Affiliation:
1. Department of Molecular Biology & Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom,1 and
2. Institut de Genetique et de Microbiologie, Universite Paris-Sud, 91405 Orsay, France2
Abstract
ABSTRACT
The
gerP1
transposon insertion mutation of
Bacillus cereus
is responsible for a defect in the germination response of spores to both
l
-alanine and inosine. The mutant is blocked at an early stage, before loss of heat resistance or release of dipicolinate, and the efficiency of colony formation on nutrient agar from spores is reduced fivefold. The protein profiles of alkaline-extracted spore coats and the spore cortex composition are unchanged in the mutant. Permeabilization of
gerP
mutant spores by coat extraction procedures removes the block in early stages of germination, although a consequence of the permeabilization procedure in both wild type and mutant is that late germination events are not complete. The complete hexacistronic operon that includes the site of insertion has been cloned and sequenced. Four small proteins encoded by the operon (GerPA, GerPD, GerPB, and GerPF) are related in sequence. A homologous operon (
yisH-yisC
) can be found in the
Bacillus subtilis
genome sequence; null mutations in
yisD
and
yisF
, constructed by integrational inactivation, result in a mutant phenotype similar to that seen in
B. cereus
, though somewhat less extreme and equally repairable by spore permeabilization. Normal rates of germination, as estimated by loss of heat resistance, are also restored to a
gerP
mutant by the introduction of a
cotE
mutation, which renders the spore coats permeable to lysozyme. The
B. subtilis
operon is expressed solely during sporulation, and is sigma K-inducible. We hypothesize that the GerP proteins are important as morphogenetic or structural components of the
Bacillus
spore, with a role in the establishment of normal spore coat structure and/or permeability, and that failure to synthesize these proteins during spore formation limits the opportunity for small hydrophilic organic molecules, like alanine or inosine, to gain access to their normal target, the germination receptor, in the spore.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
90 articles.
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