Throughout its infection of the mammalian host, Bacillus anthracis is confronted with a number of different hostile environments to which it must adapt its gene expression and physiology. These adaptations are critical for pathogenesis, but they remain poorly understood. The fifteen ECF (extracytoplasmic function) RNA polymerase sigma factors encoded within the B. anthracis genome appear to be possible regulators of these adaptations, since studies in other bacterial species have shown the ECF proteins to be master regulators mediating bacterial responses to the environment. We hypothesize that one or more of these fifteen proteins might play a role in mediating the response of B. anthracis to stresses encountered during infection, and our preliminary experiments showed that three ECF proteins are critical for virulence in a mouse model of inhalational anthrax. Here we propose to characterize these three proteins in more detail, using two parallel approaches. In the first, we will use phenotype microarrays to screen nearly 2000 different environmental stimuli for conditions in which the deletion of a given ECF factor has an effect on growth of B. anthracis. With this approach we can cover every environmental condition previously associated with ECF factors in any bacterium (plus hundreds of others), and we will confirm and more closely define the phenotypic defects of ECF mutants in further growth studies. These data will tell us a great deal about ECF function, and will also point to specific conditions we can use in later experiments examining the roles of each individual protein. In the second set of experiments, we will use comparative transcriptional profiling to define the regulon associated with each of the three ECF proteins; these data will provide important clues about the function of each ECF factor, and will identify downstream effectors. We expect that in defining the stimuli and regulon associated with each of these three B. anthracis ECF proteins, we will gain significant insights into the B. anthracis-host interaction, and that these insights will likely be broadly applicable to other bacterial pathogens, since the ECF family is found throughout the bacterial domain. Further, we anticipate that the proposed work may lead to new strategies for developing new therapeutic options for treating or preventing anthrax and other bacterial infections.
Showing the most recent 10 out of 400 publications
