Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “SPORES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14Linked to original sources
PubMed2006

Spores of Bacillus subtilis: their resistance to and killing by radiation, heat and chemicals.

A number of mechanisms are responsible for the resistance of spores of Bacillus species to heat, radiation and chemicals and for spore killing by these agents. Spore resistance to wet heat is determined largely by the water content of spore core, which is much lower than that in the growing cell protoplast. A lower core water content generally gives more wet heat-resistant spores. The level and type of spore core mineral ions and the intrinsic stability of total spore proteins also play a role in spore wet heat resistance, and the saturation of spore DNA with alpha/beta-type small, acid-soluble spore proteins (SASP) protects DNA against wet heat damage. However, how wet heat kills spores is not clear, although it is not through DNA damage. The alpha/beta-type SASP are also important in spore resistance to dry heat, as is DNA repair in spore outgrowth, as Bacillus subtilis spores are killed by dry heat via DNA damage. Both UV and gamma-radiation also kill spores via DNA damage. The mechanism of spore resistance to gamma-radiation is not well understood, although the alpha/beta-type SASP are not involved. In contrast, spore UV resistance is due largely to an alteration in spore DNA photochemistry caused by the binding of alpha/beta-type SASP to the DNA, and to a lesser extent to the photosensitizing action of the spore core's large pool of dipicolinic acid. UV irradiation of spores at 254 nm does not generate the cyclobutane dimers (CPDs) and (6-4)-photoproducts (64PPs) formed between adjacent pyrimidines in growing cells, but rather a thymidyl-thymidine adduct termed spore photoproduct (SP). While SP is formed in spores with approximately the same quantum efficiency as that for generation of CPDs and 64PPs in growing cells, SP is repaired rapidly and efficiently in spore outgrowth by a number of repair systems, at least one of which is specific for SP. Some chemicals (e.g. nitrous acid, formaldehyde) again kill spores by DNA damage, while others, in particular oxidizing agents, appear to damage the spore's inner membrane so that this membrane ruptures upon spore germination and outgrowth. There are also other agents such as glutaraldehyde for which the mechanism of spore killing is unclear. Factors important in spore chemical resistance vary with the chemical, but include: (i) the spore coat proteins that likely react with and detoxify chemical agents; (ii) the relative impermeability of the spore's inner membrane that restricts access of exogenous chemicals to the spore core; (iii) the protection of spore DNA by its saturation with alpha/beta-type SASP; and (iv) DNA repair for agents that kill spores via DNA damage. Given the importance of the killing of spores of Bacillus species in the food and medical products industry, a deeper understanding of the mechanisms of spore resistance and killing may lead to improved methods for spore destruction.

Bacillus subtilis↗
PubMed2003

Germination of spores of Bacillus subtilis with dodecylamine.

AIMS: To determine the properties of Bacillus subtilis spores germinated with the alkylamine dodecylamine, and the mechanism of dodecylamine-induced spore germination. METHODS AND RESULTS: Spores of B. subtilis prepared in liquid medium were germinated efficiently by dodecylamine, while spores prepared on solid medium germinated more poorly with this agent. Dodecylamine germination of spores was accompanied by release of almost all spore dipicolinic acid (DPA), degradation of the spore's peptidoglycan cortex, release of the spore's pool of free adenine nucleotides and the killing of the spores. The dodecylamine-germinated spores did not initiate metabolism, did not degrade their pool of small, acid-soluble spore proteins efficiently and had a significantly lower level of core water than did spores germinated by nutrients. As measured by DPA release, dodecylamine readily induced germination of B. subtilis spores that: (a) were decoated, (b) lacked all the receptors for nutrient germinants, (c) lacked both the lytic enzymes either of which is essential for cortex degradation, or (d) had a cortex that could not be attacked by the spore's cortex-lytic enzymes. The DNA in dodecylamine-germinated wild-type spores was readily stained, while the DNA in dodecylamine-germinated spores of strains that were incapable of spore cortex degradation was not. These latter germinated spores also did not release their pool of free adenine nucleotides. CONCLUSIONS: These results indicate that: (a) the spore preparation method is very important in determining the rate of spore germination with dodecylamine, (b) wild-type spores germinated by dodecylamine progress only part way through the germination process, (c) dodecylamine may trigger spore germination by a novel mechanism involving the activation of neither the spore's nutrient germinant receptors nor the cortex-lytic enzymes, and (d) dodecylamine may trigger spore germination by directly or indirectly activating release of DPA from the spore core, through the opening of channels for DPA in the spore's inner membrane. SIGNIFICANCE AND IMPACT OF THE STUDY: These results provide new insight into the mechanism of spore germination with the cationic surfactant dodecylamine, and also into the mechanism of spore germination in general. New knowledge of mechanisms to stimulate spore germination may have applied utility, as germinated spores are much more sensitive to processing treatments than are dormant spores.

