In vitro determination of essential genes required by Streptococcus uberis to grow in a complex biological media relating to intramammary infection

<i>Streptococcus uberis</i> is a leading cause of bovine mastitis, a disease of significant economic impact to the dairy industry. Understanding the genetic factors essential for bacterial survival in milk and during intramammary infection is crucial for developing effective interventions and reducing the reliance on antimicrobials. Some studies have looked at how certain genes affect the growth and spread of <i>S. uberis</i> in milk, but they have mostly ignored the impact of inflammation and increased blood vessel permeability.Cultures in milk containing serum subsequently exhibited accelerated growth rate and yield in proportion to the concentration of serum, potentially highlighting a role in bacterial proliferation. Using high-throughput transposon insertion sequencing, genes essential for <i>S. uberis</i> to grow in milk and milk supplemented with serum, mimicking conditions of an inflamed mammary gland, were identified. A total of 359 genes associated with growth in milk and 460 genes required in milk supplemented with serum were identified and correlated with metabolic pathways crucial for the survival of <i>S. uberis</i> in these phenotypes. Individual genes associated with carbohydrate metabolism, lipid metabolism and protein synthesis were significantly enriched in both conditions; however, there were a high number of genes with an unknown function, highlighting the poor characterization of the <i>S. uberis</i> genome. There were also numerous hypothetical genes which hint at a putative role in bacterial proliferation, presenting opportunities for further research.