D.H. Jennings

Long distance translocation in Serpula lacrimans: Velocity estimates and the continuous monitoring of induced perturbations

Apparatus for continuous in situ monitoring of translocation of radioisotopes in mycelium of Serpula lacrimans is described. Similar velocities of translocation were found for several different isotopes. Velocities were much higher than those previously reported. Addition of a respiratory inhibitor or a concentrated solution to the food source resulted in rapid inhibition of translocation along the full length of the mycelium. The results suggest that solute and water uptake at the food source is the major driving force for translocation which takes place as mass flow of solution.

Evidence for diffusion being the mechanism of translocation in the hyphae of three molds

Abstract Translocation of nutrients from a part of the mycelium exposed to an ample supply of a particular nutrient to other parts of the mycelium might be of the utmost importance for the proliferation of fungi in a nutritionally heterogeneous environment. The extent and mechanism of such translocation for saprophytic molds are poorly understood. In this study, diffusion has been shown to be responsible for the translocation of label added as [ 14 C]glucose and [ 32 P[orthophosphate to cultures of Rhizopus nigricans grown on opposing gradients of glucose and other nutrients in glass fiber filters. Translocation of the labeled nutrient was found when the label was added to the side of the mycelium that was exposed to high levels of the nutrient. When added to the inoculation point or to the side of the colony exposed to low levels of the nutrient, the labeled compound was immobilized by the mycelium at the addition point. Translocation was bidirectional in that 14 C was translocated simultaneously in the opposite direction to 32 P. A sink for the translocated nutrients was apparent in the region of sporulation. This pattern of translocation of label added as [ 14 C]glucose to the glucose surplus side was similar for Trichoderma viride and Stemphylium sp.

Growth of Serpula lacrimans in relation to water potential of substrate.

Serpula lacrimans grows over lime-sand plaster containing more than 1% (w/w) water at a rate comparable to that on nutrient agar. When the water content of the plaster is lower, growth is reduced and occurs non-uniformly in a series of flushes. Growth under these conditions is stimulated by the addition of water or inhibited by the addition of 0.5 molal sucrose to the inoculum and the water content of the plaster is raised as the mycelium grows over it. Studies using agar and liquid culture show that the fungus cannot withstand water potentials of less than about −60 bars. Growth takes place on plaster at a much lower (−600 bars) water potential.

Growth ofDebaryomyces hansenii andSaccharomyces cerevisiae in relation to pH and salinity

Abstract Debaryomyces hansenii is able to grow more readily in the presence of high concentrations of sodium and in alkaline media thanSaccharomyces cerevisiae. However, pH 5.2 depresses growth (cell numbers) of both yeasts. The effect can be reduced by the salts of weak acids in the medium. Increased cell numbers are accompanied by increased cell potassium concentration. WhenD. hansenii grows in alkaline medium, it is better able to select for potassium against sodium than when it is grown in more acid medium. The ability of bicarbonate to stimulate growth ofD. hansenii but notS. cerevisiae in acid pH, and the lack of proton excretion byD. hansenii in alkaline medium suggest that for yeast: (i) the production of an alkaline cytoplasm removes hydrogen ions from competing with sodium for exchange with potassium across the plasmalemma, and (ii) there may be a bicarbonate pump at that membrane not present inS. cerevisiae.

The content of soluble carbohydrates and their translocation in mycelium of Serpula lacrimans

Trehalose and arabitol are the most abundant carbohydrates in mycelium of Serpula lacrimans growing over Perspex. Trehalose is the major soluble carbohydrate in strands while arabitol reaches high levels in more marginal regions. Uptake of [14C]glucose results in the bulk of label being found in trehalose in all mycelial regions. It appears that trehalose is the major form by which carbohydrate is translocated.

