Indicator Of Fungal Biomass Research Articles

Spatial location of carbon decomposition in the soil pore system

SummaryWe sought to examine the distribution of carbon (C) decomposition within the framework of the soil pore system. Soils were sampled from a transect having a natural gradient in pore‐size distribution. After the addition of labelled wheat straw (13C) the repacked soil columns were incubated (25°C) at soil water matric potentials of either −75 kPa or −5 kPa and for either 4 or 90 days. Pore‐size distribution was determined for each soil column after incubation and soils were then analysed for soluble C, label‐derived residual C, label‐derived and native biomass C, nematode abundance, and ergosterol concentration as an indicator of fungal biomass. Overall, the data suggested that pore‐size distribution and its interaction with soil water give rise to a highly stratified biogeography of organisms through the pore system. This results in different rates of decomposition in pores of different size. Added plant material seemed to decompose most rapidly in soils with a relatively large volume of pores with neck diameters c. 15–60 µm and most slowly in soils with large volumes of pores with neck diameters < 4 µm. Regression analysis suggested that at matric potentials of both −75 kPa and −5 kPa the fastest decomposition of organic substrate occurred close to the gas–water interface. This analysis also implied that slower rates of decomposition occur in the pore class 60–300 µm. Correlations between the mass of soil biota and the pore volume of each pore class point to the importance of fungi and possibly nematodes in the rapid decomposition of C in the pores c. 15–60 µm during the early stages of decomposition.

Ergosterol as an indicator of mould growth on building materials

Ergosterol was used as a specific indicator of fungal biomass to determine and assess mould growth on damp building material. The samples were saponified, cleaned up on a silica gel column and the sterols silylated and analysed by gas chromatography and mass spectrometry in MS/MS mode. Ninety-one samples of building materials from damp rooms were analysed including plaster, plaster/paint, paint, wood-chip wallpaper and paper wall covering. The concentrations of ergosterol ranged from 0.1 to 130 microg/g dry mass and depended on carbon content of the material. The highest concentrations were determined for wallpaper, the lowest for plaster and intermediate ones for paint. Based on ergosterol content and inspection of the room during sampling a rough classification of mould infestation is presented. The applicability of the ergosterol method was further tested in two case studies on the spatial distribution of fungi on damp walls and irregular distributions were found. With few exceptions the concentration of ergosterol in building materials was found to be a suitable indicator to estimate fungal biomass.

Dehydrodimers of Ferulic Acid in Maize Grain Pericarp and Aleurone: Resistance Factors to Fusarium graminearum

ABSTRACT The relationship between the primary cell wall phenolic acids, dehydrodimers of ferulic acid, and maize grain resistance to Fusarium graminearum, the causal agent of gibberella ear rot, was investigated. Concentrations of dehydrodimers of ferulic acid were determined in the pericarp and aleurone tissues of five inbreds and two hybrids of varying susceptibility and in a segregating population from a cross between a resistant and susceptible inbred. Significant negative correlations were found between disease severity and diferulic acid content. Even stronger correlations were observed between diferulic acid and the fungal steroid ergosterol, which is an indicator of fungal biomass in infected plant tissue. These results were consistent over two consecutive field seasons, which differed significantly for temperature and rainfall during pollination, the most susceptible stage of ear development. No correlation was found between the levels of these phenolics and deoxynivalenol levels. This is the first report of in vivo evidence that the dehydrodimers of ferulic acid content in pericarp and aleurone tissues may play a role in genotypic resistance of maize to gibberella ear rot.

