Embrapa Soja, C.P. 231, 86001-970 Londrina, PR, Brazil.
BMC Microbiol. 2012 May 30;12:84. doi: 10.1186/1471-2180-12-84.
Rhizobium tropici strain PRF 81 (= SEMIA 4080) has been used in commercial inoculants for application to common-bean crops in Brazil since 1998, due to its high efficiency in fixing nitrogen, competitiveness against indigenous rhizobial populations and capacity to adapt to stressful tropical conditions, representing a key alternative to application of N-fertilizers. The objective of our study was to obtain an overview of adaptive responses to heat stress of strain PRF 81, by analyzing differentially expressed proteins when the bacterium is grown at 28°C and 35°C.
Two-dimensional gel electrophoresis (2DE) revealed up-regulation of fifty-nine spots that were identified by MALDI-TOF/TOF-TOF. Differentially expressed proteins were associated with the functional COG categories of metabolism, cellular processes and signaling, information storage and processing. Among the up-regulated proteins, we found some related to conserved heat responses, such as molecular chaperones DnaK and GroEL, and other related proteins, such as translation factors EF-Tu, EF-G, EF-Ts and IF2. Interestingly, several oxidative stress-responsive proteins were also up-regulated, and these results reveal the diversity of adaptation mechanisms presented by this thermotolerant strain, suggesting a cross-talk between heat and oxidative stresses.
Our data provide valuable protein-expression information relevant to the ongoing genome sequencing of strain PRF 81, and contributes to our still-poor knowledge of the molecular determinants of the thermotolerance exhibited by R. tropici species.
自 1998 年以来，根瘤菌热带菌株 PRF81（=SEMIA4080）已被用于巴西普通豆科作物的商业接种剂，因为它具有高效固氮、与土著根瘤菌种群竞争和适应热带胁迫条件的能力，是应用氮肥的关键替代品。我们研究的目的是通过分析细菌在 28°C 和 35°C 下生长时差异表达的蛋白质，来获得对热应激适应反应的概述。
二维凝胶电泳（2-DE）显示了 59 个上调斑点，通过 MALDI-TOF/TOF-TOF 进行了鉴定。差异表达的蛋白质与代谢、细胞过程和信号转导、信息存储和处理的功能 COG 类别相关。在上调的蛋白质中，我们发现了一些与保守的热反应相关的蛋白质，如分子伴侣 DnaK 和 GroEL，以及其他相关蛋白质，如翻译因子 EF-Tu、EF-G、EF-Ts 和 IF2。有趣的是，一些氧化应激响应蛋白也被上调，这些结果揭示了这种耐热菌株呈现的适应机制的多样性，表明热应激和氧化应激之间存在交叉对话。
我们的数据提供了与正在进行的 PRF81 菌株基因组测序相关的有价值的蛋白质表达信息，并有助于我们对热带根瘤菌属表现出的耐热性的分子决定因素的了解仍然有限。
