Tolerance of yeasts to zinc: distinction between cell growth and cell longevity

Torulopsis homii and several other yeasts grew well in a synthetic medium containing 1.0 μmolar zinc. Additional zinc increased neither the growth rate nor total growth. In concentrations up to 10 μmolar, essentially 100% of the zinc added to a culture of T. homii was accumulated during growth by the cells; soon after reaching the stationary phase, most of the metal was eliminated into the medium in the ionic state. The release of zinc was correlated with the lowering of the pH of the medium by the fermentation products.In contrast to the lack of effect on growth, the concentration of zinc markedly influenced the viability of yeast cultures. The presence of 10 to 100 μmolar zinc at the time of inoculation greatly increased the death rate of stationary phase cultures. Likewise, subfungistatic concentrations of cadmium or copper, but not iron or manganese, decreased culture longevity. This action of zinc, cadmium, and copper is attributed to the ability of these metals to suppress fungal secondary metabolism.

The effect of carbon source on trap formation by Arthrobotrys conoides

The nematode-trapping fungus Arthrobotrys conoides grows as typical vegetative hyphae on laboratory media containing glucose or starch as sole carbon source. However, in the presence of nematodes, "nemin", and several of the aliphatic amino acids (such as valine), this predacious fungus forms traps which are composed of sticky loops. The present studies show that, when A. conoides is grown on a semisynthetic medium in which various carbohydrates are substituted for glucose as the carbon source available for growth, the nature of the carbohydrate exerts a major effect on the induction of trap formation.

Influence of antifungal vapors on spore germination of fungi isolated from deteriorated old books

Studies of the effect of antifungal vapors of p-chloro-m-cresol, pentachlorophenol, mercuric chloride, and phenyl mercuric acetate on spore germination of fungi isolated from deteriorated old books snowed variation in the reaction of different fungi to fungicides. In general, minimal doses were stimulatory to germination while higher concentrations were either sporostatic or sporocidal. Phenyl mercuric acetate was found to be most effective, exerting a sporocidal action even at a concentration of 0.1 p.p.m. Lower concentrations of this compound usually inhibited spore germination or induced formation of hyphal monstrosities.

Formation of endospores in Verticillium albo-atrum (R. & B.)

A morphological study of a hyaline strain of Verticillium albo-atrum (R. & B.) has revealed that spores are produced intrahyphally. Some implications of this finding are briefly discussed.

The mechanism of action of griseofulvin

Griseofulvin had no effect on the respiration of Botrytis cinerea but, nevertheless, inhibited growth and caused abnormal hyphal formations, including stunting, spiraling, thickening of the cell wall, and disorientation of growth. Treated cells had an increase in total deoxyribonucleic acid and phosphorus but not in protein, carbohydrate, lipid, and ribonucleic acid. Griseofulvin-treated cells synthesized DNA from labelled glucose and glycine continuously and for much longer periods than control cells so that their total DNA content was greater than that in untreated cells. However, the antibiotic allowed slightly less incorporation with aspartic acid -U-14C as the precursor than the controls. Griseofulvin caused 25 to 50% increased incorporation of carbon into RNA from glucose and glycine but the increases were not due to a prolongation of the synthetic period, and again aspartic acid incorporation was slightly decreased. Griseofulvin was bound to the particulate parts of the cell and was especially high in the lipid fraction of the cell. The antibiotic was not bound to DNA or to RNA.

Attempts to detect lycopersene formation in yeast

1. beta-Ionone vapour has been shown to cause an increase in the more saturated carotenes and a decrease in the less saturated carotenes of Rhodotorula glutinis. Lycopersene (dihydrophytoene) has been proposed as a precursor to phytoene. Attempts were made to isolate lycopersene from beta-ionone-treated cultures of R. glutinis. 2. Large samples of beta-ionone-treated cultures were examined for the presence of lycopersene. Spots were detected on silicic acid plates that could not be differentiated from synthetic lycopersene on the basis of column and thin-layer chromatographic separations and staining techniques. The lycopersene-like substance could be obtained from non-treated pigmented yeast as well as baker's yeast. 3. An extraction of bacterial-grade yeast extract also yielded a lycopersene-like substance. The extracts of R. glutinis cells cultured on media not containing yeast extract did not contain the lycopersene-like compound. 4. No significant carbon was incorporated into the lycopersene zone from (14)C-labelled mevalonate, acetate and glucose by R. glutinis and baker's yeast. 5. These results indicate that compounds may exist with chromatographic properties similar to lycopersene, but that lycopersene could not be detected in either a pigmented or a non-pigmented yeast.

