Bacteriological analysis of a pond water from Gobardanga, West Bengal.

The present communication deals with the bacteriological examination of a pond water, which is being used as one of the sources of drinking water, by multiple tube fermentation test to detect the coliform bacteria. The test was performed sequentially in three stages: presumptive, confirmed and completed coliform test. The results show that as the most probable number (MPN) index per 100 ml is 23, that pond water should be treated as nonpotable.

Growth behaviour and indole acetic acid (IAA) production by a Rhizobium isolated from root nodules of Alysicarpus vaginalis DC.

From the root nodules of Alysicarpus vaginalis DC, the symbiont was isolated and identified as a Rhizobium sp. The bacteria produced a high amount (107 microg/ml) of indole acetic acid (IAA) in culture from tryptophan supplemented yeast extract mannitol medium. The isolate preferred L-isomer of tryptophan for maximum IAA production. The production was maximum when the bacteria reached its stationary phase of growth. The production of IAA could be increased up to 70% over yeast extract glucose medium by supplementing ZnSO4, 7H2O (0.5 microg/ml). L-asparagine (0.2%) and sodium dodecyl sulfate (1.0 microg/ml). The possible relationship between the rhizobial IAA production and legume-rhizobia symbiosis is discussed.

Bioproduction of indoleacetic acid by a Rhizobium sp. from the root nodules of Desmodium gangeticum DC.

The Rhizobium sp. isolated from the root nodules of Desmodium gangeticum DC. produced a high amount of indole acetic acid (IAA) from tryptophan in culture. For maximum IAA production, the bacteria preferred L-isomer over DL- or D-isomer of tryptophan. The production of IAA could be increased up to 37% over yeast extract ribose medium by supplementing the medium with ZnSO4 (0.1 microgram/ml), asparagine (0.1%) and nicotinic acid (0.1 microgram/ml). The possible relationship between the rhizobial IAA production and legume-rhizobia symbiosis is discussed.