Degenerate primed randomly amplified polymorphic DNA (DP-RAPD) fingerprinting of bacteriophages of Vibrio harveyi from shrimp hatcheries in Southern India

Abstract

Vibrio harveyi is a significant pathogen of shrimp. Seventy-six bacteriophages infecting luminescent V. harveyi were isolated from a total of 194 water samples drawn from various sources of shrimp hatcheries located in South East coast and Andaman island of India. Degenerate primed randomly amplified polymorphic DNA (DP- RAPD) fingerprinting of these bacteriophages was carried out to determine their genetic relatedness. Similarity matrix based on Dice coefficient followed by construction of dendrogram by unweighted pair group method with arithmetic averages (UPGMA) revealed 12 major clusters. One phage was randomly selected from each of these major clusters for transmission electron microscopic observations. Eleven of them had an icosahedral head (46-115 nm) with a long non-contractile tail (132-329 nm), belonging to the Siphoviridae family and two phages had a short tail (15-27 nm), belonging to the family Podoviridae. The phylogenetic analysis of the phages using DP-RAPD fingerprinting correlated to some extent to the phenotypic nature of the host specifically with regard to sucrose fermentation and source of isolation. However, phages specifically infecting V. harveyi and those belonging to different families did not cluster together in the DP-PCR cluster analysis. Hence, the genetic diversity of phages infecting same host with respect to phenotypic difference was revealed by the DP-RAPD applied in this study.