Abstract
Introduction-Hypothesis:
In many symbiotic mutualisms, microbial symbionts provide benefits to their eukaryote host through nourishment. The giant ciliate Zoothamnium niveum lives at oxic-sulfidic / anoxic interfaces in marine shallow waters. It harbors a monolayer of sulfur oxidizing bacteria on its outer surface [1]. The aims of this study were to directly demonstrate the sulfur-oxidizing, chemoautotrophic (thiotrophic) nature of the symbionts and to investigate putative carbon transfer from the symbiont cells to the host.
Methodology:
We performed pulse-chase incubations with 14C and 13C labeled bicarbonate under varying environmental conditions. A combination of tissue autoradiography, NanoSIMS 13C/12C isotope and sulfur elemental imaging coupled with transmission electron microscopy (TEM) was used to follow the fate of the radioactive and stable isotopes of carbon, respectively.
Results:
We show that symbiont cells fix substantial amounts of inorganic carbon in the presence of sulfide, but also (to a lower degree) in the absence of sulfide by utilizing internally stored sulfur. Isotope labeling patterns suggest translocation of organic carbon to the host through release of these compounds and digestion of symbiont cells. The latter mechanism was supported by TEM - based ultracytochemical detection of acid phosphatase in host lysosomes and in food vacuoles. In addition, fluorescence in situ hybridization (FISH) revealed that the vast majority of ingested microbial cells were ectosymbionts.
Conclusions/Outlook:
Tissue autoradiography allows analysis of large sample areas with many replicates. NanoSIMS correlated with TEM on the other hand opens the window to single cell physiology with ultrastructural resolution. Rounded off by ultracytochemistry and FISH, these very complementary techniques allowed us to highlight symbiont carbon fixation and subsequent transfer to the host in this thiotrophic symbiosis, confirming the nutritional role of the association. Beyond carbon, other elements such as nitrogen may be exchanged between symbiont and host and could be investigated with a similar technical approach.
References:
[1] Bright, M., Espada-Hinojosa, S., Lagkouvardos, I., Volland, J. 2014. The giant ciliate Zoothamnium niveum and its thiotrophic epibiont Candidatus Thiobios zoothamnicoli: A model system to study interspecies cooperation. Frontiers in Microbiology, 5 art. no. 145
In many symbiotic mutualisms, microbial symbionts provide benefits to their eukaryote host through nourishment. The giant ciliate Zoothamnium niveum lives at oxic-sulfidic / anoxic interfaces in marine shallow waters. It harbors a monolayer of sulfur oxidizing bacteria on its outer surface [1]. The aims of this study were to directly demonstrate the sulfur-oxidizing, chemoautotrophic (thiotrophic) nature of the symbionts and to investigate putative carbon transfer from the symbiont cells to the host.
Methodology:
We performed pulse-chase incubations with 14C and 13C labeled bicarbonate under varying environmental conditions. A combination of tissue autoradiography, NanoSIMS 13C/12C isotope and sulfur elemental imaging coupled with transmission electron microscopy (TEM) was used to follow the fate of the radioactive and stable isotopes of carbon, respectively.
Results:
We show that symbiont cells fix substantial amounts of inorganic carbon in the presence of sulfide, but also (to a lower degree) in the absence of sulfide by utilizing internally stored sulfur. Isotope labeling patterns suggest translocation of organic carbon to the host through release of these compounds and digestion of symbiont cells. The latter mechanism was supported by TEM - based ultracytochemical detection of acid phosphatase in host lysosomes and in food vacuoles. In addition, fluorescence in situ hybridization (FISH) revealed that the vast majority of ingested microbial cells were ectosymbionts.
Conclusions/Outlook:
Tissue autoradiography allows analysis of large sample areas with many replicates. NanoSIMS correlated with TEM on the other hand opens the window to single cell physiology with ultrastructural resolution. Rounded off by ultracytochemistry and FISH, these very complementary techniques allowed us to highlight symbiont carbon fixation and subsequent transfer to the host in this thiotrophic symbiosis, confirming the nutritional role of the association. Beyond carbon, other elements such as nitrogen may be exchanged between symbiont and host and could be investigated with a similar technical approach.
References:
[1] Bright, M., Espada-Hinojosa, S., Lagkouvardos, I., Volland, J. 2014. The giant ciliate Zoothamnium niveum and its thiotrophic epibiont Candidatus Thiobios zoothamnicoli: A model system to study interspecies cooperation. Frontiers in Microbiology, 5 art. no. 145
| Original language | English |
|---|---|
| Publication status | Published - 18 Sept 2018 |
| Event | SIMS Europe 2018 / Conference and Workshop - Münster / Germany, Münster, Germany Duration: 16 Sept 2018 → 18 Sept 2018 |
Conference
| Conference | SIMS Europe 2018 / Conference and Workshop |
|---|---|
| Country/Territory | Germany |
| City | Münster |
| Period | 16/09/18 → 18/09/18 |
Austrian Fields of Science 2012
- 104002 Analytical chemistry
- 106022 Microbiology
- 106021 Marine biology
