Prokaryotes carry multiple distinct anti-viral defense systems. However, the impact of carrying a multitude of defense systems on virus resistance remains unclear, especially in a clinical context. Using a collection of antibiotic-resistant clinical strains of Pseudomonas aeruginosa and a broad panel of phages, we demonstrate that intracellular defense systems are major determinants of phage host range and that overall phage resistance scales with the number of defense systems in the bacterial genome. We show that individual defense systems are specific to certain phage types, including Jumbo phages, and that the accumulation of defense systems with distinct specificities results in panphage resistant phenotypes. Accumulation of defense systems is aided by their localization within mobile phage defense elements facilitating horizontal gene transfer. Overall, we show that panphage resistant, defense-accumulating strains of P. aeruginosa with up to 19 phage defense systems already occur in the clinic, which may impact the development of phage-based therapeutics.

tRNAs in bacteriophage genomes are widespread across bacterial host genera, but their exact function has remained unclear for more than 50 years. Several hypotheses have been proposed, and the most widely accepted one is codon compensation, which suggests that phages encode tRNAs that supplement codons that are less frequently used by the host. Here, we combine several observations and propose a new hypothesis that phage-encoded tRNAs counteract the tRNA-depleting strategies of the host using enzymes such as VapC, PrrC, Colicin D, and Colicin E5 to defend from viral infection. Based on mutational patterns of anticodon loops of tRNAs encoded by phages, we predict that these tRNAs are insensitive to host tRNAses. For phage-encoded tRNAs targeted in the anticodon itself, we observe that phages typically avoid encoding these tRNAs. Further supporting the hypothesis that phage tRNAs are selected to be insensitive to host anticodon nucleases. Altogether our results support the hypothesis that phage-encoded tRNAs have evolved to be insensitive to host anticodon nucleases.

tRNAs in bacteriophage genomes are widespread across bacterial genera, but their exact function has remained unclear for more than 50 years. Multiple hypotheses have been proposed, with the most established being codon compensation, where codons more rarely used by the host but necessary for the phage are supplemented by tRNAs encoded by the phage. Here, we combine several observations and propose a new hypothesis that phage-encoded tRNAs are a means to counteract the tRNA-depleting strategies of the host to defend from viral infection. Based on mutational patterns of tRNA anticodon loops, we predict that phage tRNAs are insensitive to the host tRNAses. For tRNAs targeted in the anticodon itself, we observe phage counter-selection of targeted isoacceptor tRNAs, further supporting the hypothesis that phage tRNAs are selected to be insensitive to host anticodon nucleases. Importance The presence of tRNAs in phages was discovered more than 50 years ago and their function has been debated ever since. Here, we propose that phage tRNAs counteract the tRNAse activities of the host, which may represent a depletion strategy of essential cellular components to stop translation and thereby phage infection.

Spondyloarthritis (SpA) patients suffer from joint inflammation resulting in tissue damage, characterized by the presence of numerous neutrophils in the synovium and synovial fluid (SF). As it is yet unclear to what extent neutrophils contribute to the pathogenesis of SpA, we set out to study SF neutrophils in more detail. We analyzed the functionality of SF neutrophils of 20 SpA patients and 7 disease controls, determining ROS production and degranulation in response to various stimuli. In addition, the effect of SF on neutrophil function was determined. Surprisingly, our data show that SF neutrophils in SpA patients have an inactive phenotype, despite the presence of many neutrophil-activating stimuli such as GM-CSF and TNF in SF. This was not due to exhaustion as SF neutrophils readily responded to stimulation. Therefore, this finding suggests that one or more inhibitors of neutrophil activation may be present in SF. Indeed, when blood neutrophils from healthy donors were activated in the presence of increasing concentrations of SF from SpA patients, degranulation and ROS production were dose-dependently inhibited. This effect was independent of diagnosis, gender, age, and medication in the patients from which the SF was isolated. Treatment of SF with the enzyme hyaluronidase strongly reduced the inhibitory effect of SF on neutrophil activation, indicating that hyaluronic acid that is present in SF may be an important factor in preventing SF neutrophil activation. This finding provides novel insights into the role of soluble factors in SF regulating neutrophil function and may lead to the development of novel therapeutics targeting neutrophil activation via hyaluronic acid or associated pathways.