Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA, USA.
J Bacteriol. 2012 Jun;194(11):2973-86. doi: 10.1128/JB.00170-12. Epub 2012 Mar 30.
Developmental events across the prokaryotic life cycle are highly regulated at the transcriptional and posttranslational levels. Key elements of a few regulatory networks are conserved among phylogenetic groups of bacteria, although the features controlled by these conserved systems are as diverse as the organisms encoding them. In this work, we probed the role of the CtrA regulatory network, conserved throughout the Alphaproteobacteria, in the magnetotactic bacterium Magnetospirillum magneticum strain AMB-1, which possesses unique intracellular organization and compartmentalization. While we have shown that CtrA in AMB-1 is not essential for viability, it is required for motility, and its putative phosphorylation state dictates the ability of CtrA to activate the flagellar biosynthesis gene cascade. Gene expression analysis of strains expressing active and inactive CtrA alleles points to the composition of the extended CtrA regulon, including both direct and indirect targets. These results, combined with a bioinformatic study of the AMB-1 genome, enabled the prediction of an AMB-1-specific CtrA binding site. Further, phylogenetic studies comparing CtrA sequences from alphaproteobacteria in which the role of CtrA has been experimentally examined reveal an ancestral role of CtrA in the regulation of motility and suggest that its essential functions in other alphaproteobacteria were acquired subsequently.
原核生物生命周期中的发育事件在转录和翻译后水平受到高度调控。尽管这些保守系统控制的特征与编码它们的生物体一样多样化，但细菌的几个调控网络的关键要素在系统发育群中是保守的。在这项工作中，我们探讨了 CtrA 调控网络在具有独特的细胞内组织和区室化的趋磁细菌 Magnetospirillum magneticum 菌株 AMB-1 中的作用。尽管我们已经表明，AMB-1 中的 CtrA 对于生存力不是必需的，但它对于运动是必需的，其假定的磷酸化状态决定了 CtrA 激活鞭毛生物合成基因级联的能力。表达活性和非活性 CtrA 等位基因的菌株的基因表达分析表明了扩展的 CtrA 调控组的组成，包括直接和间接靶标。这些结果，结合对 AMB-1 基因组的生物信息学研究，使得能够预测 AMB-1 特异性的 CtrA 结合位点。此外，对已经通过实验检验 CtrA 作用的α变形菌中的 CtrA 序列进行的系统发育研究揭示了 CtrA 在调节运动中的古老作用，并表明其在其他α变形菌中的必需功能是随后获得的。
