Diversity of aquatic hyphomycetes in the aquatic ecosystems of the Western Ghats of India

Relationships between physico-chemical factors of waters, riparian vegetation, altitude and species richness of the hyphomycete communities in six rivers and a sulfur spring in the Western Ghats of Karnataka were analysed statistically. Linear regression and correlation between log fungal species and riparian vegetation was highly significant. The similarity in the fungal diversity between different rivers and the sulphur spring was evaluated by Sorensen's index. Generally, the indices of similarity in the mycoflora between the streams were high. However, in the streams of Lakya, Bhadra, Ranganathittu bird sanctuary and the sulfur spring the indices of similarity were low compared with the rest of the water systems. The low pH, low oxygen concentration, hardness, high iron, high temperature and sulfide contents of the waters of these streams are thought to be the reasons for the differences in these streams. Anguillospora longissima, Helicomyces roseus, Lunulospora curvula, Triscelophorus monosporus and Wiesneriomyces laurinus were found to be the most abundant species.     

Colonization pattern of aquatic hyphomycetes on leaf packs in subtropical stream

Steralized leaf pieces of eight plants (Eucalyptus rostrata, Phoenix dactylifera, Phragmites australis, Musa nana, Salix subserrata, Cyperus alopecuroides, Ricinus communis and Eichhornia crassipes) were submerged in the Nile stream. Thirty-nine species of aquatic hyphomycetes were colonized on the plant leaves. Eucalyptus was the best substratum (30 species) for colonization by aquatic hyphomycetes. Phoenix (14 species), Phragmites (11 species), Salix (9 species), Musa (8 species), Ricinus and Cyperus (6 species) were also good substrata for aquatic hyphomycetes colonization. Echhornia (aquatic plant) was not suitable for aquatic hyphomycetes colonization. Alatospora acuminata, Triscelophorus monosporus and Tetracladium marchalianum were found to be the major colonizers on all leaf materials. Temperature and dissolved oxygen were the highest physico-chemical parameters affecting the aquatic hyphomycetes colonization. These results indicate that aquatic hyphomycetes have been shown to be successful colonizers on plants leaf in river Nile in Egypt as subtropical region. This revised version was published online in June 2006 with corrections to the Cover Date.     

Raised water temperature lowers diversity of hyporheic aquatic hyphomycetes

1. The hyporheic zone of a permanent first‐order stream was divided into a treatment and a control section using a 1 m deep sheet‐metal barrier. During a 4‐month pre‐treatment period, water temperatures in two transects of the two sections were not different. Upon heating, the water temperature in the treatment transect increased by an average of 4.3 °C over values in the control transect. 2. Eleven bimonthly core samples were taken from a treatment and a control transect, and recovered CPOM was classified as twigs, wood, grass, roots, cedar and deciduous leaves. 3. In both transects, twigs were the most common and deciduous leaves the least common substrates. The number of leaf fragments declined significantly in the heat‐treated transect. 4. Diversity and frequencies of occurrence of aquatic hyphomycetes were highest on leaves and lowest on grass and wood. On leaves, their frequency of occurrence was higher in control than in treatment samples. 5. Preliminary results with amplified and cloned 18S DNA sequences revealed many fungal taxa with high affinities to Basidiomycota, particularly to Limnoperdon incarnatum. 6. By itself, higher water temperature due to global warming is likely to lower the availability of substrates for, and therefore the occurrence of, aquatic hyphomycetes.     

Study of the Effect of Different Techniques on Diversity of Freshwater Hyphomycetes in the River Nile (Upper Egypt)

Four different techniques were applied, lead mapping of Eucalptus rostrata; randomly leaf sampling; Millipore filtration; spores in foam, for the study of aquatic hyphomycets communities in the River Nile. Triscelophorus monlosporus, Anguilospora longissima, Flagellospora curvula and Tetracladium marchalianum were the dominant species in all the techniques used. Aquatic hyphomycetes diversity was high by using leaf mapping (23 species) and randomly leaf sampling (30 species) but it was low by using Millipore filtration (11 species) and spores in foam (8 species) techniques.     

