Mycobacterium is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis and leprosy in humans. The Greek prefix myco- means 'fungus', alluding to this genus' mold-like colony surfaces. Since this genus has cell walls with a waxy lipid-rich outer layer that contains high concentrations of mycolic acid, acid-fast staining is used to emphasize their resistance to acids, compared to other cell types.
Virulence is a pathogen's or microorganism's ability to cause damage to a host.
Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secretory portals at the plasma membrane called porosomes. Porosomes are permanent cup-shaped lipoprotein structures embedded in the cell membrane, where secretory vesicles transiently dock and fuse to release intra-vesicular contents from the cell.
Pathogenicity islands (PAIs), as termed in 1990, are a distinct class of genomic islands acquired by microorganisms through horizontal gene transfer. Pathogenicity islands are found in both animal and plant pathogens. Additionally, PAIs are found in both gram-positive and gram-negative bacteria. They are transferred through horizontal gene transfer events such as transfer by a plasmid, phage, or conjugative transposon. Therefore, PAIs contribute to microorganisms' ability to evolve.
Mycobacterium smegmatis is an acid-fast bacterial species in the phylum Actinomycetota and the genus Mycobacterium. It is 3.0 to 5.0 μm long with a bacillus shape and can be stained by Ziehl–Neelsen method and the auramine-rhodamine fluorescent method. It was first reported in November 1884 by Lustgarten, who found a bacillus with the staining appearance of tubercle bacilli in syphilitic chancres. Subsequent to this, Alvarez and Tavel found organisms similar to that described by Lustgarten also in normal genital secretions (smegma). This organism was later named M. smegmatis.
In cell biology, a phagosome is a vesicle formed around a particle engulfed by a phagocyte via phagocytosis. Professional phagocytes include macrophages, neutrophils, and dendritic cells (DCs).
Yersinia pseudotuberculosis is a Gram-negative bacterium that causes Far East scarlet-like fever in humans, who occasionally get infected zoonotically, most often through the food-borne route. Animals are also infected by Y. pseudotuberculosis. The bacterium is urease positive.
Cholera toxin is an AB5 multimeric protein complex secreted by the bacterium Vibrio cholerae. CTX is responsible for the massive, watery diarrhea characteristic of cholera infection. It is a member of the heat-labile enterotoxin family.
Lipoarabinomannan, also called LAM, is a glycolipid, and a virulence factor associated with Mycobacterium tuberculosis, the bacteria responsible for tuberculosis. Its primary function is to inactivate macrophages and scavenge oxidative radicals.
Host tropism is the infection specificity of certain pathogens to particular hosts and host tissues. This explains why most pathogens are only capable of infecting a limited range of host organisms.
The type III secretion system is one of the bacterial secretion systems used by bacteria to secrete their effector proteins into the host's cells to promote virulence and colonisation. While the type III secretion system has been widely regarded as equivalent to the injectisome, many argue that the injectisome is only part of the type III secretion system, which also include structures like the flagellar export apparatus. The T3SS is a needle-like protein complex found in several species of pathogenic gram-negative bacteria.
ESAT-6 or early secreted antigenic target 6 kDa, is produced by Mycobacterium tuberculosis, it is a secretory protein and potent T cell antigen. It is used in tuberculosis diagnosis by the whole blood interferon γ test QuantiFERON-TB Gold, in conjunction with CFP-10.
Listeriolysin O (LLO) is a hemolysin produced by the bacterium Listeria monocytogenes, the pathogen responsible for causing listeriosis. The toxin may be considered a virulence factor, since it is crucial for the virulence of L. monocytogenes.
Rhodococcus equi is a Gram-positive coccobacillus bacterium. The organism is commonly found in dry and dusty soil and can be important for diseases of domesticated animals. The frequency of infection can reach near 60%. R. equi is an important pathogen causing pneumonia in foals. Since 2008, R. equi has been known to infect wild boar and domestic pigs. R. equi can infect immunocompromised people, such as HIV-AIDS patients or organ transplant recipients. Rhodococcus equi infection in these populations resemble the clinical and pathological signs of advanced pulmonary tuberculosis. This organism is a facultative intracellular mycobacterial pathogen.
The type 2 secretion system is a type of protein secretion machinery found in various species of Gram-negative bacteria, including many human pathogens such as Pseudomonas aeruginosa and Vibrio cholerae. The type II secretion system is one of six protein secretory systems commonly found in Gram-negative bacteria, along with the type I, type III, and type IV secretion systems, as well as the chaperone/usher pathway, the autotransporter pathway/type V secretion system, and the type VI secretion system. Like these other systems, the type II secretion system enables the transport of cytoplasmic proteins across the lipid bilayers that make up the cell membranes of Gram-negative bacteria. Secretion of proteins and effector molecules out of the cell plays a critical role in signaling other cells and in the invasion and parasitism of host cells.
Joyoti Basu is an Indian biochemist, cell biologist and a senior professor at the Bose Institute. Known for her studies on the membrane structure of red blood cells, Basu is an elected fellow of all three major Indian science academies, namely the National Academy of Sciences, India, the Indian Academy of Sciences and the Indian National Science Academy, as well as the Indian Society for Chemical Biology. The Department of Biotechnology of the Government of India awarded her the National Bioscience Award for Career Development, one of the highest Indian science awards, for her contributions to biosciences in 2002.
Bacterial secretion systems are protein complexes present on the cell membranes of bacteria for secretion of substances. Specifically, they are the cellular devices used by pathogenic bacteria to secrete their virulence factors to invade the host cells. They can be classified into different types based on their specific structure, composition and activity. Generally, proteins can be secreted through two different processes. One process is a one-step mechanism in which proteins from the cytoplasm of bacteria are transported and delivered directly through the cell membrane into the host cell. Another involves a two-step activity in which the proteins are first transported out of the inner cell membrane, then deposited in the periplasm, and finally through the outer cell membrane into the host cell.
MTBVAC is a candidate vaccine against tuberculosis in humans currently in research trials. It is based on a genetically modified form of the Mycobacterium tuberculosis pathogen isolated from humans.
Type VII secretion systems are bacterial secretion systems first observed in the phyla Actinomycetota and Bacillota. Bacteria use such systems to transport, or secrete, proteins into the environment. The bacterial genus Mycobacterium uses type VII secretion systems (T7SS) to secrete proteins across their cell envelope. The first T7SS system discovered was the ESX-1 System.
The KdpD/KdpE two-component system is a regulatory system involved in controlling potassium transport and intracellular osmolarity of pathogenic bacteria. It plays an important role in potassium transport for osmoregulation of bacteria. In some bacteria, it can act as a virulence factor and acquire new adaptations from different selective pressures in the environment. It is also demonstrated to maintain internal pH, stress responses, enzyme activation, and gene expression. K+ ions are used for necessary biological processes and can generate a negative electric potential on the cytoplasmic side of the plasma membrane. There are different uptake systems for K+ ions, but the specific mechanisms vary between species.
