Clostridium gasigenes sp. nov., a psychrophile causing spoilage of vacuum-packed meat.

Two psychrophilic Clostridium strains, DB1AT and R26, were isolated from incidences of 'blown-pack' spoilage of vacuum-packed chilled lamb. Vacuum packs of meat inoculated with these strains developed gas bubbles and pack distension within 14 d storage at 2 degrees C. The two main gases responsible for pack distension were carbon dioxide and hydrogen. 1-Butanol, butyric and acetic acid and butyl esters were the major volatile compounds produced by the strains in the artificially inoculated packs. The unknown strains were Gram-positive motile rods producing elliptical subterminal spores during the late-stationary growth phase. At pH 7.0, they grew from -1.5 to 26 degrees C, and their optimum growth temperature was 20-22 degrees C. At 20 degrees C, the pH range for growth was 5.4-8.9 and the optimum pH for growth was 6.2-8.6. In peptone/yeast extract broth, the organisms grew little or not at all in the absence of fermentable carbohydrates. Both strains hydrolysed gelatin, aesculin and starch. The fermentation products formed in peptone yeast extract glucose starch broth were ethanol, acetate, butyrate, lactate, butanol, carbon dioxide and hydrogen. The G+C contents of the DNA of strains DB1AT and R26 were 29.4 and 28.3 mol%, respectively. Phylogenetic analyses indicated that the strains belong to cluster I of the genus Clostridium (sensu Collins et al. 1994). The new strains differed from the phylogenetically related clostridia in cellular fatty acid composition, soluble protein profiles and phenotypic properties. On the basis of rDNA analysis and phenotypic and phylogenetic characterization, the strains were assigned to a new species for which the name Clostridium gasigenes is proposed. Strain DB1AT (= DSM 12272T) is designated as the type strain.