David E. Padgett

Fungal biodiversity in aquatic habitats

Fungal biodiversity in freshwater, brackish and marine habitats was estimated based on reports in the literature. The taxonomic groups treated were those with species commonly found on submerged substrates in aquatic habitats: Ascomycetes (exclusive of yeasts), Basidiomycetes, Chytridiomycetes, and the non-fungal Saprolegniales in the Class Oomycetes. Based on presence/absence data for a large number and variety of aquatic habitats, about 3,000 fungal species and 138 saprolegnialean species have been reported from aquatic habitats. The greatest number of taxa comprise the Ascomycetes, including mitosporic taxa, and Chytridiomycetes. Taxa of Basidiomycetes are, for the most part, excluded from aquatic habitats. The greatest biodiversity for all groups occurs in temperate areas, followed by Asian tropical areas. This pattern may be an artifact of the location of most of the sampling effort. The least sampled geographic areas include Africa, Australia, China, South America and boreal and tropical regions worldwide. Some species overlap occurs among terrestrial and freshwater taxa but little species overlap occurs among freshwater and marine taxa. We predict that many species remain to be discovered in aquatic habitats given the few taxonomic specialists studying these fungi, the few substrate types studied intensively, and the vast geographical area not yet sampled.

An evaluation of the efficiencies of several ergosterol extraction techniques

Axenic cultures representing ten species of filamentous higher marine fungi were analyzed for ergosterol content to determine the relative efficiencies of five extraction protocols. Methanol refluxing resulted in consistently higher yields than did ethanol treatment. In every case treatment of mycelia with alcoholic KOH solution substantially enhanced ergosterol recovery. Experimental results relative to fungal biomass quantification in vascular plant detritus are discussed.

Fungal and bacterial contributions to the decomposition of Cladium and Typha leaves in nutrient enriched and nutrient poor areas of the Everglades, with a note on ergosterol concentrations in Everglades soils.

Fungal biomass was detected in peat soils from throughout the Everglades based on the presence of ergosterol. Ergosterol concentrations in soils were not detectably affected by the dominant plant, Cladium jamaicense or Typha domingensis , or phosphorus content of soils. In situ decomposition of decaying leaves, measured by respiration, was high (maximum 484 ul O 2 h −1 g −1 dry biomass). Approximately 30% of respiration was by bacteria, and the rest was by fungi and other eukaryotes. Respiration rates were essentially the same for decomposing leaves of both plant species, with higher rates early in the decomposition process. Respiration rates were relatively unaffected by the nutrient status of the site, except for eukaryotic respiration on Cladium , which was usually higher at a high nutrient site. Ergosterol concentration increased in decaying leaves through time and was unrelated to the nutrient level except for Cladium , where it was higher at the high nutrient site. Eukaryotic respiration was not correlated with ergosterol concentration in decomposing leaves of Typha , but was positively correlated with ergosterol for Cladium.

A technique for distinguishing between bacterial and non-bacterial respiration in decomposing Spartina alterniflora

A number of antibiotics were used to suppress bacterial activity in decomposing Spartina alterniflora. The effectiveness of each treatment was quantified using INT formazan vital staining and epifluorescent microscopy. Bacterial suppression of selected treatments was verified using standard plate count procedures. Chloramphenicol treated samples (exhibiting 87–90% bacterial suppression) were analyzed respirometrically and found to consume only 30% less O2 than controls. Non-bacterial respiration (probably fungal) accounted for 70% of the respiration.

A newly discovered role for aerobic fungi in anaerobic salt marsh soils

70 x 8-10 pm, 8-spored, unitunicate, apex trun? cate, containing a non-amyloid apical ring, as? cospores biseriate in the middle, uniseriate above and below, filling the ascus. Ascospores ellipsoid to ovoid, 12-17 x 5.5-7.0 pm, 1-septate, septa often appearing angular, colorless, smooth, often 1-2 orange guttules per cell, sometimes germi? nating in the centrum, L/W 2.3. Centrum con? tents appearing slightly brown, orange oily drops emitted from crushed perithecia. Paraphyses not

Growth of filamentous fungi in a surface-sealed woody substratum buried in salt-marsh sediments

Balsa wood panels were sealed to prevent oxygen diffusion from aerobic zones and buried in a North Carolina salt marsh to determine whether filamentous fungi could invade them despite the resulting anoxia. Results were similar to those of a previous study which had employed unsealed panels and suggest that fungi involved either are facultative microaerophiles or capable of translocating sufficient oxygen through their hyphae to permit growth into oxygen-deficient soil strata.

