Application of Mid-infrared and Raman Spectroscopy to the Study of Bacteria

Abstract

Infrared spectroscopy and Raman spectroscopy provide complementary technologies for rapid and precise detection of microorganisms and are emerging methods in food analysis. It is possible to use either of these techniques to differentiate and quantify microorganisms in relatively simple matrices such as liquid media and simple solutions with determinations taking less than an hour. Vibrational spectroscopy, unlike other techniques used in microbiology, is a relatively simple method for studying structural changes occurring within a microbial cell following environmental stress and applications of food processing treatments. Vibrational spectroscopy provides a wide range of biochemical properties about bacteria in a single spectrum, most importantly characteristics of the cell membrane. These techniques are especially useful for studying properties of bacterial biofilms on contact surfaces, the presence and viability of bacterial vegetative cells and spores, the type and degree of bacterial injury, and assessment of antibiotic susceptibility. Future trends in food analysis will involve combining vibrational spectroscopy with microscopy, mass spectroscopy, or DNA-based methods to comprehensively study bacterial stress. Further advances in selectivity, sensitivity, and improved chemometric methods, along with reduction in the cost of instrumentation, may lead to the development of fieldready and real-time analytical systems.

Comprehensive Detection and Discrimination of Campylobacter Species by Use of Confocal Micro-Raman Spectroscopy and Multilocus Sequence Typing

“…Both infrared and Raman spectroscopy methods are forms of vibrational spectroscopy, and their spectral patterns for biological samples have shown good reproducibility and high discriminatory power (41)(42)(43)(44). In addition, these bioanalytical techniques are fast, reagentless, and easy to conduct.…”

“…In addition, these bioanalytical techniques are fast, reagentless, and easy to conduct. Thus, they provide the unique advantage of differentiating taxonomic entities at the species or subspecies level on the basis of variations in the spectral features of bacterial cells (41). Since the two groundbreaking publications in Nature about the use of infrared spectroscopy (57) and Raman spectroscopy (61) to study microorganisms, these two techniques have been extensively employed to detect and discriminate different microorganisms and have been shown to be useful as real-time typing methods in bacterial epidemiology (3,7,33,34,36,37,48,49,59,60,65,77).…”

“…Due to minor variations within the raw vibrational spectral features of different microbiological samples, the interpretation of spectra requires advanced chemometric tools (2,41). The use of pattern recognition can unmask relationships and cluster constituents on the basis of their perceived closeness.…”

Determining Ovarian Maturity in Farmed Sturgeon 1 (Acipenser transmontanus) for Caviar Production Using Fourier Transform Infrared Spectroscopy (FT-IR)

“…The first three PCs can explain over 80% of segregation capability of either the cluster or dendrogram models (Figures 2 and 3) with the most significant features being associated with changes to protein secondary structure: amide I (1695 cm -1 ) [7,20,21]; α-helical structures (1655 cm ) [19]; CO stretching of the C-OH groups of serine, threonine and tyrosine in the cell proteins (1172/1173 cm -1 ) [19]. For carbohydrate, the band at 1430 cm -1 is assigned to δ (CH2) of polysaccharide [7,20,21], while the band at 1205 cm -1 is dominated by the ring vibrations of polysaccharides C-O-P, PO-P [22]. The band at 1469 cm -1 is derived from CH2 banding of the acyl chains from phospholipids [7,20,21].…”

“…For carbohydrate, the band at 1430 cm -1 is assigned to δ (CH2) of polysaccharide [7,20,21], while the band at 1205 cm -1 is dominated by the ring vibrations of polysaccharides C-O-P, PO-P [22]. The band at 1469 cm -1 is derived from CH2 banding of the acyl chains from phospholipids [7,20,21]. The band at 1620 cm -1 is assigned to stretching base carbonyl and ring breathing mode of 11 nucleic acids [19], and 1592 cm -1 is assigned to C=N and NH2 in adenine [22].…”