Outer Structures of theBacillus anthracisSpore

Contrasting evolutionary patterns of spore coat proteins in two Bacillus species groups are linked to a difference in cellular structure

“…Specifically, we expected to find that coat proteins closer to the spore surface would be more labile than coat proteins at more interior locations. To test this hypothesis, we first analyzed the phylogenetic profiles of the coat proteins in B. subtilis , because it is already known that many if not most of the outermost proteins in B. subtilis are among the already identified outer coat proteins (or outer coat protein candidates) [ 14 , 17 , 48 , 58 ]. We note that proteins designated in the literature or in genome annotations as members of the outer coat could also be present in the crust, the recently identified and still poorly characterized coat layer surrounding the outer coat [ 31 ].…”

“…We were unable to find a correlation between the known phenotype of each coat protein gene mutation and its degree of conservation. However, this is not surprising, as coat protein gene mutants are rarely if ever analyzed using ecologically realistic assays [ 17 ]. Interestingly, many coat proteins have a significant proportion of disordered regions (see supporting information).…”

“…This is an especially interesting question given that the majority of the morphological variation among Bacillus spores is in the coat (as well as the exosporium) [ 27 - 29 ]. Importantly, by measuring the degree of selection on a coat protein, it may be possible to show that coat proteins have evolutionarily important roles even when the corresponding coat protein gene mutants lack a detectable phenotype in the laboratory [ 17 , 42 ].…”