Competence development by Haemophilus influenzae is regulated by the availability of nucleic acid precursors
Competence development by Haemophilus influenzae is regulated by the availability of nucleic acid precursors
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DOI：
10.1046/j.1365-2958.2001.02419.x
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发表时间：
2001-05-01
影响因子：
3.6
通讯作者：
Redfield, RJ
中科院分区：
文献类型：
--
作者：
Macfadyen, LP;Chen, D;Redfield, RJ
天然细菌对DNA的摄取为细胞提供遗传信息和核苷酸。在流感嗜血杆菌中，能力发展既需要cAMP，也需要饥饿条件下产生的未知信号。为了研究这一信号，在添加了核酸前体的培养基中进行了能力诱导试验。生理水平的AMP和GMP的加入使能力降低了200倍，并阻止了基本能力基因comA和rec-2的正常能力诱导转录。通常用于生长的富培养基只允许有限的能力。毛细管电泳显示AMP的亚抑制量，没有检测到GMP，并且在该培养基中添加AMP或GMP也使能力降低了20至100倍。发现嘌呤介导的抑制既不需要功能性严格反应系统，也不需要功能性磷酸烯醇丙酮酸：糖苷磷酸转移酶系统（PTS）。添加cAMP可以部分恢复能力基因的转录和能力发展，这表明嘌呤可能会降低对cAMP的反应。在几个能力基因中发现了PurR抑制因子的潜在结合位点，这表明能力是PUR调控的一部分。这些观察结果与能力调节模型一致，即嘌呤池的耗尽表明需要核苷酸，并支持能力进化主要是为了核苷酸获取的假设。
DNA uptake by naturally competent bacteria provides cells with both genetic information and nucleotides. In Haemophilus influenzae, competence development requires both cAMP and an unidentified signal arising under starvation conditions. To investigate this signal, competence induction was examined in media supplemented with nucleic acid precursors. The addition of physiological levels of AMP and GMP reduced competence 200-fold and prevented the normal competence-induced transcription of the essential competence genes comA and rec-2. The rich medium normally used for growth allows only limited competence. Capillary electrophoresis revealed only a subinhibitory amount of AMP and no detectable GMP, and the addition of AMP or GMP to this medium also reduced competence 20- to 100-fold. Neither a functional stringent response system nor a functional phosphoenolpyruvate:glycose phosphotransferase system (PTS) was found to be required for purine-mediated repression. Added cAMP partially restored both transcription of competence genes and competence development, suggesting that purines may reduce the response to cAMP. Potential binding sites for the PurR repressor were identified in several competence genes, suggesting that competence is part of the PUR regulon. These observations are consistent with models of competence regulation, in which depleted purine pools signal the need for nucleotides, and support the hypothesis that competence evolved primarily for nucleotide acquisition.