GLYCOGEN, THE PREFERRED ENERGY-SOURCE FOR EXTRACELLULAR PROTEIN-FORMATION AND GROWTH OF AEROMONAS-SALMONICIDA

A study was made of the effect of supplementing a rich 3% (w/v) trypto ne soya broth (TSB) medium and a poorer 1.7% (w/v) tryptone-based medi um with glucose, maltose and glycogen, as carbon sources, on growth an d exoprotein formation by Aeromonas salmonicida. In TSB, glucose inhib ited growth and repressed exoprotein formation whilst maltose and glyc ogen had little effect, up to 20 h, when compared with an unsupplement ed control. By contrast, in the poorer medium, over a 24-h incubation period, growth was stimulated three-fold by glycogen, and whilst exopr otein formation was low in comparison with that observed in TSB, the g reatest production was observed in the presence of glycogen. Extracell ular alpha-amylase was measured in the tryptone medium in the presence of the three carbon sources and the highest level, produced in the pr esence of glycogen, was 1.6 times that with added maltose whilst none was detectable with glucose present. This pattern was repeated in the case of the maltose-inducible porin, LamB, of the outer membrane.