A unique method for studying the initiation of Bacillus megaterium spore germination

Life-cycle kinetic model for endospore-forming bacteria, including germination and sporulation

We develop a mechanistic life-cycle model for endospore-forming bacteria (EFB) and test the model with experiments with a Bacillus mixed culture. The model integrates and quantifies how sporulation and germination are triggered by depletion or presence of a limiting substrate, while both substrates affect the rate of vegetative growth by a multiplicative model. Kinetic experiments show the accumulation of small spherical spores after the triggering substrate is depleted, substantially more rapid decay during sporulation than for normal decay of vegetative cells, and a higher specific substrate utilization rate for the germinating cells than that for growth of vegetative cells. Model simulations capture all of these experimental trends. According to model predictions, when a batch reactor is started, seeding with EFB spores instead of active EFB delays the onset of rapid chemical oxygen demand (COD) utilization and biomass growth, but the end points are the same. Simulated results with low aeration intensity show that germination can consume some substrate without dissolved oxygen (DO) depletion.

Monitoring the Kinetics of Bacillus subtilis Endospore Germination via Surface-Enhanced Raman Scattering Spectroscopy

Mirror sandwich SERS substrates (M3S) were used to monitor the kinetics of Bacillus subtilis endospore germination. The sandwich configuration of the substrates allows real-time observation of germination in samples that contained only several hundred endospores. The enhancement provided by the substrates is attributed to the enhanced local electromagnetic field that originates from coupling between the Ag nanoparticles and the underlying metal film as well as from coupling between the Ag nanoparticles themselves. The germination kinetics at varying concentrations of l-alanine and different temperatures were studied by monitoring the intensity and growth of the Raman peak at 1010 cm(-1), which is characteristic of dipicolinic acid. A total of four concentrations (50, 75, 100, and 150 mM) of l-alanine and three different temperatures (30, 37, and 55 degrees C) were investigated.

Chemical germination of native and cation-exchanged bacterial spores with trifluoperazine

The calmodulin antagonist trifluoperazine and its analog chlorpromazine, both amphipaths, induced chemical germination of spores of various species, as do many surfactants. Cation load can greatly influence this response. Calmodulin antagonism does not seem to be involved. A new fluorometric assay for dipicolinic acid based on the fluorescence of the dipicolinic acid chelate of Tb3+ was found to be simple and sensitive.

Pulling the trigger: the mechanism of bacterial spore germination

In spite of displaying the most extreme dormancy and resistance properties known among living systems, bacterial endospores retain an alert environment-sensing mechanism that can respond within seconds to the presence of specific germinants. This germination response is triggered in the absence of both germinant and germinant-stimulated metabolism. Genes coding for components of the sensing mechanism in spores of Bacillus subtilis have been cloned and sequenced. However, the molecular mechanism whereby these receptors interact with germinants to initiate the germination response is unknown. Recent evidence has suggested that in spores of Bacillus megaterium KM, proteolytic activation of an autolytic enzyme constitutes part of the germination trigger reaction.

Trypsinlike enzymes from dormant and germinated spores of Bacillus cereus T and their possible involvement in germination

Trypsin-like enzymes were studied in dormant, activated, and germinated spores of Bacillus cereus T. Dormant spores contained two heat-labile enzyme activities. One was extractable with 2 M KCl and hydrolyzed azo-albumin. The second, a trypsinlike activity, was not extractable with 2 M KCl and hydrolyzed benzoyl-L-arginine-p-nitroanilide. Because of their heat instability, these two enzyme activities are probably not involved in the germination of heat-activated spores. Upon germination of heat-treated spores, a trypsinlike protease which was not detected in intact dormant spores was activated or exposed. This enzyme, when measured in intact germinated spores, hydrolyzed benzoyl-DL-arginine-p-nitroanilide but not azo-albumin and was inhibited in situ by sulfhydryl-blocking reagents such as p-chloromercuribenzoic acid and Hg2+. There was a correlation between the inhibition of germination and enzymatic activity by sulfhydryl-blocking reagents. The enzyme was also inhibited by leupeptin, tosyl-L-lysine chromoethyl ketone, and tosyl-L-arginine methyl ester. Good correlation existed between the inhibition of germination and enzymatic activity by these agents. Electron micrographs showed that in the presence of trypsin inhibitors, the spores did not lose their cortex. The protein extracts of the inhibited spores formed a somewhat different electrophoretic pattern in sodium dodecyl sulfate-polyacrylamide gel electrophoresis than the protein extracts of dormant or germinated spores.

Inhibition of cortex hydrolysis during spore germination by CdCl2

When the spores of Bacillus megaterium QM B1551 (ATCC 12872) were incubated with 5 mM CdCl2 at 30 C, they underwent the early germination events, such as loss of heat resistance and release of calcium dipicolinate, in the same way as when they were germinated by glucose + KNO3. However, germination by CdCl2 caused no increase in the reducing groups in the cortex and no excretion of glucosamine-containing materials due to the hydrolysis of the cortex peptidoglycan. Addition of CdCl2 at any time during germination by glucose + KNO3 inhibited the release of glucosamine-containing materials from the spores, whereas removal of cadmium from the CdCl2-germinated spores by treatment with cysteine restored the hydrolysis of peptidoglycan. These results suggested that CdCl2 caused the early events of spore germination but prevented the spores from undergoing the events following germination by inhibiting the enzymatic lysis of the cortex peptidoglycan. The conclusion from the study is that cortex degradation is not always required for the initiation of germination.

