Analysis of carbon source metabolism functions of cadmium-tolerantbacteria separated from rice (Oryza satiua) rhizosphere

To understand metabolic abilities of carbon sources in three cadmium-tolerant bacteria (strain A, strain B and strain C) isolated from rice rhizosphere soils, basic characteristics of bacteria strains were determined by physiological and biochemical reactions and metabolic functions of carbon sources analyzed via the BIOLOG ECO plate method. The main principle was based on the fact that color-reduction reaction showed differences in carbon source utilization. The physiological and biochemical characteristics showed that all three bacteria strains behaved as Gram-negative with born flagellum. Strain C was identified as Pseudomonas aeruginosa, while strains A and B both belonged to different Pseudomonas species. The conclusions on physiological and biochemical characteristics were the same as in previous molecular identifications. BIOLOG ECO analysis showed that average well color development (AWCD) nearly approached the maximum after culturing the strains for 72 hours. Significant differences were noted in AWCD among cultured strains for 24 hours, dominated by amino acid utilization efficiency. Among the thirty-one single carbon sources used, higher utilization rates were noted in nine compounds. The compounds included N-Acetyl-D- glucosamine, L-Arginine, L-Asparagine, Itaconic acid, Putrescicine, 4-Hydroxy benzoic acid, Pyruvic acid methyl ester, Tween 40 and Tween 80. Also significant differences were detected among the three bacteria strains regarding utilization rates of L-Arginine, Itaconic acid and Pyruvic acid methyl ester. On the basis of carbon source utilization, more information was gathered on strain functions. Thus this study expanded our knowledge on needed carbon sources for cadmium-tolerant strain growth. The study also taught us optimization strategy of cultured media which was beneficial for future research work. Furthermore, it provided precious microorganism resources for constructing corresponding bacteria gene engineering.