Biomedical subjects

A J McCarthy

Publications and source records attributed to A J McCarthy.

24 records · Page 2Linked to original sources

PubMed1991

Purification and Cooperative Activity of Enzymes Constituting the Xylan-Degrading System of Thermomonospora fusca.

The thermophilic actinomycete Thermomonospora fusca produced endoxylanase, alpha-arabinofuranosidase, beta-xylosidase, and acetyl esterase activities maximally during growth on xylan. Growth yields on glucose, xylose, or arabinose were comparable, but production of endoxylanase and beta-xylosidase was not induced on these substrates. The crude xylanase activity was thermostable and relatively resistant to end product inhibition by xylobiose and xylan hydrolysis products. Six proteins with xylanase activity were identified by zymogram analysis of isoelectric focusing gels, but only a 32-kDa protein exhibiting three isomeric forms could be purified by fast protein liquid chromatography. Endoglucanases were also identified in carboxymethylcellulose-grown cultures, and their distinction from endoxylanases was confirmed. alpha-Arabinofuranosidase activity was due to a single dimeric protein of 92 kDa, which was particularly resistant to end product inhibition by arabinose. Three bands of acetyl esterase activity were detected by zymogram analysis, and there was evidence that these mainly consisted of an intracellular 80-kDa protein secreted to yield active 40-kDa subunits in the culture supernatant. The acetyl esterases were found to be responsible for acetyl xylan esterase activity in T. fusca, in contrast to the distinction proposed in some other systems. The addition of purified betaxylosidase to endoxylanase increased the hydrolysis of xylan, probably by relieving end product inhibition. The enhanced saccharification of wheat straw caused by the addition of purified alpha-arabinofuranosidase to T. fusca endoxylanase suggested a truly synergistic relationship, in agreement with proposals that arabinose side groups on the xylan chain participate in cross-linking within the plant cell wall structure.

Journal Article↗

PubMed1990

Lignocarbohydrate solubilization from straw by actinomycetes.

Actinomycetes grown on wheat straw solubilized a lignocarbohydrate fraction which could be recovered by acid precipitation. Further characterization of this product (APPL) during growth of Streptomyces sp. strain EC1 revealed an increase in carboxylic acid and phenolic hydroxyl content, suggesting progressive modification. This was also observed in dioxane-extracted lignin fractions of degraded straw, and some similarity was further suggested by comparative infrared spectroscopy. However, the molecular weight profile of APPL was relatively constant during growth of Streptomyces sp. strain EC1 on straw, while analysis of the dioxane-extracted lignin fractions appeared to show fragmentation followed by repolymerization. Lignocarbohydrate solubilization could be monitored in all cultures by routine assay of APPL-associated protein, which accounted for up to 20% of the extracellular culture protein in some cases. Interestingly, this protein fraction was found to include active hydrolytic and oxidative enzymes involved in the degradation of lignocellulose, and specific enzyme activities were often increased in the acid-insoluble fractions of culture supernatants. This was particularly important for peroxidase and veratryl oxidase activities, which could be readily detected in the acid-precipitable lignocarbohydrate complex but were virtually undetectable in untreated culture supernatants.

Journal Article↗

PubMed1989

Improved medium for recovery and enumeration of the farmer's lung organism, Saccharomonospora viridis.

A new medium, which we propose to call R8, was developed for the isolation and enumeration of the thermophilic actinomycete, Saccharomonospora viridis. This organism has been implicated in a range of hypersensitivity pneumonitides, including farmer's lung, but is generally isolated in small numbers from contaminated environments. Recovery of S. viridis from moldy hay and mushroom compost on R8 medium was compared with recovery on conventional media. S. viridis was isolated from both substrates but in highest numbers and most consistently on the R8 medium. The selectivity of this medium was best observed when the sedimentation chamber method was used for hay samples. Here S. viridis accounted for up to 80% of the total number of actinomycetes recovered on R8 and could not be recovered on rifampin selective medium under the same conditions. R8 was also found to be an efficient recovery medium for a range of thermophilic actinomycetes from mushroom compost and for another allergenic species, Faenia rectivirgula, from moldy hay. Contamination of isolation plates by thermophilic bacilli was reduced on R8 compared with the activity on half-strength tryptone soy agar, supplemented with 0.2% casein hydrolysate, and this, together with specific improvements in S. viridis growth, accounts for the selective effect. It is possible that the occurrence of S. viridis and its role as a causative agent of hypersensitivity pnuemonitis have been underestimated by the use of suboptimal recovery protocols. It is hoped that use of R8 in conjunction with dilution plate techniques will generate information on the ecology of S. viridis and contribute to health risk assessment studies.

