Isolation and phenotypic characterization of Pseudomonas aeruginosa pseudorevertants containing suppressors of the catabolite repression control-defective crc-10 allele

The amiE gene encodes an aliphatic amidase capable of converting fluoroacet amide to the toxic compound fluoroacetate and is one of many genes whose ex pression is subject to catabolite repression control in Pseudomonas aerugin osa. The protein product of the cre gene, Crc, is required for repression o f amiE and most other genes subject to catabolite repression control in thi s bacterium. When grown in a carbon source such as succinate, wild-type P. aeruginosa is insensitive to fluoroacetamide (due to repression of amiE exp ression). In contrast, mutants harboring the crc-10 null allele cannot grow in the presence of fluoroacetamide (due to lack of repression of amiE). Se lection for succinate-dependent, fluoroacetamide-resistant derivatives of t he crc-10 mutant yielded three independent pseudorevertants containing supp ressors that restored a degree of catabolite repression control. Synthesis of Crc protein was not reestablished in these pseudorevertants. All three s uppressors of crc-10 were extragenic, and all three also suppressed a Delta crc::tetA allele. In each of the three pseudorevertants, catabolite repres sion control of amidase expression was restored. Catabolite repression cont rol of mannitol dehydrogenase production was also restored in two of the th ree isolates. None of the suppressors restored repression of glucose-6-phos phate dehydrogenase or pyocyanin production. (C) 2001 Federation of Europea n Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.