Characterization of Bifenthrin Degrading Bacteria from Cotton

CONTENTS

Introduction

Material and Methods

Results

Discussion

Summary and Conclusion

Bibliography

ACKNOWLEDGEMENT

Writing a book is harder than we previously believed and more rewarding than we could have ever imagined. The sense of satisfaction provides enormous happiness as we are contributing something good to the Society.

We sincerely acknowledge financial and infrastructural support extended by P.D. Patel Institute of Applied Sciences, Charotar University of Science and Technology, Changa – 388 421 (Gujarat, India) to carry out research. Overall support by the Management of Charotar University of Science and Technology is duly acknowledged. We are grateful to Professor R. V. Upadhyay, Principal and Dean (Applied Sciences) for complete freedom and necessary support. We also thank Head, Department of Biological Sciences for timely support.

Our acknowledgement would remain incomplete, if we do not thank Ms. Hardi Sinde, Ms. Priyanka Patel, Ms. Asra Dosani, Ms. Shivani Shah and Ms. Dolly Dave for necessary help and support during the tenure.

Finally, we thank our family members and friends.

Bhavtosh A. Kikani and P. D.

CHAPTER: 1

INTRODUCTION

1.1 POLLUTANTS AND PESTICIDES

A large number of pollutants and waste materials are released into the environment annually. Approximately 60,000 to 90,000 chemicals are used commercially, which get accumulated in their surroundings leading to environmental imbalance. This in turn has adversely affected the ecosystem. The environmentalists all over the world are trying to overcome this problem and raising their voice at international platforms; their words are ignored and till date without caring of adverse consequences many substances are still being used (Shukla et al., 2010). Among these chemicals we find pesticides, which are any substance or mixture of substances that are used to control pests such as insects, rodents, fungi and unwanted vegetation (weeds) that endanger our food supply, health, or comfort. In particular, the term pesticides refers to the chemicals that alters the biological processes in living organisms specific to pests which includes herbicides, insecticides, fungicides and disinfectants.

Due to increased destruction of crops by pests, production and use of varieties of pesticides has also been increased to minimize infestations by pests and thus protects crops from reduction of product quality and potential yield losses (Damalas, 2009).The use of pesticides grabs an important place in modern agriculture, as they are extremely necessary for economical pest management (Gouma, 2009). However, their repeated application creates adverse effects on target and non-target forms of life. So mineralisation of these substances to non-toxic or less toxic metabolite is of concern. Various technology have been developed; however, bioremediation involves bioaugmentation has emerged as the most dominant and advantageous method for tidying up pesticide contaminated soils.

1.2 SYNTHETIC PYRETHROIDS (SPs)

Among all the commercially available pesticides, Synthetic Pyrethroid (SP) family of pesticide is widely used all over the world. Synthetic pyrethroids are compounds that are chemical analogs to pyrethrins, a potent insecticidal ester that is naturally derived from certain chrysanthemum flowers (George and Kalyanasundaram, 1994). However pyrethrins degrades very rapidly in the environment, they are never been used at a large scale in agriculture and limited their use (Laskowski, 2002; Palmquist et al., 2012).

Besides organophosphates (OPs), pyrethroids are meant to be the safer alternative and less toxic, their applications significantly increased when the use of OPs was limited or banned. Presently pyrethroids occupies above 25% of the world’s total pesticide market (Laffn et al., 2010; Pérez et al., 2010). Pyrethroids have a high biological activity and are used for more than 20 years all over the world to control pest insects in agriculture, public and commercial buildings, animal facilities, greenhouses, horticulture and forestry and for indoor home use (Katsuda, 1999).

Although pyrethroids have agricultural benefits but their widespread and continuous application is a major problem as they contaminate terrestrial and aquatic ecosystems and affect non-target organisms. Since pyrethroids have greater stability in the soil, they are not degraded immediately after the application and because their residues are detected in the soil, there is an urgent need to clean up pyrethroid-polluted environment.

1.2.1 CATEGORY OF SPs

SPs are broadly classified into first, second and third generations based on the modifications in the molecular structure of natural pyrethrins.

