Decolorization of Synthetic Dyes and Textile Effluents by Basidiomycetous Fungi

Decolorization of six synthetic dyes and two raw textile effluents (A and B) by eight basidiomycetous fungi was investigated. Among eight basidiomycetous fungi, fungal isolate RCK-1 decolorized textile effluent A maximally (42%), while fungal isolate RCK-3 was found to decolorize more of Congo Red (69%), Xylidine Ponceau 2R (100%), Poly R-478 (96%), Indigo Carmine (99%), Lissamine Green B (90%), Toluidine Blue (57%) and textile effluent B (54%), than the rest of fungi. Percentage decolorization of all synthetic dyes and textile effluents by the new fungal isolates RCK-1 and RCK-3 was higher compared to the most widely studied simultaneous lignin degrader, Phanerochaete chrysosporium and selective lignin degrader, Pycnoporus cinnabarinus, when tested in liquid cultures. A statistically significant positive correlation between laccase production and decolorization of dyes and effluents was obtained as compared to other ligninolytic enzymes (lignin peroxidase and manganese peroxidase) production. This showed the importance of the differential contribution of the different ligninolytic enzymes towards the decolorization of the synthetic dyes and textile effluents. The substantially higher ligninolytic enzyme production by the fungal isolates RCK-1 and RCK-3 also suggested their potential use for textile effluent treatment and other possible biotechnological applications.     

Decolorization and Metabolism of Anthraquionone-Type Dye by Laccase of White-Rot Fungi Polyporus sp. S133

Utilization of microbes including white-rot fungi and bacterial strains for decolorization of synthetic dyes is one promising strategy of an environmentally friendly and cost-competitive alternative to physico-chemical decomposition processes for treating industrial effluents. In this study, the biodegradation ability of the white-rot fungi Polyporus sp. S133 that produce high laccase was investigated in order to decolorize anthraquinone-type dye. Parameter including pH, temperature, and non-ionic surfactant were used to comparatively study the decolorizing effects on Remazol Brilliant Blue R (RBBR). The purified laccase totally decolorized 200 mg L⁻¹ initial concentration of RBBR dye when only 1.5 U L⁻¹ of laccase was used in the reaction mixture. The optimal decolorization rates were achieved at pH 5 and at a temperature of 50°C. N-hydroxybenzotriazole, a small molecular weight redox mediator, was found to accelerate the decolorization. Tween 20 inhibited the decolorization while Tween 80 and Brij 35 showed no inhibition effect. Two compounds were identified as the intermediates (m/z 304.3 and m/z 342.2). These results suggest that laccase from Polyporus sp. S133 is a powerful tool for the decolorization of anthraquinone dyes. A pathway for the metabolism of the RBBR by laccase of Polyporus sp S133 was proposed. These proposed pathways could contribute to a better comprehension of the mechanisms used by oxidative enzymes to transform organic compounds.     

Humic acid bleaching by white-rot fungi isolated from biosolids compost

A screening assay for isolating humic-substances degrading fungi from biosolids compost at the thermophillic phase employed using plates containing 2,2′-azino-bis(3-ethylbenzothiazoline-sulfonic acid) (ABTS), MnCl₂ or the monoazo dye Acid Red 183. Two of the most active fungi out of 70 fungal strains isolated were identified based on rDNA sequences and designated Trametes sp. M23 and Phanerochaete sp. Y6 (accessions no. DQ408582 and DQ438910). These isolates, when compared to a model white-rot fungi T. versicolor and P. chrysosporium, showed the ability to bleach humic acids extracted from biosolids compost while growing under solid-state conditions using perlite as a solid support. T. versicolor and Trametes sp. M23 also exhibited the ability to bleach humic acids from a peat source. Interestingly, only Trametes sp. M23 bleached leonardite humic acid, which is considered to be a highly aromatic and stable type of natural organic matter. To the best of our knowledge, this is the first report of white-rot fungi being isolated and identified from thermophilic composts. Since these fungi are capable of degrading lignin and humic acid and were found active in organic-matter-degradation processes, we suggest that they may play a significant role in the degradation and transformation of these refractory substances during composting.     

