The results indicate that replication and transcription of the Gaussia and firefly luciferase genome segments are in competition with each other. If so the observed inhibitory effect of cotransfection of the Gaussia luciferase construct on the firefly luciferase expression level is expected to depend on the ratio of the transfected reporter constructs. As shown in Figure 2E , this is indeed the case. Lowering the amount of co-transfected Gaussia as well as increasing the amount of co-transfected firefly luciferase reporter plasmid shifted the balance in the competition between the firefly and Gaussia luciferase genome segments as judged from the increased normFluc/Gluc ratio (Fig. 2E ). This increased ratio resulted from altered firefly rather than Gaussia luciferase expression levels ( Fig. S2A and B ). From these results we conclude that the Gaussia luciferase genome segment is much more efficiently replicated and transcribed than its firefly luciferase counterpart, the latter of which is outcompeted by the presence of the former.