Pronounced seasonal dynamics of freshwater chitinase genes and chitin processing

Authors

  • Sara Beier,

    1. Department of Ecology and Genetics, Limnology, Uppsala University, Norbyv. 18D, SE-75236, Uppsala, Sweden
    2. UPMC Univ. Paris 06, UMR 7621, LOMIC, Observatoire Océanologique, F-66650 Banyuls sur mer, France
    3. CNRS, UMR 7621, LOMIC, Observatoire Océanologique, F-66650 Banyuls sur mer, France
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  • Vani Mohit,

    1. Department of Ecology and Genetics, Limnology, Uppsala University, Norbyv. 18D, SE-75236, Uppsala, Sweden
    2. Département de Biologie, Québec-Océan and Institut de biologie integrative et des systèmes, Université Laval, Québec (QC), Canada
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  • Thijs J. G. Ettema,

    1. Department of Molecular Evolution, Biomedical Center, Uppsala University, Box 596, SE-75123, Uppsala, Sweden
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  • Örjan Östman,

    1. Department of Ecology and Genetics, Division of Population & Conservation Biology, Uppsala University, Norbyv. 18D, SE-75236, Uppsala, Sweden
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  • Lars J. Tranvik,

    1. Department of Ecology and Genetics, Limnology, Uppsala University, Norbyv. 18D, SE-75236, Uppsala, Sweden
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  • Stefan Bertilsson

    Corresponding author
    1. Department of Ecology and Genetics, Limnology, Uppsala University, Norbyv. 18D, SE-75236, Uppsala, Sweden
      E-mail stebe@ebc.uu.se; Tel. (+46) 18 4712712; Fax (+46) 18 531134.
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E-mail stebe@ebc.uu.se; Tel. (+46) 18 4712712; Fax (+46) 18 531134.

Summary

Seasonal variation in activity of enzymes involved in polymer degradation, including chitinases, has been observed previously in freshwater environments. However, it is not known whether the seasonal dynamics are due to shifts in the activity of bacteria already present, or shifts in community structure towards emergence or disappearance of chitinolytic organisms. We traced seasonal shifts in the chitinase gene assemblage in a temperate lake and linked these communities to variation in chitinase activity. Chitinase genes from 20 samples collected over a full yearly cycle were characterized by pyrosequencing. Pronounced temporal shifts in composition of the chitinase gene pool (beta diversity) occurred along with distinct shifts in richness (alpha diversity) as well as chitin processing. Changes in the chitinase gene pool correlated mainly with temperature, abundance of crustacean zooplankton and phytoplankton blooms. Also changes in the physical structure of the lake, e.g. stratification and mixing were associated with changes in the chitinolytic community, while differences were minor between surface and suboxic hypolimnetic water. The lake characteristics influencing the chitinolytic community are all linked to changes in organic particles and we suggest that seasonal changes in particle quality and availability foster microbial communities adapted to efficiently degrade them.

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