[Short-term nitrogen deposition changes chemical composition of litter and soil organic matter in a Moso bamboo forest]

To investigate the effects of short-term nitrogen (N) deposition on organic matter composition of litter and soil in Moso bamboo (Phyllostachys edulis) forests, we established a N-addition treatments (50 kg N·hm-2·a-1) to simulate the ambient and N deposition in a subtropical Moso bamboo forest from July 2020 to January 2022. We analyzed the organic matter composition of Moso bamboo leaf/root litter and soil by using pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) technique. The results showed that short-term N deposition significantly increased the relative content of soil phenols by 50.9%, while significantly decreased fatty acids by 26.3%. The rela-tive content of alkanes & alkenes and lignin in leaf litter was significantly increased by 51.9% and 33.5%, respectively, while that of phenols and polysaccharides significantly decreased by 52.2% and 56.3%. In root litter, eleva-ted N significantly decreased the relative content of polycyclic aromatic hydrocarbons by 16.6%. Moreover, the relative content of fatty acids in soil organic matter was significantly positively correlated with the relative content of poly-saccharides in leaf litter. The relative content of phenols in soil organic matter was significantly positively correlated with the relative content of lignin, and negatively correlated with the relative content of polysaccharides in leaf litter. Our results demonstrated that short-term N deposition did not change the concentration of total organic carbon, total nitrogen, and C/N of the soil, leaf litter, and root litter, but significantly altered the chemical composition of organic matter. In addition, the changes in chemical composition of organic matter in soil under short-term N deposition were affected by the composition of organic matter in leaf litter.

Effects of maize straw and its biochar application on soil organic carbon chemical composition and carbon degradation genes in a Moso bamboo forest

We investigated the effects of maize straw and its biochar application on soil organic carbon chemical composition, the abundance of carbon degradation genes (cbhI) and the composition of cbhI gene community in a Moso bamboo forest, to provide the theoretical and scientific basis for enhancing carbon sequestration. We conducted a one-year field experiment in a subtropical Moso bamboo forest with three treatments: control (0 t C·hm-2), maize straw (5 t C·hm-2), and maize straw biochar (5 t C·hm-2). Soil samples were collected at the 3rd and 12th months after the treatment. Soil organic carbon chemical composition, the abundance and community composition of cbhI gene were determined by solid-state 13C NMR, real-time fluorescence quantitative PCR, and high-throughput sequencing, respectively. The results showed that compared with the control, maize straw treatment significantly increased the content of O-alkyl C and decreased aromatic C content, while maize straw biochar treatment showed an opposite effect. Maize straw treatment significantly increased the abundance of cbhI gene and the relative abundance of Penicillium, Gaeumannomyces and Marasmius. However, maize straw biochar treatment reduced the abundance of this gene. The relative abundance of dominant cbhI in soils was positively correlated with the content of O-alkyl C and negatively correlated with the content of aromatic C. Results of redundancy analysis showed that maize straw treatment had a significant effect on the microbial community composition of cbhI gene by changing soil O-alkyl C content, while maize straw biochar affected the microbial community composition of cbhI gene by changing soil pH, organic carbon, and aromatic C content. Maize straw biochar treatment was more effective in increasing soil organic carbon stability and reducing microbial activity associated with carbon degradation in the subtropical Moso bamboo forest ecosystem compared with maize straw treatment. Therefore, the application of biochar has positive significance for maintaining soil carbon storage in subtropical forest ecosystems.

[Effects of Low-density Polyethylene Microplastics on the Growth and Physiology Characteristics of Ipomoea aquatica Forsk]

Microplastic pollution in soil and its toxicological effects have attracted increasing attention from researchers, but the mechanisms of microplastics affecting crop growth and physiology remain unclear. A pot experiment was conducted to evaluate the impacts of various mass concentrations (0%, 0.2%, 5%, and 10%) of low-density polyethylene microplastics (LDPE MPs) on the germination rate, photosynthetic pigment content, biomass, antioxidant enzyme activity, soluble protein, and soluble sugar content of water spinach (Ipomoea aquatica Forsk). The results showed that LDPE MPs significantly inhibited (P<0.05) the seed vigor of water spinach, and the inhibitory effect increased with increasing concentration of LDPE MPs. However, the 5% LDPE MPs significantly promoted the aboveground biomass of water spinach. The 0.2% and 10% LDPE MPs significantly improved the superoxide dismutase (SOD) activity and catalase (CAT) and peroxidase (POD) activities, respectively. Further, malondialdehyde (MDA) content decreased with increasing concentration of LDPE MPs, and the reductions reached 15.53%-27.39% in comparison to that in the control. The LDPE MPs also significantly increased the soluble sugar content of water spinach leaves. In summary, LDPE MPs could inhibit the seed vigor and promote biomass accumulation in water spinach. Water spinach could relieve the oxidative stress caused by LDPE MPs by regulating antioxidant enzyme activity and soluble protein content. Therefore, this study may provide basic information for assessing the influences of microplastics on vegetables.

