Acinetobacter nosocomialis harbors BLUF photoreceptors functional at moderate temperatures such as 37ºC

BORSARELLI CLAUDIO D.; ABATEDAGA INES; LOTO ALBA; MUSSI MARÍA A; VALLE LORENA ; GOLIC ADRIÁN

Viña del Mar

Encuentro; Encuentro Latinoamericano de Fotoquímica y Fotobiología; 2019

Pontificia Universidad Catolica de Chile

Microorganisms from the genus Acinetobacter harbor from one up to six copies of Blue light using FAD (BLUF) photoreceptors in their genomes. While in A. baumanii photoregulation of motility is lost at temperatures ≥ 24ºC, in A. nosocomialis still shows photoregulation even at 37ºC. The first difference between both species is the presence of three BLUF domain-containing proteins in A. nosocomialis, while only one is present in A. baumannii, which is the well-characterized photoreceptor BlsA. Recently, we have been shown that BlsA from A. baumanni is temperature sensitive showing little or no photoactivity above 26ºC, which correlates well with its expression levels and BlsA protein presence in the cells.In contrast, given that A. nosocomialis harbors three BLUF genes encoded in its genome, with a different photoregulation pattern as a function of temperature, we hypothesized that differential behavior of the encoded photoreceptors could account for the extended photoregulation observed at higher temperatures.To confirm this hypothesis, we have performed a biophysical and photophysical characterization of two of them. For this purpose, the open reading frames encoding for A. nosocomialis BLUF46 and BLUF65 were cloned into pBluescript and then transferred into pET28. The corresponding recombinant proteins were expressed and purified. In both cases, these photoreceptors have shown to have an extended range of temperature at which they are active in comparison to BlsA. BLUF46 has an active photocycle up to 32ºC while BLUF65 reaches 37ºC completely active, and thus could be responsible for the photoregulation of motility observed in A. nosocomialis at 37ºC. Interestingly, BLUF65 shows photophysical distinctive characteristics than is A. baumannii ortholog, BlsA, suggesting that differences contained in the primary structure may account for the differential temperature dependence.