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Open Access Research article

Role of the gerA operon in L-alanine germination of Bacillus licheniformis spores

Irene S Løvdal124, Cecilie From2, Elisabeth H Madslien23, Kristin Cecilia S Romundset2, Elin Klufterud25, Jan Thomas Rosnes1 and Per Einar Granum2*

Author Affiliations

1 Nofima AS, Department of Process Technology, Måltidets hus, Richard Johnsens gate 4, P. Box 8034, N-4068 Stavanger, Norway

2 Departement of Food Safety and Infection Biology, Section for Food Safety, Norwegian School of Veterinary Science, Ullevålsveien 72, P. Box 8146 Dep., N-0033 Oslo, Norway

3 Forsvarets Forskningsinstiutt FFI, Norwegian Defence Research Establishment, P. O. Box 25, N-2027 Kjeller, Norway

4 Current address; University of Stavanger, Faculty of Arts and Education, Department of Early Childhood Education, N-4036 Stavanger, Norway

5 Current address; Mills DA, Sofienberggata 19, P. Box 4644, N-0506 Oslo, Norway

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BMC Microbiology 2012, 12:34  doi:10.1186/1471-2180-12-34

Published: 15 March 2012

Abstract

Background

The genome of Bacillus licheniformis DSM 13 harbours three neighbouring open reading frames showing protein sequence similarities to the proteins encoded from the Bacillus subtilis subsp. subtilis 168 gerA operon, GerAA, GerAB and GerAC. In B. subtilis, these proteins are assumed to form a germinant receptor involved in spore germination induced by the amino acid L-alanine.

Results

In this study we show that disruption of the gerAA gene in B. licheniformis MW3 hamper L-alanine and casein hydrolysate-triggered spore germination, measured by absorbance at 600 nm and confirmed by phase contrast microscopy. This ability was restored by complementation with a plasmid-borne copy of the gerA locus. Addition of D-alanine in the casein hydrolysate germination assay abolished germination of both B. licheniformis MW3 and the complementation mutant. Germination of both B. licheniformis MW3 and the gerA disruption mutant was induced by the non-nutrient germinant Ca2+-Dipicolinic acid.

Conclusions

These results demonstrate that the B. licheniformis MW3 gerA locus is involved in germination induced by L-alanine and potentially other components present in casein hydrolysate.