Effects of plant residues on C:N:P of soil, microbial biomass, and extracellular enzyme in an alpine mea-dow on the Qinghai-Tibetan Plateau, China

Plant residues can affect C:N:P of soil, microbial biomass, and extracellular enzyme, but the effects are still unclear. We conducted a field experiment in an alpine meadow on the eastern part of the Qinghai-Tibetan Plateau to explore the effects of removing aboveground plant or roots and adding plant residues on the C:N:P of soil, microbial biomass, and extracellular enzyme. The results showed that removing aboveground plant biomass significantly decreased soil C:N (the change was -23.7%, the same below) and C:P (-14.7%), microbial biomass C:P and N:P, while significantly increased microbial biomass C:N, and enzyme C:N:P compared with meadow without human disturbance. Removing all plant biomass (aboveground and roots) significantly reduced soil C:N (-11.6%), C:P (-24.0%), N:P (-23.3%) and microbial biomass C:N in comparison to removing aboveground plant, while significantly improved microbial biomass N:P and enzyme N:P. Adding plant residues after removing aboveground plant significantly increased microbial biomass C:N and C:P, enzyme C:N compared with removing aboveground plant, while significantly decreased enzyme N:P. Compared with removing all the plant, adding plant residues after removing whole plant significantly reduced soil C:N (-16.4%), microbial biomass C:P, N:P and enzyme N:P, while significantly increased enzyme C:N. Our results suggest that removal of plants could have a strong effect on C:N:P of soil, microbial biomass, and extracellular enzyme, and C:N:P of microbial biomass and that extracellular enzyme woule be more sensitive to plant residues. Roots could play a key role in stabilizing C:N:P of soil, microbial biomass, and extracellular enzyme under plant residues addition. Adding plant residues could be a suitable solution for restoring alpine meadows under the circumstance of intact roots, which was conducive to soil C storage, but might not be suitable for alpine meadows with serious root damage, which would increase soil CO₂ emission.

[Effects of the removal of invasive Moso bamboo on soil microbial biomass and enzyme activities in subtropical forests]

Removal of invasive plant species is the first step to restoring the invaded ecosystems. The soil microbial biomass and extracellular enzyme activities were measured in Moso bamboo (Phyllostachys edulis) pure forest (completely invasion), invasive P. edulis removal forest (secondary succession 5 years after clear cutting), and the evergreen broadleaved forest (no invasion) in Tianmu Mountain. The results showed that compared with P. edulis pure forest, invasive P. edulis removal significantly increased the contents of soil organic carbon (SOC), nitrate nitrogen, available phosphorus and potassium, as well as microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP), while significantly decreased microbial biomass nitrogen (MBN). The activities of α-glucosidase (AG), β-glucosidase (BG), leucine aminopeptidase (LAP) and phenol oxidase (POX) in the forest with removal of invasive P. edulis were significantly higher than those in P. edulis pure forest, while invasive P. edulis removal did not change the activities of cellodisaccharide hydrolase (CBH), β-N-acetyl-glucosaminopeptidase (NAG), acid phosphatase (ACP) and peroxidase (PER). Furthermore, the activities of AG, BG and LAP were positively correlated with SOC and MBC, while the increase in POX activity was positively correlated with soil nitrate content. In addition, MBC, MBN and MBP, and activities of AG, BG, NAG, LAP and ACP in P. edulis removal forest forest were significantly higher than those in evergreen broadleaved forests. Taken together, the removal of invasive P. edulis could increase soil nutrient contents, microbial biomass and extracellular enzyme activities, thus could be considered as an effective way to restore the invaded forests. Our results provide important theoretical basis for controlling P. edulis invasion in subtropical forests.

