AUTHOR=Crespo Anna , Blanco-Cabra Núria , Torrents Eduard 

TITLE=Aerobic Vitamin B12 Biosynthesis Is Essential for Pseudomonas aeruginosa Class II Ribonucleotide Reductase Activity During Planktonic and Biofilm Growth

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00986

DOI=10.3389/fmicb.2018.00986

ISSN=1664-302X

ABSTRACT=<p><italic>Pseudomonas aeruginosa</italic> is a major pathogenic bacterium in chronic infections and is a model organism for studying biofilms. <italic>P. aeruginosa</italic> is considered an aerobic bacterium, but in the presence of nitrate, it also grows in anaerobic conditions. Oxygen diffusion through the biofilm generates metabolic and genetic diversity in <italic>P. aeruginosa</italic> growth, such as in ribonucleotide reductase activity. These essential enzymes are necessary for DNA synthesis and repair. Oxygen availability determines the activity of the three-ribonucleotide reductase (RNR) classes. Class II and III RNRs are active in the absence of oxygen; however, class II RNRs, which are important in <italic>P. aeruginosa</italic> biofilm growth, require a vitamin B<sub>12</sub> cofactor for their enzymatic activity. In this work, we elucidated the conditions in which class II RNRs are active due to vitamin B<sub>12</sub> concentration constraints (biosynthesis or environmental availability). We demonstrated that increased vitamin B<sub>12</sub> levels during aerobic, stationary and biofilm growth activate class II RNR activity. We also established that the <italic>cobN</italic> gene is essentially responsible for B<sub>12</sub> biosynthesis under planktonic and biofilm growth. Our results unravel the mechanisms of dNTP synthesis by <italic>P. aeruginosa</italic> during biofilm growth, which appear to depend on the bacterial strain (laboratory-type or clinical isolate).</p>