Signal Transduction in Staphylococci and Other Gram-Positive Cocci
There is every reason to think that signal transduction is as frequent and important a regulatory mechanism in Gram-positive cocci (GPC) as it is in other more intensively analyzed bacteria such as Escherichia coli and Bacillus subtilis.
- PDF / 2,403,992 Bytes
- 16 Pages / 504.567 x 720 pts Page_size
- 119 Downloads / 156 Views
SIGNAL TRANSDUCTION IN STAPHYLOCOCCI AND OTHER
GRAM-PosiTIVE Cocci Richard P. Novick 1. INTRODUCTION
T
here is every reason to think that signal transduction is as frequent and important a regulatory mechanism in Gram-positive cocci (GPC) as it is in other more intensively analyzed bacteria such as Escherichia coli and Bacillus subtilis. To date, only a few signal transduction systems have been identified in GPC and in only one of these has the entire pathway been clearly delineated. These systems are agr, a global regulator of virulence in staphylococci, bla, the induction system for staphylococcal ~-lactamase, 1 - 3 VanA, the induction system for vancomycin (Vn) resistance in enterococci, 4 and the biosynthetic pathways for the lanthioninecontaining bacteriocins such as nisin, subtilin and epidermin, produced by Lactobacillus lactis, B. subtilis and Staphylococcus epidermidis, respectively.1 In addition, Bayles et al5 have identified a number of putative signal transduction systems in staphylococci by probing for conserved sequences corresponding to the well-known motifs characteristic of the classical signal transduction proteins. One of the putative histidine phosphokinase (HPK) genes thus identified has been insertionally inactivated, resulting in gross clumping of the bacteria in culture and a tight compact colonial morphology. Other genes identified by this screen encode products resembling transport proteins, suggesting that signal transduction may be involved in certain transport pathways (Bayles K, personal communication). Several streptococcal virulence factor genes are transcriptionally upregulated by the mrylvirR gene, which resembles the response regulators; however, no HPK component has been identified to date. Signal Transduction and Bacterial Virulence, edited by Rino Rappuoli,
Vincenzo Scarlato and Beatrice Arico.© 1995 R.G. Landes Company.
Signal Transduction and Bacterial Virulence
744
Finally, the plasmid-determined conjugation systems of the enterococci respond to small peptides (pheromones) produced by potential recipient organisms. These pheromones are taken up by the peptide permease system and interact with intracellular proteins to activate the conjugation system. Thus, these systems might be more accurately considered as involving signal transport rather than signal transduction. Nevertheless, it seems appropriate to include them since they represent an important response to an external signal and, moreover, may play a role in virulence. It is axiomatic that in bacteria signal transduction systems regulate genes that are involved in accessory functions, i.e., are not required for the basic processes of cell
growth and multiplication. Nevertheless, it is remarkable that most of the known signal transduction systems in Gram-positive cocci are carried by mobile genetic elements such as plasmids and transposons (see Table 9.1), which means their presence is variable among strains of a particular species and implies that they have been imported from other species where they may have
Data Loading...
