The Influence of pH on Biodeterioration of a Tropical Timber Exposed to Mixed Cultures of Biocontrol and Wood-Rot Fungi

A laboratory investigation of the decay control potentials of Trichoderma viride and Penicillium sp. on the deterioration of obeche wood (Triplochiton scleroxylon). buffered at various pH. by wood-rot fungi ( Gloeophyllum sp. and Gloeophyllum sepiarium ), was carried out. Biomass determinations in carboxylmethyl cellulose broth at various pH showed that the biocontrol fungal strains exployed grew better as the pH approached neutral while the reverse was true for the wood-rot fungi. Deterioration of wood (buffered at various pH) simultaneously inoculated with the biocontrol and wood-rot fungi was more markedly reduced towards neutral pH than at lower pH values. Decay begun in wood initially infested with rot fungi before inoculation with biocontrol fungi was virtually halted at neutral pH. which was not the case in lower pH (2 and 3) buffered wood simultanecously inoculated with biocontrol and wood-rot fungi. A killing effect was indicated when the rot fungi failed to appear on potato–dextrose agar from interior sections of the wood blocks. Manipulation of pH may prove important in biological control of wood decay.     

Botryosphaeria dothidea and Other Fungi Associated with Excoriose and Dieback of Grapevines in Portugal

In a study of fungi associated with symptoms of excoriose in Portugal, the most prevalent ones were found to be Botryosphaeria dothidea and Phomopsis viticola. In artificial inoculations, these two fungi infected grapevines causing dark lesions on the shoots and bud mortality. They were re-isolated from the shoot lesions and necrotic buds. Two further species of Botryosphaeria , namely B. obtusa and B. stevensii , were also isolated and they caused small lesions on wounded shoots but did not infect unwounded shoots. B. dothidea was also isolated from grapevines with a dieback of the trunk. These isolates were more virulent on young shoots and one-year-old canes than the ones from grapevines with excoriose.     

Enzyme Immunoassay of Herbicide Decomposition by Soil and Wood Decay Fungi

The effect of herbicide atrazine was studied on the growth and development of a number of soil and wood decay fungi: white-rot basidiomycetes (Cerrena maxima, Coriolopsis fulvocenerea, and Coriolus hirsutus), thermophilic micromycetes from self-heating grass composts (cellulolytic fungus Penicilliumsp. 13 and noncellulolytic ones Humicola lanuginosaspp. 5 and 12), and mesophilic phenol oxidase-producing micromycete Mycelia sterilia INBI 2-26. Detection of atrazine in liquid fungal cultures was performed by using the enzyme immune assay technique. Both stimulation (Humicola lanuginosa 5) and suppression (Humicola lanuginosa 12 and Penicillium sp. 13) of fungal growth with atrazine were observed on solid agar media. HyphomyceteMycelia sterilia INBI 2-26 was almost insensitive to the presence of atrazine. Neither of the thermophilic strains was capable of atrazine consumption in three-week cultivation. In contrast with that, active laccase producers Cerrena maxima, Coriolopsis fulvocenerea, and Coriolus hirsutus consumed up to 50% atrazine in 5-day cultivation in the presence of the xenobiotic and at least 80–92% in 40 days. Mycelia steriliaINBI 2-26, which also forms extracellular laccase, also consumed up to 70% atrazine in 17 days. The degree of atrazine consumption depended on the term of its addition to the fungal culture medium.     

Inhibition and Stimulation Effects in Communities of Wood Decay Fungi: Exudates from Colonized Wood Influence Growth by Other Species

The effects of exudates from uncolonized and from partly decayed beech wood on the extension rates of 16 later stage decay fungi were investigated. The partly decayed wood had been colonized by the pyrenomycete Eutypa spinosa, or the basidiomycetes Fomes fomentarius, Stereum hirsutum, and Trametes versicolor, all known as common early decay agents in European beech forests. Sterilized wood pieces were placed onto 0.5% malt agar, opposite to small agar plugs containing the test fungi. The latter showed very variable and species-specific growth responses to the various wood types. The presence of uncolonized wood stimulated extension rates in many species, whereas the four previously decayed wood types had variable stimulatory or inhibitory effects. Wood decayed by S. hirsutum resulted in reduced extension rate, delayed growth, or total inhibition in the majority of species, thus it is suggested that this species uses secondary metabolites in a defensive strategy. A single species was, however, stimulated in the presence of S. hirsutum-decayed wood. In contrast, the presence of wood decayed by F. fomentarius was stimulatory to 45% of the species. The other previously decayed wood types generally resulted in more variable responses, depending upon species. The results are discussed in an ecological context and it is suggested that the exudates from the partly decayed wood that are responsible for the reported effects may function as infochemicals, structuring microbial communities in wood.     