Comparison of soil fungal/bacterial ratios in a pH gradient using physiological and PLFA-based techniques

We have compared the total microbial biomass and the fungal/bacterial ratio estimated using substrate-induced respiration (SIR) in combination with the selective inhibition technique and using the phospholipid fatty acid (PLFA) technique in a pH gradient (3.0–7.2) consisting of 53 mature broad-leaved forest soils. A fungal/bacterial biomass index using the PLFA technique was calculated using the PLFA 18:2ω6,9 as an indicator of fungal biomass and the sum of 13 bacterial specific PLFAs as indicator of the bacterial biomass. Good linear correlation ( p<0.001) was found between the total microbial biomass estimated with SIR and total PLFAs (totPLFA), indicating that 1 mg biomass-C was equivalent to 130 nmol totPLFA. Both biomass estimates were positively correlated to soil pH. The fungal/bacterial ratio measured using the selective inhibition technique decreased significantly with increasing pH from about 9 at pH 3 to approximately 2 at pH 7, while the fungal/bacterial biomass index using PLFA measurements tended to increase slightly with increasing soil pH. Good correlation between the soil content of ergosterol and of the PLFA 18:2ω6,9 indicated that the lack of congruency between the two methods in estimating fungal/bacterial ratios was not due to PLFA 18:2ω6,9-related non-fungal structures to any significant degree. Several PLFAs were strongly correlated to soil pH ( R 2 values >0.8); for example the PLFAs 16:1ω5 and 16:1ω7c increased with increasing soil pH, while i16:0 and cy19:0 decreased. A principal component analysis of the total PLFA pattern gave a first component that was strongly correlated to soil pH ( R 2=0.85, p<0.001) indicating that the microbial community composition in these beech/beech-oak forest soils was to a large extent determined by soil pH.

Decomposition of biodegradable packing materials jute, Biopol, BAK and their composites in soil

We investigated the effects of the biodegradable polymers jute, Biopol and BAK 2195 and their composites on the mineralisation activity and biomass of microorganisms in soil and on the fungal component of the microbial community. Two different pre-treatments of jute were used to produce the composites, treatment of the fibres with sodium hydroxide (SH-jute) and co-polymerisation with acrylonitrile (AN-jute). All products tested were highly degradable, as indicated by the increase in CO2 evolution after amendment. The additional amount of CO2-C evolved after polymer incorporation into the soil corresponded to between 21% and 34% of the added C after 85 days incubation at 25°C. The extra CO2-C evolved decreased in the order BAK > jute > Biopol. Composites of AN-jute were less mineralisable than those of SH-jute. Degradation of jute is characterised by a rapid increase, then a slow decline of microbial respiratory activity. In contrast, in the Biopol treatments, and especially in the BAK treatments, maximum CO2 evolution rates occurred considerably later, indicating that the soil microorganisms needed some time to colonise the polymer particles. All polymers and composites tested increased the soil microbial biomass in the order jute ≤ Biopol < BAK. The net increase in microbial biomass C was 3% of the added polymer C in the jute treatment, an average of 4% in the three Biopol treatments, and 7% in the three BAK treatments. The content of ergosterol, an indicator for fungal biomass, was also increased by all amendments, but the effect on ergosterol content was much more pronounced than on microbial biomass C.

Effect of pollutants on the ergosterol content as indicator of fungal biomass

Ergosterol content was determined in 20 white-rot fungi isolates and the values ranged from 2380 to 13 060 μg g −1 fungal biomass. Significant changes of ergosterol content according the physiological stage for Bjerkandera adusta 4312 and Coriolopsis gallica 8260 were found, showing the highest values during the stationary phase. However, in the case of Phanerochaete chrysosporium 3642, no changes were detected during growth. The effect of pollutants, such as heavy metals and fungicides, on the ergosterol content of C. gallica was determined. Heavy metals (Cu 80 ppm, Zn 50 ppm or Cd 10 ppm) and fungicides (thiram 3 ppm or pentachlorophenol 1.5 ppm) at concentrations that reduce the metabolic activity between 18% and 53% (pollutant-stressed cultures) did not affect the ergosterol content. Only the fungicide zineb (25 ppm) reduced significantly the ergosterol content in biomass basis. In soil experiments with Cu (80 ppm) or thiram (10 ppm) after 15 and 30 days of incubation, the ergosterol content in soil was linearly correlated to the fungal biomass C in both polluted and control soil cultures. The ergosterol content was independent of the presence or the absence of pollutants. Thus, these results indicate that ergosterol can be a useful indicator for fungal biomass in polluted soils, and can be applied for monitoring bioremediation processes.

