Showing papers by "Iqbal Ahmad published in 2005"

Indole Acetic Acid Production by the Indigenous Isolates of Azotobacter and Fluorescent Pseudomonas in the Presence and Absence of Tryptophan

Abstract: A total of 21 bacterial isolates (Azotobacter sp., 10 and fluorescent Pseudomonas sp., 11) were isolated from different rhizospheric soils in the vicinity of Aligarh city and characterized as per standard methods. These isolates were further tested for the production of indole acetic acid (IAA) in a medium with 0, 1, 2 and 5 mg/ml of tryptophan. A low amount (2.68-10.80 mg/ml) of IAA production was recorded by Azotobacter strains without tryptophan addition. Seven Azotobacter isolates showed high level (7.3 to 32.8 mg/ml) production of IAA at 5 mg/ml of tryptophan while at 1 and 2 mg/ml the production was in the range of 1.47 to 11.88 and 5.99 to 24.8 mg/ml, respectively. Production of IAA in fluorescent Pseudomonas isolates increased with an increase in tryptophan concentration from 1 to 5 mg/ml in the majority of isolates. In the presence of 5mg/ ml of tryptophan, 5 isolates of Pseudomonas produced high levels (41.0 to 53.2 mg/ml) of IAA while 6 other isolates produced IAA in the range of 23.4 to 36.2 mg/ml. Production of IAA was further confirmed by extraction of crude IAA from 3 isolates of Azotobacter (Azs1, Azs6 and Azs9 ) and three isolates of Pseudomonas (Ps1, Ps4 and Ps7) and subsequent TLC analysis. A specific spot from the extracted IAA preparation was found corresponding with the standard spot of IAA with same Rf value. Pseudomonas isolates (Ps1, Ps4 and Ps7) showed inhibitory effects on the growth of root elongation of Sesbania aculeata and Vigna radiata at all concentrations of tryptophan compared to the control. However, the isolates of Azotobacter (Azs1, Azs6 and Azs9) demonstrated stimulatory effects on both plants. Increasing the concentration of tryptophan from 1 mg/ml to 5 mg/ml resulted in decreased growth in both S. aculeata and V. radiata. On a comparative basis isolate Azs9 was most promising in promoting plant growth. On the other hand, high concentration of exogenous tryptophan could exhibit toxic effects on plant growth.

Effect of certain bioactive plant extracts on clinical isolates of β-lactamase producing methicillin resistant Staphylococcus aureus

Abstract: Ethanolic extracts and some fractions from 10 Indian medicinal plants, known for antibacterial activity, were investigated for their ability to inhibit clinical isolates of beta-lactamase producing methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA). Synergistic interaction of plant extracts with certain antibiotics was also evaluated. The MRSA test strains were found to be multi-drug resistant and also exhibited high level of resistance to common beta-lactam antibiotics. These strains produced beta-lactamases, which hydrolyze one or other beta-lactam antibiotics, tested. The extract of the plants from Camellia sinensis (leaves), Delonix regia (flowers), Holarrhena antidysenterica (bark), Lawsonia inermis (leaves), Punica granatum (rind), Terminalia chebula (fruits) and Terminalia belerica (fruits) showed a broad-spectrum of antibacterial activity with an inhibition zone size of 11 mm to 27 mm, against all the test bacteria. The extracts from the leaves of Ocimum sanctum showed better activity against the three MRSA strains. On the other hand, extracts from Allium sativum (bulb) and Citrus sinensis (rind) exhibited little or no activity, against MRSA strains. The antibacterial potency of crude extracts was determined in terms of minimum inhibitory concentration (MIC) by the tube dilution method. MIC values, of the plant extracts, ranged from 1.3 to 8.2 mg/ml, against the test bacteria. Further, the extracts from Punica granatum and Delonix regia were fractionated in benzene, acetone and methanol. Antibacterial activity was observed in acetone as well as in the methanol fractions. In vitro synergistic interaction of crude extracts from Camellia sinensis, Lawsonia inermis, Punica granatum, Terminalia chebula and Terminalia belerica was detected with tetracycline. Moreover, the extract from Camellia sinensis also showed synergism with ampicillin.TLC of the above extracts revealed the presence of major phytocompounds, like alkaloids, glycosides, flavonoids, phenols and saponins. TLC-bioautography indicated phenols and flavonoids as major active compounds.

