Utilization Of Substrata

Substrate utilization by aquatic basidiomycetes depends on the substrata and environment from which they were isolated. Probably the least studied group in this respect is the marine basidiomycetous yeasts. Most have been isolated from water columns (Fell et al., 1973, 2001) or from water scums or the internodes of

Table 6 Mean percentage loss in dry weight of five timbers exposed to marine basidiomycetes for 24 weeks at 10 and 22°C

Fungus species

Timber species

10°C

22° C

Digitatispora marina

Ochroma lagopus

14.33

4.94

Fagus sylvatica

10.07

2.68

Pinus sylvestris

-0.33

0.57

Halocyphina villosa

O. lagopus

-0.58

22.98

F. sylvatica

3.43

7.98

P. sylvestris

-0.59

-0.09

Avicennia officinalis

NA

5.78

Xylocarpus granatum

NA

0.51

Nia vibrissa

O. lagopus

13.75

27.91

F. sylvatica

4.33

5.55

P. sylvestris

-1.26

0.08

Monodictys pelagica

O. lagopus

28.30

40.87

Marine soft-rot ascomycete

F. sylvatica

11.03

20.76

P. sylvestris

0.39

0.68

Source: After Mouzouras (1986, 1989).

Note: data for gain in weight we adjusted with +/— loss in dry weight of controls; NA not tested.

Source: After Mouzouras (1986, 1989).

Note: data for gain in weight we adjusted with +/— loss in dry weight of controls; NA not tested.

Equisetum fluviatile (Jones and Sloof, 1966; Webster and Davey, 1975). These in general were able to utilize simple sugars (glucose, maltose, sucrose) and also cellobiose, D-xylose and D-mannitol (Fell et al., 1973). There is no evidence that these marine basidiomycetous yeasts can utilize more complex polymers, for example lignocellulose.

Most studies on lignocellulose decomposition by marine basidiomycetes have been on D. marina, Haloc. villosa and N. vibrissa (Mouzouras, 1986, 1989; Mouzouras et al., 1987). D. marina, Haloc. villosa and N. vibrissa were grown on test blocks of Fagus sylvatica, Pinus sylvestris and Ochroma lagopus and at two temperatures (10, 22°C). All caused weight loss of wood (Table 6) although this was much lower than in their terrestrial counterparts, for example more than 75% after 90 days incubation on birch wood, Ganoderma applanatum, Lenzites betulina, Trametes hirsuta (KMrik, 1974). Temperature affected their ability to cause decay, with Haloc. villosa causing a greater weight loss at the higher temperature (22°C) and conversely D. marina at the lower temperature 10°C (Mouzouras, 1986). The nature of the substratum also affected the weight loss caused by Haloc. villosa, for example 5.7% loss of A. alba and none in X. granatum, both mangrove timbers (Mouzouras, 1989), while on O. lagopus (a soft timber with a low lignin content) losses of 30% have been noted (Mouzouras, 1986).

The ability of these basidiomycetes to cause decay of wood is dependent on the enzymes they possess and the salinity of the media they are grown on (Table 7). N. vibrissa produced cellulase, peroxidase and laccase on seawater and deionized water, but D. marina produced these enzymes only on seawater media (Rohrmann and Molitoris, 1992). Growth and enzyme production of Haloc. villosa

Table 7 Comparison of wood-degrading enzymes of marine and selected terrestrial basidiomycetes

Fungus species

Deionized water

Seawater

Cellulase

Laccase

Tyrosinase

Peroxidase

Cellulase

Laccase

Tyrosinase

Peroxidase

Digitatispora marina

w

1

+

+

Bjerkandera fumosa

w

3

w

1

1

2

2

Phellinus igniarius

w

2

2

3

3

2

1

3

Source: After Rohrmann and Molitoris (1992).

Note: Activity: +, presence of enzyme; —, no enzyme detected; w, weak; 1, clear reaction; 2, strong reaction; 3, very strong reaction.

QJ tt

Source: After Rohrmann and Molitoris (1992).

Note: Activity: +, presence of enzyme; —, no enzyme detected; w, weak; 1, clear reaction; 2, strong reaction; 3, very strong reaction.

was almost identical in natural and artificial seawater media (Rohrmann et al., 1992). Different strains of N. vibrissa produce amylase, caseinase, cellulase, gelatinase, laminarinase, lipase, nitrate reductase, peroxidase and xylanase, but none produced tyrosinase (Schimpfhauser and Molitoris, 1991).

Freshwater basidiomycetes have been isolated from decaying leaves, foam, woody debris, submerged test blocks and are able to breakdown major plant cell wall polysaccharides: pectins, cellulose and hemicellulose (Chamier, 1985). Their ability to degrade lignin remains to be established, although Marvanova and Bandoni (1987) listed Naiadella fluitans and Taeniospora spp. as laccase positive in an alpha-naphthol test (Stalpers, 1978).

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