Interrelationships between microbial and soil properties in young volcanic ash soils of Nicaragua

The activity and biomass of soil microorganisms were measured in soils from 25 different arable sites in the Pacific region of Nicaragua with the objective of elucidating their interrelationship with soil textural and soil chemical properties. All soils developed from recent volcanic deposits but differ in their particle size distribution. Short-term phosphorus fixation capacity varied widely and was, on average, 11% of added P. In contrast, long-term P fixation capacity varied within a small range of around 55%. Mean basal respiration was 8.6 μg CO 2–C d −1 g −1 soil, average contents of biomass C, biomass P, and ergosterol as an indicator of fungal biomass were 116, 1.95, and 0.34 μg g −1 soil, respectively. They were all, except biomass P, significantly lower in the sandy than in the loamy soils. The mean biomass C-to-soil C ratio was 0.69%, the mean metabolic quotient 95 mg CO 2–C d −1 g −1 biomass C, the mean ergosterol-to-biomass C ratio 0.31% and the mean biomass C-to-P ratio 107. The very low ergosterol-to-biomass C ratio indicates that fungi contribute only a relatively small percentage to the microbial biomass. The biomass C-to-P ratio exceeded considerably the soil C-to-total P ratio. Metabolic quotient qCO 2 and ergosterol-to-biomass C were both negatively correlated with biomass C-to-soil C ratio and clay content, indicating positive correlations between qCO 2 and ergosterol-to-biomass C ratio and between biomass C-to-soil C ratio and clay content. Key problems of soil fertility and soil quality in Nicaragua are low availability of soil organic matter and phosphorus to soil microorganisms, which are magnified by a low percentage of fungi, probably reducing the ability of soil to provide nutrients for plant growth.

Hydroperiod Influence on Breakdown of Leaf Litter in Cypress-gum Wetlands

Many cypress-gum wetlands in the southeast United States are isolated from rivers and streams and are seasonally inundated by rainfall. Organic matter processing in these wetlands is caused primarily by biotic components (i.e., microbes and invertebrates), which are influenced by timing and duration of seasonal inundation, and low dissolved oxygen levels. Using litter bags, we examined breakdown of cypress (Taxodium spp.) and gum (Nyssa sylvatica var. biflora) leaves in three wetlands with different hydroperiods: (1) flooded exposed (FE; 5 mo flooded/6 mo litter exposed), (2) multiple flooded exposed (MFE; 6 mo flooded/exposed/flooded/exposed) and (3) permanently flooded (PF; 11 mo flooded). Breakdown was fastest in the MFE wetland suggesting cycles of wetting and drying accelerated decomposition by promoting microbial activity through aeration. Even though ergosterol content, an indicator of fungal biomass on the litter, was similar among wetlands, we hypothesized that within the MFE wetland microbial activity was promoted by exposed conditions, but during subsequent flooding microbial biomass was kept at a low level by invertebrate consumers. Macroinvertebrate density and biomass were comparable between litter types, but were highest in the PF wetland, followed by MFE, then FE wetlands. Chironomids, oligochaetes, Caecidotea and Crangonyx were the dominant taxa indicating litter inputs are vital in maintaining the aquatic foodweb in this system. Cypress litter (k = −1.61 y−1) had faster breakdown rates than gum litter (k = −1.02 y−1), most likely because of plant morphology and greater surface area available to microbial decomposers. Ergosterol (mg g−1 AFDM leaf material) levels were higher on cypress (34.5) than gum (22.5) litter. In both litter types initial C:N and N:P ratios were >20, and C:P ratios were >500, indicating a possible P or N/P co-limitation in cypress-gum wetlands. Elemental gains or losses in litter were influenced predominantly by litter type and to a lesser extent by hydrologic regime. Gum leaves accumulated P, N, Ca and K and lost Mg, whereas cypress leaves had initial declines of these elements, followed by some accumulations in P and K. Temporal patterns of P showed that the drier sites (FE and MFE) immobilized more P than the wetter site (PF), suggesting that exposed conditions promoted microbial activity. In addition, N and P accumulations on gum leaves were highest in the summer at the time when wetlands would normally dry, indicating a seasonal period when moisture and temperature conditions are optimal for microbial growth. Net flux rates to the 1 y-old component of litter indicated that the FE wetland is accumulating more organic matter (172 g m−2 y−1) than the other wetlands (65 and 72 g m−2 y−1), which we attributed to higher cypress litter production. We concluded that hydrologic regime influences breakdown rates and element accumulations, but that net productivity is more important in determining litter accumulation rates.