First generation

The first generation was developed in the 1960s which are more active and it involves several pyrethrin derivatives such as bioallethrin, tetramethrin, resmethrin, and bioresmethrin. However the rapid photodegradation limited their use.

Second generation

The second generation was developed in 1970s which involves permethrin, cypermethrin and deltamethrin. Other insecticides such as fenvalerate, lambda-cyhalothrin and betacyfluthrin were synthesized in the subsequent years (Katsuda, 1999).

Third generation

This category involves bifenthrin which is characterized by greater photostability and greater insecticidal potency than first and second generation pyrethroids (Mokry and Hoagland, 1990).

1.2.2 CLASSES OF SPs

Based on their toxicological and physical properties, pyrethroids are categorized into two separate classes—type I and type II. Type I pyrethroids, characterized by absence of cyano group in their chemical structure. It includes allethrin, bifenthrin, d-phenothrin, permethrin, resmethrin, and tetramethrin. Type II pyrethroids, conversely they have a cyano group in their chemical structure. It includes cyhalothrin, cypermethrin, cyfluthrin, deltamethrin, fenvalerate, fluvalinate, and lambda-cyhalothrin (Laskowski, 2002).

The commercial products may contain a mixture of various isomers as pyrethroids are composed of two, four or eight isomers which increase the complexicity. The varying isomeric ratios in commercialization of SPs may be the reason for the variations in the toxicity of the same compound (Delgado-Morenoetal et al., 2011).

1.3 PYRETHROIDS OVER OTHER PESTICIDES

As compared to other insecticides and pesticides like organophosphates, organochlorides and others, pyrethroids are: a) Cost effective, b) Greater stability in the environment i.e. stability against photodegradation c) Hydrophobic nature i.e. water insolubility d) Broad spectrum i.e. effective against the wide range of insects and pests e) greater insecticidal potency f) less mammalian toxicity i.e. safe compared to other insecticides. All these features make pyrethroid to be more effective.

1.4 BIFENTHRIN

Bifenthrin is a third generation class II type of SP, characterized by strong environmental persistence and greater insecticidal potency then previous pyrethroids. Bifenthrin is virtually stable against photolysis and hydrolysis and is widely used in agriculture sector all over the world. Bifenthrin remains stable for two years at 25 °C and 50 °C and in natural day light the half-life is 255 days (Tomlin, 2009).

1.4.1 Structure of bifenthrin

2-methyl-3-phenylphenyl) methyl 3-[(Z)-2-chloro-3, 3, 3-trifluoroprop-1-enyl]-2, 2- dimethylcyclopropane-1-carboxylate

Abbildung in dieser Leseprobe nicht enthalten

Structure of bifenthrin (Pubchem)

1.4.2 Insecticidal potency of bifenthrin

Little research has been done specifically on bifenthrin mode of action on invertebrates or vertebrates, however, most investigations have found that the pyrethroid family of pesticides demonstrate very similar effects on invertebrate nervous systems (Miller and Salgado, 1985). Bifenthrin is a neurotoxic insecticide having slight repellent effect acting through direct contact and ingestion. The primary biological effects are inhibition of the voltage- gated calcium channels coupled with a stimulatory effect on the voltage- gated sodium channels in insects and vertebrates. All pyrethroids share similar modes of action, affecting both the peripheral and central nervous systems, and act as axonic poisons. They stimulate repetitive action by binding to voltage-gated sodium channels, prolonging the sodium ion permeability in the nervous system. This leads to spontaneous de- polarizations, augmented neurotransmitter secretion rate and neuromuscular block, which ultimately results in paralysis of the insect and eventually lead to the death of the insects (Burr and Ray, 2004; Hintzen et al., 2009).