Actinomycetales↗

PubMed1989

Degradation of lignin-related compounds by actinomycetes.

Evidence for activity against the lignin fraction of straw was produced for a range of actinomycete strains. Decolorization of the polymeric dye Poly R and oxidation of veratryl alcohol, indicators of ligninolytic activity in white rot fungi, and utilization of fractionated Kraft lignin and low-molecular-weight methoxylated aromatic compounds were the criteria used. The relationships between these activities and the solubilization of native lignin are discussed.

Journal Article↗

PubMed1988

Quantitative assessment of factors affecting the recovery of indigenous and released thermophilic bacteria from compost.

Thermophilic actinomycetes and bacilli were recovered from mushroom compost by conventional dilution plating and sedimentation chamber-Andersen sampler methods. Excessive growth of thermophilic bacilli on dilution plates accounted for the poor recovery and limited diversity of actinomycete colonies, and this result was largely unaffected by the use of modified extraction procedures and diluents. Assessment of the actinomycete population was more successfully achieved by applying the sedimentation chamber method, by using selective media, or both. Background resistance of the compost microflora to selective agents (kanamycin, novobiocin, tetracycline, thiostrepton, and NaCl) was extremely varied, but both actinomycetes and bacilli were particularly sensitive to tetracycline. The selective isolation of Thermoactinomyces spp. and Thermomonospora chromogena by novobiocin and kanamycin, respectively, was shown to be reproducible, and the use of high concentrations of kanamycin resulted in the isolation of a novel group of unidentified thermophilic actinomycetes. Comparison of nonselective nutrient media demonstrated that the nutrient-rich protoplast regeneration medium R5 was surprisingly efficient for actinomycete recovery. This medium was found to be particularly appropriate for the recovery of Saccharomonospora viridis BD125, introduced as spores into both sterile and fresh samples of mushroom compost. This stable pigmented variant of the S. viridis strains indigenous to compost was released at concentrations of up to 10 spores g of compost in order to provide information for future experiments on the release and recovery of genetically manipulated strains. The detection limits for this strain were in the region of 10 g from sterilized compost but only 10 g from nonsterile compost. These figures correspond to mean recovery efficiencies of approximately 70% (sterilized compost) and 53% (fresh compost) of viable spores released. Further improvements in the detection and recovery of S. viridis strains released into compost should be achieved by the introduction of selectable markers developed from this information on the antibiotic resistance profile of the indigenous compost microflora.

Journal Article↗

PubMed1979

Taxonomic and serologic studies on Micropolyspora faeni and Micropolyspora strains from soil bearing the specific epithet rectivirgula.

The results of serological studies on six strains of Micropolyspora faeni from hay, sputum and plant debris, and five strains of Mip. rectivirgula from soil indicated no significant differences between the two species. Antisera raised in rabbits against purified antigens of the type strains were used to compare the 11 strains by immunoelectrophoresis. The detailed antigenic composition of the type strains was also determined by two-dimensional immunoelectrophoresis against specific rabbit antisera and pooled serum samples from patients suffering from farmer's lung. Cross-reacting antigens were identified by intermediate gel immunoelectrophoresis. The close similarity of the two species was confirmed by the results of 60 morphological physiological and biochemical tests applied to the 11 strains. We consider that the strains belong to a single species and propose that the specific epithet faeni be conserved for the taxon.

Antigens, Bacterial↗