Stb Genes Research Articles

Species specificity and lack of production of STb enterotoxin by Escherichia coli strains isolated from humans with diarrheal illness.

Escherichia coli strains produce at least two heat-stable enterotoxins, STa and STb. STa is well known to be important in the pathogenesis of human diarrheal disease; the role of STb has not been defined. Fifty-two E. coli strains recovered from human diarrheal illness in northeast Brazil or Bangladesh were examined in weaned porcine ligated intestinal segments for STb activity. A total of 113 E. coli strains from human diarrheal disease in northeast Brazil and 28 E. coli strains from Bangladesh were examined for DNA hybridization to a STb gene probe. None of these strains produced STb as detected by enterotoxic activity or by the gene probe. We also examined adult human ileal mucosa for responses to STb in the Ussing chamber in vitro. In contrast to piglet jejunum, which consistently responds electrogenically to crude STb, human ileal tissue showed no response to STb but responded electrogenically to theophylline (10 mM). These results suggest that STb-producing E. coli strains are not a major cause of diarrheal illness in humans.

Inheritance of High Lysine in Hiproly Barley and Its Association with the Hiproly Endosperm Gene1

A recombination of 22.45% between the major high lysine gene and a single gene for starch binding in the endosperm (stb) was found in the barley (Hordeum vulgare L.) variety ‘Hiproly.’ This association was found by using a microscopic technique to identify the stb gene and a micro Udy‐Dye binding method to identify the high lysine gene. Both genes give a dosage effect in the 3n endosperm.