Bifidobacterium inopinatum sp. nov. and Bifidobacterium denticolens sp. nov., two new species isolated from human dental caries.

In a previous investigation of bifidobacteria isolated from human dental caries (V. Scardovi and F. Crociani, Int. J. Syst. Bacteriol. 24:6-20, 1974), 40 strains were assigned to the new species Bifidobacterium dentium. In this study we examined 70 new strains of bifidobacteria isolated from dental caries. The morphological characteristics, biochemical reactions, fermentation patterns, end products from glucose metabolism, protein electrophoretic patterns, levels of DNA hybridization, and DNA G+C contents of these organisms revealed that they belong to three different taxa. One of these taxa was identified as B. dentium. The other two are described as the following new Bifidobacterium species in this paper: Bifidobacterium inopinatum (type strain, DSM 10107) and Bifidobacterium denticolens (type strain, DSM 10105). The two new species differ from other Bifidobacterium species in their morphological characteristics (especially B. inopinatum, with its very small coccoid cells), in their carbohydrate fermentation patterns (most strains ferment dextran, and B. inopinatum does not ferment galactose), and in their DNA base compositions (especially B. inopinatum).

Characterization of the plasmid pVS809 from Bifidobacterium globosum.

A plasmid from a B. globosum strain was cut with 38 restriction enzymes and a physical map was constructed. Out of a total of 121 clones from curing experiments, plasmid was lost in 58% and 100% for acridine orange and ethidium bromide curing agent respectively. The plasmid does not exist as a chromosomal integrated form. An attempt to determine phenotypic characters encoded by the plasmid was made by electrophoretic analyses of the total proteins.

Bifidobacterial cell wall proteins (BIFOP) in Bifidobacterium globosum.

Nearly 150 strains of Bifidobacterium globosum were isolated from faeces of calf, chicken, lamb, rabbit and rat, from sewage, from rumen content and from human infant faeces between 1962 and 1973 and scored by SDS-PAGE for the presence of cell-wall-related proteins, i.e. BIFOP (bifid outer proteins); their apparent molecular masses ranged from 94.5 to 34 kDa and were designated A to L. Purified preparations from six of these ten proteins were employed to produce polyclonal rabbit antisera for use in immunoblots to investigate the interrelationships of the major antigens, A, B and C (94.5-85.5 kDa) and their distribution in strains of various origin. Two antigens differently migrating (or polymorphic forms) reacted with anti-BIFOP F serum (called F- and F+); the identity of BIFOP E with respect to these antigens was studied with anti-E serum. Only one antigen in all strain preparations reacted to anti-BIFOP H serum, which was raised against an antigen purified from a 13.5-MDa plasmid-bearing strain from rumen.

Phase variations in Bifidobacterium animalis.

Strains isolated from rabbit, chicken, and rat feces and from sewage and fermented milk products, all identified as Bifidobacterium animalis, were found to show phase variations in colony appearance and in cellular morphology. The rate of transition in a switching system from opaque to transparent colonies and vice versa was determined. Differences in protein components and in penicillin-binding proteins (PBPs) of the cells from different colony types are shown.

Related structures in the plasmid profiles of Bifidobacterium longum.

The plasmid profiles of 123 strains of B. longum were examined with the Southern blot-hybridization technique to reveal the existence of related structures. B. longum is the apparently unique species among those commonly found in man, which harbours extrachromosomal elements. Seven different structures were found and their frequency and distribution given. Twelve strains were used a source of probes in the hybridization experiments.

Related structures in the plasmid profiles of Bifidobacterium asteroides, B. indicum and B. globosum.

Seventy strains of B. asteroides isolated from the honey bees Apis mellifera and A. cerana raised in 15 different countries, 73 strains of B. indicum from Apis dorsata and A. cerana from The Philippines and 28 strains of B. globosum isolated from feces of various animals and sewage, were studied for the existence of related structures among their plasmid complements with the Southern blot-hybridization technique. Thirteen different structures were found in B. asteroides and three in B. indicum and B. globosum. A total of twenty five strains were used as source of probes in the hybridization experiments.

Plasmids in the genus Bifidobacterium.

A total of 1461 bacterial isolates, representing 24 different species of the genus Bifidobacterium, were examined for the presence of plasmid DNA. Approximately 20% of the isolates contained detectable plasmids, but only four species were presented: B. longum, the predominant bifid species in the human intestine; B. globosum, the most common in animals; and B. asteroides and B. indicum, species found exclusively in the intestines of western and asiatic honey bees, respectively. Multiple plasmids were common among isolates of B. longum and B. asteroides, while all plasmid-bearing isolates of B. globosum and 60% of B. indicum isolates contained only one plasmid each. Certain multiple plasma profiles were predominant among the B. longum and B. asteroides isolates.

Immunological relationships among transaldolases in the genus Bifidobacterium.

Antisera were prepared against electrophoretically homogeneous transaldolase (dihydroxyacetone transferase, E.C. 2.2.1.2.) of Bifidobacterium thermophilum (B. ruminale) RU326 (ATCC25866), B. cuniculi RA93 (ATCC27916) and B. 'minimum' (homology group) F392 (ATCC 27538). Crude extracts of eighty six strains previously assigned to twenty one species of the genus Bifidobacterium on the basis of deoxyribonouclelic acid (DNA) homology (DNA-DNA hybridization), were compared by double diffusion tests on Ouchterlony plates. Eight groups of identical antigenic specificity were recognized. By analysis of the spur formation, the groups of identical specificity were arranged in preliminary sequences of decreasing similarity to each of the three homologous transaldolases used as reference points. The relationships between immunological data and the genetic similarity among the species of the genus measured by means of DNA-DNA hybridization were discussed together with some relevant points of bifidal ecology.

Starch gel electrophoresis of fructose-6-phosphate phophoketolase in the genus Bifidobacterium.

Three groups of nomenspecies of the genus Bifidobacterium were distinguished by the different mobility of their fructose-6-phosphate phosphoketolase in starchgel electrophoresis; there is apparently a close relatedness between electrophoretic type of phosphoketolase and habitat.