The survival of a strain of Legionella pneumophila (Lp-1) inoculated in artificial water microcosms was investigated with and without an amoebal host and varying environmental conditions, such as biofilm formation, amount of nutrients and incubation temperature. The results obtained using short (micromethod) and long (macromethod) term methods showed that L. pneumophila Lp-1 dies rapidly at 4 degrees C in the macromethod assay. When the same temperature (4 degrees C) was applied to the micromethod assay, L. pneumophila Lp-1 survived for three weeks, although it progressively decreased. At an incubation temperature of 30 degrees C, the aquatic environment was more favourable and better survival emerged in the macromethod; in contrast.. this favourable temperature condition did not improve the survival of L. pneumophila Lp-1 cultured with the micromethod. The role of the protozoa Acanthamoeba polyphaga proved to be indispensable for legionella survival only when environmental conditions become unfavourable. (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.