Altitudinal Differences in Organic Matter Mass Loss and Fungal Biomass in a Subalpine Coniferous Forest, Mt. Fuji, Japan

In order to study the long-term effect of climatic conditions on organic matter decomposition, the difference in the mass loss rate of organic substrates was examined along the altitudinal temperature gradient (1500–2400 m) of Mt. Fuji, Japan. Two standard substrates, cellulose filter paper and wood chips of beech (Fagus crenata), were placed in the L and FH layers at each altitude. The mass loss rates tended to be smaller with increasing altitude and were significantly correlated with the annual mean air temperature in a log-linear fashion. The temperature dependence of the mass loss rates was much larger than that of microbial respiration. The initial increase in ergosterol content (an indicator of fungal biomass) of organic substrates was more rapid at low altitudes than at higher altitudes. The effects of fungal biomass and freezing temperatures on the temperature dependence of decomposition were examined using a simple simulation model. The results suggest that the effects of temperature increase on decomposition could be much larger than those estimated from the temperature-microbial respiration curves.

A logistic model of subsurface fungal growth with application to bioremediation

The goal of this research was to determine the potential of the fungal sterol ergosterol as an indicator of fungal biomass and to determine the growth response of the transformed strain of T. virens (GvT6) to added substrate and changes in temperature. Experiments in liquid culture and agar plates containing a rich medium of glucose, yeast extract, and casein (GYEC), or a soil extract medium supplemented with maltose (SE) showed that the ergosterol content of GvT6 was greatest when grown on GYEC agar plates (14.02 mg/g dry biomass). For both media, plate cultures produced higher specific ergosterol values than liquid cultures. Changes in specific ergosterol values over time were generally not significant. A value of 5.41 mg ergosterol / g dry biomass, determined for SE plate cultures, was used to convert ergosterol values to biomass values in growth experiments in soil bioreactors. Data from experiments in soil bioreactors treated with different levels of substrate (0.5–8 mg maltose / g dry soil) at three different temperatures (22, 27, 32°C) showed subsurface growth of GvT6 can be described by the logistic equation. Culture conditions of 32°C and 8 mg/g substrate produced the highest levels of biomass, but growth at 32°C and 4 mg/g substrate was somewhat faster than at the higher substrate level.

