Characterization of blue-photoreceptors present in Acinetobacter nosocomialis

PEREZ MORA, BÁRBARA; ABATEDAGA, INES; TUTTOBENE, MARISEL ROMINA; MÜLLER, GABRIELA LETICIA; BIANCOTTI, DAIANA; VALLE, LORENA; MUSSI, MARÍA ALEJANDRA

Rosario

Congreso; SAIB-SAMIGE 2021; 2021

Acinetobacter nosocomialis is a Gram-negative coccobacillus, member of the Acinetobacter calcoaceticus-Acinetobacter baumannii (ACB) complex. While A. baumannii predominates over all other members of the ACB complex in terms of incidence, poorer clinical outcomes, and antibiotic resistance rates, A. nosocomialis has gained recognition also as a clinically relevant human pathogen. Interestingly, we have shown that blue light modulates important physiological traits related to pathogenicity determinants, persistence and virulence in A. baumannii and A. nosocomialis. Extensive work performed on A. baumannii showed that this microorganism encodes only one Blue Light sensing Using FAD (BLUF)-type photoreceptor, designated BlsA, which functions at low-environmental temperatures up to 24°C and is regulated both at the transcriptional level as well as the activity of the photocycle. In addition, we have shown that A. nosocomialis is able to sense and respond to light modulating biofilm formation and motility at 24°C. Also, we have shown that light modulates persistence, metabolism, the ability to grow under iron limiting conditions and virulence in this microorganism. The genome of A. nosocomialis RUH2624 encodes three BLUF - domain containing proteins, as the only "traditional" light sensors. In this work, we present evidence indicating that regulation of motility by light in A. nosocomialis is maintained in a wide range of temperatures from 24 to 37°C. Recombinant expression, purification and characterization of the different BLUF-domain-containing proteins showed that the three of them encode active photoreceptors; however only AnBLUF46 and AnBLUF65 are stable. Interestingly, anbluf65 is the only gene expressed in vivo exhibiting a stable photocycle in the temperature range at which light regulates motility in A. nosocomialis. Moreover, intra-protein interactions were analyzed using 3D models built based on A. baumanni´s photoreceptor, to support spectroscopic data and profile intra-protein residue interactions. Finally, quantitative proteomic analyses revealed that light could play a main role in the control of A. nosocomialis physiology at 37°C, particularly modulating pathogenesis and allowing cells to respond and adapt to environmental signals.