PhoB-dependent genes in <i>B. fragilis</i>.

<p>(A) Classification of genes whose expression levels were altered more than 4-fold under Pi limitation (0.0066 mM of KH₂PO₄) in wild type and Δ<i>phoB</i> mutant strains, compared to levels in wild type in the presence of sufficient Pi (6.6 mM of KH₂PO₄). Left and right circles indicate the differentially expressed genes of wild type and Δ<i>phoB</i> mutant strains with expressions that were altered over 4-fold under Pi limitation. Group 1: includes 245 PhoB-dependent Pi-response genes. Group 3∶217 PhoB-dependent genes unrelated to Pi response. Group 2 contains two subgroups. Group 2a: 276 PhoB-independent Pi-response genes (fold change in expression in response to Pi-limitation was similar between wild type and Δ<i>phoB</i> mutant strains); Group 2b: 123 PhoB-dependent Pi response genes (the extent of change in expression in response to Pi-limitation was different >2-fold between wild type and Δ<i>phoB</i> mutant strains). (B) COG classification of PhoB-dependent (black bar) and PhoB-independent (white bar) genes that are differentially expressed during Pi starvation. The percentage of genes classified into each COG category is relative to the total number of genes in each group. Fifty-five percent of the PhoB-dependent (585 genes) and 60% of the PhoB-independent (276 genes) groups could not be assigned to a COG category (that data are not included in this figure).