Mohd Ikram Ansari

Conjugative plasmids in multi-resistant bacterial isolates from Indian soil

Aims:  Determination of heavy metal and antibiotic resistance and presence of conjugative plasmids in bacteria isolated from soil irrigated with wastewater.

Genotoxicity of wastewaters used for irrigation of food crops.

In most towns of India, wastewater coming from both industrial and domestic sources and without any treatment is used to irrigate the agricultural crops. This practice has been polluting the soil, and pollutants could possibly reach the food chain. For the above reasons, the wastewaters of Ghaziabad City (India), which is used for irrigation, were sampled (at two different sites) and monitored for the presence of genotoxic agents from January 2005 to June 2007. Gas chromatographic analysis showed the presence of certain OC (DDE, DDT, Dieldrin, Aldrin, and Endosulfan) and OP (Dimethoate, Malathion, Methlyparathion, and Chlorpyrifos) pesticides in both the sampling sites. Wastewater samples were concentrated using XAD resins (XAD‐4 and XAD‐8) and liquid–liquid extraction procedures, and the extracts were assayed for genotoxic potential by Ames Salmonella/microsome test, DNA repair defective mutants, and bacteriophage λ systems. The test samples exhibited significant mutagenicity with TA98, TA97a, and TA100 strains with the probable role of contaminating pesticides in the wastewater. However, XAD‐concentrated samples were more mutagenic in both sites as compared to liquid–liquid‐extracted samples. The damage in the DNA repair defective mutants in the presence of XAD‐concentrated water samples were also found to be higher to that of liquid–liquid‐extracted water samples at the dose level of 20 μL/mL culture. All the mutants invariably exhibited significant decline in their colony‐forming units as compared to their isogenic wild‐type counterparts. The survival was decreased by 81.7 and 75.5% in polA− strain in site I, and 76.0 and 73.5% in site II in polA− under the same experimental conditions after 6 h of treatment with XAD‐concentrated and liquid–liquid‐extracted samples, respectively. A significant decrease in the survival of bacteriophage λ was also observed when treated with the test samples.

Genotoxicity of agricultural soils in the vicinity of industrial area.

Soil samples from agricultural fields (cultivated) in the vicinity of industrial area of Ghaziabad City (India) were collected. In this city, wastewater coming from both industrial and domestic sources and without any treatment is used to irrigate the food crops. This practice has been polluting the soil and pollutants might reach the food chain. Gas chromatographic analysis show the presence of certain organochlorine (DDE, DDT, dieldrin, aldrin and endosulfan) and organophosphorus (dimethoate, malathion, methylparathion and chlorpyrifos) pesticides in soil samples. Samples were extracted using different solvents, i.e. methanol, chloroform, acetonitrile, hexane and acetone (all were HPLC-grade, SRL, India), and the extracts were assayed for genotoxic potential using Ames Salmonella/microsome test, DNA repair defective mutants and bacteriophage lambda systems. TA98 and TA100 were found to be the most sensitive strains to all the soil extracts tested. Methanol extracts exhibited a maximum mutagenicity with TA98 strain {540 (-S9) and 638 (+S9) revertants/g of soil} and 938 (-S9) and 1008 (+S9) revertants/g of soil with TA100 strain. The damage in the DNA repair defective mutants was found maximum with methanolic extract followed by acetonitrile, chloroform, hexane and acetone at the dose level of 40 microl/ml culture after 6h of treatment. The survival was 25, 30, 32, 33 and 35% in polA strain after 6h of treatment when tested with wastewater irrigated soil extracts of methanol, acetonitrile, chloroform, hexane and acetone, respectively. A significant decrease in the plaque forming units of bacteriophage lambda was also observed when treated with 40 microl of test samples. Present results showed that methanolic extracts of soil were more toxic than other soil extracts. The soil is accumulating a large number of pollutants due to wastewater irrigation and this practice of accumulation has an impact on soil health.

