A Gram-negative bacterium was isolated from corn root. This isolate is ellipsoidal to rod-shaped and slightly curved. The size of bacterium is 0.6 x (1 - 4) nm and occurring singly, in pairs or in chains. The isolated strain reduces nitrate, oxidizes ethanol to acetic acid, and hydrolyses starch and cellulose. The maximum amylase and Cellulase activities are 20 and 5.5 u ml(-1), respectively. In addition, the isolate fixes nitrogen and has a good growth on the media without any nitrogen sources. A nitrogen fixation negative strain (Nif(-)) was obtained from the isolate by UV mutation. This mutant strain Nif(-) dose not grow on the media without nitrogen sources, but it has cellulase activities. (C) 2003 Elsevier Ltd. All rights reserved.