An ICEBs1-like element may be associated with the extreme radiation and desiccation resistance of Bacillus pumilus SAFR-032 spores

Comparisons of the genomes of Bacillus pumilus SAFR-032 and the closely related type strain, B. pumilus ATCC7061^T, exposed an extended region of non-homologous genes. A detailed examination of this region revealed the presence of an ICEBs1-like integrative conjugative element in SAFR-032. A similar element was subsequently located elsewhere in the ATCC7061^T genome. A detailed comparison of these elements and the ICEBs1 of B. subtilis revealed extremely rapid flux in gene content, genome organization and sequence similarity. It is not clear if the B. pumilus elements as they are currently structured are functional. However, it is clear that the past involvement of these elements has brought multiple genes of unknown function to the SAFR-032 genome and these genes may be responsible for the rapid evolution that led to the extreme radiation and desiccation resistance of this organism’s spores.