Pseudomonad

Triazines pose rather more of a problem, probably because the carbons are in an effectively oxidized state so that no metaboHc energy is obtained by their metaboHsm. Very few pure cultures of microorganisms are able to degrade triazines such as Atrazine, although some Pseudomonads are able to use the compound as sole source of nitrogen in the presence of citrate or other simple carbon substrates. The initial reactions seem to be the removal of the ethyl or isopropyl substituents on the ring (41), followed by complete mineralization of the triazine ring. 

The earliest commercially available filters were manufactured in two pore sizes 0.45 and 0.8 pm. The 0.45 pm-rated membranes were considered to be stefilizing-grade filters and were successfully used in the sterile filtration of pharmaceuticals and parenterals. The membrane filters were qualified using Serratia marcescens a standard bacterium, having dimensions of 0.6 x 1 pm. However, in the late 1960s it became apparent that the matrix of the 0.45 pm-rated filters could be penetrated by some pseudomonad-like organisms (1). For sterile filtration apphcations in the 1990s, 0.2 pm-rated membranes are the industry standard in the manufacture of sterile parenterals and pharmaceuticals. 

The fermentative fixing of CO2 and water to acetic acid by a species of acetobacterium has been patented acetyl coen2yme A is the primary reduction product (62). Different species of clostridia have also been used. Pseudomonads (63) have been patented for the fermentation of certain compounds and their derivatives, eg, methyl formate. These methods have been reviewed (64). The manufacture of acetic acid from CO2 and its dewatering and refining to glacial acid has been discussed (65,66). 

Pseudomonas. These gram-aegative bacteria are a diverse group of microbes that iahabit plants, water, and sod. Pseudomonads are metabohcaHy versatile, capable of carrying out chemical transformations, mineralization of organic compounds, and colonization on plant roots (16). The use of Pseudomonads strains ia the clean up of chemical wastes and od spills has drawn considerable attention. 

Pseudomonads also have the abiUty for xenobiotic metaboHsm and are capable of carrying out diverse sets of chemical reactions. Pseudomonas species is used ia the commercial productioa of acrylamide (qv) (18). Several operoas iavolved ia the metaboHsm of xeaobiotic compouads have beea studied. Use of Pseudomonads for the clean up of the environment and for the production of novel chemical iatermediates is likely to be an area of active research ia the 1990s. 

Moxalactam is a synthetic antibiotic with good activity against Gram-negative bacteria including pseudomonads and has... 

AC A, 7-ADCA, and their organic acid esters Corresponding cephalosporins (cephalexin, cephaloglycine) Kluyvera citrophiia Xanthomonas dtm and other pseudomonads... 

Selective media for pseudomonads. These media depend on the relative resistance of pseudomonads to the quaternary ammonium disinfectant cetrimide. In some recipes the antibiotic nalidixic acid (Chapter 5) is added, to which pseudomonads are also resistant. 

Aminoglycosides staph, aureus (gentamicin) Conforms, pseudomonads... 

Burkholderia (formeriy Pseudomonas) cepacia is intrinsically resistant to a number of biocides, notably benzalkonium chloride and chlorhexidine. Again, the outer membrane is likely to act as a permeability barrier. By contrasL Ps. stutzeri (an organism implicated in eye infections caused by some cosmetic products) is invariably intrinsically sensitive to a range of biocides, including QACs and chlorhexidine. This organism contains less wall muramic acid than other pseudomonads but it is imclear as to whether this could be a contributory factor in its enhanced biocide susceptibility. 

However, inoculum size alone is not always a rehable indicator of likely spoilage potential. A very low level of s, aggressive pseudomonads in a weakly preserved solution may suggest a greater risk than tablets containing fairly high numbers of fungal and bacterial spores. 

In order to lessen the risk of eye-drops becoming heavily contaminated either by repeated inoculation or growth of resistant organisms in the solntion, use is restricted, after the container is first opened, to 1 month. This is nsnally reduced to 7 days for hospital ward use on one eye of a single patient. The period is shorter in the hospital environment because of the greater danger of contamination by potential pathogens, particnlarly pseudomonads. 

The oxidation of benzo[( ]thiophene by strains of pseudomonads produces the sulfoxide that undergoes an intramolecular Diels-Alder reaction followed by further transformation to benzo[fc]naphtho[l,2- (]thiophene (Figure 2.2b) (Kropp et al. 1994). 

A taxonomic note there have been substantial developments in the taxonomy of pseudomonads, and many new genera have been proposed including, for example, Sphingomonas, Comamonas, and Variovorax, while denitrifying organisms described as pseudomonads have been referred to the general Thauera and Azoarcus (Anders et al. 1995). 

Anders H-J, A Kaetzke, P Kampfer, W Ludwig, G Fuchs (1995) Taxonomic position of aromatic-degrading denitrifying pseudomonad strains K 172 and KB 740, and their description as new members of the genera Thauera, as Thauera aromatica sp. nov., and Azoarcus, as Azoarcus evansii sp. nov., respectively, members of the beta subclass of the Protobacteria. Int J Syst Bacterial 45 327-333. 

Wang Y, PCK Lau, DK Button (1996) A marine oligobacterium harboring genes known to be part of aromatic hydrocarbon degradation pathways of soil pseudomonads. Appl Environ Microbiol 62 2169-2173. 

Cournoyer B, S Watanabe, A Vivian (1998) A tellurite-resistance genetic determinant from pathogenic pseudomonads encodes a thiopurine methyltransferase evidence of a widely conserved family of methyltransferases. Biochim Biophys Acta 1397 161-168. 

FIGURE 4.1 Degradation of parathion by a mixed culture of two pseudomonads. 

The last example is mediated by a monooxygenase that can be induced by benzene, toluene, and ethylbenzene, and also by xylenes and styrene. A plausibly analogous situation exists for strains of Pseudomonas sp. and Rhodococcus erythropolis that were obtained by enrichment with isopropylbenzene, and that could be shown to oxidize trichloroethene (Dabrock et al. 1992). In addition, one of the pseudomonads could oxidize 1,1-dichloroeth-ene, vinyl chloride, trichloroethane, and 1,2-dichloroethane. 

Connors MA, EA Barnsley (1982) Naphthalene plasmids in pseudomonads. J Bacteriol 149 1096-1101. 

Haller HD, RK Finn (1978) Kinetics of biodegradation of /)-nitrobenzoate and inhibition by benzoate in a pseudomonad. Appl Environ Microbiol 35 890-896. 

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