AUTHOR=Kostick-Dunn Jessica L. , Izac Jerilyn R. , Freedman John C. , Szkotnicki Lee T. , Oliver Lee D. , Marconi Richard T. 

TITLE=The Borrelia burgdorferi c-di-GMP Binding Receptors, PlzA and PlzB, Are Functionally Distinct

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2018.00213

DOI=10.3389/fcimb.2018.00213

ISSN=2235-2988

ABSTRACT=<p>Cyclic-di-GMP (c-di-GMP) contributes to the regulation of processes required by the Lyme disease (LD) spirochetes to complete the tick-mammal enzootic cycle. Our understanding of the effector mechanisms of c-di-GMP in the <italic>Borrelia</italic> is evolving. While most LD spirochete isolates encode a single PilZ domain containing c-di-GMP receptor designated as PlzA, genome analyses have revealed that a subset encode a second PilZ domain protein (PlzB). The c-di-GMP binding potential of PlzB, and its role in LD spirochete biology, have not been investigated. To determine if PlzB binds c-di-GMP, <italic>plzB</italic> from <italic>B. burgdorferi</italic> isolate ZS7 was PCR amplified, cloned, and recombinant protein generated. PlzB bound c-di-GMP but not other nucleotides, indicating a specific binding interaction. To determine if PlzA and PlzB are functionally synonymous, a series of allelic-exchange gene deletion and <italic>cis</italic>-complemented strains were generated in the <italic>B. burgdorferi</italic> B31 background. <italic>B. burgdorferi</italic> B31-Δ<italic>plzA</italic> was competent to infect <italic>Ixodes scapularis</italic> larvae but not mice when delivered by either needle or tick feeding. <italic>B. burgdorferi</italic> B31-Δ<italic>plzA</italic> also displayed an atypical motility phenotype. Complementation in <italic>cis</italic> of <italic>B. burgdorferi</italic> B31-Δ<italic>plzA</italic> with <italic>plzA</italic> (B31-<italic>plzA</italic> KI) restored wild-type (wt) phenotype. However, a strain complemented in <italic>cis</italic> with <italic>plzB</italic> (B31-<italic>plzB</italic> KI) did not. The data presented here are consistent with an earlier study that demonstrated that PlzA plays an essential role in spirochete survival in the mammalian environment. We add to our understanding of the c-di-GMP regulatory network by demonstrating that while PlzB binds c-di-GMP, it is not functionally synonymous with PlzA. The absence of <italic>plzB</italic> from most strains suggests that it is not required for survival. One possibility is that cells that harbor both PlzA and PlzB might have enhanced biological fitness or increased virulence.</p>