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PubMed2003

Nutritional characteristics of the leaves of native plants growing in adverse soils of humid tropical lowlands.

Acid sulfate, peat, sandy podzolic, and saline soils are widely distributed in the lowlands of Thailand and Malaysia. The nutrient concentrations in the leaves of plants grown in these type of soils were studied with the aim of developing a nutritional strategy for adapting to such problem soils. In sago and oil palms that were well-adapted to peat soil, the N, P, and K concentrations were the same in the mature leaves, while the Ca, Mg, Na, and Fe concentrations were higher in the mature leaves of the oil palm than of the sago palm. Melastoma malabathricum and Melaleuca cajuputi plants that were well-adapted to low pH soils, peat. and acid sulfate soils were also studied. It was observed that a high amount of Al accumulated in the M. marabathricum leaves, while Al did not accumulate in M. cajuputi leaves. M. cajuputi plants accumulated large amounts of Na in their leaves or stems regardless of the exchangeable Na concentration in the soil, while M. malabathricum that was growing in saline-affected soils excluded Na. Positive relationships between macronutrients were recognized between P and N, between K and N, and between P and K. Al showed antagonistic relationships with P, K, Ca, Mg, Fe, Zn, Cu, and Na. Na also showed antagonistic relationships with P, K, Zn, Mn, Cu, and Al. Fe showed weak antagonistic relationships with Zn, Mn, Cu, and Al.

Aluminum↗

PubMed2001

Radionuclides in raised bogs: a case study of Bór za Lasem.

Bór za Lasem is a raised bog in the Orawsko-Nowotarska Valley (southern Poland). About half of the Bór za Lasem area has been exploited while the rest is undisturbed. Peat samples from both parts of the bog were analysed. Measurements of 137Cs, 134Cs, 239,240Pu, 238Pu, 40K, 228Ra, and 226Ra activity concentrations in all samples were performed. Comparison of the results of radiocaesium and plutonium activity concentrations reveals the highest activity concentrations of radionuclides in the undisturbed part of the peat-bog area. The radiocaesium content decreased with depth, whereas the plutonium concentration had a maximum value at a depth of 15-20 cm. The lowest activity concentrations were found in the exploited part of the bog. Potassium and radium isotopes were detected only in shallow openings within the heavily exploited part of the bog, which might suggest partial mixing of the peat with the mineral sub-soil. The growth rate of the top layer of the undisturbed part of the bog obtained from plutonium distribution was estimated as approximately 0.5 cm per year.

Ecosystem↗

PubMed2002

Biological control of cucumber and sugar beet damping-off caused by Pythium ultimum with bacterial and fungal antagonists.

AIMS: Five bacterial strains belonging to Bacillus subtilis, Pseudomonas fluorescens and Ps. corrugata and two fungal strains belonging to Trichoderma viride and Gliocladium virens were evaluated for their efficacy in controlling sugar beet and cucumber damping-off caused by Pythium ultimum. METHODS AND RESULTS: The in vitro antagonistic activity of bacteria against various Pythium spp. was evaluated with dual cultures in various media. Pseudomonas strains inhibited the pathogen better than Bacillus strains. To identify potentially useful antagonist combinations, dual compatibility of antagonists was also evaluated, based on growth in two liquid media containing substrate previously used by other antagonists. Four pairs of bacteria were selected. Sugar beet damping-off biocontrol was attempted with bacterial seed treatments (individually and in pairs). Cucumber damping-off biocontrol was attempted with bacterial seed treatments and bacterial and fungal compost treatments. In sugar beet, satisfactory biocontrol was only achieved with Pseudomonas antagonists. Antagonist combinations did not show any superior biocontrol ability to individual antagonists and compatibility of bacteria in vitro did not correlate with compatibility in vivo. Bacterial seed treatments and fungal compost treatments failed to control cucumber damping-off. Better biocontrol in cucumber was achieved when bacterial antagonists were applied by drenching or by coating seed with bacteria in a peat carrier. CONCLUSIONS: Pseudomonas antagonists were superior to Bacillus antagonists in controlling damping-off in cucumber and sugar beet. Pseudomonas peat inocula maintained a good shelf-life 2 years after preparation. SIGNIFICANCE AND IMPACT OF THE STUDY: Pseudomonas peat formulations have the potential for development into commercial biopesticides.

