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

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.