Query: NC_017179:1133510 Clostridium difficile BI1, complete genome
Lineage: Peptoclostridium difficile; Peptoclostridium; Peptostreptococcaceae; Clostridiales; Firmicutes; Bacteria
General Information: Clostridium difficile BI1 is a human strain isolated in the United States in 1988. This species is now recognized as the major causative agent of pseudomembranous colitis (inflammation of the colon) and diarrhea that may occur following antibiotic treatment. C. difficile infection represents one of the most common nosocomial (originating in a hospital) infections. This bacterium causes a wide spectrum of disease, ranging from mild, self-limiting diarrhea to serious diarrhea and, in some cases, complications such as pseudomembrane formation, toxic megacolon (dilation of the colon) and peritonitis, which often lead to lethality among patients. The bacteria produce high molecular mass polypeptide cytotoxins, A and B. Some strains produce only one of the toxins, others produce both. Toxin A causes inflammatory reaction involving hypersecretion of fluid and hemorrhagic necrosis through triggering cytokine release by neutrophils. Cytotoxin B depolymerizes actin, the major protein of the cytoskeleton, and thus aids in destruction of tissues. The combined action of the toxins results in necrosis of superficial epithelium and edema (fluidic swelling) in affected areas of intestine. Proliferation of C. difficile is normally prevented by normal intestinal microflora, which is believed to inhibit attachment of the bacterium and its toxins to intestinal walls. Alteration of intestinal microbial balance with antibiotic therapy and increased exposure to the bacterium in a hospital setting allows C. difficile to colonize susceptible individuals. Moreover, it has been shown that subinhibitory concentrations of antibiotics promote increased toxin production by C. difficile.
Subject: NC_005957:4311679 Bacillus thuringiensis serovar konkukian str. 97-27, complete
Lineage: Bacillus thuringiensis; Bacillus; Bacillaceae; Bacillales; Firmicutes; Bacteria
General Information: This organism was isolated from a case of severe human tissue necrosis which is unusual since human infections by this organism are rare. Produces insect toxinT his organism, also known as BT, is famous for the production of an insecticidal toxin. The bacterium was initially discovered as a pathogen of various insects and was first used as an insecticidal agent in the early part of this century. This organism, like many other Bacilli, is found in the soil, where it leads a saprophytic existence, but becomes an opportunistic pathogen of insects when ingested. The specific activity of the toxin towards insects and its lack of toxicity to animals has made this organism a useful biocontrol agent. The delta-endotoxin, which is produced during the sporulation part of the life cycle, causes midgut paralysis and disruption of feeding by the infected insect host. The delta-endotoxin, which is produced during the sporulation part of the life cycle, causes midgut paralysis and disruption of feeding by the infected insect host. The delta-endotoxin, which is produced during the sporulation part of the life cycle, causes midgut paralysis and disruption of feeding by the infected insect host. The presence of a parasporal crystal, which is outside the exosporium of the endospore, is indicative of production of the toxin, and serves as a marker for this species.Activation of the toxin typically requires a high pH environment such as the alkaline environments in insect midguts followed by proteolysis. Various toxin genes specific for a variety of insects have been studied, and many are now being used in genetically modified plants which have been engineered to produce the toxin themselves, eliminating the need to produce sufficient amounts of B. thuringiensis spores.