Adenine Nucleotides↗
PubMed2004

Analysis of the action of compounds that inhibit the germination of spores of Bacillus species.

AIMS: To determine the mechanism of action of inhibitors of the germination of spores of Bacillus species, and where these inhibitors act in the germination process. METHODS AND RESULTS: Spores of various Bacillus species are significant agents of food spoilage and food-borne disease, and inhibition of spore germination is a potential means of reducing such problems. Germination of the following spores was studied: (i) wild-type B. subtilis spores; (ii) B. subtilis spores with a nutrient receptor variant allowing recognition of a novel germinant; (iii) B. subtilis spores with elevated levels of either the variant nutrient receptor or its wild-type allele; (iv) B. subtilis spores lacking all nutrient receptors and (v) wild-type B. megaterium spores. Spores were germinated with a variety of nutrient germinants, Ca2+-dipicolinic acid (DPA) and dodecylamine for B. subtilis spores, and KBr for B. megaterium spores. Compounds tested as inhibitors of germination included alkyl alcohols, a phenol derivative, a fatty acid, ion channel blockers, enzyme inhibitors and several other compounds. Assays used to assess rates of spore germination monitored: (i) the fall in optical density at 600 nm of spore suspensions; (ii) the release of the dormant spore's large depot of DPA; (iii) hydrolysis of the dormant spore's peptidoglycan cortex and (iv) generation of CFU from spores that lacked all nutrient receptors. The results with B. subtilis spores allowed the assignment of inhibitory compounds into two general groups: (i) those that inhibited the action of, or response to, one nutrient receptor and (ii) those that blocked the action of, or response to, several or all of the nutrient receptors. Some of the compounds in groups 1 and 2 also blocked action of at least one cortex lytic enzyme, however, this does not appear to be the primary site of their action in inhibiting spore germination. The inhibitors had rather different effects on germination of B. subtilis spores with nutrients or non-nutrients, consistent with previous work indicating that germination of B. subtilis spores by non-nutrients does not involve the spore's nutrient receptors. In particular, none of the compounds tested inhibited spore germination with dodecylamine, and only three compounds inhibited Ca2+-DPA germination. In contrast, all compounds had very similar effects on the germination of B. megaterium spores with either glucose or KBr. The effects of the inhibitors tested on spores of both Bacillus species were largely reversible. CONCLUSIONS: This work indicates that inhibitors of B. subtilis spore germination fall into two classes: (i) compounds (most alkyl alcohols, N-ethylmaleimide, nifedipine, phenols, potassium sorbate) that inhibit the action of, or response to, primarily one nutrient receptor and (ii) compounds [amiloride, HgCl2, octanoic acid, octanol, phenylmethylsulphonylfluoride (PMSF), quinine, tetracaine, tosyl-l-arginine methyl ester, trifluoperazine] that inhibit the action of, or response to, several nutrient receptors. Action of these inhibitors, is reversible. The similar effects of inhibitors on B. megaterium spore germination by glucose or KBr indicate that inorganic salts likely trigger germination by activating one or more nutrient receptors. The lack of effect of all inhibitors on dodecylamine germination suggests that this compound stimulates germination by creating channels in the spore's inner membrane allowing DPA release. SIGNIFICANCE AND IMPACT OF THE STUDY: This work provides new insight into the steps in spore germination that are inhibited by various chemicals, and the mechanism of action of these inhibitors. The work also provides new insights into the process of spore germination itself.

Anti-Bacterial Agents↗
PubMed2003

Mechanisms of killing of Bacillus subtilis spores by hypochlorite and chlorine dioxide.

