Experimental Studies on the Physiology of the Phycobiont and Mycobiont Ramalina ecklonii By

Abstract

The lichenized fungus and alga of the fruticose lichen Ramalini ecklonii were isolated into pure cultures. The ascospores of the fungus failed to germinate in less than five weeks incubation in spite of the use of a variety of cultural conditions. The fungus showed a considerable increase in growth on malt extract agar. Both organisms showed a marked tolerance for high concentrations of glucose although growth was quantitatively reduced. The fungus was able to use a variety of carbon and nitrogen sources as well as an extract of algal cells. Cultivation in the absence of biotin and thiamine failed to yield significant amounts of growth. The alga yielded 27 mg of dry weight after three weeks in a synthetic medium under low light intensities. The alga could be grown in satisfactory amounts on CO2 and inorganic salts with moderate light intensities. Experiments using 14CO2 showed the fungus able to incorporate the extra‐cellular and intra‐cellular products of algal metabolism. The rate of incorporation of extra‐cellular products was inhibited by high concentrations of biotin and thiamine. The alga assimilated l4CO2 which was retained by the cells over a period of 14 days, at which time 78 per cent of the activity was insoluble in 80 per cent ethanol. An extract of the fungus labelled with 14C glucose was partially taken up by the alga and 50 per cent of the label was insoluble in 80 per cent after three days incubation in the light. No lichen acids were found in either the fungal cultures or the algal cultures although large amounts (e.g. 2 liters) of material were extracted and chromatographed. Usnic acid was produced by the intact lichen thallus.

A Guide to the Algae Occurring as Lichen Symbionts: Isolation, Culture, Cultural Physiology, and Identification

“…This fi gure is considerably less than that reported for other photosynthetic micro organisms (HOOGENHOUT & AMESZ, 1965). Fox (1965) showed that a Trebouxia phycobiont which was light saturated at 170 ft-c at 22°C. produced 39.4 III of O2 per mg dry wt per hr, while a free-living Chlorella, also light-saturated at 170 ft-c., produced 51.0 III O2• Fox (1967) found a comparatively rapid photosyn thetic assimilation by Trebouxia, which was in sharp contrast to the slow growth of this alga.…”

“…One method for accomplishing this involves fragmenting a thallus in a blender and centrifuging the resulting slurry differentially. The sediment composed of the algal cells is diluted and pipetted onto plates of mineral agar (Fox, 1966). Bold's Mineral Medium (DEASON & BOLD, 1960) Part I.…”

“…Fox (1967) found that Trebouxia erici (from Cladonia cristatella) showed a growth constant of about 0.09 when cul tivated with 1 % CO2 in a modifi ed Bold's mineral medium. This fi gure is considerably less than that reported for other photosynthetic micro organisms (HOOGENHOUT & AMESZ, 1965).…”

Fungus‐alga Ultrastructure in the Lichen, Cornicularia Normoerica

“…In the case of another fruticose lichen, Ramalina ecklonii, Fox (1966) demonstrated the capacities of each symbiont to take up labeled extracts produced by the other in pure culture. However, neither was individually able to produce usnic acid found in the intact thallus.…”

Location of Several Enzymes of ʟ-Arginine Catabolism in Evernia prunastri Thallus

“…Isolation of both symbionts [12][13][14] was carried out by macerating the samples in a mortar with enough volume of the appropiate buffer containing 1 mM EDTA. Homogenate was centrifuged at lOOOxgr for 2 min and supernatant was again cen trifuged for 1 min and 30 s until the hyphal suspen sion becomes colourless.…”