Improved Colorimetric Determination of Cell Wall Chitin in Wood Decay Fungi

The Svennerholm modification of the Elson-Morgan method for glucosamine analysis was evaluated for its applicability to the rapid determination of chitin in wood decay fungi. The evaluation included extent of chromogen interference, sensitivity, color stability, and hydrolysis conditions for maximum release of glucosamine from fungal cell walls. With our further modification, the Svennerholm method was shown to be suitable for rapid quantitative determination of fungal chitin without chromatographic separation of hydrolysate chromogens.     

Concomitant Antibiotic and Mercury Resistance Among Gastrointestinal Microflora of Feral Brook Trout, Salvelinus fontinalis

Twenty-nine bacterial isolates representing eight genera from the gastrointestinal tracts of feral brook trout Salvelinus fontinalis (Mitchell) demonstrated multiple maximal antibiotic resistances and concomitant broad-spectrum mercury (Hg) resistance. Equivalent viable plate counts on tryptic soy agar supplemented with either 0 or 25?μM HgCl₂ verified the ubiquity of mercury resistance in this microbial environment. Mercury levels in lake water samples measured 1.5?ng?L^?1; mercury concentrations in fish filets ranged from 81.8 to 1,080?ng?g^?1 and correlated with fish length. The presence of similar antibiotic and Hg resistance patterns in multiple genera of gastrointestinal microflora supports a growing body of research that multiple selective genes can be transferred horizontally in the presence of an unrelated individual selective pressure. We present data that bioaccumulation of non-point source Hg pollution could be a selective pressure to accumulate both antibiotic and Hg resistant bacteria.     

丽江古城建筑物梁柱腐朽真菌鉴定

通过形态观察和分子生物学技术,对采集自丽江古城的建筑物梁柱上的木腐菌进行鉴定。结果显示,引起丽江建筑物梁柱褐色腐朽的真菌为绵腐卧孔菌(Postia placenta)。同时提出相应的防治建议,以期尽可能地降低丽江古城建筑物的安全隐患。     

The Influence of Competition between Tropical Fungi on wood colonization in Streams

apd: 26 October 2000     

霍山石斛与内生真菌共培养体系的建立

将霍山石斛试管苗与内生真菌(SH-01菌株)共生培养,测定其生长状态,筛选最佳共生培养基。研究该培养体系下内生真菌对石斛试管苗生长和移栽成活率的影响。结果表明,适合共生培养基为1/2 MS 10 g/L蔗糖 10 g/L琼脂,内生真菌在共生培养过程中对石斛试管苗的生长有显著的促进作用。     

Osmoregulatory Responses of Fungi Inhabiting Standing Litter of the Freshwater Emergent Macrophyte Juncus effusus

Standing litter of emergent macrophytes often forms a major portion of the detrital mass in wetland habitats. Microbial assemblages inhabiting this detritus must adapt physiologically to daily fluctuations in temperature and water availability. We examined the effects of various environmental conditions on the concentrations of osmoregulatory solutes (polyols and trehalose) and the respiratory activities of fungal assemblages inhabiting standing litter of the freshwater emergent macrophyte Juncus effusus. Under field conditions, the concentrations of osmolytes (polyols plus trehalose) in fungal decomposers were negatively correlated with plant litter water potentials (r = −0.75, P < 0.001) and rates of microbial respiration (r = −0.66, P < 0.001). The highest concentration of osmolytes (polyols plus trehalose) occurred in standing litter exposed to desiccating conditions (range from wet to dry, 0.06 to 0.68 μmol · mg of fungal biomass⁻¹). Similar fluctuations in polyol and trehalose concentrations were observed in standing litter wetted and dried under laboratory conditions and for four predominant fungal decomposers of J. effusus grown individually on sterilized Juncus leaves. These studies suggest that fungal inhabitants associated with standing litter of emergent macrophytes can adjust their intracellular solute concentrations in response to daily fluctuations in water availability.     

