Raman spectroscopic differentiation of planktonic bacteria and biofilms
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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.
KeywordsRaman spectroscopy Biofilm Legionella species Tap water
The authors gratefully acknowledge the assistance of Dr. Oliwia Makarewicz in laser scanning microscopy analysis and Prof. Dr. Eberhard Straube and Svea Sachse for providing us with the bacterial strains and for useful discussions. Funding of the research project RiMaTH (02WRS1276E) from the Federal Ministry of Education and Research, Germany (BMBF), is gratefully acknowledged. Financial support of the European Union via the EU project “HemoSpec” (CN 611682) and of the BMBF via the Integrated Research and Treatment Center “Center for Sepsis Control and Care” (FKZ 01EO1002) is highly acknowledged. This project was realized within the InfectoGnostics Research Campus Jena.
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