Some aspects are described of tlie kinetics of the groivth of (;ibbeie!la fzljik~~ro?:in nitrogen-limited media contai~ling either am~uonium nitrate, ammonium acetate, ammonium tartl-ate, urea, or glycine. Also varied were inoculum size, agitation rate, pI-I, and initial concentrations of glucosc and nitrogen source. The sigiiihcance of kinetic parameters ~lsed in this, and published studies, is discussed.A lag phase n:as only found on ammonium acetate media or when higli concentrations of glucose \\,ere present. Early gro\vth was exponei~tial on all nitrogen sources. On ammonium acetate the specilic growth rate decreased a t a dry weight ofca. 1 mg/g WS (Whole ~~nliltered Samplc). On arnmol~iuin nitrate, early expoiientiaI growth ~~t i l i z e d more NI-13-nitrogen than NOJ-l~itrogen \vith a corlcornitant decrease in pH. I n the range pH 3.0-2.8 NHa-nitrogen uptalre and dry weight increase ceased, but SOs-nitrogen uptalce continued, and the pH increased until growth and NI-I:,-nitrogen uptalce restarted. 'This pattern could be repeated. Finally, expo~lential growth was resumed a t a lo\\, specilic gro\\.th rate. On gIycine, urea, and ammoni~lm tartrate media, exponel~tial growth continned to a dry weight of about 7 mg/g \VS. During, this pcriod the uptalces relative to dry weight (contributions) of glucose, nttrogen, phosphate, and magnesium remained coilstant and were unaffected by the rate of agltatloll, as also was the specihc growth rate, but the latter decreased with increasing glucose concentration.A period of linear growth could folio\\, the exponential period. The contribution bf glucose was ireater, and that of phosphate and magnesium less, than during exponential growth. The dry weight a t which espol~ential growth changed to linear growth \\.as greater the higher the rate of agitation, and this change may be a response to oxygen restriction. After nitrogen exhaustion, fat and carbohydrate accum~llntion in tlie cells largely accour~ted for the increase in dry weight. The specilic rates of dry weight increase and glucose uptake remained constant over the lower range of initial nitrogen concentrations. Both rates decreased with increasing nitrogen over the higher range.Gibberellic acid production began a t , or soon after, nitrogen exhaustion. The amount present increased lirlearly with time. The productivity decreased with increasing glucose conce~~tration; and first increased and then decreased with increasing initial nitrogen. 'I'he maximum amount produced was proportional to the initial nitrogen provided. Some published results are discussed in the light of these relations.

The growth of Gibberella fujikzlroi in stirred culture was studied. Media were designed in which the initial concentrations of glucose (G), nitrogen (N), phosphorus (P), and magnesium (M) were varied so that the first nutrient was exhausted a t a selected dry weight, and the remaining nutrients in all available sequences thereafter. Distinct phases of growth, related to the changing nutritional status of the mold, have been defined.The balanced phase was a period of proliferation in the presence of all nutrients, during which a unit increase in dry mycelium was accompanied by constant uptakes of G, N, P, M, and potassium (I<). The morphology remained virtually unchanged, and the d r y mycelium contained ca. 6 % fat, ca. 16% carbohydrate, and ca. 13% phosphorus-containing compounds, and the fractions of each remained constant. This phase continued until the first nutrient was exhausted. I'roliferation, indicated by increases in fat-and carbohydrate-free dry weight, then ceased in N-and G-limited fermentations. I n P-and M-limited fermentations, proliferation continued until the subsequent exhaustion of either G o r N, and during this transition phase the carbohydrate content of the mycelium increased, while in M-limited fermentations the fat content also increased. I n P-limited fermentations the uptake of both M and I< ceased, and reserves of metaphosphate were used.At the exhaustion of N in N-, P-, or M-limited fermentations, proliferation ceased but the dry weight continued to increase due t o increases in carbohydrate and triglyceride. In the presence of sufficient glucose, maximum amounts of 45% fat, visible as oil globules, and 32y0 carbohydrate were formed, but in the presence of less G these ceased t o increase when G was exhausted before these maxima were reached. In either case the nzaintenance phase followed, during which all mycelial components remained constant except the triglycerides, which decreased when exhaustion of G had initiated the maintenance phase; otherwise they also remained constant until G was subsequently exhausted, and then decreased. T h e terntinal phase began when the triglycerides were exhausted, and also when G was exhausted in G-limited fermentations, or in P-and M-limited fermentations in which G was exhausted before N. This phase was characterized by hyphal breakdown, a decrease in dry weight, and the liberation of mycelial components into the medium. 'Manuscript Can. J. Microbiol. Downloaded from www.nrcresearchpress.com by NC STATE UNIVERSITY on 09/21/13For personal use only. 80-1. FermenterThis was of conventional design, made of stainless steel, 20 in. diameter and 29 in. deep (Fig. 4). T h e two-paddle stirrer was driven a t 425 r.p.m. T h e supply of cooling water was automatically regulated to provide temperature control t o &0.15O C. Air was humidified and sterilized by passage through larger models of the apparatus already described. 2Model 0307, series WA, product of Hoover Ltd., Regent Street, London, W.1. Can. J. Microbiol. Downloaded from www.nrcresearchpress.com ...