Bacillus subtilis↗

PubMed2004

Plant regeneration from encapsulated nodal segments of Dalbergia sissoo Roxb., a timber-yielding leguminous tree species.

One of the alternative methods adopted in recent years is to use biotechnological approaches for improving the tree species. The synthetic seeds offer several advantages, e.g., easy handling, storability, reduced size of propagules, and transportability. Germplasm can be effectively stored in the form of synthetic seeds. A protocol has been developed for plant regeneration from encapsulated nodal segments of Dalbergia sissoo Roxb. Nodal segments collected from basal sprouts of mature trees were encapsulated in calcium alginate beads. Inability of nodal segments entrapped in calcium alginate beads to form root was a major problem. To avoid this problem, an appropriate root induction treatment was given to nodal segments for 10 days, prior to encapsulation to allow formation of root primordia. For synthetic seeds production and subsequent conversion into plantlet, nodal segments with root primordia were encapsulated using sodium alginate and calcium chloride as gelling matrix. The best gel complexation was achieved using 3% sodium alginate and 75 mmol/L CaCl2 2H2O. Maximum percentage response (85%) for conversion of encapsulated nodal segments into plantlets was achieved on 1/2-MS medium without plant growth regulators, after 25 days of culture. The frequency of conversion of encapsulated nodal segments into plantlets affected by the concentration of sodium alginate, and the presence or absence of 1/2-MS nutrients in calcium alginate beads. Plantlets with well developed roots and shoots were transferred to pots containing autoclaved mixture of peat moss and soil (1:1). Plants were also established in pots. The conversion of encapsulated nodal segments into plantlets also occurred when calcium alginate beads having entrapped nodal segments were directly sown in autoclaved peat moss moistened with 1/2-MS0 medium. Out of 60 encapsulated nodal segments, in each experiments, stored at 4 degrees C for 30 days, 44 plants developed under in vitro conditions, and 27 on peat moss moistened with 1/2-MS0.

Agriculture↗

PubMed2003

Determination of the hydraulic residence time in a trickling biofilter filled with organic matter.

Biofiltration process using peat as media has been shown to be efficient for the treatment of agroindustrial, chemical and municipal effluents. However, determining the hydraulic retention time of this process is difficult due to many factors. Generally tracer techniques are used, but they measure the molecular retention time instead of the hydraulic retention time; and depending on the case, the results can be wrong. In order to contribute to solving this problem, the objective of this research was to find a trustworthy and adequate technique to determine the hydraulic retention time for a process using a very adsorbent filter bed material (peat). An overview of the hydraulic behaviour of a peat bed filter related to their particular structural composition is presented. Then, based on these characteristics, two different techniques to determine the hydraulic retention time were developed and tested. The first, an indirect modified tracing technique and, the second, a direct one which determines the volume of liquid in treatment into the filter bed through the establishment of a relation between the volume of porosity and the volume of empty spaces (or not occupied by liquid) into the filter bed. The results obtained showed that the proposed techniques gave similar results and proved adequate.

Biodegradation, Environmental↗

PubMed2005

Peatland hydrology and carbon release: why small-scale process matters.

