Raman spectroscopic differentiation of planktonic bacteria and biofilms

Abstract

Both biofilm formations as well as planktonic cells of water bacteria such as diverse species of the Legionella genus as well as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli were examined in detail by Raman microspectroscopy. Production of various molecules involved in biofilm formation of tested species in nutrient-deficient media such as tap water was observed and was particularly evident in the biofilms formed by six Legionella species. Biofilms of selected species of the Legionella genus differ significantly from the planktonic cells of the same organisms in their lipid amount. Also, all Legionella species have formed biofilms that differ significantly from the biofilms of the other tested genera in the amount of lipids they produced. We believe that the significant increase in the synthesis of this molecular species may be associated with the ability of Legionella species to form biofilms. In addition, a combination of Raman microspectroscopy with chemometric approaches can distinguish between both planktonic form and biofilms of diverse bacteria and could be used to identify samples which were unknown to the identification model. Our results provide valuable data for the development of fast and reliable analytic methods based on Raman microspectroscopy, which can be applied to the analysis of tap water-adapted microorganisms without any cultivation step.

Raman and Surface-Enhanced Raman Scattering for Biofilm Characterization

“…Kusić et al [38] studied planktonic cells and biofilms of six Legionella strains, as well as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli species. Comparison of the Raman spectra of L. pneumophila and Pseudomonas aeruginosa grown in tap water and artificial media revealed an increased lipid and decreased DNA content in bacterial cells as an adaptation to nutrient-limited environmental conditions.…”

The application of Raman spectroscopy for the detection and identification of microorganisms

“…This hierarchical approach was then successfully tested with 985 independent Raman spectra. In addition, also planktonic cells could be distinguished from sessile cells inside biofilms …”

“…In addition, also planktonic cells could be distinguished from sessile cells inside biofilms. [72] Raman imaging was applied on bacteria isolated out of distilled water by means of filtration. In a preliminary approach, droplets of cell suspensions were dried on an aluminum slide.…”

Strain-level typing and identification of bacteria – a novel approach for SERS active plasmonic nanostructures

“…SERS also provides an opportunity to obtain a spectral fingerprint of different bacterial species, including foodborne species, for instance Listeria monocytogenes [7–9]. For this reason, over the last decade interest in SERS applied to bacteria has rapidly increased [10–12]. This interest is associated with the high sensitivity of the SERS technique and increasing number of bacterial strains dangerous for humans.…”