[Soil denitrifying enzyme activity and its influencing factors in a bamboo forest riparian zone in the upper reaches of the Taihu Lake Basin, China]

Soil denitrifying enzyme activity (DEA) was measured by acetylene inhibition technique, along with exploration of factors influencing DEA in a bamboo forest riparian zone in the upper reaches of the Taihu Lake Basin during summer. Our aim was to provide important insights into the assessment of ecological functions of bamboo forest riparian zone on reducing nitrogen pollution in rivers. The results showed that the riparian soil DEA ranged from 6.32 to 23.22 μg N·kg^-1·h^-1, with a mean value of 14.65 μg N·kg^-1·h^-1. The vertical distribution (0-40 cm soil profile) of DEA was affected by several factors, such as soil organic carbon (SOC), total nitrogen (TN), nitrate nitrogen (NO₃^--N), soil water content, and activity of carbon and nitrogen hydrolase, which resulted in decreased DEA with increasing soil depth. The horizontal changes in DEA (at the same soil depth but at different distances from river) was mainly governed by the variation in SOC concentration. In this area, the concentration of soil dissolved organic carbon was relatively low, which might inhibit the soil DEA during summer.

[Effects of nitrogen deposition and biochar application on soil N2O fluxes in a Moso bamboo plantation]

In July 2019-July 2020, we conducted a field trial to examine the effects of nitrogen addition (60 kg N·hm^-2·a^-1), biochar application (10 t·hm^-2), and their combination on soil N₂O emission and the relationship between soil N₂O emission and environmental factors in a typical Moso bamboo (Phyllostachys edulis) plantation in Hangzhou City of Zhejiang Province. Soil N₂O flux of Moso bamboo plantation was measured by the static chamber-gas chromatography technique. The results showed that nitrogen addition treatment increased the annual cumulative N₂O emission by 14.6%, while biochar application and the combination treatment reduced it by 20.8% and 10.6%, respectively. Soil N₂O flux rate was significantly correlated with soil temperature, NO₃^--N concentration, urease and protease activities, and soil NH₄⁺-N concentration across all treatments. In conclusion, under the background of nitrogen deposition, the application of biochar would have a significant reduction effect on soil N₂O fluxes in Moso bamboo plantations.

[Characteristics and Drivers of Dissolved Carbon Dioxide and Methane Concentrations in the Nantiaoxi River System in the Upper Reaches of the Taihu Lake Basin During Summer-Autumn]

Inland waters are vital sinks for active carbon (C) and potential sources of greenhouse gas emissions. In this study, the characteristics of dissolved carbon dioxide (CO₂) and methane (CH₄) concentrations in the Nantiaoxi River system in the upper reaches of the Taihu Lake basin were observed between Jul. 2019 and Nov. 2019 (summer and autumn) using headspace equilibration-gas chromatography. Simultaneously, physical and chemical parameters were also determined to understand the factors influencing dissolved CO₂ and CH₄ concentrations. The results showed that the mean dissolved CO₂ concentrations and saturation levels in water were (505.47±16.99) μg·L^-1 and (256.31±8.32)%, respectively, and the corresponding values for CH₄ were (1.88±0.09) μg·L^-1 and (5218.74±264.30)%, respectively. The saturation levels of dissolved CO₂ and CH₄ at all observation points were greater than 100%, indicating that the Nantiaoxi River system is a potential source of CO₂ and CH₄. The highest mean dissolved CO₂ concentrations in water were found in agricultural areas followed by residential and forest areas, and there were significant differences among the three land-use types. The mean dissolved CH₄ concentrations in the water in residential areas were significantly higher than those in agricultural area forest areas. The dissolved CO₂ concentrations, saturation levels of CO₂, dissolved CH₄ concentrations, and saturation levels of CH₄ in water were all negatively correlated with oxidation reduction potential (ORP) (P<0.01) and positively correlated with electrical conductivity (EC) (P<0.01). The discrepancies in chlorophyll (Chl-a), nitrate (NO₃^--N), total nitrogen (TN), and EC were the main reasons for differences in dissolved CO₂ concentrations among the different land use types. Phytoplankton growth could be promoted by the higher input of nitrogen pollutants into rivers in agricultural and residential areas, and respiration could be also enhanced, resulting in higher dissolved CO₂ concentrations. The higher concentrations of dissolved organic carbon (DOC) and ammonium nitrogen (NH₄⁺-N) in the water, and the water temperature in residential areas, were probably the main causes of the higher dissolved CH₄ concentrations. Rainfall also had some influence on dissolved CO₂ and CH₄ concentrations in the water associated with the different land use types. Specifically, higher concentrations of nitrogen pollutants and the enhancement of DOC were the main drivers of high dissolved CO₂ concentrations in agricultural areas as well as the higher dissolved CH₄ concentrations in residential areas following rainfall events.