Effects of temperature and light on growth and sporulation of aquatic hyphomycetes

Nine isolates of the aquatic hyphomycetes Dactylella aquatica, Flagellospora penicillioides, Flagellospora saccata, Helicomyces sp., Lunulospora curvula, Phalangispora constricta, Tetracladium setigerum, Vermispora cauveriana and Wiesneriomyces laurinus were incubated at different temperatures (5–35 °C) to study their growth on MEA medium. Maximum growth was observed between 20 and 30 °C. Growth rate was highest in Vermispora cauveriana and lowest in Tetracladium setigerum. Colonies on submerged leaves showed maximum spore production at 25 °C. Light was confirmed as a stimulus to sporulation.     

Effects of cadmium,copper, and zinc on growth and thiol content of aquatic hyphomycetes

The effects of cadmium, copper, and zinc on the growth of ten strains ofaquatic hyphomycetes were investigated. On a solid medium, Cd and Cu reducedradial growth of most strains by 50% at concentrations between150–400 µM; in a liquid medium, the strains were more sensitive.The inhibitory effects of zinc were much less severe. Two isolates(Articulospora tetracladia and Tetracladium marchalianum) from a copper-minestream were more resistant against copper than conspecific strains from anon-polluted stream. Heliscus lugdunensis and Varicosporium elodeaeresponded to Cd exposure, but not to Cu or Zn exposure, by increasedsynthesis of SH-containing compounds. Glutathione levels showed a unimodalresponse to increasing Cd and Zn exposure. With copper, glutathionedecreased at intermediate levels of contamination. In the presence of Cd, H. lugdunensis synthesized several unknown sulfur-rich substances that wereabsent or produced at reduced rates in control cultures.     

Enzymatic studies of the extracellular mucilage of two aquatic hyphomycetes,Lemonniera aquatica andMycocentrospora filiformis

The effect of three carbohydrate-digesting enzymes, β-glucuronidase, lyticase and α-mannosidase and three proteolytic enzymes, α-chymotrypsin, papain and pronase E, on the strength of conidial attachment ofLemonniera aquatica andMycoentrospora filiformis was determined using the LH_Fowler cell Adhesion Measurement Module. Carbohydrate-digesting enzyme treatments showed significant differences in number of attached and detached, conidia versus control samples; little or no effect was observed for the proteolytic enzymes. Scanning and transmission electron microscopy showed different degrees of mucilage digestion by the carbohydrate-digesting enzymes on the germ hyphae, hyphae subtending appressoria, and appressoria of the two species. The loss of mucilage integrity and decrease in mucilage thickness were more pronounced on the hyphal sheaths than on the appressorial sheaths. Lyticase caused the most severe damage to the mucilage and cytoplasm of both fungi, particularlyL. aquatica. β-Glucuronidase and α-mannosidase exhibited more effective mucilage digestion onM. filiformis than onL. aquatica. Results indicate that the mucilage of the two species is mainly polysaccharide, containing more β-1,3-glucans than β-glucuronide and α-mannosyl residues. Variability of mucilage composition exists between these species and also between different structures of the same fungus.     

Cell-wall-degrading enzymes of aquatic hyphomycetes: a review

Reports of cell-wall-degrading enzymes of aquatic hyphomycetes are reviewed, including pectinases, cellulases, hemicellulases, laminarinases and chitinases and the ability of these fungi to degrade lignin and straw. New evidence of enzymic activity is presented for 14 species.     

