Biotin Production by bioB Transformants of a Bacillus sphaericus Mutant Resistant to 1-(2′-Thenoyl)-3,3,3-trifluoroacetone, an Electron Transport Inhibitor

Bacillus sphaericus DR-1-189[pBHB5022] was found to have an electron transport chain including at least three cytochromes with absorption maxima at 552, 563, and 602 nm, which were reduced by succinic acid, NADH, or NADPH. Electron transport inhibitors such as antimycin A, 3,3′,5′-triiodo-L-thyronine and 1-(2′-thenoyl)-3,3,3-trifluoroacetone (TTFA), blocked this electron transport, with resultant inhibition of cell growth and of biotin synthesis by the cells. When DR-1-189[pBHB5022] was mutagenized to yield mutants resistant to TTFA, the amounts of cytochrome 552 and those of biotin secreted increased in proportion to the extent of resistance of cells to TTFA. A mutant resistant to 250 μg/ml of TTFA produced 48 mg biotin per liter in a medium containing pimelic acid. These results suggest that biotin production by B. sphaericus DR-1-189[pBHB5022] is closely related to its electron transport chain.