Sensitivity of the root nodule rhizobium leguminosarum to the anti-fungal dressing aldrex T

Abstract

Induction of inhibited growth halo, around filter paper discs or groundnut seeds dusted with aldrex T, diameter of which consistently increased with dressing application rate, was exhibited by the root nodule bacteriumRhizobium leguminosarum. Some cells sensitive to aldrex T gained recovery upon transference to fresh media denoting a bacteriostatic effect of the anti-fungal dressing.

The viable bacterial cells steadily declined with fungicide concentrations between 100 and 500 p.p.m. An increase of 130% in viable colony count was recorded when the dose was increased to 700 p.p.m., and a relatively similar increase at 900 p.p.m., thus exhibiting a zone of inverted growth at 500 p.p.m. which was also confirmed by the optical density test. The latter was reliable after 24h incubation when the turbidity uniformly deminished with the fungicide dose to a maximal decline at 500 p.p.m. Aldrex T decreased the log and increased the stationary phases ofR. leguminosarum growth at all test doses.

In vitro treatment ofR. leguminosarum with the fungicide exhibited some changes in bacterial morphology, cell lysis and shrinkage of cell membrane as revealed by the electron microscope.