title: Genomes and virulence factors of novel bacterial pathogens causing bleaching disease in the marine red alga Delisea pulchra.
abstract: Nautella sp. R11, a member of the marine Roseobacter clade, causes a bleaching disease in the temperate-marine red macroalga, Delisea pulchra. To begin to elucidate the molecular mechanisms underpinning the ability of Nautella sp. R11 to colonize, invade and induce bleaching of D. pulchra, we sequenced and analyzed its genome. The genome encodes several factors such as adhesion mechanisms, systems for the transport of algal metabolites, enzymes that confer resistance to oxidative stress, cytolysins, and global regulatory mechanisms that may allow for the switch of Nautella sp. R11 to a pathogenic lifestyle. Many virulence effectors common in phytopathogenic bacteria are also found in the R11 genome, such as the plant hormone indole acetic acid, cellulose fibrils, succinoglycan and nodulation protein L. Comparative genomics with non-pathogenic Roseobacter strains and a newly identified pathogen, Phaeobacter sp. LSS9, revealed a patchy distribution of putative virulence factors in all genomes, but also led to the identification of a quorum sensing (QS) dependent transcriptional regulator that was unique to pathogenic Roseobacter strains. This observation supports the model that a combination of virulence factors and QS-dependent regulatory mechanisms enables indigenous members of the host alga's epiphytic microbial community to switch to a pathogenic lifestyle, especially under environmental conditions when innate host defence mechanisms are compromised.
authors.affiliation: The Centre for Marine Bio-Innovation (CMB), University of New South Wales, Sydney, Australia.
authors.forename: Neil
authors.initials: N
authors.lastname: Fernandes
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Case
authors.forename: Sharon R
authors.initials: SR
authors.lastname: Longford
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Seyedsayamdost
authors.forename: Peter D
authors.initials: PD
authors.lastname: Steinberg
authors.forename: Staffan
authors.initials: S
authors.lastname: Kjelleberg
authors.forename: Torsten
authors.initials: T
authors.lastname: Thomas
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D016678:Genome; D016680:Genome, Bacterial; D013058:Mass Spectrometry / Q000379:methods; D010802:Phylogeny; D053038:Quorum Sensing / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D000461:Rhodophyta / Q000378:metabolism*; D041904:Roseobacter / Q000235:genetics / Q000378:metabolism; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D012336:RNA, Ribosomal, 16S; D037521:Virulence Factors