The Broad Spectrum Inhibitory Effect Study of 3 Rare Earth Salts Used for Microbial Inoculant Additive

Three rare earth salts: La(NO3)3, LaCl3 and Ce(NO3)3 were used to study their broad spectrum inhibitory effect on micro-organisms to look for an effective additive for microbial inoculant. YMA solid media containing different concentrations of RE 3+ (200, 400, 600, 800, 1000 mg L-1) were exposed to air and been smeared soil solution, respectively, for contamination study. Results indicating that for air microbes, the inhibitory effect on microbe number of the 3 rare earths was Ce(NO3)3 > LaCl3 > La(NO3)3, and for soil microbes, it was La(NO3)3 > Ce(NO3)3 > LaCl3. On the whole, microbe diameters decreased as RE 3+ concentration increase, except that mass microbes occurred in high density. Actinomycetes were the most sensitive microbes to RE3+ stress, which could be inhibited at low RE 3+ concentrations (200 and 400 mg L-1), followed by bacteria and mould.