The role of gerK operon in germination of Bacillus licheniformis spores

Abstract

Sporeforming bacteria are one of the main challenges in food preserva on. The consumer demand for refrigerated foods of extended durability (REPFED) increases the need for effec ve ways of reducing the threat of food borne illness stemming from sporeforming bacteria. Studying germina on receptors and their role in germina on and outgrowth of spores might uncover the Achilles heel of spores. This study is part of an ongoing project at the Norwegian School of Veterinary Science to study germina on receptors in Bacillus licheniformis. Previous work done by the same research group has demonstrated that the gerA operon in B. licheniformis is involved in L-alanine induced germina on. This thesis builds on this work and focuses on the gerK operon. In order to study the func on of the GerK receptor, a dele on mutant was made using the transformable B. licheniformis MW3 strain. B. licheniformis MW3 lacks two type I restric on modifica on enzymes present in the type strain. Two mutants were created, a single gerK dele on in B. licheniformis MW3 and a double dele on mutant, gerA and gerK, created by dele on of gerK in the gerA mutant. No involvement of gerK could be found in germina on with L-alanine, L-cysteine, L-isoleucine or casamino acid, but further studies are needed to rule out a possible coopera on between GerA and GerK receptors in rela on to germina on with L-alanine, glucose and K+. A$er crea ng the gerK dele on mutants, a set of CwlJ dele on mutants were created. CwlJ is an enzyme which is involved in depolymeriza on of cortex pep doglycan during germina on. Due to meframe restric on these were not included in the germina on study for this thesis, but will be studied by the research group.