Antarctic Bacteria as Astrobiological Models

Antarctica contains many different types of habitat that would traditionally be considered harsh from a human perspective; it can be extremely cold, have low levels of liquid water, low humidity, low nutrient availability, high levels of salinity and high levels of non-ionizing radiation. Yet a wide variety of bacteria have been found living there, despite these harsh conditions; some of them are believed to be unique to the continent, others more cosmopolitan in distribution. When we compare aspects of these Antarctic habitats to conditions known to occur on Mars, or to what is known of the icy moons of Jupiter and Saturn, we find notable similarities even though, clearly, significant differences remain. It is therefore unsurprising that scientists have used bacteria isolated from the Antarctic as astrobiological models. The extent to which this has been done to date, however, is perhaps surprisingly limited despite the enormous potential in this approach. In this chapter, we examine the differences and similarities between specific habitats in Antarctica and those which they might mimic on Mars, Europa and Enceladus. It considers the nature of the microbiological adaptions found in these Antarctic habitats and the experiments carried out to date on bacteria isolated from them. The chapter concludes by discussing the future potential of Antarctic bacterial species as well as the lessons learnt in understanding the limits of life here on Earth and the possibility of finding evidence of microbial life elsewhere in the solar system.