Change in the Bacterial Community of Natural River Biofilm during Biodegradation of Aniline-Derived Compounds Determined by Denaturing Gradient Gel Electrophoresis

Abstract

The biodegradation capacity of planktonic cells and biofilms obtained from a natural river located in an industrial area was compared through the use of a river die-away biodegradation test. The change in the bacterial community during the biodegradation process was also investigated using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments and multidimensional scaling (MDS) analysis of banding patterns in DGGE gel. The bacterial community structure of biofilm formed on ceramic slides submerged in natural river water were similar to those formed on natural stones in the river bed, that is, ceramic is a more suitable material for forming natural biofilm than glass or polycarbonate. Biodegradation of aniline-derived compounds revealed that aniline was easily biodegraded by both planktonic and biofilm communities. N-methylaniline, a difficult compound to biodegrade, could not be biodegraded by planktonic bacterial cells, although biofilm communities could biodegrade this compound within 7 days. The banding pattern in DGGE gel showed that one dominant bacterium appeared during biodegradation of aniline and the bacterial community was disturbed by the addition of chemicals, although bacteria formed a relatively stable community after biodegradation was completed. DGGE of PCR-amplified 16S rDNA fragments and MDS analysis of banding patterns in DGGE gel are available for monitoring bacterial populations in the biodegradation test system. These results should be useful to improve the river die-away biodegradation test.