Effect of inhibitors of trypsin-like proteolytic enzymes Bacillus cereus T spore germination

The germination of Bacillus cereus T spore suspensions is partially prevented by several inhibitors of trypsin-like enzymes. Leupeptin, antipain, and tosyl-lysine-chloromethyl ketone are effective inhibitors, whereas chymostatin, elastatinal, and pepstatin are inactive. A synthetic substrate of trypsin, tosyl-arginine-methyl ester, also inhibits germination. Its inhibitory effect decreases as a function of incubation time in the presence of spores and is abolished by previous hydrolysis with trypsin. Germinating, but not dormant, spore suspensions hydrolyze tosyl-arginine-methyl ester; its hydrolysis is insensitive to chloramphenicol, sulfhydryl reagents, and EDTA. A crude extract of germinated B. cereus spores contains a trypsin-like enzyme whose activity, as measured by hydrolysis of benzoyl-arginine p-nitroanilide, is sensitive to germination-inhibitory compounds such as leupeptin, tosyl-arginine-methyl ester, and tosyl-lysine-chloromethyl ketone. Spore suspensions exposed to the above inhibitors under germination conditions lose only part of their heat resistance and some 10 to 30% of their dipicolinic acid content. Part of the germinating spore population becomes "phase grey" under phase optics. Based on a study of the inhibition of germination by protease inhibitors and the activity of a protease in germination spores and spore extracts, it is suggested that the activity of a trypsin-like enzyme may be involved in the mechanism of the breaking of dormancy in spores of B. cereus T.

Germination properties of a spore coat-defective mutant of Bacillus subtilis

The presence of the gerE36 mutation in strains of Bacillus subtilis 168 resulted in poor germination of their spores in a range of germinants, as measured by the fall in absorbance of spore suspensions. Although resistant to heat and organic solvents, spores were sensitive to lysozyme; electron microscopy revealed that their coat structure was incomplete. These spores responded to germinants by losing heat resistance and changing from phase bright to phase gray. The release of dipicolinic acid and the fall in absorbance of spore suspensions reached only 75 and 50% of wild-type levels, respectively, but followed the same time course as the loss of heat resistance. Although the germination response was incomplete, the concentration of L-alanine required to elicit it was the same for the mutant as for the wild type. The properties of mutant spores suggest that an intact spore coat is not required for the initial interaction between germinant and spore, but that the coat layers may contain molecules important in later stages of germination. In transduction with phage SPP1, the gerE36 mutation mapped between citF and ilvB and was 90% cotransduced with citF2. The gerE mutation identifies the location of a gene important for the progress of late stages of spore formation.

Biochemistry of L-proline-triggered germination of Bacillus megaterium spores

The mechanism by which L-proline triggers germination in Bacillus megaterium QM B1551 spores was investigated. First, brief exposure of spores to L-proline, followed by dilution, was sufficient to trigger germination. Once germination was triggered, the spores continued initiation of germination and did not require high concentrations of L-proline. Triggering of germination was pH and temperature dependent. Second, enzymes for L-proline catabolism were absent in spores, and several non-metabolizable analogs of L-proline were effective trigger compounds. Third, triggering of germination occurred in the presence of inhibitors of proton motive force production, oxygen uptake, and metabolism. Fourth, uptake of L-proline occurred after the triggering of germination. These results argue that neither uptake nor metabolism of L-proline was necessary to trigger germination. Instead, L-proline probably causes a biophysical alteration in the spores that triggers the biochemical changes in germination.

Glucose-triggered germination of Bacillus megaterium spores

Triggering of germination in Bacillus megaterium QM B1551 spores with D-glucose was studied. First, the interaction of glucose with spores for less than 1 min resulted in triggering almost 90% of the spores after the glucose was removed by dilution. Therefore only a brief time is needed for glucose to trigger germination, and then the continuous presence of glucose is not necessary. Detectable uptake of glucose began 2 to 3 min after absorbance loss started, and a non-metabolizable glucose analog, methyl-alpha-D-glucopyranoside, triggered germination in the absence of detectable uptake. Several inhibitors that reduced or eliminated glucose uptake did not block triggering of germination. Therefore, glucose uptake may be a relatively late event and not a prerequisite for triggering of germination.

An evaluation of respiration chain-associated functions during initiation of germination of Bacillus megaterium spores

In Bacillus megaterium QM B1551, spore germination could be initiated by glucose in the absence of detectable oxygen consumption, ATP synthesis or a pH decrease in the external media, suggesting that none of those reactions were mandatory. In addition, initiation of germination was insensitive to a variety of inhibitors of energy production or protonmotive force uncouplers. Therefore the respiratory chain-associated functions are not prerequisites for initiation of germination but these functions may be necessary to drive energy-dependent transport systems and other biosynthetic reactions during outgrowth.