基于PCR DGGE的小鼠肠道菌群基因组提取方法的建立

通过比较4种小鼠粪便细菌总DNA提取方法对基于PCR-DGGE检测的肠道菌群多样性分析的影响,旨在建立适于PCR—DGGE的小鼠肠道微生物宏基因组提取的稳定、经济、快捷的方法。采用SDS裂解法、某国产市售粪便DNA提取试剂盒、改进的化学裂解法、改进的溶菌酶法4种方法提取小鼠粪便细菌总DNA,通过琼脂糖凝胶电泳、紫外分光光度法、细菌16S rRNAV3区PCR扩增结合DGGE对提取结果进行比较分析。SDS裂解法和国产市售试剂盒2种方法提取粪便细菌总DNA均未得到理想结果,另2种方法均能够检测到粪便中20种左右的细菌。改进的化学裂解法和改进的溶菌酶提取法的建立为基于PCR—DGGE进行肠道菌群结构的定量及定性分析提供了可靠的前提基础和实验保障。     

Effect of Cadmium on Fungi and on Interactions Between Fungi and Bacteria in Soil: Influence of Clay Minerals and pH

Fungi (Rhizopus stolonifer, Trichoderma viride, Fusarium oxysporum f. sp. conglutinans, Cunninghamella echinulata, and several species of Aspergillus and Penicillium) tolerated higher concentrations of cadmium (Cd) when grown in soil than when grown on laboratory media, indicating that soil mitigated the toxic effects of Cd. In soil amended with clay minerals, montmorillonite provided partial or total protection against fungistatic effects of Cd, whereas additions of kaolinite provided little or no protection. Growth rates of Aspergillus niger were inhibited to a greater extent by 100 or 250 μg of Cd per g in soil adjusted to pH 7.2 than in the same soil at its natural pH of 5.1. However, there were no differences in the growth rates of Aspergillus fischeri with 100 or 250 μg of Cd per g in the same soil, whether at pH 5.1 or adjusted to pH 7.2. Growth of A. niger and A. fischeri in a soil contaminated with a low concentration of Cd (i.e., 28 μg/g), obtained from a site near a Japanese smelter, did not differ significantly from growth in a soil collected some distance away and containing 4 μg of Cd per g. Growth of A. niger in sterile soil amended with 100 μg of Cd per g and inoculated with Bacillus cereus or Agrobacterium tumefaciens was reduced to a greater extent than in the same soil containing 100 μg of Cd per g but no bacteria. The inhibitory effects of Agrobacterium radiobacter to A. niger were slightly reduced in the presence of 100 μg of Cd per g, whereas the inhibitory effects of Serratia marcescens were enhanced.     

Establishment of Vesicular-Arbuscular Mycorrhizal Fungi and Other Microorganisms on a Beach Replenishment Site in Florida

Beach replenishment is a widely used method of controlling coastal erosion. To reduce erosional losses from wind, beach grasses are often planted on the replenishment sands. However, there is little information on the microbial populations in this material that may affect plant establishment and growth. The objectives of this research were to document changes in the populations of vesicular-arbuscular mycorrhizal (VAM) fungi and other soil microorganisms in replenishment materials and to determine whether roots of transplanted beach grasses become colonized by beneficial microbes. The study was conducted over a 2-year period on a replenishment project in northeastern Florida. Three sampling locations were established at 1-km intervals along the beach. Each location consisted of three plots: an established dune, replenishment sand planted with Uniola paniculata and Panicum sp., and replenishment sand left unplanted. Fungal and bacterial populations increased rapidly in the rhizosphere of beach grasses in the planted plots. However, no bacteria were recovered that could fix significant amounts of N₂. The VAM fungi established slowly on the transplanted grasses. Even after two growing seasons, levels of root colonization and sporulation were significantly below those found in the established dune. There was a shift in the dominant VAM fungi found in the planted zone with respect to those in the established dunes. The most abundant species recovered from the established dunes were Glomus deserticola, followed by Acaulospora scrobiculata and Scutellospora weresubiae. The VAM fungi that colonized the planted zone most rapidly were Glomus globiferum, followed by G. deserticola and Glomus aggregatum.     

The in vivo Effect of Nisin on the Microflora of the Oral Cavity

SUMMARY: Saliva specimens from 2 groups of volunteers were taken immediately before and after one group had consumed 25,000 i.u. of nisin/day for 14 days, and were analysed quantitatively for total viable and nisin-resistant bacteria. No significant differences were observed between the pre- and post-test specimens from either group.