Degradation of triphenyltin by a fluorescent pseudomonad

Triphenyltin (TPT)-degrading bacteria were screened by a simple technique using a post-column high-performance liquid chromatography using 3,3',4',7-tetrahydroxyflavone as a post-column reagent for determination of TPT and its metabolite, diphenyltin (DPT). An isolated strain, strain CNR15, was identified as Pseudomonas chlororaphis on the basis of its morphological and biochemical features. The incubation of strain CNR15 in a medium containing glycerol, succinate, and 130 microM TPT resulted in the rapid degradation of TPT and the accumulation of approximately 40 microM DPT as the only metabolite after 48 h. The culture supernatants of strain CNR15, grown with or without TPT, exhibited a TPT degradation activity, whereas the resting cells were not capable of degrading TPT. TPT was stoichiometrically degraded to DPT by the solid-phase extract of the culture supernatant, and benzene was detected as another degradation product. We found that the TPT degradation was catalyzed by low-molecular-mass substances (approximately 1,000 Da) in the extract, termed the TPT-degrading factor. The other fluorescent pseudomonads, P. chlororaphis ATCC 9446, Pseudomonas fluorescens ATCC 13525, and Pseudomonas aeruginosa ATCC 15692, also showed TPT degradation activity similar to strain CNR15 in the solid-phase extracts of their culture supernatants. These results suggest that the extracellular low-molecular-mass substance that is universally produced by the fluorescent pseudomonad could function as a potent catalyst to cometabolite TPT in the environment.     

Degradation of 2-bromo-, 2-chloro- and 2-fluorobenzoate by Pseudomonas putida CLB 250

Abstract Pseudomonas putida strain CLB 250 (DSM 5232) utilized 2-bromo-, 2-chloro- and 2-fluorobenzoate as sole source of carbon and energy. Degradation is suggested to be initiated by a dioxygenase liberating halide in the first catabolic step. After decarboxylation and rearomatization catechol is produced as a central metabolite which is degraded via the ortho-pathway. After inhibition of ring cleavage activities with 3-chlorocatechol, 2-chlorobenzoate was transformed to catechol in nearly stoichiometric amounts. Other ortho -substituted benzoates like anthranilate and 2-methoxybenzoate seem to be metabolized via the same route.     

Degradation of 2-bromo-, 2-chloro- and 2-fluorobenzoate by Pseudomonas putida CLB 250

Pseudomonas putida strain CLB 250 (DSM 5232) utilized 2-bromo-, 2-chloro- and 2-fluorobenzoate as sole source of carbon and energy. Degradation is suggested to be initiated by a dioxygenase liberating halide in the first catabolic step. After decarboxylation and rearomatization catechol is produced as a central metabolite which is degraded via the ortho-pathway. After inhibition of ring cleavage activities with 3-chlorocatechol, 2-chlorobenzoate was transformed to catechol in nearly stoichiometric amounts. Other ortho-substituted benzoates like anthranilate and 2-methoxybenzoate seem to be metabolized via the same route.     

Metabolism of beta-methylaspartate by a pseudomonad

A bacterium was isolated from soil which utilizes threo-beta-methyl-l-aspartate, certain other amino acids, and a variety of organic substances as single energy sources. It is, or closely resembles, Pseudomonas putida biotype B. The ability of this organism to rapidly decompose such amino acids is dependent on inducible enzyme systems. Dialyzed cell-free extracts of this bacterium metabolize beta-methylaspartate only when catalytic amounts of alpha-ketoglutarate, or pyruvate, and pyridoxal phosphate are also present. The main products formed from beta-methylaspartate under these conditions are alpha-aminobutyrate, carbon dioxide, and alpha-ketobutyrate. When l-aspartate is substituted for beta-methylaspartate in this system, it is converted mainly to alanine and carbon dioxide. beta-Methyloxalacetate is decarboxylated, and the resulting alpha-ketobutyrate is converted enzymatically in the presence of glutamate to alpha-aminobutyrate which accumulates. The added keto acids are converted, in part, to the corresponding amino acids probably by transamination. The data indicate that beta-methylaspartate is converted to alpha-aminobutyrate, and aspartate to alanine, by a circuitous transamination-beta-decarboxylation-transamination sequence rather than by a direct beta-decarboxylation.     

