Lignocellulolytic enzyme profiles of edible mushroom fungi

One of the most economically-viable processes for the bioconversion of many types of lignocellulosic wastes is represented by edible mushroom cultivation. Lentinula edodes, Volvariella volvacea and Pleurotus sajor-caju are three important commercially cultivated mushrooms which exhibit varying abilities to utilise different lignocellulosics as growth substrate. Examination of the lignocellulolytic enzyme profiles of the three species show this diversity to be reflected in qualitative variations in the major enzymic determinants (i.e. cellulases, ligninases) required for substrate bioconversion. For example, L. edodes, which is cultivated on highly lignified substrates such as wood or sawdust, produces two extracellular enzymes which have been associated with lignin depolymerisation in other fungi, (manganese peroxidase and laccase). Conversely, V. volvacea, which prefers high cellulose-, low lignin-containing substrates produces a family of cellulolytic enzymes including at least five endoglucanases, five cellobiohydrolases and two -glucosidases, but none of the recognised lignin-degrading enzymes.J.A. Buswell, Y.J. Cai, S.T. Chang, J.F. Peberdy and S.Y. Fu are with the Department of Biology, The Chinese University of Hong Kong, Shatin, Hong Kong. J.A. Buswell and S.T. Chang are also with the Centre for International Services to Mushroom Biotechnology, The Chinese University of Hong Kong, Shatin, Hong Kong. J.F. Peberdy is also with the Department of Life Science, University of Nottingham, United Kingdom. S.Y. Fu is also with, and H.-s. Yu is with the Institute of Chemistry, Academia Sinica, Guangzhou, China.     

Mutagenesis of Protoplasts and Regeneration of Mycelium in the Mushroom Volvariella volvacea

Regenerating protoplasts were obtained from mycelial culture of the mushroom Volvariella volvacea by the action of the lytic enzyme Novozym 234 in the presence of 0.01 M phosphate buffer (pH 6.0) containing 0.6 M NaCl. Regeneration was found to be poor in liquid medium, but more than 50% regeneration was achieved on solid 2% agar medium overlaid with 0.5% agar. Protoplasts of V. volvacea were found to be highly sensitive to the killing action of both UV irradiation and N-methyl-N′-nitro-N-nitrosoguanidine. However, no morphological or auxotrophic mutants could be obtained from protoplasts by chemical mutagenesis. Four types of morphological mutants and one auxotrophic (adenine-negative) mutant were obtained from UV-irradiated protoplasts. The adenine-negative mutant of V. volvacea was found to be stable, not losing auxotrophy on repeated subculture.     

Degradation of tannins in spent coffee grounds by Pleurotus sajor-caju

Pleurotus sajor-caju PL27, a white rot fungus, degraded up to 87% of the tannins in spent coffee grounds as a solid substrate over 32 days. Degradation of tannins was enhanced if potato and dextrose were included. The potential nutritive value of the substrate as animal feed may be improved by this process.Yum-Shing Wong is with the Biology Department, Chinese University of Hong Kong, Shatin, NT, Hong Kong. Xun Wang is a visiting scientist from the Research Institute of Food and Fermentation Industry, People's Republic of China.     

Eating Metropolitaneity: Hong Kong Identity in yumcha

In Hong Kong, yumcha as a pervasive form of eating in the public has become an institution which epitomises the diversity and inclusiveness that Hong Kong people think are quintessential to the civility and economic achievement of the metropolis. It stands out particularly as a practice that has come to represent both locally and overseas a Hong Kong culture which has previously been characterised as residual of ‘Chinese tradition’ and ‘Western customs’, and hence is virtually non-existent. This paper looks at the consumption of metropolitaneity and the culturalisation of the heunggongyan or Hong Kong personal identity in the form, content and social relations involved in yumcha. It points to the significance of yumcha as a key to understanding a collective identity which has become more and more apparent as Hong Kong people vehemently try to establish a city with its own culture, first against the colonial grip and then the return of sovereignty to China in 1997.     

A description of the first intact Dwarf Sperm whale from the South China Sea and a review of documented specimens of the Kogiidae (Cetacea) from Hong Kong

Reports of the Dwarf Sperm whale (Kogia sima) in Chinese waters exist only for four specimens, which stranded along the coast of the East China Sea. Records of this species in the South China Sea consist of one skull noted as present in a Vietnamese ‘whale temple’. Recently recognized material in the biological sciences building of the University of Hong Kong, confirms the presence of both the Dwarf (K. sima) and the Pygmy (K. breviceps) Sperm whales in Hong Kong. In addition, close examination of Hong Kong stranding records reveals that of the four specimens identified as K. breviceps one is, in fact, K. sima. A comparison of the Hong Kong material, the holotype of K. sima and other Asian specimens of Kogia spp. affirms that most of the features already used elsewhere to distinguish the two species are reliable.     

