The matrix of ancient biofilms modulates stress tolerance

From an evolutionary and ecological perspective the Cyanobacteria are of particular interest. Why is one of the key Precambrian organisms still one of the most important groups of phototrophs today? The hypothesis that the morphology and physiology of cyanobacteria has evolved little, or not at all, over thousands of millions of years, remains unproven. What does seem likely is that the success of desiccation‐tolerant cyanobacteria stems, in large part, from a capacity to withstand multiple and superimposed environmental stresses. A knowledge of how these organisms accomplish this feat is thus of fundamental significance to microbial ecology, physiology and evolution. Our work aims to understand the overall effects of complex environmental stresses on the diversity, metabolism, and genome structure of cyanobacterial biofilms. Our perspective is that these communities are ancient biosensors that facilitated the rise of the cyanobacteria and their subsequent success in diverse extreme environments. Observations of polymorphic peptides in native extracellular water stress protein (WspA), polymorphic wspA sequences from different colonies, presence in WspA of primary sequences that are the most susceptible to deamidation, and genetic heterogeneity of the single copy wspA gene from different sources of Nostoc commune strongly supports the hypothesis that a single Nostoc colony may contain multiple, if not a continuum, of morphotypes. Similar diversity is displayed by Gloeocapsa spp., the predominant cyanobacteria found on asphalt shingle roof communities of worldwide distribution. Extension of this concept infers that the global diversity (and plasticity) of one “organism” may be enormous, with profound inherent regulatory consequences.