The alternative sigma factor RpoS in
Borrelia burgdorferi
, the etiological agent of Lyme disease, has long been postulated to regulate virulence-associated genes other than
ospC
and
dbpA
. Here, we demonstrate that
bb0563
, a gene encoding a hypothetical protein, is regulated by RpoS and contributes to the optimal infectivity of
B. burgdorferi
.