International Journal of Biotechnology Research Vol. 3(3), pp. 035-044, April 2015 Available online at http://academeresearchjournals.org/journal/ijbr ISSN 2328-3505 ©2015 Academe Research Journals Full Length Research Paper Molecular characterization and phylogenetic analysis of Family Adenoviridae from marine environment as inferred from the hexon protein gene Dhirendra Kumar Singh and Swapna P. Antony* National Centre for Aquatic Animal Health, Cochin University of Science and Technology, Cochin-682016, Kerala, India. Accepted 6 April, 2015 The marine environment, covering 70% of the planet’s surface, is estimated to contain 10 30 viruses. Despite their great importance in the marine environment, virtually very little is known about marine viral biodiversity or the evolutionary relationships of marine and non-marine viruses. The present study is aimed at molecular characterization and phylogenetic analysis of the viral Family Adenoviridae from the marine environment, based on the hexon protein gene. Briefly, 50 L of sea water was purified and concentrated by a combination of tangential flow filtration, flocculation and centrifugation. Metagenomic DNA was extracted from the viral particles and PCR amplification was performed using specific primers designed for hexon protein gene of adenoviruses. Positive amplicons were cloned and sequenced. Sequences were analysed using GeneTool, BioEdit, ExPASy, ClustalW, GeneDoc and Mega 5.0 programmes. Partial hexon protein amplicon of 254 bp fragment encoding hexon protein of 84 amino acids could be recovered from the metagenomc viral DNA (KJ958986). Phylogenetic relationship of the newly identified hexon protein gene was constructed employing neighbour joining method based on already available hexon protein sequences in GenBank. The results of phylogenetic analysis confirmed the basal placement of the newly identified hexon protein gene in the Adenoviridae family. The present study shows that the newly identified adenovirus from marine environment is more closely related to adenoviruses isolated from Ovine and Bovine sources than to other adenoviruses from human sources. The present study provides a clearer insight into adenoviridae present in the marine system. Key words: Adenovirus, marine viruses, hexon protein, metagenomics, phylogeny. INTRODUCTION Viruses are the smallest sub-microscopic forms of life, attacking all organisms on the earth and the most abundant entity in sea water. Currently, best estimation of viral particles indicates concentrations of ~10 6 viruses ml -1 of surface seawater, ~3×10 6 viruses ml -1 in the deep sea to ~10 8 viruses ml -1 in productive coastal waters till now, the total estimation of viruses is about ~10 30 in the oceans (Bergh et al., 1989; Suttle, 2005; Rohwer and Barott, 2013). With higher abundance of viruses it is also seen that their genome sequences are also remarkably diverse. Due to lack of standard culture techniques, our knowledge about viral world is limited (Fuhrman and Campbell, 1998; Paul and Sullivan, 2005). To overcome these difficulties, new culture-independent approaches came into light which are mainly based on molecular tools and done by amplification of conserved gene present in viruses (Nicholas and Paul, 2011). Metagenomics is one of the prominent culture- independent approaches that have revealed an incredible amount of viral genetic diversity, particularly in the marine *Corresponding author. E-mail: swapnapantony@gmail.com, swapnapantony@cusat.ac.in. Tel: + 914842381120; Fax: + 914842381120.