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Abstract
Respiratory quinones and the ability to use fumarate as a terminal electron acceptor in anaerobic respiration were investigated in 49 bacterial strains representing a variety of conventional Flavobacterium or Cytophaga species. The organisms examined were subdivided into two categories according to their quinones. (i) Ubiquinones are used by the neotype strain of Flavobacterium aquatile and by cultures representing F. acidificum, F. capsulatum, F. devorans, F. halmephilum, and some unnamed Flavobacterium species. (ii) Menaquinones are produced by both typical Cytophaga strains and many so-called Flavobacterium or “Flavobacterium/Cytophaga” cultures. Several members of category ii exhibited low to medium reduced nicotinamide adenine dinucleotide-fumarate reductase activities when grown in unaerated complex media supplemented with fumarate. In addition, with F. meningosepticum, “group IIb” organisms, and a strain of F. odoratum, the yields of oxygen-limited growth were markedly increased by fumarate, indicating an energetic use of fumarate respiration. On the basis of these findings, restriction of the genus Flavobacterium to “low-guanine-plus-cytosine” organisms containing ubiquinones and resembling F. aquatile is proposed. The incorporation of some former “flavobacteria” into a natural group of organisms containing menaquinones and placement in the vicinity of the C. hutchinsonii guanine-plus-cytosine ratio are discussed.
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