560 Notes and brief articles

SAEZ, H. (1975). La thermotolerance des Aspergillus.Revue de l'Institute Pasteur de Lyon 8, 35-51.

SNOW, D. (1949). The germination of mould spores atcontrolled humidities. Annals of Applied Biology 36,1-17·

TUITE, J. F. & CHRISTENSEN, C. M. (1957). Grain storagestudies. XXIV. Moisture content of wheat seed inrelation to invasion of the seed by species of theAspergillus glaucus group, and effectof invasion upongermination of the seed. Phytopathology 47, 323-327.

CELLULOSE DECOMPOSITION BY SOME TROPICAL AQUATIC

HYPHOMYCETES

BY N. SINGH

Department of Botany, Fourah Bay College, University of Sierra Leone, Freetown, Sierra Leone

Cellulose in the cell walls of submerged decayingleaves and twigs may serve as a substrate for aquaticfungi but only a few species of aquatic fungi havebeen tested for their cellulolytic ability. Theutilization of cellulose has been reported inAnguillospora longissima (Ranzoni, 1951), Articulo-spora tetracladia, Lemonniera terrestris, Varico-sporium elodeae (Tubaki, 1958), Margaritisporaaquatica (Tubaki, 1958; Nilsson, 1964), Tetraclad-ium marchalianum (Nilsson, 1964), and Pleuroped-ium tricladioides (Marvanova & Iqbal, 1973). Fivespecies of tropical aquatic hyphomycetes isolatedfrom a local stream were investigated for theirability to decompose cellulose in pure culture.

The fungi were grown in a medium of thefollowing composition: NH4N03, 2 g; KH2P04,

1 g; MgS04 , 0'50 g; FeSOp 0'02 g; yeast extract,0'05 g; distilled water, 1 I; pH adjusted to 6'0.Fungi were grown in 100 ern" conical flasks con-taining 20 ern" of the medium to which either car-boxymethylcellulose (10 g l~l) or a single 5'5 ernWhatman No. 3 paper disk (approx. dry weight0'45 g) was added. The flasks were sterilized byautoclaving at 121°C for 15 min. Four replicateflasks were inoculated with 1 em" of a fine mycelialhomogenate for each fungus and incubated at 28°under stationary conditions. Four uninoculatedflasks served as controls. Flasks containing carboxy-methylcellulose were harvested after 2 weeks andthose containing filter paper after 6 weeks.

Mycelium and filter paper were filtered through

tared sintered glass crucibles and dried at 80° for24 h. The oven dry weight loss of filter paper disksreflects the amount of cellulose respired by thefungi but not the proportion converted intomycelial dry weight. The protein and reducingsugar content of the filtrate were respectivelymeasured by the Folin-phenol reagent of Lowry,Rosebrough, Farr & Randall (1951) and dinitro-salicylic reagent of Miller (1959). All proteinmeasurements were standardized against blanks ofuninoculated medium. Enzymatic activity was alsomonitored viscometrically in an Ostwald-typeviscometer. Four em" of culture filtrate were mixedwith 6 ern" of 1% (wIv) carboxymethylcellulose incitrate phosphate buffer (pH 4'6) and the mixtureincubated at room temperature (28°) for 1 h.Enzyme activity was expressed as the percentageloss in viscosity.

Earlier investigations on the cellulolytic activitiesof aquatic fungi report only on the qualitativeutilization of cellulose. All the fungi tested heredegraded cellulose and caused weight losses of filterpaper disks (Table 1). Lateriramulosa uni-inflataMatsushima showed the strongest cellulolyticability with 12'5 % loss in weight while Margariti-spora aquatica Ingold showed the weakest cellulo-lytic ability with 5'2 % loss in weight. The otherfungi tested caused percentage weight lossesbetween these two values and Anguillosporalongissima (de Wild). Ingold and Lunulosporacurvula Ingold showed similar cellulolytic activities.

Table 1. Cellulolytic activity of some aquatic hyphomycetes (mean values from four replicates)

Anguillospora longissimaLateriramulosa uni-infiataLunulospora curvulaMargaritispora aquaticaTriscelophorus monosporus

Control

Trans. Br. mycol. Soc. 79 (3), (1982)

Protein in Sugars in Loss of Filter paperDry wt medium medium viscosity loss

(mg) (mg cm") (mg em-a) (%) (%)

12'5±°"4 0'153 0'542 52 8'215±0'6 0'185 0'920 57 12'59±0'3 0'110 0'700 45 8·88±0'5 0'080 0'096 31 5'2

