Interaction of Endosulfan and malathion with blue-green algae Anabaena and Aulosira fertilissima

Profenofos induced modulation in physiological indices, genomic template stability and protein banding patterns of Anabaena sp. PCC 7120

To understand the mechanism underlying organophosphate pesticide toxicity, cyanobacterium Anabaena PCC 7120 was subjected to varied concentrations (0, 5, 10, 20 and 30 mg L(-1)) of profenofos and the effects were investigated in terms of changes in cellular physiology, genomic template stability and protein expression pattern. The supplementation of profenofos reduced the growth, total pigment content and photosynthetic efficiency of the test organism in a dose dependent manner with maximum toxic effect at 30 mg L(-1). The high fluorescence intensity of 2', 7' -dichlorofluorescin diacetate and increased production of malondialdehyde confirmed the prevalence of acute oxidative stress condition inside the cells of the cyanobacterium. Rapid amplified polymorphic DNA (RAPD) fingerprinting and SDS-PAGE analyses showed a significant alteration in the banding patterns of DNA and proteins respectively. A marked increase in superoxide dismutase, catalase, peroxidase activity and a concomitant reduction in glutathione content indicated their possible role in supporting the growth of Anabaena 7120 up to 20 mg L(-1). These findings suggest that the uncontrolled use of profenofos in the agricultural fields may not only lead to the destruction of the cyanobacterial population, but it would also disturb the nutrient dynamics and energy flow.

Exogenous osmolytes suppresses the toxic effects of malathion on Anabaena variabilis

Role of osmolytes is though well established for salt, drought and chilling stress, but their role in pesticide stress is yet to be explored thoroughly. The sporadic information covers our previous studies on proline with respect to endosulfan and carbaryl pesticides in cyanobacteria. Therefore, during the present investigation importance of osmolytes (exogenous and endogenous) is studied in cyanobacterial biofertilizer Anabaena variabilis in the presence of 25, 50, 75 and 100 μg mL(-1) malathion pesticide. Present investigation has two parts. In the first part we showed that malathion exert its toxic effect on growth (biomass) via. malondialdehyde (MDA) and hydrogen peroxide (H2O2). This was associated with quantitative enhancement of endogenous osmolytes (proline, sucrose, mannitol, trehalose and glycogen). In the second part effort was made to corelate effect of exogenous addition of osmolytes (which were detected in the first part of this study) on growth and antioxidant enzymes [like superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] of A. variabilis in the presence of 100 μg mL(-1) malathion. Surprisingly it was observed that exogenous osmolytes gave additional protection to the organism. The order of protection provided by osmolytes was as trehalose>glycogen>sucrose>mannitol>proline in A. variabilis.

The organophosphate insecticide Coumaphos induces oxidative stress and increases antioxidant and detoxification defences in the green macroalgae Ulva pertusa

It is well established that many pesticides used in the farming and horticultural industries are harmful to not only the target species they were developed for, but also other organisms. Organophosphates were introduced as a replacement for the organochlorines and are generally considered non-toxic to plants and algae. This study investigated the impact of Coumaphos, a commonly used organophosphate, on the estuarine macrophyte Ulva pertusa. In a seven-day experiment U. pertusa cultures were exposed to four environmentally relevant concentrations of Coumaphos (0.01 mg/L, 0.05 mg/L, 0.1mg/L, 0.5 mg/L), well below the aqueous solubility maximum of the insecticide. The impact of Coumaphos was determined at a cellular level by assessing oxidative damage in the form of protein carbonyl and lipid hydroperoxide levels. Furthermore, non-enzymatic antioxidant levels and changes in the levels of enzymatic antioxidants and the enzyme GST were measured. Concentrations of Coumaphos above 0.01 mg/L caused rapid increases in the levels of protein carbonyls and lipid hydroperoxides peaking after 2-3 days of exposure, followed by a rapid decline in both markers of oxidative stress. Glutathione levels and the activities SOD, CAT, GR, APOX and GST all increased in response to the higher concentrations of Coumaphos tested and remained elevated for the duration of the experiment. These results demonstrate that environmentally relevant levels of the insecticide Coumaphos can cause oxidative damage and increase the antioxidant scavenging capacity, and GST activity in U. pertusa. This could potentially alter resource allocation within this alga, impacting algal growth and development, with possible indirect ecological consequences.

Compatibility of ascorbate-glutathione cycle enzymes in cyanobacteria against low and high UV-B exposures, simultaneously exposed to low and high doses of chlorpyrifos

This study deals with the comparative responses of the two cyanobacteria viz. Nostoc muscorum and Phormidium foveolarum against single and combined doses of low (UV-B(L,) 0.1 μmol m(-2) s(-1)) and high (UV-B(H), 1.0 μmol m(-2) s(-1)) fluence rates of ultraviolet-B radiation with low (CP(L), 1 μg ml(-1)) and high (CP(H), 2 μg ml(-1)) doses of the insecticide chlorpyrifos by measuring changes in growth, ascorbate-glutathione cycle enzymes and related metabolites. CP(L) and UV-B(L) both caused lesser increase in ROS but significantly stimulated AsA-GSH cycle enzymes. On the other hand, CP(H) and UV-B(H) posed inhibitory effects by enhancing ROS and inhibiting AsA-GSH cycle enzymes. Inhibitions in CP(H) or UV-B(H) treated samples were significantly prevented when they were supplemented with UV-B(L) and CP(L) (after 72 h), respectively by lowering down ROS and enhancing AsA-GSH enzymes and related metabolites which manifested in terms of improved biomass accumulation.

