Abstract: The invention relates to a method for the extraction of nucleic acids from microorganisms and to the use thereof in a method for the analysis of a microbial population in a given environment, e.g. a population of microorganisms taken from the air. In particular, the invention relates to an extraction method in which the following three lysis steps are performed successively in any order, namely: (i) chemical lysis of the microorganisms, consisting in bringing the microorganisms into contact with a lysis solution containing a detergent; (ii) thermal shock lysis comprising the incubation of the extract at a temperature lower than 0° C., immediately followed by the incubation of the extract at a temperature of at least 95° C. and preferably 100° C.; and mechanical lysis in which the extract is stirred in the presence of balls.