[14C] Acetate incorporation,an indicator of lipid biosynthesis within intact river biofilms

A method is described which enables lipid biosynthesis to be determined within intact river biofilms. Significantly different rates of biosynthesis were detected in rivers of differing nutrient availability and during different seasons. Rapid changes in microbial physiology could be detected within 24 hours. The technique appeared to be well suited to investigation of factors affecting lipid biosynthesis within biofilms. Although in contrast, acetate incorporation did not correlate with microcalorimetric total activity measurements over a 12-month period, and so the method did not appear suitable for determining total metabolic activity. However, microbial lipid biosynthesis produces a valuable food resource for the ecosystems higher tropic levels and thus the acetate incorporation technique could prove useful as an indicator of aspects of aquatic ecosystem health.