The acquisition of knowledge about relations between bacteria and their locations (habitats and geographical locations) in short texts about bacteria, as defined in the BioNLP-ST 2013 Bacteria Biotope task, depends on the detection of co-reference links between mentions of entities of each of these three types. To our knowledge, no participant in this task has investigated this aspect of the situation. The present work specifically addresses issues raised by this situation: (i) how to detect these co-reference links and associated co-reference chains, (ii) how to use them to prepare positive and negative examples to train a supervised system for the detection of relations between entity mentions, (iii) what context around which entity mentions contributes to relation detection when co-reference chains are provided.