Bacterial Flora of the Biofilm Formed on the Submerged Surface of the Reed Phragmites australis

Abstract

Bacterial flora of a biofilm formed on the submerged stems of reeds (Phragmites australis) was studied in comparison with the flora in the water surrounding the reeds and on the aerial stems of the reeds. Most of the isolates from the above three samples were Gram-negative (90%) and rod-shaped (87%) with a distinct difference in glucose metabolism: largely oxidative (aerial stem surface), less oxidative (biofilm) and not at all (water). Most of the isolates (90%) belonged to the α, β, and γ-Proteobacteria, with Sphingomonadaceae a common group. Isolates from the aerial stem were phylogenetically different from those of the biofilm and water. The biofilm and water samples consisted of a phylogenetically common and a different group. The biofilm was characterized by 1) a seasonal change in thickness with a maximum in spring and a minimum in winter, 2) the existence of plastic-degrading strains phylogenetically close to Roseateles depolymerans, and 3) strong denitrifying activity even under aerobic conditions in a thicker biofilm formed in spring.