Use of the 5-cyano-2,3-ditolyl tetrazolium chloride reduction test to assess respiring marine bacteria and grazing effects by flow cytometry during linear alkylbenzene sulfonate degradation

Abstract

Viable, total and metabolically active bacteria were determined during linear alkylbenzene sulfonate degradation in coastal seawater. Viable bacteria were estimated by plate counts on marine agar media while the total and metabolically active bacteria were determined with the nucleic acid stain SYTO-13 and the tetrazolium salt 5-cyano-2,3-ditolyl tetrazolium chloride, respectively, in double stain procedures analyzed by flow cytometry. The double stain SYTO-13/5-cyano-2,3-ditolyl tetrazolium chloride is a rapid and simple method that discriminates bacterioplankton populations according to nucleic acid content and formazan formation. Linear alkylbenzene sulfonate degradation was monitored by high-performance liquid chromatography analysis. Bacterioplankton degraded linear alkylbenzene sulfonate by growing to communities with a high percentage of viable and metabolically active bacteria. The bacteria produced were rapidly grazed by protozoa; however, the grazing took place mostly on metabolically active cells, which were larger than the rest of the population.