Distribution of Ergosterol in Organically and Conventionally Cultivated Agricultural Soils

ABSTRACT Ergosterol is generally assumed to be one of the best indicators of fungal biomass and soil quality. The present case studies describe variations in ergosterol content in soil, sampled at three Danish farms. One is organically cultivated according to the biodynamical principles (ORG). The other two are conventionally cultivated, one with animal husbandry (CONV-H) and one with plant production (CONV-P). The analytical method combined extraction in a microwave oven, clean-up with a new SPE sorbent material (OasisTM), and quantification by HPLC. The average estimated concentrations of ergosterol were 1.66 μg g−1 in ORG, 2.35 μg g−1 in CONV-H and 1.13 μg g−1 in CONV-P. These results correlated well with some of the important variables in the management systems of the soils (frequency of grass and clover, input of animal manure, total-C, frequency of ploughing). However, the exact causal relationships cannot be revealed using the case-study approach. The statistical analysis of the spatial variation in ergosterol across the field demonstrated very clearly that in some soils, small-scale (few cm2) variations in ergosterol concentrations may be quite large in comparison with large scale (few hundred m2) variations. This should be taken into account when planning the sampling strategy.

Influence of residential fungal contamination on peripheral blood lymphocyte populations in children.

Reported residential fungal contamination has been associated consistently with increased symptoms among occupants; however, an objective measure of a health effect is lacking, and a pathophysiologic mechanism has not been established. Our objective was to determine if exposure to indoor fungal contamination influenced T-cell differentiation. In this study, we contrasted lymphocyte populations, measured by flow cytometry, between a group of children who lived in homes with considerable fungal contamination (n = 39) and a group in less-contaminated homes (n = 20). Indicators of fungal biomass were viable fungi in house dust and air ergosterol in the child's bedroom. Living in a more-contaminated home versus a less-contaminated home was associated with a larger number of CD3+ T cells expressing CD45RO (1.5 x 10(9)/I versus 1.1 x 10(9)/I, respectively; p = .05, two-tailed t testing) and a reduced CD4/CD8 ratio (1.6 versus 1.8, respectively; p = .04). The differences persisted over a 12-mo period, and they were not explained by the child's age or total serum IgE, dust mite antigens, and the presence of furry or feathered pets or a humidifier. The results suggest that residential fungal contamination leads to chronic stimulation of children's lymphocytes.

Chitin and ergosterol combined to measure total and living fungal biomass in ectomycorrhizas

We have studied the chitin and ergosterol contents of ectomycorrhizal roots in three sets of experiments to evaluate them as indicators of fungal biomass. The first set of experiments showed that ageing had a marked effect on ergosterol concentrations. The ergosterol content of 7‐month‐old, brown, shrunken Pinus sylvestris L.–Paxillus involutus (Fr.) Fr. mycorrhizas was found to be only 10% of that found in white, turgid, 1‐ or 4‐month‐old specimens. This supports the hypothesis that the compound is a good indicator of living fungal biomass. Ageing had a lesser effect on chitin concentrations since the chitin levels found in 7‐month‐old mycorrhizas were still 60% of the levels found in 1‐ and 4‐month‐old specimens.Consequently, the chitin∶ergosterol ratio increased from about 14 to 19 in 1‐ and 4‐month‐old mycorrhizas respectively to about 110 in 7‐month‐old mycorrhizas. In the second set of experiments, we found that variation in plant growth had no effect on the chitin∶ergosterol ratio in whole root systems of either Alnus incana (L.) Moench or Pinus sylvestris mycorrhizal with Paxillus involutus. In the third set of experiments, we found a constant relationship between the two marker concentrations in 10‐month‐old root systems of Pinus sylvestris, regardless of fungal species involved, using Paxillus involutus, Piloderma croceum Erikss. &amp; Hjorts and Suillus variegatus (Fr.) O. Kuntze as test organisms. Taken together, the results of this study suggest that both chitin and ergosterol give reliable, but different, relative measures of fungal biomass in mycorrhizal roots. Furthermore, we demonstrate that, in combination, the two chemical markers can be used to estimate both total and living fungal biomass (derived from the chitin∶ergosterol ratio).

Comparison Between a Culture Plate Method and an Immunoassay to Evaluate Vascular Colonization of Potato by Verticillium dahliae.

