A bacterial model system (Pseudomonas putida DSM 50026) was used in this research to assess potential effect of five selected chemically diverse environmental pollutants on cell membranes. Long chain fatty acid profiles of cultures exposed to environmentally relevant concentrations of atrazine (ATR), metolachlor (MET), pentachlorobiphenyl (PCB), hexachlorobenzene (HCB) and fluoranthene (FL), were analyzed and compared to non-exposed cultures. To assess sensitivity of membrane-based responses, the impact of each toxicant on culture growth was also followed spectrophotometrically. Results revealed changes in fatty acid profiles when cells were exposed to PCB, HCB and FL in concentrations below the inhibitory levels. Moreover, the observed membrane responses were similar to the ones previously associated with adaptation to some membrane-active compounds. On the other hand, exposure of cells to any of the two herbicides, ATR or MET, did not induce any significant changes in fatty acid profiles. However, when combined with a commonly used fertilizer compound, NH4NO3 growth impairment was observed. Synergistic effect of the two herbicides with NH4NO3 might be a consequence of changes in fatty acid profile increasing membrane fluidity, likely induced by NH4+ ions.