Abstract
The effects of UV-B radiation on the heterotrophic nanoflagellate Bodo saltans (Kinetoplastida) were examined under controlled conditions with artificial UV sources and also under natural solar radiation in an oligotrophic lake. In both types of experiments, the characteristic elongated cell morphology of this flagellate changed into a spherical one. This effect was due to UV-B but also to UV-A radiation, and after 4 h of exposure at 0.5 m of depth, 99% (UV-B plus UV-A plus photosynthetically active radiation) and 69% of the cells (UV-A plus photosynthetically active radiation) were spherical. At 6 m of depth where only 10% of the UV-B (305 nm) at the surface was measured, no significant effect was observed. The spherical cells were nonmotile, but before the morphological change took place, the swimming speed was ca. 3.5 times lower in the plus-UV-B treatment. The negative relation between the abundance of spherical cells and the average ingestion of fluorescently labeled bacteria per cell indicates that these cells are not able to feed upon bacteria. In bacterivory experiments lasting for 6 h, the total number of grazed bacteria was up to 70% lower in the plus-UV-B treatment than in the control without UV-B. This resulted in a positive feedback between UV-B and bacterial growth. The high sensitivity of B. saltans to solar UV-B and UV-A radiation strongly reduces its ability to live near the surface at times of high UV radiation.
Full Text
The Full Text of this article is available as a PDF (226.0 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Lim E. L., Amaral L. A., Caron D. A., DeLong E. F. Application of rRNA-based probes for observing marine nanoplanktonic protists. Appl Environ Microbiol. 1993 May;59(5):1647–1655. doi: 10.1128/aem.59.5.1647-1655.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sancar A. Structure and function of DNA photolyase. Biochemistry. 1994 Jan 11;33(1):2–9. doi: 10.1021/bi00167a001. [DOI] [PubMed] [Google Scholar]
- Sommaruga R., Psenner R. Permanent presence of grazing-resistant bacteria in a hypertrophic lake. Appl Environ Microbiol. 1995 Sep;61(9):3457–3459. doi: 10.1128/aem.61.9.3457-3459.1995. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vrba J., Simek K., Nedoma J., Hartman P. 4-Methylumbelliferyl-beta-N-Acetylglucosaminide Hydrolysis by a High-Affinity Enzyme, a Putative Marker of Protozoan Bacterivory. Appl Environ Microbiol. 1993 Sep;59(9):3091–3101. doi: 10.1128/aem.59.9.3091-3101.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]