Peatlands cover over 400 million hectares of the Earth's surface and store between one-third and one-half of the world's soil carbon pool. The long-term ability of peatlands to absorb carbon dioxide from the atmosphere means that they play a major role in moderating global climate. Peatlands can also either attenuate or accentuate flooding. Changing climate or management can alter peatland hydrological processes and pathways for water movement across and below the peat surface. It is the movement of water in peats that drives carbon storage and flux. These small-scale processes can have global impacts through exacerbated terrestrial carbon release. This paper will describe advances in understanding environmental processes operating in peatlands. Recent (and future) advances in high-resolution topographic data collection and hydrological modelling provide an insight into the spatial impacts of land management and climate change in peatlands. Nevertheless, there are still some major challenges for future research. These include the problem that impacts of disturbance in peat can be irreversible, at least on human time-scales. This has implications for the perceived success and understanding of peatland restoration strategies. In some circumstances, peatland restoration may lead to exacerbated carbon loss. This will also be important if we decide to start to create peatlands in order to counter the threat from enhanced atmospheric carbon.

Carbon↗

PubMed1996

Molecular biological evidence for the occurrence of uncultured members of the actinomycete line of descent in different environments and geographical locations.

A 16S rDNA based molecular ecological study was performed on a sample taken from a peat bog in Germany. Total DNA was extracted by directly lysing micro-organisms in the peat matrix. The 5' 1400 nucleotides of the bacterial 16S rDNA were amplified using conserved bacterial PCR primers. A clone library was generated by blunt-end cloning and 262 16S rDNA clones were analysed. Of these, 37 were located in the Gram-positive phylum, as determined by hybridization to an oligonucleotide probe specific for Gram-positive bacteria. Analysis of 17 of these clones by sequence analysis and their comparison with published sequences representing all of the main bacterial phyla indicated their membership of the actinomycete line of descent. These peat clones were found to represent three novel lineages, two of which appear to be related to the species Acidimicrobium ferrooxidans, and 'Candidatus Microthrix parvicella'. Clone sequences of the third group are phylogenetically related to Rubrobacter radiotolerans. Comparison with short 16S rDNA clone sequences obtained from DNA isolated from a geothermally heated soil in New Zealand, and from DNA isolated from soil in Australia, Japan and Finland and marine environments from the Atlantic and the Pacific Oceans, suggests that members of these three groups occur in very different environments across the world.

Actinomycetales↗

PubMed2004

An immunological approach to quantifying the saprotrophic growth dynamics of Trichoderma species during antagonistic interactions with Rhizoctonia solani in a soil-less mix.

Studies of the saprotrophic growth dynamics of Trichoderma species and their fungal hosts during antagonistic interactions are severely hampered by the absence of methods that allow the unambiguous identification and quantification of individual genera in complex environments such as soil or compost containing mixed populations of fungi. Furthermore, methods are required that allow discrimination between active hyphal growth and other components of fungal biomass such as quiescent spores that are produced in large numbers by Trichoderma species. This study details the use of monoclonal antibodies to quantify the saprotrophic growth dynamics of the soil-borne plant pathogen Rhizoctonia solani and biological control strains of Trichoderma asperellum and Trichoderma harzianum during antagonistic interactions in peat-based microcosms. Quantification was based on the immunological detection of constitutive, extracellular antigens that are secreted from the growing tip of Rhizoctonia and Trichoderma mycelium and, in the case of Trichoderma harzianum, from quiescent phialoconidia also. The Trichoderma-specific monoclonal antibody (MF2) binds to a protein epitope of the enzyme glucoamylase, which was shown by immunofluorescence and immunogold electron gold microscopy studies of Trichoderma virens in vitro to be produced at the origin of germ tube emergence in phialoconidia and from the growing tip of germ tubes. In addition, a non-destructive immunoblotting technique showed that the enzyme was secreted during active growth of Trichoderma asperellum mycelium in peat. The Rhizoctonia solani-specific monoclonal antibody (EH2) similarly binds to a protein epitope of a glycoprotein that is secreted during active mycelial growth. Extracts derived from lyophilized mycelium were used as a quantifiable and repeatable source of antigens for construction of calibration curves. These curves were used to convert the absorbance values obtained in ELISA tests of peat extracts to biomass equivalents, which allowed comparisons of the saprotrophic growth dynamics of the pathogen and antagonists to be made in single or mixed species microcosms. Trichoderma species were able to compete successfully with R. solani for nutrients and to prevent saprotrophic growth of the pathogen. Specificity of the Trichoderma quantitative assay was tested in non-sterile soil-based microcosms artificially inoculated with T. asperellum. The assay was highly specific and only detected T. asperellum population dynamics. No cross-reactivity was found with extracts from soil samples containing contaminant fungi.

