Molecular and morphological characterization of Rhodobacter sphaeroides 7001 bacteriophages øR3-PR6 and øR3-PR7

Abstract

Bacteriophages are ubiquitous viral particles found in most environments, such as oceans, rivers, and soil. This wide distribution makes phages one of the most abundant viral types on the planet. Bacteria are outnumbered by phages by a factor of 10 to 1, totaling a population close to c capable of conducting an estimated a 1023 infections per seconds globally. Bacteriophages have been widely studied, especially in gram-positive and delta-proteobacteria. However, information regarding phages belonging to the Rhodospirillaceae family is scarce. The øR3-PR1-5 are bacteriophages capable of infecting Rhodobacter sphaeroides 7001 and was originally isolated by Rojas et al., 2009 in different freshwater bodies in southwest Puerto Rico. Since the isolations, two more bacteriophages specific for a restriction system mutant of Rhodobacter sphaeroides have been isolated in aquatic environments int northern part of the Island and have been named øR3-PR6 and øR3-PR7. This study describes molecularly and morphologically both phages and compare them with the other five isolated Rhodophages (bacteriophages that infect Rhodobacter spp.) in Puerto Rico. Transmission electron microscopy revealed that both phages differ in morphology, capsid and tail size. Furthermore, morphological analysis suggests both phages belong to the Caudovirales order whereas øR3-PR6-7 seems to be affiliated to the Siphoviridae family. Restriction enzyme digestion analyses using ClaI and HindIII shows that these phages present distinctive banding pattern. Estimated genome size for each phage is about 53.236 KbP in øR3-PR6 and 51.865 KbP in øR3-PR7. Total genome DNA sequencing and subsequent Rapid Annotation using Subsystem Technology (RAST) analysis demonstrated that Rhodophages share various putative proteins amongst themselves and with Rhizobium phage vB_Rgls_P106B. This study expands on the limited knowledge available for Rhodophages isolated outside of the United States and provides information applicable to the advancement of phage mediated genetic transfer studies across the Rhodospirillaceae as well as a deeper understanding of the Siphoviridae family.