Screening for and isolation and identification of malathion-degrading bacteria: cloning and sequencing a gene that potentially encodes the malathion-degrading enzyme, carboxylestrase in soil bacteria

Abstract

Five malathion-degrading bacterial strains were enriched and isolated from soil samples collected from different agricultural sites in Cairo, Egypt. Malathion was used as a sole source of carbon (50 mg/l) to enumerate malathion degraders, which were designated as IS1, IS2, IS3, IS4, and IS5. They were identified, based on their morphological and biochemical characteristics, as Pseudomonas sp., Pseudomonas putida, Micrococcus lylae, Pseudomonas aureofaciens, and Acetobacter liquefaciens, respectively. IS1 and IS2, which showed the highest degrading activity, were selected for further identification by partial sequence analysis of their 16S rRNA genes. The 16S rRNA gene of IS1 shared 99% similarity with that of Alphaprotoebacterium BAL284, while IS2 scored 100% similarity with that of Pseudomonas putida 32zhy. Malathion residues almost completely disappeared within 6 days of incubation in IS2 liquid cultures. LC/ESI-MS analysis confirmed the degradation of malathion to malathion monocarboxylic and dicarboxylic acids, which formed as a result of carboxylesterase activity. A carboxylesterase gene (CE) was amplified from the IS2 genome by using specifically designed PCR primers. The sequence analysis showed a significant similarity to a known CE gene in different Pseudomonas sp. We report here the isolation of a new malathion-degrading bacteria from soils in Egypt that may be very well adapted to the climatic and environmental conditions of the country. We also report the partial cloning of a new CE gene. Due to their high biodegradation activity, the bacteria isolated from this work merit further study as potential biological agents for the remediation of soil, water, or crops contaminated with the pesticide malathion.

Factors Affecting Performance of Soil Termiticides

“…However, several other studies have found little microbial degradation of chlorpyrifos. Goda et al (2010) showed that the intact cells of Pseudomonas putida IS168 were able to degrade fenitrothion, diazinon and profenofos when present as sole carbon sources, but failed to grow on chlorpyrifos. Trichloropyridinol (TCP), one of the main chlorpyrifos metabolites, has antimicrobial properties (Cáceres et al, 2007;Feng et al, 1997;Racke et al, 1990), possibly accounting for the scarcity of chlorpyrifos-degrading microorganisms.…”

Isolation and characterization of two malathion-degrading Pseudomonas sp. in Egypt

“…Due to extensive use of malathion, exposure risk of living organisms including human beings is very high. Malathion degradation by microorganisms has been reported by several items (Goda et al, 2010;Singh et al, 2012;Janeczko et al, 2014).…”

“…There are different types of enzymes responsible for the degradation of OPCs, the most important of them are phosphotriesterases and carboxylesterases (Goda et al, 2010). Carboxylesterases are enzymes found in the α/β-hydrolase fold family that catalyze the hydrolysis of carboxyl esters via the addition of water (Hosokawa et al, 2007).…”

“…Carboxylesterases are enzymes found in the α/β-hydrolase fold family that catalyze the hydrolysis of carboxyl esters via the addition of water (Hosokawa et al, 2007). Several researchers isolated and fully characterized carboxylesterase enzymes recovered from different microorganisms (Hosokawa et al 2007;Li et al, 2007;Goda et al, 2010). Li and colleagues (2007) were able to fuse carboxylesterase enzyme with a green fluorescent protein that made their organism easily detectable in the environment following the degradation of pesticide residues.…”

Comparison of different models of substrate inhibition in aerobic batch biodegradation of malathion

“…Several studies have examined the degradation of malathion by microbes (Xie et al, 2009;Goda et al, 2010;Singh et al, 2012) and most of these studies were carried out using pure cultures. Little information is available concerning degradation of malathion by activated sludge culture (Barik et al, 1984;Kanazawa, 1987 Evaluation of substrate inhibition becomes an important consideration in the treatment of toxic compounds in engineered systems such as activated sludge processes (Hao et al, 2002), and mathematical modeling can be helpful for understanding the behavior of biological processes and predicting the component concentrations in the system (Tziotzios et al, 2008).…”