Production of 1-aminocyclopropane-1-carboxylic acid deaminase (ACC) by Burkholderia cepacia as an indicator of cadmium contamination

Abstract

The most common sources of cadmium are volcanic, biological and anthropogenic processes such as industry, manufacturing, metallurgy and fertilizer use. In Colombia, there is evidence that cadmium is introduced into the soil by the use of agrochemicals in agriculture, contact with waste water, the use of irrigation water containing this element or by the deposition on the surface of wet and dry particles that are carried by the air from industrial processes. This metal can be absorbed by plants in contaminated soils and its incorporation into the food chain, which motivated this study to isolate rhizospheric bacteria; to evaluate in vitro the capacity of these bacteria to tolerate different cadmium concentrations and the capacity to produce the enzyme 1-aminocyclopropane-1-carboxylic acid deaminase (ACC) in vitro. The cadmium values in the rhizosphere were 0.95 ± 2.21 mg/kg and, according to international reference values, correspond to soils in the highly toxic category. The results of the in vitro bacterial tolerance test showed that the maximum tolerance capacity was 500 ppm Cd. Furthermore, these morphotypes showed qualitative siderophore production activity. The results of the identification by sequencing of the 16S DNAr gene showed high homology with the bacterium Burkholderia cepacia, which according to several studies corresponds to a bacterium with the capacity to produce different heavy metals such as cadmium and lead and the capacity to promote growth in plant species that grow in environments contaminated with these metals.