Respiratory System of Rhodotorula glutinis I. Inhibitor Tolerance and Cytochrome Components

Stemphylium lotn, a pathogen of a cyanogenc plant, possesses a cyanide-isensitive alternate respiratory pathway. In the absence of cytochrome inhibitors, the alternate system had only a minor role in resption. When S. loi was grown in medium amended with antimycin to block the cytochrome chain, the alternate system accounted for the total oxygen consumption ocited with respiration. Hydrogen cyanide is released from cyanogenic glucosides in birdsfoot trefoil (Lotus corniculatus L.) upon infection by Stemphylium loti (16). This fungus grows in the presence of relatively high concentrations of cyanide in vitro (3) and is more tolerant of cyanide than are other fungi (16). reported that cyanide tolerance in S. loti is induced upon exposure to cyanide and is due to the production of the enzyme formamide hydro-lyase which converts cyanide to nontoxic formamide.We Cyanide-insensitive respiration is generally associated with an unidentified alternate terminal oxidase (ATO) (8) which reportedly connects with the normal electron transport chain at ubiquinone (24). This alternate respiratory pathway coexists with the normal respiratory chain in mitochondria (8). Studies of the normal and alternate respiratory systems have shown the following: (a) antimycin, cyanide, azide, and carbon monoxide, through inhibition of certain Cyt in the normal electron transport chain, inhibit the normal respiratory system but not the alternate pathway (9, 14, 25); (b) salicylhydroxamic acid specifically inhibits the alternate pathway but not the normal pathway (20); and (c) the addition of Cyt inhibitors to a growth medium promotes the appearance of the alternate respiratory pathway in microorganisms such that 100% of the respiration is insensitive to cyanide but is sensitive to SHAM (6,10,12).Our objectives were to determine if S. loti possesses a cyanideinsensitive alternate respiratory pathway and to assess the contribution of such an alternate pathway to growth and to increases in FHL activity. A preliminary report of this work has been published (17). MATERIALS AND METHODS

supporting

confidence: 87%

Contribution of a Cyanide-insensitive Alternate Respiratory System to Increases in Formamide Hydro-lyase Activity and to Growth in Stemphylium loti in Vitro

Rissler¹,

Millar²

1977

“…However, certain respiratory systems such as those of Rhodotorula glutinis (8,9) and Symplocarpus foetidus (skunk cabbage) (12) are insensitive to the antibiotic. Unestam and Gleason (13) showed that following an initial inhibition, antimycin A actually stimulates respiration of mycelia of a Saprolegnia sp.…”

mentioning

confidence: 99%

Antimycin A-resistant respiratory pathway in Ustilago maydis and Neurospora sitophila.

Sherald¹,

Sisler²

1970

Antimycin A inhibits electron transport at a site generally believed to be located between cytochromes b and c (10). However, certain respiratory systems such as those of Rhodotorula glutinis (8,9) and Symplocarpus foetidus (skunk cabbage) (12) are insensitive to the antibiotic. Unestam and Gleason (13) showed that following an initial inhibition, antimycin A actually stimulates respiration of mycelia of a Saprolegnia sp. We have observed a similar phenomenon in conidia of Neurospora sitophila Shear and Dodge, treated with the antibiotic. Respiration of sporidia of Ustilago maydis (DeCandolle) Corda, on the other hand, is not inhibited initially by the antibiotic, but rather is immediately stimulated. A feature which distinguishes the respiration of antimycin A-treated cells of N. sitophila or U. maydis from that of untreated cells is the difference in sensitivity to oxygen tension. This report characterizes the antimycin A effects on respiration of these two fungi and also presents evidence that an alternate terminal oxidase operates in the cells after treatment with the antibiotic.N. sitophila was grown at room temperature on agar medium (2) supplemented with 2 g/liter of yeast extract. Conidia from 4-to 7-day-old cultures were suspended in water or buffer solution (0.02 M phosphate containing 0.5 g/liter of MgSO4-7H20, pH 6.4), filtered through cheesecloth, and washed twice with water or buffer. Sporidia of U. maydis (ATCC 14826) were grown in shake culture at 30 C in a liquid medium of the same nutrient composition used to grow N. sitophila. After 18 to 24 hr, sporidia were centrifuged from the medium and washed twice with buffer solution. Unless otherwise specified, respiratory measurements were made with cells suspended in a glucose-mineral salts solution (pH6.4) supplemented with vitamins (2) Figs. 1 and 2). Conidia of N. sitophila behave similarly, although a small decline in rate of 02 uptake occurs in untreated conidia at 02 levels above 2% saturation (Fig. 3).The terminal oxidase of the rapid, cyanide-resistant respiration of Arum spadix tissue was reported to require a much higher 02 concentration for saturation than the terminal oxidase of the slower, cyanide-sensitive respiration in other tissues of the same plant (5). However, Yocum and Hackett (14) concluded from their studies that at reduced 02 tensions the diffusion rate of 02 through the liquid-suspending medium, rather than a low affinity of the terminal oxidase for 02, limits the respiration rate of aroid spadix tissue.The following evidence indicates that increased sensitivity of respiration of antimycin A-treated cells of N. sitophila and U.

“…Green algae (22), yeast (1), many h'igher plant tissues (14), and animals (1) are also sensitive t'o these inhibitoors. There are, however, groups o'f closely related microorganisms which contain both sensitive and resiistan't species (18,21 found in both plants and animals. Not enough is known albout cytochrome proteins yet for theiir use in the study of evolution and phylogeny in the algae and in most groups o,f funigi.…”

Section: Discussionmentioning

confidence: 99%

Respiratory Electron Transport Systems of Aquatic Fungi. I. Leptomitus lacteus and Apodachlya punctata

Gleason

1968

Abstract. The electron transport systems of 2 species of aquatic fungi, Leptomitus lacteus and Apodachlya punctata, contained cytochrome a-a3 (605 m,u), 2 b type cytochromes (564 and 557 mju), c type cytochrome (551 mg), and flavoprotein, but they appeared to lack cytochrome c.. Reduced-minus-oxidized difference spectra and difference spectra in the presence of antimycin A or cyanide were used to characterize these systems. Studies with the electron microscope revealed that hyphae of Leptomitus lacteus contained numerous, oonspicuous mitochondria with tubular cristae.