Nanochemistry and biotechnology

Pseudomonas aeruginosa and its reaction to sublethal concentrations of carbon nanomaterials
Augustyniak A. 1,2, Jabłońska J.1, Dubrowska K.1, Krzysztof Cendrowski3, Rakoczy R.1
1 Department of Chemical and Process Engineering, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Szczecin, al. Piastów 42, 71-065 Szczecin, Poland. 
E-mail: adrian.augustyniak@zut.edu.pl
2 Chair of Building Materials and Construction Chemistry, Technische Universität Berlin, Gustav-Meyer-Allee 25, 13355 Berlin, Germany.
3 Department of Nanomaterials Physicochemistry, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Szczecin, Al. Piastów 45, Szczecin 70-311, Poland.
Nanomaterials are often studied for their antibacterial activity. However, still, there are gaps in knowledge on the response of bacteria to the sublethal doses of nanostructures. It has been hypothesized that these concentrations may even stimulate bacteria to grow instead of inhibiting them. Pseudomonas aeruginosa is one of the microorganisms which express high resistance to harsh environmental conditions. It is also a potent producer of utile metabolites such as rhamnolipids, biopolymers, and pigments. These features make this bacterium an excellent model to study reactions to various nanomaterials. Therefore, the aim of the study was to investigate the physiological response of P. aeruginosa to sublethal doses of carbon nanotubes and graphene oxide. 
P. aeruginosa ATCC®27853™ served as the bacterial model for this study, whereas selected nanomaterials included multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO). Several physiological measures were taken into account, including viability, respiration, population growth rate, and pigment production. The results were recorded with the use of culture methods, phase-contrast microscopy, spectrophotometry, and flow cytometry. 
The physiological reaction of the bacterial model depended on the nanomaterial and its concentration. The sublethal doses of nanomaterials could produce a stimulative environment and enhance the growth rate of studied bacteria. Similarly, viability, pigment production, and biofilm formation were also affected by the presence of nanostructures. 
Acknowledgments: This study was funded by the National Science Centre, Poland (PRELUDIUM Project No. 2018/31/N/NZ1/03064.