Animals↗

PubMed1982

Dilution of liquid Rhizobium cultures to increase production capacity of inoculant plants.

Experiments were undertaken to test whether peat-based legume seed inoculants, which are prepared with liquid cultures that have been deliberately diluted, can attain and sustain acceptable numbers of viable rhizobia. Liquid cultures of Rhizobium japonicum and Rhizobium phaseoli were diluted to give 10, 10, or 10 cells per ml, using either deionized water, quarter-strength yeast-mannitol broth, yeast-sucrose broth, or yeast-water. The variously diluted cultures were incorporated into gamma-irradiated peat, and the numbers of viable rhizobia were determined at intervals. In all of the inoculant formulations, the numbers of rhizobia reached similarly high ceiling values by 1 week after incorporation, irrespective not only of the number of cells added initially but also of the nature of the diluent. During week 1 of growth, similar multiplication patterns of the diluted liquid cultures were observed in two different peats. Numbers of rhizobia surviving in the various inoculant formulations were not markedly different after 6 months of storage at 28 degrees C. The method of inoculant preparation did not affect the nitrogen fixation effectiveness of the Rhizobium strains.

Journal Article↗

PubMed1988

High Survivability of Cheese Whey-Grown Rhizobium meliloti Cells upon Exposure to Physical Stress.

Whey, a by-product of the dairy industry, has been found to protect the rhizobia cells during freezing and thawing. Cells of rhizobia grown on whey sustained freezing better at -18 degrees C than did cells grown on mannitol or sucrose. Suspensions of cells grown on whey or mannitol that were suspended in whey performed equally well at -18 and -80 degrees C, with 94 and 100% survival, respectively. Whey-grown rhizobia in pellets withstood desiccation better than did their mannitol-grown equivalents. Rhizobia that were grown on whey and then inoculated onto commercial peat showed a survival rate of 100% after 23 weeks at -4 degrees C. Whey-grown cells in peat performed better at various temperatures during storage, even when they were exposed to desiccation, than did mannitol-grown cells in peat. Whey, therefore, offers interesting possibilities as a Rhizobium protectant for the inoculum industry.

Journal Article↗

PubMed1989

Bradyrhizobium japonicum Survival in and Soybean Inoculation with Fluid Gels.

The utilization of gels, which are used for fluid drilling of seeds, as carriers of Bradyrhizobium japonicum for soybean (Glycine max (L.) Merr.) inoculation was studied. Gels of various chemical composition (magnesium silicate, potassium acrylate-acrylamide, grafted starch, and hydroxyethyl cellulose) were used, although the hydroxyethyl cellulose gels were more extensively investigated. Gel inocula were prepared by mixing gel powder with liquid cultures of B. japonicum (2% [wt/vol]). The population of B. japonicum USDA 110 did not change in each gel type during 8 days of incubation at 28 degrees C. These fluid gels were prepared with late-exponential-growth-phase cells that were washed and suspended in physiological saline. Mid-exponential-growth-phase B. japonicum USDA 110, 123, and 138 grew in cellulose gels prepared with yeast extract-mannitol broth as well as or better than in yeast extract-mannitol broth alone for the first 10 days at 28 degrees C. Populations in these cellulose gels after 35 days were as large as when the gels had originally been prepared, and survival occurred for at least 70 days. Soybeans grown in sand in the greenhouse had greater nodule numbers, nodule weights, and top weights with gel inoculants compared with a peat inoculant. In soil containing 10 indigenous B. japonicum per g of soil, inoculation resulted in increased soybean nodule numbers, nodule weights, and top weights, but only nodule numbers were greater with gel than with peat inoculation. The gel-treated seeds carried 10 to 10 more bacteria per seed (10 to 10) than did the peat-treated seeds.

