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Bioremediation for Sustainable Environmental Cleanup

(Subashchandrabose et al. 2013). The two processes use living organisms to metabolize xenobiotics,

recalcitrant and toxic materials found in soil, water and sediments (Avila et al. 2021). There has been

extensive research on the biological removal of pesticides by microorganisms, including bacteria

(Arthrobacter, Bacillus, Corynebacterium, Flavobacterium, Pseudomonas and Rhodococcus), algae/

cyanobacteria (Chlorella, Scenedesmus, Synechococcus, Phormidium, Nostoc sp., Oscillatoria,

Anabaena sp., and Aulosira) and fungi (Penicillium, Aspergillus, Fusarium and Trichoderma)

(Nicolopoulou-Stamati et al. 2016). Several species display a strong pesticide degradation activity

and are highly adaptable (Subashchandrabose et al. 2013, Huang et al. 2018, Tarla et al. 2020). With

advanced metabolic mechanisms, microorganisms can use or transform pesticide molecules into

non-toxic or less hazardous forms of metabolites (Huang et al. 2018). This chapter aims to describe

the current status of pesticide pollution, and the types and mechanisms involved in microbe-assisted

bioremediation of pesticides.

7.2 Types of Pesticides

The term “pesticide” is used to describe a variety of insecticides, herbicides, fungicides, rodenticides

and garden chemicals. They may be grouped according to the type of pest to be controlled and by

their mode of action, penetration, chemical composition and toxicity (Table 7.1) (Castelo-Grande

et al. 2010). Pesticides are classified according to their chemical nature as organochlorine pesticides,

organophosphorus pesticides, carbamates and other pesticides such as pyrethroids, triazine, and

neonicotinoids (Nicolopoulou-Stamati et al. 2016). The use of pesticides creates significant risks to

the environment and non-target organisms, such as beneficial soil microorganisms, plants, fish and

birds. The main classes of pesticides are considered as follows:

7.2.1 Organochlorine Pesticides

Organochlorine pesticides (OCPs) are chlorinated hydrocarbons that have been extensively used since

the 1940s for commercial agriculture, mosquito, termite and tsetse fly control (Nicolopoulou-Stamati

et al. 2016). The widely known organochlorine pesticides are dichlorodiphenyltrichloroethane,

dieldrin, endosulfan, heptachlor, dicofol and methoxychlor (Nicolopoulou-Stamati et al. 2016).

These chemical substances act upon the pest’s nervous system by disrupting the enzyme that regulates

neurotransmitters (Huang et al. 2018). After application, they remain in the environment for up to

three decades and accumulate in water, food and sediments (Kafilzadeh 2015). Many studies suggest

the toxic potential of OCPs to human health including reproductive failure, birth defects, endocrine

disorders, lipid metabolism, immune system dysfunction and cancer (Lehmann et al. 2018, Tarla

et al. 2020, Bose et al. 2021, Gonçalves and Delabona 2022, Mali et al. 2022). Consequently, in

many countries, several OCPs are no longer permitted due to health and environmental concerns.

7.2.2 Organophosphorus Pesticides

Organophosphorus pesticides (OPPs) are known as one of the major groups of pesticides widely

used in agriculture to control pests from exhibiting undesirable behavior. These include esters of

phosphoric acids as an alternative to organochlorine in pesticides (Mali et al. 2022). The most

widely used OPPs are glyphosate, chlorpyrifos, monocrotophos, acephate, bromophos, ectophos,

leptophos, quinalphos, malathion, parathion, dimethoate, tribufos, merphos and trichlorofon (Foong

et al. 2020). Studies have reported that these chemicals persist in soil for up to 10 to 360 d (Singh

and Walker 2006). Thus, posing increased environmental risk to flora and fauna in terrestrial and

aquatic ecosystems. Many ecosystems have been contaminated by OPPs, and they present threats

such as cardiovascular disease, dementia, neurological problems, autoimmune disorders, negative

effects on the reproductive system and other adverse effects on human health (Subashchandrabose

et al. 2013, Gonçalves and Delabona 2022).