Heavy Metal Biosorption potential of Aspergillus and Rhizopus sp. isolated from Wastewater treated soil

Abstract: Two isolates belonging to the predominant genera Aspergillus and Rhizopus isolated from agricultural field treated with sewage/ industrial effluents were selected for the biosorption potential evaluation of Cr and Cd. Pretreated, dead biomass of above fungi was used for bioadsorption experiment at pH value 4.5 with the biomass, 1-5 mg in a 100 ml metal solution of different concentration (2, 4, 6 and 8 mM) with a contact time of 18 hrs and agitation, 120 rpm. Bioadsorption of Cr ranged from 6.20-9.5 mg/g of dry mass at one or other initial metal concentrations by Aspergillus and Rhizopus sp. The bioadsorption of Cd was ranged from 2.3-8.21mg/g. On the comparative basis Rhizopus sp. could bioadsorbed higher concentration of both metals as compared to Aspergillus sp. Bioadsorption of Cd and Cr was influenced by initial metal concentration and nature of organism. The findings revealed that fungi of metal polluted sites showed higher metal tolerance and bioadsorption capacity of chromium and cadmium. Journal of Applied Sciences and Environmental Management Vol. 9(1) 2005: 123-126

Evaluation of fluorescent Pseudomonads and Bacillus isolates for the biocontrol of a wilt disease complex of pigeonpea

Abstract: Twenty isolates of fluorescent pseudomonads and Bacillus spp. were obtained from pathogen suppressive soil of a pigeonpea (Cajanus cajan) field showing wilt disease complex. These isolates were evaluated in the laboratory and screen-house for the biocontrol of wilt disease complex. Six isolates were considered to have potential for the biocontrol of the disease on the basis of antibiotic sensitivity, antifungal activity, fluorescence produced by Pseudomonas, inhibitory effect on the hatching and penetration of nematodes and colonization of pigeonpea roots by these isolates. These isolates will be further tested for their biocontrol of wilt disease complex of pigeonpea under field conditions.

Effect of heavy metal on survival of certain groups of indigenous soil microbial population

Abstract: Heavy metal pollution of soil is known to adversely effect microbial activities at elevated concentration. However, response of indigenous soil bacterial population to added heavy metal and metal combinations is poorly understood. In the present study salts of heavy metals like Cu, Cd, Cr, Hg, Mn, Ni, Pb and Zn were added in soil under laboratory conditions with different concentrations (50, 100, 150 and 200 μg/g of soil) and sufficient moisture. The microcosm were stored at 28 ± 1 °C for 28 days. Viable count of aerobic heterotrophs, asymbiotic nitrogen fixers and actinomycetes were determined at different time intervals (0, 7, 14, 21 and 28 days of incubation) using the plate dilution method. Aerobic-heterotrophic bacterial population were more sensitive to metal groups like Ni and Cd followed by Cu, Cd, Hg, Mn, Cr and Zn. Similarly a symbiotic nitrogen fixers showed higher sensitivity to metal groups like Cd, Pb, Hg followed by Cu, Cr, Mn, Ni and Zn. Actinomycetes were found most sensitive. Metal toxicity was higher for Pb, Mn, Ni followed by Cd, Hg, Cr and least to Cu and Zn. Toxicity of heavy metal was concentration as well as time dependent. Loss of microbial diversity is evident as we move towards higher concentration of heavy metal in soil. Further, experimentation is needed to understand the genetic diversity of the sensitive and metal tolerant microbial population and metal-microbe interaction under natural condition in soil. Journal of Applied Sciences and Environmental Management Vol. 9(1) 2005: 115-121

Heavy metal contamination of soil: problems and remedies.

Abstract: Practical Issues of Land Application of Biosolids: PK Wong Bioavailability of Metals and Metalloids in Terrestrial Environments: Patrick K Jjemba Microbially Mediated Changes in the Mobility of Contaminant Metals in Soils and Sediments: Flynn Picardal and D Craig Cooper Influence of Long-Term Application of Treated Oil Refinery Effluent on Soil Health: Iqbal Ahmad et al Heavy Metals in Temperate Forest Soils: Speciation, Mobility and Risk Assessment: G Koptsik et al Bioremediation: Andrew S Ball Effects of Fly Ash on Soil Characteristics, Plant Growth and Soil Microbial Populations: ZA Siddiqui and LP Singh Effect of Metal-Contaminated Organic Wastes on Microbial Biomass and Activities: A Review: K Chakrabarti et al Characterization and Evaluation of Municipal Solid Waste Compost by Microbiological and Biochemical Parameters in Soil under Laboratory and Field Conditions: P Bhattacharyya et al Phytoextraction of Lead-Contaminated Soils: Current Experience: John Pichtel