Date of Award


Publication Type

Doctoral Thesis

Degree Name



Biological Sciences


Biology, Microbiology.




The effect of cytochalasins, a group of fungal metabolites, on the respiration of bacteria and fungi was investigated. Among several cytochalasins used only cytochalasin A (CA), a thiol-blocking reagent, inhibited respiration of certain bacteria and fungi at low concentrations. Thirteen bacterial species (5 gram positives and 8 gram negatives) were tested for CA-inhibition of respiration. All the gram negative organisms used were CA-resistant whereas the gram positive organisms were susceptible. The CA-inhibition of respiration in gram positive bacteria was rapid, concentration dependent and generally reversible by washing, except in Bacillus subtilis, and not mediated via inhibition of substrate transport. The CA-susceptibility of bacteria was related to their permeability to this compound. Gram negative organisms which were resistant had low CA-permeability whereas susceptible gram positive organisms possessed high permeability. CA-resistant gram negative bacteria became CA-susceptible and CA-permeable when their permeability was modified with EDTA-treatment. Among various fungi from 6 phylogenetic groups examined only Oomycetes and Chytridiomycetes were susceptible to CA-inhibition of respiration. Except in Basidiomycetes CA-susceptibility was correlated with CA-permeation into the cells. Experiments with Achlya ambisexualis, a typical Oomycetous fungus, indicated that CA-inhibition of respiration in this fungus was rapid, concentration dependent, irreversible and not mediated by inhibition of substrate transport. Although Achlya mitochondria in vitro respired the TCA-cycle intermediates pyruvate, alpha-ketoglutarate and succinate with good acceptor control ratios, CA inhibited only pyruvate oxidation. In contrast to the irreversible CA-action in intact systems, inhibition of pyruvate oxidation by isolated mitochondria was reversible by washing. Both in bacteria and in fungi CA acts as a thiol-blocking reagent. This thiol-blocking property of CA is the key to its effectiveness as a respiratory inhibitor. The selective action of CA as a respiratory inhibitor is mainly responsible for its bacteriostatic and fungistatic properties in susceptible organisms.Dept. of Biological Sciences. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1981 .M252. Source: Dissertation Abstracts International, Volume: 42-03, Section: B, page: 0917. Thesis (Ph.D.)--University of Windsor (Canada), 1981.