Revival and characterization of fungi from ancient polar ice

Abstract

Glacial ice provides a unique global source of micro-organisms that allows study of both contemporary and ancient fungal diversity. The aim of this research was to revive and/or characterize fungi and fungal DNA entrapped in ancient ice cores from Greenland. Two main methods were developed to detect these micro-organisms in glacial ice: (1) Culturing to obtain viable isolates which were characterized by microscopy, PCR (polymerase chain reaction) amplification and DNA sequencing, using fungal ribosomal DNA internal transcribed spacer primers; and (2) PCR amplification and DNA sequencing directly from glacial ice. Hundreds of viable fungi (as well as bacteria) were isolated, and DNA sequences were obtained from Greenland ice cores up to 140,000 years old. Some sequences derived directly from ice melt resembled those of contemporary species, while others exhibited little similarity to well-characterized present-day fungi. Species diversity varied among the ice cores. Some fungi remain viable for over 100,000 years in ice. This leads to the possibility that a species can appear to become extinct, but may be capable of reappearing at a later point in time.