Adhesion, autoaggregation and hydrophobicity of 13 strains of Bifidobacterium longum.

To identify bacterial traits related to adhesion ability in human bifidobacteria, 13 strains of Bifidobacterium longum isolated from human gastric juice and intestine were studied. Strains were tested for their capability to adhere to Caco-2 cells and classified as adhesive (Adh+) or non-adhesive (Adh-). Adh+ and Adh- strains were then investigated for their autoaggregation ability and surface hydrophobicity. Comparing the properties of Adh+ and Adh-, we observed that strains were able to adhere to cell monolayers if they autoaggregate and manifest a good degree of hydrophobicity as determined by microbial adhesion to hydrocarbons. These two traits could be used for preliminary screening to identify potentially adherent isolates.

Autoaggregation and adhesion ability in a Bifidobacterium suis strain.

On the basis of autoaggregation ability, two different phenotypes (Agg+ and Agg-) were selected from a strain (BSu895) of Bifidobacterium suis. The relationship between autoaggregation and adhesion of bacteria to intestinal tissue was investigated by observing the adhesivity of the two phenotypic variants to ileum and colon tissue pieces collected from six new-born piglets. The results suggest that there is a good relationship between autoaggregation and adhesion as variant Agg+ (autoaggregating) has a stronger adhesion ability than Agg- (non-autoaggregating).

Transformation of Bifidobacterium longum with pRM2, a constructed Escherichia coli-B. longum shuttle vector.

An Escherichia coli-Bifidobacterium longum shuttle vector, designated pRM2, was constructed by cloning a B. longum plasmid and an enterococcal spectinomycin resistance gene into a commercial E. coli vector. The plasmid was successfully introduced into B. longum cells by electroporation and into E. coli cells by both electroporation and chemical transformation.

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 and phages in Bifidobacterium longum.

Fourteen strains of Bifidobacterium longum were tested for phage production with UV and mitomycin C as inducing agents. Only four strains released phage-like particles; of these four strains, two harbour plasmids, while two are apparently plasmid free. The induced phages have heads of dimensions ranging from 49 to 56 nm and tails from 76 to 268 nm long. No correlation is evident between any of the large variety of plasmids of B. longum and induced phages.

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.

Preliminary quantification of immunological relationships among the transaldolases of the genus Bifidobacterium.

The immunological relatedness among the transaldolases (dihydroxyacetone transferase, E.C. 2.2.1.2) of twenty species of the genus Bifidobacterum has been tested by the microcomplement fixation method, using B. thermophilum (B. ruminale) RU326 (= ATCC 25866), B. cuniculi RA93 (= ATCC 27916) and B. 'minimum' (DNA homology group) F392 (= ATCC 27916) as references. Based on the serological relationships of the transaldolases, expressed either as indices of dissimilarity or as immunological distances, the twenty species of the genus Bifidobacterium were arranged into clusters. These clusters generally coincided with the immunological groups obtained previously by the immunodiffusion method (Sgorbati and Scardovi, 1979).

Purification and properties of two fructose-6-phosphate phosphoketolases in Bifidobacterium.

Fructose-6-phosphate phosphoketolase was purified from type strains of two species of the genus Bifidobacterium: B. globosum and B. dentium. The first species has a preferred "animal" habitat, like feces of animals and rumen of cattle; the latter is harboured in "human" habitat, like feces and dental caries of man. Two electrophoretic types of phosphoketolase (F6PPK) were previously distinguished and called "animal" and "human" type according to the habitat of the bifid organism. The purified preparations of these two phosphoketolases displayed very different optimum pH range, metal activator and molecular weight; outstanding difference was found in the substrate specificity: the enzyme from B. globosum was able to split xylulose-5-P as well as fructose-6-P, whereas the phosphoketolase from B. dentium appeared to be specific for fructose-6-P.

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.