Arbuscular mycorrhizal fungal spore-associated bacteria affect mycorrhizal colonization,plant growth and potato pathogens

Arbuscular mycorrhizal (AM) fungi and their bacterial associates are essential living components of the soil microbiota. From a total of 385 bacteria previously isolated from spores of AM fungi (AMB), 10 were selected based on ability to inhibit growth of plant pathogens. Effects of these isolates on AM fungal colonization, plant growth in potato (Solanum tuberosum L.) and inhibition of pathogens was investigated. AM fungal root colonization of potato was 7-fold higher in the presence of the Pseudomonas FWC70 isolate in a greenhouse and was 6–9-fold higher in the presence of the three isolates Pseudomonas FWC70, Stenotrophomonas FWC94 and Arthrobacter FWC110 in an outdoor pot experiment. Several growth traits of potato were stimulated by the Pseudomonas isolates FWC16, FWC30 and FWC70 and by the Stenotrophomonas isolate FWC14. All three Pseudomonas isolates showed inhibition against Erwinia carotovora, Phytophthora infestans and Verticillium dahliae but Stenotrophomonas isolates were variable. Protease(s), siderophores and indole acetic acid were produced by all isolates. Chitinase(s) were produced by all Stenotrophomonas and phosphate-solubilizing activity by all Pseudomonas isolates, the Stenotrophomonas FWC14 isolate and the Arthrobacter FWC110 isolate. We conclude that some AMB are multifunctional and production of extracellular enzymes and bioactive compounds are likely mechanisms for their multifunctional activities. Our results show that some AMB are likely to contribute to the often described ability of AM fungi to inhibit pathogens, acquire mineral nutrients and modify plant root growth.     

Fertilizer-induced pathogenicity of mycorrhizal fungi to sweetgum seedlings

One isolate of Glomus clarus, two of G. etunicatus, and one of G. claroideum, obtained from plants growing on abandoned stripmine sites in Kentucky, and an isolate of G. fascicutatus known to stimulate growth of various woody plants, were evaluated for their influence on growth of sweetgum seedlings in a mixture of sand and stripmine soil. Soils were supplemented with various rates of a complete slow-release fertilizer. Throughout the growth period, G. fasciculatus, and most of the stripmine isolates, stimulated growth at low fertilizer rates. At higher fertilizer rates, including the level optimum for non-mycorrhizal plants, the stripmine isolates inhibited plant growth. After 14 weeks, plants inoculated with one of the four stripmine isolates overcame the early growth depression, and those inoculated with a second isolate appeared to be overcoming the growth depression. G. fasciculatus was not inhibitory at any fertilizer rate. Root colonization by all three isolates evaluated was inhibited by the highest fertilizer rate, but this effect was not related to growth inhibition of plants. The other two isolates colonized roots at an extremely low rate (< 1%). Sporulation of all the stripmine isolates, but not G. fasciculatus, was also inhibited by the highest fertilizer rate. The G. fasciculalus isolate used in this study may be atypical of mycorrhizal fungi occurring randomly in nature in its mutualistic or neutral effect on plants under a wide range of growth conditions.     

Evolution of Chemistry along the Bagmati Drainage Network in Kathmandu Valley

Two fungal strains producing ligninolytic enzymes and having the potential to decolorize distillery effluent were isolated from the soil of a distillery effluent contaminated site. DNA was isolated from the pure cultures of these fungi and polymerase chain reaction (PCR) amplification of their internal transcribed spacer (ITS) region of nuclear ribosomal DNA was carried out. Further, the DNA was sequenced and the comparison of generated sequence with database led to their identification as Penicillium pinophilum TERI DB1 and Alternaria gaisen TERI DB6 respectively. These two isolates along with one isolate of Pleurotus florida EM 1303 were assessed for their ligninolytic enzyme activity in culture filtrate as well as after solid state fermentation on two substrates wheat straw and corncob powder. Ergosterol was measured to assess the growth of fungi on solid media. Both P. pinophilum TERI DB1 and A. gaisen TERI DB6 were found to produce laccase, manganese-dependent peroxidases (MnP) and lignin peroxidases (LiP). The immobilized fungal biomass was then used for decolorization of the post biomethanated wastewater from the distillery. Reduction in color up to the magnitude of 86, 50 and 47% was observed with P. florida, P. pinophilum and A. gaisen respectively.     

