ABSTRACTLyme disease is the most widely reported vector-borne disease in the United States. Its incidence is rapidly increasing and disease symptoms can be debilitating. The need to understand the biology of the disease agent, the spirocheteBorrelia burgdorferi, is thus evermore pressing. Despite important advances inB. burgdorferigenetics, the array of molecular tools available for use in this organism remains limited, especially for cell biological studies. Here, we adapt a palette of bright and mostly monomeric fluorescent proteins for versatile use and multi-color imaging inB. burgdorferi. We also characterize two novel antibiotic selection markers and establish the feasibility of their use in conjunction with extant markers. Lastly, we describe a set of constitutively active promoters of low and intermediate strengths that allow fine-tuning of gene expression levels. These molecular tools complement and expand current experimental capabilities inB. burgdorferi, which will facilitate future investigation of this important human pathogen. To showcase the usefulness of these reagents, we used them to investigate the subcellular localization of BB0323, aB. burgdorferilipoprotein essential for survival in the host and vector environments. We show that BB0323 accumulates at the cell poles and future division sites ofB. burgdorfericells, highlighting the complex subcellular organization of this spirochete.IMPORTANCEGenetic manipulation of the Lyme disease spirocheteB. burgdorferiremains cumbersome, despite significant progress in the field. The scarcity of molecular reagents available for use in this pathogen has slowed research efforts to study its unusual biology. Of interest,B. burgdorferidisplays complex cellular organization features that have yet to be understood. These include an unusual morphology and a highly fragmented genome, both of which are likely to play important roles in the bacterium’s transmission, infectivity, and persistence. Here, we complement and expand the array of molecular tools available for use inB. burgdorferiby generating and characterizing multiple fluorescent proteins, antibiotic selection markers, and constitutively active promoters of different strengths. These tools will facilitate investigations in this important human pathogen, as exemplified by the polar and midcell localization of the cell envelope regulator BB0323, which we uncovered using these reagents.
Fine Tuning the Optical Properties of Green to Red Photoconvertible Fluorescent Proteins