Biofilm Formation by Environmental Bacteria

The majority of bacteria in the environment live associated with surfaces, in so called biofilms. Bacterial cells embedded in a biofilm can better withstand environmental stress, such as nutrient deprivation, unphysiological temperatures and pH changes. Within the biofilm they become more resistant to detachment, oxygen radicals, disinfectants, and antibiotics than the individual planktonic cells. In this chapter, the current status of biofilm research is summarized, with focus on the mechanims involved in formation of biofilms, characteristics of bacteria living in biofilms, e.g. the production of extracelluar polymeric substances (EPS) and the intercellular communication via quorum sensing. Detrimental and beneficial effects of microbial biofilms are described, as well as their application in modern biotechnology. An overview about state of the art techniques to analyse complex biofilms is given, as well as a summary on existing and emerging biofilm inhibitors. We developed a continuous upflow biofilm reactor system where mixed species environmental biofilms can form attached to glass beads. Studies on these biofilms by lectin-binding analysis and fluorescence microscopy are described. Experimental systems developed to visualize biofilms by fluorescent labels using confocal laser scanning microscopy (CLSM) and the current strategies in removing or controlling the biofilm are dicussed. The chapter ends with perspectives on the development of new emerging biofilm inhibitors and with an outlook on new promising techniques that will enable analysis of the composition as well as the structure of biofilms in even more detail.

Environmental Protection Strategies: An Overview

Environment protection and sustainability are harmonious and sustainability can be achieved by protecting our natural resources. This chapter presents an overview of the different types of problems affecting the environment and recent advances in environmental protection strategies. The role and potential of rhizospheric microorganisms in plant growth in disturbed soils is presented. Agro-industrial wastes and municipal solid wastes management options are discussed; the various sustainable solutions are also highlighted. The health effects of dyes and their different remedial treatment process and also the potential of peroxidases for treatment of dyes are discussed. The resistance and transfer genes in microorganisms and their molecular detection methods are explained along with the ability of environmental bacteria to form biofilms. The biochemical attributes for the assessment of soil ecosystem sustainability and the various methods involved in genotoxicity testing of environmental pollutants are summarized. Pesticides bioremediation strategies from soil and wastewater and the biodegradation of cyanobacteria and their toxins are outlined. The cause of Alfalfa damping off and the characterization of the causal agent are discussed. The significance of biochemical compounds derived from legumes and rhizobacteria (rhizodeposits) with potential in biotechnology are explained. The pulp and paper industry is a big sector and generates large amounts of wastewater; the treatment processes are briefly presented. The contamination of shooting range soils with heavy metals is a matter of concern and the remediation processes are discussed. The chapter ends with the role of biopesticides in sustainable agriculture. Thus, whole work concluded the ill effects of different types of pollution and the waste generated by human activities in the environment. Current trends involved in the remediation and the technologies used for this purpose are presented in detail.

Metal Tolerance and Biosorption Potential of Soil Fungi: Applications for a Green and Clean Water Treatment Technology

Heavy metals pose a significant ecological and public health hazard because of their toxic effects and their ability to accumulate in terrestrial and aquatic food chains. This chapter addresses the interactions of heavy metals with organisms for application in wastewater or soil treatment systems, with special emphasis on yeasts and fungi. Conventional techniques to remove metals from wastewaters have several disadvantages; however, biosorption has demonstrated significant metal removal performance from large volumes of effluents. One key step of treatment processes for cleanup of heavy metal-enriched water or soil involves growing resistant cells that accumulate metals to optimize removal through a combination of biosorption and continuous metabolic uptake. Fungal biosorption can be used for the removal of metals from contaminated water and soil; fungal biosorbents are less expensive and more effective alternatives for the removal of metallic elements, especially heavy metals, from aqueous solution. In this chapter, the biosorption abilities of fungal biomass toward metal ions are emphasized. The chapter also highlights the mechanisms involved in fungal biosorption and the factors affecting the biosorption process. The current status and achievements of fungal biosorption technologies are reviewed.