Summary: Mutants of 12 strain WGAS-GF/LF were selected for their inability to use fumarate as terminal electron acceptor for supporting growth on glycerol or lactate in an atmosphere of H plus 5% CO. Eighty-three mutants were grouped into seven different categories according to their ability to grow on different media and their ability to produce gas during glucose fermentation. Enzymological and genetic studies indicated that the major class (type I), representing nearly 70% of the isolates, lacked fumarate reductase and corresponded to the mutants studied previously (Spencer & Guest, 1973, 1974). Members of a second class (type II) were phenotypically similar to mutants, blocked in menaquinone biosynthesis. They differed from mutants in having lesions in the 44 to 51 min region of the chromosome rather than at 87 min. It was concluded that fumarate reductase and menaquinone are essential for anaerobic growth when fumarate serves as electron acceptor but not when nitrate performs this function. Fumarate reductase and menaquinone are also essential for H-dependent growth on fumarate. Type III mutants, originally , were designated because they were defective in fumarate and nitrate reduction and impaired in their ability to produce gas. The gene was located at 28·5 min by its cotransducibility with (5·7 to 9·2%) and (2·7 to 5·7%) and the gene order was established. It was not possible to assign specific metabolic lesions to the mutants nor to the remaining classes, which all exhibited pleiotropic phenotypes. Nevertheless, the results demonstrate that functional or organizational relationships exist between the fumarate reductase system, nitrate reduction and hydrogen production.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error