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J. Bacteriol., Dec 1997, 7315-7320, Vol 179, No. 23
ML Gwinn, AE Stellwagen, NL Craig, JF Tomb and HO Smith
Haemophilus influenzae Rd is a gram-negative bacterium capable of natural
DNA transformation. The competent state occurs naturally in late
exponential growth or can be induced by a nutritional downshift or by
transient anaerobiosis. The genes cya, crp, topA, and sxy (tfoX) are known
to function in the regulation of competence development. The
phosphoenolpyruvate:carbohydrate phosphotransferase system functions to
maintain levels of cyclic AMP necessary for competence development but is
not directly involved in regulation. The exact signal(s) for competence and
the genes that mediate the signal(s) are still unknown. In an effort to
find additional regulatory genes, H. influenzae Rd was mutated by using an
in vitro Tn7 system and screened for mutants with a reduced ability to
induce the competence-regulatory gene, comA. Insertions in atpA, a gene
coding for the alpha subunit of the F1 cytoplasmic domain of the ATP
synthase, reduce transformation frequencies about 20-fold and cause a
significant reduction in expression of competence-regulatory genes, while
the expression of constitutive competence genes is only minimally affected.
In addition, we found that an insertion in atpB, which encodes the a
subunit of the F0 membrane-spanning domain, has a similar effect on
transformation frequencies.
Copyright © 1997, American Society for Microbiology
In vitro Tn7 mutagenesis of Haemophilus influenzae Rd and characterization of the role of atpA in transformation
Department of Molecular Biology and Genetics, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA. mlgwinn@tigr.org
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