Isolation and Characterization of Bacteriophages from the Arctic

Abstract

Bacteriophages are viruses that specifically infect bacteria. These obligate intracellular parasites are Earth's most copious, ubiquitous, and genetically diverse (unexplored) biological entities. Organisms in the Arctic environment constantly experience extreme conditions, therefore life in the Arctic evolved different specialized strategies and molecules to survive which offers huge opportunities to prospect for novel bioactive compounds and potential industrial applications or products for different purposes. In the Arctic, biological resources are little studied, and we know just a little bit of them. This study aims to isolate and characterize various phages from the Arctic Sea and sewage samples collected from waste-water treatment plants (WWTP) in Tromsø, Norway (Arctic). Host bacteria used were isolated from the Arctic Sea and belong to the following genera: Vibrio (2 strains), Flavobacterium, Shewanella, and Maribacter, while Escherichia coli K12 (laboratory strain) was used for isolating phages from sewage samples. Marine bacteria were cultured at 4°C whereas E. coli was cultivated at 37°C. Phage isolation was made by preparation of enrichment cultures and plating using the double agar layer (DAL) method. Morphological characterization was performed using negatively stained transmission electron microscopy (TEM). This study found that while marine phages were present in the samples, but they were challenging to grow and further characterize. Based on plaque assay, phages were found in three marine Arctic hosts (none in Shewanella). However, five coliphages were successfully isolated and purified from the sewage samples, and their titer was determined. The highest titer was estimated at 8 × 1010 pfu/ml for phage Ec42_SH23 followed by the lowest 2 × 1010 in Ec41_SH23 phage. The TEM analysis revealed that the isolated phages belonged to the caudovirus group, which is known for its long, short, and contractile or non-contractile tails according to the International Committee on Taxonomy of Viruses (ICTV). Moreover, the phage genome was extracted from the isolated coliphages, although it has not been sequenced yet. These findings suggest that the Arctic may be a potential source of novel phages with unique features.

Keywords: Arctic Bacteriophage, Marine Bacteria, Sewage, TEM, Caudovirus