A revision of post-war collections of Hong Kong Sematophyllaceae

Abstract

Six genera and 11 species of Sematophyllaceae are confirmed for the Hong Kong moss flora based on recent collections. One genus, Brotherella, and three species, Brotherella erythrocaulis, lsocladiella surcularis and Taxithelium instratum, are new to Hong Kong. Taxithelium batanense is a new synonym of T. oblongifolium. Sematophyllum japonicum, S. pulchellum and S. subhumile are treated as a species complex awaiting further revision. The report of Trichosteleum mammosum from Hong Kong needs confirmation.     

Carotenoid Mutants of Mucor circinelloides

The wild-type of the filamentous fungus Mucor circinelloides accumulates the yellow pigment β-carotene. At a continuous blue-light fluence rate of 0.1 W/m² the β-carotene content increases about eight fold over the dark controls. Among the mutants isolated after exposure of spores to either N-methyl-N'-nitro-N-nitrosoguanidine or ICR-170, a red mutant accumulating lycopene, white mutants accumulating phytoene and white mutants without carotenoids were found. The biosynthesis of carotenoids in M. circinelloides shows similarities with that of the fungus Phycomyces blakesleeanus such as the presence of mutants in the same structural genes and the induction by light of the pathway. However, negative end-product regulation by β-carotene on the biosynthetic pathway, as in Phycomyces, is absent in M. circinelloides. In contrast to Phycomyces carB and carR mutants, carotenoids in corresponding mutants of M. circinelloides are photoinduced.     

Purification and properties of β-amylase from Bacillus circulans S31

A thermotolerant -amylase was purified from Bacillus circulans S31 isolated from soil in Hong Kong. The purified enzyme has an M _r of 64 kDa and was stable at 50°C and pH 7.0 for 30 min. Its K _m for starch was 0.9 mg/ml with a V _max of 0.3 mg/min. It was not activated by any metal ion although sulphydrys reagents were inhibitory.H.S. Kwan, K.H. So and K.Y. Chan are with the Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong S.C. Cheng is with the Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic, Hung Hom, Hong Kong.     

Cross-species microarray hybridization to identify developmentally regulated genes in the filamentous fungus <Emphasis Type="Italic">Sordaria macrospora</Emphasis>

The filamentous fungus Sordaria macrospora forms complex three-dimensional fruiting bodies that protect the developing ascospores and ensure their proper discharge. Several regulatory genes essential for fruiting body development were previously isolated by complementation of the sterile mutants pro1, pro11 and pro22. To establish the genetic relationships between these genes and to identify downstream targets, we have conducted cross-species microarray hybridizations using cDNA arrays derived from the closely related fungus Neurospora crassa and RNA probes prepared from wild-type S. macrospora and the three developmental mutants. Of the 1,420 genes which gave a signal with the probes from all the strains used, 172 (12%) were regulated differently in at least one of the three mutants compared to the wild type, and 17 (1.2%) were regulated differently in all three mutant strains. Microarray data were verified by Northern analysis or quantitative real time PCR. Among the genes that are up- or down-regulated in the mutant strains are genes encoding the pheromone precursors, enzymes involved in melanin biosynthesis and a lectin-like protein. Analysis of gene expression in double mutants revealed a complex network of interaction between the pro gene products.     

VOLVARIELLA VOLVACEA AND ITS LIFE HISTORY

Volvariella volvacea (Bull. ex Fr.) Sing. is a large pileate edible fungus of the tropics and sub-tropics. It has two kinds of spores, one being the sexual basidiospores in tetrads and the other the asexual chlamydospores. Both monosporous and vegetative hyphae are multinucleate, and there are no clamp connections. Fifty monospores were isolated from two fruiting bodies, and were cultivated individually with four replicates under controlled laboratory conditions. On the average, 76% of the monosporous progenies were fertile. The fungus is homothallic. The development and life cycle of the fungus are described. The possible mechanisms of homothallism are also discussed.     

