Research

Studies on halophilic and phototrophic bacteria

The Halophilic and Phototrophic Bacteria group takes part in several research projects in collaboration with a variety of international experts and research institutions. The focus of these studies ranges from microbial ecology studies of phototrophic bacteria in their natural environment, such as hot spring microbial mats, over the investigation of intramolecular carbon isotopic structures of biogenic phytane found in fossil sediment samples, to the unusual polygonalshaped assemblies and shapeshifting in halophilic Archaea.

Fig. 1: Pictures of Mushroom Spring, a well studied hot spring in Yellowstone National Park, USA. The oxygenic phototrophic microbial mats developing at temperatures between 45-70°C are characterized by a green upper layer and an orange colored undermat.

Hot spring associated microbial mats are natural habitats for phototrophic bacteria and due to their low diversity wonderful model systems for research studies in the area of microbial ecology, interspecies interactions and evolution of photosynthesis, as well as the detection and isolation of novel phototrophic bacteria, which we conduct in collaboration with researchers in the USA, Japan and Denmark.

Fig. 2: The impressive morphological diversity among haloarchaea. From rods (H. salinarum) to triangles (H. japonica), it is still unknown how many more new cell shapes are waiting to be discovered. H. walsbyi (square archaeon) image kindly provided by Mike Dyall-Smith. Scale bar represents 2 μm.

Haloarchaea (salt-loving Archaea) are known for their high diversity of cell morphologies, with distinct polygonal morphologies and differences not only among closely related species; but are also capable of ‚shapeshifting‘ between different morphologies depending on the growth phase. The DSMZ joins an international research team around Ass. Prof. Alexandre Bisson (Brandeis University, USA), to study the biophysical and spatio-temporal control of unusual polygonalshaped assemblies and specifically, the cell shape polymorphology across the haloarchaea.

Fig. 3: Phytane was also detected in this approx. 725-777 million years old sediment core piece such as this sample from the Officer Basin in Western Australia showing the stromatolite Baicalia burra, a fossilized microbial mat containing cyanobacteria. (Photo by M. Öztoprak, NIOZ)

One of the most common sedimentary isoprenoids is phytane (C20), which can be either of archaeal origin or potentially represent the most important biological marker for phototrophs in the fossil record. Currently, it is not possible to distinguish between phytane derived from either of those two organismal groups. In collaboration with the group around Dr. Laura Villanueva from NIOZ we will study phytane from chlorophyll of a diverse set of phosynthetic bacteria as well as archaeol from archaea at natural abundance (~10 nmol total analyte) to identify pathways specific intramolecular isotopic signatures, which will serve to establish a novel tool to assign the origin of phytane in natural samples of unknown origin(s).

Selected publications

  1. Kawai, S., Martinez, J. N., Lichtenberg, M., Trampe, E., Kühl, M., Tank, M., Haruta, S., Nishihara, A., Hanada, S., & Thiel, V. (2021). In-situ metatranscriptomic analyses reveal the metabolic flexibility of the thermophilic anoxygenic photosynthetic bacterium Chloroflexus aggregans in a hot spring cyanobacteria-dominated microbial mat. Microorganisms, 9(3), 1–22. doi.org/10.3390/microorganisms9030652
  2. Saini, M. K., ChihChe, W., Soulier, N., Sebastian, A., Albert, I., Thiel, V., Bryant, D. A., Hanada, S., & Tank, M. (2020). Caldichromatium japonicum gen. nov., sp. nov., a novel thermophilic phototrophic purple sulphur bacterium of the Chromatiaceae isolated from Nakabusa hot springs, Japan. International Journal of Systematic and Evolutionary Microbiology, 7. doi.org/10.1099/ijsem.0.004465
  3. Martinez, J. N., Nishihara, A., Lichtenberg, M., Trampe, E., Kawai, S., Tank, M., Kühl, M., Hanada, S., & Thiel, V. (2019). Vertical distribution and diversity of phototrophic bacteria within a hot spring microbial mat (Nakabusa hot springs, Japan). Microbes and Environments, 34(4), 374–387. doi.org/10.1264/jsme2.ME19047
  4. Thiel, V., Costas, A. M. G., Fortney, N. W., Martinez, J. N., Tank, M., Roden, E. E., Boyd, E. S., Ward, D. M., Hanada, S., & Bryant, D. A. (2019). “Candidatus Thermonerobacter thiotrophicus,” a non-phototrophic member of the Bacteroidetes/Chlorobi with dissimilatory sulfur metabolism in hot spring mat communities. Frontiers in Microbiology, 10(JAN), 1–24. doi.org/10.3389/fmicb.2018.03159
  5. Tank, M., Thiel, V., Ward, D. M., & Bryant, D. A. (2017). A Panoply of Phototrophs: An Overview of the Thermophilic Chlorophototrophs of the Microbial Mats of Alkaline Siliceous Hot Springs in Yellowstone National Park, WY, USA. In Modern Topics in the Phototrophic Prokaryotes: Environmental and Applied Aspects (pp. 1–492). doi.org/10.1007/978-3-319-46261-5

 

Dr. Vera Thiel

Group leader