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Abstract:
In addition to primary production, consideration of heterotrophic decomposition processes is
extremely important for the understanding of the interrelationships in aquatic ecosystems. From fresh water bodies two major groups of heterotrophic microorganisms can be isolated. Knowledge of the spatial and temporal distribution, as well as the activities of these organisms, is very important for the understanding of lake ecosystems. Therefore 276 isolates of heterotrophic
bacteria, i. e. 105 oligocarbophilic (KAZ-strains) and 171 saprophytic (CPS-strains) were isolated
from the Plußsee from seven different depths. 213 morphological, physiological and biochemical
characteristics were investigated and then subjected to cluster analysis
("complete linkage
clustering"). The use of a multiwell
dispenser in conjunction with an automatic multipoint
inoculator allowed recognition of the individual diagnostic characteristics to be performed more
rapidly and cheaply than by conventional methods.
91% of the isolates (251 strains) were grouped in 54 clusters at a similarity level of > 80 %. There
are obvious differences in both the population composition and abundance of the two groups of the
microflora (CPS- and KAZ-isolates). Strains of both groups often occur in different clusters. In
addition the composition of the bacterial populations differs at different depths (in particular
between epilimnetic and metalimnetic isolates). On the other hand some bacteria, although isolated
from different depths, constitute a single group.
It can be concluded that in addition to a nucleus of strains present at all depths, some specialized
components occur only under specific environmental conditions (at specific depths). Significant
qualitative changes in the bacterial community occur with position and nutrient availability in the
Plußsee.
The complete results will be published elsewhere.
