We studied the relationships of nitrogen dioxide atmospheric pollution and metal trace elements contained in atmospheric particles which were accumulated in Bryophytes to microbial communities of Bryophytes at 3 differently polluted sites in France (rural, urban and industrial) over an 8-month period. We used the following methods. Metal trace elements in mosses were analyzed by instrumental neutron activation (INAA) and by inductively coupled plasma mass spectrometry (ICP-MS) by the CEA. The temperature, relative humidity, but also wind speeds and the levels of NO2 were measured. The microbial communities were extracted from the terrestrial mosses (Scleropodium purum) and the biomass of the testate amoebae was determined. We obtained the following results. The biomass of testate amoebae was significantly higher at the rural site than at the urban and industrial sites (p=0.0008) at the end of this study. After 8 months of exposure, Assulina muscorum and Bullinularia indica had disappeared from the industrial site. At the urban site, the testate Difflugia genus had disappeared. The Redundancy Analysis (RDA) showed that the physico-chemical variables ([NO2], relative humidity and temperature) and the trace elements which were accumulated in Bryophytes ([Cu], [Sr]) explained 51.3% of the variance in the testate amoebae community data. We reach the following conclusions. The results of this study suggest that testate amoebae could be a good bioindicator of atmospheric pollution (NO2 and PM10) and could be used for ecological biomonitoring. However, other variables such as other atmospheric pollutants (PAH, VOC,...) also influence the structure of this testate amoebae community.