Anjana Singh

Sebacinaceae: Culturable Mycorrhiza-Like Endosymbiotic Fungi and Their Interaction with Non-Transformed and Transformed Roots

The term mycorrhiza refers to the association between fungi and roots of higher plants. This association is usually considered a mutualistic symbiosis because of the highly beneficial relationships established between both partners, in which the host plants receive mineral nutrients via the fungal mycelium (mycotrophism), while the heterotrophic fungi obtain carbon compounds from the host plants (Harley and Smith 1983; Varma et al. 1999, 2004). Arbuscular mycorrhizal (AM) fungi belong to nine genera: Gigaspora, Scutellospora, Glomus, Acaulospora, Entrophospora, Archaeospora, Gerdemannia, Paraglomus and Geosiphon, the only known fungal endosymbiosis with cyanobacteria (see Chap. 15). The monoxenic cultivation of these micro-organisms in association with suitable root organ cultures has received increased interest in the last decades, and several fundamental research areas are now widely covered using this system.

Efficacy of arsenic filtration by Kanchan Arsenic Filter in Nepal

Groundwater arsenic contamination has caused a significant public health burden in lowland regions of Nepal. For arsenic mitigation purposes, the Kanchan Arsenic Filter (KAF) was developed and validated for use in 2003 after pilot studies showed its effectiveness in removing arsenic. However, its efficacy in field conditions operating for a long period has been scarcely observed. In this study, we observe the efficacy of KAFs running over 6 months in highly arsenic-affected households in Nawalparasi district. We assessed pair-wise arsenic concentrations of 62 randomly selected household tubewells before filtration and after filtration via KAFs. Of 62 tubewells, 41 had influent arsenic concentration exceeding the Nepal drinking water quality standard value (50 μg/L). Of the 41 tubewells having unsafe arsenic levels, KAFs reduced arsenic concentration to the safe level for only 22 tubewells, an efficacy of 54%. In conclusion, we did not find significantly high efficacy of KAFs in reducing unsafe influent arsenic level to the safe level under the in situ field conditions.

Enhanced Productivity Associated with Tripartite Symbiosis Between Phaseolus, Rhizobia, and Piriformospora indica: In Presence of Vermicompost

Phaseolus bean has potential to establish symbiosis with rhizobia and mycorrhizal fungi for its nitrogen nutrition and uptake of phosphorus from the soil, respectively. This benefit to the plant can be further enhanced by incorporating nutrient-rich vermicompost in the soil. The tripartite symbiosis of Phaseolus bean with rhizobia and Piriformospora indica in presence of vermicompost was assessed by plant growth, productivity, mycorrhizal colonization, and nitrogen, phosphorous, and potassium (NPK) content of plant. The length and weight of shoot and root were highest during harvesting stage in the rhizobia and P. indica-inoculated plant supplemented with vermicompost compared to single inoculation. Similarly, the NPK uptake and mycorrhizal colonization was highest in dual inoculation in presence of vermicompost. Incorporation of vermicompost is beneficial for the growth of the plant.

Mass Cultivation of Piriformospora indica and Sebacina Species

Symbiotic arbuscular mycorrhizal fungi Sebacinales can be easily mass multiplied on defined synthetic media. Piriformospora indica, the symbiotic fungi can be grown in a root of a living plant and under axenic culture. Scientists can take privilege of carrying out certain basic research to understand the molecular basis of plant–microbes interaction. Plant industries can produce Sebacinales under aseptic condition for commercial purposes and biological hardening of tissue-culture raised plants. Symbiotic fungi can be successfully cultivated on a wide range of synthetic solidified and broth media, e.g., MMN1/10, modified aspergillus, M4N, MMNC, MS, WPM, Malt–Yeast extract, PDA, and aspergillus. Among the tested the most optimum was aspergillus.