Colonisation of seminal roots of wheat and barley by egg-parasitic nematophagous fungi and their effects on Gaeumannomyces graminis var. tritici and development of root-rot

This study provides evidence that egg-parasitic nematophagous fungi, Pochonia chlamydosporia, Pochonia rubescens and Lecanicillium lecanii, can also reduce root colonisation and root damage by a fungal pathogen. Interactions of nematophagous fungi with the take-all fungus, Gaeumannomyces graminis var. tritici (Ggt), and their influence on severity of the root disease it causes were studied in laboratory and pot experiments. In Petri dish experiments the three nematophagous fungi reduced colonisation of barley roots by Ggt and also reduced necrotic symptoms. On the contrary, root colonisation by nematophagous fungi was unaffected by Ggt. In growth tube experiments, the three nematophagous fungi again reduced Ggt root colonisation and increased effective root length of barley seedlings. This was true for both simultaneous and sequential inoculation of nematophagous fungi versus Ggt. In the pot experiments the inoculum of the tested fungi in soil was applied in the same pot, as a mixture or in layers, or in coupled pots used for wheat grown with a split-root system. The nematophagous fungi P. chlamydosporia (isolate 4624) and L. lecanii (isolate 4629), mixed with Ggt or in split root systems with the pathogen, promoted growth of wheat (i.e. increased shoot weight), although no disease reduction was found. In split root systems, lower levels of peroxidase activity were found in seedlings inoculated with Ggt in combination with the nematophagous isolates 4624 and 4629 than when the take-all fungus was applied alone.Our results show that nematophagous fungi reduce root colonisation by Ggt, root damage and stress induced senescence in Ggt-inoculated plants.     

Experimental study of sequences of ectomycorrhizal fungi on birch (Betula SP.) seedling root systems

Birch seedlings on which mycorrhizas of different fungi (primary inoculants) were established in aseptic conditions were transplanted into pots of brown earth supplemented with inocula of other mycorrhizal fungi (secondary inoculants) in a glasshouse study. Leccinum scabrum and Amanita muscaria did not persist as primary inoculants after transplanting seedlings to soil, and did not colonize as secondary inoculants, irrespective of the presence of other mycorrhizal fungi. Lactarius pubescens persisted poorly as a primary inoculant after transplanting and did not colonize seedlings as a secondary inoculant in soil; however, Lactarius-type mycorrhizas sometimes developed from naturally occurring inoculum in soil, especially after seedlings had been subjected to dormancy. Hebeloma sacchariolens and Thelephora terrestris persisted and spread as primary inoculants after transplanting and also colonized seedlings as secondary inoculants. These fungi apparently competed with one another, H. sacchariolens being dominant in a brown earth; but H. sacchariolens was ineffective as either primary or secondary inoculant in sphagnum peat, whereas T. terrestris formed abundant mycorrhizas in peat. Two isolates of Paxillus involutus behaved differently from one another: one isolate did not persist as a primary inoculant and did not colonize as a secondary inoculant whereas the other isolate did not persist as a primary inoculant but colonized seedlings extensively as a secondary inoculant in soil.The results demonstrate important and predictable behavioural differences between mycorrhizal fungi that have been termed “early-stage” and “late-stage” in mycorrhizal sequences on birch. Only early-stage mycorrhizal types were suitable for artificial inoculation of seedlings; they influenced subsequent colonization by some other mycorrhizal fungi but did not facilitate colonization by late-stage types typical of mature tree stands.     

Characterization of Reactive Red-120 Decolorizing Bacterial Strain Acinetobacter junii FA10 Capable of Simultaneous Removal of Azo Dyes and Hexavalent Chromium

Continual discharge of textile wastewaters loaded with a variety of synthetic dyes and metals is considered as a huge threat to surrounding ecosystems. In order to treat these undesirable pollutants, microbial bioremediation is considered as an efficient and economical technique. This study was conducted to evaluate the use of bacterial strains for simultaneous removal of azo dyes and hexavalent chromium [Cr(VI)]. Fifty-eight bacterial strains were isolated from Paharang drain wastewater and tested for their potential to decolorize reactive red-120 (RR-120) in the presence of 25 mg L^?1 of Cr(VI). Among the tested isolates, FA10 decolorized the RR-120 most efficiently and was identified as Acinetobacter junii strain FA10. Based on quadratic polynomial equation and response surfaces given by the response surface methodology (RSM), Cr concentration and pH were found to be the main factors governing the RR-120 decolorization by FA10. The strain FA10 also exhibited a substantial salt resistance since it showed a considerable decolorization of RR-120 even in the presence of 150 g L^?1 of NaCl. Moreover, the strain FA10 also showed the potential to simultaneously remove the Cr(VI) and the selected azo dyes in the same medium. More than 80 % of the initially added Cr(VI) was removed over 72 h of incubation along with the appreciable decolorization efficiency. The strain FA10 also exhibited good tolerance to considerable levels of different heavy metals. The findings of this study suggest that the strain FA10 might serve as an efficient bioresource to develop the biotechnological approaches for simultaneous removal of different azo dyes and heavy metals including Cr(VI).     

