The genetic analysis of bacterial spore germination

Moir, Anne; Kemp, E. Helen; Robinson, Carl; Corfe, Bernard M.

doi:10.1111/j.1365-2672.1994.tb04353.x

Cited by 77 publications

(125 citation statements)

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“…Previous studies have suggested that spores detect nutrient germinants through specific receptors (11,13), and a group of homologous operons, typified by the B. subtilis gerA operon, has been identified as likely encoding the putative receptors (15). In this study, we showed that B. subtilis spores lacking all five gerA-like operons had a severe defect in nutrient-induced germination.…”

Section: Discussionmentioning

confidence: 49%

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Role of Ger Proteins in Nutrient and Nonnutrient Triggering of Spore Germination in Bacillus subtilis

2000

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DormantBacillus subtilis spores germinate in the presence of particular nutrients called germinants. The spores are thought to recognize germinants through receptor proteins encoded by the gerA family of operons, which includes gerA, gerB, and gerK. We sought to substantiate this putative function of the GerA family proteins by characterizing spore germination in a mutant strain that contained deletions at all known gerA-like loci. As expected, the mutant spores germinated very poorly in a variety of rich media. In contrast, they germinated like wild-type spores in a chemical germinant, a 1-1 chelate of Ca 2؉ and dipicolinic acid (DPA). These observations showed that proteins encoded by gerA family members are required for nutrient-induced germination but not for chemical-triggered germination, supporting the hypothesis that the GerA family encodes receptors for nutrient germinants. Further characterization of Ca 2؉ -DPA-induced germination showed that the effect of Ca 2؉ -DPA on spore germination was saturated at 60 mM and had a K m of 30 mM. We also found that decoating spores abolished their ability to germinate in Ca 2؉ -DPA but not in nutrient germinants, indicating that Ca 2؉ -DPA and nutrient germinants probably act through parallel arms of the germination pathway.Bacillus subtilis cells form metabolically dormant spores when starved for one or more nutrients (7). In the presence of particular nutrients, called germinants, the spores break dormancy through the process of germination and, after going through outgrowth, eventually resume vegetative growth (15). It is currently believed that spores recognize nutrient germinants through receptor proteins encoded by three loci (gerA, gerB, and gerK). This hypothesis is based on genetic studies which showed that spores containing mutations at any one of these loci fail to germinate in response to specific germinants (14,15,19). Further support for the receptor hypothesis came from the finding that dominant mutations in gerB allow spores to germinate in novel germinants (17). The gerA, gerB, and gerK loci are each tricistronic operons encoding proteins which share significant homology across the three operons (4,12,25). Two of the three proteins encoded by each operon are predicted to be membrane proteins, which is again consistent with the idea that they encode germinant receptors (4, 25). The proteins, however, have been refractory to in vitro biochemical manipulation, and thus the receptor hypothesis remains untested.Recent sequencing and genetic studies have identified members of the gerA family of operons in other endospore-forming bacteria including Bacillus cereus (3), Bacillus anthracis (9), Bacillus halodurans (23), Clostridium acetobutylicum (Genome Therapeutics Corporation), Clostridium difficile (Sanger Centre), and Clostridium pasteurianum (GenBank). However, thus far no gerA homologs have been identified in other bacterial groups. Furthermore, the B. cereus gerA operon homolog, gerI, has been implicated in inosine-induced spore germination in that ...

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Section: Discussionmentioning

confidence: 49%

“…Genetic studies with B. subtilis have implicated three homologous operons, gerA, gerB, and gerK, in germinant recognition (13,15). To better understand the role played by these operons in spore germination, we constructed a triple-mutant strain, FB72, that contained large deletions in gerA, gerB, and gerK.…”

Section: Resultsmentioning

confidence: 99%

Role of Ger Proteins in Nutrient and Nonnutrient Triggering of Spore Germination in Bacillus subtilis

2000

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“…Work by Hachisuka demonstrated that the addition of exogenous adenosine and L-alanine was required for in vivo germination of Bacillus anthracis in the rat peritoneal cavity, thus establishing nucleosides as potentially contributing to in vivo germination (5). Germination is characterized by the hydration of the core and the breakup of the endospore cortex, though the molecular mechanisms underlying these activities remain undetermined (2,9). Endospore germination results in the expulsion of Ca 2ϩ and dipicolinic acid and the initiation of metabolic activity (11).…”

