The trigger mechanism of spore germination: current concepts

Johnstone, Keith

doi:10.1111/j.1365-2672.1994.tb04354.x

Cited by 55 publications

(44 citation statements)

References 61 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…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: 48%

See 1 more Smart Citation

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

2000

View full text Add to dashboard Cite

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 ...

show abstract

Section: Discussionmentioning

confidence: 48%

“…downstream from the germinant receptors (8,11) could be responsible for the infrequent germination events. These two possibilities could be distinguished by examining the occurrence of the infrequent germination events in water, because stochastic activation events would be expected to take place even in distilled water.…”

Section: Discussionmentioning

confidence: 99%

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

2000

View full text Add to dashboard Cite

show abstract

“…Previous work suggested that germinants act by binding to and activating spore receptors (9,13,19). This idea has been substantiated by several types of experiments which suggest that a family of homologous operons (the gerA family, which includes gerA, gerB, and gerK) encode the predicted receptors.…”

mentioning

confidence: 74%

Localization of a Germinant Receptor Protein (GerBA) to the Inner Membrane of Bacillus subtilis Spores

2001

View full text Add to dashboard Cite

DormantBacillus subtilis spores germinate in response to specific nutrients called germinants, which are recognized by multisubunit receptor complexes encoded by members of the gerA family of operons, of which the gerB operon is a member. The germinant receptors are expected to be membrane associated, but there is some debate about whether they are located in the inner or outer spore membrane. In this study we have used Western blot analysis to determine the precise location of GerBA, a gerB-encoded receptor protein, in various spore fractions. GerBA was not extracted from spores by a decoating treatment that removes the coat and outer membrane but was present in lysates from decoated spores and in the insoluble fraction (termed P100) from such lysates that contained inner-membrane vesicles. GerBA was also solubilized from the P100 fraction with detergent but not with high salt. These findings suggest that GerBA is an integral membrane protein located in the spore's inner membrane. Consistent with this idea, GerBA was present in the cell membrane of the outgrowing spore, a membrane that is derived from the dormant spore's inner membrane. Based on these observations we propose that GerBA and probably the entire GerB germinant receptor are located in the inner membrane of the dormant spore. We also estimated that there are only 24 to 40 molecules of GerBA per spore, a number that is consistent with the previously reported low level of gerB operon expression and with the putative receptor function of the proteins encoded by the gerB operon.Dormant spores of Bacillus subtilis are metabolically inert structures that are formed when growing cells are starved for particular nutrients. Despite their dormancy, these spores can detect nutrients in the environment and respond to such cues by triggering a number of reactions that result in the resumption of metabolism and growth. The initial steps in this process, called spore germination, thus represent a novel paradigm for studying the communication between a cell and its surroundings.A variety of nutrients can induce spore germination, and in B. subtilis two such germinants have been extensively studied: L-alanine (L-Ala) and a combination of L-asparagine, D-fructose, D-glucose, and potassium ions (AFGK) (19). Previous work suggested that germinants act by binding to and activating spore receptors (9,13,19). This idea has been substantiated by several types of experiments which suggest that a family of homologous operons (the gerA family, which includes gerA, gerB, and gerK) encode the predicted receptors. First, mutations in gerA, gerB, and gerK block germination in a germinant-specific manner (17-19). Second, missense mutations in one family member, gerB, allow spores to recognize novel germinants (23). Finally, spores lacking all of the gerA family members show a severe defect in nutrient-induced germination (24). At the DNA sequence level, each gerA family member is a tricistronic operon that encodes three predicted proteins named A, B, and C, and there is evidence t...

show abstract

“…Nutrient-induced germination can be initiated by small molecules called germinants, which are somehow able to activate putative germination receptors located in the inner membrane (11,24), probably by an allosteric interaction with the receptor (38). After this initial interaction, the spore becomes committed to germination (16). Subsequent processes in germination are the release of metal ions from the spore core and the excretion of spore-specific molecules such as dipicolinic acid (DPA) (19,26,33).…”

mentioning

confidence: 99%

Characterization of Germination Receptors of Bacillus cereus ATCC 14579

Hornstra

Vries

Wells-Bennik

et al. 2006

Appl Environ Microbiol

View full text Add to dashboard Cite

Specific amino acids, purine ribonucleosides, or a combination of the two is required for efficient germination of endospores of Bacillus cereus ATCC 14579. A survey including 20 different amino acids showed that L-alanine, L-cysteine, L-threonine, and L-glutamine are capable of initiating the germination of endospores of B. cereus ATCC 14579. In addition, the purine ribonucleosides inosine and adenosine can trigger germination of the spores. Advanced annotation of the B. cereus ATCC 14579 genome revealed the presence of seven putative germination (ger) operons, termed gerG, gerI, gerK, gerL, gerQ, gerR, and gerS. To determine the role of the encoded putative receptors in nutrient-induced germination, disruption mutants were constructed by the insertion of pMUTIN4 into each of the seven operons. Four of the seven mutants were affected in the germination response to amino acids or purine ribonucleosides, whereas no phenotype could be attributed to the mutants with disrupted gerK, gerL, and gerS loci. The strain with a disrupted gerR operon was severely hampered in the ability to germinate: germination occurred in response to L-glutamine but not in the presence of any of the other amino acids tested. The gerG mutant showed significantly reduced L-glutamine-induced germination, which points to a role of this receptor in the L-glutamine germination signaling pathway. gerR, gerI, and gerQ mutants showed reduced germination rates in the presence of inosine, suggesting a role for these operons in ribonucleoside signaling. Efficient germination by the combination of L-glutamine and inosine was shown to involve the gerG and gerI operons, since the germination of mutants lacking either one of these receptors was significantly reduced. Germination triggered by the combination of L-phenylalanine and inosine was lost in the gerI mutant, indicating that both molecules are effective at the GerI receptor.

show abstract

The trigger mechanism of spore germination: current concepts

Cited by 55 publications

References 61 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

Localization of a Germinant Receptor Protein (GerBA) to the Inner Membrane of Bacillus subtilis Spores

Characterization of Germination Receptors of Bacillus cereus ATCC 14579

Contact Info

Product

Resources

About