Diversity and activity of aquatic fungi under low oxygen conditions

1. The objective was to test whether a decrease in oxygen concentration in streams affects the diversity and activity of aquatic hyphomycetes and consequently leaf litter decomposition. 2. Senescent leaves of Alnus glutinosa were immersed for 7 days in a reference stream, for fungal colonization, and then incubated for 18 days in microcosms at five oxygen concentrations (4%, 26%, 54%, 76% and 94% saturation). Leaf decomposition (as loss of leaf toughness), fungal diversity, reproduction (as spore production) and biomass (ergosterol content) were determined. 3. Leaf toughness decreased by 70% in leaves exposed to the highest O₂ concentration, whereas the decrease was substantially less (from 25% to 45%) in treatments with lower O₂. Fungal biomass decreased from 99 to 12 mg fungi g⁻¹ ash‐free dry mass on exposure to 94% and 4% O₂ respectively. Sporulation was strongly inhibited by reduction of dissolved O₂ in water (3.1 × 10⁴ versus 1.3 × 10³ spores per microcosms) for 94% and 4% saturation respectively. 4. A total of 20 species of aquatic hyphomycetes were identified on leaves exposed to 94% O₂, whereas only 12 species were found in the treatment with 4% O₂ saturation. Multidimensional scaling revealed that fungal assemblages exposed to 4% O₂ were separated from all the others. Articulospora tetracladia, Cylindrocarpon sp. and Flagellospora curta were the dominant species in microcosms with 4% O₂, while Flagellospora curvula and Anguillospora filiformis were dominant at higher O₂ concentrations. 5. Overall results suggest that the functional role of aquatic hyphomycetes as decomposers of leaf litter is limited when the concentration of dissolved oxygen in streams is low.     

Factors affecting the distribution of lignicolous marine fungi in Hong Kong

An investigation into the effect of environmental factors on the general distribution and occurrence of lignicolous marine fungi using submerged blocks of pine (Pinus massoniana Lamb.) and teak (Tectona grandis L.) was carried out for 18 months in the coastal waters of Hong Kong. Five test sites, with environmental conditions varying from estuarine to oceanic, and from polluted to non-polluted, were selected. During each collection, salinity, temperature, pH, dissolved oxygen, biochemical oxygen demand, nitrate-nitrogen, inorganic phosphate-phosphorus and light transmission were measured. A total of 51 species of fungi were recorded among which only 28 were either obligate or facultative marine forms. Neither the general distribution pattern nor the distribution of the more frequent fungi could be solely accounted for by differences in salinity at the test sites and it is suggested that other ecological factors such as heavy sediments in the waters, low pH, and the presence of an abundant source of inocula may be important.     

Laccase activity from the fungus Trametes hirsuta using an air-lift bioreactor

AIM: To produce high laccase activities from the white-rot fungus Trametes hirsuta in an in-house air-lift bioreactor (ALB). METHODS AND RESULTS: Trametes hirsuta was grown in a 6-l ALB. A fed-batch strategy with glycerol as an addition resulted in maximum laccase activity of 19,400 U l(-1), which was the highest reported from the fungus. CONCLUSION: The ALB configuration with additional glycerol resulted in high laccase activities. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides useful information on how to produce high concentrations of laccase.     

Early stages of leaf decomposition are mediated by aquatic fungi in the hyporheic zone of woodland streams

1. Leaf litter constitutes the major source of organic matter and energy in woodland stream ecosystems. A substantial part of leaf litter entering running waters may be buried in the streambed as a consequence of flooding and sediment movement. While decomposition of leaf litter in surface waters is relatively well understood, its fate when incorporated into river sediments, as well as the involvement of invertebrate and fungal decomposers in such conditions, remain poorly documented. 2. We tested experimentally the hypotheses that the small interstices of the sediment restrict the access of the largest shredders to buried organic matter without compromising that of aquatic hyphomycetes and that fungal decomposers in the hyporheic zone, at least partly, compensate for the role of invertebrate detritivores in the benthic zone. 3. Alder leaves were introduced in a stream either buried in the sediment (hyporheic), buried after 2 weeks of exposure at the sediment surface (benthic‐hyporheic), or exposed at the sediment surface for the entire experiment (benthic). Leaf decomposition was markedly faster on the streambed surface than in the two other treatments (2.1‐ and 2.8‐fold faster than in the benthic‐hyporheic and hyporheic treatments, respectively). 4. Fungal assemblages were generally less diverse in the hyporheic habitat with a few species tending to be relatively favoured by such conditions. Both fungal biomass and sporulation rates were reduced in the hyporheic treatment, with the leaves subject to the benthic‐hyporheic treatment exhibiting an intermediate pattern. The initial 2‐week stage in the benthic habitat shaped the fungal assemblages, even for leaves later subjected to the hyporheic conditions. 5. The abundance and biomass of shredders drastically decreased with burial, except for Leuctra spp., which increased and was by far the most common leaf‐associated taxon in the hyporheic zone. Leuctra spp. was one of the rare shredder taxa displaying morphological characteristics that increased performance within the limited space of sediment interstices. 6. The carbon budgets indicated that the relative contributions of the two main decomposers, shredders and fungi, varied considerably depending on the location within the streambed. While the shredder biomass represented almost 50% of the initial carbon transformed after 80 days in the benthic treatment, its contribution was <0.3% in the hyporheic one and 2.0% in the combined benthic‐hyporheic treatment. In contrast, mycelial and conidial production in the permanently hyporheic environment accounted for 12% of leaf mass loss, i.e. 2–3 times more than in the two other conditions. These results suggest that the role of fungi is particularly important in the hyporheic zone. 7. Our findings indicate that burial within the substratum reduces the litter breakdown rate by limiting the access of both invertebrate and fungal decomposers to leaves. As a consequence, the hyporheic zone may be an important region of organic matter storage in woodland streams and serve as a fungal inoculum reservoir contributing to further dispersal. Through the temporary retention of litter by burial, the hyporheic zone must play a significant role in the carbon metabolism and overall functioning of headwater stream ecosystems.     

