title: Some effects of temperature on the growth of F pili.
abstract: The effect of temperature on the production of F pili by an F(+) strain of Escherichia coli B/r was studied by electron microscopy and by a technique involving serum-blocking power. The latter method is based on the ability of F pili to adsorb F pili antibody which inhibits male-specific phage infection. The total amount of pili in a sample was estimated by serum-blocking power; the length of F pili and number per cell was determined by electron microscopy. Cell extracts prepared by sonic oscillation lacked serum-blocking power, suggesting that F pili are not present in the cytoplasm. The number of F pili per cell varied with the growth temperature, but the average length of F pili remained constant. Maximum number of pili per cell occurs between 37 and 42 C; below 37 C the number decreases, reaching zero at about 25 C. When cells are grown at 37 C, blended, and resuspended in fresh media at 25 C, they make F pili. These pili are probably assembled from a pool of subunits that were synthesized during growth at 37 C. The rates of assembly at 25 and 37 C, as judged by the rate of increase in length of F pili, are similar. When cells were grown at 25 C and shifted up to 37 C, there was a 30-min lag in pili production followed by a period of rapid outgrowth. When cells were shifted down from 37 to 20 C, outgrowth (assembly) of pili ceased, and approximately 50% of the attached pili were released in 2 min. No release was observed when cells were shifted to 0 C. This suggests that pili may be released from the cell by a mechanism that requires metabolic activity, but not the outgrowth of F pili.
mesh_terms: D000327:Adsorption; D000372:Agglutination Tests; D000818:Animals; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D002586:Cesium; D002712:Chlorides; D003090:Coliphages; D003227:Conjugation, Genetic; D003470:Culture Media; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000166:cytology / Q000254:growth & development / Q000276:immunology; D005827:Genetics, Microbial; D007106:Immune Sera; D008854:Microscopy, Electron; D010772:Phosphotungstic Acid; D011817:Rabbits; D013194:Staining and Labeling; D013696:Temperature; D014465:Ultrasonics; D014732:Vibration
chemical_list: D002712:Chlorides; D003470:Culture Media; D004269:DNA, Bacterial; D007106:Immune Sera; D010772:Phosphotungstic Acid; D002586:Cesium