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151.
152.
Burkholderia cepacia is an opportunistic pathogen that causes serious pulmonary infections in cystic fibrosis patients. We have purified and partially
characterized one potential virulence factor for the organism—a nonhemolytic phospholipase C—and we studied the effect of
iron restriction and choline and phosphate concentrations on the expression of phospholipase C. Iron limitation did not affect
expression, the effect of choline was variable, and high phosphate concentrations repressed expression. Experiments with heat-treated
spent culture supernatants suggested that autoinducers affected the expression of the phospholipase and two other potential
virulence factors, a protease and a lipase. We screened 26 B. cepacia isolates for autoinducer activity: 11 induced violacein production in the autoinducer-deficient mutant Chromobacterium violaceum CV026. Spent supernatants from two strains, one that was positive in the C. violaceum assay and one that was negative, were tested for inducing early expression of phospholipase C, protease, and lipase in homologous
and heterologous cultures. Expression of all three enzymes was increased or induced at an earlier stage in the growth curve
in every case, suggesting not only that autoinducers were involved in the regulation of the expression of these enzymes, but
also that the autoinducers were of two different classes.
Received: 13 May 1999 / Accepted: 14 June 1999 相似文献
153.