« Previous AbstractA Comparison of Different Tissues Identifies the Main Precursors of Volatile Substances in Chicken Meat    Next Abstract[Characteristics of Ozone and Source Apportionment of the Precursor VOCs in Tianjin Suburbs in Summer] »

Mol Microbiol

Title:		ComX is a unique link between multiple quorum sensing outputs and competence in Streptococcus pneumoniae
Author(s):		Luo P; Li H; Morrison DA;
Address:		"Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607, USA"
Journal Title:		Mol Microbiol
Year:		2003
Volume:		50
Issue:		2
Page Number:		623 - 633
DOI:		10.1046/j.1365-2958.2003.03714.x
ISSN/ISBN:		0950-382X (Print) 0950-382X (Linking)
Abstract:		"Natural competence for genetic transformation in Streptococcus pneumoniae is achieved directly by specific proteins that are involved in DNA uptake and chromosomal recombination, and is regulated indirectly by a quorum-sensing system encoded by two loci, comAB and comCDE. The alternative sigma factor, ComX, is thought to be the unique link between quorum sensing and competence-specific genes. To test this hypothesis, we replaced the quorum-sensing inducible promoter (PQ) of the comX gene with either a constitutive promoter (PC) or a raffinose-inducible promoter (PR), so that comX transcription would be independent of quorum sensing. Surprisingly, both competence and expression of late genes, such as ssbB, cglA or celB, were found to depend on CSP in these mutants. An unknown, CSP-dependent regulator was needed when comX was expressed from these ectopic promoters, and it appears to act post-transcriptionally. However, when a multicopy nisin-inducible ComX-overexpressing plasmid was introduced, pneumococcal cells developed competence in the presence of nisin even despite deletion of comE. At 1% of the normal protein peak level, ComX protein stimulated competence without the participation of the pheromone response circuit. Thus, ComX is a unique link to competence-specific genes, but depends on multiple outputs of quorum sensing for maximal expression"
Keywords:		"Bacterial Proteins/*physiology Plasmids/genetics Promoter Regions, Genetic Regulatory Sequences, Nucleic Acid Streptococcus pneumoniae/enzymology/*genetics Transcription Factors/*physiology *Transformation, Genetic;"
Notes:		"MedlineLuo, Ping Li, Haiying Morrison, Donald A eng Research Support, U.S. Gov't, Non-P.H.S. England 2003/11/18 Mol Microbiol. 2003 Oct; 50(2):623-33. doi: 10.1046/j.1365-2958.2003.03714.x"