Quantification of microbial diversity in biofilms using denaturing gradient gel electrophoresis profile

Microbial diversity affects thickness, structural complexity and ecological stability of biofilms. This study was conducted to demonstrate that diversity of biofilms might be quantified by either of two indices, Shannon-Weaver and Simpson, based on the DGGE (denaturing gradient gel electrophoresis) profiles of DNA extracted from the communities. Using such a method, the diversity indices of anaerobic marine biofilms were estimated, and compared with those of the corresponding microbial communities in suspension. The DGGE profiles of DNA revealed the presence of 22 species in both communities. The Shannon-Weaver and Simpson indices of the biofilms averaged 2.69 and 0.19 , respectively. The former was about 9% lower and the latter was about 16% higher than the corresponding indices of the suspended communities. Results in both cases show that the suspended communities were more diverse than the biofilms. Details of the biofilm and suspended communities, derivations of both indices and implications of these results will be discussed.