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) depolyme rization-minus mutant, GPo500 phaZ, residing in natural water microcosms, w ere utilized to asses the effect of PHA availability on survival and resist ance to stress agents. The wild-type strain showed increased survival compa red to the PNA depolymerase-minus strain. The appearance of a round cellula r shape, characteristic of bacteria growing under starvation conditions, wa s delayed in the wild type in comparison to the mutant strain. Percent surv ival at the end of ethanol and heat challenges was always higher in GPo1 th an in GPo500. Based on these results and on early experiments (H. Hippe, Ar ch. Mikrobiol. 56:248-277, 1967) that suggested an association of PHA utili zation with respiration and oxidative phosphorylation, we investigated the association between PHA degradation and nucleotide accumulation ATP and gua nosine tetraphosphate (ppGpp) production was analyzed under culture conditi ons leading to PRA depolymerization. A rise in the ATP and ppGpp levels app eared concomitant with PHA degradation, while this phenomenon was not obser ved in the mutant strain unable to degrade the polymer. Complementation of the phaZ mutation restored the wild-type phenotype.