Vascular colonization by Verticillium dahliae of 14 potato (Solanum tuberosum) cultivars was evaluated in field trials by a culture plate method and an indirect competitive enzyme-linked immunosorbent assay (IC-ELISA). Whereas the culture plate technique quantifies fungal propa-gules, the monoclonal antibody-based immunoassay detects the soluble antigen, providing an indicator of fungal biomass. Differences in vascular colonization were evident with both methods; thus, cultivars could be ranked as susceptible, intermediate, or resistant. Linear regression analysis of means of each cultivar showed correlation coefficients (r2) ranging from -0.606 to -0.835. Spearman's rank correlation coefficient (rs) ranged from -0.65 to -0.91. Estimation by IC-ELISA of vascular colonization by V. dahliae in potato is as accurate as that by the culture plate technique, and results can be obtained in 3 days with an approximately 50% reduction in costs of materials and reagents. This quantitative immunoassay can be applied in potato breeding programs to evaluate resistance to Verticillium wilt.

The use of phospholipid fatty acid analysis to estimate bacterial and fungal biomass in soil

The cell content of 12 bacterial phospholipid fatty acids (PLFA) was determined in bacteria extracted from soil by homogenization/centrifugation. The bacteria were enumerated using acridine orange direct counts. An average of 1.40×10-17 mol bacterial PLFA cell-1 was found in bacteria extracted from 15 soils covering a wide range of pH and organic matter contents. With this factor, the bacterial biomass based on PLFA analyses of whole soil samples was calculated as 1.0–4.8 mg bacterial C g-1 soil C. The corresponding range based on microscopical counts was 0.3–3.0 mg bacterial C g-1 soil C. The recovery of bacteria from the soils using homogenization/centrifugation was 2.6–16% (mean 8.7%) measured by PLFA analysis, and 12–61% (mean 26%) measured as microscopical counts. The soil content of the PLFA 18:2ω6 was correlated with the ergosterol content (r=0.92), which supports the use of this PLFA as an indicator of fungal biomass. The ratio 18:2ω6 to bacterial PLFA is therefore suggested as an index of the fungal:bacterial biomass ratio in soil. An advantage with the method based on PLFA analyses is that the same technique and even the same sample is used to determine both fungi and bacteria. The fungal:bacterial biomass ratio calculated in this way was positively correlated with the organic matter content of the soils (r=0.94).

Vitality fertilization of Scots pine stands growing along a gradient of heavy metal pollution: short-term effects on microbial biomass and respiration rate of the humus layer.

In 1992 forest vitality fertilization experiments were established on a heavy metal deposition gradient with four treatments in three replications at distances of 0.5, 4 and 8 km from a Cu-Ni smelter in order to estimate their impact on the disturbed forest ecosystem. The increase in Cu concentration in the humus (F/H) layer of the Calluna site type Scots pine (Pinus sylvestris) stands from ca. 300 to 8000 mg kg(-1) d.m. (dry matter) along the 8 km long transect towards the smelter resulted in declining soil microbial biomass and soil respiration activity. Three independent measurements of microbial biomass: C(mic)-FE (fumigation extraction), C(mic)-SIR (substrate induced respiration), and ATP have been used together with an indicator of fungal biomass (ergosterol) and microbial activity (soil respiration). Within this Cu pollution range, all the measured microbial biomass levels declined to 10%-28% of the control plot values and activity assessed by respiration was lowered to 16%. Liming has increased the C(mic)-SIR and respiration rate. Treatments with test fertilizer, made from grounded apatite, did not result in different microbial biomass and respiration rate values compared to the respective controls along the whole gradient. Nitrogen + lime treatments resulted in similar changes to lime alone. No changes, as compared to the respective control, could be detected with nitrogen fertilization at the less polluted end of the gradient.

