Molecular identification and characterization of endophytic bacteria from root of chamaecrista rotundifolia growing on the nigerian air force shooting range, kaduna.

Abstract

Chamaecrista rotundifolia is one of the few plant species growing on heavy metal-contaminated Nigerian Air Force shooting range, Kaduna. This microbially unexplored plant species can have microbial association with endophytes. This study was aimed at isolating, identifying and characterizing endophytic bacteria associated with the roots of Chamaecrista rotundifolia growing on the Nigerian Air Force shooting range, Kaduna. The identification of the endophytic bacteria was done using standard biochemical methods and 16S rRNA sequencing analysis. The isolates were then screened for antibiotic resistance, plant growth promoting properties and heavy metal tolerance using standard techniques.  Varied concentrations of heavy metal salts (Pb²⁺, Cr³⁺, Ni²⁺ and Mn²⁺) were used to test the isolates for their heavy metal tolerance. Four endophytic bacteria isolated from the roots of C. rotundifolia were Aerococcus viridans, Peribacillus simplex, Staphylococcus simplex and Pseudomonas aeruginosa. Results on antibiotic sensitivity test revealed that the four isolates were resistant to most of the antibiotics. The isolates possessed plant growth promoting properties by showing positive results for Indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylic (ACC) deaminase activity and phosphate solubilizing. Results also revealed that the isolates showed some degree of tolerance to the heavy metals. The tolerance of both A. viridans and P. simplex to chromium and manganese showed significant difference (p<0.05) across all the concentration levels of the metal salts. It is therefore concluded that Chamaecrista rotundifolia growing on Nigerian Air Force shooting range, Kaduna, is associated with endophytic bacteria which could be the reason the plant species thrive in heavy metal-contaminated site.