AIMS: To determine the mechanisms of Bacillus subtilis spore killing by hypochlorite and chlorine dioxide, and its resistance against them. METHODS AND RESULTS: Spores of B. subtilis treated with hypochlorite or chlorine dioxide did not accumulate damage to their DNA, as spores with or without the two major DNA protective alpha/beta-type small, acid soluble spore proteins exhibited similar sensitivity to these chemicals; these agents also did not cause spore mutagenesis and their efficacy in spore killing was not increased by the absence of a major DNA repair pathway. Spore killing by these two chemicals was greatly increased if spores were first chemically decoated or if spores carried a mutation in a gene encoding a protein essential for assembly of many spore coat proteins. Spores prepared at a higher temperature were also much more resistant to these agents. Neither hypochlorite nor chlorine dioxide treatment caused release of the spore core's large depot of dipicolinic acid (DPA), but hypochlorite- and chlorine dioxide-treated spores much more readily released DPA upon a subsequent normally sub-lethal heat treatment than did untreated spores. Hypochlorite-killed spores could not initiate the germination process with either nutrients or a 1 : 1 chelate of Ca2+-DPA, and these spores could not be recovered by lysozyme treatment. Chlorine dioxide-treated spores also did not germinate with Ca2+-DPA and could not be recovered by lysozyme treatment, but did germinate with nutrients. However, while germinated chlorine dioxide-killed spores released DPA and degraded their peptidoglycan cortex, they did not initiate metabolism and many of these germinated spores were dead as determined by a viability stain that discriminates live cells from dead ones on the basis of their permeability properties. CONCLUSIONS: Hypochlorite and chlorine dioxide do not kill B. subtilis spores by DNA damage, and a major factor in spore resistance to these agents appears to be the spore coat. Spore killing by hypochlorite appears to render spores defective in germination, possibly because of severe damage to the spore's inner membrane. While chlorine dioxide-killed spores can undergo the initial steps in spore germination, these germinated spores can go no further in this process probably because of some type of membrane damage. SIGNIFICANCE AND IMPACT OF THE STUDY: These results provide information on the mechanisms of the killing of bacterial spores by hypochlorite and chlorine dioxide.

Bacillus subtilis↗
PubMed2006

Mechanisms of killing of spores of Bacillus subtilis by dimethyldioxirane.

AIMS: To determine the mechanisms of Bacillus subtilis spore resistance to and killing by a novel sporicide, dimethyldioxirane (DMDO) that was generated in situ from acetone and potassium peroxymonosulfate at neutral pH. METHODS AND RESULTS: Spores of B. subtilis were effectively killed by DMDO. Rates of killing by DMDO of spores lacking most DNA protective alpha/beta-type small, acid-soluble spore proteins (alpha- beta- spores) or the major DNA repair protein, RecA, were very similar to that of wild-type spore killing. Survivors of wild-type and alpha- beta- spores treated with DMDO also exhibited no increase in mutations. Spores lacking much coat protein due either to mutation or chemical decoating were much more sensitive to DMDO than were wild-type spores, but were more resistant than growing cells. Wild-type spores killed with this reagent retained their large pool of dipicolinic acid (DPA), and the survivors of spores treated with DMDO were sensitized to wet heat. The DMDO-killed spores germinated with nutrients, albeit more slowly than untreated spores, but germinated faster than untreated spores with dodecylamine. The killed spores were also germinated by very high pressures and by lysozyme treatment in hypertonic medium, but many of these spores lysed shortly after their germination, and none of these treatments were able to revive the DMDO-killed spores. CONCLUSIONS: DMDO is an effective reagent for killing B. subtilis spores. The spore coat is a major factor in spore resistance to DMDO, which does not kill spores by DNA damage or by inactivating some component needed for spore germination. Rather, this reagent appears to kill spores by damaging the spore's inner membrane in some fashion. SIGNIFICANCE AND IMPACT OF THE STUDY: This work demonstrates that DMDO is an effective decontaminant for spores of Bacillus species that can work under mild conditions, and the killed spores cannot be revived. Evidence has also been obtained on the mechanisms of spore resistance to and killing by this reagent.

Anti-Bacterial Agents↗