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J Bacteriol. 1965 February; 89(2): 271-276
Copyright © 1965 American Society for Microbiology. All Rights Reserved.

Electron Transport in Bacillus popilliae¹

^a Department of Microbiology and Public Health, Michigan State University, East Lansing, Michigan

ABSTRACT

PEPPER, ROLLIN E. (Michigan State University, East Lansing), AND RALPH N. COSTILOW. Electron transport in Bacillus popilliae. J. Bacteriol. 89:271–276. 1965.—Bacillus popilliae was found to be unique among aerobic microorganisms in that it was deficient in a hydrogen peroxide-scavenging system. Neither catalase nor peroxidase was found. At the same time, a system for producing hydrogen peroxide during oxidation of reduced nicotinamide adenine dinucleotide (NADH₂) was consistently present in the soluble fraction of extracts of cells from older cultures. Cells harvested from 9-hr cultures did not produce a significant amount of peroxide. The soluble NADH₂ oxidase was apparently a flavoprotein, since it was stimulated by flavin nucleotides, insensitive to cyanide and azide, and inhibited by Atabrine. Also, difference spectra demonstrated the presence of a reducible flavin in the soluble fraction of cell extracts. The particulate fraction of cell extracts was shown by difference spectra to contain cytochrome b₁; the strong inhibition of NADH₂ oxidation by cyanide, azide, and carbon monoxide indicated that a terminal cytochrome oxidase was also present. This system was also flavin-dependent, since it was strongly inhibited by Atabrine. The specific activity of the NADH₂ oxidase in the particulate fraction was lower in extracts of cells from older cultures than in those from exponentially growing cultures. Cytochrome c was not found in extracts of these cells. It is believed that the increased participation of the hydrogen peroxide-generating NADH₂ oxidase in cells of older cultures may be responsible for the rapid loss in cell viability noted in stationary-phase cultures.

² Present address: Department of Biology, Elizabethtown College, Elizabethtown, Pa.

¹ Journal article no. 3425, Michigan Agricultural Experiment Station.