Building a domain ontology usually requires several resources of different types, e.g. thesaurus, object taxonomies, terminologies, data\-bases, sets of documents, etc. where objects are described in terms of attributes and relations with other objects. One important and hard problem is to be able to combine and merge knowledge units extracted from these different resources within the representation formalism supporting the ontology. The purpose of this paper is to show which kinds of resources can be taken as starting points for building an ontology, using FCA and its extension RCA. A real-world example in microbiology is proposed, detailing the interaction with domain experts during the ontology design process. Finally, an evaluation based on recall and precision gives an idea of the efficiency of the approach and points out several research perspectives.