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Bacteriophages are recognized as major mortality agents of microbes, among them intracellular marine rickettsiales-like bacteria. Recently, a phage hyperparasite of Candidatus Xenohaliotis californiensis (CXc) has been described. This bacterium is considered the causal agent of Withering Syndrome (WS) which is a chronic and potentially lethal disease of abalone species from California, USA and the peninsula of Baja California, Mexico. This hyperparasite which infects CXc could be used as a biocontrol agent for WS. Therefore, it is necessary to obtain genomic information to characterize this phage. In this study, the first complete genome sequence of a novel phage, Xenohaliotis phage (pCXc) was determined. The complete genome of pCXc from red abalone (Haliotis rufescens) is 35,728 bp, while the complete genome of pCXc from yellow abalone (Haliotis corrugata) is 35,736 bp. Both phage genomes consist of double-stranded DNA with a G + C content of 38.9%. In both genomes 33 open reading frames (ORFs) were predicted. Only 10 ORFs encode proteins that have identifiable functional homologues. These 10 ORFs were classified by function, including structural, DNA replication, DNA packaging, nucleotide transport and metabolism, life cycle regulation, recombination and repair, and additional functions. A PCR method for the specific detection of pCXc was developed. This information will help to understand a new group of phages that infect intracellular marine rickettsiales-like bacteria in mollusks. [ABSTRACT FROM AUTHOR]

Candidatus Xenohaliotis californiensis ( C Xc) is a Rickettsiales-like prokaryote that is considered the causal agent of Withering Syndrome (WS), a chronic disease of abalone, from the west coast of North America and it is listed by the International Organization for Animal Health (OIE) as a reportable agent due to its pathogenicity. This bacterium in red abalone Haliotis rufescens , black abalone Haliotis cracherodii , and yellow abalone Haliotis corrugata from California, US and Baja California, Mexico has been found to be infected by a bacteriophage. To date, there is no information on the epizootiology of C Xc and its bacteriophage in natural populations of abalone; furthermore, it is unknown if the bacteriophage was also present in C Xc infecting blue abalone Haliotis fulgens . The objective of this study was to determine the distribution, prevalence and intensity of C Xc, as well as to determine the distribution and prevalence of the bacteriophage and to study interactions between host sex and hyperparasitism in blue abalone and yellow abalone. Tissue samples were obtained from seven localities where the commercial capture of wild abalone is carried out. Samplings were conducted throughout the 2012–2013 capture seasons and a total of 182 blue abalone and 170 yellow abalone were obtained. The prevalence and intensity of C Xc and the prevalence of the bacteriophage were determined by histology. The identity of C Xc was confirmed by PCR, product sequence analysis and in situ hybridization while the identity of the bacteriophage was corroborated by TEM. The prevalence of C Xc infected and uninfected by the bacteriophage was 80% in blue abalone and 62% in yellow abalone. Low infection intensities were found in 86% of blue abalone and 82% of yellow abalone. Infection intensity was significantly higher in undifferentiated yellow abalone. The bacteriophage in C Xc showed a prevalence of 22% and 31% in blue abalone and yellow abalone respectively. These results show that C Xc and its bacteriophage are widely distributed in the peninsula of Baja California and that they are well established in natural populations of blue abalone and yellow abalone. Additionally, this data constitutes the first record of a bacteriophage in blue abalone. [ABSTRACT FROM AUTHOR]