PMID:30478087

Citation	Boyle, WK, Groshong, AM, Drecktrah, D, Boylan, JA, Gherardini, FC, Blevins, JS, Samuels, DS and Bourret, TJ (2019) DksA Controls the Response of the Lyme Disease Spirochete to Starvation. J. Bacteriol. 201
Abstract	The pathogenic spirochete senses and responds to changes in the environment, including changes in nutrient availability, throughout its enzootic cycle in ticks and vertebrate hosts. This study examined the role of DnaK suppressor protein (DksA) in the transcriptional response of to starvation. Wild-type and mutant strains were subjected to starvation by shifting cultures grown in rich complete medium, Barbour-Stoenner-Kelly II (BSK II) medium, to a defined mammalian tissue culture medium, RPMI 1640, for 6 h under microaerobic conditions (5% CO, 3% O). Microarray analyses of wild-type revealed that genes encoding flagellar components, ribosomal proteins, and DNA replication machinery were downregulated in response to starvation. DksA mediated transcriptomic responses to starvation in , as the -deficient strain differentially expressed only 47 genes in response to starvation compared to the 500 genes differentially expressed in wild-type strains. Consistent with a role for DksA in the starvation response of , fewer CFU of mutants were observed after prolonged starvation in RPMI 1640 medium than CFU of wild-type spirochetes. Transcriptomic analyses revealed a partial overlap between the DksA regulon and the regulon of Rel, the guanosine tetraphosphate and guanosine pentaphosphate [(p)ppGpp] synthetase that controls the stringent response; the DksA regulon also included many plasmid-borne genes. Additionally, the mutant exhibited constitutively elevated (p)ppGpp levels compared to those of the wild-type strain, implying a regulatory relationship between DksA and (p)ppGpp. Together, these data indicate that DksA, along with (p)ppGpp, directs the stringent response to effect adaptation to its environment. The Lyme disease bacterium survives diverse environmental challenges as it cycles between its tick vectors and various vertebrate hosts. must withstand prolonged periods of starvation while it resides in unfed ticks. In this study, the regulatory protein DksA is shown to play a pivotal role controlling the transcriptional responses of to starvation. The results suggest that DksA gene regulatory activity impacts metabolism, virulence gene expression, and the ability of this bacterium to complete its natural life cycle.
Links	PubMed PMC6351744 Online version:10.1128/JB.00582-18
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BORBU:O51190		GO:0015972: guanosine pentaphosphate metabolic process	ECO:0007110: thin layer chromatography evidence used in manual assertion		P		The authors generated a mutant strain of Borrelia burgdorferi with the dksA gene knocked out. Using thin-layer chromatography, they measured the levels of (p)ppGpp produced by both wild-type and ΔdksA mutants under starvation conditions (figure 7A). When these results were quantified and normalized to levels of (p)ppGpp+GTP, the authors found that the ΔdksA mutant produced significantly higher levels of (p)ppGpp than wild-type (figure 7B). Reinsertion of the dksA gene through a plasmid vector containing the dksA ORF (pDksA) restored production levels of (p)ppGpp comparable to that of the wild-type strain. This indicates that the dksA gene plays a role in regulation of guanosine pentaphosphate metabolism.	complete CACAO 13662

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