Seasonal Levels of theVibrioPredatorBacteriovoraxin Atlantic, Pacific, and Gulf Coast Seawater

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 ≤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 (P ≤ 0.0001) in the Delaware Bay during the summer and significantly more (P ≤ 0.0001) in the Gulf during the winter, but no significant seasonal differences (P > 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, resp.). There was a relatively strong negative correlation between temperature and Bacteriovorax levels (r = −0.585) for Gulf seawater. Selected isolates were sequenced and identified by phylogenetic analysis as Bacteriovorax clusters IX, X, XI, and XII.

Purification and Host Specificity of Predatory Halobacteriovorax Isolates from Seawater

“…Four previously described isolates of Halobacteriovorax (G3, OR7, OS1, and S11) were used (23). Strain G3 was isolated from seawater from the Gulf Coast of Alabama, and the others were from seawater from the Delaware Bay.…”

“…All vibrios were enriched in Difco Luria-Bertani (LB) broth (Becton, Dickinson and Company, Sparks, MD) supplemented with 2% NaCl (3% NaCl total), whereas non-Vibrio bacteria were grown in LB broth which contained 1% NaCl. Seawater was obtained from Scotton Landing, on the St. Jones River in Frederica, DE, 6.2 km from the Delaware Bay (20,23), and was used to screen for Halobacteriovorax strains against E. coli and S. Typhimurium. This location was affected by the tide and contained water that was a mixture of fresh river water and seawater.…”

“…The Halobacteriovorax strains showed high host species specificity in that they were capable of killing V. parahaemolyticus strains other than O3:K6 but were unable to kill V. vulnificus, V. alginolyticus, several strains of E. coli, or S. Typhimurium. Interestingly, all four Halobacteriovorax isolates exhibited the same specificity profiles, even though G3 and OR7 were phylogenetically defined as members of cluster IX while OS1 and S11 were from cluster XII (23).…”

“…Predatory bacteria represent a potential green technology that may prove useful in controlling antibiotic-resistant bacteria in clinical, environmental, and industrial settings. The size differences between Halobacteriovorax and V. parahaemolyticus are substantial: attack-phase Halobacteriovorax strains are approximately 0.2 to 0.4 m in width (22) and approximately 0.75 to 1 m in length (taken from figures of Richards et al [20,23]), while V. parahaemolyticus is larger (roughly 0.5 to 0.8 m in width and 1.4 to 2.4 m in length). Vibrios are, however, capable of entering a viable but nonculturable state where they shrink in size and become rounded to produce minicells, a state often induced by low temperatures or starvation (24)(25)(26)(27).…”

Halobacteriovorax, an underestimated predator on bacteria: potential impact relative to viruses on bacterial mortality

“…Within the periplasm the predator feeds and grows on the prey's cellular material, multiplies by segmenting, and lyses the remaining prey cell wall, releasing newly formed predators into the environment to repeat the cycle (Starr and Baigent 1966). Although relatively low in abundance, typically 0-50 plaque-forming units (PFU) per ml (Taylor et al, 1974;Varon and Shilo, 1980;Richards et al, 2013), compared with viruses, BALOs are ubiquitous globally. They have been isolated from oceans, seas, estuaries, salt lakes, ponds, freshwater systems and soils (Taylor et al, 1974;Williams, 1979;Sutton and Besant, 1994;Pineiro et al, 2004;Davidov et al, 2006;Pineiro et al, 2007).…”