Identification of rice Allene Oxide Cyclase mutants and the function of jasmonate for defence against Magnaporthe oryzae

Two photomorphogenic mutants of rice, coleoptile photomorphogenesis 2 (cpm2) and hebiba, were found to be defective in the gene encoding allene oxide cyclase (OsAOC) by map‐based cloning and complementation assays. Examination of the enzymatic activity of recombinant GST–OsAOC indicated that OsAOC is a functional enzyme that is involved in the biosynthesis of jasmonic acid and related compounds. The level of jasmonate was extremely low in both mutants, in agreement with the fact that rice has only one gene encoding allene oxide cyclase. Several flower‐related mutant phenotypes were observed, including morphological abnormalities of the flower and early flowering. We used these mutants to investigate the function of jasmonate in the defence response to the blast fungus Magnaporthe oryzae. Inoculation assays with fungal spores revealed that both mutants are more susceptible than wild‐type to an incompatible strain of M. oryzae, in such a way that hyphal growth was enhanced in mutant tissues. The level of jasmonate isoleucine, a bioactive form of jasmonate, increased in response to blast infection. Furthermore, blast‐induced accumulation of phytoalexins, especially that of the flavonoid sakuranetin, was found to be severely impaired in cpm2 and hebiba. Together, the present study demonstrates that, in rice, jasmonate mediates the defence response against blast fungus.     

Rodent Diversity in a Highly Degraded Tropical Landscape: Hong Kong, South China

The diverse ecological roles played by different rodent species mean that the loss of some species and superabundance of others could potentially influence a wide range of ecological processes. Hong Kong (22° N, 114° E), with seven million people in a land area of 1100 km², could be considered a `worst case scenario' for the survival of mammalian diversity. Existing information on rodents in Hong Kong was compiled from previous published and unpublished studies, and additional trapping was conducted at 17 non-urban sites. The rodent fauna of modern Hong Kong consists of eight species of rats and mice (Bandicota indica, Mus caroli, M. musculus, Niviventer fulvescens, Rattus norvegicus, R. rattus, R. tanezumi, R. sikkimensis: Muridae), one porcupine (Hystrix brachyura: Hystricidae), and one recently introduced tree squirrel (Callosciurus erythraeus: Sciuridae). Six of the murids are urban or agricultural commensals, so only the porcupine and two murids, N. fulvescens and R. sikkimensis, are likely survivors of Hong Kong's pre-deforestation native rodent fauna. The two murids co-dominate in forest and shrubland, but can also move through grassland, which has probably enabled their survival through repeated cycles of fragmentation and regrowth. Additional forest rodents that may have inhabited Hong Kong in the past are tentatively identified from information on their recent distributions in the region. One possible ecological consequence of Hong Kong's depleted rodent fauna is a shift in the balance between seed predation and seed dispersal, in favor of the former.     

Distribution of toxigenic Bacillus cereus in rice samples marketed in Hong Kong

Eleven of 16 samples of rice on sale in rice shops and supermarkets in Hong Kong contained Bacillus cereus. Although B. cereus counts did not exceed 100 bacteria/g in most of the positive samples, a sample of Thai red rice and a poor quality rice originating from China contained between 300 to 1000 cells/g and 10⁴ to 2×10⁵ cells/g, respectively. Nine strains produced an enterotoxin responsible for the diarrhoeal-type B. cereus food poisoning and seven of these strains also produced a haemolysin (haemolysin BL), a dermonecrotic vascular permeability factor which may be a virulence determinant in diarrhoeal illness caused by this bacterium.P.K. Lee and J.A. Buswell are with the Department of Biology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong; K. Shinagawa is with the Department of Veterinary Medicine, Iwate University, Iwate, Japan.     

Mycorrhizal associations in Hong Kong Fagaceae

A rapid method of screening has been devised whereby the large seeds (acorns) of Castanopsis, Lithocarpus and Quercus growing in Hong Kong can be germinated in the presence of a variety of known mycorrhizal fungi and observations made on the initiation of host/fungal associations. Early stages of Hartig net formation could be detected in bleached roots, and an observation was made on the antibiotic activity of the mycorrhizal fungus, Pisolithus tinctorius. The method offers a simple and effective means of assessing the potential of fungi to form mycorrhizal associations under non-sterile conditions.     

Three new species of Annulatascus (Ascomycetes) from Hong Kong freshwater habitats

 Annulatascus joannae, A. lactus, and A. tropicalis are described and illustrated from decaying woody substrata in freshwater habitats in Hong Kong. Annulatascus joannae is distinguished by ellipsoidal and thick-walled ascospores whereas A. lacteus has milky ascomata and A. tropicalis has relatively large, fusiform, 1–3-septate ascospores. Annulatascus biatriisporus is reported as a new record in Hong Kong. A key to and a synoptic table of Annulatascus species are provided. Received: December 14, 2001 / Accepted: July 5, 2002 Acknowledgments C.K.M. Tsui and V.M. Ranghoo are grateful to The University of Hong Kong for the award of postgraduate studentships. A.Y.P. Lee, M.H. Ng, and M.Y. Chan are thanked for photographic and technical assistance. Correspondence to:C.K.M. Tsui     

