Effect of herbicides on cellular growth, microbiological and physiological activities of an identified rhizosphere isolate Rhodococcus erythropolis

Abstract

ABSTRACT Considering the excessive pesticide pollution in the environment, atrazine (ATZ), butachlor (BCR) and quizalofop-p-ethyl (QUIZ) were selected to assess their toxic effect on Rhodococcus erythropolis PSB-6 (NCBI Accession No. MG028649). MIC values of ATZ, BCR and QUIZ to R. erythropolis were determined to be 100, 200 and 150 μM, respectively. Biomarker enzymatic assays including LPO, LDH and oxidative stress (CAT) induced by herbicides represented significant (p ≤ 0.005) toxicity towards strain PSB-6. Herbicide-induced morphological changes viz. aberrant margins; cellular cracking and distortion/damage in R. erythropolis cells were apparent under SEM observation. Furthermore, herbicide-treated and DAPI (4’,6-diamidino-2-phenylindole)-stained cells showed concentration-dependent reduction in cellular permeability as revealed under CLSM. Furthermore, herbicides displayed toxicity towards bioactive molecules of PSB-6 in a dose-related manner. Among them, ATZ imparted maximum negative effect, where it reduced the bacterial production of IAA, ACC deaminase and 2, 3-DHBA by 68% (p ≤ 0.001), 75% (p ≤ 0.001), and 83% (p ≤ 0.005), respectively, over control. Additionally, following herbicide exposure, bacterial counts (log10 CFU mL−1) were reduced. Higher concentrations of ATZ and BCR completely reduced the growth patten of strain PSB-6. The current investigation provides an insight into a mechanistic approach of chemical herbicide-induced hazard toward a beneficial soil isolate. Careful monitoring is therefore necessary before agricultural application of pesticides.