Pseudomonas aeruginosa: An Understanding of Resistance Issues
Robert C. Owens, Lautenbach Ebbing in Antimicrobial Resistance, 2007
The pathogenesis of P. aeruginosa may be divided into three stages: (i) bacterial attachment and colonization, (ii) local invasion and dissemination, and (iii) systemic disease; although disease progression can stop at any stage. The organism is well endowed with diverse virulence factors that promote colonization and/or infection. For example, pili or fimbriae (which are specialized attachment organelles) and mucoid exopolysaccharide allow for adherence of P. aeruginosa to epithelial cells (1,7). In addition, exoenzyme S, which is displayed on the bacterial cell surface, appears also to mediate bacterial attachment to respiratory epithelium (8). In combination with an array of others, these secreted virulence factors and endotoxins collectively contribute to the Pseudomonas’ pathogenic versatility (9).
Macromolecular Absorption From The Digestive Tract In Young Vertebrates
Károly Baintner in Intestinal Absorption of Macromolecules and Immune Transmission from Mother to Young, 2019
I discuss separately N-acetyls-hexosaminidase, an enzyme occuring in the distal intestine with an optimum between pH 4.0 and 4.5.738 It occurs in both soluble and particle-bound form in mucosal homogenates. The activity was demonstrated in granules attached to the internal surface of ACS vesicles. After releasing the granules from the membrane in 10 mM CaCl2 solution, they were resolved by gel filtration to N-acetyl-hexosaminidase and to a filamentous protein (“ligatin”), which attaches the enzyme to the membrane.610,1209 The enzyme has both N-acetyl-β-glucosidase and N-acetyl-β-galactosidase activities, but it differs from TV-acetyl-neuraminidase, which splits alpha-glycosidic bonds.1262 N-acetyl-hexosamin-idase is an exoenzyme. It splits hexosamines from the end of carbohydrate chains and disappears at closure time together with the vacuolated cells.742, 738
Aeromonas
Dongyou Liu in Handbook of Foodborne Diseases, 2018
Type II, III, and VI secretion systems (T2SS, T3SS, and T6SS) are linked to the virulence of A. dhakensis SSU.79T2SS is involved in the extracellular secretion of a wide range of virulence factors, such as aerolysin and cytotoxic enterotoxin Act.79,87 T3SS functions as a molecular needle injecting effector toxins into host cells.88 T3SS-associated exoenzyme effector (AexU) inhibits macrophage phagocytosis and causes host cell apoptosis, disruption of actin filament, and lethality in mice.89–91 T6SS has been implicated in the translocation of a potential effector protein into eukaryotic cells.92 Valine glycine repeat G (VrgG) proteins and hemolysin coregulated protein (Hcp) are important effectors secreted by T6SS. VrgG family proteins exerted cytotoxic effects by ADP-ribosylation of actin, leading to disruption of actin cytoskeleton, a decrease in cell viability, and an increase in apoptosis.93 Hcp binds to macrophages, and impairs recruitment and inhibition of phagocytosis by producing immunosuppressive cytokines, IL-10 and TGF-ß, and causes apoptosis of host cells through activation of caspase-3.94 Collectively, the pathogenesis of Aeromonas infection is multifactorial, and several virulence genes act in concert to cause human diseases. However, there remain considerable unexplored virulence mechanisms that deserve future research.
Stenotrophomonas maltophilia – a low-grade pathogen with numerous virulence factors
Published in Infectious Diseases, 2019
Angelina Trifonova, Tanya Strateva
The gelatinase production of S. maltophilia is an important biochemical characteristic of the species (over 85% of the strains are producers). Although in other bacteria the enzyme participates in biofilm formation, host tissue degradation, and avoidance of immune response by inactivating the complement system [29], data on its role as a virulence factor in S. maltophilia are scarce [1,6]. A case of ecthyma gangrenosum due to bacteraemia with S. maltophilia was reported in a patient with leukaemia [17]. The exoenzyme profile of the isolate included both gelatinase and elastase. One of the functions of elastase is degradation of the elastic lamina of blood vessels facilitating release of bacterial cells into subcutaneous tissue [17]. A study of clinical S. maltophilia isolates established that elastase activity is dependent on incubation time and temperature (all tested strains demonstrate elastin hydrolysis at 30 °C after 72 h). According to the authors, previous results showing a low prevalence of the enzyme, are due to absence of standard methodology in laboratory practice [30].
Characterization of biological peculiarities of the radioprotective activity of double-stranded RNA isolated from Saccharomyces сerevisiae
Published in International Journal of Radiation Biology, 2020
Genrikh S. Ritter, Valeriy P. Nikolin, Nelly A. Popova, Anastasia S. Proskurina, Polina E. Kisaretova, Oleg S. Taranov, Tatiana D. Dubatolova, Evgenia V. Dolgova, Ekaterina A. Potter, Svetlana S. Kirikovich, Yaroslav R. Efremov, Sergey I. Bayborodin, Margarita V. Romanenko, Maria I. Meschaninova, Aliya G. Venyaminova, Nikolay A. Kolchanov, Mikhail A. Shurdov, Sergey S. Bogachev
In the case of ‘denaturation’, exposure to RNase A results in hydrolysis of single-stranded RNA molecules, which could not re-associate, and the effect of radioprotection disappears. If RNase is added during ‘renaturation’, then the radioprotectivity restoration can be explained as follows. Upon the hairpin formation, the resulting dsRNA molecule bears a single-stranded loop on the one end, and this structure, for some reason, cannot be used as a template in the DSB repair process. The reason can be either a steric obstacle for complementation of processed ends in the site of chromatin break, or the absence of essential structural components (3′-OH and 5′-phosphate ends). RNase A cannot hydrolyze the double-stranded form of RNA, but easily degrade the single-stranded loops of the formed hairpins (endo/exoenzyme). As a result, a shorter than in initial ‘0.25 M’ fraction, but nonetheless double-stranded RNA molecule, which can be used as an extrachromosomal template in the repair process, is formed (Figure 7).
Dual transcriptome of Streptococcus mutans and Candida albicans interplay in biofilms
Published in Journal of Oral Microbiology, 2023
Yan Zeng, Elena Rustchenko, Xinyan Huang, Tong Tong Wu, Megan L. Falsetta, Jin Xiao
Understanding the molecular basis for microbial interactions is critical to developing a new therapeutic strategy for oral polymicrobial infectious diseases, such as dental caries related to S. mutans and C. albicans colonization. In recent years, various studies focused on the role/contributions of S. mutans-derived exoenzyme glucosyltransferase B (gtfB), synergistic carbohydrate metabolism, and enhanced sugar metabolism in S. mutans and C. albicans mixed-species biofilms. This mixed-species biofilm contains an extensive matrix of extracellular α-glucans, which is produced by S. mutans gtfB. gtfB gene readily binds to C. albicans cells strongly and stably in an active form [30]. Mannans locates on the outer surface of C. albicans cell-wall mediates gtfB gene binding, enhancing glucan-matrix production and modulating bacterial-fungal association within the biofilm. S. mutans-secreted gtfB gene binds to the mannan layer of C. albicans to promote extracellular matrix formation and their co-existence within biofilms [31].