A bacterium from a mountain lake harvests light using both proton-pumping xanthorhodopsins and bacteriochlorophyll-based photosystems

0565420 - MBÚ 2023 RIV US eng J - Journal Article
Kopejtka, Karel - Tomasch, Jurgen - Kaftan, David - Gardiner, Alastair T. - Bína, David - Gardian, Zdenko - Bellas, Ch. - Dröge, A. - Geffers, R. - Sommaruga, R. - Koblížek, Michal
A bacterium from a mountain lake harvests light using both proton-pumping xanthorhodopsins and bacteriochlorophyll-based photosystems.
Proceedings of the National Academy of Sciences of the United States of America. Roč. 119, č. 50 (2022), č. článku e2211018119. ISSN 0027-8424. E-ISSN 1091-6490
R&D Projects: GA ČR(CZ) GX19-28778X; GA MŠMT(CZ) EF18_053/0017705; GA MŠMT(CZ) LM2018129
Institutional support: RVO:61388971 ; RVO:60077344
Keywords : anoxygenic photosynthesis * bacteriochlorophyll a * dual phototrophy * light energy * xanthorhodopsin
OECD category: Microbiology; Cell biology (BC-A)
Impact factor: 11.1, year: 2022
Method of publishing: Limited access
https://www.pnas.org/doi/10.1073/pnas.2211018119

Photoheterotrophic bacteria harvest light energy using either proton-pumping rhodopsins or bacteriochlorophyll (BChl)-based photosystems. The bacterium Sphingomonas glacialis AAP5 isolated from the alpine lake Gossenköllesee contains genes for both systems. Here, we show that BChl is expressed between 4°C and 22°C in the dark, whereas xanthorhodopsin is expressed only at temperatures below 16°C and in the presence of light. Thus, cells grown at low temperatures under a natural light-dark cycle contain both BChl-based photosystems and xanthorhodopsins with a nostoxanthin antenna. Flash photolysis measurements proved that both systems are photochemically active. The captured light energy is used for ATP synthesis and stimulates growth. Thus, S. glacialis AAP5 represents a chlorophototrophic and a retinalophototrophic organism. Our analyses suggest that simple xanthorhodopsin may be preferred by the cells under higher light and low temperatures, whereas larger BChl-based photosystems may perform better at lower light intensities. This indicates that the use of two systems for light harvesting may represent an evolutionary adaptation to the specific environmental conditions found in alpine lakes and other analogous ecosystems, allowing bacteria to alternate their light-harvesting machinery in response to large seasonal changes of irradiance and temperature.
Permanent Link: https://hdl.handle.net/11104/0336944