Carbonfixation, -incorporation and -transfer in the chemoautotrophic Zoothamnium niveum symbioses with 14 C bicarbonat autoradiography
Christian Rinke
Art der Arbeit
Universität Wien
Formal- und Naturwissenschaftliche Fakultät
Monika Bright
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The very large and fast growing sessile, colonial ciliate <i>Zoothamnium niveum</i>(Ciliophora, Oligohymenophora) inhabits peat surfaces of mangrove islands in the lagoonal regions of the Belize Barrier Reef. A coat of bacteria covers the host obligatorily. First indications of a nutritional relationship came from observations of life specimens that ingested bacteria identical to their own symbionts and from ultrathin sections with similar bacteria in food vacuoles in the process of degradation. The aims of this study were to investigate with <sup>14</sup>C bicarbonate tissue autoradiography under which conditions and time frames the autotrophic symbionts are capable of carbon fixation and incorporation and by which means transfer of fixed carbon from the symbionts to the host occurs. The results indicate that the symbionts are able to fix inorganic carbon and incorporate organic carbon incubated in normoxic, thiosulfatic and sulfidic seawater. Incubations in seawater without added sulfur species are hypothesized to be due to the use of elemental sulfur stored in the symbionts and are in accordance with Cartesian diver experiments that demonstrated the oxidation of elemental sulfur within a few hours incubation time. The two bacterial morphotypes, cocci and rods were incorporating different amounts of organic carbon per cell. This difference is explained by the dissimilar sulfide and oxygen supply caused by behavior and morphology of the host. Transfer of fixed carbon from the symbionts to the host occurs via digestion of the symbionts and via uptake of low molecular release from the symbionts. While fast bacterial release is seen already after 15 min of pulse labeling, the slower digestional process is seen in the increase of label over host tissue between 3 hour pulse and 24 hour chase periods. Translocation of digested nutrients from the feeding microzooids to the non-feeding other parts of the colony, such as macrozooids, stalk, and branches occurred fast, since label over all parts of the host was detected simultaneously. This transfer is hypothesized to occur via cytoplasmic connections. Our experiment clearly point to a tight nutritional relationship between a thiotrophic ectosymbiont and <i>Z. niveum</i>. The host is capable to uptake symbionts release of organic carbon and to ingest its own symbionts, but at the same time, most likely also consumes free-living bacteria from the surrounding water. The specific contribution of the symbionts to the host´s diet still remains to be determined.


symbioses <i>Zoothamnium niveum</i> <sup>14<7sup>C bicarbonate autoradiography thiotrophic bacteria carbonfixaton carbon incorporation carbon transfer
Christian Rinke
Haupttitel (Englisch)
Carbonfixation, -incorporation and -transfer in the chemoautotrophic Zoothamnium niveum symbioses with 14 C bicarbonat autoradiography
Paralleltitel (Deutsch)
Kohlenstofffixierung, -inkorporation und -transfer in der chemoautotrophen Zoothamnium niveum Symbiose mit 14 C Bikarbonat Autoradiographie
44 Bl. : Ill., graph. Darst.
Monika Bright
42 Biologie > 42.30 Mikrobiologie ,
42 Biologie > 42.60 Zoologie: Allgemeines ,
42 Biologie > 42.70 Protozoa ,
42 Biologie > 42.94 Meeresbiologie
AC Nummer
Utheses ID
UA | 439 | | |
Universität Wien, Universitätsbibliothek, 1010 Wien, Universitätsring 1