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Seasonal Variability of Cultivable Nitrate-Reducing and Denitrifying Bacteria and Functional Gene Copy Number in Fresh Water Lake

Böllmann, Jörg, Martienssen, Marion·2024·Microorganisms
DOI 10.3390/microorganisms12030511PMC PMC10974893
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Abstract

This study describes the seasonal course of denitrifying and nitrate-reducing bacteria in a dimictic mesotrophic lake (Lake Scharmützelsee, Brandenburg, Germany) within a three-year period from 2011 to 2013. The bacterial cell numbers were quantified by the fluorescence microscopy, most probable number (MPN) and PCR-dependent quantification of the chromosomal 16S rDNA and of the nirS and nirK gene copy number. The highest seasonal differences (up to three orders of magnitudes) have been measured using MPN in the epilimnion. This variation was not reflected by PCR-dependent approaches or direct microscopical enumeration. At adverse conditions (low temperature and/or low nitrate concentrations), the differences between MPN and gene copy numbers increased by up to five orders of magnitudes and decreased to one magnitude at favourable environmental conditions. These results can be explained best by an increasing ratio of viable but not cultivable (VBNC) cells or dead cells at impairing conditions. In the hypolimnion, the courses of MPN and nir gene copy numbers were similar. This can be explained by a higher feeding pressure and therefore smaller amounts of dormant cells. In the pelagial in general, the total cell numbers enumerated by either microscopical or molecular approaches were similar. In the sediment, more than 99% of the DNA was obviously not related to viable bacteria but was rather DNA in dead cells or adsorbed to particle surfaces.

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  • The winter maxima of N-NH3 and DIN indicate possible decreased microbial activity and slower nitrification processes.

    “indicating possible decreased microbial activity and slower nitri fi cation processes (Klymenko et al. 2018; Böllmann & Martienssen 2024).”

    From A study of surface water quality using organic pollution indices: Comparative characteristics and educational opportunities (2025) · cites this paper as Böllmann & Martienssen 2024

    Section 2.1 reports a winter maximum for nitrate, and Discussion §4.2 reports fewer cultivable nitrate-reducing bacteria in the cold epilimnion. The paper does not establish winter maxima for N-NH3 or DIN, or link those maxima to slower nitrification; it studies nitrate reducers and denitrifiers rather than measuring seasonal nitrification rates. Page numbers were not supplied in our copy. (LLM, conf=0.83)

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Authors
Böllmann, J., & Martienssen, M.
Affiliations
Chair of Biotechnology for Water Treatment, Brandenburg Technical University Cottbus-Senftenberg, 03044 Cottbus, Germany
ORCID
Böllmann, Jörg
Venue
Microorganisms
Publisher
MDPI AG
Published
2024-03-02
Volume
12
Issue
3
Pages
511
ISSN
2076-2607
DOI
10.3390/microorganisms12030511
PMC
PMC10974893
Cited by
3
References
0
Language
en
Licence
creativecommons.org/licenses/by/4.0/ (vor)
Funders
  • German Federal Ministry of Education and Research (Fkz. 033L041D)
  • Brandenburgische Technische Universität Cottbus-Senftenberg, Germany (Fkz. 033L041D)

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