Comparison of Gram-staining and alternate methods, KOH test and aminopeptidase activity in aquatic bacteria: their application to numerical taxonomy

A miniaturized method for Gram-staining using a microtiter system introduced. Compared with other methods this procedure is more rapid and precise. A total of 466 aerobic bacterial isolates (82.6% Gram-negative, 12.7% Gram-positive and 4.7% Gram-variable) from a eutrophic lake were examined with the KOH test and for aminopeptidase (AP) activity. A complete correlation between the KOH test and Gram-reaction was not observed; this was also the case between Gram-reaction and AP activity. Almost all (91.4%) of the Gram-negative isolates were disintegrated with a 3% KOH solution, while the correlation between Gram-positive staining and a negative KOH reaction was somewhat less (88%). All Gram-variables were KOH negative. Additionally, 76.2% of the Gram-negative showed AP activity, whereas 44.1% of the Gram-positive, and 54.5% of the Gram-variable were AP negative when grown on casein-peptone-starch agar (CPS). Of the naturally occurring Gram-negative strains, 73% were both AP positive and KOH positive; only 42.4% of the Gram-positive strains were AP and KOH negative. Therefore, it is proposed to employ treatment with KOH and hydrolysis of l-alanine-4-nitroanalide as an additional taxonomic criterion for classifying naturally occurring aquatic populations. These methods should not replace the Gram-staining

Characterization of bacterial populations in a Baltic lake by microtitertechnique and numerical taxonomy

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

On the structure of bacterial communities in a Central European open grassland stream, the Breitenbach

As a part of the bacteriological investigations on the Breitenbach, a small central European stream, strains were isolated from different sites along the brook and, for comparison, from the surrounding meadow soil, to obtain a first impression of the bacterial community composition. Physiological-biochemical features were determined by the rapid microtechniques established by Moaledj (1984). These data, together with colony and cell morphological features, were used for numerical taxonomic analysis