Journal Article↗

PubMed1990

Distribution and rate of methane oxidation in sediments of the Florida everglades.

Rates of methane emission from intact cores were measured during anoxic dark and oxic light and dark incubations. Rates of methane oxidation were calculated on the basis of oxic incubations by using the anoxic emissions as an estimate of the maximum potential flux. This technique indicated that methane oxidation consumed up to 91% of the maximum potential flux in peat sediments but that oxidation was negligible in marl sediments. Oxygen microprofiles determined for intact cores were comparable to profiles measured in situ. Thus, the laboratory incubations appeared to provide a reasonable approximation of in situ activities. This was further supported by the agreement between measured methane fluxes and fluxes predicted on the basis of methane profiles determined by in situ sampling of pore water. Methane emissions from peat sediments, oxygen concentrations and penetration depths, and methane concentration profiles were all sensitive to light-dark shifts as determined by a combination of field and laboratory analyses. Methane emissions were lower and oxygen concentrations and penetration depths were higher under illuminated than under dark conditions; the profiles of methane concentration changed in correspondence to the changes in oxygen profiles, but the estimated flux of methane into the oxic zone changed negligibly. Sediment-free, root-associated methane oxidation showed a pattern similar to that for methane oxidation in the core analyses: no oxidation was detected for roots growing in marl sediment, even for roots of Cladium jamaicense, which had the highest activity for samples from peat sediments. The magnitude of the root-associated oxidation rates indicated that belowground plant surfaces may not markedly increase the total capacity for methane consumption. However, the data collectively support the notion that the distribution and activity of methane oxidation have a major impact on the magnitude of atmospheric fluxes from the Everglades.

Journal Article↗

PubMed1996

In Situ Analyses of Methane Oxidation Associated with the Roots and Rhizomes of a Bur Reed, Sparganium eurycarpum, in a Maine Wetland.

Methane oxidation associated with the belowground tissues of a common aquatic macrophyte, the burweed Sparganium eurycarpum, was assayed in situ by a chamber technique with acetylene or methyl fluoride as a methanotrophic inhibitor at a headspace concentration of 3 to 4%. Acetylene and methyl fluoride inhibited both methane oxidation and peat methanogenesis. However, inhibition of methanogenesis resulted in no obvious short-term effect on methane fluxes. Since neither inhibitor adversely affected plant metabolism and both inhibited methanotrophy equally well, acetylene was employed for routine assays because of its low cost and ease of use. Root-associated methanotrophy consumed a variable but significant fraction of the total potential methane flux; values varied between 1 and 58% (mean (plusmn) standard deviation, 27.0% (plusmn) 6.0%) with no consistent temporal or spatial pattern during late summer. The absolute amount of methane oxidized was not correlated with the total potential methane flux; this suggested that parameters other than methane availability (e.g., oxygen availability) controlled the rates of methane oxidation. Estimates of diffusive methane flux and oxidation at the peat surface indicated that methane emission occurred primarily through aboveground plant tissues; the absolute magnitude of methane oxidation was also greater in association with roots than at the peat surface. However, the relative extent of oxidation was greater at the latter locus.

Journal Article↗

PubMed1997

Variation in microbial community structure in two boreal peatlands as determined by analysis of phospholipid Fatty Acid profiles.