[Efficacy and safety of neoadjuvant apatinib in combination with dose-dense paclitaxel and carboplatin in locally advanced triple negative breast cancer patients]

Objective: To observe the short-term efficacy and safety of apatinib in combination with dose-dense paclitaxel and carboplatin in locally advanced triple-negative breast cancer (TNBC) patients. Methods: From September 2018 to September 2019, 17 stage Ⅱ/Ⅲ TNBC patients were enrolled in this single arm, single center prospective phase Ⅱ study. They received neoadjuvant treatment of apatinib 250 mg per day, paclitaxel 175 mg/m(2) on 1(st) day and a dose of carboplatin according to the area under curve (AUC)=4 on 2(nd) day, every 14 days as a cycle. Results: By January 2020, 16 cases completed 4-7 cycles of apatinib treatment and 4-8 cycles of chemotherapy. The median cycles of apatinib treatment and chemotherapy were 5 cycles and 6 cycles, respectively. Two cases achieved complete responses (CR), 12 achieved partial responses (PR), 2 achieved stable diseases (SD) and no progressive disease was observed. The objective response rate (ORR) was 87.5%, disease control rate (DCR) was 100%. By January 2020, among 12 patients who received surgery, 8 achieved pathologic complete response (pCR, 66.7%). The grade Ⅲ/Ⅳ adverse events included: neutropenia, thrombocytopenia in 3 cases (18.8%) each, anemia, fatigue, arrhythmia and alanine aminotransferase (ALT) elevation in 1 case each. Apatinib was interrupted in 5 cases, and was discontinued in 3 cases; chemotherapy dosage was reduced in 1 case. Conclusion: Apatinib in combination with dose-dense paclitaxel and carboplatin neoadjuvant therapy are effective and well tolerated in locally advanced TNBC patients.

Reducing 3,4-dihydroxyphenylpyruvic acid to d-3,4-dihydroxyphenyllactic acid via a coenzyme nonspecific d-lactate dehydrogenase from Lactobacillus reuteri

AIMS

The purpose of this work was to find an efficient enzyme to synthesize d-3,4-dihydroxyphenyllactic acid (d-DSS).

METHODS AND RESULTS

Nineteen lactic acid bacteria strains were screened for production of d-DSS using 3,4-dihydroxyphenylpyruvic acid (DPA) as a substrate. Lactobacillus reuteri JN516 exhibited the highest d-DSS yield. A nonspecific coenzyme, d-lactate dehydrogenase (d-LDH82319), from L. reuteri JN516 with high DPA reducing activity was identified. This enzyme reduced DPA to form d-DSS with excellent optical purity (enantioselectivity >99%). Its molecular weight was 35 kDa based on SDS-PAGE migration. The Michaelis-Menten constant (Km ), turnover number (kcat ), and catalytic efficiency (kcat /Km ) of d-LDH82319 for DPA were 0·09 mmol l-1 , 2·17 s-1 and 24·07 (mmol l-1 )-1  s-1 , respectively, with NADH as the coenzyme. The (Km ), (kcat ) and (kcat /Km ) of d-LDH82319 for DPA were 0·10 mmol l-1 , 0·13 s-1 and 1·30 (mmol l-1 )-1  s-1 , respectively, with NADPH as the coenzyme. The optimum temperature and pH of d-LDH82319 were 25°C and pH 8 respectively. Additionally, d-LDH82319 had a broad substrate range for alpha-keto acids, among which the activity of reducing pyruvate was the strongest; therefore, it belongs to the group of d-lactate dehydrogenases. d-LDH82319 and glucose dehydrogenase (GDH) were coexpressed to produce d-DSS from DPA.

CONCLUSIONS

d-LDH82319 from L. reuteri JN516 with high DPA reducing activity has the characteristics of a nonspecific coenzyme.

SIGNIFICANCE AND IMPACT OF THE STUDY

d-LDH82319 is the first reported coenzyme nonspecific d-lactate dehydrogenase with DPA-reducing activity. The coexpression system provided an effective method to produce d-DSS.

