Queuosine modification mediates cold-active growth in Shewanella glacialimarina

ABSTRACT Efficient protein synthesis in cold-active bacteria requires precise coordination within the translation machinery to overcome the kinetic challenges imposed by growth at near-freezing temperatures (< 5 °C). Post-transcriptional modifications (PTMs) on transfer RNA (tRNA)—particularly those located at the wobble position 34—are central to this coordination as they regulate decoding speed and fidelity. Here, we show that queuosine (Q) modification in the cold-active marine bacterium Shewanella glacialimarina TZS-4 T is dynamically regulated in response to bacterial growth and environmental conditions. Importantly, we demonstrate that Q levels are modulated in a tRNA isoacceptor-specific manner during cold-active growth, while Q-deficiency produces a cold-sensitive phenotype that underscores the functional importance of Q modification. Proteomic analysis of the Q-deficient Δ tgt mutant revealed that tRNA His Q-hypomodification activates the histidine biosynthesis pathway, whereas the concomitant phosphate-starvation-like response reflects a general consequence of global disruption of Q-modified tRNAs. Consequently, we propose a model where Q modification maintains efficient codon decoding and protein quality control at near-freezing temperatures, whereas loss of Q destabilizes codon decoding and ultimately compromises protein homeostasis.