Segmented filamentous bacteria (SFB) are indigenous gut commensal bacteria. They are commonly detected in the gastrointestinal tracts of both vertebrates and invertebrates. Despite the significant role they have in the modulation of the development of host immune systems, little information exists regarding the presence of SFB in humans. The aim of this study was to investigate the distribution and diversity of SFB in humans and to determine their phylogenetic relationships with their hosts. Gut contents from 251 humans, 92 mice and 72 chickens were collected for bacterial genomic DNA extraction and subjected to SFB 16S rRNA-specific PCR detection. The results showed SFB colonization to be age-dependent in humans, with the majority of individuals colonized within the first 2 years of life, but this colonization disappeared by the age of 3 years. Results of 16S rRNA sequencing showed that multiple operational taxonomic units of SFB could exist in the same individuals. Cross-species comparison among human, mouse and chicken samples demonstrated that each host possessed an exclusive predominant SFB sequence. In summary, our results showed that SFB display host specificity, and SFB colonization, which occurs early in human life, declines in an age-dependent manner.

BackgroundLactobacillus plantarum is a plant-associated bacterial species but it has also been found in human, mouse and porcine gastrointestinal tracts. It can ferment a broad spectrum of plant carbohydrates; it is tolerant of bile salts and low pH, and it has antagonistic potential against intestinal pathogens. However, experiments reporting the use of L. plantarum as a probiotic are limited. In this study, the effects of L. plantarum ZJ316 isolated from infant fecal samples on pig growth and pork quality were investigated.ResultsOne hundred and fifty newly weaned pigs were selected randomly and divided into five groups. Group 1 was fed a diet supplemented with the antibiotic mequindox; Groups 2, 3 and 4 were fed a diet supplemented with L. plantarum and no antibiotic; and Group 5 was fed a mixture of mequindox and L. plantarum. After a 60 days initial treatment, samples were collected for evaluation. The results showed that, the L. plantarum ZJ316 has probiotic effects on pig growth and that these effects are dose dependent. The effects of a dose of 1 × 109 CFU/d were more pronounced than those of a dose of 5 × 109 CFU/d or 1 × 1010 CFU/d. In Group 2 (1 × 109 CFU/d), the diarrhea (p = 0.000) and mortality rates (p = 0.448) were lower than in antibiotic-treated pigs (Group 1), and the daily weight gain (p = 0.001) and food conversion ratios were better (p = 0.005). Improved pork quality was associated with Lactobacillus treatment. pH (45 min, p = 0.020), hardness (p = 0.000), stickiness (p = 0.044), chewiness (p = 0.000), gumminess (p = 0.000) and restoring force (p = 0.004) were all significantly improved in Lactobacillus-treated pigs (Group 2). Although we found that L. plantarum exerted probiotic effects on pig growth and pork quality, the mechanisms underlying its action require further study. Polymerase chain reaction-denaturing gradient gel electrophoresis results showed that the gut bacterial communities in Lactobacillus- and antibiotic-treated pigs were very similar and the quantity of L. plantarum ZJ316 was below the detection limits of DGGE-band sequencing. The concentration of short-chain fatty acids in Lactobacillus- and antibiotic-treated fecal samples were not significantly different (p = 0.086). However, the villus height of ilea (p = 0.003), jejuna (p = 0.000) and duodena (p = 0.036) were found to be significantly improved by Lactobacillus treatment.ConclusionL. plantarum ZJ316 was found to have probiotic effects, improving pig growth and pork quality. The probiotic mechanism might not involve L. plantarum colonization and alteration of the gut bacterial community. Rather, it might be related to the inhibition of the growth of opportunistic pathogens and promotion of increased villus height.

The transition from a sterile gut environment to the development of microbiota in the newborns is not fully understood. The objective of this study was to investigate the impact of exposure to bacterial communities on the development of gut microbiota in the newly hatched chicken. A total of 90 as-hatched chicks were divided into three groups. Groups A and B were treated with inocula of the cecal origin, whereas group C was fed with sterile water. The major bacteria in Inoculum-I to treat group A included Bacteroides (20.7%), Lachnospiraceae (17.2%) and unclassified Ruminococcaceae (16.1%), whereas group B was introduced with Inoculum-II composed of Prevotella (37.9%), Acidaminococcus (16.1%) and Dorea (12.6%). Analyses of the ileal and cecal contents over a period of 15 days showed that Inoculum-I resulted in a higher rate of colonization than Inoculum-II, but the colonization was predominantly in the cecum. The influence of Inoculum-II on group B was similar to that of water on group C, showing only a marginal effect on colonization. Microarray analysis showed that each group presented a distinct pattern of gene expression in the ileum. In group A, the most obvious changes were noted in genes controlling the function of ion transport, cell cycle and chromosome maintenance, suggesting that the inocula influenced gene expression. Our findings indicate that initial exposure to different bacterial communities could lead to the development of distinct microbiota and gene expression in the gut. It is possible to manipulate the gut microbiota by feeding to a proper bacterial composition at an early age.