Tuesday, 8 January 2019

A microbe's membrane helps it survive extreme environments

Within harsh environments like hot springs, volcanic craters and deep-sea hydrothermal vents -- uninhabitable by most life forms -- microscopic organisms are thriving. How? It's all in how they wrap themselves.

Stanford University researchers have identified a protein that helps these organisms form a protective, lipid-linked cellular membrane -- a key to withstanding extremely highly acidic habitats.

Scientists had known that this group of microbes -- called archaea -- were surrounded by a membrane made of different chemical components than those of bacteria, plants or animals. They had long hypothesized that it could be what provides protection in extreme habitats. The team directly proved this idea by identifying the protein that creates the unusual membrane structure in the species Sulfolobus acidocaldarius.

The structures of some organisms' membranes are retained in the fossil record and can serve as molecular fossils or biomarkers, leaving hints of what lived in the environment long ago. Finding preserved membrane lipids, for example, could suggest when an organism evolved and how that may have been the circumstance of its environment. Being able to show how this protective membrane is created could help researchers understand other molecular fossils in the future, offering new evidence about the evolution of life on Earth.

Archaea are sometimes called the "third domain of life," with one domain being bacteria and the other being a group that includes plants and animals -- collectively known as eukaryotes. Archaea includes some of the oldest, most abundant lifeforms on the planet, without which the ecosystem would collapse. Archaea are particularly anomalous microbes, confused with bacteria one day and likened to plants or animals the next because of their unique molecular structures.

The research is particularly interesting because the classification for archaea is still debated by taxonomists. They were only separated from the bacteria and eukaryote domains in the past two decades, following the development of genetic sequencing in the 1970s.


Zhirui Zeng, Xiao-Lei Liu, Jeremy H. Wei, Roger E. Summons, and Paula V. Welander. Calditol-linked membrane lipids are required for acid tolerance in Sulfolobus acidocaldarius. Proceedings of the National Academy of Sciences, 2018; DOI: 10.1073/pnas.1814048115

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology

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