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Title: Seasonal levels of the Vibrio predator Bacteriovorax in Atlantic, Pacific and Gulf Coast Seawater

Author
item Richards, Gary
item Watson, Michael
item BOYD, FIDELMA - University Of Delaware
item BURKHARDT III, WILLIAM - Us Food & Drug Administration (FDA)
item LAU, RONALD - Kona Coast Shellfish, Llc
item Uknalis, Joseph
item FAY, JOHNNA - University Of Delaware

Submitted to: International Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2013
Publication Date: 12/23/2013
Citation: Richards, G.P., Watson, M.A., Boyd, F., Burkhardt Iii, W., Lau, R., Uknalis, J., Fay, J.P. 2013. Seasonal levels of the Vibrio predator Bacteriovorax in Atlantic, Pacific and Gulf Coast Seawater. International Journal of Microbiology. doi:10.1155/2013/375371.

Interpretive Summary: Vibrio bacteria are responsible for illnesses and deaths among unsuspecting consumers of oysters and other shellfish. We previously showed that a marine bacterium known as Bacteriovorax kills vibrios in seawater and shellfish. To examine the natural levels of these Bacteriovorax in seawater, we conducted a year-long study of Bacteriovorax levels in seawater from four sites along the Atlantic Coast (in the Delaware Bay), and one site each from the Gulf Coast (Alabama), and the Pacific Ocean (Kailua-Kona, Hawaii). Levels of Bacteriovorax were detected for most months, with higher counts in the Delaware Bay during the summer and in the Gulf during the winter. Levels in Hawaiian seawater did not show any summer or winter preference. The highest counts in the Delaware Bay occurred immediately after Hurricane Sandy struck the coast, contributing to much runoff and sediment in the waters of the Delaware Bay and its tributaries. There was only limited association between Bacteriovorax counts and seawater salinity. In summary, Bacteriovorax predators of vibrios are present in natural seawater throughout much of the year and are subject to regional differences in levels – levels that cannot be attributed to seawater temperature or salinity alone. These Bacteriovorax are likely to reduce levels of disease-causing vibrios in shellfish, thus a better understanding of factors responsible for increased Bacteriovorax counts in environmental waters may be the key to understanding factors that reduce outbreaks of Vibrio illnesses among consumers of fishery products.

Technical Abstract: 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 lass than or equal to 12.2 PFU. Spikes in counts were observed at 3 of 4 sites along the Delaware Bay 1 week after Hurricane Sandy. A comparison of summer versus winter counts showed significantly more Bacteriovorax (P is less than or equal to 0.0001) in the Delaware Bay during the summer and significantly more (P is less than or equal to 0.0001) in the Gulf during the winter, but no significant seasonal differences (P is greater than 0.05) for Hawaiian seawater. Bacteriovorax counts only correlated with seawater salinity and temperature at one Delaware site (r = 0.79 and r = 0.65, respectively). There was a relatively strong negative correlation between temperature and Bacteriovorax levels (r = -0.585) for Gulf seawater. Selected isolates were identified by phylogenetic analysis as Bacteriovorax clusters IX, X, XI and XII.