Bacteriophages are an integral component of the evolution of bacteria through population control, spreading of genetic material by horizontal gene transfer, and introducing genetic novelty through the selection for resistance. Bacteriophage-host interactions have been the basis on which many biotechnological tools were discovered, such as restriction enzymes and CRISPR-Cas9. It has been known for several decades that phage T4 encodes tRNAs, but more recently, we have found that about 20% of fully sequenced phage genomes also encode tRNAs. Yet why this is the case remains unknown. The main hypothesis, the Codon Usage Bias Hypothesis (CUBH), suggests that differences between bacteriophage and host in codon choice necessitates that bacteriophage encode their own tRNAs to complement host tRNAs. Here we show that codon usage bias does not explain the presence of tRNAs in phage genomes. Instead, through experiments in T4 and E. coli, we show preliminary evidence that tRNAs are involved in host-range by reducing the rate at which spontaneous phage resistance mutants arise. We are currently investigating the mechanistic basis for the control of host-range by tRNAs in this model system.