Effects of salinity on anatomical features and physiology of a semi-mangrove plant Myoporum bontioides

The effect of different concentrations of NaCl, 0, 100, 200, 300 and 400 mM, on the anatomical features and physiology of Myoporum bontioides was investigated. The photosynthetic rates (Pn) were significantly reduced by salt stress, with the lowest values at 400 mM NaCl. The content of malondialdehyde (MDA), proline and soluble sugar, as well as the activities of peroxidase (POD) and catalase (CAT) increased at the beginning, but became similar to the control as the experiment proceeded. The NaCl effect on superoxide dismutase (SOD) was different from the other parameters, with a significant reduction at 400 mM NaCl at Day 7. Salt glands were found in both upper and lower epidermis, and the ratios of the thickness of palisade to spongy mesophyll tissues increased with NaCl concentrations. The medullary ray was clearly damaged by NaCl at levels of 200 and 300 mM. These results demonstrated that M. bontioides could adapt to a relatively low salinity, and was not a halophilous species.

Zoospore chemotaxis of mangrove thraustochytrids from Hong Kong

Zoospores of mangrove isolates of Schizochytrium mangrovei KF6, KF7, KF12 (three strains), Thraustochytrium striatum KF9 and Ulkenia sp. KF13 were examined for their chemotactic responses to amino acids, carbohydrates, ethanol, and leaf extracts using a capillary root model. Most leaf extracts of mangrove plants and a marsh grass tested were shown to induce moderate chemotactic responses in zoospores of both S. mangrovei KF6 and Ulkenia sp. KF13. Of the remaining amino acids and carbohydrates evaluated, glutamic acid and pectin induced strong attraction in zoospores of S. mangrovei KF6 and Ulkenia sp. KF13, suggesting these are the major components in leaves which may be responsible for the chemotactic response of thraustochytrid zoospores in nature. Zoospores of T. striatum KF9, in general, showed a weak chemotactic response to all the tested compounds and extracts except cellulose, which elicited a moderate response. The ecological significance of the data presented is discussed.

Biodegradation of anthracene and benz[a]anthracene by two Fusarium solani strains isolated from mangrove sediments

An investigation was undertaken on the biodegradation of two kinds of polycyclic aromatic hydrocarbons (PAHs), anthracene (ANT) and benz[a]anthracene (BAA), by fungi isolated from PAH-contaminated mangrove sediments environment in Ma Wan, Hong Kong. ANT (50mg l(-1)) and BAA (20mg l(-1)), respectively, were added to mineral salt medium initially for screening of PAH-degrading fungi, and finally two fungal species capable of using ANT or BAA as the sole carbon source were isolated and identified as Fusariumsolani species. Removal of ANT and BAA reached 40% and 60% of the added amount, respectively, after 40 days of incubation. A total of six metabolites were isolated and characterized by solid phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC/MS), which indicate that F.solani degraded both ANT and BAA via their respective quinone molecules to generate phthalic acid. Free extracellular laccase was detected during the degradation process without detectable lignin peroxidase (LiP) and manganese-dependent peroxidase (MnP), suggesting that laccase might play an important role in the transformation of PAHs compounds.

Purification and characterization of an extracellular laccase from the anthracene-degrading fungus Fusarium solani MAS2

An extracellular laccase was purified from the culture medium of the non-white rot, anthracene-degrading fungal strain Fusarium solani MAS2. Both native PAGE and SDS-PAGE revealed one single band corresponding to a molecular weight of about 72 kDa. Treatment with endoglycosidase H reduced the molecular weight by 12%. The purified laccase maintained stable at pH 3-11 and up to 50 degrees C. The highest activity was detected at pH 3.0 and at 70 degrees C. The enzyme retained 46.2-97.2% of it activity in the presence of 20mM Pb(2+), Ni(2+), Cr(3+), and its activity was enhanced in the presence of 20mM Hg(2+). The laccase retained more than 50% of its activity in the presence of 5% acetone, acetonitrile, dimethyl sulphoxide (DMSO), ethanol and methanol. The kinetic constants (K(m) and k(cat)) showed that 2,6-dimethoxyphenol (DMOP) and 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt (ABTS) were the more effective substrates rather than catechol and guaiacol. The novel properties of this laccase suggest its potential for biotechnological and environmental applications.

Benzofuran derivatives from the mangrove endophytic Fungus Xylaria sp. (#2508)

Three metabolites, named xyloketal J (1), xyloester A (2), and xyloallenolide B (3), together with the known substituted dihydrobenzofuran (4) were isolated from the mangrove endophytic fungus Xylaria sp. (#2508). Structures were determined by spectroscopic methods, mainly 1D and 2D NMR.

