Biodegradation of phorate by bacterial strains in the presence of humic acid and metal ions.

Phorate is a systemic insecticide used to eradicate mites, insects, and nematodes. Extensive use of this organophosphate has engendered severe environmental concerns. The current research aimed to explore the kinetic pathways of phorate biodegradation in aqueous solutions. Two novel bacterial strains Pseudomonas aeruginosa strain PR1 (KP268772.1) and Pseudomonas sp. PR_02 (KP268773.1) were isolated, screened, and developed given their potential to degrade phorate. Mineralization of phorate was assayed with and without the addition of metal ions [Fe (II) and Cu (II)] and humic acid (HA). In 14 days, experiment both strains have consumed about 69%-94.5% (half-life from 3.58 to 6.02 days) of phorate. The observed biodegradation rate of phorate with Cu (II) in the system was 73% and 87%, with a half-life of 4.86 and 4.07 days for PR1 and PR2, respectively. The biodegradation of phorate using Fe(II) was 69% and 82%, with half-life periods 5.68 and 4.49 days. Meanwhile, incorporating HA, the phorate biodegradation was inhibited significantly, showing 71% and 85% degradation, with half-life periods of 6.02 and 5.02 days. The results indicated that both bacterial strains were able to mineralize phorate with PR2 > PR1. Summarizing, the inhibition in phorate biodegradation order under different conditions was as HA > Fe (II) > Cu (II). UV-visible measurements and gas chromatography-mass spectrometric assays indicated that the possible degradation pathway of phorate included ethoxy-phosphonothio-methanethiol S-mercaptomethyl-O,O-dihydrogen phosphorodithioate, diethyl-methylphosphonate, methane dithiol, ethanethiol, and phosphate, as the main metabolites identified. Therefore, it was concluded that the newly isolated Pseudomonas strains could be a potential candidates for biodegradation of phorate in a cost-effective, safe, and environmentally friendly alternative.

Phorate induced oxidative stress, DNA damage and differential expression of p53, apaf-1 and cat genes in fish, Channa punctatus (Bloch, 1793).

The present study was conducted to assess the in-vivo activities of certain molecular biomarkers under the impact of phorate exposure. Fish, Channa punctatus (35 ± 3.0 g; 14.5 ± 1.0 cm; Actinopterygii) were subjected to semi-static conditions having 5% (0.0375 mg/L for T1 group) and 10% of 96 h-LC50 (0.075 mg/L for T2 group) of phorate exposure for 15 and 30 d. The oxidative stress was assessed in terms of superoxide dismutase (SOD) and catalase (CAT) activities. DNA damage was measured as induction of micronuclei (MN) and consequent differential expression of apoptotic genes-tumor suppressor (p53), apoptotic peptidase activating factor-1 (apaf-1) and catalase (cat) in liver and kidney, two major sites of biotransformation in fish, were quantified. Our findings reveal significant (p < 0.001) augmentations in SOD and CAT activities of liver and kidney tissues. MN frequency in erythrocytes of fish also increases significantly (p < 0.05) in a dose- and time-dependent manner. The mRNA level of p53 increased significantly (p < 0.05) in liver at 10% of 96 h-LC50 of phorate exposure after 30 d suggesting generation of stress due to accumulation of reactive oxygen species (ROS). Eventually, these findings decipher the dual role of ROS in generating genotoxicity as is evident by micronuclei induction and differential regulation of p53, apaf-1 and cat genes during the phorate induced DNA damage and apoptosis in test fish. The experimental inferences drawn on the basis of activities of aforesaid biomarkers shall be helpful in elucidating the possible causes of apoptosis under stressful conditions. Further, this study finds ample application in biomonitoring of phorate polluted aquatic ecosystem.

Phorate can reverse P450 metabolism-based herbicide resistance in Lolium rigidum.

BACKGROUND: Organophosphate insecticides can inhibit specific cytochrome P450 enzymes involved in metabolic herbicide resistance mechanisms, leading to synergistic interactions between the insecticide and the herbicide. In this study we report synergistic versus antagonistic interactions between the organophosphate insecticide phorate and five different herbicides observed in a population of multiple herbicide-resistant Lolium rigidum. RESULTS: Phorate synergised with three different herbicide modes of action, enhancing the activity of the ALS inhibitor chlorsulfuron (60% LD50 reduction), the VLCFAE inhibitor pyroxasulfone (45% LD50 reduction) and the mitosis inhibitor trifluralin (70% LD50 reduction). Conversely, phorate antagonised the two thiocarbamate herbicides prosulfocarb and triallate with a 12-fold LD50 increase. CONCLUSION: We report the selective reversal of P450-mediated metabolic multiple resistance to chlorsulfuron and trifluralin in the grass weed L. rigidum by synergistic interaction with the insecticide phorate, and discuss the putative mechanistic basis. This research should encourage diversity in herbicide use patterns for weed control as part of a long-term integrated management effort to reduce the risk of selection of metabolism-based multiple herbicide resistance in L. rigidum. © 2016 Society of Chemical Industry.