Analyses of phospholipid fatty acids (PLFAs) were used to assess variation in community structure and total microbial biomass in two boreal peatlands in Sweden. The total PLFA concentration in peat ranged from 0.16 to 7.0 nmol g of wet peat(sup-1) (median, 0.70 nmol g of wet peat(sup-1)). Principal-component analysis of PLFA data revealed that the degree of depth-related variation in PLFA composition was high among peatland habitats, with general differences between wet sites, with water tables within a few centimeters of the moss surface, and dry sites, with water tables >10 cm below the moss surface. However, variation in PLFA composition over the growing season was negligible. In the principal-component analyses, most PLFAs were determined to be parts of clusters of covarying fatty acids, suggesting that they originated in the same functional groups of microorganisms. Major clusters were formed by monounsaturated (typical of gram-negative eubacteria), terminally branched (gram-positive or anaerobic gram-negative eubacteria), methyl-branched and branched unsaturated (sulfate-reducing bacteria and/or actinomycetes), (omega)8 monounsaturated (methane-oxidizing bacteria), and polyunsaturated (eucaryotes) PLFAs. Within the clusters, PLFAs had rather distinct concentration-depth distributions. For example, PLFAs from sulfate-reducing bacteria and/or actinomycetes and those from methane-oxidizing bacteria had maximum concentrations slightly below and at the average water table depth, respectively.

Journal Article↗

PubMed2000

Development of formulations of biological agents for management of root rot of lettuce and cucumber.

The effect of various carrier formulations of Bacillus subtilis and Pseudomonas putida were tested on germination, growth, and yield of lettuce and cucumber crops in the presence of Pythium aphanidermatum and Fusarium oxysporum f.sp. cucurbitacearum, respectively. Survival of B. subtilis and P. putida in various carriers under refrigeration (about 0 degree C) and at room temperature (about 22 degrees C) was also studied. In all carrier formulations, B. subtilis strain BACT-0 survived up to 45 days. After 45 days of storage at room temperature (about 22 degrees C), populations B. subtilis strain BACT-0 were significantly higher in vermiculite, kaolin, and bacterial broth carriers compared with other carriers. Populations of P. putida were significantly higher in vermiculite, peat moss, wheat bran, and bacterial broth than in other carriers when stored either under refrigeration (about 0 degree C) or at room temperature (about 22 degrees C) for 15 or 45 days. Germination of lettuce seed was not affected in vermiculite, talc, kaolin, and peat moss carriers, but germination was significantly reduced in alginate and bacterial broth carriers of B. subtilis compared to the non-treated control. Germination of cucumber seed was not affected by any of the carriers. Significantly higher fresh lettuce and root weights were observed in vermiculite and kaolin carriers of B. subtilis compared with P. aphanidermatum-inoculated control plants. Lettuce treated with vermiculite, and kaolin carriers of B. subtilis, or non-inoculated control lettuce plants had significantly lower root rot ratings than talc, peat moss, bacterial broth, and P. aphanidermatum-inoculated control plants. Growth and yield of cucumber plants were significantly higher in vermiculite-based carrier of P. putida than the other carriers and Fusarium oxysporum f.sp. cucurbitacearum-inoculated plants.

Alginates↗

PubMed2001

Rhizobium population dynamics in the pea rhizosphere of rhizobial inoculant strain applied in different formulations.

The effect of inoculant formulation on the population dynamics of rhizobia in the pea rhizosphere was investigated using a streptomycin-resistant mutant of Rhizobium leguminosarum bv. viceae NITRAGIN128C56G (128C56G strR). The isolate was formulated into liquid, peat powder, and granular peat carriers, and was tested on pea at field sites near Saskatoon, Saskatchewan, and Beaverlodge, Alberta, in 1996 and 1997. The liquid and peat powder formulations were applied to seed while the granular inoculant was applied to soil. In three out of four site years, population dynamics were similar among formulations: an initial decline or lag period lasting 2-5 days followed by an increase to approximately 10(5) colony-forming units (CFU)/seedling by 14-28 days after planting (DAP) and, where sampled, a continuing increase from 10(7) to 10(8) CFU/plant at 63 DAP. In these same site years, nodule number (not determined at Beaverlodge in 1997) and nodule occupancy at 60 days were not significantly different among formulations. In contrast, soil populations of 128C56G strR from the liquid formulation declined to near zero by 28 DAP at Beaverlodge in 1996, when soil moisture was excessive in spring because of high rainfall. Populations increased in this treatment after this time, but remained significantly lower than the populations of the other two formulations throughout the sampling period. Pea seed yields were not significantly different among treatments in either year at Beaverlodge, but were significantly higher with granular inoculant than the noninoculated control in Saskatoon. Within inoculated treatments at Saskatoon, there were no significant differences in grain yield.

