The Aggregatibacter aphrophilus Type VI Secretion System - an Initial Characterization
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Type VI secretion system (T6SS) is an important virulence factor for many Gram-negative species, for example Vibrio cholerae. The T6SS translocates effector proteins. Hemolysin co-regulated protein (Hcp) is a protein important for the T6SS function and can be found on the outside of the bacteria. Presence of extracellular Hcp can therefore be used as a marker of an active T6SS. Genome sequence analysis has revealed genes of a T6SS in one isolate of Aggregatibacter aphrophilus (NJ8700). A. aphrophilus is an oral bacterium closely related to the periodontal pathogen Aggregatibacter actinomycetemcomitans, which does not have a T6SS. The aim of this study was to confirm the presence of T6SS- encoding genes and to test if the system was functionally expressed in three A. aphrophilus isolates, (AHI- 3151, IH- 90256, and CCUG 3715). A genetic map of the A. aphrophilus T6SS gene cluster was generated based on the whole genome sequence of NJ8700, showing many similarities with the T6SS gene cluster in V. cholerae. This also led to the identification of a putative A. aphrophilus T6SS substrate, Hcp protein. Conservation of three T6SS-associated genes was analyzed by PCR, results showed presence of these genes in all tested A. aphrophilus strains. The functionality of the T6SS was tested by immunoblot analyses using antiserum against Hcp of V. cholerae, however without detecting Hcp in any of the samples. Hcp and a T6SS related lipoprotein were however found in strain AHI-3151 culture supernatants using LC-MS/MS, which indicates an active T6SS in this A. aphrophilus strain.
Place, publisher, year, edition, pages
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:umu:diva-113634OAI: oai:DiVA.org:umu-113634DiVA: diva2:886221