Bacteriovorax were quantified in US Atlantic, Gulf, and Pacific seawater to determine baseline levels of these predatory bacteria and possible seasonal fluctuations in levels. Surface seawater was analyzed monthly for 1 year from Kailua-Kona, Hawaii; the Gulf Coast of Alabama; and four sites along the Delaware Bay. Screening for Bacteriovorax was performed on lawns of V. parahaemolyticus host cells. Direct testing of 7.5？mL portions of seawater from the Atlantic, Pacific, and Gulf coasts gave mean annual counts ≤12.2 PFU. Spikes in counts were observed at 3 out of 4 sites along the Delaware Bay 1 week after Hurricane Sandy. A comparison of summer versus winter counts showed significantly more Bacteriovorax ( ) in the Delaware Bay during the summer and significantly more ( ) in the Gulf during the winter, but no significant seasonal differences ( ) for Hawaiian seawater. Bacteriovorax counts only correlated with seawater salinity and temperature at one Delaware site ( and , resp.). There was a relatively strong negative correlation between temperature and Bacteriovorax levels ( ) for Gulf seawater. Selected isolates were sequenced and identified by phylogenetic analysis as Bacteriovorax clusters IX, X, XI, and XII. 1. Introduction Vibrio parahaemolyticus and Vibrio vulnificus are important foodborne pathogens associated with the consumption of fish and shellfish, especially oysters, which have long been known to bioconcentrate vibrios within their edible tissues [1, 2]. Vibrio vulnificus also causes life-threatening illness from wound infections acquired in the marine environment [3]. Pathogenic vibrios show seasonal predilection in seawater and shellfish, with high counts during warmer months and low to negligible counts during the colder months [2, 4, 5]. Recently, we showed that naturally occurring Bdellovibrio and like organisms (BALOs) from coastal seawater significantly reduced the levels of V. parahaemolyticus and V. vulnificus in seawater and V. parahaemolyticus in seawater and oysters [6]. Among the BALOs are marine and terrestrial forms, with the marine forms associated with Bacteriovorax, which are exclusively saltwater predators [7, 8]. Bacteriovorax have shown preferential predation toward V. parahaemolyticus when compared to a broad range of potential host bacteria [9–12]. This suggests that Bacteriovorax may invade and kill V. parahaemolyticus in seawater more efficiently than other bacterial pathogens. The life cycle of Bacteriovorax and other BALOs usually involve intracellular invasion of and replication within a host cell, although
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