STRAIN CHARACTERIZATION, GENOME SIZE AND PLASMID CONTENT IN THE LACTOBACILLUS-ACIDOPHILUS GROUP (HANSEN AND MOCQUOT)

Chromosomal DNA of nine strains of the Lactobacillus acidophilus (Hans en and Mocquot) group in which heterogeneity had previously been revea led by biochemical characteristics and DNA-DNA hybridization studies w ere further investigated bv restriction analysis, Southern hybridizati on, conventional and pulsed-field gel electrophoresis (PFGE) analyses. Industrial strains were characterized and identified as Lact. acidoph ilus. For this species, the number of rRNA gene clusters was estimated to be at least four from analyses of rRNA gene restriction patterns. The chromosome size of type-strains of Lact. acidophilus and Lact. gas seri was estimated from PFGE analysis to be 1.85 and 2.02 Mb respectiv ely and Lact. gasseri strains were found to contain large-sized linear plasmids.