Dependence on epiphytic bacteria for freezing protection in an Antarctic moss, Bryum argenteum

• Published in: Environmental Microbiology Reports
• Main Author: Raymond, James A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1111/1758-2229.12337; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1758-2229.12337; http://onlinelibrary.wiley.com/wol1/doi/10.1111/1758-2229.12337/fullpdf

Summary Mosses are the dominant flora of A ntarctica, but their mechanisms of survival in the face of extreme low temperatures are poorly understood. A variety of B ryum argenteum from 77 o S was previously shown to have strong ice‐pitting activity, a sign of the presence of ice‐binding proteins ( IBPs ) that mitigate freezing damage. Here, using samples that had been stored at −25 o C for 10 years, it is shown that much if not all of the activity is due to bacterial ice‐binding proteins secreted on the leaves of the moss. Sequencing of the leaf metagenome revealed the presence of hundreds of genes from a variety of bacteria (mostly A ctinobacteria and B acteroidetes ) that encode a domain ( DUF 3494) that is associated with ice binding. The frequency of occurrence of this domain is one to two orders of magnitude higher than it is in representative mesophilic bacterial metagenomes. Genes encoding 42 bacterial IBPs with N ‐terminal secretion signals were assembled. There appears to be a commensal relationship in which the moss provides sustenance to the bacteria in return for freezing protection.