Mm. Sala et H. Gude, Role of protozoans on the microbial ectoenzymatic activity during the degradation of macrophytes, AQUAT MIC E, 20(1), 1999, pp. 75-82
A succession of microbial populations and ectoenzymatic activities was obse
rved during the decomposition of the dissolved organic matter (DOM) leached
from the macrophyte Potamogeton pectinatus. In an initial phase, free bact
erial populations dominated. These bacteria produced ectoenzymes to hydroly
ze dissolved carbohydrates (maltose, cellobiose and starch). When bacterivo
rous Protozoa entered the sample, free bacteria almost disappeared and most
of the bacteria were then found attached. colonizing the macrophyte partic
les. Protozoan populations also showed a succession where heterotrophic nan
oflagellates (HNF) grew first and then larger Protozoa, ciliates and amoeba
, developed. During this second phase, high activities of degradation of st
ructural polysaccharides such as cellulose and hemicellulose were detected.
HNF seemed to play an important role during the degradation of macrophytes
because they grazed mainly on free bacteria and left the attached bacteria
to grow. Thus, they promoted a shift from the hydrolysis of non-structural
to structural polysaccharides.