Degradation of phenoxyalkanoic acid herbicides by isolated bacterial strain LKDC4 Pseudomonas aeruginosa

Abstract

Phenoxyalkanoic acid herbicides are widely used in agricultural lands to kill the weeds in crop fields and have a very detrimental effect on soil’s natural fertility and its microbiome. Bacterial culture isolated from these lands in the presence of herbicides group 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2-Methyl-4-chlorophenoxy acetic acid (MCPA) belongs to plant growth hormone auxin. Strain LKDC4 Pseudomonas aeruginosa exposed to both herbicides at a range of concentrations 300 mg/L, 500 mg/L and 700 mg/L for 5 days without any enrichment culture, providing 2,4-D and MCPA as a carbon source for survival. LKDC4 shows a maximum number of cell growth in 2,4-D herbicide at the lowest concentration 300 mg/L (1.35 mM) comparatively with the highest concentration 700 mg/L (3.16 mM) of optical density 0.85 and 0.78 at 600 nm, respectively. At the same time, this strain shows a similar number of cell growth at all three concentrations 300 mg/L, 500 mg/L, and 700 mg/L of 1.49 mM, 2.49 mM, and 3.48 mM respectively of optical density 0.90 at 600 nm. The degradation efficiency of the Pseudomonas aeruginosa LKDC4 was 70 to 80% of 2,4-D herbicide when the growth medium contained 0.2% glucose as the only carbon source after 5 days at optimum conditions. The degradation of MCPA was 100% at 300 mg/L and 700 mg/L, while 81% degradation at 500 mg/L after 5 days of incubation at optimum conditions. P. aeruginosa can degrade both herbicides and survive well in their presence, making it a tolerant microbial strain.