- Volume 27, Issue 1, 1977

An antiserum against the purified glucose-6-phosphate dehydrogenase (EC 1.1.1.49) (G-6-P-DH) of Leuconostoc mesenteroides NCDO 768 has been prepared. Cross-reactions were observed with extracts of other strains of Leuconostoc, comprising named strains of L. lactis, L. mesenteroides, L. dextranicum, L. cremoris, and L. paramesenteroides. Cross-reactions were not obtained with L. oenos. The groups of identical specificity and their order of decreasing similarity toward the homologous enzyme were determined, and the results are consistent with those obtained previously with another G-6-P-DH antiserum from L. lactis NCDO 546. Thus, except for L. oenos, many strains of Leuconostoc comprising multiple (three or more) species might be considered as phenotypically diverse but genetically rather uniform in their line of descent from a common ancestor.

Six deoxyribonucleic acid (DNA)-DNA homology groups within 45 strains of the genus Leuconostoc were distinguishable through DNA-DNA hybridizations with four 3H-labeled reference DNA preparations from type or reference strains of the various known named species. There is good correspondence between two of these DNA-DNA hybridization groups and the species L. lactis and L. paramesenteroides. Strains named L. mesenteroides are heterogeneous, comprising three different hybridization groups. One of these groups includes all the strains named L. dextranicum and L. cremoris. These results agree precisely with previous results from an immunological study of the two isofunctional enzymes, glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and d-lactate dehydrogenase (EC 1.1.1.28), prepared from L. lactis NCDO 546 and L. mesenteroides NCDO 768 (ATCC 12291).

A biochemically and serologically homogeneous group of bacterial strains is described. The strains were selected because of their biochemical and serological similarity to strain number 145/46, which was isolated from a patient with the symptoms of clinical dysentery in the British Isles in 1946. Similar strains, sometimes called “serotype 147,” have been described as biochemically atypical members of Escherichia coli O group 25. Other studies have suggested, on the basis of biochemical tests and pathogenicity tests, that such strains should be classified as Shigella and the names Shigella 13, S. sofia, S. manolovii, and S. metadysenteriae have been proposed for them. Some workers have proposed that these strains should be regarded as intermediate between Shigella and E. coli. There is little doubt that these organisms have caused outbreaks of bloody diarrhoea resembling bacillary dysentery, but pathogenicity cannot be considered as a criterion for inclusion in the genus Shigella. The present study shows that the organisms can be classified biochemically as E. coli but they are atypical in being nonmotile, anaerogenic, and non-lactose-fermenting; serological studies show that these organisms can easily be distinguished from all currently recognised E. coli O groups (O1 to O163). It is proposed that these strains should be regarded as members of a new E. coli O group, O164.

The deoxyribonucleic acid (DNA) relationships among strains of the anaerobic Lactobacillus species L. ruminis and L. vitulinus, other lactobacilli with meso-diaminopimelic acid in the cell wall peptidoglycan, and L. jensenii were studied by DNA-DNA hybridization experiments. The DNA of strains assigned to L. ruminis had a high degree of homology. However, strains which have been assigned to L. vitulinus were genotypically heterogenous, three different unrelated groups being included. There was a very low level of homology between these two species and between them and L. plantarum subsp. mobilis, L. plantarum, and L. jensenii.

The base compositions of the deoxyribonucleic acids (DNAs) extracted from four representative strains of Dermatophilus congolensis and six of Geodermatophilus obscurus, which are described in the literature as belonging to the family Dermatophilaceae (Actinomycetales), were determined. The range of guanine plus cytosine contents (G+C) of their DNAs was 57.4 to 58.7 mol% for D. congolensis and 72.9 to 74.6 mol% for G. obscurus. This difference in DNA base composition is considered great enough to suggest a substantial genetic heterology between the two groups of organisms.

It is proposed to confer species rank to the genetically distinct streptococci that have been considered subspecies of Streptococcus mutans Clarke: S. mutans subsp. rattus Coykendall, S. mutans subsp. cricetus Coykendall, and S. mutans subsp. sobrinus Coykendall. S. mutans is defined to exclude phenotypically similar bacteria that have deoxyribonucleic acid (DNA) guanine plus cytosine contents appreciably different from 36 to 38 mol% and/or that do not demonstrate DNA base-sequence homology with the type strain. Streptococci that resemble S. mutans but that are quite disparate in molecular constitution are here regarded as comprising four new species: S. rattus (Coykendall) comb. nov., S. cricetus (Coykendall) comb. nov., S. sobrinus (Coykendall) comb. nov., and S. ferus sp. nov. NCTC 10449 is here designated as the neotype strain of S. mutans. The type strains of S. rattus, S. cricetus, S. sobrinus, and S. ferus are FA1 (= ATCC 19645), HS6 (= ATCC 19642), SL1, and 8S1, respectively. Simple biochemical tests serve to identify most strains of all five species. Serological procedures are capable of differentiating most human isolates.

The degree of binding was determined between deoxyribonucleic acid (DNA) preparations from nocardiae and “rhodochrous” strains and uracil-labeled DNA from three reference strains, Nocardia asteroides N668 and rhodochrous strains N11 and N54. In all cases, good congruence was found between the DNA reassociation data and that from numerical phenetic studies. Only a small degree of nucleotide sequence homology was found between the N. asteroides reference system and the other taxa studied, and there was evidence that N. asteroides is genetically heterogeneous. The moles percent guanine plus cytosine for the rhodochrous strains was within the range 58 to 67; the corresponding range for nocardiae was 64 to 68 mol%.

Two gram-negative, gas-vacuolated, aerotolerant, heterotrophic bacteria were isolated from the anaerobic digester of the Göttingen Waste Treatment Plant, Göttingen, Federal Republic of Germany. Pure white colonies of these organisms were picked from pour plates of basal growth medium containing 1.2% agar. The plates had been inoculated with digester sludge and incubated in a nitrogen-carbon dioxide atmosphere using the agar itself as the main carbon and energy source. One organism was rod shaped, and the other was vibrioid; both were encapsulated and nonmotile. The two organisms have identical deoxyribonucleic acid base compositions and identical nutritional requirements and fermentation characteristics. It is proposed that these organisms are stable morphovaric forms of a single species belonging to a new genus, for which the name Meniscus is proposed. The name proposed for the species (the type species) is Meniscus glaucopis sp. nov., of which the type strain is strain V (= ATCC 29398). The genus Meniscus does not appear to belong to any of the currently recognized families of bacteria.

A taxonomy for Bacillus subtilis, B. megaterium, B. cereus, B. pumilus, B. pasteurii, B. stearothermophilus, and Sporosarcina ureae has been constructed from comparisons of T1 ribonuclease digests of their respective 16S ribosomal ribonucleic acids. This molecular approach to systematics is shown to give results in essential agreement with traditional techniques for this group of organisms. In addition, the technique appears well suited for higher order classification, an area which has been difficult to approach with traditional techniques.

The genetic relatedness among streptomycetes capable of producing tetracycline, chlortetracycline, and oxytetracycline was studied by using deoxyribonucleic acid (DNA) association techniques. Reciprocal DNA association experiments yielded genetic similarity values ranging from 75 to 97% among Streptomyces aureofaciens ATCC 10762, S. aureofaciens ATCC 13911, S. lusitanus CBS 101A, and S. lusitanus var. tetracyclini 106-T ATCC 15843. These four strains should thus be considered members of the same species on the basis of genetic relatedness. On the bases of DNA association experiments, the degree of nucleotide similarity of morphologically heterogeneous strains with S. rimosus ATCC-10970 was 28 to 33%.