Sugar-Phosphate Metabolism Regulates Stationary-Phase Entry and Stalk Elongation in Caulobacter crescentus
Sugar-Phosphate Metabolism Regulates Stationary-Phase Entry and Stalk Elongation in Caulobacter crescentus
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DOI：
10.1128/jb.00468-19
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发表时间：
2020-02-01
影响因子：
3.2
通讯作者：
Klein, Eric A.
中科院分区：
文献类型：
--
作者：
de Young, Kevin D.;Stankeviciute, Gabriele;Klein, Eric A.
细菌有多种适应环境扰动的机制。氧可用性的变化导致有氧和无氧呼吸之间的切换，而铁限制可能导致铁载体分泌。除了代谢适应，许多生物体还通过改变细胞形状来做出反应。新月柄杆菌，当生长在磷酸盐限制条件下，显着延长其极柄附属物。茎假设，以促进磷酸盐的吸收，然而，茎合成的机械细节没有得到很好的表征。我们使用了化学诱变的方法来分离和表征茎缺陷突变体，其中之一有两个突变的磷酸甘露糖异构酶基因（manA）是必要的，足以抑制茎伸长。在莫纳突变体中，磷酸盐调节子的转录不受影响;因此，ManA在茎合成中起着独特的调节作用。突变体ManA的酶活性降低，导致细胞内果糖6-磷酸/甘露糖6-磷酸比例增加5倍。这种代谢失衡损害了来自甘露糖6-磷酸的细胞包膜成分的合成，即脂多糖O-抗原和胞外多糖。此外，manA突变阻止了C. crescentus细胞有效进入稳定期。在野生型细胞中，稳定期反应调节基因spdR的缺失抑制了茎的伸长，而alarmone ppGpp的过量产生，这会触发生长停滞和稳定期进入，增加了莫纳突变株的茎长度。这些结果表明，糖-磷酸盐代谢调节茎伸长独立的磷酸盐starvation.IMPORTANCE代谢控制细菌细胞形状是一个重要的机制，为适应环境扰动。新月柄杆菌显着延长其极柄附属物响应磷酸盐饥饿。为了研究这种形态适应的机制，我们分离出茎缺陷突变体，其中一个突变的磷酸甘露糖异构酶基因（manA），阻止茎伸长，尽管正常激活的磷酸盐饥饿反应。突变体ManA导致糖-磷浓度失衡，影响细胞膜成分的合成和进入稳定期。由于代谢途径的相互联系，我们的研究结果可能更普遍地表明，细菌细胞形状的调节涉及生长阶段的调节和细胞结构单元的合成。
Bacteria have a variety of mechanisms for adapting to environmental perturbations. Changes in oxygen availability result in a switch between aerobic and anaerobic respiration, whereas iron limitation may lead to siderophore secretion. In addition to metabolic adaptations, many organisms respond by altering their cell shape. Caulobacter crescentus, when grown under phosphate-limiting conditions, dramatically elongates its polar stalk appendage. The stalk is hypothesized to facilitate phosphate uptake; however, the mechanistic details of stalk synthesis are not well characterized. We used a chemical mutagenesis approach to isolate and characterize stalk-deficient mutants, one of which had two mutations in the phosphomannose isomerase gene (manA) that were necessary and sufficient to inhibit stalk elongation. Transcription of the pho regulon was unaffected in the monA mutant; therefore, ManA plays a unique regulatory role in stalk synthesis. The mutant ManA had reduced enzymatic activity, resulting in a 5-fold increase in the intracellular fructose 6-phosphate/mannose 6-phosphate ratio. This metabolic imbalance impaired the synthesis of cellular envelope components derived from mannose 6-phosphate, namely, lipopolysaccharide O-antigen and exopolysaccharide. Furthermore, the manA mutations prevented C. crescentus cells from efficiently entering stationary phase. Deletion of the stationary-phase response regulator gene spdR inhibited stalk elongation in wild-type cells, while overproduction of the alarmone ppGpp, which triggers growth arrest and stationary-phase entry, increased stalk length in the monA mutant strain. These results demonstrate that sugar-phosphate metabolism regulates stalk elongation independently of phosphate starvation.IMPORTANCE Metabolic control of bacterial cell shape is an important mechanism for adapting to environmental perturbations. Caulobacter crescentus dramatically elongates its polar stalk appendage in response to phosphate starvation. To investigate the mechanism of this morphological adaptation, we isolated stalk-deficient mutants, one of which had mutations in the phosphomannose isomerase gene (manA) that blocked stalk elongation, despite normal activation of the phosphate starvation response. The mutant ManA resulted in an imbalance in sugar-phosphate concentrations, which had effects on the synthesis of cellular envelope components and entry into stationary phase. Due to the interconnectivity of metabolic pathways, our findings may suggest more generally that the modulation of bacterial cell shape involves the regulation of growth phase and the synthesis of cellular building blocks.