Detection of different quorum-sensing signal molecules in a virulent Edwardsiella tarda strain LTB-4.
OBJECTIVE
The aim of this study was to elucidate the potential quorum-sensing (QS) signal molecules of an emerging pathogen (Edwardsiella tarda strain LTB-4) of cultured turbot (Scophthalmus maximus).


RESULTS
A sensitive and rapid double-layer plate method using biosensor strain Agrobacterium tumefaciens KYC55 was developed to detect the N-acylhomoserine lactone (AHL)-related compounds in bacteria. LTB-4 was found to have two QS systems, one was based on the AHLs and the other was based on the autoinducer-2 (AI-2). The AI-2 activity produced by LTB-4 was growth phase dependent and topped at OD(600) of 1.0. The protocol to detect cholerae autoinducer 1 (CAI-1) activity in bacteria was modified, lowering the background luminescence of biosensor strain Vibrio harveyi JAF375. CAI-1 activity could not be detected in LTB-4.


CONCLUSIONS
Edwardsiella tarda LTB-4 produced at least four kinds of AHLs during its whole growth phase. In comparison with the AHL-inducing QS, AI-2 may be the first predominant signal, functioning at early exponential phase. LTB-4 did not produce any CAI-1 activity.


CONCLUSIONS
Different QS signal molecules of Edw. tarda LTB-4 were clarified by improved bioassays. In contrast to earlier studies detecting two types of AHLs, strain LTB-4 produced at least four kinds of AHLs, which seemed to be C(4)-HSL, C(6)-HSL, 3-oxo-C(6)-HSL and an uncharacterized AHL molecule.
Han
Y
Y
Department of Marine Biology, Ocean University of China, Yushan, Qingdao, China.
Li
X
X
Qi
Z
Z
Zhang
X-H
XH
Bossier
P
P
D016960:Agrobacterium tumefaciens / Q000378:metabolism*; D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D020609:Edwardsiella tarda / Q000378:metabolism* / Q000472:pathogenicity; D004756:Enterobacteriaceae Infections / Q000378:metabolism / Q000382:microbiology; D005393:Fish Diseases / Q000378:metabolism / Q000382:microbiology; D005412:Flatfishes / Q000382:microbiology; D053038:Quorum Sensing / Q000502:physiology*; D014733:Vibrio / Q000378:metabolism*