Zapata Claudia, Paillavil Braulio, Chávez Renato, Álamos Pamela, Levicán Gloria
FEMS Microbiol Ecol. 2017 Mar 1;93(3). doi: 10.1093/femsec/fix001.
Bioleaching processes are used to recover metals from sulfidic ores. Biofilm formation on ores is important for bioleaching because the attached microorganisms start the leaching process by concentrating ferric ions in the extracellular matrix. It has been shown that hydrogen peroxide is spontaneously generated on the surface of ores and that it negatively influences the growth and activity of microorganisms. However, the mechanism by which bioleaching microorganisms tolerate exogenous H2O2 as an adaptive trait remains elusive. Herein, we demonstrate that the gene yhjA, encoding a predicted periplasmic cytochrome c peroxidase (CcP), is important for the response to exogenously generated oxidative stress in the iron-oxidizing acidophilic bacterium Leptospirillum sp. CF-1. Our results show that yhjA is co-transcribed with the genes encoding the peroxide-responsive transcription regulator PerR and peroxiredoxin AhpC. CcP activity, but not yhjA mRNA level, significantly increased in response to hydrogen peroxide and ferric ion exposure, suggesting a post-translational regulation. In agreement with these results, challenging planktonic cells with hydrogen peroxide significantly increased their attachment to pyrite surfaces. In summation, our results suggest that CcP is important to cope with exogenous H2O2, thus favoring the early steps of attachment to mineral substrates.
生物浸出工艺用于从硫化矿石中回收金属。矿石上生物膜的形成对生物浸出很重要，因为附着的微生物通过在细胞外基质中浓缩铁离子来启动浸出过程。研究表明，矿石表面会自发产生过氧化氢，并且它会对微生物的生长和活性产生负面影响。然而，生物浸出微生物作为一种适应性特征耐受外源过氧化氢的机制仍然不清楚。在此，我们证明编码预测的周质细胞色素c过氧化物酶（CcP）的基因yhjA，对于嗜酸氧化亚铁硫杆菌CF-1应对外源产生的氧化应激很重要。我们的结果表明，yhjA与编码过氧化物响应转录调节因子PerR和过氧化物酶AhpC的基因共同转录。过氧化氢和铁离子暴露后，CcP活性显著增加，但yhjA mRNA水平没有增加，这表明存在翻译后调控。与这些结果一致，用过氧化氢刺激浮游细胞会显著增加它们在黄铁矿表面的附着。总之，我们的结果表明CcP对于应对外源过氧化氢很重要，从而有利于附着到矿物底物的早期步骤。