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confidence: 99%

Identification and Characterization of the gerH Operon of Bacillus anthracis Endospores: a Differential Role for Purine Nucleosides in Germination

Weiner

Read²,

Hanna

2003

J Bacteriol

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confidence: 99%

“…These sensors belong to the GerA family of germinant receptors, which are best characterized in Bacillus subtilis but which have also been studied in other Bacillus spp. (2,5,15,16,18,19,29,30).Six tricistronic gerA-like chromosomal loci (gerAA, gerAB, gerAC) plus the gerX locus carried on pXO1 exist in B. anthracis; these loci encode germinant recognition proteins (6,10,11,25). The gerS operon in B. anthracis mediates germination in response to aromatic ring structures and is required for germination in the presence of cultured M (11, 12).…”

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Macrophage-Mediated Germination of Bacillus anthracis Endospores Requires the gerH Operon

Weiner

Hanna

2003

Infect Immun

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The gerHABC operon of Bacillus anthracis, encoding a gerA-like family member of germinant sensors, was shown to be required for endospore germination in the presence of macrophages and in macrophage-conditioned media. The loss of the germination phenotype in macrophage cultures of B. anthracis gerH-null endospores was restored by complementation in trans with a wild-type copy of gerH expressed under the control of its own promoter. Using endospores from both the parental strain B. anthracis Sterne and an isogenic gerH-null strain, we partially characterized germinants secreted by macrophages into the extracellular medium.Bacillus anthracis endospores can persist for long periods in soil but, upon entering a host, germinate quickly into vegetative bacilli that grow and cause disease (4). Endospores germinate inside of or proximal to phagocytes. These cells are believed to be de facto sites of germination and contribute to the establishment of B. anthracis infection, as phagocytes are the primary means of bacterial access to the body in cases of inhalation anthrax (6,8,10,20). Several recent studies examined the fate of B. anthracis endospores in macrophages (M). Guidi-Rontani et al. showed that murine alveolar phagocytes ingest endospores that then germinate and grow into vegetative bacilli but do not replicate (6). Welkos et al. observed intact endospores and recently germinated nascent bacilli within phagosomes in M that are subsequently destroyed by these immune cells (26,27,28). Work by Dixon et al. indicated that newly vegetative bacilli escape from the phagocytic vesicles of the M where they can replicate freely in the host cell cytoplasm and release themselves from the M (3). Though there are important differences among these researchers' observations of the ultimate fates of phagocytosed endospores, it is generally agreed that germinant sensors recognize and bind small-molecule germinants and initiate the germination cascade (17). These sensors belong to the GerA family of germinant receptors, which are best characterized in Bacillus subtilis but which have also been studied in other Bacillus spp. (2,5,15,16,18,19,29,30).Six tricistronic gerA-like chromosomal loci (gerAA, gerAB, gerAC) plus the gerX locus carried on pXO1 exist in B. anthracis; these loci encode germinant recognition proteins (6,10,11,25). The gerS operon in B. anthracis mediates germination in response to aromatic ring structures and is required for germination in the presence of cultured M (11, 12). The gerH operon also mediates germination in response to aromatic ring structures and germination triggered by inosine (Ino) in combination with amino acids (25). The germinants recognized by the gerX operon on pXO1 have not yet been identified, although ⌬Sterne strains lacking pXO1 do not exhibit any gross germination defects in vitro (11,12). Endospores from a gerXnull strain, identified by Guidi-Rontani et al., germinates slightly less well than do Sterne endospores in the presence of M (6, 12). One ger locus has homology to the gerL locus...

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The genetic analysis of bacterial spore germination

Cited by 77 publications

References 35 publications

Role of Ger Proteins in Nutrient and Nonnutrient Triggering of Spore Germination in Bacillus subtilis

Role of Ger Proteins in Nutrient and Nonnutrient Triggering of Spore Germination in Bacillus subtilis

Identification and Characterization of the gerH Operon of Bacillus anthracis Endospores: a Differential Role for Purine Nucleosides in Germination

Macrophage-Mediated Germination of Bacillus anthracis Endospores Requires the gerH Operon

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