Anaerobic degradation of 2-fluorobenzoate by benzoate-degrading, denitrifying bacteria.

Three strains of anaerobically benzoate-degrading, denitrifying bacteria of the genus Pseudomonas were able to grow on 2-fluorobenzoate as the sole carbon and energy source. Fluoride ion release was stoichiometric, and the reduction of dissolved organic carbon indicated total degradation. Cells grown anaerobically with benzoate were adapted for immediate growth with 2-fluorobenzoate, and both compounds were substrates for an inducible benzoyl-coenzyme A synthetase, the initial enzyme of anaerobic degradation. It is proposed that fluoride is eliminated gratuitously by a regioselective reaction in a sequence common to both carbon sources. Benzoate, but not 2-fluorobenzoate, was oxidized by aerobically grown cells.     

Degradation of aniline and monochloroanilines by Rhodococcus sp. An 117 and a pseudomonad: a comparative study

Two newly isolated aniline-degrading bacterial strains were characterized with regard to their enzyme systems responsible for aniline catabolism. One of them identified as a Rhodococcus sp. metabolized aniline exclusively via the beta-ketoadipate pathway by means of inducible enzymes. The aniline-degrading enzyme system of the second isolate, presumably a pseudomonad, was shown to consist of an inducible aniline-converting enzyme and constitutive meta-pathway enzymes. Both isolates failed to metabolize monochlorinated anilines in the absence of additional carbon sources. To explain this the ring-cleaving enzymes of both isolates were examined for their substrate specificities. Furthermore, the effect of 4-chlorocatechol on the enzymes catalyzing aniline conversion and catechol oxygenation was investigated.     

The metabolism of nitrilotriacetate by a pseudomonad

1. An organism that grows on nitrilotriacetate as sole source of carbon and energy was isolated in pure culture and was identified as a pseudomonad. 2. Cell-free extracts of the nitrilotriacetate-grown pseudomonad contain an enzyme that catalyses the NADH-and O(2)-dependent oxidation of nitrilotriacetate to iminodiacetate and glyoxalate. This enzyme is absent from extracts of glucose-grown cells. 3. Compared with growth on glucose, growth on nitrilotriacetate results in increased activities of enzymes of glycine and serine metabolism, namely serine hydroxymethyltransferase, glycine decarboxylase, serine-oxaloacetate aminotransferase and hydroxypyruvate reductase. 4. Cell-free extracts of the nitrilotriacetate-grown organism contain the enzyme glyoxalate carboligase and, when supplemented with NADH, Mg(2+) and thiamin pyrophosphate, can catalyse the anaerobic conversion of glyoxalate into glycerate. 5. These results are incorporated in a scheme which shows the oxidative metabolism of nitrilotriacetate by the successive removal of C(2) units to form 2mol of glyoxalate and 1mol of glycine per mol of nitrilotriacetate degraded. The glyoxalate and glycine are then both metabolized to glycerate by separate pathways, via tartronic semialdehyde and serine respectively. The role of this scheme in the growth of the organism on nitrilotriacetate is discussed.     

Diminution of outer membrane permeability by Mg2+ in a marine pseudomonad.

Intact cells of the marine pseudomonad MB-45, in the presence of optimal Mg2+, exhibited little alkaline phosphatase activity as judged by the hydrolysis of p-nitrophenylphosphate. Sonic extracts, in contrast, were rich in this activity. Removal of the loosely bound outer layer did not diminish this crypticity of alkaline phosphatase, but decreasing the concentration of Mg2+ in the suspending medium progressively exposed the alkaline phosphatase. Since MB-45 did not liberate alkaline phosphatase into the surrounding medium even in the absence of Mg2+ and since this enzyme is localized in the periplasmic space, it can be concluded that the crypticity was due to the exclusion of p-nitrophenylphosphate by the outer membrane. Mg2+ is apparently essential for the full expression of this limited permeability.     

