title: The Burkholderia pseudomallei Proteins BapA and BapC Are Secreted TTSS3 Effectors and BapB Levels Modulate Expression of BopE.
abstract: Many Gram-negative pathogens use a type III secretion system (TTSS) for the injection of bacterial effector proteins into host cells. The injected effector proteins play direct roles in modulation of host cell pathways for bacterial benefit. Burkholderia pseudomallei, the causative agent of melioidosis, expresses three different TTSSs. One of these systems, the TTSS3, is essential for escape from host endosomes and therefore intracellular survival and replication. Here we have characterized three putative TTSS3 proteins; namely BapA, BapB and BapC. By employing a tetracysteine (TC)-FlAsH™ labelling technique to monitor the secretion of TC-tagged fusion proteins, BapA and BapC were shown to be secreted during in vitro growth in a TTSS3-dependant manner, suggesting a role as TTSS3 effectors. Furthermore, we constructed B. pseudomallei bapA, bapB and bapC mutants and used the well-characterized TTSS3 effector BopE as a marker of secretion to show that BapA, BapB and BapC are not essential for the secretion process. However, BopE transcription and secretion were significantly increased in the bapB mutant, suggesting that BapB levels modulate BopE expression. In a BALB/c mouse model of acute melioidosis, the bapA, bapB and bapC mutants showed a minor reduction of in vivo fitness. Thus, this study defines BapA and BapC as novel TTSS3 effectors, BapB as a regulator of BopE production, and all three as necessary for full B. pseudomallei in vivo fitness.
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Department of Microbiology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Puthayalai
authors.initials: P
authors.lastname: Treerat
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Department of Microbiology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Priyangi
authors.initials: P
authors.lastname: Alwis
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Biochemistry and Molecular Biology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Tanya
authors.initials: T
authors.lastname: D'Cruze
authors.affiliation: Department of Microbiology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Meabh
authors.initials: M
authors.lastname: Cullinane
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Department of Microbiology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Jamunarani
authors.initials: J
authors.lastname: Vadivelu
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Biochemistry and Molecular Biology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Rodney J
authors.initials: RJ
authors.lastname: Devenish
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Biochemistry and Molecular Biology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Prescott
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Department of Microbiology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: Ben
authors.initials: B
authors.lastname: Adler
authors.affiliation: Infection and Immunity Program, Monash Biomedicine Discovery Institute, and Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton campus, Victoria 3800, Australia.|Department of Microbiology, Monash University, Clayton campus, Victoria 3800, Australia.
authors.forename: John D
authors.initials: JD
authors.lastname: Boyce
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D016957:Burkholderia pseudomallei / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D008554:Melioidosis / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation / Q000235:genetics; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors