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 ...

The DNA sequence of the region located downstream from the kanamycin resistance gene of Tn5 up to the right inverted repeat IS50R has been determined. This completes the determination of the sequence of Tn5 which is 5818 bp long. The 2.7 Kb central region contains three resistance genes: the kanamycin-neomycin resistance gene, a gene coding for resistance to CL990 an antimitotic-antibiotic compound of the bleomycin family and a third gene that confers streptomycin resistance in some bacterial species but is cryptic in E. coli. A Tn5* mutant able to express streptomycin resistance in E. coli was isolated. With this mutant, it was demonstrated that in E. coli the expression of the three resistance genes is coordinated in a single operon.

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D( -) or for L( + ) lactic acid; some species contained both enzymes. For each species there was a strict correlation between the stereospecificity of the NAD-dependent lactic dehydrogenases found in extracts and the type of lactic acid produced during growth, i.e. D(-), L(+) or DL. The L-lactic dehydrogenases (NAD-dependent) of Lactobacillus casei and L. fermenti were not reversible and consequently could not be detected after electrophoresis. Only those NAD-independent lactic dehydrogenases able to reduce phenazine methosulphate could be detected by the method of development used. Such enzymes were found in extracts of some homofermentative lactobacilli.The number and the nature of the lactic dehydrogenases and their respective electrophoretic mobilities are constant within a species. Therefore the electrophoretic migration of lactic dehydrogenases of lactobacilli is a useful taxonomic marker for species differentiation.

The system involving the oxidation of methanol to formaldehyde in Gram-negative methylotrophic bacteria is complex. A total of 32 genes have been reported, termed mox, for methanol oxidation, and it is possible that more will be identified. Some mox genes carrying out completely different functions have been given the same designations by different laboratories and others have been given separate designations that were later discovered to be the same. It is now important to change the mox nomenclature to remedy this confusing situation. This communication proposes a new nomenclature for genes involved in methanol oxidation based on currently known linkage groups.