Cyanophage tRNAs may have a role in cross-infectivity of oceanic Prochlorococcus and Synechococcus hosts (In collaboration with Prof. Oded Beja)
Marine cyanobacteria of the generaProchlorococcusandSynechococcusare the most abundant photosynthetic prokaryotes in oceanic environments, and are key contributors to global CO2 fixation, chlorophyll biomass and primary production. Cyanophages, viruses infecting cyanobacter-ia, are a major force in the ecology of their hosts. These phages contribute greatly to cyanobacterial mortality, therefore acting as a powerful selective force upon their hosts. Phage reproduction is based on utilization of the host transcription and translation mechanisms; therefore, differences in the GþC genomic content between cyanophages and their hosts could be a limiting factor for the translation of cyanophage genes. On the basis of comprehensive genomic analyses conducted in this study, we suggest that cyanophages of the Myoviridaefamily, which can infect both ProchlorococcusandSynechococcus, overcome this limitation by carrying additional sets of tRNAs in their genomes accommodating AT-rich codons. Whereas the tRNA genes are less needed when infecting their Prochlorococcushosts, which possess a similar GþC content to the cyanophage, the additional tRNAs may increase the overall translational efficiency of their genes when infecting a Synechococcushost (with high GþC content), therefore potentially enabling the infection of multiple hosts.
Enav et al., ISME J. (2011)
Phage codon frequencies compared with the codon frequencies of their hosts for four phage–host interactions: (a) Syn19 compared with NATL2A, a low %GCProchlorococcushost; (b) Syn19 compared with MIT9303, a relatively high %GCProchlorococcus host; (c) Syn19 compared with WH7803, a Synechococcushost; and (d) Syn19 compared with WH8102, a Synechococcushost. Each triangle stands for a specific codon; red triangles correspond to tCC. The regions between the lower and the upper quartile representing the distances of the triangle to the diagonal are shaded in gray.