Cross-feeding between intestinal pathobionts promotes their overgrowth during undernutrition

Child undernutrition is a global health issue associated with a high burden of infectious disease. Undernourished children display an overabundance of intestinal pathogens and pathobionts, and these bacteria induce enteric dysfunction in undernourished mice; however, the cause of their overgrowth remains poorly defined. Here, we show that disease-inducing human isolates of Enterobacteriaceae and Bacteroidales spp. are capable of multi-species symbiotic cross-feeding, resulting in synergistic growth of a mixed community in vitro. Growth synergy occurs uniquely under malnourished conditions limited in protein and iron: in this context, Bacteroidales spp. liberate diet- and mucin-derived sugars and Enterobacteriaceae spp. enhance the bioavailability of iron. Analysis of human microbiota datasets reveals that Bacteroidaceae and Enterobacteriaceae are strongly correlated in undernourished children, but not in adequately nourished children, consistent with a diet-dependent growth synergy in the human gut. Together these data suggest that dietary cross-feeding fuels the overgrowth of pathobionts in undernutrition.

Physiological state of the sterlet × beluga hybrid (Asipenser ruthenus × Huso huso) when growing under ecological conditions in the Volga delta

Three-year-olds (15 individuals) and eight-year-olds (15 individuals) of the sterlet × beluga hybrid (Asipenser ruthenus × Huso huso), grown in mesh cages in the Volga delta, were studied in the third decade of September 2019 in order to establish the functional state of the organism by blood parameters reflecting the state erythron and metabolism. The results of the performed study found that the erythron system differs in a smaller number of blood erythrocytes in eight-year-olds (0,76 ± 0,04 × 1012l –1) compared with three-year-olds (0,98 ± 0,04 × 1012l –1), in the absence of differences in blood hemoglobin and serum iron. Analysis of the state of protein metabolism showed that the content of total protein and the activity of ASAT in serum were the same in the groups. The serum albumin content in eight-yearolds was 17,87 ± 0,92 g/l, which was significantly less than in three-year-olds (24,15 ± 1,78) (p < 0,05). The relative content of serum albumin (as a percentage of total protein) in eightyear-olds was 51,04 ± 3,12%, which is less than in three-year-olds (72,51 ± 6,04%) (p < 0.01). The serum ALAT activity in eight-year-olds was lower than in three-year-olds (2,33 ± 0,16 and 2,93 ± 0,17 μkat/l, respectively) (p < 0,05). The results of the study of lipid metabolism revealed that serum cholesterol in eight-year-olds (2,62 ± 0,11 mmol/l) is less than in three-year-olds (1,39 ± 0,05) (p < 0,05). However, the serum triglyceride content did not differ between threeyear-olds and eight-year-olds, being 3,50 ± 0,07 and 3,26 ± 0,13 mmol/l, respectively. The glycemic values in three-year-olds and eight-year-olds are significantly different and amount to 1,80 ± 0,08 and 1,42 ± 0,11 mmol/l, respectively (p < 0.05). The results of the study can be used to assess the state of physiological adaptation of the hybrid and to determine the reference values of the parameters of the erythron system and metabolic homeostasis.