[PMC free article] [PubMed] [CrossRef] [Google Scholar] 9. by CtrA, whereas the expression of the chemotaxis genes that control Fla1 is usually mediated by the grasp regulators of the Fla1 system. The coordinated expression of the chemosensory Galanthamine hydrobromide proteins with their cognate flagellar genes highlights the relevance of integrating the expression of the horizontally acquired genes with a chemosensory system independently of the regulatory proteins responsible for the expression of and its cognate chemosensory system. IMPORTANCE Gene acquisition via horizontal transfer represents a challenge to Galanthamine hydrobromide the recipient organism to adjust its metabolic and genetic networks to incorporate the new material in a way that represents an adaptive advantage. In the case of and and and (11, 12). In the alphaproteobacteria and is an alphaproteobacterium with two different flagellar systems, multiple copies of the chemotaxis genes, and four different genes, encoding functionally different 54 factors. 54-2 has been shown to be required to transcribe one of the flagellar units (15,C17). This bacterium assembles a single, subpolar flagellum under standard laboratory growth conditions (18), and the products of the genes are responsible for the formation and functioning of this structure. The expression of these genes follows a hierarchical pattern. At the top of the hierarchy, the grasp protein FleQ, together with the Galanthamine hydrobromide RNA polymerase core (E) associated with the 54-2 factor, promotes the expression of the class II flagellar operon (which encodes 28) and (encoding the anti-sigma factor of Galanthamine hydrobromide 28). Once the HBB has been assembled, FlgM is usually exported out of the cell, and 28 is usually free to associate with E to transcribe the late flagellar genes, such as those encoding flagellin (FliC) and its scaffold protein, FliD (19). The other flagellar system present in genes are not expressed under standard laboratory growth conditions. So far, the Fla2 flagellar system has been analyzed in mutant strains that are unable to form Fla1 due to a mutation in a regulatory or structural gene and importantly contain a gain-of-function mutation in the histidine kinase CckA. In these strains, it has been determined that this expression of is dependent around the two-component system formed by the histidine kinase CckA, the phosphotransferase protein ChpT, and the response regulator CtrA (21). Phylogenetic studies have shown that this genes constitute the native flagellar genes of set was acquired by horizontal transfer from an ancestral gammaproteobacterium (16). In genes are in red. Black outlines group the chemotaxis operons that control Fla1 or Fla2. The control of Fla1 was shown to be mediated by the products of operon 2 (gene. The expression of and and has four 54 factors, two of which, 54-1 and 54-2, are activated by specific bEBPs (i.e., NifA and FleQ/FleT, respectively) (17, 30). Potential bEBP-encoding genes were previously recognized in the genome of system (FleQ) is the activator protein for this operon. In addition, we found out that expression is dependent on 28 (FliA) and, consequently, is usually also a part of the flagellar transcription hierarchy. Our results also show that is coordinated with the expression of their cognate flagellar system. RESULTS In this work, we used derivatives of the WS8N and AM1 strains to study the regulation of the flagellar and chemotaxis genes. WS8N is the wild-type strain that constitutively expresses the Fla1 flagellum but is unable to express the genes given that the two-component system CckA/ChpT/CtrA is usually inactive. The AM1 strain is usually a WS8N derivative that is unable to express the genes, given that it carries a mutation in the flagellar grasp Galanthamine hydrobromide activator and also carries a point mutation in that activates the CckA/ChpT/CtrA two-component system (21, 25); therefore, this strain has a Fla1? Fla2+ phenotype. genes. The expression of three chemotaxis proteins encoded in (Fig. 2A), indicating that with the Flag epitope in the AM1 strain. The resulting strain, JV1 (allele indicates that this WS8N and (SP13) strains do not carry the gain-of-function mutation in CckA that enables the expression of the genes whereas the AM1 strain and its derivatives carry the mutations and, importantly, derivative (LC7 strain) transporting the transcriptional fusion were produced in 80 M succinic acid, and total cell extracts were utilized for the LRRC63 enzymatic reaction. Activity is usually reported in picomoles of 4-methylumbelliferone produced per minute.