Abstract
One of the beneficial roles of the microbial population is their ability to convert toxic herbicides to lesser toxic compounds such as water and carbon (IV) oxide. Paraquat which is an acutely toxic herbicide is used on farmlands and has been found to affect human health. This study was aimed at characterizing bacteria with the potential to degrade paraquat. Previously isolated bacteria from culture collection labelled A-F were screened for their potential to degrade and utilized paraquat as the sole carbon source in Bushnell Hass agar media. Of the six isolates, isolate E (Morganella sp.) was observed to have the highest growth and tolerance to paraquat after 72 h of incubation at 37 ºC. Characterization study revealed that Morganella sp. can utilize and grow with optimum conditions of pH 6.5, the temperature of 30 ºC and can tolerate up to 400 mg/L paraquat concentration with an increase in growth as inoculum size increases. Thus, these findings showed that Morganella sp. can degrade toxic paraquat to a less toxic form and therefore can be a good isolate for the future bioremediation process of the pollutant.
Highlights
The use of chemical compounds in modern agricultural systems have become common, one group of such chemicals is a herbicide, used to control weed, protect crops and increase agricultural yield [1]
Screening of Isolates for Paraquat Biodegradation A total of six (6) molybdenum-reducing bacteria was previously isolated from agricultural soils in Kano state were screened for their potentials to degrade Paraquat and utilize it as a sole carbon source
Paraquat concentration was observed to be optimum at 400 mg/L for this isolate with a decline in growth on increasing the concentration to 800 mg/L (Fig. 1)
Summary
The use of chemical compounds in modern agricultural systems have become common, one group of such chemicals is a herbicide, used to control weed, protect crops and increase agricultural yield [1]. In vivo toxicity study of paraquat showed the herbicide can cause lipid peroxidation of cell membranes, damaging the cells in mice [2]. Study of lungs tissue of rats after a single oral dose of paraquat indicated pulmonary oedema, swelling of the epithelium, an increase in collagen, and an effect on the ribosomes of the membranous pneumocytes [3]. It produces degenerative lesions in the lung after systemic administration to man and animals [4]. Acute multiorgan failure and mortality occur during the first two days after PQ consumption of more than 40 mg/kg, but PQ consumption less than 20 mg/kg is associated with moderate symptoms and the majority of patients survive
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