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Study region The study region is the coastal Tra Vinh province located in Mekong Delta, Vietnam Study focus The study aims to clarify the ambiguities in implementing Vietnam's regulation on restrictions of groundwater abstraction in Mekong Delta. Three ambiguities were identified, namely, how should half of the saturated thickness of the unconfined aquifer be computed; is the water level depth of 30 m for the confined aquifer sufficient to prevent seawater intrusion and land subsidence; and why is the interference of water use rights of neighbouring provinces not considered. Numerical groundwater flow, saltwater transport and land subsidence were constructed for Tra Vinh province to assess water level requirements from Vietnam regulation and important constraints for groundwater sustainability. The model results show that although all scenarios satisfy groundwater level requirements from the Vietnam regulation, only the mitigation scenario combined with reducing abstraction and increasing recharge can lead to sustainable development. New hydrological insights for the region The current groundwater abstraction in Tra Vinh province has caused groundwater storage depletion and induced seawater intrusion, land subsidence, and captured groundwater inflow from neighbouring provinces. When the business as usual continues, seawater may intrude 4–5 km inland and cumulative land subsidence may reach 1.5 m by 2100. Reduction of current abstraction by 50% supplemented with the increase of recharge by 1.5 times in the dunes can lead to sustainable development.

The early intestinal colonization of functional microbial groups plays an essential role in infant gut health, with most studies targeting the initial colonization period from birth to 6 months of age. In a previous report, we demonstrated the metabolic cross-feeding of lactate and identified keystone species specified for lactate utilization in fecal samples of 40 healthy infants. We present here the extension of our longitudinal study for the period from 6 months to 2 years, with a focus on the colonization of functional groups involved in lactate metabolism and butyrate production. We captured the dynamic changes of the gut microbiota and reported a switch in the predominant lactate-producing and lactate-utilizing bacteria, from Veillonella producing propionate in the first year to Anaerobutyrycum hallii producing butyrate in the second year of life. The significant increase in butyrate producers and fecal butyrate concentration was also pinpointed to the weaning period between 6 and 10 months. Correlation analyses further suggested, for the first time, the metabolic cross-feeding of hydrogen in infants. In conclusion, our longitudinal study of 40 Swiss infants provides important insights into the colonization of functional groups involved in lactate metabolism and butyrate production in the first 2 years of life.

The global prevalence of Fe deficiency is high and a common corrective strategy is oral Fe supplementation, which may affect the commensal gut microbiota and gastrointestinal health. The aim of the present study was to investigate the impact of different dietary Fe concentrations on the gut microbiota and gut health of rats inoculated with human faecal microbiota. Rats (8 weeks old, n 40) were divided into five (n 8 each) groups and fed diets differing only in Fe concentration during an Fe-depletion period (12 weeks) and an Fe-repletion period (4 weeks) as follows: (1) Fe-sufficient diet throughout the study period; (2) Fe-sufficient diet followed by 70mg Fe/kg diet; (3) Fe-depleted diet throughout the study period; (4) Fe-depleted diet followed by 35mg Fe/kg diet; (5) Fe-depleted diet followed by 70mg Fe/kg diet. Faecal and caecal samples were analysed for gut microbiota composition (quantitative PCR and pyrosequencing) and bacterial metabolites (HPLC), and intestinal tissue samples were investigated histologically. Fe depletion did not significantly alter dominant populations of the gut microbiota and did not induce Fe-deficiency anaemia in the studied rats. Provision of the 35mg Fe/kg diet after feeding an Fe-deficient diet significantly increased the abundance of dominant bacterial groups such as Bacteroides spp. and Clostridium cluster IV members compared with that of an Fe-deficient diet. Fe supplementation increased gut microbial butyrate concentration 6-fold compared with Fe depletion and did not affect histological colitis scores. The present results suggest that Fe supplementation enhances the concentration of beneficial gut microbiota metabolites and thus may contribute to gut health

The aetiology of colic, a functional gastrointestinal disorder in infants, is not yet resolved. Different mechanisms have been suggested involving the gut microbiota and intermediate metabolites such as lactate. Lactate can be metabolized by lactate-utilizing bacteria (LUB) to form different end-products. Using a functional approach, we hypothesized that H2 production and accumulation by LUB is associated with the development of colic. The LUB communities in the feces of forty infants, including eight colicky infants, were characterized using a combination of culture- and molecular-based methods, and metabolite concentrations were measured by HPLC. Interactions among LUB strains isolated from feces were investigated with pure and mixed cultures using anaerobic techniques. We emphasized high prevalence of crying, flatulence, colic and positive correlations thereof in the first 3 months of life. Crying infants showed significantly higher ratio of LUB non-sulfate-reducing bacteria (LUB non-SRB) (H2-producer), to LUB SRB (H2-utilizer) at 3 months. Colicky infants had significantly higher number of H2-producing Eubacterium hallii at 2 weeks compared to non-colicky infants. We revealed the function of Desulfovibrio piger and Eubacterium limosum to reduce H2 accumulation in co-cultures with H2-producing Veillonella ratti. Our data suggest that the balance between H2-producing and H2-utilizing LUB might contribute to colic symptoms.

The global prevalence of Fe deficiency is high and a common corrective strategy is oral Fe supplementation, which may affect the commensal gut microbiota and gastrointestinal health. The aim of the present study was to investigate the impact of different dietary Fe concentrations on the gut microbiota and gut health of rats inoculated with human faecal microbiota. Rats (8 weeks old, n 40) were divided into five (n 8 each) groups and fed diets differing only in Fe concentration during an Fe-depletion period (12 weeks) and an Fe-repletion period (4 weeks) as follows: (1) Fe-sufficient diet throughout the study period; (2) Fe-sufficient diet followed by 70mg Fe/kg diet; (3) Fe-depleted diet throughout the study period; (4) Fe-depleted diet followed by 35mg Fe/kg diet; (5) Fe-depleted diet followed by 70mg Fe/kg diet. Faecal and caecal samples were analysed for gut microbiota composition (quantitative PCR and pyrosequencing) and bacterial metabolites (HPLC), and intestinal tissue samples were investigated histologically. Fe depletion did not significantly alter dominant populations of the gut microbiota and did not induce Fe-deficiency anaemia in the studied rats. Provision of the 35mg Fe/kg diet after feeding an Fe-deficient diet significantly increased the abundance of dominant bacterial groups such as Bacteroides spp. and Clostridium cluster IV members compared with that of an Fe-deficient diet. Fe supplementation increased gut microbial butyrate concentration 6-fold compared with Fe depletion and did not affect histological colitis scores. The present results suggest that Fe supplementation enhances the concentration of beneficial gut microbiota metabolites and thus may contribute to gut health