Summary: Fifteen independent menaquinone biosynthesis mutants () of K12, selected for their inability to use fumarate as terminal electron acceptor, were investigated. Two nutritionally distinct groups were detected. The major group (13 mutants) responded to 1,4-dihydroxy-2-naphthoate (DHN), 2-succinylbenzoate (SB) and its dilactone, whereas the minor group (2 mutants) only responded to DHN. DHN was at least five times more effective than SB but it inhibited growth at concentrations greater than 10 μ. For anaerobic growth on glucose minimal medium the auxotrophs responded to much lower concentrations of DHN and SB and these intermediates could be replaced by uracil. Anaerobic growth tests showed that glycerol, formate and H are good substrates for when fumarate is the ultimate electron acceptor but growth with lactate or with fumarate alone is poor.

All 15 mutations were located between and at approximately 49 min in the linkage map. Cotransduction frequencies with relevant markers were: (21%), (35%) and (15%). The presence of at least three genetically distinct classes ( and , SB-requirers; , DHN-requirers) was indicated using abortive transduction as a complementation test and three-factor genetic analysis. The relative orientation was indicated.

Fluoroacetate-resistant mutants were isolated and four different classes were identified: , lacking acetate kinase; , lacking phosphotransacetylase; , lacking both of these activities; and , which retained both of these enzyme activities. Some of the mutants and all of the mutants failed to grow on media containing fumarate as terminal electron acceptor or anaerobically on glucose minimal medium. All four types had genetic lesions clustered between the and sites. Average cotransduction frequencies with relevant markers were: (4%), (27 to 35%) and (71 to 80%).


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