Competence development by Haemophilus influenzae is regulated by the availability of nucleic acid precursors

Citation
Lp. Macfadyen et al., Competence development by Haemophilus influenzae is regulated by the availability of nucleic acid precursors, MOL MICROB, 40(3), 2001, pp. 700-707
Citations number
35
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
MOLECULAR MICROBIOLOGY
ISSN journal
0950-382X → ACNP
Volume
40
Issue
3
Year of publication
2001
Pages
700 - 707
Database
ISI
SICI code
0950-382X(200105)40:3<700:CDBHII>2.0.ZU;2-9
Abstract
DNA uptake by naturally competent bacteria provides cells with both genetic information and nucleotides. In Haemophilus influenzae, competence develop ment requires both cAMP and an unidentified signal arising under starvation conditions. To investigate this signal, competence induction was examined in media supplemented with nucleic acid precursors. The addition of physiol ogical levels of AMP and GMP reduced competence 200-fold and prevented the normal competence-induced transcription of the essential competence genes c omA and rec-2. The rich medium normally used for growth allows only limited competence. Capillary electrophoresis revealed only a subinhibitory amount of AMP and no detectable GMP, and the addition of AMP or GMP to this mediu m also reduced competence 20- to 100-fold. Neither a functional stringent r esponse system nor a functional phosphoenolpyruvate:glycose phosphotransfer ase system (PTS) was found to be required for purine-mediated repression. A dded cAMP partially restored both transcription of competence genes and com petence development, suggesting that purines may reduce the response to cAM P. Potential binding sites for the PurR repressor were identified in severa l competence genes, suggesting that competence is part of the PUR regulon. These observations are consistent with models of competence regulation, in which depleted purine pools signal the need for nucleotides, and support th e hypothesis that competence evolved primarily for nucleotide acquisition.