Bioengineering and Drug Design Lab, Department of Biotechnology, Indian Institute of Technology (IIT) Madras, Chennai, Tamil Nadu, India.
FEMS Microbiol Lett. 2013 Jun;343(1):34-41. doi: 10.1111/1574-6968.12123. Epub 2013 Apr 2.
Acylated homoserine lactone (AHL)-based quorum sensing (QS) has been reported to be present only in Gram-negative microorganisms. Isolation of a novel Gram-positive microorganism from sea water, capable of producing AHL, is reported here. The isolate (GenBank: JF915892, designated as MPO) belonging to the Exiguobacterium genera is capable of inducing the AHL bioreporters, namely Chromobacterium violaceum CV026, Agrobacterium tumefaceins A136, and E. coli JM 109(psb1075). This inducer is characterized as C3-oxo-octanoyl homoserine lactone (OOHL), and its production reaches a maximum of 15.6 μg L(-1), during the stationary growth phase of the organism. MPO extract when exogenously added inhibits the formation of biofilm for the same organism and lowers the extracellular polymeric substances, indicating an AHL-associated phenotypic trait. The isolated sequence of a probable LuxR homolog from MPO (designated as ExgR) shows similar functional domains and contains conserved residues in LuxR from other known bacterial QS LuxR regulators. Also present immediately downstream to ExgR was found a sequence showing homology to known LuxI synthase of Pseudomonas putida. qPCR analysis suggests an increment in exgR mRNA on addition of AHL, further proving the role of ExgR as a QS regulator.
酰化高丝氨酸内酯 (AHL)- 基于群体感应 (QS) 仅在革兰氏阴性微生物中报道。本文报道了从海水中分离出一种新型革兰氏阳性微生物，能够产生 AHL。该分离物（GenBank：JF915892，命名为 MPO）属于极端杆菌属，能够诱导 AHL 生物报告菌，即紫色杆菌 CV026、根癌农杆菌 A136 和大肠杆菌 JM 109(psb1075)。这种诱导剂的特征是 C3- 氧代 - 辛酰高丝氨酸内酯 (OOHL)，其产量在生物体的静止生长阶段达到最大值 15.6 μg L(-1)。MPO 提取物在体外添加时可抑制同一生物体生物膜的形成并降低细胞外聚合物物质，表明存在与 AHL 相关的表型特征。从 MPO 中分离出的一种可能的 LuxR 同源物的序列（命名为 ExgR）显示出与其他已知细菌 QS LuxR 调节剂中的 LuxR 相似的功能结构域和保守残基。在 ExgR 下游紧接着发现了一个与假单胞菌属中的已知 LuxI 合酶同源的序列。qPCR 分析表明，在添加 AHL 时 exgR mRNA 增加，进一步证明了 ExgR 作为 QS 调节剂的作用。
