In nymphs taking a blood meal, the expression of RpoS is highly induced, and then this global regulator, rather than the housekeeping σ70, likely transcribes dbpA. Additional studies are warranted to further elucidate the fine tuning of dbpBA expression, including the putative roles of the

IRs in dbpBA gene expression in ticks. Figure 4 qRT-PCR analysis of dbpA transcription in ticks and in mouse tissues. A, flat (uninfected) larvae, fed larvae, intermolt larvae, and fed nymphs during transmission phase were collected at 24-, 48-, and 72-h post-feeding. TT: tick transmission. B, mouse tissues of skin (S) heart (H), and bladder (B) were collected at various numbers of days (inset) after infection. Angiogenesis inhibitor The values represent the average copy

number normalized per 100 copies of B. burgdorferi flaB transcripts. Our data also revealed that dbpA transcripts were readily detected in mouse tissues at all times post-infection, including 7-, 14-, 21-, 28-, and 50-d (Figure 4B), suggesting that dbpA expression remains active during the entire mammalian phase of B. burgdorferi infection. These results are fully consistent with other reports using protein detection methods for Dbp assessment [63]. The finding that expression of both rpoS and dbpA, but not ospC, in the later BIX 1294 cell line phases of mammalian infection also is in agreement with a previous hypothesis [49] that repression of ospC may be mediated by a potential trans-acting repressor. Conclusions Since its initial discovery by Hubner et al. [19], the RpoN-RpoS pathway has been the subject of numerous studies seeking to understand core elements Resveratrol of regulatory control in B. burgdorferi [16–18, 20–33, 37, 43, 47, 49, 52, 56, 66]. What has emanated from this expanding body of work is that although certain

aspects of the pathway’s activation have been predictable, many emerging details have been counter intuitive. One of the unanticipated findings includes the discovery that BosR serves as an additional molecule essential for activation of the RpoN-RpoS pathway [28–31]. In this current study, we again obtained both anticipated and unanticipated experimental results surrounding the activation of the RpoN-RpoS pathway in ticks and during B. burgdorferi dissemination in mammalian tissues. Our data indicate that the transcription levels of ospC, dbpA, ospA, or rpoS were variable among mouse samples at different times post-infection. One potential explanation for this is that these important genes are indeed transcribed at different levels within these tissues. Alternatively, it is also possible that our results emanated from low spirochete burdens in these tissue samples, as indicated by the relatively low levels of flaB transcripts detected in these same samples (data not shown). Indeed, the low numbers of spirochetes in certain mouse tissue samples limited our cDNA yields.