Nucleic Acids of Species of Lactobacillus

Nucleic acid composition of 17 cultures representing the type or neotype strains of 15 named Lactobacillus species was studied. Nucleic acid characterization of these isolates was accompanied by a comparative study of conventional phenotypic reactions. The overall guanine plus cytosine mean deoxyribonucleic acid base composition ranged from 33 to 50% and genome sizes varied between 700 and 1500 X 10(6) daltons. Sporolactobacillus inulinus contained 2500 X 10(6) daltons of chromosomal deoxyribonucleic acid and was therefore similar in size to members of the genus Bacillus. Deoxyribonucleic acid hybridization at a temperature 15 degrees C below the thermal melting temperature confirmed the extreme molecular heterogeneity of many species. The genus can be divided into three major groups, each containing four or more species based on a combination of nucleic acid characteristics and conventional phenotypic reactions. Group I (33 to 39% guanine plus cytosine) contains Lactobacillus jensenii, Lactobacillus helveticus, Lactobacillus helveticus nov. ssp. jugurt, Lactobacillus acidophilus, Lactobacillus salivarius, and Lactobacillus sanfrancisco. Group II (42 to 48% guanine plus cytosine contains Lactobacillus plantarum, Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus brevis, and Group III (48 to 50% guanine plus cytosine) contains Lactobacillus delbrueckii, Lactobacillus delbrueckii nov. ssp. bulgaricus, Lactobacillus delbrueckii nov. ssp. lactis, Lactobacillus delbrueckii nov. ssp. leichmanii, Lactobacillus fermentum, and Lactobacillus fermentum nov. ssp. cellobiosis.