Decomposition of lignins by microorganisms

Soil microorganisms, inducing bacteria, fungi imperfecti, and basidiomycetes were investigated to determine their roles in lignin degradation. White-rot basidiomycete fungi and some bacteria demonstrated ability to degrade specifically-labeled synthetic lignins (DHPs). White-rot basidiomycetes degraded methoxyl groups and bacteria degraded side chains most rapidly. Fungi imperfecti, brown-rot basidiomycetes and some bacteria were unable to degrade DHPs. Interactions of white-rot basidiomycetes with imperfects usually resulted in decresed rates of DHP degradation. Attempts to correlate the ability to degrade DHPs with ability of the microorganisms to grow upon aromatic C sources, demethylate $\text{p-(}{}^{14}\text{CH}{}_3\text{O}\text{)}\text{phenyl}$ and produce monooxygenases, dioxygenases, and polyphenoloxidases were unsuccessful.     

Diversity and phylogeny of rhizobial strains isolated from Lotus uliginosus grown in Uruguayan soils

Lotus uliginosus is generally nodulated by rhizobia of the genus Bradyrhizobium when used for improvement of Uruguayan pastures. The genetic diversity and phylogenetic relationships of 111 isolates from nodules of L. uliginosus collected from four fields with or without prior inoculation history were analyzed in this study. Genetic diversity estimated by ERIC-PCR revealed 75 different genomic fingerprints, and showed a relatively greater value compared with other methods and varied by soil type. 16S ribosomal RNA gene RFLP analysis revealed three different ribogroups, A, B and C, with 71 isolates in ribogroup A, three isolates in ribogroup B and only one in ribogroup C. Phylogenetic analyses based on 16S RNA gene sequences, ITS, as well as atpD, recA and glnII gene sequences indicated that ribogroup A strains were affiliated with B. japonicum bv. genistearum strains. The three isolates in ribogroup B did not clearly associate with any Bradyrhizobium species described previously and could represent a novel species within this genus. Unlike B. japonicum strains these isolates were able to nodulate and fix nitrogen with other Lotus species as well as with Spartium, a leguminous shrub. The unique isolate in ribogroup C clustered with Mesorhizobium and appeared genetically and phenotypically related to broad host-range Mesorhizobium sp. NZP2037. Our data suggest that Uruguayan soils contain native or naturalized bradyrhizobia that are able to nodulate L. uliginosus as efficiently as the commercial strain NZP2309 but could have adaptive advantages making them more suitable for inoculant purposes.     

Comparaison des aptitudes parasitaires de clones de Trichoderma vis-a-vis de quelques champignons a sclerotes

Nineteen monoconidial isolates (referred to as clones) of Trichoderma from different species aggregates, one isolate of Gliocladium virens, and one isolate of an Acrostalagmus sp. (that was naturally associated with sclerotia of Sclerotinia spp and Macrophomina phaseolina) were tested. They were incubated in controlled conditions, in sterile soil, with sclerotia of Corticium rolfsii, Sclerotinia minor, or S. sclerotiorum. At the end of appropriate periods of incubation (respectively 26, 20 and 8 days), the sclerotia were retrieved from soil and checked for invasion by the antagonist. Important differences between the parasitic ability of Trichoderma clones were noted. Clones from at least three different species (T. aureoviride, T. hamatum, T. harzianum) exhibited a high antagonistic activity. Activity of the G. virens isolate was at the same level as the best clones of Trichoderma, whereas no parasitic tendencies were found in the isolate of Acrostalagmus sp., thus confirming previous results.A rather good correlation was found between the capacity of the clones for attacking C. rolfsii sclerotia and their ability to parasitize both Sclerotinia.In conclusion, it is proposed that a screening with only one of the sclerotial species would give clones efficient against all three, and possibly against related sclerotial types.     

