This micro-level study explores the extent that citation analysis provides an accurate and representative assessment of the use and impact of bioinformatics e-research infrastructure. The bioinformatic e-research infrastructure studied offers common tools used by life scientists to analyse and interpret genetic and protein sequence information. These e-resources therefore provide an interesting example with which to explore how representative citations are as acknowledgements of knowledge in the life sciences. The examples presented here suggest that there is a relation between number of visits to these databases and number of citations; however, a parallel finding shows how citation analysis frequently underestimates acknowledged use of the resources offered on this e-research infrastructure. The paper discusses the implications of the findings for various aspects of impact measurement and also considers how appropriate citation analysis is as a measurement of knowledge claims.