title: Stimulatory effect of phosphate on colicin V synthesis/secretion by strains of Escherichia coli.
abstract: Larger inhibitory zones were produced by ColV+ strains on sensitive indicators if the strains were grown on nutrient agar and phosphate rather than nutrient agar. This was due to an effect of phosphate on colicin V synthesis/secretion and not to an effect on the response of the indicator. Phosphate produced an effect at 25 degrees C as well as at 37 degrees C (although zones were larger at 37 degrees C). It seems likely that phosphate stimulation of colicin V synthesis/secretion results from its effect in reducing divalent cation levels in NA because adding EDTA to NA also increased colicin V synthesis/secretion whereas the addition of magnesium or calcium salts had the opposite effect. It is possible that the extent of colicin V synthesis/secretion may depend on the strength of the LPS-LPS bonds in the outer membrane. Phosphate also stimulated synthesis/secretion of colicins E4, G and N but not of the other colicins or microcins tested. Studies with a wild Col+ E. coli isolate suggest that production of some colicins may not be detected on nutrient agar and that addition of phosphate may reveal the synthesis of new colicins.
mesh_terms: D002118:Calcium / Q000494:pharmacology; D003087:Colicins / Q000096:biosynthesis*; D003470:Culture Media; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D010710:Phosphates / Q000494:pharmacology*
chemical_list: D003087:Colicins; D003470:Culture Media; D008070:Lipopolysaccharides; D010710:Phosphates; D004492:Edetic Acid; D008274:Magnesium; D002118:Calcium