Isolation and amino acid sequence of an acid soluble protein fromClostridium perfringensspores

Bacterial spore structures and their protective role in biocide resistance

The structure and chemical composition of bacterial spores differ considerably from those of vegetative cells. These differences largely account for the unique resistance properties of the spore to environmental stresses, including disinfectants and sterilants, resulting in the emergence of spore-forming bacteria such as Clostridium difficile as major hospital pathogens. Although there has been considerable work investigating the mechanisms of action of many sporicidal biocides against Bacillus subtilis spores, there is far less information available for other species and particularly for various Clostridia. This paucity of information represents a major gap in our knowledge given the importance of Clostridia as human pathogens. This review considers the main spore structures, highlighting their relevance to spore resistance properties and detailing their chemical composition, with a particular emphasis on the differences between various spore formers. Such information will be vital for the rational design and development of novel sporicidal chemistries with enhanced activity in the future.

Investigating the role of small, acid-soluble spore proteins (SASPs) in the resistance of Clostridium perfringens spores to heat

Background

Clostridium perfringens type A food poisoning is caused by enterotoxigenic C. perfringens type A isolates that typically possess high spore heat-resistance. The molecular basis for C. perfringens spore heat-resistance remains unknown. In the current study, we investigated the role of small, acid-soluble spore proteins (SASPs) in heat-resistance of spores produced by C. perfringens food poisoning isolates.

Results

Our current study demonstrated the presence of all three SASP-encoding genes (ssp1, 2 and 3) in five surveyed C. perfringens clinical food poisoning isolates. β-Glucuronidase assay showed that these ssp genes are expressed specifically during sporulation. Consistent with these expression results, our study also demonstrated the production of SASPs by C. perfringens food poisoning isolates. When the heat sensitivities of spores produced by a ssp3 knock-out mutant of a C. perfringens food poisoning isolate was compared with that of spores of the wild-type strain, spores of the ssp3 mutant were found to exhibit a lower decimal reduction value (D value) at 100°C than exhibited by the spores of wild-type strain. This effect was restored by complementing the ssp3 mutant with a recombinant plasmid carrying wild-type ssp3, suggesting that the observed differences in D values between spores of wild-type versus ssp3 mutant was due to the specific inactivation of ssp3. Furthermore, our DNA protection assay demonstrated that C. perfringens SASPs can protect DNA from DNase I digestion.

Conclusion

The results from our current study provide evidences that SASPs produced by C. perfringens food poisoning isolates play a role in protecting their spores from heat-damage, which is highly significant and relevant from a food safety perspective. Further detailed studies on mechanism of action of SASPs from C. perfringens should help in understanding the mechanism of protection of C. perfringens spores from heat-damage.

Heat treatment adaptations in Clostridium perfringens vegetative cells

Vegetative cells of Clostridium perfringens enterotoxigenic strains NCTC 8679, NCTC 8238. and H6 were grown at 37 degrees C followed by a 60-min exposure to 28 degrees C or 46 degrees C. D10-values, as a measure of thermal resistance at 60 degrees C, were significantly lower for 28 degrees C exposures as compared with cultures given 37 and 46 degrees C exposures. Following refrigeration at 4 degrees C for 24 h, D10-values for the 37 and 46 degrees C samples could not be differentiated from 28 degrees C samples. Western immunoblot analyses of lysates from heat-adapted cells also detected the increased expression of proteins reacting with antiserum directed against the molecular chaperonins from Escherichia coli; GroEL, DnaJ, and the small acid soluble protein from Bacillus subtilis, SspC. Differential scanning calorimetry (DSC) identified thermal transitions corresponding to ribosomal protein denaturations at 72.1 +/- 0.5 degrees C. Any cellular heat adaptations in the DSC profiles were lost following refrigeration for several days to simulate minimally processed food storage conditions. Further analyses of high-speed pellets from crude cell extract fractions using two-dimensional gel electrophoresis detected the differential gene expression of at least four major proteins in heat-adapted vegetative cells of C. perfringens. N-terminal amino acid analyses identified two of the proteins as glyceraldehyde 3-phosphate dehydrogenase and rubrerythrin. Both appear to have roles in this anaerobe under stressful conditions.

Sigma factor and sporulation genes in Clostridium

The genus Clostridium, represented by Gram-positive, anaerobic, spore-forming bacteria, is well known for its clinical importance and considerable biotechnological potential. Recently, evidence for a functional role of the transcription factors sigma A, sigma E, sigma G, and sigma K in this genus was provided by cloning and sequencing these genes from C. acetobutylicum. In C. kluyveri, a partially sequenced open reading frame was found to encode the N terminus of the putative sigma factor L with significant similarity to members of the sigma 54 family. The identification of sequences with high similarity to the Bacillus sigma F (C. acetobutylicum), sigma H (several clostridial species), and sigma D (C. thermocellum)-controlled consensus promoters renders the existence of these transcription factors in clostridia very likely. These data are in agreement with information obtained by RNA transcript mapping (sigma A, sigma H), heterologous DNA hybridization (sigma D, sigma H), and immuno characterization of purified proteins (sigma A) from various clostridial species. Thus, the picture emerges that a fundamental similarity exists at the genetic level between the regulation of various cellular responses, in particular sporulation, in the genera Bacillus and Clostridium. The different induction patterns of sporulation in Bacillus spp. (nutrient starvation) and many clostridial species (cessation of growth or exposure to oxygen in the presence of excess nutrients) are most interestingly not reflected in the general regulatory features of this developmental process.

Cloning and sequencing of the genes encoding acid-soluble spore proteins from Clostridium perfringens

In Clostridium perfringens the acid-soluble spore proteins (ASSPs) of the alpha/beta type are encoded by two genes, sspC1 and sspC2. These genes, encoding ASSP C1 and C2 proteins, respectively, were cloned as parts of 3.5-kb genomic fragments. The genes were sequenced and polypeptides of 59 (C1) and 60 (C2) amino acids (aa) were deduced from the nucleotide sequence. The N-terminal Met is removed from the primary translation products in both cases, yielding mature polypeptides with Mrs of 6306 (C1) and 6553 (C2). The aa sequences of the two polypeptides were very similar and showed a closer relationship with C. bifermentans ASSPs than with ASSPs from Bacillus species.