High Salinity Alters the Germination Behavior of Bacillus subtilis Spores with Nutrient and Nonnutrient Germinants

Nagler, Katja; Setlow, Peter; Li, Yongqing; Moeller, Ralf

doi:10.1128/aem.03293-13

Cited by 61 publications

(66 citation statements)

References 46 publications

(78 reference statements)

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“…Phasecontrast microscopy further revealed that at 0.6 to 2.4 M NaCl, while the vast majority of decoated spores were able to exit the phase-bright (i.e., dormant) state, many turned only phase gray instead of phase dark (data not shown). As reported previously (23), the latter finding might indicate the successful initiation of germination but inhibition of the completion of germination. In the presence of 3.6 M NaCl, most decoated spores remained phase bright, although some phase-gray spores were also present.…”

Section: Resultssupporting

confidence: 57%

“…6A and B). As for nutrient-dependent germination, the extent of NaCl inhibition increased with increasing NaCl concentrations (23). Importantly, even at up to 3.6 M NaCl, noticeable germination could be induced by 150 MPa and significant amounts of DPA (ca.…”

Section: Resultsmentioning

confidence: 96%

“…It has previously been shown that germination with exogenous Ca 2ϩ -DPA, which is GR independent, is also inhibited by NaCl (23). Because Ca 2ϩ -DPA triggers germination via CLEs (17) that are localized in the outer spore layers (38,39), it was hypothesized that they might be one of the targets of NaCl inhibition (23). Since either cwlJ or sleB needs to be present and functional for complete germination (14), in vivo inhibition of the individual enzymes was tested with single mutants of either gene.…”

Section: Resultsmentioning

confidence: 99%

“…Previous studies showed that high salinity is detrimental to B. subtilis spore germination (22)(23)(24). Increasing NaCl concentrations delay germination initiation and increase its heterogeneity, slow down the germination process, and decrease its overall efficiency (23).…”

mentioning

confidence: 99%

“…Increasing NaCl concentrations delay germination initiation and increase its heterogeneity, slow down the germination process, and decrease its overall efficiency (23). Germination might be negatively affected by high salt concentrations at several stages (23). These include (i) GR accessibility, (ii) germinant binding to the GRs, (iii) signal processing within and signal transduction from the germinosome, leading to (iv) ion and Ca 2ϩ -DPA release with concomitant water influx, and (v) cortex hydrolysis by CLEs.…”

mentioning

confidence: 99%

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Involvement of Coat Proteins in Bacillus subtilis Spore Germination in High-Salinity Environments

Nagler

Setlow

Reineke

et al. 2015

Appl Environ Microbiol

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The germination of spore-forming bacteria in high-salinity environments is of applied interest for food microbiology and soil ecology. It has previously been shown that high salt concentrations detrimentally affect Bacillus subtilis spore germination, rendering this process slower and less efficient. The mechanistic details of these salt effects, however, remained obscure. Since initiation of nutrient germination first requires germinant passage through the spores' protective integuments, the aim of this study was to elucidate the role of the proteinaceous spore coat in germination in high-salinity environments. Spores lacking major layers of the coat due to chemical decoating or mutation germinated much worse in the presence of NaCl than untreated wild-type spores at comparable salinities. However, the absence of the crust, the absence of some individual nonmorphogenetic proteins, and the absence of either CwlJ or SleB had no or little effect on germination in high-salinity environments. Although the germination of spores lacking GerP (which is assumed to facilitate germinant flow through the coat) was generally less efficient than the germination of wild-type spores, the presence of up to 2.4 M NaCl enhanced the germination of these mutant spores. Interestingly, nutrient-independent germination by high pressure was also inhibited by NaCl. Taken together, these results suggest that (i) the coat has a protective function during germination in high-salinity environments; (ii) germination inhibition by NaCl is probably not exerted at the level of cortex hydrolysis, germinant accessibility, or germinant-receptor binding; and (iii) the most likely germination processes to be inhibited by NaCl are ion, Ca 2؉ -dipicolinic acid, and water fluxes.T he soil bacterium Bacillus subtilis possesses a broad range of different stress responses, as it is frequently confronted with changing conditions in its natural habitat (1). Upon nutrient depletion, B. subtilis forms endospores that are dormant and highly resistant to harsh environmental conditions (reviewed in references 2 and 3). The resistance properties of the spore strongly depend on its structure and composition: the dehydrated spore interior (the core) is surrounded by a relatively impermeable inner membrane, a germ cell wall, and protective integuments, i.e., the spore cortex and coat (2-4). The cortex is composed of modified peptidoglycan and is an important factor for establishing the low core water content required for wet heat resistance (5). In developing spores, the cortex is separated from the coat by an outer membrane, but its fate and integrity in mature spores are unclear (4). The coat is an elaborate structure composed of more than 70 different proteins that are synthesized by the sporulating mother cell, and it plays a major role in protecting spores from chemicals and exogenous enzymes (2, 4, 6). It consists of at least four layers (the basement layer, inner coat, outer coat, and crust), whose presence depends on specific morphogenetic proteins (SpoIVA, ...

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Section: Resultssupporting

confidence: 57%

Section: Resultsmentioning

confidence: 96%