[Different models and a certain methodological unity].

The papers included in this section were previously exposed in the Microbial Communities Symposium organized in XXXV Congreso Nacional de Microbiología. The contributions try to understand the diversity associated to different microbial communities from a molecular perspective, regardless of culture or including a cultured based perspective. Thus, natural models, including bacteria associated to insect tissues, biofilms and microbial communities in man-made habitats as oil pipelines, anaerobic digestors and fermented foods are described. The papers explain several questions and exhibit different perspectives, but maintain a methodological unit, illustrating the knowledge and applicative potential of microbial ecology from a molecular point of view.