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Helicobacter
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Gram-negative and gram-positive bacteria possess types I–V secretion systems. Among them, the type IV secretion system is used to deliver DNA, protein, or other macromolecules to target bacterial or eukaryotic cells. This apparatus resembles that of Agrobacterium tumefaciens, consisting of 12 proteins including virB1–11 and virD4.111 In H. pylori, there are three types of type IV secretion systems, ComB, Cag, and Tfs3, in which Cag determines the bacterial virulence.112
Brucella
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Smooth Brucella that enter via lipid rafts quickly traffic through the early endosomal compartment and depart the phagosome to form the modified phagosome (termed brucellosome) by acquiring components of endoplasmic reticulum in a manner similar to autophagosome biogenesis. Brucella initially localize within acidified phagosomes40 where they are exposed to free oxygen radicals generated by the respiratory burst. Brucella require acidification of the phagosomal compartment to a pH < 4.5 before they display wild-type intracellular replication. The requirement for low pH is transient and only extends through the initial stages of intracellular infection. Localization in an acidified environment induces expression of the VirB operon (virB 1–10), which controls expression of genes associated with a type IV secretion system. The VirB operon interacts with the endoplasmic reticulum to neutralize the pH of the phagosome.41Brucella-induced modifications of the phagosome leads to inhibition of phagosome maturation and prevention of fusion with lysosomes. The brucellosome environment provides Brucella with conditions of nutrient depletion and limited oxygen availability. It should be noted that under in vitro conditions, up to 90% of virulent Brucella, and 99% of nonvirulent Brucella, may be killed following intracellular entry.42
Rickettsia spp.
Published in Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward, Case Studies in Infectious Disease, 2010
Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward
The Rickettsia are small bacteria (0.3 ¥ 0.1 μm) that are obligate intracellular pathogens. They have a typical tri-laminar gram-negative cell wall structure and chemistry, although they stain poorly with the Gram stain. Morphologically the cell wall of Orientia (previously included as a Rickettsia sp.) has a different cell wall structure with a prominent outer layer compared with the Rickettsia spp., which have a prominent inner layer. The Rickettsia spp. have a small genome size of about 1.3 Mbp, which is the result of gene decay. To date, three rickettsial genomes have been sequenced: R. prowazekii, R. typhi, and R. conori. Twenty-three genes are common to R. prowazekii and R. typhi, 15 are common to R. prowazekii and R. conori, 24 are found only in R. typhi, and 775 are common to all three species. Since their cytosolic habitat is rich in nutrients, amino acids, and nucleotides, they lack enzymes for sugar and amino acid metabolism, and for lipid and nucleotide synthesis. Their genome therefore codes for several transport proteins, which enable them to utilize host cell products including ATP, although they may also synthesize ATP. They possess a type IV secretion system.
Tracing the origins of extracellular DNA in bacterial biofilms: story of death and predation to community benefit
Published in Biofouling, 2021
Davide Campoccia, Lucio Montanaro, Carla Renata Arciola
In Neisseria gonorrhoeae, secretion of chromosomal DNA has been found to be associated to a type IV secretion system (TFSS) implicated in bacterial transformation. Salgado-Pabón et al. (2010) observed that, within the cell population, gonococcal variants that produce type IV pili release larger quantities of DNA than non-piliated variants. Piliated strains would produce the largest quantity of DNA secretion in late log-phase growth and DNA release would not occur through autolysis. Moreover, secreted DNA would be in the form of single-strand DNA protected at the 5′ end from 5′–3′ exonuclease digestion (Salgado-Pabón et al. 2007). Secretion would occur between the 2-h and 2.5-h time points and precede the onset of the stationary/death phase during which bacteria would switch to cell lytic processes.
The role of gastric microbiota in gastric cancer
Published in Gut Microbes, 2020
Oliver A. Stewart, Fen Wu, Yu Chen
One study demonstrated decreased abundance of Sphingobium yanoikuyae in patients with gastric cancer compared to patients with superficial gastritis.25 This species is capable of degrading aromatic hydrocarbons, which are a group of molecules that has potential carcinogenic effects.25 This study was the first study to suggest a negative association between Sphingobium yanoikuvae and gastric cancer. Park et al.’s 2019 study found an increased level of abundance of Rhiozobiales in patients with intestinal metaplasia compared to patients with chronic superficial gastritis.26 In addition, they found an increased abundance of genes encoding type IV secretion system (T4SS) proteins in the metagenome of patients with intestinal metaplasia. T4SS is one type of secretion system used by microorganisms to transport macromolecules across the cell envelope.35 Many pathogenic bacteria use the T4SS in order to transfer proteins known as virulence factors that confer a bacterium with its pathogenicity.36 T4SS proteins consist of a smaller subset of proteins that allow injection of H. pylori’s proposed main virulence factor, CagA, from the bacterial cytoplasm to the cytoplasm of gastric epithelial cells.37 Although the researchers did not find direct evidence of horizontal genetic transfer between Rhizobiales and H. pylori, they hypothesized that it is possible that T4SS genetic transfer occurs between H. pylori and members of the microbiota, thus contributing to H. pylori’s carcinogenicity.
Hypervirulence and carbapenem resistance: two distinct evolutionary directions that led high-risk Klebsiella pneumoniae clones to epidemic success
Published in Expert Review of Molecular Diagnostics, 2019
Yi-Chyi Lai, Min-Chi Lu, Po-Ren Hsueh
The number of mobile elements, including prophages and insertion sequences identified in the genomes of CG258, is significantly higher than those found in the hypervirulent CG23 strains [39]. The presence of ICEKp258.1 and ICEKp258.2 may help foreign DNA acquisition in CG258 strains. The type IV secretion system carried by ICEKp258.1 may have a role in accelerating the horizontal transfer of mobile genetic elements. Genomic analyses by independent groups have concluded that ST258 is a hybrid clone derived from an ST11 ancestor, containing 80% of ST11-like and 20% of ST442-like genes. The global success of ST258 may be attributed to the inheritance of ICEKp258.2, which is exclusively present in the ST258 lineage [111]. The determinants on ICEKp258.2 form two gene clusters. The first cluster codes for a type IV pilus that assists ST258 strains by increasing the uptake of plasmids and bacterial adherence to surfaces. The second cluster encodes a type III restriction-modification system that determines host specificity for plasmid compatibilities and plays a role in the restriction of the types of plasmids acquired by the ST258 strains. Further, ICEKp258.2 contributes to the divergence of the ST258 and ST11 strains. The ST258 strains predominantly harbor blaKPC-bearing plasmids [109], whereas ST11 strains acquire a broader range of plasmids carrying various carbapenemases (KPC, OXA-48, NDM, and VIM) [112,113].