Extracellular, low-affinity β-N-acetylglucosaminidases linked to the dynamics of diatoms and crustaceans in freshwater systems of different trophic degree
✍ Scribed by Jaroslav Vrba; Jitka Kofroňová-Bobková; Jakob Pernthaler; Karel Simek; Miroslav Macek; Roland Psenner
- Book ID
- 102870199
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 675 KB
- Volume
- 82
- Category
- Article
- ISSN
- 1434-2944
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✦ Synopsis
Extracellular hydrolysis of 4-methyIumbell/feryl P-N-acetylglucosaminide was measured in the oligomesotrophic Piburger See and the eutrophic Rimov reservoir during spring and summer phytoplankton blooms, respectively. Total enzymatic activity (TEA) ranged between 0.2 and 19.1 nmol I-' h-' in the reservoir and between 0.8 and 12.4 nmol I-' h-' in the lake. High-affinity (K,,, < 1 p o l 1-') and lowaffinity ( K , > 100 ymol I-') enzymes were kinetically identifiable in most samples from both localities.
The low-affinity enzyme activity (LEA) usually accounted for >60% (mean: 80%) of TEA. LEA and diatom biomass significantly correlated over time in the reservoir epilimnion (rr = 0.578) and in the lake metalimnion (rs = 0.862). As diatoms possess chitin and take up its monomer, N-acetylglucosamine, two explanations of the observed relationships are suggested: extracellular P-N-acetylglucosaminidase activity partly originates either from ectoenzymes of chitinolytic bacteria attached to diatom cells or from ectoenzymes of diatoms, enabling them to take up N-acetylglucosamine from ambient amino sugars instead of synthesizing it de now. A significant positive correlation of LEA with crustacean abundance was found in the lake epilimnion (rs = 0.850). apparently reflecting the growing spring populations of frequently moulting juvenile crustaceans. A possible contribution of chitinolytic bacteria, accompanying the crustacean populations, to LEA is discussed.