Bactofilins are essential spatial organizers of peptidoglycan insertion in the Lyme disease spirochete Borrelia burgdorferi

The Lyme disease spirochete Borrelia burgdorferi has a distinctive pattern of growth. Newly born cells elongate by primarily inserting peptidoglycan at mid-cell, while in longer cells, additional insertion sites form at the one-quarter and three-quarter positions along the cell length. It is not known how peptidoglycan insertion is concentrated at these locations in B. burgdorferi . In other bacteria, multi-protein complexes are known to synthesize new peptidoglycan, and are often organized by cytoskeletal proteins. We show here that B. burgdorferi ’s zonal concentration of peptidoglycan insertion requires BB0538 (BbbF) and BB0245 (BbbG), two members of the bactofilin class of cytoskeletal proteins. Bactofilin depletion redistributed peptidoglycan insertion along the cell length. Prolonged bactofilin depletion arrested growth in culture and induced extensive cell blebbing, indicating that B. burgdorferi bactofilins are essential for viability. Fluorescent protein fusions of BbbF and BbbG localized to new zones of growth before peptidoglycan insertion occurred at these sites, with BbbG localization dependent on BbbF. Our results show that BbbF and BbbG direct the spatial patterning of new peptidoglycan insertion in B. burgdorferi .