Immobilization of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> Cells on <Emphasis Type="Italic">Luffa cylindrica</Emphasis>: a Study of a Novel Material for the Adsorption of Textile Dye

The textile industry is responsible for the disposal of a large volume of effluents containing synthetic dyes, which are considered to be highly toxic compounds for both human health and the environment. The aim of the present study was to test potential use of a renewable, low-cost product—Luffa cylindrica in disk and powder form—as adsorbent material for the treatment of textile effluents containing dyes. Saccharomyces cerevisiae cells were also immobilized on L. cylindrica to increase the adsorbent capacity. Batch experiments were conducted for the evaluation of the removal of the azo dye Direct Red 23. The Langmuir, Freundlich, and Temkin isotherms were used for a better interpretation of the data. The results showed that adsorption is more efficient at acidic pH and all adsorbent materials best fit the Langmuir model, indicating the formation of a monolayer. The isotherm results also demonstrated that the materials immobilized with the yeast had a greater sorption rate, but the cell-free L. cylindrica powder had a higher adsorbate/adsorbent interaction. The comparison with a spectrophotometrically defined standard revealed that the powder without and with yeast cells was able to achieve an acceptable removal rate of the dye from the solution. Moreover, the difference in adsorption between the powder without and with yeast cells was very small. Thus, the application of the cell-free L. cylindrica powder is economically more feasible. The findings demonstrate the potential use of L. cylindrica powder as an adsorbent for the treatment of effluents containing textile dyes.     

Root-nodule bacteria from indigenous legumes in the north-west of Western Australia and their interaction with exotic legumes

Bacteria were isolated from root-nodules collected from indigenous legumes at 38 separate locations in the Gascoyne and Pilbara regions of Western Australia. Authentication of cultures resulted in 31 being ascribed status as root-nodule bacteria based upon their nodulation of at least one of eight indigenous legume species. The authenticated isolates originated from eight legume genera from 19 sites. Isolates were characterised on the basis of their growth and physiology; 20 isolates were fast-growing and 11 were slow-growing (visible growth within 3 and 7 d, respectively). Fast-growers were isolated from Acacia, Isotropis, Lotus and Swainsona, whilst slow-growers were from Muelleranthus, Rhynchosia and Tephrosia. Indigofera produced one fast-growing isolate and seven slow-growing isolates. Three indigenous legumes (Swainsona formosa, Swainsona maccullochiana and Swainsona pterostylis) nodulated with fast-growing isolates and four species (Acacia saligna, Indigofera brevidens, Kennedia coccinea and Kennedia prorepens) nodulated with both fast- and slow-growing isolates. Swainsona kingii did not form nodules with any isolates. Fast-growing isolates were predominantly acid-sensitive, alkaline- and salt-tolerant. All slow-growing isolates grew well at pH 9.0 whilst more than half grew at pH 5.0, but all were salt-sensitive. All isolates were able to grow at 37 °C. The fast-growing isolates utilised disaccharides, whereas the slow-growing isolates did not. Symbiotic interactions of the isolates were assessed on three annual, one biennial and nine perennial exotic legume species that have agricultural use, or potential use, in southern Australia. Argyrolobium uniflorum, Chamaecytisus proliferus, Macroptilium atropurpureum, Ononis natrix, Phaseolus vulgaris and Sutherlandia microphylla nodulated with one or more of the authenticated isolates. Hedysarum coronarium, Medicago sativa, Ornithopus sativus, Ornithopus compressus, Trifolium burchellianum, Trifolium polymorphum and Trifolium uniflorum did not form nodules. Investigation of the 31 authenticated isolates by polymerase chain reaction with three primers resulted in the RPO1 primer distinguishing 20 separate banding patterns, while ERIC and PucFor primers distinguished 26 separate banding patterns. Sequencing the 16S rRNA gene for four fast- and two slow-growing isolates produced the following phylogenetic associations; WSM1701 and WSM1715 (isolated from Lotus cruentus and S. pterostylis, respectively) displayed 99% homology with Sinorhizobium meliloti, WSM1707 and WSM1721 (isolated from Sinorhizobium leeana and Indigofera sp., respectively) displayed 99% homology with Sinorhizobium terangae, WSM1704 (isolated from Tephrosia gardneri) shared 99% sequence homology with Bradyrhizobium elkanii, and WSM1743 (isolated from Indigofera sp.) displayed 99% homology with Bradyrhizobium japonicum.     

