The <i>lp17</i> regulatory elements in <i>Borrelia burgdorferi</i> : a novel small RNA impacts gene expression and mammalian infection

<i>Borrelia burgdorferi</i>, the tick-borne agent of Lyme disease, is the causative agent of one of the most prevalent vector-borne infections in many regions worldwide. Despite extensive study, the biological functions of many of its protein and small RNA (sRNA) products remain poorly defined. Here, we confirm and extend the regulatory roles of the linear plasmid (<i>lp</i>)17-encoded protein BBD18 and the sRNA <i>SR0736</i> (<i>ittA</i>) in spirochete infectivity. Importantly, we identify a previously unrecognized regulatory function for an adjacent sRNA, <i>SR0735</i>, underscoring lp17 as a key regulatory region in <i>B. burgdorferi</i>. Together, our findings highlight the <i>bbd18</i> locus and its surrounding sRNA elements as an independent, multilayered regulatory module that controls gene products, including those required for mammalian infection. Defining how these three regulators shape gene expression and virulence will reveal new mechanisms underlying Lyme disease pathogenesis and may inform the development of new strategies to prevent this widespread illness.