Root-soil air gap and resistance to water flow at the soil-root interface of Robinia pseudoacacia

During periods of water deficit, growing roots may shrink, retaining only partial contact with the soil. In this study, known mathematical models were used to calculate the root-soil air gap and water flow resistance at the soil-root interface, respectively, of Robinia pseudoacacia L. under different water conditions. Using a digital camera, the root-soil air gap of R. pseudoacacia was investigated in a root growth chamber; this root-soil air gap and the model-inferred water flow resistance at the soil-root interface were compared with predictions based on a separate outdoor experiment. The results indicated progressively greater root shrinkage and loss of root-soil contact with decreasing soil water potential. The average widths of the root-soil air gap for R. pseudoacacia in open fields and in the root growth chamber were 0.24 and 0.39 mm, respectively. The resistance to water flow at the soil-root interface in both environments increased with decreasing soil water potential. Stepwise regression analysis demonstrated that soil water potential and soil temperature were the best predictors of variation in the root-soil air gap. A combination of soil water potential, soil temperature, root-air water potential difference and soil-root water potential difference best predicted the resistance to water flow at the soil-root interface.

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 β-glucosidases, but none of the recognised lignin-degrading enzymes.

Low-dose 5-fluorouracil induces cell cycle G2 arrest and apoptosis in keloid fibroblasts

BACKGROUND

Intralesional injection of low-dose 5-fluorouracil (5-FU) has recently been used as an experimental modality for treating keloid scarring and has shown promising efficacy in improving scar appearance and preventing recurrence of the keloid.

OBJECTIVES

We sought to explore the cellular- and molecular-based evidence for the observed clinical benefits.

METHODS

Primary cell lines of keloid fibroblasts were treated with 5-FU at a range of lower doses (∼10 mg mL(-1) ) in monolayer culture and subjected to examination for cell viability, proliferative potential, apoptosis, cell cycle and associated proteins involved in cell cycle control.

RESULTS

5-FU significantly inhibited cell proliferation of keloid fibroblasts in the full dose range used in this study. The DNA synthesis was completely inhibited by 5-FU at 72 h, and significant cell apoptosis was observed at concentrations ≥ 1 mg mL(-1) for a period over 72 h. 5-FU caused a significant delay in cell cycle progression and the G2/M phase arrest. 5-FU induced p53 and p21 accumulation together with a decrease in cyclin B1 and Bcl-2 levels in treated keloid fibroblasts.

CONCLUSIONS

Our data indicate that low-dose 5-FU (as low as 1 mg mL(-1) ) induces significant inhibition of proliferation, G2/M cell cycle arrest and apoptosis but not immediate cell death of keloid fibroblasts. The lack of tissue necrosis is a particular benefit as further scarring is likely to be prevented. These results support the use of low-dose 5-FU as a potential modality for treating keloid scars.

A novel nonionic surfactant- and solvent-stable alkaline serine protease from Serratia sp. SYBC H with duckweed as nitrogen source: production, purification, characteristics and application

A novel nonionic surfactant- and hydrophilic solvent-stable alkaline serine protease was purified from the culture supernatant of Serratia sp. SYBC H with duckweed as nitrogen source. The molecular mass of the purified protease is about 59 kDa as assayed via SDS-PAGE. The protease is highly active over the pH range between 5.0 and 11.0, with the maximum activity at pH 8.0. It is also fairly active over the temperature range between 30 and 80°C, with the maximum activity at 40°C. The protease activity was substantially stimulated by Mn(2+) and Na(+) (5 mM), up to 837.9 and 134.5% at 40°C, respectively. In addition, Mn(2+) enhanced the thermostability of the protease significantly at 60°C. Over 90% of its initial activity remained even after incubating for 60 min at 40°C in 50% (v/v) hydrophilic organic solvents such as DMF, DMSO, acetone and MeOH. The protease retained 81.7, 83.6 and 76.2% of its initial activity in the presence of nonionic surfactants 20% (v/v) Tween 80, 25% (v/v) glycerol and Triton X-100, respectively. The protease is strongly inhibited by PMSF, suggesting that it is a serine protease. Washing experiments revealed that the protease has an excellent ability to remove blood stains.

Structural and Functional Analysis of Giant Strong Component of Bacillus thuringiensis Metabolic Network

The purpose of this work was to study the giant strong component (GSC) of B. thuringiensis metabolic network by structural and functional analysis. Based on so-called “bow tie” structure, we extracted and studied GSC with its functional significance. Global structural properties such as degree distribution and average path length were computed and indicated that the GSC is also a small-world and scale-free network. Furthermore, the GSC was decomposed and functional significant for metabolism of these divisions were investigated by comparing to KEGG metabolic pathways.