1H and 13C NMR assignments for 6-demethylvermistatin and two penicillide derivatives from the mangrove fungus Guignardia sp. (No. 4382) from the South China Sea

One new compound 6-demethylvermistatin (1), together with two known compounds, the penicillide derivatives (2) and (3) were isolated from the mangrove fungus Guignardia sp. No. 4382 obtained from the South China Sea. Their structures were assigned using high-resolution electron ionization mass spectrometry(HREIMS), (1)H and (13)C NMR spectra, DEPT, and by 2D COSY, HMQC, and HMBC experiments. The absolute configuration of 1 was established by comparison of its CD with that of vermistatin.

(1)H and (13)C NMR assignments for five anthraquinones from the mangrove endophytic fungus Halorosellinia sp. (No. 1403)

We report the unambiguous assignments of the (1)H and (13)C NMR spectra of two new natural products, namely, 1,4,5,6,7,9-hexahydroxy-2-methoxy-7-methyl-5beta,9beta,8abeta, 6alpha,10aalpha-hexahydroanthracen-10 (10aH)-one (1) and 1,4,6-trihydroxy-2-methoxy-7-methylanthracene-9, 10-dione (2), together with three known anthraquinones. These compounds were all isolated from the marine endophytic fungus No. 1403 collected from the South China Sea. Compounds 3 and 4 were isolated from the marine fungus for the first time. The structures were elucidated by the spectroscopic methods 1D and 2D NMR including COSY, HMQC, HMBC and NOE, and HREIMS. In our cytotoxicity assays, compound 5 showed cytotoxicity toward KB and KBv-200 cells with IC(50) of 1.40 and 2.58 microg/ml, respectively. In addition, the plausible biogenic relationship of compounds 1, 2, 3 and 4 is discussed.

Cyclic peptides from an endophytic fungus obtained from a mangrove leaf (Kandelia candel)

Two new cyclic depsipeptides, 1962A (1) and 1962B (2), along with the three known cyclodipeptides cyclo-(Leu-Tyr) (3), cyclo-(Phe-Gly) (4), and cyclo-(Leu-Leu) (5) were isolated from the fermentation broth of the mangrove endophytic fungus (No. 1962) isolated from an old leaf of Kandelia candel collected in Hong Kong. Through spectroscopic experimentation, X-ray crystallographic analysis, and acid hydrolysis followed by chiral HPLC analysis, their structures were established to be 1962A, cyclo-(D-Leu-Gly-L-Tyr-L-Val-Gly-S-O-Leu) (1), and 1962B, cyclo-(D-Leu-Gly-L-Phe-L-Val-Gly-S-O-Leu) (2), respectively. Both of these new cyclo-depsipeptides were found to contain one d-amino acid. In the MTT bioassay, 1962A (1) showed weak activity against human breast cancer MCF-7 cells.

A new chloro-monoterpene from the mangrove endophytic fungus Tryblidiopycnis sp. (4275)

A new chloro-monoterpene (compound 1) and three known compounds, peroxyergosterol, uracil and methylisocoumarin, were isolated from the ethyl acetate extract of the fermentation broth of the mangrove endophytic fungus Tryblidiopycnis sp. (4275) obtained from Kandelia woody tissue from Mai Po, Hong Kong. Its structure was determined spectroscopically and by X-ray crystallographic analysis.

A comparison of airborne ergosterol, glucan and Air-O-Cell data in relation to physical assessments of mold damage and some other parameters

We report here a comparison of long duration air samples in 110 homes where the material collected on open faced filter cassettes was analyzed for beta 1,3-d glucan, ergosterol, cholesterol and endotoxin. These data were then compared to careful estimates of visible mold and Air-O-Cell data. All the values found except cholesterol were of a similar magnitude to values reported in the limited number of studies available. Glucan was measured with a factor G based assay of the Limulus Amebocyte Lysate followed by size exclusion chromatography. This showed that the majority of airborne glucan found in these houses was fungal in origin arising from both yeasts and intact spores, as well as hyphal and spore fragments. Hyphal and spore fragments together represented 16% of the intact spore counts but over a broad range. Correlations between airborne glucan were strong for ergosterol and visible mold. However, airborne ergosterol was more highly correlated to visible mold than glucan. Endotoxin and Air-O-Cell measurements were poorly or not related to the other measures in the study. This study provides confidence that long duration air samples of the toxin glucan and ergosterol are related to building damage.

