Son G. Nguyen

Analysis of swine fecal microbiota at various growth stages

Recent obesity studies in humans and rodents have suggested that host weight gain is significantly associated with energy harvesting efficiency which is regulated by gut microbiota. Antibiotic growth promoters have been banned as feed additives in many countries. In this study, we aimed to provide knowledge of swine fecal microbiota by analyzing bacterial 16S rRNA gene sequences. Our results showed that swine fecal bacterial composition varied at each growth stage. Bacteroidetes decreased as the swine gained weight and unclassified genera significantly increased at later growth stages. Operational taxonomic unit (OTU) distribution analysis showed that the bacterial community difference was most significant between growers and finishers, while analysis of shared OTUs indicated a greater proportion of common species between growers and finishers. The differential abundance test between growers and finishers detected that nearly half of the species were shared OTUs, suggesting that differential abundance of each bacterial species predominantly controls bacterial community differences. Although functions of these bacteria are yet to be identified, understanding differences in fecal microbiota between each growth stage will provide additional insights for further studies related to swine gut microbiota.

Laminarin favorably modulates gut microbiota in mice fed a high-fat diet

We investigated the anti-obesity effects of the potential prebiotic, laminarin, on mice fed a high-fat diet. A metagenomics approach was applied to characterize the ecological and functional differences of gut microbiota among mice fed a normal diet (CTL), a high-fat diet (HFD), and a laminarin-supplemented high-fat diet (HFL). The HFL mice showed a slower weight gain than the HFD mice during the laminarin-feeding period, but the rate of weight gain increased after the termination of laminarin supplementation. Gut microbial community analysis showed clear differences between the CTL and HFD mice, whereas the HFL mice were between the two. A higher abundance of carbohydrate active enzymes was observed in the HFL mice compared to the HFD mice, with especially notable increases in glycoside hydrolase and polysaccharide lyases. A significant decrease in Firmicutes and an increase in the Bacteroidetes phylum, especially the genus Bacteroides, were observed during laminarin ingestion. Laminarin ingestion altered the gut microbiota at the species level, which was re-shifted after termination of laminarin ingestion. Therefore, supplementing laminarin could reduce the adverse effects of a high-fat diet by shifting the gut microbiota towards a higher energy metabolism. Thus, laminarin could be used to develop anti-obesity functional foods. Our results also suggest that laminarin would need to be consumed regularly in order to prevent or manage obesity.

Effects of the Antibiotics Growth Promoter Tylosin on Swine Gut Microbiota.

Tylosin has been used as a livestock feed additive and antibiotic growth promoter for many years. However, the mode of action by which tylosin enhances animal growth is unclear. We used high-throughput sequencing of 16S rRNA genes to investigate the effects of tylosin as a feed additive on swine gut microbiota. No significant difference in the rate of weight increase was observed between control and tylosin-treated pigs during a 10-week feeding trial. However, tylosin-treated pigs showed rapid increases in the relative abundance of the phylum Firmicutes. Increases in Firmicutes species are associated with (so-called) obese-type gut microbiota. The abundance of species of four families of the phylum Firmicutes (Streptococcaceae, Peptococcaceae, Peptostreptococcaceae, and Clostridiaceae) correlated positively with host weight gain. The abundance of Streptococcaceae family bacteria was least affected by tylosin treatment. Distribution analysis of operational taxonomic units (OTUs) showed that both control and tylosin-treated pigs exhibited similar OTU alterations during growth. However, the tylosin-treated group showed distinctive alterations in gut microbiota when the host weighed approximately 60 kg, whereas similar alterations occurred at around 80 kg in the control group. Our results suggest that use of tylosin accelerates maturation of swine gut microbiota rather than altering its composition.

Influence of seawater intrusion on microbial communities in groundwater

Groundwater is the sole source of potable water on Jeju Island in the Republic of (South) Korea. Groundwater is also used for irrigation and industrial purposes, and it is severely impacted by seawater intrusion in coastal areas. Consequently, monitoring the intrusion of seawater into groundwater on Jeju is very important for health and environmental reasons. A number of studies have used hydrological models to predict the deterioration of groundwater quality caused by seawater intrusion. However, there is conflicting evidence of intrusion due to complicated environmental influences on groundwater quality. Here we investigated the use of next generation sequencing (NGS)-based microbial community analysis as a way to monitor groundwater quality and detect seawater intrusion. Pristine groundwater, groundwater from three coastal areas, and seawater were compared. Analysis of the distribution of bacterial species clearly indicated that the high and low salinity groundwater differed significantly with respect to microbial composition. While members of the family Parvularculaceae were only identified in high salinity water samples, a greater percentage of the phylum Actinobacteria was predominantly observed in pristine groundwater. In addition, we identified 48 shared operational taxonomic units (OTUs) with seawater, among which the high salinity groundwater sample shared a greater number of bacterial species with seawater (6.7%). In contrast, other groundwater samples shared less than 0.5%. Our results suggest that NGS-based microbial community analysis of groundwater may be a useful tool for monitoring groundwater quality and detect seawater intrusion. This technology may also provide additional insights in understanding hydrological dynamics.