Pathogenic bacteria, factors

Studies on S-layers present on the cell envelopes of a great variety of pathogenic organisms [100] revealed that these crystalhne arrays can represent important virulence factors. Most detailed studies have been performed on the fish pathogenic bacteria Aeromonas salmonicida and Aeromonas hydrophila [102] and the human pathogen Campylobacter fetus uh p. fetus [103] and Bacillus anthracis [104]. For example, whole-cell preparations or partially purified cell products are currently used as attenuated vaccines against various fish pathogens [102,105]. 

Low-iron stress in the host is a signal for pathogenic bacteria to induce virulence factors, such as Shiga-like toxin and haemolysins (although haemolysins could also help to obtain iron from lysed cells and could be grouped under iron uptake ). 

Obviously siderophores can be potent virulence factors of pathogenic bacteria. Siderophores in many cases have elaborate structures providing recognition only by the receptor site of the producing species. This renders a pirating by competing microorganisms more difficult. The structural specificities of siderophores have been used for classification purposes of bacterial species (see especially pyoverdins, Sect. 2.1). 

Urease (urea amidohydrolase) is an enzyme first identified over a hundred years ago in bacterial extracts [22], The presence of urease is a virulence factor for some pathogenic bacteria [23,24], It is now known to occur also in plants, fungi, and invertebrates (see [24,25] for reviews). Urease from jack bean was the first enzyme to be crystallized, in 1926. Almost 50 years later its metal content was reexamined and it was found to contain two atoms of nickel per subunit [26]. Finally in 1995 the crystal structure of the enzyme from the enteric bacterium Klebsiella aerogenes was determined [27], Amino-acid sequence comparisons predict that the structures of the plant and bacterial enzymes are similar, although with different subunit arrangements. 

What factor controls the pH in the vaginal lumen at between pH 4 and pH 5, preventing the proliferation of pathogenic bacteria ... 

At the turn of the century. Dr. William B. Coley, a young surgeon in New York City, made the remarkable discovery that injection of live or inactivated pathogenic bacteria into patients with otherwise incurable cancers would oftentimes induce dramatic necrosis (a specific type of cell death) and regression of the tumors. Owing to a nmnber of factors including lack of standardization of the potency of the bacterial injections, toxic side effects, variability and sometimes total lack of effect, and the simultaneous advent of radiotherapy, these intriguing results were not followed up until much later. 

Circulating proenzymes of the blood clotting factors, of the complement system (Chapter 31), represent a specialized group of secreted signaling proteins that are able to initiate important defensive cascades. Proteases also act more directly in defense systems of the body. For example, serine proteases cause lysis of the target cells of cytotoxic T lymphocytes (Chapter 31) and activated neutrophils (Chapter 18). At the same time, pathogenic bacteria often secrete proteases that assist in attack on their hosts and schistosomes secrete an elastase that helps them penetrate skin and invade their hosts. ... 

Neutrophils arc the primary innate defense against pathogenic bacteria. They make up most (SO to 75(3>) of the leukocyte fraction in the bhxid. Micro.scopically. neutrophils have mullilobcd nuclei. They respond to chemical motility factors such as complement mediators released from infected i>r inflamed tissues and migrate to a site of infection by the process of chemotaxis. There, they recognize, adhere to, and phagocytose invading microbes. 

Cancer cells can form from normal cells when DNA and/or RNA is modified or mutated, either spontaneously or as a result of any number of external factors, including radiation, chemicals and toxins, pathogens (bacteria, viruses, fungi, and parasites), and the water and food we ingest. If the immune system is not functioning properly or is overburdened, cancer cells can proliferate and effectively overpower its capacity to destroy them. 

Facultative pathogenic bacteria use many complex systems to enable them to sense and adapt to environmental stresses. These systems then provide signals for the appropriate expression of genes to encode colonization and pathogenicity factors (Merrell and Camilli, 1999). 

In pathogenic bacteria, SOD may be a virulence factor. Strains of Mycobacterium tuberculosis and Nocardia asteroides that secrete FeSOD during logarithmic phase growth are resistant to phagocytic attack, while non-secreting strains are less virulent. 

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