No abstract

SUMMARY:Ten antibiotics have been included in this study : eight of them were metabolic products of fungi isolated from soils of the Bagshot Sand type. Their stability in Bagshot Sand soils and in a neutral garden loam has been investigated. Some were more stable than others, the rate of inactivation varied from soil to soil, but all exhibited a fair degree of stability in some of the soils. Four types of inactivation could be distinguished: (1) The natural pH of the soil was sometimes that at which the antibiotic was intrinsically unstable ; this was noted specially with albidin, frequentin, gliotoxin, penicillin and viridin . ( 2 ) Inactivation caused by some form of biological activity, indicated by less rapid inactivation in heattreated than in untreated soil, was observed with griseofulvin, mycophenolic acid and patulin. (3) Adsorption on the soil was noticeable only in the case of streptomycin, the only basic antibiotic studied; acid-washed sand was able t o bind appreciable quantities of this antibiotic. (4) Some other form of inactivation, probably chemical in nature, was concerned in the inactivation of gladiolic acid, penicillin and streptomycin.

SUMMARY: A study has been made, using a plating technique, of the fungi occurring in acid sandy podsol soils and of their distribution at different levels of the soil profile. The most widespread species, characteristic of this type of soil, included: Absidia orchidis, Mortierella alpina, Mucor ramannianus, Penicillium frequentans, P. nigricans, P. roqueforti, P. terlikmshii and Tricho-a wiride. A number of other species were locally abundant, including Absidia glauca, Coniothyrium sp., Gliocladium sp. (roseum series), Penicillium citrinum and Zygorhyncus nmellem'.The plate counts of viable fungal units decreased sharply from upper to lower levels, though there was occasionally a secondary maximum in the upper part of the B horizon. Most species were characteristically found most abundantly in upper layers of the A horizon, but Mucor ramannianus was notable for its abundance a t much lower levels ; in several of the profiles examined it was isolated in almost pure culture from the B horizon.Of the sixty-five species isolated, about half produced antibiotics. Most of these were toxic to fungi and bacteria; only a few cases of specific antifungal or antibacterial activity were encountered. The Phycomycetes differed from other groups in that none produced antifungal substances. The capacity to produce antifungal antibiotics appears to be correlated with the distribution of species; of the widespread and locally abundant fungi, 45% produced such antibiotics as compared with 15 yo of the rare fungi. Nevertheless, certain widespread species (e.g. Absidia orchidis, Mortierella alpina, Mucor ramannianus, Penieillium roqueforti) did not produce antifungal antibiotics, so it cannot be considered to be a necessary character of widespread soil fungi. There is some evidence that such widespread non-producers of antibiotics are relatively resistant to the antibiotics produced by other species.An attempt has been made to group the fungi isolated into Burges' ecological categories of 'sugar-fungi' and 'humus-fungi' on the basis of their capacity to attack and utilize carboxymethylcellulose (CMC). Only 26 % of the fungi were unable to utilize CMC, Phycomycetes being prominent among these. Whereas 35 yo of the rare fungi and 54% of locally abundant fungi were 'sugar-fungi', only 17% (all Phycomycetes) of the widespread fungi were ' sugar-fungi'.These results are believed to lend support to the view that antibiotic production is of ecological significance to soil fungi. They also provide information which can form the basis of an experimental search for more direct evidence.