Unraveling the effects of polyhydroxyalkanoates accumulation inPseudomonas extremaustralisgrowth and survival under different pH conditions

Abstract

AbstractPolyhydroxyalkanoates (PHAs) are intracellular polymers that enhance bacterial fitness against various environmental stressors.Pseudomonas extremaustralis14-3b is an Antarctic bacterium capable of accumulating, short-chain-length PHAs (sclPHAs), composed of C3–C5 monomers, as well as medium-chain-length PHAs (mclPHAs) containing ≥C6 monomers. Since pH changes are pivotal in bacterial physiology, influencing microbial growth and metabolic processes, we propose that accumulated PHA increasesP. extremaustralisfitness to cope with pH changes. To test this, we analyzed the production of sclPHA and mclPHA at different pH levels and its effect on bacterial survival against pH stress.P. extremaustraliswas able to grow and accumulate PHA when the culture media pH ranged from 6.0 to 9.5, showing a marked loss of viability outside this range. Additionally, based on the analysis of different PHA-deficient mutants, we found that when exposed to both acidic and alkaline conditions, sclPHA and mclPHA conferred different protection against pH stress, with sclPHA making the main contribution. These results highlight the importance of PHA in supporting survival in pH-stressful environments.