Study of Serum Cholinesterase levels in fish Clarias batrachus (Linn.) exposed to pesticides carbaryl and phorate.

Study of the Serum Cholinesterase levels (SchE) in the freshwater catfish Clarias batrachus when exposed to sub lethal dose of pesticides phorate and carbamate, was attempted in this paper. SchE levels decreased in the fish exposed to both the pesticides, the depletion being more pronounced with phorate. These results can be due to impairment of nervous system, liver damage as well as myocardial infarction. Similar findings were not only reported in experimental organisms but also found in human beings working in agricultural fields and pesticide manufacturing plants. Hence it is imperative that suitable occupational health and preventive measures need to be undertaken.

Pesticide induced alterations of non-protein nitrogenous constituents in the serum of a fresh water cat fish, Clarias batrachus (Linn.).

A freshwater cat fish was exposed to sublethal concentrations of two pesticides--carbaryl, a carbamate and phorate, an organophosphorus pesticide for 24, 72, 120 and 168 hr. The alterations in the serum profile of non protein nitrogen compounds demonstrated an increase in urea, uric acid and creatinine throughout the experimental period.

Biphasic responses in synergistic interactions.

Synergistic reactions, as exemplified by the methylenedioxyphenyl (benzodioxole) insecticide synergists, are one of the more studied interactions between toxicants. This group of chemicals includes, in addition to synergists such as piperonyl butoxide, carcinogens such as safrole and isosafrole and many compounds occurring naturally in foods, such as myristicin and piperine. These compounds may function as cytochrome P450 substrates, inhibitors and/or inducers. The biphasic curve in cytochrome P450 activities following a single dose is the result of an initial inhibitory phase followed by a phase of induction, with an eventual return to baseline levels. Both inhibition and induction may be isozyme-specific and different isozymes may be involved in the two activities of the same chemical. Details of these activities are presented and their significance is discussed.

Insecticides: their effect on microorganisms and persistence in rice soil.

A field experiment was conducted to investigate the effect of four insecticides, HCH, phorate, carbofuran and fenvalerate, at recommended doses on the preponderance of bacteria, actinomycetes and fungi. We also measured the persistence of the insecticides in the rhizosphere soil of rice. HCH and fenvalerate stimulated the proliferation of all of the microorganisms significantly. Phorate increased the population of bacteria and actinomycetes. Carbofuran accentuated the preponderance of actinomycetes in soil. Insecticides, in general, did not have marked influence on the proliferation of Bacillus, Streptomyces, Aspergillus and Fusarium in soil. However, we observed a stimulation of growth of Staphylococcus, Proteus and Sarcina with HCH, Pseudomonas, Corynebacterium, Erysipelothrix and Rhizopus with phorate, Serratia, Corynebacterium, Klebsiella, Escherichia, Rhizopus and Humicola with carbofuran, and Staphylococcus, Sarcina, Klebsiella and Nocardia with fenvalerate. On the other hand, there was an inhibition in growth of Pseudomonas, Micrococcus, Nocardia and Penicillium with HCH, of Pseudomonas, Micrococcus and Penicillium with carbofuran, and of Pseudomonas, Micrococcus and Micromonospora with fenvalerate. Different types of insecticides exhibited differential patterns of dissipation in soil. HCH had the highest persistence followed by phorate, carbofuran and fenvalerate, respectively.

Genotoxic effects of some organophosphorous pesticides. I. Induction of micronuclei in bone marrow cells in rat.

The genotoxic effects of 4 organophosphorous pesticides, i.e. ekatin, fenitrothion, methylparathion and phorate, were examined employing the micronucleus test in bone marrow cells of the rat. Methylparathion and phorate were found to be mutagenic, while ekatin was weakly mutagenic. The frequency of micronuclei induction by fenitrothion did not differ significantly from that noticed in negative control.

The effects of phorate and some of its metabolites incorporated in an artificial diet on liquid uptake by Aphis fabae scop.

