AUTHOR=Ottaviani Donatella , Pieralisi Silvia , Rocchegiani Elena , Latini Mario , Leoni Francesca , Mosca Francesco , Pallavicini Alberto , Tiscar Pietro Giorgio , Angelico Gabriele 

TITLE=Vibrio parahaemolyticus-specific Halobacteriovorax From Seawater of a Mussel Harvesting Area in the Adriatic Sea: Abundance, Diversity, Efficiency and Relationship With the Prey Natural Level

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01575

DOI=10.3389/fmicb.2020.01575

ISSN=1664-302X

ABSTRACT=<p>This research aimed to study the abundance and molecular diversity of <italic>Vibrio parahaemolyticus</italic>-specific <italic>Halobacteriovorax</italic> strains isolated from seawater of the Adriatic Sea and the relationship between predator and prey abundances. Moreover, predator efficiency of the <italic>Halobacteriovorax</italic> isolates toward <italic>V. parahaemolyticus</italic> and <italic>Vibrio cholerae</italic> non-O1/O139 strains was tested. <italic>V. parahaemolyticus</italic> NCTC 10885 was used as primary host for the isolation of <italic>Halobacteriovorax</italic> from seawater by the plaque assay. Molecular identification was performed by PCR detection of a fragment of the 16S rRNA gene of the <italic>Halobacteriovoraceae</italic> family members. Moreover, 700 bp PCR products were sequenced and compared between them and to clones described for other sampling sites. <italic>Vibrio</italic> counts were performed on TCBS agar from 100 ml of filtered water samples and presumptive colonies were confirmed by standard methods. Predatory efficiency of <italic>Halobacteriovorax</italic> isolates was tested by monitoring abilities of 3-day enrichments to form clear lytic halos on a lawn of <italic>Vibrio</italic> preys, by the plaque assay. Out of 12 seawater samples monthly collected from June 2017 to May 2018, 10 were positive for <italic>V. parahaemolyticus</italic> specific <italic>Halobacteriovorax</italic> with counts ranging from 4 to 1.4 × 10<sup>3</sup> PFU per 7.5 ml. No significant relationship was found between <italic>Halobacteriovorax</italic> and <italic>Vibrio</italic> abundances. The 16SrRNA sequences of our <italic>Halobacteriovorax</italic> strains, one for each positive sample, were divided into three lineages. Within the lineages, some sequences had 100% similarity. Sequence similarity between lineages was always &lt;94.5% suggesting that they may therefore well belong to three different species. All <italic>Halobacteriovorax</italic> isolates had the ability to prey all tested <italic>Vibrio</italic> strains. Additional research is necessary to assess whether stable strains of <italic>Halobacteriovorax</italic> are present in the Adriatic Sea and to understand the mechanisms by which <italic>Halobacteriovorax</italic> may modulate the abundance of <italic>V. parahaemolyticus</italic> and other vibrios in a complex marine ecosystem.</p>