Muramic Acid Measurements for Bacterial Investigations in Marine Environments by High-Pressure Liquid Chromatography

Muramic acid, a constituent of procaryotic cell walls, was assayed by high-pressure liquid chromatography in samples from several marine environments (water column, surface microlayer, and sediment) and a bacterial culture. It is used as a microbial biomass indicator. The method gave a good separation of muramic acid from interfering compounds with satisfactory reproducibility. A pseudomonad culture had a muramic acid content of 4.7 x 10 to 5.3 x 10 mug per cell during growth. In natural water samples, highly significant relationships were found between muramic acid concentrations and bacterial numbers for populations of 10 to 10 cells per liter. The muramic acid content in natural marine water decreased from 5.3 x 10 to 1.6 x 10 mug per cell with increasing depth. In coastal sediments exposed to sewage pollution, concentrations of muramic acid, ATP, organic carbon, and total amino acids displayed a parallel decrease with increasing distance from the sewage outlet. Advantages of muramic acid measurement by high-pressure liquid chromatography are its high sensitivity and reduction of preparation steps, allowing a short time analysis.