Membrane Topology and Structural Insights into the Peptide Pheromone Receptor ComD, A Quorum-Sensing Histidine Protein Kinase of Streptococcus mutans

The presence of multidrug-tolerant persister cells within microbial populations has been implicated in the resiliency of bacterial survival against antibiotic treatments and is a major contributing factor in chronic infections. The mechanisms by which these phenotypic variants are formed have been linked to stress response pathways in various bacterial species, but many of these mechanisms remain unclear. We have previously shown that in the cariogenic organismStreptococcus mutans, the quorum-sensing peptide CSP (competence-stimulating peptide) pheromone was a stress-inducible alarmone that triggered an increased formation of multidrug-tolerant persisters. In this study, we characterized SMU.2027, a CSP-inducible gene encoding a LexA ortholog. We showed that in addition to exogenous CSP exposure, stressors, including heat shock, oxidative stress, and ofloxacin antibiotic, were capable of triggering expression oflexAin an autoregulatory manner akin to that of LexA-like transcriptional regulators. We demonstrated the role of LexA and its importance in regulating tolerance toward DNA damage in a noncanonical SOS mechanism. We showed its involvement and regulatory role in the formation of persisters induced by the CSP-ComDE quorum-sensing regulatory system. We further identified key genes involved in sugar and amino acid metabolism, the clustered regularly interspaced short palindromic repeat (CRISPR) system, and autolysin from transcriptomic analyses that contribute to the formation of quorum-sensing-induced persister cells.

Download Full-text

Structural Analysis of the Peptide Pheromone Receptor PlnB, a Histidine Protein Kinase from Lactobacillus plantarum

Journal of Bacteriology ◽

10.1128/jb.185.23.6913-6920.2003 ◽

2003 ◽

Vol 185 (23) ◽

pp. 6913-6920 ◽

Cited By ~ 20

Author(s):

Ola Johnsborg ◽

Dzung B. Diep ◽

Ingolf F. Nes

Keyword(s):

Protein Kinase ◽

Lactobacillus Plantarum ◽

Domain Switching ◽

Transmembrane Domain ◽

Cell Communication ◽

Threshold Concentration ◽

Membrane Topology ◽

Histidine Protein Kinase ◽

Transmembrane Segments ◽

Physiological Processes

ABSTRACT Intercellular communication plays a key role in the regulation of several physiological processes in gram-positive bacteria. Cell-cell communication is often mediated by secreted inducer peptide pheromones (IPs), which upon reaching a threshold concentration in the environment specifically activate a cognate membrane-localized histidine protein kinase (HPK). Interestingly, the majority of IP-activated HPKs fall into one distinct subfamily (HPK10). As part of an effort to study the mechanism underlying pheromone-mediated activation of the HPK10 subfamily, the present work investigated the membrane topology of PlnB from Lactobacillus plantarum. Gene fusion experiments with Escherichia coli and Lactobacillus sakei, using alkaline phosphatase, β-lactamase, and β-galactosidase reporter fusions, suggested that PlnB is anchored to the cytoplasmic membrane via seven transmembrane segments. By domain switching between HPK10 members, it was demonstrated that the determinants for pheromone binding and specificity are contained within the transmembrane domain. The results also indicate that the mechanism of signal transduction, in which the final transmembrane segment apparently plays a key role, is conserved between members of the HPK10 subfamily.

Download Full-text

Microarray Analysis of a Two-Component Regulatory System Involved in Acid Resistance and Proteolytic Activity in Lactobacillus acidophilus

Applied and Environmental Microbiology ◽

10.1128/aem.71.10.5794-5804.2005 ◽

2005 ◽

Vol 71 (10) ◽

pp. 5794-5804 ◽

Cited By ~ 90

Author(s):

M. Andrea Azcarate-Peril ◽

Olivia McAuliffe ◽

Eric Altermann ◽

Sonja Lick ◽

W. Michael Russell ◽

...

Keyword(s):

Protein Kinase ◽

Proteolytic Activity ◽

Lactobacillus Acidophilus ◽

Regulatory System ◽

Probiotic Bacterium ◽

Transport Systems ◽

Logarithmic Phase ◽

Histidine Protein Kinase ◽

Regulatory Systems ◽

Two Component

ABSTRACT Two-component regulatory systems are one primary mechanism for environmental sensing and signal transduction. Annotation of the complete genome sequence of the probiotic bacterium Lactobacillus acidophilus NCFM revealed nine two-component regulatory systems. In this study, the histidine protein kinase of a two-component regulatory system (LBA1524HPK-LBA1525RR), similar to the acid-related system lisRK from Listeria monocytogenes (P. D. Cotter et al., J. Bacteriol. 181:6840-6843, 1999), was insertionally inactivated. A whole-genome microarray containing 97.4% of the annotated genes of L. acidophilus was used to compare genome-wide patterns of transcription at various pHs between the control and the histidine protein kinase mutant. The expression pattern of approximately 80 genes was affected by the LBA1524HPK mutation. Putative LBA1525RR target loci included two oligopeptide-transport systems present in the L. acidophilus genome, other components of the proteolytic system, and a LuxS homolog, suspected of participating in synthesis of the AI-2 signaling compound. The mutant exhibited lower tolerance to acid and ethanol in logarithmic-phase cells and poor acidification rates in milk. Supplementation of milk with Casamino Acids essentially restored the acid-producing ability of the mutant, providing additional evidence for a role of this two component system in regulating proteolytic activity in L. acidophilus.

Download Full-text