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Structural and functional analysis of the GerD spore germination protein of Bacillus species.

ABSTRACT: Spore germination in Bacillus species represents an excellent model system with which to study the molecular mechanisms underlying the nutritional control of growth and development. Binding of specific chemical nutrients to their cognate receptors located in the spore inner membrane triggers the germination process that leads to a resumption of metabolism in spore outgrowth. Recent studies suggest that the inner membrane GerD lipoprotein plays a critical role in the receptor-mediated activation of downstream germination events. The 121-residue core polypeptide of GerD (GerD???¹??) from Geobacillus stearothermophilus forms a stable ?-helical trimer in aqueous solution. The 2.3-Å-resolution crystal structure of the trimer reveals a neatly twisted superhelical rope, with unusual supercoiling induced by parallel triple-helix interactions. The overall geometry comprises three interleaved hydrophobic screws of interacting helices linked by short turns that have not been seen before. Using complementation analysis in a series of Bacillus subtilis gerD mutants, we demonstrated that alterations in the GerD trimer structure have profound effects on nutrient germination. This important structure-function relationship of trimeric GerD is supported by our identification of a dominant negative gerD mutation in B. subtilis. These results and those of others lead us to propose that GerD mediates clustering of germination proteins in the inner membrane of dormant spores and thus promotes the rapid and cooperative germination response to nutrients.

SUBMITTER: Li Y

PROVIDER: S-EPMC4038265 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Structural and functional analysis of the GerD spore germination protein of Bacillus species.

Li Yunfeng Y Jin Kai K Ghosh Sonali S Devarakonda Parvathimadhavi P Carlson Kristina K Davis Andrew A Stewart Kerry-Ann V KA Cammett Elizabeth E Pelczar Rossi Patricia P Setlow Barbara B Lu Min M Setlow Peter P Hao Bing B

Journal of molecular biology 20140212 9

Spore germination in Bacillus species represents an excellent model system with which to study the molecular mechanisms underlying the nutritional control of growth and development. Binding of specific chemical nutrients to their cognate receptors located in the spore inner membrane triggers the germination process that leads to a resumption of metabolism in spore outgrowth. Recent studies suggest that the inner membrane GerD lipoprotein plays a critical role in the receptor-mediated activation ...[more]

PMID: 24530795

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Project description:Bacillus and Clostridium species form spores, which pose a challenge to the food industry due to their ubiquitous nature and extreme resistance. Pressurization at <300 MPa triggers spore germination by activating germination receptors (GRs), while pressurization at >300 MPa likely triggers germination by opening dipicolinic acid (DPA) channels present in the inner membrane of the spores. In this work, we expose spores of Bacillus licheniformis, a species associated with food spoilage and occasionally with food poisoning, to high pressure (HP) for holding times of up to 2 h. By using mutant spores lacking one or several GRs, we dissect the roles of the GerA, Ynd, and GerK GRs in moderately HP (mHP; 150 MPa)-induced spore germination. We show that Ynd alone is sufficient for efficient mHP-induced spore germination. GerK also triggers germination with mHP, although at a reduced germination rate compared to that of Ynd. GerA stimulates mHP-induced germination but only in the presence of either the intact GerK or Ynd GR. These results suggests that the effectiveness of the individual GRs in mHP-induced germination differs from their effectiveness in nutrient-induced germination, where GerA plays an essential role. In contrast to Bacillus subtilis spores, treatment with very HP (vHP) of 550 MPa at 37°C did not promote effective germination of B. licheniformis spores. However, treatment with vHP in combination with elevated temperatures (60°C) gave a synergistic effect on spore germination and inactivation. Together, these results provide novel insights into how HP affects B. licheniformis spore germination and inactivation and the role of individual GRs in this process.IMPORTANCE Bacterial spores are inherently resistant to food-processing regimes, such as high-temperature short-time pasteurization, and may therefore compromise food durability and safety. The induction of spore germination facilitates subsequent inactivation by gentler processing conditions that maintain the sensory and nutritional qualities of the food. High-pressure (HP) processing is a nonthermal food-processing technology used to eliminate microbes from food. The application of this technology for spore eradication in the food industry requires a better understanding of how HP affects the spores of different bacterial species. The present study provides novel insights into how HP affects Bacillus licheniformis spores, a species associated with food spoilage and occasionally food poisoning. We describe the roles of different germination receptors in HP-induced germination and the effects of two different pressure levels on the germination and inactivation of spores. This study will potentially contribute to the effort to implement HP technology for spore inactivation in the food industry.

Dataset Information

Structural and functional analysis of the GerD spore germination protein of Bacillus species.

Publications

Structural and functional analysis of the GerD spore germination protein of Bacillus species.

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