The marine alphaproteobacterium Phaeobacter inhibens DSM 17395, a member of the Roseobacter group, was recently shown to markedly enhance growth upon deletion of its 262-kb chromid encoding biosynthesis of tropodithietic acid (TDA). To scrutinize the metabolic/regulatory adaptations that underlie enhanced growth of the Δ262 mutant, its transcriptome and proteome compared to the wild type were investigated in process-controlled bioreactors with Casamino Acids as growth substrate. Genome resequencing revealed only few additional genetic changes (a heterogenic insertion, prophage activation, and several point mutations) between wild type and Δ262 mutant, albeit with no conceivable effect on the studied growth physiology. The abundances of the vast majority of transcripts and proteins involved in the catabolic network for complete substrate oxidation to CO₂ were found to be unchanged, suggesting that the enhanced amino acid utilization of the Δ262 mutant did not require elevated synthesis of most enzymes of the catabolic network. Similarly, constituents of genetic information processing and cellular processes remained mostly unchanged. In contrast, 426 genes displayed differential expression, of which 410 were localized on the 3.2-Mb chromosome, 5 on the 65-kb chromid, and 11 on the 78-kb chromid. Notably, the branched-chain amino transferase IlvE acting on rapidly utilized Val, Ile, and Leu was upregulated. Moreover, the transportome was reconfigured, as evidenced from increased abundances of transcripts and proteins of several uptake systems for amino acids and inorganic nutrients (e.g., phosphate). Some components of the respiratory chain were also upregulated, which correlates with the higher respiration rates of the Δ262 mutant. Furthermore, chromosomally encoded transcripts and proteins that are peripherally related to TDA biosynthesis (e.g., the serine acyl transferase CysE) were strongly downregulated in the Δ262 mutant. Taken together, these observations reflect adaptations to enhanced growth as well as the functional interconnectivity of the replicons of P. inhibens DSM 17395.
Microbial Physiol

中文翻译：

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Phaeobacter 抑制 DSM 17395 删除其 262-kb 编码抗生素合成的全局反应。

海洋α-变形菌Phaeobacter inhibens DSM 17395，所述的构件Roseobacter组，最近显示在其 262-kb chromid 编码原二硫酸 (TDA) 生物合成的缺失后显着促进生长。为了仔细检查作为 Δ262 突变体增强生长基础的代谢/调节适应性，在以酪蛋白氨基酸作为生长底物的过程控制的生物反应器中研究了与野生型相比其转录组和蛋白质组。基因组重测序仅揭示了野生型和 Δ262 突变体之间很少有额外的遗传变化（异源插入、原噬菌体激活和几个点突变），尽管对所研究的生长生理学没有可以想象的影响。参与将底物完全氧化为 CO ₂的分解代谢网络的绝大多数转录本和蛋白质的丰度发现没有变化，这表明 Δ262 突变体的氨基酸利用增强不需要分解代谢网络的大多数酶的合成增加。同样，遗传信息处理和细胞过程的成分基本保持不变。相比之下，426 个基因表现出差异表达，其中 410 个位于 3.2-Mb 染色体上，5 个位于 65-kb 染色体上，11 个位于 78-kb 染色体上。值得注意的是，作用于快速利用的 Val、Ile 和 Leu 的支链氨基转移酶 IlvE 被上调。此外，转运体被重新配置，这从氨基酸和无机营养物（例如磷酸盐）的几种摄取系统的转录物和蛋白质的丰度增加可以证明。呼吸链的一些成分也被上调，这与 Δ262 突变体的更高呼吸速率相关。此外，与 TDA 生物合成外围相关的染色体编码转录物和蛋白质（例如丝氨酸酰基转移酶 CysE）在 Δ262 突变体中被强烈下调。综上所述，这些观察结果反映了对增强生长的适应以及复制子的功能互连性。P. inhibens DSM 17395.
微生物生理学