Classification of some lactic acid bacteria from vacuum-packed meats by direct probe mass spectrometry.

The technique of direct probe mass spectrometry (DPMS) has been applied to the classification of 40 strains of lactic acid bacteria from refrigerated vacuum-packed beef, pork, lamb and bacon. Relationships between strains were examined by multi-variate statistical techniques using sets of ions selected for reproducibility and sample discrimination. Five groups were distinguished which corresponded closely to those detected in a previous numerical taxonomic study. Two groups contained all 12 representatives of a cluster of unidentifiable non-aciduric streptobacteria whose sub-division is supported by other taxonomic evidence. All twenty-one strains from a cluster of aciduric streptobacteria provisionally identified with Lactobacillus sake were contained in two further groups. The sub-division of these aciduric strains revealed by DPMS has not been verified by other techniques and requires further investigation. The fifth group contained Leuconostoc strains. The study demonstrates the value of DPMS in confirming and clarifying classification schemes obtained by conventional methods.