Study of biochemical and molecular properties of Sinorhizobium meliloti bacteria isolated from alfalfa roots in two regions of Iran

Rhizobia are able to fix atmospheric nitrogen and provide a significant amount of nitrogen in the soil. The purpose of this study was to isolate and identify the biochemical properties of indigenous Sinorhizobium meliloti bacteria in two regions of Iran, and also to detect the strains with higher efficiency, which have the potential to be used as bio-fertilizer. 

In this cross- sectional study, bacteria were collected from alfalfa plants in areas around Qom and Khorasan Provinces. These bacteria were identified using nodulation test, as well as biochemical and molecular examinations. The growth curves of these isolates were drawn. The isolates with higher efficiency were identified by inoculation of bacteria into alfalfa seeds and comparison of the rate of plant growth.

The isolated bacteria did not show a same reaction in Lithmus milk medium. All bacteria were gelatinase-negative, and only a few strains were able to utilize starch of the media. Some bacteria were able to grow in the presence of hydrophobic compounds. S22K and S36k from Khorasan, S3Q and S12Q from Qom showed better effects on the growth of test plants in comparison to other isolates.

The results of these research showed that some indigenous bacteria of S. meliloti are able to digest starch and were able to grow in the presence of SDS. Among the isolates, strains S3Q and S22K had the better potential for application as biological fertilizer. This research could be a step for the production of bio-fertilizers in our country.