Fourier transform infrared spectroscopy of dental unit water line biofilm bacteria

Iram Liaqat

doi:10.1155/2009/892569

Abstract

Fourier transform-infrared (FT-IR) spectroscopy has become an important tool for rapid analysis of complex biological samples. The infrared absorbance spectrum could be regarded as a “fingerprint” which is a feature of biochemical substances. The FT-IR spectra of fresh and stored dried samples of six bacterial isolates (Klebsiellasp.,Bacillus cereus, Bacillus subtilis, Pseudomonas aeruginosa, Achromobacter xylosoxidans and Achromobactersp.) were observed by variation in sample preparation. The results indicated that variation in sample preparation did not affect the spectra of isolates. However, less promiment/absence of a small shoulder peak at 1738 cm−1was evident in fresh dried samples ofAchromobactersp. and A.xylosoxidanscompared to prominent and broad shoulder band at 1724 cm−1in stored dried samples of these two isolates. In addition to the established KBr pellet technique, attenuated total reflectance (ATR) spectroscopy was used to analyse the spectra of planktonic growth (−80°C liquid cultures) and biofilm growth of six isolates. ATR spectroscopy of −80°C planktonic and biofilm growth showed variation in absorption spectra in fingerprint (1200−900 cm−1) region. Two clear absorption bands were prominent in biofilm at 1175 and 1143 cm−1whereas, one prominent broad band at 1075 cm−1resulting from the overlapping of two band was noted in planktonic cultures. Biofilm forming capability of the six isolates was also determined by acridine orange staining method. The microscopic analysis of biofilms formed on glass slides revealed the presence of a matrix of exopolysaccharides and microcolonies typical of biofilm architecture. Maximum biofilm formation was observed after 175 h inP. aeruginosaandKlebsiellasp.

Highlights

Microbial biofilm formation in dental unit water lines (DUWL) is common and has become a serious threat to clinical dentistry
The six bacterial strains used in this study were Klebsiella sp. (DQ989215), Bacillus cereus (DQ989214), Bacillus subtilis (DQ989210), Pseudomonas aeruginosa (DQ989211), Achromobacter xylosoxidans (DQ989213) and Achromobacter sp. (DQ989212), which were grown in 100-ml Luria-Bertani (LB) medium (10 g bacto tryptone (Difco, UK), 5 g yeast extract (Difco, UK) and 10 g NaCl) to early stationary phase (18 h)
The six bacterial strains examined for Fourier transform infrared spectroscopy (FT-IR) spectroscopy were isolated from DUWL biofilm [15]

Summary

Introduction

Microbial biofilm formation in dental unit water lines (DUWL) is common and has become a serious threat to clinical dentistry. There exist a number of methods for study of bacterial microorganisms. These methods include amplification of nucleic acids by polymerase chain reaction (PCR) [32], and mass spectrometry. I. Liaqat / Fourier transform infrared spectroscopy of dental unit water line biofilm bacteria [19], etc. FT-IR and Raman spectroscopy have been developed by several research groups to explore many features of whole microorganisms [2] and have been used to identify cellular components of both pathogenic and non-pathogenic bacteria [24]. Compared to FT-IR, this approach is still not sufficiently developed [34]

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Conclusion