Fig. 1.

Lower levels of endogenous intestinal alkaline phosphatase (IAP) reduce bacterial growth. Laparotomy was performed on mice under general anesthesia, a 5-cm loop was constructed, and ∼1,000 colony-forming units (CFU) of a specific bacterial species were instilled by injection (100 μl) into the loop. After 2 h, the loop was dissected out, homogenized, and plated on selective media for overnight growth at 37°C (see materials and methods for details). Bacterial growth in the jejunal loops of wild-type (WT) and IAP-knockout (KO) mice. A: growth of Escherichia coli (n = 10 in each group). B: growth of Morganella morganii (n = 5 in each group). C: growth of Enterococcus faecalis (n = 5 in each group). D: growth of E. coli in the jejunal loop of animals fasted for 14 and 48 h. E: IAP levels in the jejunal loops of animals fasted for 14 and 48 h. Growth of E. coli in the animals treated with phenylalanine (Phe). F: jejunal loop. G: ileal loop. H: colonic loop. I: exogenous IAP (10 U) enhances E. coli growth in the jejunal loop. J: E. coli growth is reduced in the intestinal luminal fluid of IAP-KO mice compared with WT mice. Bacterial growth in the luminal fluid from the proximal small intestine (PSI), distal small intestine (DSI), and colon of IAP-KO mice compared with WT mice. K: growth of E. coli was significantly reduced in DSI luminal fluid of IAP-KO mice compared with WT mice. L: growth of Salmonella typhimurium. Groups of mice were euthanized and the luminal fluid from different segments or the entire intestine of each mouse was collected. Approximately 1,000 CFU of bacteria were added to the fluid and incubated for 2 h at 37°C. Values are expressed as means ± SE. Statistical significance between 2 groups was tested by the 2-tailed Student's t-test. *P < 0.05, **P < 0.01, ***P < 0.001.