Bacterial biovolume and biomass estimations

The biomass of bacterial populations in aquatic ecosystems is often estimated by measuring bacterial biovolume and converting this into biomass in terms of carbon. A reliable conversion factor relating the measured bacterial biovolume to bacterial carbon content is essential for this approach. Based on direct measurements of bacterial cell carbon content, cell number, and biovolume, I have derived an average conversion factor of 5.6 x 10 g of C mum. This conversion factor is 3.4 to 6.6 times higher than most theoretically derived factors currently in use. Both bacterial biomass and bacterial production in aquatic ecosystems may thus have been seriously underestimated.