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Title: Temperature-dependent regulation in the Bacillus cereus-Bacillus anthracis crossover strain, Bacillus cereus G9241
Author: Brooker, Thomas Adam
ISNI:       0000 0004 9357 7983
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2019
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Bacillus cereus G9241 was originally isolated from a Louisiana welder suffering from an anthrax-like infection. A member of the Bacillus cereus sensu lato complex, strain G9241 is closely related to the mammalian pathogen Bacillus anthracis. It contains two plasmids pBCX01 and pBC218, which are homologous and analogous to pX01 and pX02 respectively, from Bacillus anthracis. In addition, it contains a phagemid, pBFH_1 encoding a putative prophage. The gene for PlcR, which is the pleiotropic quorum sensing regulator of secreted proteins, is truncated in all B. anthracis isolates. The current dogma suggests this truncation evolved to accommodate the acquisition of the anthrax toxin regulator, AtxA encoded on the pX01 plasmid. B. cereus G9241 appears to break this dogma as it encodes intact copies of both plcR and atxA. Work prior to this study showed when cultured at 25 °C, cell free B. cereus G9241 culture supernatant is cytotoxic to human macrophages, PMNs and T2 lymphocytes in addition to insect haemocytes from Manduca sexta. However, the cytotoxic activity of the culture supernatant is lost at 37 °C. B. cereus G9241 is also motile at 25 °C but immotile at 37 °C. This study proposes that BcG9241 is able to switch between B. cereus and B. anthracis –like phenotypes in a temperature-dependent manner. A combination of RNAseq, whole cell and secretome proteomics suggests that differential regulation of PlcR at a post transcriptional level is responsible for the temperature-dependent cytotoxic activity of the culture supernatant and temperature-dependent motility. Furthermore, expression from the extrachromosomal elements increases at 37 °C, particularly from the phagemid pBFH_1. This study shows that pBFH_1 encoded phage particles are expressed at 37 °C and this may be a link to a rapid sporulation phenotype also seen at this temperature.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QR Microbiology