Phages Infecting Vibrio vulnificus Are Abundant and Diverse in Oysters ( Crassostrea virginica ) Collected from the Gulf of Mexico

Abstract

ABSTRACT Phages infecting Vibrio vulnificus were abundant (>10 4 phages g of oyster tissue −1 ) throughout the year in oysters ( Crassostrea virginica ) collected from estuaries adjacent to the Gulf of Mexico (Apalachicola Bay, Fla.; Mobile Bay, Ala.; and Black Bay, La.). Estimates of abundance ranged from 10 1 to 10 5 phages g of oyster tissue −1 and were dependent on the bacterial strain used to assay the sample. V. vulnificus was near or below detection limits (<0.3 cell g −1 ) from January through March and was most abundant (10 3 to 10 4 cells g −1 ) during the summer and fall, when phage abundances also tended to be greatest. The phages isolated were specific to strains of V. vulnificus , except for one isolate that caused lysis in a few strains of V. parahaemolyticus . Based on morphological evidence obtained by transmission electron microscopy, the isolates belonged to the Podoviridae , Styloviridae , and Myoviridae , three families of double-stranded DNA phages. One newly described morphotype belonging to the Podoviridae appears to be ubiquitous in Gulf Coast oysters. Isolates of this morphotype have an elongated capsid (mean, 258 nm; standard deviation, 4 nm; n = 35), with some isolates having a relatively broad host range among strains of V. vulnificus . Results from this study indicate that a morphologically diverse group of phages which infect V. vulnificus is abundant and widely distributed in oysters from estuaries bordering the northeastern Gulf of Mexico.