[Relationships of soil physical and microbial properties with nitrous oxide emission under effects of freezing-thawing cycles]

Freezing-thawing cycles often occurs in the regions of mid-high latitude and high altitude. This process can affect soil physical and biological properties, e.g., soil water status, aggregate stability, and microbial biomass and community structure. Under its effects, the bio-indicators of soil microbes, i.e., the kinds and quantities of some specific amino sugars varied, and the course and intensity of soil nitrogen transformation changed, which resulted in an increase of nitrous oxide (N2O) production and emission, and made the soil be a major source of N2O emission. This paper summarized the research progress on the aspects mentioned above, with the further research directions on the theoretical problems of soil N2O production and emission under effects of freezing-thawing suggested.

Efficiency and structure-activity relationship of the antioxidant action of resveratrol and its analogs

Resveratrol and its analogs, six other polyhydroxystilbenes, were synthesized and their antioxidative activities were evaluated in vitro by determination of the levels of malondialdehyde and hydrogen peroxide. Results clearly exhibited that resveratrol and its analogs had various potencies in inhibiting lipid peroxidation in rat brain, kidney, and liver homogenates and rat erythrocyte hemolysis. Several polyhydroxystilbenes were found to be more active than resveratrol in these models, and structure-activity relationship studies on polyhydroxystilbenes are described in this paper.

Cladonia furcata polysaccharide induced apoptosis in human leukemia K562 cells

AIM

To study whether Cladonia furcata polysaccharide (CFP-1) might induce apoptosis in human leukemia K562 cells.

METHODS

Inhibition of proliferation was measured by MTT assay. Morphological assessment of apoptosis was performed with fluorescence microscope and electron microscope. DNA fragmentation was visualized by agarose gel electrophoresis. The amount of apoptosis cells was measured by flow cytometry.

RESULTS

CFP-1 (50 - 800 mg/L) inhibited K562 cell proliferation in a concentration-dependent manner. After incubation of K562 cells with CFP-1 300 mg/L for 5 d, morphological changes of typical apoptosis were observed and agarose gel electrophoresis of DNA revealed "ladder" pattern.

CONCLUSION

CFP-1 induced apoptosis in human leukemia K562 cells.

Production and distribution of endoglucanase, cellobiohydrolase, and beta-glucosidase components of the cellulolytic system of Volvariella volvacea, the edible straw mushroom

The edible straw mushroom, Volvariella volvacea, produces a multicomponent enzyme system consisting of endo-1,4-beta-glucanase, cellobiohydrolase, and beta-glucosidase for the conversion of cellulose to glucose. The highest levels of endoglucanase and cellobiohydrolase were recorded in cultures containing microcrystalline cellulose (Avicel) or filter paper, while lower but detectable levels of activity were also produced on carboxymethyl cellulose, cotton wool, xylitol, or salicin. Biochemical analyses of different culture fractions in cultures exhibiting peak enzyme production revealed that most of the endoglucase was present either in the culture filtrate (45.8% of the total) or associated with the insoluble pellet fraction remaining after centrifugation of homogenized mycelia (32.6%). Cellobiohydrolase exhibited a similar distribution pattern, with 58.9% of the total enzyme present in culture filtrates and 31.0% associated with the pellet fraction. Conversely, most beta-glucosidase activity (63.9% of the total) was present in extracts of fungal mycelia whereas only 9.4% was detected in culture filtrates. The endoglucanase and beta-glucosidase distribution patterns were confirmed by confocal laser scanning microscopy combined with immunolabelling. Endoglucanase was shown to be largely cell wall associated or located extracellularly, with the highest concentrations being present in a region 1 to 2 microm wide immediately adjacent to the outer surface of (and possibly including) the hyphal wall and extending 60 to 70 microm from the hyphal tip. Immunofluorescence patterns indicated little if any intracellular endoglucanase. Most beta-glucosidase was located intracellularly in the apical area extending 60 to 70 microm below the hyphal tip, although enzyme was also evident in the extracellular region extending approximately 15 microm all around the hyphal tip and trailing back along the length of the hypha. The regions of the hypha located some distance from the apical region appeared to be devoid of intracellular beta-glucosidase, and the enzyme appears to be associated almost exclusively with, or located on the outside surface of, the hyphal wall.