Recent studies into the stringent response and the discovery of a number of RNA polymerase binding proteins suggests that the model for bacterial transcription initiation in Actinobacteria may differ from that in Escherichia coli. In E. coli, the alarmone ppGpp, together with DksA, binds to RNA polymerase to elicit the stringent response. However, the ppGpp binding site on RNA polymerase is not conserved in S. coelicolor, although the organism possesses a DksA homologue. Deletion of DksA did not affect the growth and development of S. coelicolor, although its overexpression stimulated antibiotic production. Evidence is presented that suggests that this occurs through binding to the RNA polymerase secondary channel. The biological role of this protein remains unknown. CarD and RbpA are two RNA polymerase­‐binding proteins present in all Actinobacteria, including S. coelicolor and M. tuberculosis. Both proteins are critical for growth and have been identified as transcriptional activators from σHrdB­‐dependent promoters in vitro. Here it was demonstrated that CarD and RbpA activate transcription from rRNA promoters with a poorly conserved ­‐35 element. Surprisingly it was also found that both proteins can inhibit transcription from synthetic promoters with highly conserved ­‐35 elements. Chromatin immunoprecipitation followed by high throughput sequencing (ChIP­‐seq) experiments revealed that CarD and RbpA are found exclusively at promoter regions. RbpA is localised only at promoters recognised by σHrdB, whereas CarD also co‐localises with the alternative sigma factor σR during oxidative stress indicating that it lacks RNA polymerase holoenzyme specificity. The sigma specificity of RbpA was tested by the generation of sigma mutants that were defective in binding. In vivo, in vitro and ChIP­‐seq data presented in this study suggest that CarD and RbpA have an overlapping role in transcription initiation at σHrdB­‐dependent promoters in S. coelicolor.

Yersinia pestis, the aetiological agent of plague, is responsible for a disease that has killed over 200 million people throughout history and generated three pandemics. This bacterium's terrible success in causing disease is owed greatly to the virulence factors it expresses. Two of these factors are V antigen (LcrV) and F1 antigen (Caf1), both of which are two major antigens which the immune system produces antibodies against. V antigen is already known to have vital roles in Y. pestis gene expression and translocating other virulence factors into the host cells as well as having some immunosuppressive effects while F1 antigen is better known for possessing an antiphagocytic effect. The effects that these two antigens have in modulating the innate immune system of Mono Mac 6 cells were studied, such as modulation of expression of pattern recognition receptors (PRRs), in particular Toll-like receptors (TLRs), activation of NF-κB and secretion of cytokines, particularly those involved in inflammatory responses, as well as localising where in the cell these antigens target to. It was demonstrated that both V and F1 antigens possess immunosuppressive abilities, such as downregulation of TLRs as well as inhibitition of NF-κB activation and suppression of secretion of the cytokines TNF-α, IL-6 and IL-10. Furthermore, stimulation with only either V or F1 antigens can upregulate expression of the scavenger receptor CD36 and are capable of inducing secretion of the anti-inflammatory cytokine IL-10. V and F1 antigens were found to localise in the Golgi apparatus 30 minutes after stimulation and it was also determined that these antigens interfere with the signalling molecule MyD88.