Figure 1

Ca²⁺ measurements in M. loti cells stimulated with different physico-chemical signals. Bacteria were challenged (arrow) with: A, mechanical perturbation, represented by injection of an equal volume of culture medium (black trace) or 10 volumes of air (grey trace); B, cold shock, given by 3 volumes of ice-cold culture medium (black trace); control cells were stimulated with 3 volumes of growth medium kept at room temperature (grey trace); C, hypoosmotic stress, given by injection of 3 volumes of distilled water (black trace); salinity stress, represented by 200 mM NaCl (grey trace); D, different external Ca²⁺ concentrations. These and the following traces have been chosen to best represent the average results of at least three independent experiments.