Localization by X-ray microanalysis of soluble ions, particularly potassium and sodium, in fungal hyphae

Two methods are described for the preparation of hyphae for X-ray microanalysis of their soluble ions. Freeze-drying leads to ultrastructural changes and there is evidence of relocation of potassium during preparation. Freeze-quenching appears to meet the necessary stringent criteria for a successful procedure. The spatial distributions of potassium and sodium in the hyphae of Dendryphiella salina determined by X-ray microanalysis are paralleled by temporal changes in content of the two ions determined by flame photometry in mycelium growing in shake culture. The problem of replication of observations is considered. The study has shown that the apex of the hypha of D. salina is less able to select for potassium against sodium than the remainder of the hypha. The 1- to 50- μ m region behind the apex is the most selective for potassium against sodium.

A glass fiber filter technique for studying nutrient uptake by fungi : the technique used on colonies grown on nutrient gradients of carbon and phosphorus

In most natural environments supporting fungal growth, nutrients are heterogeneously distributed in space. Growth of a fungus will thus take place in an environment characterized by gradients. A system has been developed for growth of fungi on opposing carbon and mineral nutrient gradients, present in liquid medium in glass fiber filters. By labeling the carbon or phosphorus in the medium, the amount of carbon or phosphorus accumulated inside hyphae ofRhizopus nigricans and the amount still present outside the hyphae were determined. The distribution of labeled C and P in the medium and in the colonies of the fungus grown in the presence and absence of initial gradients in the medium was compared. In both cases, little carbon or phosphorus was found remaining in the medium after fungal growth. With colonies grown on media without an initial gradient, two peaks of carbon and phosphorus accumulation were found, but when there was a gradient there was only one such peak. These peaks coincided with the regions of greatest sporulation. It was concluded, by comparing the distribution of the total amount of carbon inside and outside mycelium grown on gradients with that in control media which was uninoculated, that the translocation of carbon inside the mycelium could have been brought about by simple diffusion.

Tear or drop formation by mycelium of Serpula lacrimans

When Serpula lacrimans grows over a non-nutrient, non-absorbant surface, droplets are produced in the 1 mm margin of the colony, mainly at hyphal tips. Tips may grow through droplets or become trapped in them. Sometimes tips burst. The rate of increase in droplet size can be reduced by severing the hyphae or applying 10 −4 mol 1 −1 sodium azide, 2 molal sucrose, or 1 molal potassium chloride to mycelium which is growing on the agar food base. The observations are discussed in terms of a pressure driven flow of fluid along the hyphae.

Further observations on tear or drop formation by mycelium of Serpula lacrimans

Serpula lacrimans produces droplets in the hyphal tip region. Droplet volume can be reduced by high KCl and glucose concentrations at the food source. This reduction is not due solely to changes in vapour pressure above the droplets. Experiments with inhibitors show that contractile micro-filaments and microtubules behind the hyphal tips are probably not directly involved in droplet production and growth. Respiration and potassium uptake at the food base appear to be involved. The osmotic properties of droplets are investigated and the results discussed in terms of a pressure-driven water flow along the hyphae. The implications for the mechanism of translocation of solutes along hyphae are considered.

Membrane-bound ATPase activity, properties of which are altered by growth in saline conditions, isolated from the marine yeast Debaryomyces hansenii

A membrane fraction, relatively free from mitochondrial membrane contamination, has been isolated from Debaryomyces hansenii containing Mg 2+ -ATPase activity which possessed a pH optimum of 6–6.5 when grown in non-saline conditions but an additional optimum at pH 8 when 1.5 m sodium chloride was present in the growth medium. Under both conditions of growth the alkaline ATPase activity in the assay medium was much less sensitive to 4-acetamido-4′- iso -thiocyanatostilbene-2,2′-disulphonate (SITS), and to concentrations of sodium chloride greater than 100 mM, than the acid ATPase activity. In other respects, the properties of the alkaline ATPase was similar to those of plasma membrane-bound ATPase activity isolated from Saccharomyces cerevisiae .