Bacterium toxicity

Aeromonas hydrophila is a bacterium that causes diarrheal diseases and deep wound infections. These complications arise due to pore formation in sensitive cells by the protein toxin aerolysin. Proteolytic processing of the 52-kD precursor proaerolysin (Figure 10.34) produces the toxic form of the protein, aerolysin. Like a-hemolysin, aerolysin monomers associate to form a heptameric transmembrane pore. Michael Parker and coworkers have proposed... 

Bacillus thuringiensis produces a variety of organic compounds which are toxic to the larvae of certain susceptible insect hosts. Among the toxic entities are proteinaceous crystals, probably three soluble toxins, and certain enzymes. The protein material is the major toxin active in killing lepidopterous larvae. The protein is formed by the cells apparently in close synchrony with sporulation, and its nature is a constant function of bacterial strain. The mode of action of the protein is under study. The sequence of events in the pathology observed is probably solubilization of the crystal (enzymatic or physical)—>liberation of toxic unit—>alteration of permeability of larval gut wall— change in hemolymph pH—>invasion of hemolymph by spores or vegetative cells of the bacterium. 

Preparations of the bacterium Bacillus thuringiensis (BT) are applied as sprays to control insect pests on agricultural crops. The bacterium produces endotoxins that are highly toxic to insects. 

Mergeay M, S Monchy, T Vallaeys, V Auquier, A Benotmane, P Berlin, S Taghavi, J Dunn, D van der Lelie, R Wattiez (2003) Ralstonia metallidurans, a bacterium specifically adapted to toxic metals towards a catalogue of metal-responsive genes. EEMS Micobiol Rev 27 385-410. 

Bioluminescence can be used for spedfic detection of separated bioactive compounds on layers (BioTLC) [46]. After development and drying the mobile phase by evaporation, the layer is coated with microorganisms by immersion of the plate. Single bioactive substances in multicomponent samples are located as zones of differing luminescence. The choice of the luminescent cells determines the specificity of detection. A specific example is the use of the marine bacterium Vibrio fischeri with the BioTLC format. The bioluminescence of the bacteria cells on the layer is reduced by toxic substances, which are detected as dark zones on a fluorescent background. BioTLC kits are available from ChromaDex, Inc. (Santa Ana, CA). 

Drzyzga O, Jannsen S, Blotevogel KH (1995) Toxicity of diphenylamine and some of its nitrated and aminated derivatives to the luminescent bacterium vibrio fischeri. Environ Safety 31(12) 149-152... 

Organic matter is also the essential component of natural soils and its association with microorganisms may influence the behavior and fate of toxic metals. A variety of batch complexation experiments were performed by Borrok et al. (2007) in single, binary and ternary systems for the three components natural organic matter (NOM), bacterium (B. subtilis) and metals (Pb, Cu, Cd, and Ni) to determine the significance of ternary complexation. They found that the formation of bacteria-metal-NOM complex is a rapid, fully-reversible chemical process. The stability of bacteria-metal-NOM complexes increases with the decrease of pH. All NOM fractions form ternary complexes to similar extents at circumneutral pH, but humic acid becomes the dominant NOM fraction in ternary complexes at low pH. The abundance of humic acid in ternary form is greatest with Ni or Cd systems and less with Pb and Cu systems. Their results suggest that... 

Unlike selenium there is no required biological role for tellurium in bacteria or plants that has been determined however, this may ultimately not be the whole story.111 Selenium was only viewed as a toxic metalloid with no necessary role for metabolism until at least the 1950s see above. While tellurite is less soluble than tellurate in aqueous solution, in general tellurite is probably more toxic to most organisms.190 The non Te-resistant wild type E. coli bacterium (Gramnegative) has MICs of 1 to 3 ppm for tellurite and tellurate.144,191,192 Tellurite is used to enrich and select for Staphylococcus aureus.169,193,194... 

Boyd, E.M., Meharg, A.A., Wright, J., and Killham, K. Toxicity of chlorobenzenes to a /ux-marked terrestrial bacterium. Pseudomonas fluorescens. Environ. Toxicol. Chem., 17(11) 2134-2140, 1998. 

Jonsson, S. and Baun, A. Toxicity of mono- and diesters of o-phthalic esters to a crustacean, a green alga, and a bacterium. Environ. Toxicol Chem., 22(12) 3037-3043, 2003. 

Lajoie, C.A. Lin, S.C. Nguyen, H. Kelly, C.J. A toxicity testing protocol using a bioluminescent reporter bacterium from activated sludge. J. Microbiol. Methods 2002, 50, 273-282. 

Much information on the mechanism of action and cross-resistance of purine analogues has been obtained in bacteria, some of which are quite sensitive to certain of these compounds in vitro. There is a great deal of variation in response of the various bacteria to a particular agent and of a particular bacterium to the various cytotoxic purine analogues. Some, if not most, of these differences are probably due to differences in the anabolism of the various compounds. Despite the fact that certain purine analogues have quite a spectrum of antibacterial activity in vitro, none has been useful in the treatment of bacterial infections in vivo because their toxicity is not selective—the metabolic events whose blockade is responsible for their antibacterial activity are also blocked in mammalian cells and thus inhibition of bacterial growth can only be attained at the cost of prohibitive host toxicity. In contrast, the sulpha drugs and antibiotics such as penicillin act on metabolic events peculiar to bacteria. 

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