Evidence for extreme salinity tolerance in saprolegniaceous fungi (Oömycetes)

Ander, P., and K.-E. Eriksson. 1977. Selective degradation of wood components by white-rot fungi. Physiol. Pl (Copenhagen) 41: 239-248. Antai, S. P., and D. L. Crawford. 1982. Degradation of extractive-free lignocelluloses by Coriolus versicolor and Poria placenta. Eur. J. Appl. Microbiol. Biotechnol. 14: 165-168. Crawford, D. L., and R. L. Crawford. 1976. Microbial degradation of lignocellulose: the lignin component. Appl. Environ. Microbiol. 31: 714-717. Effland, M. J. 1977. Modified procedure to determine acid-insoluble lignin in wood and pulp. Tappi 60(10): 143-144. Glover, G. H. 1975. Cotton processing, by-products, and wastes. Pp. 403-411. In: Solid wastes: origin, collection, processing, and disposal. Ed., C. L. Mantell. Wiley, New York. Hatakka, A. L, and A. K. Uusi-Rauva. 1983. Degradation of 14C-labelled poplar wood lignin by selected white-rot fungi. Eur. J. Appl. Microbiol. Biotechnol. 17: 235-242. Holler, J. R., and J. C. Brooks. 1980. Nutritional studies of Pycnoporus cinnabarinus. Mycologia 72: 329-337. Morey, P. R., R. M. Bethea, P. J. Wakelyn, I. W. Kirk, and M. T. Kopetzky. 1976. Botanical trash present in cotton before and after saw-type lint cleaning. Amer. Industr. Hyg. Assoc. J. 37: 321328.

Growth of filamentous fungi into balsa wood panels buried in North Carolina salt marsh sediments

Balsa wood panels were buried vertically in sediment in two North Carolina salt marshes to assess the effect of living versus non-living plants, soil redox potential and depth of sediment drainage on depth of fungal growth. Fungi penetrated panels deepest where soil drainage was greatest and in several cases grew at depths where surrounding soil was anoxic.

Salinity tolerance of an Aphanomyces isolate (oomycetes) and its possible relationship to ulcerative mycosis (UM) of Atlantic menhaden.

An Aphanomyces sp. recovered from and thought to be a pathogen of Atlantic menhaden was subjected to salinity stress to see if its behavior suggested that it was a salt-resistant isolate. Respiration during prolonged salinity exposure as well as hyphal morphology suggested a degree of salinity tolerance generally greater than previously reported for this or other saprolegniaceous fungi. Furthermore, zoo? spores were shown to germinate during salinity stress if exogenous nutrients are present. In vitro studies of salinity tolerance of saprolegniaceous fungi have demonstrated that some representatives exhibit substantial resistance to salt stress. Te Strake (1959) described vegetative growth of several species at salinities as high as 22.5 parts per thousand (ppt), while Harrison and Jones (1971) observed growth of Saprolegnia

An Isolate of Saprolegnia Australis From Southeastern North Carolina

There are no known reports of the occurrence of Saprolegnia australis Elliott since its initial isolation (Elliott, 1968). Saprolegnia australis is prevalent, however, in small streams feeding Bradley Creek, Wilmington, North Carolina. The most striking dissimiliarity of the present isolate (UNC-W No. WlOb, ATCC No. 32940) from the type species is sporangium size (FIGS. 1-4). Elliott reported the median primary sporangium length to be 40-80 tm, while those of W-lOb are 189-243 t/m (median 70%). Secondary sporangia in W-lOb, like the type species, usually are short and arise by internal proliferation; but in W-lOb secondary sporangia up to 600 tm in length are not uncommon at the tips of robust hyphae (FIG. 5). In 6-da-old cultures several sporangia exhibited dictyoid spore discharge, a characteristic not noted by Elliott. Although W-lOb is clearly an isolate of S. australis several aspects of its sexual morphology serve to broaden the species concept. Neither the antheridial branches no antheridia are persistent (FIGS. 6-7) while the reverse was true in Elliotts isolates. Fertilization tubes were found in three cases in W-lOb, (e.g., FIG. 8), but none were noted by Seymour (1970) in preserved slides of the type culture. O6spheres are variable in size as in Elliotts isolates, the smaller ones being produced by budding of large o6spheres (FIGS. 9-12). Mature subcentric o6spores of greatly varying sizes thus can be found in the same o6gonium (FIG. 7), but