Brito María Gabriela, López Nancy I, Raiger Iustman Laura J
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, IQUIBICEN-CONICET, 1428, Buenos Aires, Argentina.
Extremophiles. 2024 Dec 19;29(1):9. doi: 10.1007/s00792-024-01375-x.
Polyhydroxyalkanoates (PHAs) are intracellular polymers that enhance bacterial fitness against various environmental stressors. Pseudomonas extremaustralis 14-3b 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 increases P. extremaustralis fitness 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. extremaustralis was 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.
聚羟基脂肪酸酯（PHA）是一种细胞内聚合物，可增强细菌对各种环境压力的适应性。南极假单胞菌14-3b是一种南极细菌，能够积累由C3-C5单体组成的短链长度PHA（sclPHA）以及含有≥C6单体的中链长度PHA（mclPHA）。由于pH变化在细菌生理学中至关重要，会影响微生物的生长和代谢过程，我们提出积累的PHA可提高南极假单胞菌应对pH变化的适应性。为了验证这一点，我们分析了不同pH水平下sclPHA和mclPHA的产生及其对细菌在pH胁迫下存活的影响。当培养基pH值在6.0至9.5范围内时，南极假单胞菌能够生长并积累PHA，在此范围之外其活力会显著丧失。此外，基于对不同PHA缺陷突变体的分析，我们发现当暴露于酸性和碱性条件下时，sclPHA和mclPHA对pH胁迫具有不同的保护作用，其中sclPHA起主要作用。这些结果突出了PHA在支持细菌在pH胁迫环境中生存的重要性。
