Lupp Claudia, Ruby Edward G
Pacific Biomedical Research Center, University of Hawaii at Manoa, Honolulu, USA.
J Bacteriol. 2005 Jun;187(11):3620-9. doi: 10.1128/JB.187.11.3620-3629.2005.
Vibrio fischeri possesses two quorum-sensing systems, ain and lux, using acyl homoserine lactones as signaling molecules. We have demonstrated previously that the ain system activates luminescence gene expression at lower cell densities than those required for lux system activation and that both systems are essential for persistent colonization of the squid host, Euprymna scolopes. Here, we asked whether the relative contributions of the two systems are also important at different colonization stages. Inactivation of ain, but not lux, quorum-sensing genes delayed initiation of the symbiotic relationship. In addition, our data suggest that lux quorum sensing is not fully active in the early stages of colonization, implying that this system is not required until later in the symbiosis. The V. fischeri luxI mutant does not express detectable light levels in symbiosis yet initiates colonization as well as the wild type, suggesting that ain quorum sensing regulates colonization factors other than luminescence. We used a recently developed V. fischeri microarray to identify genes that are controlled by ain quorum sensing and could be responsible for the initiation defect. We found 30 differentially regulated genes, including the repression of a number of motility genes. Consistent with these data, ain quorum-sensing mutants displayed an altered motility behavior in vitro. Taken together, these data suggest that the sequential activation of these two quorum-sensing systems with increasing cell density allows the specific regulation of early colonization factors (e.g., motility) by ain quorum sensing, whereas late colonization factors (e.g., luminescence) are preferentially regulated by lux quorum sensing.
费氏弧菌拥有两个群体感应系统，即ain和lux，它们使用酰基高丝氨酸内酯作为信号分子。我们之前已经证明，ain系统在比lux系统激活所需细胞密度更低时就能激活发光基因表达，并且这两个系统对于鱿鱼宿主——夏威夷短尾乌贼的持续定殖都是必不可少的。在此，我们探究了这两个系统的相对作用在不同定殖阶段是否也很重要。ain群体感应基因（而非lux群体感应基因）的失活延迟了共生关系的起始。此外，我们的数据表明lux群体感应在定殖早期并未完全激活，这意味着该系统在共生后期才是必需的。费氏弧菌luxI突变体在共生过程中不表达可检测到的光水平，但定殖起始情况与野生型一样，这表明ain群体感应调控的是发光以外的定殖因子。我们使用最近开发的费氏弧菌微阵列来鉴定受ain群体感应控制且可能导致起始缺陷的基因。我们发现了30个差异调节基因，包括一些运动性基因的抑制。与这些数据一致，ain群体感应突变体在体外表现出改变的运动行为。综上所述，这些数据表明，随着细胞密度增加，这两个群体感应系统的顺序激活使得ain群体感应能够特异性调节早期定殖因子（如运动性），而后期定殖因子（如发光）则优先由lux群体感应调节。
