Isolation, identification and acclimatization of Atrazine-resistant soil bacteria

Abstract

The present study aimed to isolate and identify and acclimatize Atrazine-resistant soil bacteria from different contaminated soils in order to be used for bioremediation of polluted environments. Bacteria were isolated from three soil types cultivated with corn and cucumber and amended with Atrazine. Soils were collected from different ecosystems (Abu El-Matameer area, El-Behaira Governorate, Egypt (SoilM), Hada Al-Shame area, Saudi Arabia (SoilH), and El-Sharqia Governorate, Egypt (SoilE) and used in comparative study to investigate the fate of Atrazine. The applied herbicide was tested at 3 elevated doses, dose recommended by the Ministry of Agriculture(RD), half the recommended dose (1/2 RD) and double the recommended dose (2X RD). Physical, chemical, mechanical and biological properties of soils were characterized to determine how they affect and affected by soil indigenous microorganisms. Indigenous and three exogenous bacterial isolate were subjected to a preliminary screening toxicity test obtaining 23 isolate best grown at the 2X RD. Sequences of the tested isolates were affiliated according to their 16S rDNA gene to members of 5 genera, namely Enterobacter (E. cloacae), Bacillus (B. cereus andB. anthracis), Pseudomonas (P. aeruginosa, P. balearica, P. indica and P. otitidis), Ochrobactrum (O. intermedium) and Providencia (P. vermicola) with similarities ranged between 91% and 99%. Resistant bacteria were individually enriched in 2X RD Atrazine amended-liquid cultures for 10 days to select the most promising acclimatized bacteria for biodegradation of Atrazine in the contaminated soils. Enrichment of the resistant isolates led to obtain seven isolates that exhibited remarkable stimulation (S: 70.7–88.7%) in their growth and considered acclimatized and highly Atrazine-resistant. Therefore, they can efficiently be used for degradation of Atrazine-contaminated soil and/or wastewater.