Similarities and Differences in Quorum Sensing-Controlled Bioluminescence between Photobacterium phosphoreum T3 and Vibrio qinghaiensis sp.-Q67

Dan Wang,Wei Yan,Shanshan Li,Linming Bai

doi:10.3390/app12042066

Abstract

Quorum sensing is a density-dependent mechanism using chemical signal molecules termed autoinducers to regulate diverse biological processes in bacteria, including bioluminescence. However, the correlation between growth and light emission of two typical luminescent bacteria, Photobacterium phosphoreum T3 and Vibrio qinghaiensis sp.-Q67, is still unclear. This study investigates the variations of bioluminescence and the light-emission-involved gene expression of the above two strains, respectively, showing that bioluminescence is population density-dependent. Furthermore, the effect of crude extracts (175, 350, 700 and 1750 mg/L) from the bacterial culture that contains the potential autoinducers on the bioluminescence is explored. At the exponential and the early stationary growth phase, T3 did not exhibit an obvious light intensity and cell density change after adding crude extracts at 175 and 350 mg/L, while the light intensity decreased at 700 and 1750 mg/L, showing a luminescence inhibition. For Q67, the light intensity increased dramatically with crude extract concentration. These results suggest that the bioluminescence process of both T3 and Q67 is controlled by quorum sensing. Furthermore, the different response modes of these two strains to autoinducers imply that the two strains could be applied to different compounds for toxicity assesses.

Highlights

Quorum sensing (QS) is a microbial cell–cell communication process that depends on the secretion of diffusible chemical molecular-termed autoinducers to regulate associated gene expression in response to cell density [1,2]
The luminescent bacteria Photobacterium phosphoreum T3 and Vibrio qinghaiensis sp.-Q67 were purchased from China General Microbiological Culture Collection Center (Beijing, China) and Beijing Hamamatsu Corp., Ltd. (Beijing, China), respectively
The Genes Associated with Luminescence in P. phosphoreum and V. qinghaiensis

Summary

Introduction

Quorum sensing (QS) is a microbial cell–cell communication process that depends on the secretion of diffusible chemical molecular-termed autoinducers to regulate associated gene expression in response to cell density [1,2]. When the accumulated autoinducers (in and out of the cell) gradually reach a significant threshold concentration the expression of related genes will be induced, leading to various microbial behaviors, including bioluminescence production and virulence secretion, biofilm formation and so on [3]. Various studies have demonstrated that acyl-homoserine lactone (AHL) is one of the most important autoinducers that mediates the QS-dependent gene expression in Gram-negative bacteria [4,5]. A second QS system named AinS/AinR was reported in

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