What’s on : Lectures

Life in hot acid: the alga Galdieria

8 Feb 2022
Start time
7:30 PM
Professor Seth Davis, University of York
Life in hot acid: the alga Galdieria

Event Information

Life in hot acid: the alga Galdieria
Professor Seth Davis, Department of Biology, University of York

Galdieria species are extremophilic microalgae with amazing diversity of metabolism, essentially unparalleled in the eukaryotic kingdom. Galdieria thrives to acidic pH = 0 and 56˚C, the limits of eukaryotic life, can grow as an autotroph performing photosynthesis in the light and as a heterotroph in the dark by consuming essentially any sugar or other carbon source. Galdieria originates from fumarole vents that emit sulphur gases, which are companions to volcanic activity. These algae are also colonisers of human-made waste sites that are acidic and loaded with toxins, such as in acid-mine drainage. Galdieria can remediate contaminants under high concentrations of toxic metals and thus are targets for bespoke bio-mining applications for precious metal and rare-earth metal accumulation. Full genome sequencing serves as a start to explore the mechanisms of all these strange biological features that defines it metabolic diversity. In this the nuclear and organellar genomes of Galdieria are now completed using long-read sequencing, and this technology will be explained. The genomics of Galdieria should explain how it responds rapidly to adaptive shifts in extreme environments to support a eukaryotic extremophilic life.

Member’s Report

Everyone knows that living organisms cannot survive temperatures of 55°C, or extremely acid conditions, that plants photosynthesise and other organisms can’t.  Seth Davis introduced us to Galdieria, a single-celled red alga, which can do all of the above, and more.  Galdieria flourishes at temperatures above 55°C and at pH values of 0 – 4 (around that of concentrated sulphuric acid) and it can switch between photosynthesis and other forms of nutrition, depending on circumstances.  It has other tricks up its sleeve, such as harvesting genetic material from its environment in case it finds ‘stranger’ genes it can assimilate and put to use.

Understanding the Galdieria genome is crucial to understanding how it works, as well as its relatedness to other organisms. Seth introduced us to some of the current techniques of genome analysis (collectively, these have reduced the cost of sequencing a single genome from billions of $US – remember the ‘moon-shot’ Human Genome Project? – to around £150).  These include the remarkable nanopore technique, where a single DNA molecule feeds through a very very small pore; electrical potential across the pore varies according to which base is currently passing through, and the entire linear sequence of bases of the DNA molecule can be read off, rather like listening to a tune as magnetic tape passes through the playback head of a tape recorder.

Extremophiles such as Galdieria have the advantage of carrying out useful biological processes fast, and without interference from less hardy organisms; given its peculiarities, Galdieria can, potentially be put to use in many ways. Among those currently being explored by Seth Davis and his team at the University of York are the removal of toxic heavy metals from the environment – potentially valuable in relation to water purity – or post-war soil remediation, and the recycling of the ‘rare earth’ elements, in short supply, vital to the workings of mobile phones, and notoriously difficult to separate by conventional chemical means.

There are likely to be difficulties in scaling up such processes from ‘proof of concept’ to practical application: but we certainly haven’t heard the last of Galdieria.

Peter Hogarth