1.4.3 Adverse effect of bifenthrin

Although, Bifentrhin is considered environmentally safe but its continuous use has led to permanent occurrence in the soil and may negatively affect non-target organisms such as fish and aquatic beetles (Desneux et al., 2007), insects (Wendt-Rasch et al., 2003; Antwi and Reddy, 2015), parasitic wasps (Longley and Jepson, 1996), bees (Decourtye et al., 2005), and microorganisms (Cyco´n et al., 2016; Das et al., 2016). It is thought that many SPs may be responsible for disruptions of the endocrine system, suppression of the immune system, reproductive damage and increased chances of cancer in humans (ATSDR, 2003). Cancer Classification classifies bifenthrin as Group C Possible Human Carcinogen . According to the WHO Recommended Classification of Pesticides by Hazard, Bifenthrin (technical grade) is identified as Class II: moderately hazardous pesticide.

SPs, such as BF, are associated with developmental effects, immunological abnormalities, and neurotoxicity (DeMicco et al., 2009; Soderlund, 2012). The reported neurotoxic effects of BF and other pyrethroids are considered to be primarily mediated by their interaction with sodium channels, leading to membrane depolarization and hyper excitability of neuronal cells (Cao et al., 2014). This group of pesticides has also been shown to act on isoforms of voltage sensitive calcium channels, thereby contributing to the release of neurotransmitters and hence leading to induced toxicity (Cao et al., 2011; Soderlund, 2012; Yang and Li, 2015). Few cases are presented with cardiovascular symptoms such as high blood pressure, irregular heartbeat, and heart attack. Bifenthrin exposure, even at "acceptable" limits, can increase the frequency and risk of diseases such as asthma and also can generate inflammatory responses.

ECOTOXICITY STUDIES: based on the available data, bifenthrin has been classified as slightly toxic on an acute basis to birds and showed no adverse effects to reproduction at the highest concentration. According to Mammalian toxicity data suggestion, bifenthrin is moderately toxic to small mammals on an acute basis. On an acute and chronic basis, bifenthrin is highly toxic to freshwater fish and aquatic-phase amphibians. Bifenthrin has also been classified as very highly toxic to freshwater and marine fish and aquatic invertebrates.

1.4.4 Environmental stability of bifenthrin

Cyco´n et al. (2014) found the highest dissipation of pyrethroids in soils is characterized by the highest organic matter content. As per their results, organic matter and clay content are the major factors that control the bioavailability of pyrethroids for microorganisms. The lipophilic and hydrophobic properties result in their strong tendency to bind various organic and non-organic soil components and can persist in soils for a long period which allows them to leach into the groundwater and to form residues of these compounds. However, the adsorption and desorption processes are associated with other soil parameters such as pH and water content (Oudou and Hansen, 2002; Gu et al., 2008; Muñoz-Leoz et al., 2009) which makes them more stable against degradation. Because of its high octanol water coefficient and ability to adsorb to soils, bifenthrin has a low potential to contaminate ground water.

1.4.5 Applications of bifenthrin

Bifenthrin is registered for use to control a variety of insects including aphids, worms, ants, gnats, moths, beetles, grasshoppers, mites, midges, spiders, ticks, yellow jackets, maggots, thrips, caterpillars, flies, fleas, and other pests in public health, domestic, agricultural, and industrial situations.

1.5 MICROBIAL DEGRADATION OF PYRETHROIDS

Among the various methods proposed the use of pesticide degrading microorganisms with effective hydrolyzing enzyme is thought to be the most promising. The most useful are microorganisms capable of degrading many pyrethroids. The microbial degradation of the pyrethroids have been most commonly used for many years such as allethrin, bifenthrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenpropathrin, fenvalerate, and permethrin. Some of them are characterized, having capability of degrading pyrethroid and special attention is given to the bacterial strains from the genera Achromobacter, Acidomonas, Bacillus, Brevibacterium, Catellibacterium, Clostridium, Lysinibacillus, Micrococcus, Ochrobactrum, Pseudomonas, Serratia, Sphingobium, Streptomyces, and the fungal strains from the genera Aspergillus, Candida, Cladosporium, and Trichoderma. Many studies have been reported on microbial degradation of class I and class II SPs except bifenthrin. Little research has been done on bifenthrin and the pathway by which degradation of bifenthrin takes place is unknown. Few studies have been reported on microbial degradation of bifenthrin by some fungal strains and some bacterial genera.

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