Summary
1. This review on the bacteriological research conducted on the Windermere catchment over the last 70 years addresses the significant contributions made to the understanding of freshwater microbial processes, such as nitrification, the spread of antibiotic resistance and the development of process-based ecological tools.

2. Water quality fluctuated through periods of decline and recovery. Although the general microbial community responded to lake trophic status, it is a poor indicator of change because of poor resolution and lack of long-term monitoring of Windermere’s general bacterial community.

3. Long-term monitoring has shown that bacterial faecal indicators, conversely, have not shown any significant change when comparing data from the last 13 years to those obtained in 1939. Bathing water quality continues to pass the imperative value as defined by the current Bathing Water Directive and Windermere is safe for recreation.

4. Notwithstanding, the bacterial community includes pathogens and other bacteria containing transferable antibiotic resistance genes which remain unmonitored. These have the potential for an as yet unquantified and possibly long-term impact on human health.

5. Despite increased knowledge and technological advances, a complete description of the bacterial diversity of Windermere, as with most environmental sites, remains unresolved because of technological constraints. The application of the latest technologies, such as next generation sequencing, can help measure the diversity and elucidate the possible roles of the silent majority of bacteria to overcome these constraints [Correction inserted on 24 October 2011, after first online publication. The text has changed from “measure the diversity and possible roles” to “measure the diversity and elucidate the possible roles”.].