Utilization of cutin by a pseudomonad isolated from soil

Summary A Pseudomonas sp., which has been isolated from orchard soil, is able to utilize cutin as a sole source of carbon. Products obtained from the culture filtrate corresponded to that obtained by alkaline hydrolysis of cutin.     

Degradation of triglycerides by a pseudomonad isolated from milk: molecular analysis of a lipase-encoding gene and its expression in Escherichia coli.

Psychrotrophic lipolytic bacteria represent a significant problem in the storage of refrigerated dairy products. A lipase-encoding gene has been cloned and characterized from a highly lipolytic strain of Pseudomonas. The nucleotide sequence of the gene predicts a polypeptide of M(r) 49,905, which was identified when the gene was expressed in Escherichia coli.     

Degradation of triglycerides by a pseudomonad isolated from milk: molecular analysis of a lipase-encoding gene and its expression in Escherichia coli.

Psychrotrophic lipolytic bacteria represent a significant problem in the storage of refrigerated dairy products. A lipase-encoding gene has been cloned and characterized from a highly lipolytic strain of Pseudomonas. The nucleotide sequence of the gene predicts a polypeptide of M(r) 49,905, which was identified when the gene was expressed in Escherichia coli.     

Production of the siderophore aerobactin by a halophilic pseudomonad.

A bacterial strain, isolated from a cyanobacterial culture, was identified as Pseudomonas sp. strain X40. Under iron-limiting conditions, the Pseudomonas sp. produced aerobactin, a dihydroxamate siderophore previously found only in the family Enterobacteriaceae. Aerobactin was identified by electrophoretic mobility, spectrophotometric titration, proton nuclear magnetic resonance spectroscopy, mass spectrometry, acid hydrolysis, and biological activity. Aerobactin was used as a siderophore in the Pseudomonas sp. and Escherichia coli. Two iron-repressed outer membrane proteins were observed in the Pseudomonas sp., neither of which had electrophoretic mobility identical to that of the aerobactin outer membrane receptor protein from E. coli. DNA hybridization assays showed no hybridization to the aerobactin genes from the E. coli plasmid pColV, indicating that the genetic determinants for aerobactin production by Pseudomonas strain X40 differ substantially from those found in the archetypic enteric plasmid pColV-K30.     

Production of the siderophore aerobactin by a halophilic pseudomonad.

A bacterial strain, isolated from a cyanobacterial culture, was identified as Pseudomonas sp. strain X40. Under iron-limiting conditions, the Pseudomonas sp. produced aerobactin, a dihydroxamate siderophore previously found only in the family Enterobacteriaceae. Aerobactin was identified by electrophoretic mobility, spectrophotometric titration, proton nuclear magnetic resonance spectroscopy, mass spectrometry, acid hydrolysis, and biological activity. Aerobactin was used as a siderophore in the Pseudomonas sp. and Escherichia coli. Two iron-repressed outer membrane proteins were observed in the Pseudomonas sp., neither of which had electrophoretic mobility identical to that of the aerobactin outer membrane receptor protein from E. coli. DNA hybridization assays showed no hybridization to the aerobactin genes from the E. coli plasmid pColV, indicating that the genetic determinants for aerobactin production by Pseudomonas strain X40 differ substantially from those found in the archetypic enteric plasmid pColV-K30.     

Planktonic-cell yield of a pseudomonad biofilm

Biofilm cells differ phenotypically from their free-floating counterparts. Differential growth rates in biofilms are often referred to, particularly in response to limited diffusion of oxygen and nutrients. We observed growth rates of attached Pseudomonas sp. strain CT07 cells that were notably higher than the maximum specific growth rate measured in batch culture. Despite dilution rates in continuous flow cells that exceeded the maximum planktonic specific growth rate by 58 times, sampling of the effluent revealed >10(9) cells ml(-1), suggesting that biofilms function as a source of planktonic cells through high cell yield and detachment. Further investigation demonstrated considerable planktonic cell yield from biofilms as young as 6 h, indicating that detachment is not limited to established biofilms. These biofilm-detached cells were more sensitive to a commercial biocide than associated biofilm- and chemostat-cultivated populations, implying that detached biofilm cells exhibit a character that is distinct from that of attached and planktonic cell populations.