Colony Count, Microbial↗

PubMed2006

Methylation of p16 and Ras association domain family protein 1a during colorectal malignant transformation.

Accurate assessment of gene methylation in formalin-fixed, paraffin-embedded archived tissue (FF-PEAT) by microdissection remains challenging because the tissue volume is small and DNA is damaged. In addition, methods for methylation assessment, such as methylation-specific PCR (MSP), require sodium bisulfite modification (SBM) on purified DNA, which causes major loss of DNA. On-slide SBM, in which DNA is modified in situ before isolation of tumor cells, eliminates DNA purification steps and allows histology-oriented assessment of gene methylation. This study describes a protocol and use of on-slide SBM using 20 FF-PEAT of colorectal cancers with intratumoral adenoma components to detect accumulation of gene methylation during colorectal malignant transformation. Deparaffinized tissue sections were incubated in sodium bisulfite solution for 8 hours at 60 degrees C, stained with hematoxylin, and then microdissected. Proteinase K lysate was directly used as a template in subsequent PCR. Using on-slide SBM, 282-bp-long bisulfite direct sequencing was possible. Yield of modified DNA was 2.6-fold greater than standard SBM on average. The mean conversion rate was 97%, and false-positive or false-negative results were not observed in subsequent MSP. Intratumoral heterogeneity by accumulation of p16 and Ras association domain family protein 1a methylation during malignant transformation were shown by MSP comparing cancer with adenoma parts within a single section. On-slide SBM is applicable in most methylation studies using FF-PEAT. It allows detailed, intratumoral analysis of methylation heterogeneity within solid tumors. On-slide SBM will significantly improve our approach and understanding of epigenetic events in minimal disease and the carcinogenic process.

Alu Elements↗

PubMed1988

The microbial environment and intestinal nematode infections of Heligmosomoides polygyrus in laboratory mice.

The difficulty of establishing primary infections of Heligmosomoides polygyrus (= Nematospiroides dubius) in ASH/CSI mice in the Laboratory Animal House at Royal Holloway and Bedford New College during a recent autumn and spring period was associated with a syndrome of worm distortion, together with zero or low worm establishment and reduced fecundity (eggs/female worm). The eggs produced were non-viable and the egg capsule comprised a rumpled lipid and ruptured chitin layer. The egg size and peaks of egg production were also reduced and the total egg output ceased entirely by day 28 post-infection in male mice. The syndrome was repeated when control LACA mice harbouring 'normal' infections of H. polygyrus were housed on the same source of peat bedding material as the ASH/CSI mice. An increase in H. polygyrus egg production in ASH/CSI mice, removed from the peat or treated with 0.04% oxytetracycline hydrochloride suggested that the cause of the syndrome was microbial in origin. A microbiological assay of the peat, which was the common denominator of all syndrome infections, revealed an abundance of chitinase secreting species of bacteria (Bacillaceae). Bacterial chitinase was therefore likely to rupture the chitin layer of the egg capsule producing nonviable eggs and either abnormal or no larvae. Preliminary in vitro studies using chitinase from Streptomyces griseus indicated that the hatching success of eggs of H. polygyrus was reduced as the concentration of chitinase increased.

Animals↗