Isolation and partial purification of fungal ligninolytic enzymes from the forest soil fungi isolated from Bhadra Wildlife Sanctuary

Screening was done for the isolation of effective lignin degraders from the forest soil samples, by providing lignin as a carbon source through the enrichment method, which leads to the isolation of 8 effective fungal isolates among 14 isolates. Submerged fermentation was done for the production of ligninolytic enzymes with the effective microorganisms by providing Guiaicol as a carbon source. The assay of laccase, lignin peroxidise activity and specific activity was done after the incubation intervals of 2, 4, 6, 7, 8, 10 and 12 days at 27±2℃ under shake culture condition. Partially purified protein content was estimated by using Lowry＇s method. Pleurotus sp. and Phanerochaetae chrysosporium are more effective at the 2nd and 7th days of incubation for the production of laccase and lignin peroxidases among the effective isolates.     

Acanthophysis-like structures from wood submerged in freshwater streams in the tropics

Acanthophysis-like structures which commonly occur on submerged wood in the tropics are described and illustrated at the light microscope level. These are produced on fibre-like or rope-like strands and produce numerous detachable spinulose cells at their ends. These cells lack contents, do not germinate, and do not appear to be dispersal propagules. The acanthophysis-like structures may function as rhizomorphs enabling the fungus to colonize adjacent woody tissue, or serve to uptake oxygen from the water and these possibilities are discussed.     

Polyester-degrading actinomycetes isolated from the Touchien River of Taiwan

Actinomycete strains were isolated from upstream and downstream regions of the Touchien River in Taiwan and screened for the ability to degrade poly(ethylene succinate) (PES), poly(ε-caprolactone) (PCL) and/or poly(β-hydroxybutyrate) (PHB) by the clear-zone method. Out of 305 isolates 135 isolates were PHB-degraders (44.2%), 83 isolates were PCL-decomposers (27.2%), and 64 isolates could degrade PES (21.0%). Furthermore, 46 isolates could degrade both PHB and PCL (15%), 39 isolates could degrade both PHB and PES (12.8%), and 12 isolates could degrade the three polyesters used in this study. Based on the appearance of isolates, the major isolates belong to the Streptomyces genus (91.9%) and Micromonospora genus (8.1%).     

Leaf litter decomposition and microbial activity in nutrient-enriched and unaltered reaches of a headwater stream

SUMMARY 1. Decomposition of red maple ( Acer rubrum ) and rhododendron ( Rhododendron maximum ) leaves and activity of associated microorganisms were compared in two reaches of a headwater stream in Coweeta Hydrologic Laboratory, NC, U.S.A. The downstream reach was enriched with ammonium, nitrate, and phosphate whereas the upstream reach was not altered.
2. Decomposition rate, microbial respiration, fungal and bacterial biomass, and the sporulation rate of aquatic hyphomycetes associated with decomposing leaf material were significantly higher for both leaf types in the nutrient-enriched reach. Species richness and community structure of aquatic hyphomycetes also exhibited considerable changes with an increase in the number of fungal codominants in the nutrient-enriched reach.
3. Fungal biomass was one to two orders of magnitude greater than bacterial biomass in both reaches. Changes in microbial respiration rate corresponded to those in fungal biomass and sporulation, suggesting a primary role of fungi in leaf decomposition.
4. Nutrient enrichment increased microbial activity, the proportion of leaf carbon channelled through the microbial compartment and the decomposition rate of leaf litter.     

