Núñez Cinthia, Esteve-Núñez Abraham, Giometti Carol, Tollaksen Sandra, Khare Tripti, Lin Winston, Lovley Derek R, Methé Barbara A
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa Cuernavaca, Morelos 62210, Mexico.
J Bacteriol. 2006 Apr;188(8):2792-800. doi: 10.1128/JB.188.8.2792-2800.2006.
The regulon of the sigma factor RpoS was defined in Geobacter sulfurreducens by using a combination of DNA microarray expression profiles and proteomics. An rpoS mutant was examined under steady-state conditions with acetate as an electron donor and fumarate as an electron acceptor and with additional transcriptional profiling using Fe(III) as an electron acceptor. Expression analysis revealed that RpoS acts as both a positive and negative regulator. Many of the RpoS-dependent genes determined play roles in energy metabolism, including the tricarboxylic acid cycle, signal transduction, transport, protein synthesis and degradation, and amino acid metabolism and transport. As expected, RpoS activated genes involved in oxidative stress resistance and adaptation to nutrient limitation. Transcription of the cytochrome c oxidase operon, necessary for G. sulfurreducens growth using oxygen as an electron acceptor, and expression of at least 13 c-type cytochromes, including one previously shown to participate in Fe(III) reduction (MacA), were RpoS dependent. Analysis of a subset of the rpoS mutant proteome indicated that 15 major protein species showed reproducible differences in abundance relative to those of the wild-type strain. Protein identification using mass spectrometry indicated that the expression of seven of these proteins correlated with the microarray data. Collectively, these results indicate that RpoS exerts global effects on G. sulfurreducens physiology and that RpoS is vital to G. sulfurreducens survival under conditions typically encountered in its native subsurface environments.
通过结合DNA微阵列表达谱和蛋白质组学，确定了嗜硫还原地杆菌中σ因子RpoS的调控子。在以乙酸盐作为电子供体、富马酸盐作为电子受体的稳态条件下，以及使用Fe(III)作为电子受体进行额外转录谱分析的情况下，对rpoS突变体进行了检测。表达分析表明，RpoS既作为正调控因子又作为负调控因子发挥作用。许多已确定的依赖RpoS的基因在能量代谢中发挥作用，包括三羧酸循环、信号转导、转运、蛋白质合成与降解以及氨基酸代谢与转运。正如预期的那样，RpoS激活了参与抗氧化应激和适应营养限制的基因。嗜硫还原地杆菌以氧气作为电子受体生长所必需的细胞色素c氧化酶操纵子的转录，以及至少13种c型细胞色素的表达，包括一种先前已证明参与Fe(III)还原的细胞色素（MacA），均依赖于RpoS。对rpoS突变体蛋白质组的一个子集进行分析表明，相对于野生型菌株，15种主要蛋白质在丰度上表现出可重复的差异。使用质谱进行蛋白质鉴定表明，其中7种蛋白质的表达与微阵列数据相关。总体而言，这些结果表明RpoS对嗜硫还原地杆菌的生理功能具有全局影响，并且RpoS对于嗜硫还原地杆菌在其原生地下环境中通常遇到的条件下的生存至关重要。
