Biotin defiency in Bacillus megaterium.

Morphological deformity of Bacillus megaterium NCIB758I grown at 37 "C ina minimal chemically defined medium could be prevented by addition of either biotin, aspartate or acetate (Al-ssum & White, 1977). The only carbon source in the minimal medium was glycerol or glucose, and the metabolism of either of these two substrates requires an adequate conversion of C, compounds [e.g.pyruvate or phosphoenolpyruvate(PEP)] to C, compounds anaplerotically, to replace citric acid cycle intermediates that are withdrawn for biosynthesis. Such conversion occurs in bacteria mainly by the action of a C0,-fixing enzyme, either the biotin-dependent pyruvate carboxylase, or the biotinindependent PEP carboxylase; generally, organisms have one or other (not both) of these enzymes (Kornberg, I 966). Anaplerotic synthesis of C, compounds could also occur independently of C0,-fixing enzymes by the operation of the glyoxylate cycle. Another biotinrequiring enzyme is acetyl coenzyme A carboxylase, which catalyses the ATP-dependent carboxylation of acetyl-CoA to yield malonyl-CoA (see review by Vagelos, I 964). In biotindeficient organisms, the activity of this enzyme might be lowered, so that synthesis of fatty acids (via malonyl-CoA) might be impaired. The nutritional evidence suggests that in B. megaterium N C I B z ~a~n ~ac tive pyruvate carboxylase is necessary unless a source of C, compounds (e.g. aspartate) is available or unless the glyoxylate cycle is functioning. In this paper, activities of three anaplerotic enzymes and of acetyl-CoA carboxylase and malic enzyme are compared in organisms grown with and without biotin. A preliminary report of some of these results has been mad