Effect of atrazine on growth response of Sclerotium rolfsii and Trichoderma viride

The effect of atrazine (2-chloro-4-ethylamino-6-isopropylamino-.s-triazine) on growth of Sclerotium rolfsii and Trichoderma viride was studied in liquid culture. The fungi were grown in Czapek solution containing 0, 8, 20, 40, and 80 μg of the herbicide per milliliter, and growth responses were measured at intervals of 3–5 days after inoculation. Mycelial dry weight of S. rolfsii was little affected at concentrations below 40 μg/ml, but was decreased at the higher concentrations. Total mycelium produced by T. viride was greater with all atrazine treatments than in the control. For S. rolfsii, the efficiency of utilization (economic coefficient) of glucose, inorganic P, and NO3-N with atrazine at 8 μg/ml was slightly higher than that of the control, but was significantly reduced at higher concentrations. Values for glucose utilization efficiency in T. viride increased with herbicide at 8 and 20 μg/ml, then decreased considerably at other concentrations, but remained higher than the control; a similar pattern was revealed for P and NO3-N utilization. Titratable acidity in the medium increased for both fungi with increased atrazine concentration.

The carbon and nitrogen nutrition of certain fungi

Carbon nutrition of Chaetomium sp., Myrothecium verrucaria, Pestalotia gracilis, and Pleurotus ostreatus was studied. Nitrogen nutrition was also examined with Nigrospora oryzae included. The effect of C/N ratio on fruiting was measured for the first four fungi. Several carbon sources including alcohols, carbohydrates, and organic acids were tested; in general, dextrin and L-arabinose were the most favorable for growth, starch was less so, whereas sodium acetate and sodium citrate were the least favorable. Maltose supported good sporulation of M. verrucaria, P. gracilis, and P. ostreatus. Organic nitrogen was superior to inorganic nitrogen for growth of M. verrucaria, N. oryzae, and P. ostreatus. The opposite was noticed for Chaetomium sp. and P. gracilis. Not all could grow on sodium nitrite at the concentration used nor sporulate on DL-methionine or ammonium sulfate. The best sporulation of P. gracilis was obtained with the maximum glucose and nitrate concentrations used (4% and 1% respectively), whereas the minimum concentrations (0.1 and 0.05% respectively) were best for the sporulation of P. ostreatus. Chaetomium sp. and M. verrucaria fruited best on intermediate concentrations of glucose and nitrate.

Electrical sensing zone particle analyzer for measuring germination of fungal spores in the presence of other particles

Microscopic, respirometric, and electronic sizing methods for measuring germination of fungal spores were compared. With the electronic sizing method, early stages of germination (i.e., spore swelling) were detected long before germ tube emergence or significant changes in respiratory rates were observed. This method, which is rapid, easy, sensitive, and reproducible, also permits measuring the germination of spores when similar-size particles are present in concentrations considerably in excess of the number of spores.

Effect of abrupt temperature shift on the growth of mesophilic and psychrophilic yeasts

Exponentially growing cultures of mesophilic and psychrophilic yeasts were subjected to abrupt changes in temperature. Temperature shifts made within the range in which the temperature characteristic, mu, is relatively constant (moderate temperatures) immediately induced growth at the normal exponential rate for the new temperature. Prior incubation at temperatures defined as moderate enabled some yeasts to grow for a few generations at temperatures higher than their normal maximal temperature for growth. Shifts made to or from temperatures above or below those in the moderate temperature range resulted in growth rates that were intermediate between the normal steady-state rates for the initial and final temperatures. A period of transient growth rate at the new temperature outside the moderate temperature range seems to be required before normal steady-state growth rates can be attained after such temperature shifts. The psychrophiles gave transient growth rates only below 10 C, whereas the mesophiles gave transient rates below 20 C. However, the psychrophiles cannot be distinguished from the mesophiles on the basis of the temperature characteristic, mu, which was found to be about 12,000 cal/mole for both types.