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Appl. Environ. Microbiol., Feb 1996, 372-379, Vol 62, No. 2
HF Valentin and D Dennis
The gene encoding the large subunit of the methylmalonyl-coenzyme A (CoA)
mutase in Nocardia corallina (mutBNc) was cloned. A 4.3-kbp BamHI fragment
containing almost the entire mutBNc was identified by Southern
hybridization experiments employing a digoxigenin-labeled probe deduced
from mutB of Streptomyces cinnamonensis, mutBNc was interrupted by
insertion of a kanamycin resistance gene block (mutB::kan or mutB::neo) and
introduced into N. corallina to obtain mutB-negative strains by homologous
recombination. Four of sixteen kanamycin-resistant clones occurred via
double-crossover events and harbored only the interrupted mutBNc. These
exhibited no growth on odd-chain fatty acids in the presence of kanamycin
but exhibited wild-type growth on even-chain fatty acids, glucose, and
succinate. Whereas the wild type of N. corallina accumulates a copolyester
of 3-hydroxybutyrate (3HB) and 3- hydroxyvalerate (3HV) containing more
than 60 mol% 3HV from most carbon sources, mutB-negative strains
accumulated poly(3HB-co-3HV) containing only 2 to 6 mol% 3HV.
Methylmalonyl-CoA mutase activity was not found in these clones. Therefore,
this study provides strong evidence that the majority of 3HV units in
poly(3HB-co-3HV) accumulated by N. corallina are synthesized via the
methylmalonyl-CoA pathway.
Copyright © 1996, American Society for Microbiology
Metabolic pathway for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) formation in Nocardia corallina: inactivation of mutB by chromosomal integration of a kanamycin resistance gene
Department of Biology, James Madison University, Harrisonburg, Virginia 22807, USA. Valenthe@vaxl.acs.jmu.cdu
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