The development of a Biotic Pollution Index for the River Nile in Egypt

This article describes the development of a Nile Biotic Pollution Index (NBPI) for the River Nile in Egypt. Chemical data were collected from 30 locations along the Nile from Aswan to Cairo and 21 sites within the river delta, incorporating a range of conditions from unpolluted to grossly polluted. Seven chemical variables were used to calculate a Nile Chemical Pollution Index (NCPI) for each site. Biological data were collected primarily using Artificial Substrate Samplers (ASS). The UK developed, Biological Monitoring Working Party (BMWP) biotic index and the BMWP-ASPT were applied to the data. A Nile Biotic Pollution Index (NBPI) and the NBPI-ASPT were obtained by incorporating more of the Nile taxa. There were highly significant regressions (P < 0.001) for both the UK and the Nile Pollution Index scores with the NCPI for the whole river. The modification of the UK indices improved the Nile Indices increasing the number of taxa recorded from 29 to 43 and the total number of recorded taxon occurrences from 377 to 490. The Nile Indices provided better discrimination at both ends of the pollution spectrum. The NBPI-ASPT was best for the river as a whole, and particularly for the river from Aswan to Cairo. The NBPI was much better in the delta than from Aswan to Cairo. These differences in performance were attributed to the fact that the NBPI-ASPT excludes information on taxon diversity. In clean waters there was a wide range of NBPI score suggesting that the biodiversity of taxa is dependent on other aspects of habitat quality. Conversely in the polluted delta the high score of an individual taxon is critical for the NBPI-ASPT as it may have a distorting effect. As the NBPI-ASPT was the most consistent biotic index it is recommended as the regular biological assessment and regulatory tool for Egypt to meet the requirements of the Convention for Biodiversity. Handling editor: R. Norris     

改构的野生革耳漆酶基因在毕赤酵母中的表达和活性鉴定

在野生革耳漆酶的cDNA序列3’端添加15个核苷酸后得到突变基因lccT。将其克隆入表达载体pPICZαA,重组质粒pPICZαA／lccT经PmeⅠ线性化,电击转化毕赤酵母X-33细胞。经过菌落PCR鉴定的转化子pPICZαA／lccT—X一33在甲醇诱导后分泌表达活性重组漆酶LCCT,比未添加该段序列的野生革耳漆酶基因lcc在毕赤酵母中表达的活性提高2倍多。其培养液上清经凝胶过滤层析和离子交换层析后,得到了电泳纯的漆酶蛋白,以ABTS为底物在pH4．5时测得比活为3．68U／mg。根据SDS-PAGE测定的重组漆酶LCCT的表观相对分子质量为62600。     

Preliminary study of the aquatic Oligochaeta of the Changjiang (Yangtze) River

The aquatic oligochaetes in mainstream of the Changjiang River have not been studied previously. Since 1983, benthic samples have been collected mainly from mid-upper reach of the river. Altogether 19 species belonging to 4 families of the Oligochaeta were found. Among them, Nais inflata is the commonest species throughout the river, whereas Nais sp., Arcteonais lomondi, Limnodrilus silvani, Rhyacodrilus riabuschinskii and Telmatodrilus sp. ae recorded from China for the first time.Quantitatively, the aquatic oligochaetes constitute the majority of zoobenthos in the mainstream. In 1984, the standing crop of the Tubificidae was 231–343 ind·m^-2 in density and 0.73–0.97 g·m^-2 (wet weight) in biomass, and that of the Naididae was 21–4982 ind·m^-2 and 0.003–1.75 g·m^-2 (wet weight) respectively.