香港茜草科植物新记录

查阅馆藏植物标本,有3种茜草科植物：丹草（Hedyotis herbacea）、小耳草（H.pumila）和蕴璋耳草（Scleromitrion koanum）为香港新记录。这些资料为香港的生物多样性工作提供了基础数据。     

A mutant in Lycopersicon esculentum Mill. with highly reduced VA mycorrhizal colonization: isolation and preliminary characterisation

This paper reports the successful isolation and preliminary characterisation of a mutant of Lycopersicon esculentum Mill. with highly reduced vesicular-arbuscular (VA) mycorrhizal colonization. The mutation is recessive and has been designated rmc . Colonization by G. mosseae is characterised by poor development of external mycelium and a few abnormal appressoria. Vesicles were never formed by this fungus in association with the mutant. Gi. margarita formed large amounts of external mycelium, complex branched structures and occasional auxiliary cells. Small amounts of internal colonization also occurred. Laser scanning confocal microscopy (LSCM) gave a clear picture of the differences in development of G. intraradices and Gi. margarita in mutant and wild-type roots and confirmed that the fungus is restricted to the root surface of the mutants. The amenability of tomato for molecular genetic characterisation should enable us to map and clone the mutated gene, and thus identify one of the biochemical bases for inability to establish a normal mycorrhizal symbiosis. The mutant represents a key advance in molecular research on VA mycorrhizal symbiosis.     

Nutrient flow in a major urban settlement: Hong Kong

A nutrient balance is established for the contemporary urban ecosystem of Hong Kong. The flow of nutrients in the Hong Kong food system in particular is examined, including current and potential nutrient recycling patterns. Losses of nutrients in food for human consumption are found to be up to 20% for major nutrients. The flow of mineral phosphorus in the Hong Kong food system is examined in detail. About 3600 tonnes of phosphorus are lost from the Hong Kong food system each year. A comparison is made between the land-based forage area demand of the Hong Kong population and a similar-sized Western population, that of Sydney, Australia. It is estimated that the average Hong Kong person consumes a diet which requires only half the land area needed to produce the diet of the average Sydney person. However, Hong Kong relies on the ocean for 25% of its animal protein supply compared with 2.5% for Sydney. Patterns of food production and nutrient recycling are proposed, with the aim of optimizing resource utilization in close association with contemporary urban settlements.     

Characterization of Mycorrhizas Formed by Glomus sp. on Roots of Hypernodulating Mutants of Lotus japonicus

Lotus japonicus hypernodulating mutants, Ljsym78-1 and Ljsym78-2, by the arbuscular mycorrhizal fungus Glomus sp. was characterized. The mutants are defective in systemic autoregulation of nodulation and nitrate inhibition, and form an excess of nodules and lateral roots. The percent root length colonized by the arbuscular mycorrhizal fungi was significantly higher for the mutant than wild-type roots. Detailed assessment of the colonization indicated that the percentage of colonization by arbuscules was increased, but that by external hyphae, internal hyphae and vesicles was decreased, in the mutant roots compared with the wild-type. The succinate dehydrogenase activity of arbuscules, external hyphae and internal hyphae showed similar trends. In addition, the majority of individual arbuscules that formed on the mutant roots had a well-developed and seemingly tough morphology. The results suggest that mutation at the Ljsym78 locus positively stimulates the growth and activity of arbuscules, but leads to reduced growth and activity of hyphae. We report the first identification of Lotus japonicus mutants that show significantly increased arbuscule formation and termed these mutants Arb⁺⁺. Received 8 August 2000/ Accepted in revised form 19 October 2000     

Isolation and characterization of restriction endonuclease EclHKI from an Enterobacter cloacae strain

An Enterobacter cloacae strain, producing restriction enzyme EclHKI, was isolated from a decaying potato. The enzyme is an isoschizomer of Eam1105I, which recognizes and cleaves GACNNN!NNGTC. EclHKI was produced at high activity (4×10⁴ U/g wet cells) and was purified from contaminants which interfere with restriction digestion by passing the cell lysate through DEAE-Sephacel and heparin columns. Activity was optimal at 37°C in a medium salt buffer.H.-Y. Chan, Y.-C. Chan and P.-C. Shaw are with the Department of Biochemistry, The Chinese University of Hong Kong, Hong Kong: K.-M. Kam is with the Institute of Pathology, Sai Ying Pun Jockey Club Clinic, Hong Kong.