Mycoparasitism by Pythium oligandrum and P. acanthicum

Isolates of the reported mycoparasites Pythium oligandrum, P. acanthicum and P. periplocum markedly reduced growth and cellulolysis by Botryotrichum piluliferum, grew rapidly across agar plates precolonized by Phialophora radicicola var radicicola (sensu Deacon) and, where tested (not P. periplocum), were non-pathogenic towards higher plants. Isolates of P. echinulatum, P. mamillatum. P. megalacanthum, P. spinosum, P. ultimum and one isolate of P. acanthicum behaved differently from the mycoparasites and could, themselves, be placed in two groupings in these tests. It is suggested that the ability or otherwise to grow on Phialophora-precolonized agar plates may help to distinguish broad biological groupings within the genus Pythium, but these groupings may cut across conventional taxonomic ones.One isolate of P. acanthicum was tested for its effects on a range of cellulolytic fungi: it reduced their growth to different extents, as did P. oligandrum.Plates of potato-dextrose agar precolonized by Phialophora radicicola were used to isolate selectively P. oligandrum and similar fungi from soils, but the use of hemp seed baits in conjunction with precolonized plates was less selective for these fungi.Straw pieces precolonized by P. oligandrum and buried in soil decomposed at the same rate as virgin straws or those precolonized by P. ultimum or Mucor hiemalis. Subsequently, Stachyholrys atra appeared to colonize straws more frequently from soil, and Fusarium spp. less so, in the presence of P. oligandrum than in its absence. In the laboratory, P. oligandrum was antagonized by Slachyholrys, whereas Fusarium spp. were frequently overgrown by the Pythium.     

Biologically-induced hydrolysis of parathion in soil: Isolation of hydrolyzing bacteria

Fifty bacterial isolates from a parathion-treated soil (Gilat, Israel) were tested for their ability to hydrolyze the organophosphorus insecticide, parathion in peptone-yeast extract medium. After 5 days 33 isolates had hydrolyzed at least a portion of the added parathion. Eight of these isolates hydrolyzed 75% of the added parathion in 5 days and appeared to be Bacillus strains. Ten of these 33 isolates had hydrolyzed all of the parathion after 5 days and appeared to be Arthrohacter strains. One isolate from each group was tested further. During the logarithmic phase of growth, Bacillus sp., isolate 10, hydrolyzed less than 10% of the parathion added to peptone-yeast extract medium and was not active in parathion hydrolysis when inoculated into sterilized, parathion-treated soil. Arthrobacter sp., isolate 6, hydrolyzed parathion rapidly in peptone-yeast extract medium and in sterilized, parathion-treated soil. It used parathion or its hydrolysis product, p-nitrophenol, as sole carbon source. The parathion hydrolyzing enzyme appeared to be constitutive in isolate 6. Single applications of p-nitrophenol at concentrations greater than 1 mM inhibited growth but successive additions of smaller amounts permitted growth to continue.     

Resistance in natural populations of three wild Lactuca species from Israel to highly virulent Californian isolates of Bremia lactucae

Seedlings of 213 accessions representing 9, 14, and 10 Israeli natural populations of the wild Lactuca serriola, L. saligna, and L. aculeata, respectively, were initially screened for their resistance to a pathotype CAVIII isolate of Bremia lactucae. All 60 L. serriola accessions were susceptible while all 83 accessions of L. saligna were resistant. Out of the 69 L. aculeata accessions, 36 (52.2 %) were resistant. From those resistant accessions, 56 L. saligna and 23 L. aculeata accessions were then tested at the seedling stage for their reaction against five highly virulent isolates originating from California and representing the two current major pathotypes and a novel type of B. lactucae; true leaves of adult plants were also tested with two out of these five isolates. Our study supports previous observations that L. saligna is highly resistant to B. lactucae. However, our results provide additional evidence that L. saligna may not be an absolutely non-host plant for B. lactucae at least at a seedling stage, which is in agreement with other recent data for this species. Sixteen (69.6 %) out of the 23 L. aculeata accessions expressed resistance against all isolates tested, even in seedling stage as well as in true leaves of adult plants. This study is probably the first report of detailed screening of resistance to some B. lactucae isolates in natural populations of L. aculeata. These patterns of resistance reactions show that L. aculeata, a species within the primary lettuce gene pool, should be considered as an attractive source of germplasm for resistance breeding of cultivated lettuce (L. sativa).     

