title: Pseudomonas aeruginosa uses type III secretion system to kill biofilm-associated amoebae.
abstract: Bacteria and protozoa coexist in a wide range of biofilm communities of natural, technical and medical importance. Generally, this interaction is characterized by the extensive grazing activity of protozoa on bacterial prey populations. We hypothesized that the close spatial coexistence in biofilms should allow opportunistic pathogenic bacteria to utilize their eukaryote-targeting arsenal to attack and exploit protozoan host cells. Studying cocultures of the environmental pathogen Pseudomonas aeruginosa and the amoeba Acanthamoeba castellanii, we found that P. aeruginosa rapidly colonized and killed biofilm-associated amoebae by a quorum-sensing independent mechanism. Analysis of the amoeba-induced transcriptome indicated the involvement of the P. aeruginosa type III secretion system (T3SS) in this interaction. A comparison of mutants with specific defects in the T3SS demonstrated the use of the secretion apparatus and the effectors ExoU, ExoS and ExoT in the killing process, of which ExoU had the greatest impact. T3SS-mediated virulence towards A. castellanii was found to be controlled by the global regulators RpoN and RpoS and through modulation of cAMP and alginate biosynthesis. Our findings suggest that conserved virulence pathways and specifically the T3SS play a central role in bacteria-protozoa interactions in biofilms and may be instrumental for the environmental persistence and evolution of opportunistic bacterial pathogens.
authors.affiliation: School of Biotechnology and Biomolecular Sciences and Centre for Marine Bio-Innovation, University of New South Wales, Sydney, Australia. carsten.matz@helmholtz-hzi.de
authors.forename: Carsten
authors.initials: C
authors.lastname: Matz
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Moreno
authors.forename: Morten
authors.initials: M
authors.lastname: Alhede
authors.forename: Mike
authors.initials: M
authors.lastname: Manefield
authors.forename: Alan R
authors.initials: AR
authors.lastname: Hauser
authors.forename: Michael
authors.initials: M
authors.lastname: Givskov
authors.forename: Staffan
authors.initials: S
authors.lastname: Kjelleberg
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics / Q000378:metabolism; D048248:Acanthamoeba castellanii / Q000187:drug effects* / Q000382:microbiology* / Q000502:physiology; D000818:Animals; D000898:Antibiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology / Q000633:toxicity*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects*; D018920:Coculture Techniques; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000502:physiology*; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012808:Sigma Factor / Q000502:physiology; D037521:Virulence Factors / Q000378:metabolism / Q000633:toxicity
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C477521:ExoT protein, Pseudomonas aeruginosa; D020690:GTPase-Activating Proteins; D026901:Membrane Transport Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012808:Sigma Factor; D037521:Virulence Factors; C111749:pseudomonas exoprotein A protein, Pseudomonas aeruginosa; C069567:sigma factor KatF protein, Bacteria; D036002:ADP Ribose Transferases; C444820:exoenzyme S