The laser dye rhodamine 123 is shown to be a specific probe for the localization of mitochondria in living cells. By virtue of its selectivity for mitochondria and its fluorescent properties, the detectability of mitochondria stained with rhodamine 123 is significantly improved over that provided by conventional light microscopic techniques. With the use of rhodamine 123, it is possible to detect alterations in mitochondrial distribution following transformation by Rous sarcoma virus and changes in the shape and organization of mitochondria induced by colchicine treatment.

https://www.pnas.org/content/pnas/77/2/990.full.pdf

Localization of mitochondria in living cells with rhodamine 123

Interactions of toxic metals with fungi have long been of importance since metal toxicity still is the basis of many fungicidal preparations while in an environmental context, accelerating pollution of the natural environment has led to increased interest because of the sometimes dominant presence of fungi in metal-polluted habitats, the translocation of toxic metals and radionuclides to fruit bodies of edible higher fungi, and the significance of mycorrhizal fungi in the amelioration of metal phytotoxicity (Colpaert and Van Assche, 1987). Furthermore, the use of fungal (and other microbial) biomass for the detoxification of metal/radionuclide-containing industrial effluents is of biotechnological potential (Gadd, 1990, 1992a).

Interactions of fungip with toxic metals

Organotin compounds are ubiquitous contaminants in the environment. The high biological activity of some compounds toward aquatic organisms lead to deleterious impacts in aquatic ecosystems. Here, the aquatic ecotoxicology of organotins is reviewed based on a multidisciplinary approach involving environmental chemical, toxicological, and ecological aspects. Basic results were obtained both with field and laboratory studies, and some of the most important recent results and conclusions are critically reviewed. The contamination of and fate in aquatic systems is reported and linked with effects at different levels of biological organization. Major emphasis is placed on the development of a concept of ecotoxicology that encompasses not only effect assessment alone, but also integrates environmental chemistry with aquatic toxicology. Thereby, the influence of speciation for bioavailability, basic modes of toxic action, and aquatic toxicity are discussed. This case study on organotins allows to a certain extent generalizations to ecotoxicology in general.

Ecotoxicology of organotin compounds.

Lipids of mitochondria

Regulation of membrane enzymes by lipids

Oligomycin resistance is expressed at the mitochondrial and submitochondrial levels in oligomycin-resistant mutants of Saccharomyces cerevisiae. Studies of the mitochondrial ATPase and Pi-ATP exchange reaction indicate that a modification of the mitochondrial ATPase (ATP-synthetase) complex is involved. The specific resistance at the mitochondrial level to oligomycin and related inhibitors such as ossamycin, rutamycin and peliomycin and the lack of resistance to other inhibitors of mitochondrial ATP synthetase (triethyltin sulphate, venturicidin, aurovertin, Dio-9) correlate with whole cell studies and provide further evidence for a specific modification of an inhibitor site on the mitochondrial inner membrane.



Mitochondrial mutants which map at the OLI and OLII loci can be differentiated biochemically by their sensitivity to oligomycin of mitochondrial ATPase and the pH 9.5/pH 6.5 ATPase activity ratios.



Studies utilising F1-ATPase from wild type and oligomycin-resistant mutants indicate that oligomycin resistance is due to a modification of a membrane-bound component of the mitochondrial ATP-synthetase complex and not to a modification of F1-ATPase or the oligomycin-sensitivity-conferring protein.



Partially purified oligomycin-sensitive ATPase preparations (Triton X-100 extracts) retain the sensitivity (resistance) and specificity of the original membrane-bound system in mitochondria. Purified oligomycin-sensitive ATPase preparations also retain the specificity of the original membrane preparation but the sensitivity to inhibitors is partially modified. The results support the conclusion that oligomycin resistance is due to modification of mitochondrially coded and mitochondrially synthesised subunits of the oligomycin-sensitive ATPase (ATP synthetase) complex. There is no correlation of oligomycin resistance with the ergosterol concentration of yeast cells, yeast mitochondria or mitochondrial ATPase.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1974.tb03608.x

Studies on energy-linked reactions: modified mitochondrial ATPase of oligomycin-resistant mutants of Saccharomyces cerevisiae.

The genetics of the two major phenotypic classes of oligomycin-resistant yeast mutants have been investigated. All the class II mutants (oligomycin specific) tested show typical cytoplasmic inheritance and the determinants appear located on mtDNA. Evidence is presented that this type of resistance can be conferred by at least two distinct groups of nonallelic cytoplasmic determinants. The class I mutants which show cross resistance to a variety of inhibitors and uncouplers of energy conservation reactions exhibit behaviour on genetic analysis which is not fully understood. Tetrad analysis indicates that a nuclear gene is concerned but many anomalous observations, discussed here, suggestive of the involvement of a cytoplasmic element remain to be explained.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1973.tb02611.x

Studies on energy-linked reactions. Genetic analysis of oligomycin-resistant mutants of Saccharomyces cerevisiae.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2877%2980877-6

Studies on energy-linked reactions: inhibition of oxidative phosphorylation and energy-linked reactions by dibutyltin dichloride.

Genetic analysis of venturicidin-resistant mutants has revealed the presence of both nuclear and mitochondrial genes responsible for determining venturicidin sensitivity/resistance in Saccharomyces cerevisiae.



Recombination studies show that the mutation with phenotype VENR is situated at mitochondrial locus OL I and is therefore extremely useful for future genetic manipulations as it gives a unique phenotype to this locus distinguishable from that of the second oligomycin locus OL II.



The mutations with phenotype VENR OLYR are linked to oligomycin locus OL I and have been allocated a new mitochondrial locus, namely OL III.



Three factor crosses involving the venturicidin mutations at loci OL I and OL III have shown them to freely recombine with the other mitochondrial loci R I, R III and OL II. The mitochondrial genetic map is therefore represented as four ‘recombinational linkage groups’.



A fifth linkage group is also specified for mutants with phenotype VENR TETR, and is probably located on a separate DNA molecule from the four other groups.

Studies on energy-linked reactions: genetic analysis of venturicidin-resistant mutants.

The lipid composition of yeast cells was manipulated by the use of an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae. There was a 2-3-fold decrease in the concentration of cytochromes a+a3 when the unsaturated fatty acid content of the cells was decreased from 60-70% of the total fatty acid to 20-30%. The amounts of cytochromes b and c were also decreased under these conditions, but to a lesser extent. Further lipid depletion, to proportions of less than 20% unsaturated fatty acid, led to a dramatic decrease in the content of all cytochromes, particularly cytochromes a+a3. The ATPase (adenosine triphosphatase), succinate oxidase and NADH oxidase activities of the isolated mitochondria also varied with the degree of unsaturation of the membrane lipids. The lower the percentage of unsaturated fatty acid, the lower was the enzymic activity. Inhibition of mitochondrial ATPase by oligomycin, on the other hand, was not markedly influenced by the membrane-lipid unsaturation. Npn-linear Arrenius plots of mitochondrial membrane-bound enzymes showed transition temperatures that were dependent on the degree of membrane-lipid unsaturation. The greater the degree of lipid unsaturation, the lower was the transition temperature. It was concluded that the degree of unsaturation of the membrane lipids plays an important role in determining the properties of mitochondrial membrane-bound enzymes.

/pdf/membrane-lipid-unsaturation-and-mitochondrial-function-in-2fdhlwgetl.pdf

David E. Griffiths

Papers

Studies on energy-linked reactions: modified mitochondrial ATPase of oligomycin-resistant mutants of Saccharomyces cerevisiae.

Studies on energy-linked reactions. Genetic analysis of oligomycin-resistant mutants of Saccharomyces cerevisiae.

Studies on energy-linked reactions: inhibition of oxidative phosphorylation and energy-linked reactions by dibutyltin dichloride.

Studies on energy-linked reactions: genetic analysis of venturicidin-resistant mutants.

Membrane-lipid unsaturation and mitochondrial function in Saacharomyces cerevisiae.