Biomedical subjects

Naresh Magan

Publications and source records attributed to Naresh Magan.

22 records · Page 2Linked to original sources

PubMed2003

Differentiation of Agaricus species and other homobasidiomycetes based on volatile production patterns using an electronic nose system.

Comparisons of the qualitative volatile production patterns between seven species of Agaricus, and between two of Volvariella and Pleurotus and one Coprinus species when grown at 25 degrees C on agar media for 14 d were made. There was good reproducibility between the volatile production patterns of the same species using an electronic nose unit with a 14 conducting sensor polymer array. Principle Component Analysis (PCA) showed that it was possible to discriminate between five of the seven Agaricus species, but that some overlap occurred between the others. Cluster analysis showed that there was also overlap between some species with the tropical collection of A. bitorquis separating out from the others. The volatile production profile of the commercial A. bisporus was close to that of a wild species, A. campestris. A. bisporus could be readily differentiated from other non-Agaricus species. This study demonstrates the potential for using electronic nose systems to rapidly differentiate mycelial cultures of homobasidiomycete mushrooms.

Agaricus↗

PubMed2003

Water availability affects the growth, accumulation of compatible solutes and the viability of the biocontrol agent Epicoccum nigrum.

Growth of the biocontrol fungus Epicoccum nigrum was more sensitive to ionic solute water stress (NaCl) than non-ionic (glycerol) on potato dextrose-based media at -0.5, -3.0 and -5.5 MPa water potentials. Subsequent physiological manipulation of growth of E. nigrum in glycerol-modified media to -3.0 MPa water potential resulted in a significant increase in the accumulation of compatible solutes in both mycelial liquid cultures and spores, but no enhanced accumulation of the desiccation protectant trehalose, when compared to unmodified media (-0.5 MPa). The main solute accumulated was glycerol, followed by arabitol. In temporal studies over 20 days maximum accumulation of glycerol occurred in 5-d old cultures with water stressed cultures having 250x greater amounts than those from unmodified medium. The arabitol content was also higher in mycelium and spores produced under water stress. The difference was maximum after 15 days growth. Glucose content decreased over time in mycelial colonies but increased in spores. The germination of conidia from the two treatments was similar, regardless of compatible solute content, even at -9.25 MPa water potential stress. However, germ tube extension was significantly increased at this water potential level. The production of E. nigrum spores at -3.0 MPa water potential resulted in improved survival when stored fresh at 4 and 25 degrees C. However, freeze-drying severely affected the viability of spores produced on both media (-0.5 or 3.0 MPa). Accumulation of compatible solutes may assist the fungus in better ecological competence and establishment in the phyllosphere, where water availability is often limited.

Ascomycota↗

PubMed2002

Use of an electronic nose system for diagnoses of urinary tract infections.

The use of volatile production patterns produced by bacterial contaminants in urine samples were examined using electronic nose technology. In two experiments 25 and 45 samples from patients were analysed for specific bacterial contaminants using agar culture techniques and the major UTI bacterial species identified. These samples were also analysed by incubation in a volatile generation test tube system for 4-5 h. The volatile production patterns were then analysed using an electronic nose system with 14 conducting polymer sensors. In the first experiment analysis of the data using a neural network (NN) enabled identification of all but one of the samples correctly when compared to the culture information. Four groups could be distinguished, i.e. normal urine, Escherichia coli infected, Proteus spp. and Staphylococcus spp. In the second experiment it was again possible to use NN systems to examine the volatile production patterns and identify 18 of 19 unknown UTI cases. Only one normal patient sample was mis-identified as an E. coli infected sample. Discriminant function analysis also differentiated between normal urine samples, that infected with E. coli and with Staphylococcus spp. This study has shown the potential for early detection of microbial contaminants in urine samples using electronic nose technology for the first time. These findings will have implications for the development of rapid systems for use in clinical practice.

Biosensing Techniques↗

PubMed1995

Manipulation of intracellular glycerol and erythritol enhances germination of conidia at low water availability.

The insect pathogens Beauveria bassiana, Metarhizium anisopliae and Paecilomyces farinosus can be effective biocontrol agents when relative humidity (RH) is close to 100%. At reduced water availability, germination of propagules, and therefore host infection, cannot occur. Cultures of B. bassiana, M. anisopliae and P. farinosus were grown under different conditions to obtain conidia with a modified polyol and trehalose content. Conidia with higher intracellular concentrations of glycerol and erythritol germinated both more quickly and at lower water activity (aw) than those from other treatments. In contrast, conidia containing up to 235.7 mg trehalose g-1 germinated significantly (P < 0.05) more slowly than those with an equivalent polyol content but less trehalose, regardless of water availability. Conidia from control treatments did not germinate below 0.951-0.935 aw (identical to 95.1-93.5% RH). In contrast, conidia containing up to 164.6 mg glycerol plus erythritol g-1 germinated down to 0.887 aw (identical to 88.7% RH). These conidia germinated below the water availability at which mycelial growth ceases (0.930-0.920 aw). Germ tube extension rates reflected the percentage germination of conidia, so the most rapid germ tube growth occurred after treatments which produced conidia containing the most glycerol and erythritol. This study shows for the first time that manipulating polyol content can extend the range of water availability over which fungal propagules can germinate. Physiological manipulation of conidia may improve biological control of insect pests in the field.

Culture Media↗