Evaluation of methods to detect in vitro biofilm formation by staphylococcal clinical isolates

ObjectiveStaphylococcus genus comprising both Staphylococcus aureus and coagulase negative staphylococci (CoNS) are widely distributed in nature and can infect diversity of hosts. Indeed, staphylococci are the major pathogens causing biofilm associated infections caused by contaminated hospital indwelling devices. These infections are persistent in nature being highly refractory to various stresses including antibiotics. Implementation of efficient diagnostic techniques for the biofilm production would help minimize the disease burden. Thus, early detection of pathogenic strains producing biofilms warrant the utmost importance in diagnostic laboratories especially in resource limited settings.ResultAmong 375 isolates collected from different clinical specimens, 214 (57%) were identified as coagulase negative staphylococci and 161 (43%) S. aureus. Detection of In-vitro biofilm formation in these isolates were carried out by three commonly used phenotypic assays and a genotypic assay. While evaluating the results, tissue-culture method with supplemented glucose and sucrose showed the best correlation with the results of genotypic assay.

Effect of Azotobacter chroococcum and Piriformospora indica on Oryza sativa in Presence of Vermicompost

The overall growth and development of various plants is benefited by the activity of rhizospheric microorganisms in soil. The beneficial activities of these organisms include biological nitrogen fixation, phosphate solubilization and mineralization etc. which is enhanced in presence of mycorrhiza. A pot culture trial was carried out to study the growth promotion of Oryza sativa with dual inoculation of Azotobacter chroococcum and Piriformospora indica an Arbuscular-Mycorrhiza-like-fungus in presence of vermicompost. The study parameters included to evaluate the dual effect were shoot length, root length, fresh and dry shoot weight, fresh and dry root weight, panicle numbers, plant tissue analysis (NPK content) and soil analysis in terms of pH, NPK and organic content on 45th and 90th day for vegetative and reproductive stage respectively. In both stages, a significant positive response was observed in all growth parameters when plant was dual inoculated with A. chroococcum and P. indica in presence of vermicompost than untreated control plants. The result shows that the combination of dual inoculation of A. chroococcum and P. indica with vermicompost was found to improve growth parameters and nutrient uptake in rice plant.

Stimulated Growth of Lycopersicum esculentum CLA 1131 in Presence of Piriformospora indica and Vermicompost

In the mutualistic association between plant and mycorrhiza, plant benefits by gaining an improved nutrient and water acquisition through fungal hyphae and/or an enhanced abiotic stress tolerance. Since mycorrhiza facilitates the plant in the nutrient uptake from the soil, fertility of soil is necessary for the availability of the essential nutrients. The axenically cultivable root-colonizing endophytic fungi Piriformospora indica treated tomato plant (Lycopersicum esculentum CLA 1131); when supplemented with vermicompost, the growth and biomass were enhanced. Mycorrhizal colonization was improved in the presence of vermicompost. The amount of essential nutrient nitrogen, phosphorous, and potassium content in plant was improved by the colonization with P. indica and influenced by the nutrient conditions in the soil. The efficiency of nutrient uptake by P. indica is complemented by vermicompost.

Antibiotic susceptibility and arsenic tolerance of urinary bacteria isolated from arsenic-exposed people in Nepal.

Community-based information on antibiotic susceptibility of urinary bacteria is useful in clinical practice, including empiric therapy. Owing to evidence of coselection of metal and antibiotic resistance, there is growing concern on testing of such selective pressure in clinical as well as environmental bacterial isolates. We examined arsenic tolerance and antibiotic resistance in urinary isolates and their possible coselection among arsenic-exposed subjects. Urinary arsenic levels were assessed by atomic absorption spectrophotometer. Antibiotic resistance and arsenic tolerance of urinary bacteria were observed by modified Kirby-Bauer and minimum inhibitory concentration methods, respectively. The percentage of one, two, and multidrug-resistant urinary isolates were 30.4%, 37%, and 30.4%, respectively. Isolates showed variable tolerance to arsenic species. Gram-negative isolates were more tolerant to arsenic species than Gram positive. Although statistically insignificant, arsenic tolerance tended to increase from total susceptible to two-drug resistance. However, multiple drug resistance was not induced by the urinary arsenic (p>0.05). We observed moderately positive correlation between urinary arsenic level to arsenic tolerance of isolates (p<0.05). Although tolerance significantly correlated to urinary arsenic level, coselection/coresistance of arsenic to the antibiotic resistance in urinary isolates is inconclusive and remains to be further elucidated.