Measurement of Proteolysis in Natural Water as an Approach to the Study of Natural Cycling and Pollution Impact

摘要

Studies were conducted using a spectrophotometric assay that utilizes a particulate chromogenic protein to detect and follow proteolytic activity of natural mixed bacterial populations from lake water. Seasonal changes in proteolytic rates were found to be related to lake turnover, algal blooms, and are dependent on the dominant proteolytic bacterium. In addition, temperature, but not pH changes, leads to changes in proteolytic rates. Addition of 100 micrograms per liter of orthophosphate leads to an increase in proteolytic rates by 54 percent, while the addition of metal cofactors leads to variable increases (about 5 percent) in rates when compared to control flasks. The addition of chemical contaminants generally leads to a reduction in the rate of proteolysis. Toxic heavy metals were also inhibitory. Recognition of the sensitivity of the assay to varying levels of added orthophosphate led to the development of a procedure for assessment of trophic state of freshwater ecosystems. Preliminary data demonstrate a reasonable correlation between biologically available phosphorus and trophic state.