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

doi:10.1186/1471-2180-12-34

BMC Microbiol. 2012; 12: 34.

Published online 2012 March 15. doi: 10.1186/1471-2180-12-34

PMCID: PMC3359204

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

Irene S Løvdal,^1,^2,⁴ Cecilie From,² Elisabeth H Madslien,^2,³ Kristin Cecilia S Romundset,² Elin Klufterud,^2,⁵ Jan Thomas Rosnes,¹ and Per Einar Granum²

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

²Departement 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

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

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

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

Corresponding author.

Irene S Løvdal: irene.s.lovdal/at/uis.no; Cecilie From: Cecilie.From/at/nvh.no; Elisabeth H Madslien: Elisabeth-Henie.Madslien/at/ffi.no; Kristin Cecilia S Romundset: Kristin.Romundset/at/nvh.no; Elin Klufterud: elin.klufterud/at/mills.no; Jan Thomas Rosnes: thomas.rosnes/at/nofima.no; Per Einar Granum: pereinar.granum/at/nvh.no

Received December 22, 2011; Accepted March 15, 2012.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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.

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