Staring at the cold sun: blue light regulation is distributed within the genus Acinetobacter

PLoS One. 2013;8(1):e55059. doi: 10.1371/journal.pone.0055059. Epub 2013 Jan 24.

Abstract

We previously showed that the opportunistic nosocomial pathogen Acinetobacter baumannii is able to sense and respond to light via BlsA, a BLUF (Blue-Light-sensing Using FAD)-domain photoreceptor protein. Here, we extend our previous studies showing that light regulation is not restricted to A. baumannii, but rather widespread within the genus Acinetobacter. First, we found that blue light modulates motility and biofilm formation in many species of the genus, including members of the Acinetobacter calcoaceticus-A. baumannii complex. In many of these species blue light acts as a key factor guiding the decision between motility or sessility at 24°C, whereas in A. baumannii, light inhibits both motility and biofilm formation. We also show that light regulation of motility occurred not only at 24°C but also at 37°C in non-A. baumannii species, contrasting the situation of A. baumannii which only shows photoregulation at 24°C. Second, we show that Acinetobacter baylyi (strain ADP1) BLUF-photoreceptors can functionally replace in vivo the A. baumannii 17978 BlsA protein and that the pathways leading to biofilm formation are inversely regulated at 24°C between these two microorganisms. Finally, we found the presence of predicted genes coding BLUF-containing proteins in all Acinetobacter sequenced genomes, even though the copy number is variable among them. Phylogenetic analysis suggests a common origin for all BLUF domains present in members of this genus, and could distinguish well-differentiated clusters that group together BLUF homologs from different species, a situation particularly clear for members of the ACB complex. Despite a role played by these BLUF domain-containing proteins in the photoregulation observed in the members of the genus Acinetobacter is a likely scenario given our findings in A. baumannii and A. baylyi, further research will contribute to confirm this possibility.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter baumannii / classification
  • Acinetobacter baumannii / drug effects
  • Acinetobacter baumannii / physiology*
  • Base Sequence
  • Biofilms
  • DNA Primers
  • Light*
  • Microbial Sensitivity Tests
  • Phylogeny
  • Temperature

Substances

  • DNA Primers

Grants and funding

CONICET PIP 326 2011–2013 (www.conicet.gov.ar), PIP 114–200801–00469 (www.conicet.gov.ar), ANPCyT PICT 25972 (www.agencia.gov.ar), Secretaría de Estado de Ciencia, Tecnología e Innovación de la Provincia de Santa Fe, Grant 2012 (www.santafe.gov.ar/index.php/web/content/view/full/93773). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.