Chemosensory Responses of Heterotrophic and Mixotrophic Flagellates to Potential Food Sources
Abstract:Chemosensory responses by freshwater heterotrophic and mixotrophic microflagellates to amino acids, bacteria and bacterial exudates were measured using the Van Houten T-maze assay. Positive responses by Monas sp. 1 were demonstrated to 0.1 M CasAmino acids within 30 min. Bacteria resuspended in sterile water elicited no response from Monas sp. 1 after 30 min, but a positive response was observed after 90 min. Monas sp. 2 also showed a positive chemosensory response to the presence of bacteria after 90 min. Strongest positive responses by Monas sp. 2 were to bacterial exudates with or without cells present. These data suggest that heterotrophic flagellates may be attracted to areas of high bacterial densities by chemical cues present in bacterial exudates. The Van Houten T-maze tests also indicated a strong positive response to a toxic bacterium, Chromobacterium violaceum. This may be due to the death and deposition of cells upon entry in the T-maze arm with the toxins. The pigmented mixotroph, Poterioochromonas showed no response to bacteria with or without exudates after 90 min, and a negative response after 24 h. Phytoflagellates may avoid bacteria as potential competitors for nutrients. Alternatively, the arm containing bacteria could have become chemically inhospitable after 24 h and the flagellates were responding to an adverse chemical stimulus.
Document Type: Research Article
Publication date: November 1, 1988
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