Taxonomy of the Lactobacillus acidophilus Group

Abstract

A total of 89 strains designated Lactobtrcillus acidophilus were examined for physiological properties, type of lactic acid produced, cell wall sugar pattern, guanine plus cytosine content of deoxyribonucleic acid (DNA), and DNA homology values compared with selected reference strains. Immunological reactions among a group of the strains were determined by gel diffusion tests, using antiserum to purified lactic acid dehydrogenase (LDH) from a single strain (Sharpe strain AM). Antiserum to glyceraldehyde-3-phosphate dehydrogenase from strain ATCC 4356 was used in microcomplement fixation tests to determine relationships among some strains. DNA preparations from 78 of the 89 strains of L. acidophilus were distributed among six distinct homology groups, designated A l , A2, A3, A4, B1, and B2. The A group strains had 20 to 30% intergroup homology but very low homology to groups B1 and B2. Likewise, the strains in the two B groups had 20 to 30% intergroup homology but very low homology to the A group strains. Nine strains did not fall into any of the six homology groups.The guanine plus cytosine contents of the DNAs in strains comprising the six homology groups varied from 32 to 38 mol%. In the nine strains not falling into any of the homology groups, the guanine plus cytosine contents were 39 to 47 mol% Homology group Al, which includes the neotype strain of L. acidophilus (ATCC 4356), is very homogeneous, with most strains showing 95% or more homology to the reference strain. This group corresponds to LDH serogroup 111. Strains in the other homology groups showed 60 to 90% homology to their reference strains. Strains of LDH serogroup I1 were found in homology groups A2, A3, and A4, and those in LDH serogroup I were in homology groups B1 and B2. In general, the glyceraldehyde-3-phosphate dehydrogenase serology results correlated well with the LDH results. Other phenotypic test results were similar for all of the DNA homology groups. It is recommended that homology group A1 be designated L. acidophilus and that strain ATCC 4356 remain the neotype strain.In 1900, Moro isolated from infant feces grampositive, asporogenous rods, which he named Bacillus acidophilus (26). In 1929, this species was included by Holland in the genus Lactobacillus (16). The original strain of Moro was probably lost (13), and its description, according to present day standards, is very incomplete. Moreover, investigators tended to identify all new Lactobacillus isolates from mouths and from intestinal and vaginal floras as strains of Lactobacillus acidophilus. It was only in 1970 that Hansen and Mocquot adequately described this species and designated a neotype strain for it (ATCC 4356) according to the recommendations of the International Subcommittee on the Taxonomy of Lactobacilli and Closely Related Organisms (13, 14). The description of L. acidophilus by Hansen and Mocquot was derived from the important taxonomic work of Rogosa and Sharpe (29) The guanine plus cytosine (G+C) content of the deoxyribonucleic acid (DNA) of several strains ...

Reclassification of Treponema hyodysenteriae and Treponema innocens in a New Genus, Serpula gen. nov., as Serpula hyodysenteriae comb. nov. and Serpula innocens comb. nov.

“…Miao et al reported a DNA-DNA relative reassociation value of 28% between strains B7gT and B256T (35). In both the work of Miao et al and our work the DNA homology values were below the accepted range (60 t o 100%) for strains belonging to the same species (12,20) but indicated that these species should be assigned to the same genus. Protein electrophoresis results were correlated with DNA-DNA reassociation results, as has been found for other bacteria (12,17).…”

“…DNA was extracted from bacterial cells (2 to 3 g, wet weight) by using the techniques of Marmur (33), except that proteinase K (total weight, 2 mg) was added after cell lysis by lysozyme-SDS and cell lysates were incubated for 3 to 4 h at 37°C to ensure protein degradation. The abilities of DNAs from various organisms to hybridize with one another were determined by John L. Johnson (Department of Anaerobic Microbiology, Virginia Polytechnic Institute and State University), who used the S1 nuclease method (19,20).…”

Identification and Classification of Lactobacillus Acidophilus, L. Gasseri and L. Johnsonii Strains by SDS-PAGE and rRNA-Targeted Oligonucleotide Probe Hybridization

“…Despite considerable industrial and medical interest, the systematics of this species remained confusing for a long time (Moro, 1900;OrlaJensen et al, 1936;Hansen & Mocquot, 1970), and a considerable serological heterogeneity has been shown (Sharpe, 1970;Gasser, 1970). The heterogeneity was also reflected by the results of DNA : DNA hybridization studies (Johnson et al, 1980;Lauer et al, 1980). L. acidophilus and L. gasseri are found in similar habitats and cannot be distinguished by simple phenotypic criteria (Kandler & Weiss, 1986 L. acidophilus DNA similarity groups A4 and B2, respectively (Fujisawa et al, 1992).…”

Structural and Functional Differences in Two Cyclic Bacteriocins with the Same Sequences Produced by Lactobacilli

“…This group of bacteria, including L. gasseri, which is found in the human intestine, has been classified on the basis of similarities in rRNA sequences and compositions of the cell walls into six subgroups (9,11,18). Many strains in this group have been shown to be bacteriocin producers (6,12,19,23).…”