CEFOBI   05405
CENTRO DE ESTUDIOS FOTOSINTETICOS Y BIOQUIMICOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Percepción y respuesta a luz azul en Acinetobacter
Autor/es:
MUSSI M. A.
Lugar:
Córdoba
Reunión:
Congreso; II GRAFOB. (Grupo Argentino de Fotobiología); 2013
Institución organizadora:
(Grupo Argentino de Fotobiología)
Resumen:
We previously demonstrated that the Gram-negative opportunistic human pathogen Acinetobacter baumannii senses and responds to blue light (Mussi et al., 2010). At 24°C, cells form spreading colonies in the dark, but remained at the inoculation point when incubated under blue light. Blue light also inhibited the formation of biofilms and pellicles in broth grown cultures. These bacterial responses depend on the expression of the blue-light-sensing A (blsA) gene, which codes for a protein that contains an N-terminal blue-light-sensing-using flavin (BLUF) domain and lacks a detectable effector domain. Interestingly, temperature plays a role in the ability of A. baumannii to sense and respond to light, as the photoregulation is not observed at 37ºC. One of the most intriguing questions arising from our previous study is related to whether other non-baumannii members of the Acinetobacter genus also show the ability to sense blue light. To address this question, we screened databases for the presence of BLUF-domain containing proteins in the available sequenced genomes of members of this genus. Using the retrieved sequences (and also including sequences from other bacteria and lower eukarya), we inferred their phylogenetic relationships from amino acidic alignments constructed using only the BLUF domain. These analyses showed that all of the Acinetobacter putative photoreceptors were grouped together in a monophyletic cluster, indicating that they share a common origin and no horizontal gene transfer events have occurred with members of other bacteria or eukarya. Besides, we show that light regulation is not restricted to A. baumannii but, rather, is widespread within the Acinetobacter genus. In particular, other members of the A. baumannii-calcoaceticus complex (a subgroup that contains the clinical most relevant species) share with A. baumannii the ability to sense light at 24°C reflected both by motility and biofilm formation assays. Moreover, the four A. baylyi photoreceptors were able to complement the A. baumannii blsA mutant, therefore showing the redundancy in function existent between photoreceptors of different species such as baumannii and baylyi (Golic et al., 2013). Finally, we studied the levels of BlsA in different cells and cellular situations and found that its levels are very low, compatible with its functioning as a regulator. The levels of this photoreceptor vary under light and temperature conditions along the cell cycle, showing that it may function as an activator or anti-repressor at environmental temperatures.