Between a rock and a soft place

Written by Associate Professor Brendan Burns

Viruses are not doing well in the news at the moment. When you hear the word ‘virus’ it is not likely to be good news that follows. However, the fact is a lot of viruses are not only ‘good’ but are critical to life on the planet. They are major players in many processes such as essential nutrient cycles of carbon and nitrogen. They can also shuffle beneficial genetic material to make organisms ‘fitter’.

Sample piece from the field in Shark Bay, Western Australia

We also postulate that they may have been critical in the evolution of early life on Earth. In a recent opinion piece from our group in Trends in Microbiology (White et al., 2021), we believe viruses play a major role in the transition from a ‘soft’ microbial mat to a ‘hard’ concrete-like stromatolite. Stromatolites are one of the oldest known microbial ecosystems, dating back some 3.7 billion years and fossils of these microbial ecosystems are some of our earliest records of life. Microbial mats can be likened to an earlier phase of stromatolite, a ‘softer’ version more common today in places such as Shark Bay in Western Australia. Given their longevity it has even been suggested that some eukaryotes may have evolved in these systems. 

Trends in Microbiology Front Page

However, despite their evolutionary importance the exact mechanism of transition from mat to stromatolite is not completely understood. We propose viruses may be a missing interaction in the transition from microbial mat to stromatolite, and potentially viral mechanisms that lead to stromatolite formation could produce biosignatures – a record of past or present life – which has implications for improving our understanding of the evolution of the biosphere. Indeed understanding the role of viruses in these systems may provide insight into the development of key biological processes and pathways relevant to the origin of life on Earth. 

And, with the Mars Perseverance Rover (‘Percy’) set to touch down on Mars with a mission to look for past evidence of life, it is an exciting time to be in the field of astrobiology understanding microbial components of modern and ancient ecosystems – including viruses.

White RA, Visscher PT, Burns BP (2021). Between a rock and a soft place: viral role in stromatolite formation. Trends in Microbiology 29, 204-213 (doi.org/10.1016/j.tim.2020.06.004)