Bartnicki-Garcia, S. (Rutgers, The State University, New Brunswick, N.J.) and Walter J. Nickerson. Nutrition, growth, and morphogenesis of Mucor rouxii. J. Bacteriol. 84:841-858. 1962.-Mucor rouxii was grown under three different atmospheres of incubation: air, N(2), and CO(2) in parallel cultures. The atmosphere of incubation markedly affected nutritional requirements, growth, and morphogenesis. Absence of oxygen greatly reduced growth and increased the nutritional demands of the fungus. Presence of a high tension of CO(2) resulted in a change from filamentous to yeastlike morphogenesis. Aerobically, a large variety of carbon sources was utilized; anaerobically, only hexoses served to meet requirements for carbon and energy. Aerobically, various amino acids supported abundant growth; anaerobically, they were poorly utilized. Ammonium and nitrate ions were better sources of nitrogen for anaerobic growth. In general, incubation under either air or N(2) resulted in development of coenocytic filamentous mycelium, whereas incubation under CO(2) resulted in development of budding yeastlike cells. Variations in temperature and time of incubation, inoculum size, type and concentration of carbon source, type of nitrogen source, and presence of various substances with known action on fungal morphogenesis altered growth in many cases, but did not significantly affect the patterns of vegetative morphogenesis conditioned by each atmosphere of incubation. However, vegetative morphogenesis was strongly affected by addition of certain chelating agents. Yeastlike development of M. rouxii was prevented by ethylene-diaminetetraacetic acid (EDTA) in concentrations which were also partially inhibitory for growth; under these conditions, development was filamentous. Chemically related chelating agents were similarly active. The growth-inhibitory and morphogenetic effects of EDTA were reversed by transition-group metal ions. Yeastlike development of M. subtilissimus, which does not require CO(2) for its induction, was also inhibited by EDTA.

Nutrition, growth, and morphogenesis of mucor rouxii

Nutritional control of dimorphism inCeratocystis ulmi

The interconversions of mycelial and yeast-like forms (M ⇌ Y) in Blastomyces dermatitidis and in Blastomyces brasiliensis are characterized as examples of thermal dimorphism since the phenomena are apparently dependent only on the temperature of incubation of these two species. The change in morphology consequent upon Y → M conversion is considered to result from the selective inhibition of cell division, without the simultaneous inhibition of growth. Such selective inhibition is viewed in a wider context as an example of the differential operation of the physicochemical apparatus of the cell in the control of form development by an organism. To analyze this differential operation, which is here dependent only on temperature, we have studied the effect of temperature on oxygen consumption by each of the dimorphic forms. In the absence of external substrate the yeast forms consume 5 to 6 times more oxygen per unit dry weight than do the M forms.The Y forms exhibit an exogenous oxidation of acetate and of glucose, as well as an oxidative assimilation of these substrates, whereas the M forms exhibit no exogenous metabolism in either a resting or starved condition. A study of the effect of a wide range of temperatures on oxygen consumption by the M forms indicates the operation of two rate-limiting processes: (a) one with an activation energy of 13,250 calories/gm. molecule over the range 5–30°, and (b) reversible enzyme inactivation; the latter process assuming importance in the higher temperature range. On abrupt, large changes in temperature the balance between these two rate-limiting reactions (which it is suggested characterizes the steady state) is apparently disrupted as a result of a lag in the assumption of a rate of reversible enzyme inactivation characteristic of the new temperature. This disruption of balance is evidenced in overshoot phenomena. The effect of an analogous disruption of balance, and of increasing enzymic inactivation; on a competition between enzyme systems, competing for substrate for cell elongation and for cell division, is considered in explanation of the observed dependence of the cell division mechanism on the maintenance of an elevated temperature.

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Studies on the physiological bases of morphogenesis in fungi i. the respiratory metabolism of dimorphic pathogenic fungi

https://mmbr.asm.org/content/mmbr/17/1/51.full.pdf

The dimorphism phenomenon in yeasts

FROM lines of evidence converging from apparently widely separated fields it now appears possible to assemble evidence indicating that cell division in micro-organisms, and probably also in other organisms, is under the control of a unit enzymatic mechanism. The lines of investigation, developed quite independently, forming the foundations for this thesis are : (1) physico-chemical studies by Hinshelwood and co-workers1 on the kinetics of bacterial growth and the state of balance between division and elongation ; (2) the studies of Witkin2 (genetic), Eisenstark and Clark3 (electron microscope), and others20,21,22 on irradiated bacteria ; (3) cytochemical investigations of Pratt and Dufrenoy4 on the mode of action of penicillin ; (4) metabolic studies on dimorphic pathogenic fungi by Nickerson and Edwards5 ; and (5) examination of the chemical control of morphogenesis in yeasts by Jillson and Nickerson6, the common denominator in all of these lines of investigation being a close examination of the effects of inimical or critical conditions on the morphogenesis of dividing cells. The examinations have revealed a common fundamental attribute of cell division of micro-organisms.

