BackgroundIt has been reported that the composition of human gut microbiota changes with age; however, few studies have used molecular techniques to investigate the long-term, sequential changes in gut microbiota composition. In this study, we investigated the sequential changes in gut microbiota composition in newborn to centenarian Japanese subjects.ResultsFecal samples from 367 healthy Japanese subjects between the ages of 0 and 104 years were analyzed by high-throughput sequencing of amplicons derived from the V3-V4 region of the 16S rRNA gene. Analysis based on bacterial co-abundance groups (CAGs) defined by Kendall correlations between genera revealed that certain transition types of microbiota were enriched in infants, adults, elderly individuals and both infant and elderly subjects. More positive correlations between the relative abundances of genera were observed in the elderly-associated CAGs compared with the infant- and adult-associated CAGs. Hierarchical Ward’s linkage clustering based on the abundance of genera indicated five clusters, with median (interquartile range) ages of 3 (0–35), 33 (24–45), 42 (32–62), 77 (36–84) and 94 (86–98) years. Subjects were predominantly clustered with their matched age; however, some of them fell into mismatched age clusters. Furthermore, clustering based on the proportion of transporters predicted by phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) showed that subjects were divided into two age-related groups, the adult-enriched and infant/elderly-enriched clusters. Notably, all the drug transporters based on Kyoto Encyclopedia of Genes and Genomes (KEGG) Orthology groups were found in the infant/elderly-enriched cluster.ConclusionOur results indicate some patterns and transition points in the compositional changes in gut microbiota with age. In addition, the transporter property prediction results suggest that nutrients in the gut might play an important role in changing the gut microbiota composition with age.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0708-5) contains supplementary material, which is available to authorized users.

Bifidobacteria are one of the major components in human microbiota that are suggested to function in maintaining human health. The colonization and cell number of Bifidobacterium species in human intestine vary with ageing. However, sequential changes of Bifidobacterium species ranging from newborns to centenarians remain unresolved. Here, we investigated the gut compositional changes of Bifidobacterium species over a wide range of ages. Faecal samples of 441 healthy Japanese subjects between the ages of 0 and 104 years were analysed using real-time PCR with species-specific primers. B. longum group was widely detected from newborns to centenarians, with the highest detection rate. B. breve was detected in approximately 70% of children under 3 years old. B. adolescentis and B. catenulatum groups were predominant after weaning. B. bifidum was detected at almost all ages. The detection rate of B. dentium was higher in the elderly than in other ages. B. animalis ssp. lactis was detected in 11.4% of the subjects and their ages were restricted. B. gallinarum goup was detected in only nine subjects, while B. minimum and B. mongoliense were undetected at any age. The presence of certain Bifidobacterium groups was associated with significantly higher numbers of other Bifidobacterium species/subspecies. Inter-species correlations were found among each species, exception for B. animalis ssp. lactis. These results revealed the patterns and transition points with respect to compositional changes of Bifidobacterium species that occur with ageing, and the findings indicate that there may be symbiotic associations between some of these species in the gut microbiota.Electronic supplementary materialThe online version of this article (doi:10.1007/s00284-017-1272-4) contains supplementary material, which is available to authorized users.

Streptococcus suis, a major porcine pathogen and an important zoonotic agent, is considered to be composed of phenotypically and genetically diverse strains. However, recent studies reported several “S. suis-like strains” that were identified as S. suis by commonly used methods for the identification of this bacterium, but were regarded as distinct species from S. suis according to the standards of several taxonomic analyses. Furthermore, it has been suggested that some S. suis-like strains can be assigned to several novel species. In this review, we discuss the current taxonomical situation of S. suis with a focus on (1) the classification history of the taxon of S. suis; (2) S. suis-like strains revealed by taxonomic analyses; (3) methods for detecting and identifying this species, including a novel method that can distinguish S. suis isolates from S. suis-like strains; and (4) current topics on the reclassification of S. suis-like strains.

Lactobacilli with tannase activity were isolated from human feces and fermented foods. A PCR-based taxonomic assay revealed that the isolates belong to Lactobacillus plantarum, L. paraplantarum, and L. pentosus. Additional studies on a range of Lactobacillus species from established culture collections confirmed that this enzymatic activity is a phenotypic property common to these three species.

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