title: Characterization of a novel and genetically different small infective variant of Piscirickettsia salmonis.
abstract: We report a novel genetically different small infective variant of the fish pathogen Piscirickettsia salmonis (sP.s). sP.s variants were recovered both from ageing post-infected CHSE-214 culture cells as well as from naturally infected fish. The ITS region of sP.s variants, although sharing a common core sequence, is different from the ITS of the prototype strain LF-89 from which they originate. Thus, sP.s can be selectively amplified with sequence-specific discriminatory set of PCR primers. Transcriptionally, sP.s are fully active as shown by reverse transcription PCR analysis. Immunologically, sP.s is specifically recognized by antibodies against standard P. salmonis. Structurally, atomic force microscopy shows that sP.s. is well below (<0.2microm) the standard range size described for this pathogen (0.5-1.5microm). Functionally, although sP.s is infective their in vitro progeny is a hundred percent identical to the LF-89 prototype strain. In summary sP.s, represent selectable infective variants of the LF-89 strain and not new strains, probably resulting from a survival strategy of the bacteria in response to limiting growth conditions. In this frame, sP.s could be responsible of horizontal infection of fish in the field.
authors.affiliation: Laboratorio de Genética e Inmunología Molecular, Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2950, Valparaíso, Chile.
authors.forename: M
authors.initials: M
authors.lastname: Verónica Rojas
authors.forename: Jorge
authors.initials: J
authors.lastname: Olivares P
authors.forename: Rodrigo
authors.initials: R
authors.lastname: del Río
authors.forename: Sergio H
authors.initials: SH
authors.lastname: Marshall
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology*; D014644:Genetic Variation; D018625:Microscopy, Atomic Force; D008969:Molecular Sequence Data; D053522:Piscirickettsia / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000648:ultrastructure; D016133:Polymerase Chain Reaction / Q000379:methods; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D012474:Salmon / Q000382:microbiology*; D016415:Sequence Alignment; D014158:Transcription, Genetic
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D012329:RNA, Bacterial; D012333:RNA, Messenger