Shock-absorbing effect of flooring-adopted mechanical metamaterial technology and its influence on the gait and balance of older adults.

OBJECTIVE: To elucidate the performance of a shock-absorbing floor material with a mechanical metamaterial (MM-flooring) structure and its effect on the gait and balance of older adults. METHODS: The drop-weight impact was applied to evaluate the shock-absorbing performance. The falling weight was adjusted equivalent to the energy exerted on the femur of an older woman when she falls, which was evaluated on the MM-flooring and six other flooring materials.Nineteen healthy people over the age of 65 years participated in the gait and balance evaluations. The timed up and go and two-step tests were adopted as gait performance tests, and the sway-during-quiet-balance test with force plates and the functional reach test (FRT) were adopted as balance tests. All the participants underwent these tests on the MM-flooring, shock-absorbing mat and rigid flooring. RESULTS: The shock-absorbing performance test revealed that MM-flooring has sufficient shock-absorbing performance, and suggesting that it may reduce the probability of fractures in the older people when they fall. The results of the gait performance test showed that the participants demonstrated the same gait performance on the MM-flooring and the rigid floor. In the quiet standing test, MM-flooring did not affect the balance function of the participants to the same extent as the rigid floor, compared with the shock-absorbing mat. In the FRT, no significant differences were found for any of the flooring conditions. CONCLUSIONS: MM-flooring has the potential to prevent fractures attributed to falls and does not affect the gait or balance of older adults.

Isolation and transposition properties of ISBlo11, an active insertion sequence belonging to the IS3 family, from Bifidobacterium longum 105-A.

Transposon mutagenesis systems are still under development in bifidobacteria, partly because intrinsic active insertion sequences are not well characterized in bifidobacteria. Here, we isolated an active insertion sequence, ISBlo11, from Bifidobacterium longum 105-A using a sacB-based counterselection system, which is generally used to screen for active insertion sequences from bacterial genomes. ISBlo11 is 1432 bp long and belongs to the IS3 family. It has a single ORF encoding a transposase and 25-bp inverted repeats at its termini. Full-length copies of ISBlo11 are specifically conserved among certain B. longum genomes and exist in different sites. Transposition analysis of an artificial ISBlo11 transposon using an Escherichia coli conjugation system revealed that ISBlo11 has adequate transposition activity, comparable to the reported activity of IS629, another IS3 family element initially isolated from Shigella sonnei. ISBlo11 also showed low transposition selectivity for non-conserved 3- or 4-bp target sequences. These characteristics of ISBlo11 seem suitable for the development of a new transposon mutagenesis system in bifidobacteria.

Effects of active hexose correlated compound on the seasonal variations of immune competence in healthy subjects.

The aim of this study was to evaluate the effects of active hexose correlated compound intake on the immune competence in healthy volunteers. Thirty-four subjects were randomized to receive placebo or active hexose correlated compound at 1.0 g/d for 4 weeks in early winter. Natural killer cell activity was significantly increased in both groups during the study period, the natural killer cell number, however, was not altered in the active hexose correlated compound group while placebo group showed remarkable decline. In addition, the score of immunological vigor, an index of total immune competence, was maintained in the active hexose correlated compound group although that of placebo group lowered during the test period. These results suggested that the continuous active hexose correlated compound intake maintained the immune competence against the seasonal change.

Functional analysis of bifidobacterial promoters in Bifidobacterium longum and Escherichia coli using the α-galactosidase gene as a reporter.

Heterologous gene expression in bifidobacteria requires weak, strong, and inducible promoters depending on the objectives of different expression studies. Weak promoters in Escherichia coli can also be desirable for stable heterologous gene cloning. Here, we developed a reporter system using the Bifidobacterium longum α-galactosidase gene and investigated the activity and inducibility of seven bifidobacterial promoters in B. longum and their activities in E. coli. These studies revealed diverse promoter activities. Three promoters were highly active in B. longum, but only slightly active in E. coli. Among these, two phosphoketolase gene (xfp) promoters exhibited strong activity in B. longum cells grown on glucose. In contrast, the promoter activity of the fructose transporter operon (fruEKFG) was strongly induced by carbohydrates other than glucose, including fructose, xylose, and ribose. These promoters will allow strong or highly inducible expression in bifidobacteria and stable gene cloning in E. coli. In contrast to the functions of these promoters, the promoter of sucrose-utilization operon cscBA showed very high activity in E. coli but low activity in B. longum. Other three promoters were functional in both B. longum and E. coli. In particular, two sucrose phosphorylase gene (scrP) promoters showed inducible activity by sucrose and raffinose in B. longum, indicating their applicability for regulated expression studies. The diverse promoter functions revealed in this study will contribute to enabling the regulated expression of heterologous genes in bifidobacteria research.

Development of a double-crossover markerless gene deletion system in Bifidobacterium longum: functional analysis of the α-galactosidase gene for raffinose assimilation.

Functional analysis of Bifidobacterium genes is essential for understanding host-Bifidobacterium interactions with beneficial effects on human health; however, the lack of an effective targeted gene inactivation system in bifidobacteria has prevented the development of functional genomics in this bacterium. Here, we report the development of a markerless gene deletion system involving a double crossover in Bifidobacterium longum. Incompatible plasmid vectors were used to facilitate a second crossover step. The conditional replication vector pBS423-ΔrepA, which lacks the plasmid replication gene repA, was integrated into the target gene by a first crossover event. Subsequently, the replicative plasmid pTBR101-CM, which harbors repA, was introduced into this integrant to facilitate the second crossover step and subsequent elimination of the excised conditional replication vector from the cells by plasmid incompatibility. The proposed system was confirmed to work as expected in B. longum 105-A using the chromosomal full-length ß-galactosidase gene as a target. Markerless gene deletion was tested using the aga gene, which encodes α-galactosidase, whose substrates include raffinose. Almost all the pTBR101-CM-transformed strains became double-crossover recombinants after subculture, and 4 out of the 270 double-crossover recombinants had lost the ability to assimilate raffinose. Genotype analysis of these strains revealed markerless gene deletion of aga. Carbohydrate assimilation analysis and α-galactosidase activity measurement were conducted using both the representative mutant and a plasmid-based aga-complemented strain. These functional analyses revealed that aga is the only gene encoding a functional α-galactosidase enzyme in B. longum 105-A.

Technological advances in bifidobacterial molecular genetics: application to functional genomics and medical treatments.

Bifidobacteria are well known as beneficial intestinal bacteria that exert health-promoting effects in humans. In addition to physiological and immunological investigations, molecular genetic technologies have been developed and have recently started to be applied to clarify the molecular bases of host-Bifidobacterium interactions. These technologies include transformation technologies and Escherichia coli-Bifidobacterium shuttle vectors that enable heterologous gene expression. In this context, a plasmid artificial modification method that protects the introduced plasmid from the restriction system in host bifidobacteria has recently been developed to increase transformation efficiency. On the other hand, targeted gene inactivation systems, which are vital for functional genomics, seemed far from being practically applicable in bifidobacteria. However, remarkable progress in this technology has recently been achieved, enabling functional genomics in bifidobacteria. Integrated use of these molecular genetic technologies with omics-based analyses will surely boost characterization of the molecular basis underlying beneficial effects of bifidobacteria. Applications of recombinant bifidobacteria to medical treatments have also progressed.