Effect of light regimes on the utilisation of an exogenous carbon source by freshwater biofilm bacterial communities
This study reports the novel use of nucleic acid stable isotope probing (NA-SIP) to identify metabolically active ([13C]-acetate assimilating) bacteria in freshwater biofilms. Currently, a little is known of the factors affecting the structure and activity of these complex microbial biofilm communities, although it is likely that they are influenced by riparian vegetation through attenuation of light and alteration of allochthonous inputs of carbon. NA-SIP was used to investigate the effect of varying light regimes on [13C]-acetate assimilating bacteria within laboratory biofilm microcosms. Differences in clone libraries of 16S rRNA and rRNA genes from 13C-labelled and unlabelled nucleic acids indicated differential uptake of acetate and the rapid transfer of 13C to organisms at a higher trophic level. Biofilm communities incubated in the dark changed least over time and retained a significant fraction of phototrophic organisms. Incubation under elevated light caused the greatest change in bacterial community structure. Contrary to expectation, a complete loss of chlorophyll containing organisms occurred within this treatment, challenging current thinking that elevated light promotes communities dominated by photoautotrophs in nutrient enriched environments.
Keywords[13C]-acetate Carbon Photoinhibition Stable isotope probing Stream biofilms Bacteria
This work was funded by the Foundation for Research, Science and Technology, New Zealand (Grant No. UA0X306).
- Franklin L, Forster R (1997) The changing irradiance environment: consequences for marine macrophyte physiology, productivity and ecology. Eur J Phycol 32:207–232Google Scholar
- Jackson CR, Churchill PF, Roden EE (2001) Successional changes in bacterial assemblage structure during epilithic biofilm development. Ecology 82:555–566Google Scholar
- Jeffrey SW, Humphrey GF (1975) New spectrophotometric equations for determining chlorophylls a, b, c1 and c2 in higher plants, algae, and natural phytoplankton. Biochem Physiol Pflanz 167:191–194Google Scholar
- Kovach W (1999) MVSP—a multivariate statistical package for windows, ver. 3.1. Kovach Computing Services, PenreathGoogle Scholar
- Lane D (1991) 16S/23S rRNA sequencing. In: Stackebrandt E, Goodfellow M (eds) Nucleic acid techniques in bacterial systematics. Wiley, New York, pp 115–175Google Scholar
- Ramasamy P, Zhang X (2005) Effects of shear stress on the secretion of extracellular polymeric substances in biofilms. Water Sci Technol 52:217–223Google Scholar
- Romani AM, Sabater S (2000) Influence of algal biomass on extracellular enzyme activity in river biofilms. Microbiol Ecol 41:16–24Google Scholar
- Segers P, Vancanneyt M, Pot B, Torck U, Hoste B, Dewettinck D, Falsen E, Kersters K, De Vos P (1994) Classification of Pseudomonas diminuta Leifson and Hugh 1954 and Pseudomonas vesicularis Busing, Doll, and Freytag 1953 in Brevundimonas gen. nov. as Brevundimonas diminuta comb. nov. and Brevundimonas vesicularis comb. nov., respectively. Int J Syst Bacteriol 44:499–510PubMedCrossRefGoogle Scholar
- Spring S, Kampfer P, Ludwig W, Schleifer KH (1996) Polyphasic characterization of the genus Leptothrix: new descriptions of Leptothrix mobilis sp. nov. and Leptothrix discophora sp. nov. nom rev and emended description of Leptothrix cholodnii emend. Syst Appl Microbiol 19:634–643Google Scholar
- Sterman NT (1988) Spectrophotometric and fluorometric chlorophyll analysis. In: Lobban CS, Chapman DJ, Kremer BP (eds) Experimental phycology—a laboratory manual. Cambridge University Press, Cambridge, pp 35–46Google Scholar