Abstract: In this paper, the effect of methionine(Met) and lysine(Lys), two typical root exudates from Eichhrmnia crassipes, on the degradation phenol by its rhbopheric Enterobacter sp. F₂ is studied. Met, an attractant, doeS not affect the growth, enzyme activity and phenol-degrading efficiency of F₂, but Lys, a negative chemotaxic amino acid, call inhibit them under high concentrations (10^-2 or 10^-3mol·L^-1 ), and the inhibition effect is weackened progressively with its decreasing concentration. Amino acids in root exudates from Eichhornia crassipes act as partial information flows of its rhizospheric micrxiystem and affect phenol-degrading efficiency of the system.

Key words: Eichhornia crassipes, Root exudates, Amino acids, Enterobacter sp.F₂, Phenoldegrading efficiency, water source, community, hydrogen and oxygen isotopes, Beijing mountainous area