Production of lignocellulose-degrading enzymes and degradation of leaf litter by saprotrophic basidiomycetes isolated from a Quercus petraea forest

Due to the production of lignocellulose-degrading enzymes, saprotrophic basidiomycetes can significantly contribute to the turnover of soil organic matter. The production of lignin- and polysaccharide-degrading enzymes and changes of the chemical composition of litter were studied with three isolates from a Quercus petraea forest. These isolates were capable of fresh litter degradation and were identified as Gymnopus sp., Hypholoma fasciculare and Rhodocollybia butyracea. Within 12 weeks of incubation, H. fasciculare decomposed 23%, R. butyracea 32% and Gymnopus sp. 38% of the substrate dry mass. All fungi produced laccase and Mn-peroxidase (MnP) and none of them produced lignin peroxidase or other Mn-independent peroxidases. There was a clear distinction in the enzyme production pattern between R. butyracea or H. fasciculare compared to Gymnopus sp. The two former species caused the fastest mass loss during the initial phase of litter degradation, accompanied by the temporary production of laccase (and MnP in H. fasciculare) and also high production of hydrolytic enzymes that later decreased. In contrast, Gymnopus sp. showed a stable rate of litter mass loss over the whole incubation period with a later onset of ligninolytic enzyme production and a longer lasting production of both lignin and cellulose-degrading enzymes. The activity of endo-cleaving polysaccharide hydrolases in this fungus was relatively low but it produced the most cellobiose hydrolase. All fungi decreased the C/N ratio of the litter from 24 to 15-19 and Gymnopus sp. also caused a substantial decrease in the lignin content. Analytical pyrolysis mass spectrometry of litter decomposed by this fungus showed changes in the litter composition similar to those caused by white-rot fungi during wood decay. These changes were less pronounced in the case of H. fasciculare and R. butyracea. All fungi also changed the mean masses of humic acid and fulvic acid fractions isolated from degraded litter. The humic acid fraction after degradation by all three fungi contained more lignin and less carbohydrates. Compared to the decomposition by saprotrophic basidiomycetes, litter degradation in situ on the site of fungal isolation resulted in the relative enrichment of lignin and differences in lignin composition revealed by analytical pyrolysis. It can most probably be explained by the participation of non-basidiomycetous fungi and bacteria during natural litter decomposition.     

Origin and properties of β-glucosidase activity of tomato-field soil

The distribution of β-glucosidase activity in a tomato-field soil was examined. Of the total activity found, > 50% was in the < 2mm soil fraction, 20% in the organic debris and a significant proportion in roots. In an attempt to determine the origin of β-glucosidase in this soil, the properties of β-glucosidase of various fungal and bacterial isolates from the soil, and of plant materials, were studied.Selective inhibition of bacterial or fungal growth in re-moistened, over-dried, inoculated soil indicated that fungi were a more important source of β-glucosidase in this soil. Monierella, Actinomucor, Coniochaeta and Penicillium were the principal fungi isolated from the soil by the dilution-plate technique, comprising over 60% of the total isolates. Remoistened oven-dried soil, inoculated with Mortierella and Actinomucor spp exhibited higher β-glucosidase activity after incubation than did soil inoculated with other strains.The β-glucosidase activity of extracts from cultured fungal strains had similar pH optima and Q₁₀ values to those of soil extracts. The β-glucosidase of extracts from isolates of bacteria and actinomycetes had similar Q₁₀ values, but higher pH optima, than did that of soil extracts.These results indicate that fungi, mainly some of the mucoraceous fungi, may be the primary source of β-glucosidase in tomato-field soil.     

Phytophthora species producing toxin active on tobacco

Extracts of oat cultures of 53 isolates of Pythium and Phytophthora and an isolate of Achlya were tested for their ability to cause watersoaking, laminar collapse, and dehydration of excised tobacco leaves. Extracts of oat cultures of 10 of 11 isolates of P. cryptogea Pethy. & Laff., 4 of 5 isolates of P. megasperma Drechs., all 5 isolates of P. drechsleri Tucker, and 3 of 4 isolates of P. erythroseptica Pethy, were toxic to tobacco laminae. Mycelial extracts of three P. cryptogea isolates obtained from three diverse sources had properties similar to a previously studied toxin from P. cryptogea. Extracts of oat cultures of three P. cryptogea isolates and an isolate of P. megasperma caused foliar toxicity and growth reduction of tobacco transplants. Mycelial extracts of isolates of four species of Phytophthora active on excised leaves were also active in inhibiting plant growth. Most isolates of these four species of Phytophthora appear to produce identical or similar toxins. Although not parasitic to tobacco, those species are potentially detrimental to tobacco.