| Abstract: | Cadmium toxicity reduces the species diversity of soil microbial communities and their ability to metabolize different carbon substrates. However, it is not yet clear whether there is a relationship between loss of species diversity and the metabolic rates at which different substrates are used. In this research, the ability of a soil microbial community to metabolize 31 C substrates was examined using Biolog Ecoplates amended with Cd over a range of concentrations (0, 5, 10, 20, 50  g ml–1). After 48 h growth, the bacterial communities that were produced on ten of the substrates were characterized in relation to their 16S rDNA profiles by PCR denaturing-gradient gel electrophoresis. Results showed that both the microbial growth rates and the numbers of substrates that were used were reduced with increasing Cd concentration. When examined across all substrates, approximately 30% of the 16S rDNA bands representing different bacterial species were eliminated by 5 g Cd ml–1. However, there was considerable variation in the bacterial community responses with different C substrates. Both cluster analysis and discriminant analysis indicated that the bacterial community structures could be grouped into sensitive, moderately sensitive, and Cd-resistant communities. |
