Transcription of quorum-sensing system genes in clinical and environmental isolates of Pseudomonas aeruginosa
Transcription of quorum-sensing system genes in clinical and environmental isolates of Pseudomonas aeruginosa
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DOI：
10.1128/jb.185.24.7222-7230.2003
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发表时间：
2003-12-01
影响因子：
3.2
通讯作者：
Ruimy, R
中科院分区：
文献类型：
--
作者：
Cabrol, SN;Olliver, A;Ruimy, R
铜绿假单胞菌中基于群体感应（Quorum sensing， QS）的转录反应被定义为：随着lasR基因等中心控制基因的分层转录增加，lasB和aprA等QS控制基因的转录水平也随之增加。这些增加发生在高细菌浓度下，如体外生长的早期静止阶段。然而，在各种临床和环境分离株中增加的程度尚未确定，也没有关于lasR基因等位基因变异的广泛信息。对66株临床分离株和环境分离株的lasR基因序列分析表明，81%的序列与菌株PAO1相同或有沉默突变，15%的序列发生核苷酸变化导致氨基酸变化，5%的序列在lasR基因中有插入序列。利用实时荧光定量PCR对35株从菌血症、肺炎病例和环境中分离出来的菌株进行测定，我们发现大多数（35株中的33株）菌株在固定期早期lasR、lasB和aprA转录物水平增加，但每个细胞的最终转录物水平范围很广。在所有菌株中，早期对数期转录物水平与早期平稳期转录物水平之间存在很强的相关性（r(2) = 0.84），但这一发现仅适用于50%高于早期对数期lasR中位数水平的菌株。lasR转录物水平与aprA （r(2) = 0.2）和lasB （r(2) = 0.5）转录物水平有显著（P < 0.05）但弱至中度相关性，但这种相关性同样只出现在50%的铜绿假单胞菌中，lasR转录物水平在固定期早期最高。在菌血症、肺炎和环境分离株中lasR等位基因的分布没有差异。总的来说，只有大约50%的临床和环境来源的铜绿假单胞菌菌株显示出lasr依赖性的aprA和lasB基因转录增加，这表明对于大约50%的临床分离株，该调控系统可能在发病机制中不起重要作用。
Quorum sensing (QS)-based transcriptional responses in Pseudomonas aeruginosa have been defined on the basis of increases in transcript levels of QS-controlled genes such as lasB and aprA following the hierarchical transcriptional increases of central controllers such as the lasR gene. These increases occur at high bacterial concentrations such as early-stationary-phase growth in vitro. However, the extent to which the increases occur in a variety of clinical and environmental isolates has not been determined nor is there extensive information on allelic variation in lasR genes. An analysis of the sequences of the lasR gene among 66 clinical and environmental isolates showed that 81% have a sequence either identical to that of strain PAO1 or with a silent mutation, 15% have nucleotide changes resulting in amino acid changes, and 5% have an insertion sequence in the lasR gene. Using real-time PCR to quantify transcript levels of lasR, lasB, and aprA in the early log and early stationary phases among 35 isolates from bacteremia and pneumonia cases and the environment, we found most (33 of 35) strains had increases in lasR transcripts in early stationary phase but with a very wide range of final transcript levels per cell. There was a strong correlation (r(2) = 0.84) between early-log- and early-stationary-phase transcript levels in all strains, but this finding remained true only for the 50% of strains above the median level of lasR found in early log phase. There were significant (P < 0.05) but weak-to-modest correlations of lasR transcript levels with aprA (r(2) = 0.2) and lasB (r(2) = 0.5) transcript levels, but again this correlation occurred only in the 50% of P. aeruginosa strains with the highest levels of lasR transcripts in early stationary phase. There were no differences in distribution of lasR alleles among the bacteremia, pneumonia, or environmental isolates. Overall, only about 50% of P. aeruginosa strains from clinical and environmental sources show a lasR-dependent increase in the transcription of aprA and lasB genes, indicating that for about 50% of clinical isolates this regulatory system may not play a significant role in pathogenesis.