Enzymatic control of cell division in micro-organisms.

Blastomyces dermatitidis possesses two morphological forms, a yeastlike form in tissue and a mycelial form on Saboraud's medium at room temperature. A yeastlike form similar to the form appearing in tissue may be obtained if the organism is grown on blood agar at 37 C. An extensive literature has developed around blastomycosis as a clinical entity, but only a small proportion of the papers have been concerned with the biological nature of the etiological agent, Blastomyces dermatitidis. Ricketts (1901) described the two morphological forms. Hamburger (1907) concluded that temperature was the most important factor influencing morphology, and that room temperature favored mycelial formation, but incubator temperatures favored the yeastlike form. He did not determine the effect of intermediate temperature or of hydrogen ion concentration. Michelson (1928) studied the effect of higher temperatures and noted that temperatures of 37, 41, and 45 C favored the growth of the yeastlike form. Moore (1933) studied the organism for the purpose of determining its position in botanical classification. He studied its growth in media of different hydrogen ion concentrations, but each hydrogen ion concentration was represented by a different medium. The purpose of the present study was to determine the effect of various controlled changes in the environment, such as nutrition, hydrogen ion concentration, temperature, and type of inoculum on the two morphological forms of Blastomyces dermatitidis.

Factors Influencing the Morphology of Blastomyces dermatitidis.

Blastomyces dermatitidis, a fungus pathogenic for man, exists in two morphological forms, a yeastlike form in tissue and at 37 C, and a mycelial form at room temperature. Bernheim (1942) reported that acetate stimulated the oxygen uptake of this organism, but the higher members of the fatty acid series, palmitate, stearate, and oleate, inhibited oxygen uptake. In view of the increased interest in the fatty acids as fungistatic agents, it seemed desirable to investigate further the effect of fatty acids on the respiration of Blastomyces dermatitidis. The present study was undertaken to determine the effect of the structure and

The effect of fatty acids on the oxygen uptake of blastomyces dermatitidis.

The procedures used for the growth and preparation of the cell suspension were identical with those described by Levine and Novak (1950). For this study the following buffers were used in a final concentration of M/60: phthalate buffer, pH 2, 3, 4, and 5; phosphate buffer, pH 6, 7, and 8; and borate buffer, pH 9 and 10. Before any of the experiments were performed, a series of vessels were set up to determine the effect of M/60 final concentration of phthalate and borate on the respiration of B. dermatitidis. The phthalate and borate were added to phosphate buffer of pH 6.0. The results are shown in table 1. As can be seen, phthalate has very little, if any, effect on oxygen uptake. Borate is definitely inhibitory, so that any conclusions drawn from its use will have to take into account this inhibitory action.

Studies on the metabolism of Blastomyces dermatitidis. II. The effect of pH on respiration.

The fungi causing the deep mycotic infections of man represent an extremely interesting group of microorganisms. Among them there are several species, notably Blaatomyces dermatitidis and Histoplasma capsulatum, possessing a diphasic morphology. In tissue and on culture media at 37 C they exhibit a yeastlike form. On culture media at room temperature they grow in a filamentous phase. Bermheim (1942) studied the oxidative metabolism of the yeast phase of B. dermatitidis. The effect of various substances upon the oxygen uptake of this organism was determined at pH 6.7 with unstarved cells. He observed that glucose, mannose, pyruvate, and lactate were oxidized, whereas arabinose, rhamnose, and fructose were not. Acetate was oxidized. The higher fatty acids, oleate, palmitate, and stearate inhibited endogenous respiration and also the oxidation of added glucose, pyruvate, lactate, and acetate. Succinic acid was slowly oxidized, the oxidation being inhibited by malonate. Fumaric acid did not act catalytically, nor did citric acid, which was not oxidized. Sodium cyanide completely inhibited the oxidation of all added substances. Bernheim also studied the effects of aldehydes and amino acids on the respiration of B. dermatitidis. In a previous paper (1949) we reported the results of the effect of a homologous series of fatty acids on the respiration of B. dermatitidis. In the present paper we shall report on the results of a study to determine the effect of various substances on the respiration of this organism.

Seymour Levine

Papers

Factors Influencing the Morphology of Blastomyces dermatitidis.

The effect of fatty acids on the oxygen uptake of blastomyces dermatitidis.

Studies on the metabolism of Blastomyces dermatitidis. II. The effect of pH on respiration.

Studies on the metabolism of Blastomyces dermatitidis. I. The effect of various substances on respiration.