GROWTH AND NITROGENOUS EXCRETION OF A COMMON SOIL FLAGELLATE SPUMELLA SP - A LABORATORY EXPERIMENT

The growth and nitrogenous excretion of a common soil flagellate, Spumella sp., isolated from a Scottish podzol and fed with the common soil bacterium, Pseudomonas fluorescens, were investigated. Video-enhanced light microscopy and transmission electron microscopy were used to study the digestion process. Ingestion of the bacteria occurred rapidly at the base of the two flagella and involved the formation of a small protrusion, which surrounded the prey. The first signs of digestion appeared a few minutes after ingestion with the degradation of the outer membrane of the bacteria. Digestion was complete within 30-60 min, and the indigestible bacterial residues were then released into the medium. Ammonium nitrogen was the major form of nitrogen excreted. Some apparently intact P. fluorescens bacteria were also egested. For each division 130 bacteria were required. No feeding activities were observed at 5-degrees-C. Of the total bacterial protein, 42% was incorporated into biomass of flagellates.