[14C]Phorate and some of its metabolites were incorporated in an artificial diet and their effects on liquid uptake by Aphis fabae were studied. At sublethal and very low toxicity levels of phorate there was a tendency for a reduction in feeding with increasing concentrations. [14C]Phorate sulphone, [14C]phorate sulphoxide and [14C]phoratoxon sulphoxide at high concentrations gave very low mortality figures, but a significant drop in liquid uptake occurred with increasing concentrations. The results demonstrate that the presence of the insecticide rendered the diet less acceptable to the aphids which exhibited a wandering behaviour that might promote transmission of virus diseases.

Feeding behaviour and susceptibility of Myzus persicae (Sulz) and Brevicoryne brassicae (L.) to [14C] phorate in artificial diet.

The effect of artificial diet on the growth and reproduction of the aphids Myzus persicae (Sulz) and Brevicoryne brassicae (L) was studied. Following the application of [14C] phorate to the diet, the results showed that B. brassicae was more susceptible than M. persicae. In these experiments the dead and live aphids and their honeydew were also analysed. The dead aphids contained more toxic 14C than the live ones with a direct correlation between the amount of insecticide in the diet and the insecticide extracted from the aphids. The total amount of 14C imbided by aphids was calculated but it bore no correlation with the insecticide applied. The amounts of honeydew produced before and after application of the insectide were measured. In both the species the honeydew production was increased as the insecticide was increased from sublethal doses until the toxic range was reached when honeydew production fell gradually. The results obtained from foliar application of the insecticide were compared with those following treatment of the diet. It was found that the aphids were more susceptible to insecticide applied to the diet.

Pharmacological studies on the molluscicidal activity of phorate on Pila globosa (Gastropoda).

Amongst heart, rectum and radula protractor muscles of Pila globosa, the heart showed a negative inotropic and negative chronotropic response while the rectum and radula protractor showed a positive tonotropic response to exogenously applied acetycholine (ACh). The anti-cholinesterase pesticide phorate substantially increased the response to ACh; at high doses it could also evoke cholinomimetic response from the heart. The anti-cholinesterase property of phorate gradually increased with an increase in its contact period to the tissue. The extent of alteration in ACh response caused by prior treatment with low and high doses of phorate were very similar, indicating that the efficacy of phorate is by and large time-dependent rather than dose-dependent. The effect of phorate remained irreversible even after prolonged washing. The mode of action of phorate has been discussed in the light of the above findings.

Effect of some insecticides on the periodic activity of the fresh-water mussel (Anodonta cygnea L.).

The effect of the insecticides Hungaria L-7, Dimecron-50, Thimet-10 G and Satox 20 WSC containing lindane, phosphamidon, phorate and trichlorfon, respectively, as active ingredient was investigated on the survival and pumping behaviour of the fresh-water mussel Anodonta cygnea L. The shortening of active periods was used as indicator of the sublethal effects. Hungaria L-7, Thimet-10 G and Satox 20 WSC caused significant inhibition of the filtering activity, while Dimecron-50 was less effective. Fifty per cent shortening of active periods required 6 X 10-3 g/l Hungaria L-7, 8 X 10-3 g/l Thimet-10 G and 2 X 10-2 ml/l Satox 20 WSC. Thimet and Satox were lethal at 10-1 g/l and 1 m/l concentrations, respectively. Although the mechanism of the effect can be different with various substances, the results have shown, that monitoring of the activity of mussels can be a suitable test for the biological indications of water pollution.

The effect of some pesticides on the rhythmic activity of adductor muscle of fresh-water mussel larvae.

The effect of some pesticides on the rhythmic and tonic activity of adductor muscle of fresh-water mussel (Anodonta cygnea) larvae was investigated in short-term experiments. In the examined concentration range, Dimecron-50 does not influence the rhythmic activity of adductor muscles, while high concentrations of Gramoxone (is greater than 1 ml/l), Thimet-10 G (is greater than 5 x 10(-1) g/l) and Hungaria L-7 (is greater than 10(-1) g/l) cause a slight increase in it. These substances also induce a prolonged tonic contraction of a small proportion (10%) of larvae. Hungaria L-7 makes an exception, causing considerable contracture (30%). The concentrations inhibiting the TA activation by 50% are: 6x 10(-1) ml/l Dimecron-50; 2.5 x 10(-1) ml/l Gramoxone; 10(-1) g/l Hungaria L-7 and 8x 10(-2) g/l Thimet-10 G, while the 50% inhibition of the nonspecific ACh activation is resulted by 2 x 10(-1) ml/l D-50. It is concluded that contamination of environmental waters with Dimecron-50, Thimet-10 G or Hungaria L-7 may be injurious also for Pelecypoda larvae, that may contribute to the unbalancing of the water ecosystem.