Insights into the Phylogeny and Evolution of Cold Shock Proteins: From Enteropathogenic and to Eubacteria.

Psychrotrophic foodborne pathogens, such as enteropathogenic , which are able to survive and multiply at low temperatures, require cold shock proteins (Csps). The Csp superfamily consists of a diverse group of homologous proteins, which have been found throughout the eubacteria. They are related to cold shock tolerance and other cellular processes. Csps are mainly named following the convention of those in . However, the nomenclature of certain Csps reflects neither their sequences nor functions, which can be confusing. Here, we performed phylogenetic analyses on Csp sequences in psychrotrophic enteropathogenic and . We found that representative Csps in enteropathogenic and can be clustered into six phylogenetic groups. When we extended the analysis to cover Enterobacteriales, the same major groups formed. Moreover, we investigated the evolutionary and structural relationships and the origin time of Csp superfamily members in eubacteria using nucleotide-level comparisons. Csps in eubacteria were classified into five clades and 12 subclades. The most recent common ancestor of Csp genes was estimated to have existed 3585 million years ago, indicating that Csps have been important since the beginning of evolution and have enabled bacterial growth in unfavorable conditions.