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2 Polish Journal of Ecology

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Impact of humic substances on bacterioplankton in eutrophic lake

Burkowska Aleksandra, Donderski Wojciech

Polish Journal of Ecology

2007

Vol. 55, nr 1

155-160

This paper presents the results of resarch on impact of humic substances (HS) on bacterioplancton in eutrophic Lake Jeziorak (north-eastern Poland). In cultures of natural bacteria from the lake water, enriched with 0, 5, 10, 25 and 50 mg dm[^-3] of HS (natural HS - isolated from lake water or commercial HS - sodium salt of humic substance; Sigma-Aldrich), were determined the following parameters: total number of bacteria (TNB), number of heterotrophic bacteria (CFU), bacterial production (BP) (measured with [[3]H]methyl thymidine method) and general activity of esterases. Natural HS had a more positive impact on bacterial growth, bacterial production and activity of esterases than the commercial preparation HS. The highest TNB and CFU was observed when the water was enriched with 25 mg dm[^-3] of natural HS. Ali concentrations of the natural HS stimulated bacterial production. The activity of hydrolytic enzymes increased with rising concentrations of natural HS.

Chitinolytic bacteria in two lakes of different trophic status

Swiontek-Brzezinska Maria, Donderski Wojciech

Polish Journal of Ecology

2006

Vol. 54, nr 2

295-301

This paper presents the results of research on the number of chitinolytic bacteria and chitinolytic activity of strains in the oligo-mesotrophic and the eutrophic lakes. Two lakes of soft and hard water and of different trophic status (in terms of nutrients contents) from Iławskie Lake District (North Poland) were choosen. The numbers of chitinolytic bacteria were higher in eutrophic lake (average 1.0 x 10^3 cells cm^-3) than in oligo-mesotrophic lake (average 0.5 x 10^3 cells cm^-3) as well as in littoral versus pelagic zone. However, a higher percentage of chitinolytic bacteria (average 13%) among the total numbers of heterotrophic bacteria was found in oligo-mesotrophic lake as well as higher rate of the chitinolytic activity of bacteria (7.0 versus 4.5 nmol GlcNAc mg^-1 protein h^-1 after 6 days of incubation). The possible shortage of dissolved organic compounds in mesotrophic lake was pointed up as the reason for using the dissolved chitin as the source of carbon and nitrogen. Enterobacter aerogenes (28%), Aeromonas sp. (25%) and Chromobacterium sp. (16%) dominated in oligo-mesotrophic lake. In eutrophic lake, the most numerous species were Aeromonas hydrophila (46%) and Aeromonas sp. (15%).