PRACTICAL IMPLICATIONS

Some studies of damp buildings have shown a relationship between extent of water/mold damage and symptoms. This study compared long duration air samples for glucan and ergosterol to extent of visible mold in houses measuring also the nature of the glucans present. Both measures were highly correlated to extent of visible mold damage in the houses; ergosterol was somewhat superior. Spore counts or prevalence of Asp/Pen in Air-O-Cell samples was not related to extent of visible mold damage but the observation of hyphal fragments was more likely when mold damage was present. This indicates that rigorous assessment of mold damage is a useful measure.

The metabolites of the mangrove fungus Verruculina enalia No. 2606 from a salt lake in the Bahamas

Two metabolites enalin A (1) and B (2), together with hydroxymethyl furfural (3) and three cyclodipeptides (4, 5 and 6), were isolated from the mangrove fungus Verruculina enaria from a salt lake in the Bahamas. Their structures were determined by spectroscopic methods, mainly by 2D NMR spectroscopic analyses. A possible biosynthetic scheme to 1 and 2 is presented.

A Novel Compound Enniatin G from the Mangrove Fungus Halosarpheia sp. (strain #732) from the South China Sea

A novel cyclic depsipeptide, enniatin G, together with enniatins B and B4 were isolated from the mangrove fungus Halosarpheia sp.(strain 732) from the South China Sea. Their structures were determined by analysis of spectroscopic data, mainly two-dimensional nuclear magnetic resonance experiments. Enniatin G exhibited activity against Heps 7402, ED50 12mg/mL.

Tirispora, a new ascomycetous genus in the Halosphaeriales

The new genus Tirispora, with the single species Tirispora unicaudata, is described from an intertidal mangrove plant Acanthus ilicifolius in Hong Kong. The genus is compared with other genera with polar unfurling appendages: Aniptodera, Cucullosporella, Halosarpheia, Moana, Ophiodeira, and Trichomaris. Key words: ascus, Halosphaeriales, spore appendages, taxonomy, Tirispora gen.nov., ultrastructure.

Fungi and cellulolytic activity associated with decomposition of Bauhinia purpurea leaf litter in a polluted and unpolluted Hong Kong waterway

A survey of fungal succession on decomposing Bauhinia purpurea L. leaves in the unpolluted Tai Po Kau Forest Stream (TPKFS) and the animal waste polluted Lam Tsuen River (LTR) was carried out during the winter of 1988 and the summer of 1989. In situ cellulolytic activity of the TPKFS leaf litter was also investigated. Most of the 28 aquatic hyphomycete species found were cosmopolitan or frequently reported in temperate regions. Clavariopsis aquatica De Wildeman, Lunulospora cymbiformis Miura, and Flagellospora penicillioides Ingold were the dominant species at both sites. Among the 49 geofungi species recorded, lymaphilic species were commonly observed in the polluted LTR (e.g., Geotrichum candidum Link ex Leman, Fusarium oxysporum Schlecht, and Mucor racemosus Fres.) and lymaxenes in the TPKFS (e.g., Humicola spp., Trichoderma spp. and Gliocladium roseum Bain.). Species richness of aquatic hyphomycetes was higher in the TPKFS (27 species) than in the polluted LTR (14 species), whereas for the associated geofungi, it was higher in the LTR (35 species) than in the TPKFS (28 species). Conidial production was also higher in the TPKFS. Aquatic hyphomycetes and geofungi showed a complementary sequence of dominance in winter and summer, respectively, in the clean TPKFS. Higher cellulolytic activity occurred in the winter than the summer leaf litter. Key words: aquatic hyphomycetes, geofungi, leaf litter, pollution, cellulolytic activity.

Decomposition of Bauhinia purpurea leaf litter in a polluted and unpolluted Hong Kong waterway

Decomposition of Bauhinia purpurea L. leaves in litter bags submerged in the Tai Po Kau Forest Stream (TPKFS) and the Lam Tsuen River (LTR) was investigated during the winter of 1988 and the summer of 1989. At every collection, temperature, pH, turbidity, dissolved oxygen, and biological oxygen demand (BOD5) were measured. In winter, the organically enriched LTR was categorized as polluted based on BOD5, turbidity, and heterotrophic bacteria counts, whereas the TPKFS was always relatively clean. Weight loss of leaf litter at both sites was very rapid when compared with published values and exhibited a distinct seasonal pattern. The decomposition rate of leaf litter (using the single exponential decay model) varied linearly with mean water temperature. Carbon content of the leaf litter decreased during decomposition and was, as expected, negatively correlated with the percent ash content. Except in the first 2 weeks, the nitrogen content of decomposing leaf litter decreased with time at a rate correlated with the abundance of heterotrophic bacteria in winter leaf litter (insufficient data were available in summer). Based on the results of the winter study only, the decomposition of leaf litter seems to be suppressed in the polluted river. Key words: decomposition, carbon, nitrogen, water pollution, heterotrophic bacteria.