Comparative toxicity of the pesticides carbofuran and malathion to the freshwater flagellate Euglena gracilis

Pesticides are toxic chemicals used for agricultural as well as non-agricultural purposes. The toxicity of pesticides does not remain limited to the site of application but they also cause toxicity to non-target organisms in terrestrial as well as in aquatic environments. This study discusses the comparative toxicity of a carbamate (carbofuran) and an organophosphorus (malathion) pesticide to the freshwater flagellate Euglena gracilis during short- and long-term exposures. To evaluate the toxicity of the pesticides, different parameters of the flagellate, like cell density, motility, swimming velocity, cell shape, gravitactic orientation, photosynthetic efficiency, and concentration of light harvesting pigments, were used as end points. Carbofuran was found to be more toxic to E. gracilis than malathion and adversely affected almost all the tested parameters in short- and long-term experiments. The only significant adverse effect by malathion could be demonstrated on the swimming velocity of cells in short-term experiments. The adverse effects of the pesticides were more pronounced during short-term than during long-term exposure.

Influence of endosulfan on microbial biomass and soil enzymatic activities of a tropical alfisol

The effect of endosulfan at normal residue level (1 and 10 ppm) and elevated level (100 ppm) on microbial biomass and enzymatic activities of a tropical alfisol was studied. Dehydrogenase, Fluorescein diacetate hydrolase, acid phosphatase, aryl sulphatase activities and microbial biomass of the soil increased by 2.4, 1.7, 1.4, 1.8 and 3.7 times, respectively by the 14th day of incubation with 1 ppm endosulfan, indicating the possible involvement of soil microorganisms and their enzymes in degradation of endosulfan. Soil nitrogenase activity decreased by 8.0 times by the 14th day of application of 1 ppm endosulfan, suggesting that endosulfan or its metabolites may pose toxicological threat to nitrogen fixers in soil.

Effect of lindane on the growth and metabolic activities of cyanobacteria

The effect of lindane was studied in Cyanobacteria (Anabaena) by estimating its growth pattern, biomass yield, chlorophyll content, and total starch and protein content. The results reveal that exposure of Anabaena with 0.5, 1.0, 1.5, and 2.0 ppm levels of lindane will have drastic effects on biomass production and photosynthetic rate. Since Cyanobacteria are a primary source of aquatic food web and important biofertilizer for rice cultivation, their protection from residual effects of lindane is essential for enriched soil fertility.

Toxicity of pesticides to aquatic microorganisms: a review

Microorganisms contribute significantly to primary production, nutrient cycling, and decomposition in estuarine eco-systems; therefore, detrimental effects of pesticides on microbial species may have subsequent impacts on higher trophic levels. Pesticides may affect estuarine microorganisms via spills, runoff, and drift. Both the structure and the function of microbial communities may be impaired by pesticide toxicity. Pesticides may also be metabolized or bioaccumulated by microorganisms. Mechanisms of toxicity vary, depending on the type of pesticide and the microbial species exposed. Herbicides are generally most toxic to phototrophic microorganisms, exhibiting toxicity by disrupting photosynthesis. Atrazine is the most widely used and most extensively studied herbicide. Toxic effects of organophosphate and organochlorine insecticides on microbial species have also been demonstrated, although their mechanisms of toxicity in such nontarget species remain unclear. There is a great deal of variability in the toxicity of even a single pesticide among microbial species. When attempting to predict the toxicity of pesticides in estuarine ecosystems, effects of pesticide mixtures and interactions with nutrients should be considered. The toxicity of pesticides to aquatic microorganisms, especially bacteria and protozoa, is an area of research requiring further study.

Modulation of cadmium uptake and toxicity in Spirodela polyrrhiza (L.) schleiden due to malathion

Fronds of Spirodela polyrrhiza were treated with different concentrations of Cd and malathion singly and in combinations. Results showed that Cd toxicity was more than malathion. The chlorophyll content was more severely affected by Cd (EC-50 of >1.0 µg ml(-1)); however, its toxicity was ameliorated in the presence of malathion (EC-50 of 2.0 µg ml(-1)). Although biomass and frond numbers were least affected by these toxicants, at initial treatment durations fronds multiplication was more severely affected than biomass with an increase in treatment durations. The importance of these findings have been discussed in relation to metal abatement and biomonitoring.

Role of calcium in the inhibition of nitrogenase activity by Methylparathion and Benthiocarb in the cyanobacterium Nostoc muscorum

Methylparathion and Benthiocarb inhibition of N2 fixation in the cyanobacterium Nostoc muscorum was reversed by Ca(2+) at 1 mM but not at 0.1 mM. The concentration of intracellular Ca(2+) was relatively high in the presence of these pesticides when 1 mM Ca(2+) was also present, indicating that intracellular Ca(2+) may participate in protecting nitrogenase activity against Methylparathion and Benthiocarb.

Effects of two herbicidal wastewaters on Chlorella sp. and Phaeodactylum tricornutum

The effects on Chlorella sp. and Phaeodactylum tricornutum of two industrial wastewaters known to contain the herbicide residues of Trifluralin and Propanil have been determined by monitoring the number of cells, the chlorophyll fluorescence and the carbon dioxide assimilation simultaneously for a period of 14 days. The growth of the diatom, Phaeodactylum tricornutum, was inhibited by concentrations of herbicidal waste of the order of 0.1-0.5%, apparently because the rate of reproduction was reduced. Chlorella sp. cells, on the other hand, whilst dramatically inhibited by 1% concentrations of herbicidal waste, were able to recover over a period of 14 days. If discharged at concentrations below 0.01%, the industrial wastes appeared not to affect phytoplankton.