Photosynthetic genes in viral populations with a large genomic size range from Norwegian coastal waters.

This study reports the diversity of uncultured environmental viruses harbouring photosynthetic genes (psbA and psbD) in samples from cold seawater (latitude above 60 degrees ). The viral community in coastal Norwegian waters was separated according to genome size using pulse field gel electrophoresis. Viral populations within a wide genome size range (31-380 kb) were investigated for the presence of the psbA and psbD genes using PCR, combined with cloning and sequencing. The results show the presence of photosynthetic genes in viral populations from all size ranges. Thus, valuable information could be obtained about the size class to which viral particles that encode photosynthesis genes belong. The wide genomic size range detected implies that a different cyanophage profile has been observed than has been reported previously. Thus, the method of phage gene detection applied here may represent a truer picture of phage diversity in general or that there is a larger range of size profile for viruses with psbA and psbD in higher latitudes than for the better-studied lower latitudes. Alternatively, a picture of diversity based on a different set of biases than that from either isolation-based research or from conventional metagenomic approaches may be observed.