Polyhydroxyalkanoate degradation is associated with nucleotide accumulation and enhances stress resistance and survival of Pseudomonas oleovorans in natural water microcosms.

Pseudomonas oleovorans GPo1 and its polyhydroxyalkanoic acid (PHA) depolymerization-minus mutant, GPo500 phaZ, residing in natural water microcosms, were utilized to asses the effect of PHA availability on survival and resistance to stress agents. The wild-type strain showed increased survival compared to the PHA depolymerase-minus strain. The appearance of a round cellular shape, characteristic of bacteria growing under starvation conditions, was delayed in the wild type in comparison to the mutant strain. Percent survival at the end of ethanol and heat challenges was always higher in GPo1 than in GPo500. Based on these results and on early experiments (H. Hippe, Arch. Mikrobiol. 56:248-277, 1967) that suggested an association of PHA utilization with respiration and oxidative phosphorylation, we investigated the association between PHA degradation and nucleotide accumulation. ATP and guanosine tetraphosphate (ppGpp) production was analyzed under culture conditions leading to PHA depolymerization. A rise in the ATP and ppGpp levels appeared concomitant with PHA degradation, while this phenomenon was not observed in the mutant strain unable to degrade the polymer. Complementation of the phaZ mutation restored the wild-type phenotype.

Polyhydroxyalkanoates degradation affects survival of Pseudomonas oleovorans in river water microcosms

Bacterial survival in natural environments involves the ability of scavenging nutrients and energy sources. Polyhydroxyalkanoates (PHAs) are intracellular polymers that endow bacteria with enhanced survival capabilities in adverse environmental conditions. In this paper we compared survival of Pseudomonas oleovorans wild type and PHA depolymerase mutant strains in natural river waters by using microcosms. Experiments were performed with water samples collected from the Rio de la Plata. The survival of the P. oleovorans strain capable of degrading PHA was higher in raw river water compared to the depolymerase negative mutant strain. Bacterial numbers decreased during the experiment. At the end of the experiment, the difference in the number of cells between wild type and mutant strains was of 3 orders of magnitude. Mutants deficient in PHA degradation are useful to study the importance of reserve polymers in the survival of bacterial species in natural environments. They could also provide an adequate system for the analysis of the role of PHA in the tolerance to physical or chemical stress agents.

Polyhydroxyalkanoates degradation affects survival of Pseudomonas oleovorans in river water microcosms

Bacterial survival in natural environments involves the ability of scavenging nutrients and energy sources. Polyhydroxyalkanoates (PHAs) are intracellular polymers that endow bacteria with enhanced survival capabilities in adverse environmental conditions. In this paper we compared survival of Pseudomonas oleovorans wild type and PHA depolymerase mutant strains in natural river waters by using microcosms. Experiments were performed with water samples collected from the Rio de la Plata. The survival of the P. oleovorans strain capable of degrading PHA was higher in raw river water compared to the depolymerase negative mutant strain. Bacterial numbers decreased during the experiment. At the end of the experiment, the difference in the number of cells between wild type and mutant strains was of 3 orders of magnitude. Mutants deficient in PHA degradation are useful to study the importance of reserve polymers in the survival of bacterial species in natural environments. They could also provide an adequate system for the analysis of the role of PHA in the tolerance to physical or chemical stress agents.(AU)

Evaluation of Xanthomonas campestris survival in a soil microcosm system.

Xanthomonas campestris pv. campestris is a pathogen of cruciferous plants. We studied the survival of the wild type strain and mutant derivatives which are deficient in exopolysaccharide (EPS) or in extracellular protease synthesis in soil microcosms in order to test the hypothesis that, in this environment, adherence to soil particles and scavenging of nutrients are very important strategies for bacterial survival. In sterile soil microcosms, differences in survival were only observed between the EPS producer and its mutant. In non-sterile soil experiments, survival of Prt- mutant was similar to EPS- mutant, suggesting that both characteristics have a strong influence in survival in the presence of the natural bacterial community. Bacterial decrease represented by the slope of regression lines was higher in non-sterile soil microcosms due to the influence of biotic interactions.

Polyhydroxyalkanoates degradation affects survival of Pseudomonas oleovorans in river water microcosms.

Bacterial survival in natural environments involves the ability of scavenging nutrients and energy sources. Polyhydroxyalkanoates (PHAs) are intracellular polymers that endow bacteria with enhanced survival capabilities in adverse environmental conditions. In this paper we compared survival of Pseudomonas oleovorans wild type and PHA depolymerase mutant strains in natural river waters by using microcosms. Experiments were performed with water samples collected from the Rio de la Plata. The survival of the P. oleovorans strain capable of degrading PHA was higher in raw river water compared to the depolymerase negative mutant strain. Bacterial numbers decreased during the experiment. At the end of the experiment, the difference in the number of cells between wild type and mutant strains was of 3 orders of magnitude. Mutants deficient in PHA degradation are useful to study the importance of reserve polymers in the survival of bacterial species in natural environments. They could also provide an adequate system for the analysis of the role of PHA in the tolerance to physical or chemical stress agents.

Monitoring by PCR amplification of the polyphosphate kinase gene added to natural water samples.

A fast, simple method for the detection of the Escherichia coli polyphosphate kinase (ppk) gene by means of PCR amplification is described. The method uses filters to recover cells from the samples, which makes it suitable for environmental studies. The detection of the ppk gene was achieved from samples containing 10(2) E. coli cells, either in saline solution or in river water.