We characterized the T6SS in 15 different strains in Xanthomonas and our phylogenetic analyses suggest that the T6SS might have been acquired by a very ancient event of horizontal gene transfer and maintained through evolution, hinting at their importance for the adaptation of Xanthomonas to their hosts. Finally, we demonstrated that the T6SS of Xpm is functional, and significantly contributes to virulence and motility. This is the first experimental study that demonstrates the role of the T6SS in the Xpm-cassava interaction and the T6SS organization in the genus Xanthomonas.

Antieukaryotic Type Six Secretion System Virulence Factors of Bacteria

The type 6 protein secretion system (T6SS) is prevalently utilized by Gram-negative bacteria to compete for resources and space. Upon activation, toxic effectors from this secretion system are translocated into the competitor prokaryote or eukaryote in a contact-dependent manner. While much has been reported on T6SS-mediated prokaryotic competition, very little is understood about the mechanisms of bacterial interactions with eukaryotic hosts. Likewise, many virulent T6SS effectors are known to be antibacterial. In recent years, however, evidence has emerged on numerous T6SS effectors that interact with related immunity proteins in a range of eukaryotic hosts. Insights into how this effector-immunity pairing alters the physiological responses of the recipient organism might provide opportunities relating to the T6SS agricultural and biotherapeutic applications. We, therefore, summarize the impacts of the T6SS effectors with a special focus on bacterial interactions with animals, plants, and fungi. We further briefly discuss pipelines that are currently used to characterize antieukaryotic T6SS effectors.