11±0'8 0'130 0'220 48 7"30 0'012 0'018 0·8

Printed in Great Britain

Notes and brief articles 561

Carboxymethylcellulose was also decomposed asshow n by the loss in viscosity of solutions (T able1). Again L. uni- inflata showed the maximum(57 C),,,) and M . aquatica th e minimum (31 '~~» )

act ivity .The cellulolytic ability of these fungi in culture

may reflect a similar acti vity in th e field . Aquaticfungi have been shown to more dom inant member sof the microflora than bacteria during th e earlystages of leaf decomposition in strea ms (Kaushik &H yne s, 1968, 1971 ; Triska , 1970 ; Willoughby,1974). Aquatic hyphom ycet es have a world-widedistribution and have been repeatedl y obse rved ondecaying leaf litt er in temperate and tropi calstreams (N ilsson , 1964 ; Ingold , 1966 ; Singh &Musa, 1977). A major role of th ese fungi inprocessing of leaf material in water ha s beensuggested by various investigators (N ilsson , 1964;Triska, 1970; Barlocher & Kendrick, 1974;Suberkropp & Klug, 1976). The present investiga-tion provides some evidence that aquati c hypho-mycct es play an active role in the decomposition ofleaf materi al in water.

I wish to th ank Mr R. Alexander for technicalassistance.

REFERE N CE S

BARLOCHER, F . & KENDRICK, B. (1974). Dynam ics of th efungal population on leaves in a stream. J ournal ofEcology 62, 761-791.

INGOLD, C. T . (1966). The tetraradiate aquatic fungalspore . My cologia 58, 43-56.

KAUSHIK, N . K . & HYNES, H . B. N . (1968). Exper iment alstudy on the role of autumn-shed leaves in aquaticenvi ron ment s. J ourr1<11 of Ecology 56, 229-243 .

KAUSHIK, N . K. & HYNES, H . B. (1971). The fate of thedead leaves that fell into str eams. A rchiven fu rHydrobiologie 68, 465-5 15.

LOWRY, O. H ., ROSEBROUGH, N. J., FARR, A. L. &RANDALL, R. J. (1951). Protein measur ement with theFalin ph enol reagent . Jo urnal of Biological Chemistry193, 265- 275.

MARVANOVA, L. & IQBAL, S. H . (1973). Pleuropediumtricladioides gen . et sp . nov. A ntonie van Leeuwenhoek39,4° 1-4° 8.

MILLER, G . L. (1959). Use of dinitrosalicylic acid reagentfor de termination of reducing sugar. A nalyticalChemist ry 31, 426-428.

NILSSON, S. (1964). Freshwater hyphom ycetes, taxonomy,morphology and ecology. Symbolae B otanicae Upsali-enses 18, 1-13 0.

RANZONI, F . V. (1951). Nutrient requirem ent s for twospecies of aquatic hyphomycetes. My cologic 43 ,130-141.

SINGH, N . & MUSA, T . M. (1977). Terrestrial occur renceand the effect of temperature on growth, spor ulationand spore germ ination, of some tropical aqu atichyphomycetes. Tr ansactions of the British My cologicalSocie ty 68, 1°3-106.

SUBERKROPP, K . & K LUG, M. J. (1976). Fungi andbacteria assoc iated with leaves during proc essing in awoodland stream. Ecology 57, 709-719.

TRISKA, F . J . (1970). Seaso nal distribution of aquatichyph omycetes in relation to the disappearance of leaflitter from a woodland stream. Ph .D. Thesis, Universityof Pittsburgh.

T UBAKI , K . (1958). Studies on Japanese hyph ornycetes.J ournal of H attori Bo tanica l Lab oratory 20, 142- 244.

WILLOUGHBY, L. G. (1974). De composition of litt er infreshwater. In B iology of Plan t L itter Decomposition 2 ,

(cd . C. H. D ickinson & G . J . F . Pugh), pp . 659-681.Lond on : Academic Press.

BASIDIOSPORE GERMINATION IN TR EMELL A FOLIA C E A

BY C. T. INGOLD

I I Bu ckner's Close, Benson, Oxford OX9 6LR

D etails of basidiospore germination in Tremellamesenterica Retz. ex Hook. have already beendescribed (I ngold, 1982). The present note recordsth e process in T . fo liacea Pers . ex F r.

In a light spore deposit on 0 '2 ');, malt agar (MA)in a Petri dis h, there was ioo "., germinat ion at th eend of 24 h at room temperature (15- 18 DC). Bythat time each basidi osp ore was at th e centre of aminute colon y of yeast-like cells. Germinat ion onwate r agar was similar.

T o follow th e early stages of germi nat ion, spo reswere allowed to fall from a spo rophore for o·5 h onto a th in layer ( 1- 2 mm deep) of 0 ' 2 " " MA. A

square of spore-bearing agar was then cut out,placed on a slide and, without added water, coveredwith a cover-slip . Under these conditions germina-tion appeared to pr oceed normally. A high-powermicroscope field containing a suitable group ofbasidi ospores was then selected , and the beha viourof three spo res over the next 9 h was recorded bycamera lucida drawings at intervals (F ig. 1). Thefirst visible change, occurring about 3 h from thestart of observa tion, was the production of a lateral,sessile conidium whi ch in due course separatedfrom th e parent spore . Thereafter another began to

develop in th e same posit ion . In spo res A and C

TrQlIS. Dr . my col, S oc. 79 (3), ( t 982) Prim ed in Grea t B ritain