Mesorhizobium mediterraneum

Name of bacteria: Mesorhizobium mediterraneum
The picture is obtained by epi-fluorescence microscopy of a root nodule suspension. 

Method: immunofluorescence. The green color of bacteria is obtained by reaction with fluorescent specific antibodies labeled with the fluorescein Isothiocyanate (FITC).

Ecological role: The bacteria are present in the soil and form symbiotic  associations (nodules) with plants of the family Leguminosae. In the nodules, the bacteria are able to transform the Nitrogen gas from the atmosphere (N₂) into the  compound NH₄⁺, that can be used from the plants (biological Nitrogen fixation).