Analysis on Actinobacillus pleuropneumoniae LuxS regulated genes reveals pleiotropic roles of LuxS/AI-2 on biofilm formation, adhesion ability and iron metabolism.

LuxS is an enzyme involved in the activated methyl cycle and the by-product autoinducer-2 (AI-2) was a quorum sensing signal in some species. In our previous study, the functional LuxS in AI-2 production was verified in the porcine respiratory pathogen Actinobacillus pleuropneumoniae. Enhanced biofilm formation and reduced virulence were observed in the luxS mutant. To comprehensively understand the luxS function, in this study, the transcriptional profiles were compared between the A. pleuropneumoniae luxS mutant and its parental strain in four different growth phases using microarray. Many genes associated with infection were differentially expressed. The biofilm formation genes pgaABC in the luxS mutant were up-regulated in early exponential phase, while 9 genes associated with adhesion were down-regulated in late exponential phase. A group of genes involved in iron acquisition and metabolism were regulated in four growth phases. Phenotypic investigations using luxS mutant and both genetic and chemical (AI-2) complementation on these virulence traits were performed. The results demonstrated that the luxS mutant showed enhanced biofilm formation and reduced adhesion ability and these effects were not due to lack of AI-2. But AI-2 could increase biofilm formation and adhesion of A. pleuropneumoniae independent of LuxS. Growth under iron restricted condition could be controlled by LuxS through AI-2 production. These results revealed pleiotropic roles of LuxS and AI-2 on A. pleuropneumoniae virulence traits.

Li L ，Xu Z ，Zhou Y ，Li T ，Sun L ，Chen H ，Zhou R ... -  《-》

Enhanced biofilm formation and reduced virulence of Actinobacillus pleuropneumoniae luxS mutant.

Li L ，Zhou R ，Li T ，Kang M ，Wan Y ，Xu Z ，Chen H ... -  《MICROBIAL PATHOGENESIS》

Autoinducer AI-2 is involved in regulating a variety of cellular processes in Salmonella Typhimurium.

Soni KA ，Jesudhasan PR ，Cepeda M ，Williams B ，Hume M ，Russell WK ，Jayaraman A ，Pillai SD ... -  《-》

luxS-based quorum-sensing signaling affects Biofilm formation in Streptococcus mutans.

Quorum sensing (QS) is a process by which bacteria communicate with diffusible chemical signaling molecules called autoinducers (AIs). The autoinducer-2 signal (AI-2) produced by the LuxS protein mediates interspecies communication among Gram-positive and Gram-negative bacteria. In this study, we report that luxS-dependent QS is involved in the formation of Streptococcus mutans biofilms. An S. mutans luxS mutant was constructed, and the differences in growth and biofilm formation were compared between the wild-type strain and the mutant strain. To quantificationally analyze the kinetic biofilm formation of the mutant strain, an assay of BioFilm Ring Test(R) was applied. There is a small increase in the growth of the luxS mutant strain after the stationary phase, compared with the parent strain. However during the exponential period, there were no significant differences. Using the BioFilm Ring Test(R), it was demonstrated that this luxS mutation was able to accelerate biofilm formation on a polystyrene surface during the mid-exponential growth phase. With 1% glucose treatment, even greater differences were observed between the mutant strain and its parental strain. These data suggest that a luxS-dependent signal may play an important role in the biofilm formation of S. mutans.

Huang Z ，Meric G ，Liu Z ，Ma R ，Tang Z ，Lejeune P ... -  《-》

The LuxS/AI-2 Quorum-Sensing System of Streptococcus pneumoniae Is Required to Cause Disease, and to Regulate Virulence- and Metabolism-Related Genes in a Rat Model of Middle Ear Infection.

Yadav MK ，Vidal JE ，Go YY ，Kim SH ，Chae SW ，Song JJ ... -  《Frontiers in Cellular and Infection Microbiology》