Food selection in three leaf-shredding stream invertebrates

Leaf disks (Betula papyrifera) were conditioned for two weeks by six species of aquatic hyphomycetes. Mass losses of the leaves were determined, and their concentrations of protein (extracted at pH 7, 10 and 12.8), phenolics (Folin-Ciocalteu and BSA-precipitation), lipids, and ergosterol (as indicator of fungal biomass) were measured. Enzymatic activities of the culture filtrates against cellulose, xylan and pectin were estimated. Gammarus tigrinis, Pycnopsyche guttifer and Tipula caloptera were given a choice of the six leaf/fungus combinations. G. tigrinus and P. guttifer consistently preferred some combinations over others; T. caloptera appeared to feed randomly. There were no significant correlations between consumption and any of the measured characteristics of leaf disks. With G. tigrinus and P. guttifer, the sequence of preference could be reproduced by extracting mycelia with non-polar solvents and applying the extracts to unconditioned leaf disks. Consumption of extract-coated disks was lower than consumption of conditioned disks. Numbers of endosymbiotic gut bacteria increased from G. tigrinus to P. guttifer to T. caloptera; diet diversity showed the opposite trend.

Quantification of fungal hyphae in leaves of deciduous trees by automated image analysis

An optical method to quantify the fungal hyphae within decomposing leaves of deciduous trees was developed. The plant matrix was partially destroyed under hydrolytic conditions, and fungal hyphae and cellulose residues within the leaves were stained with Calcofluor M2R. Cellulose residues were subsequently depolymerized by cellulase, and fungal hyphae were separated from the remaining plant matrix with a pressurized air-water mixture. An image analysis program to quantify the fungal hyphae was written. The program included the recognition of fungal hyphae, the elimination of stomata from the images, and the measuring of lengths of fungal hyphae. The optical method was verified by a chemical method relying on glucosamine as an indicator of fungal biomass. The fungal biomass in leaves of Fagus silvatica and Quercus petraea at early states of decomposition was 0.2 to 0.4% of the leaf weight. The biomass reached a maximum within 2 to 4 weeks (optical method, 0.5 to 0.7%; chemical method, 1 to 1.4% of the initial leaf weight) and decreased thereafter.

A critical assessment of the validity of ergosterol as an indicator of fungal biomass

The relationship between ergosterol content and biomass of nine species of aquatic hyphomycetes was examined. Biomass was manipulated by varying incubation period and subdividing mycelial mats. Similar results were obtained for both methods. In only three species (Flagellospora curvula, Tetrachaetum elegans and Tetracladium marchalianum) was there a significant regression between mycelial ergosterol content and biomass. Interspecific variation in ergosterol content was also evident. Consequently, even when studying assemblages of species for which direct relationships between ergosterol and biomass occur, ergosterol could still be an unreliable measure of total biomass. This assay must therefore be viewed with caution.

Effects of ruminal protozoa on cellulose degradation and the growth of an anaerobic ruminal fungus, Piromyces sp. strain OTS1, in vitro

An anaerobic rumen fungus, Piromyces sp. strain OTS1, was incubated in the presence or absence of a mixed, A-type, protozoal population obtained from a goat, in a medium containing filter paper cellulose as energy source and antibiotics to suppress bacterial growth. Fermentation end products, cellulose degradation, and chitin as an indicator of fungal biomass were examined. In the presence of protozoa, total volatile fatty acids, notably propionate and butyrate, increased, and lactate decreased. In fungus-protozoan coincubations, formate was not detected at the end of the experiment and the amount of reducing sugars remained low throughout the incubation period. The fungal growth in the coincubations was negatively affected. While protozoal predation on zoospores was one mechanism of inhibition, mature fungal cells were also affected. Total cellulose degradation was greater in fungal monocultures, but the amount of cellulose degraded per unit of fungal biomass was 25% larger in the coincubations. The negative effects that the protozoal predatory activity had on the fungal growth and subsequently on the amount of cellulose degraded by Piromyces sp. strain OTS1 were partially attenuated by the protozoal fibrolytic activity or by an enhanced fungal activity due to a more favorable environment.