Raman Spectroscopy of Xylitol Uptake and Metabolism in Gram-Positive and Gram-Negative Bacteria

Abstract

Visible-wavelength Raman spectroscopy was used to investigate the uptake and metabolism of the fivecarbon sugar alcohol xylitol by Gram-positive viridans group streptococcus and the two extensively used strains of Gram-negative Escherichia coli, E. coli C and E. coli K-12. E. coli C, but not E. coli K-12, contains a complete xylitol operon, and the viridans group streptococcus contains an incomplete xylitol operon used to metabolize the xylitol. Raman spectra from xylitol-exposed viridans group streptococcus exhibited significant changes that persisted even in progeny grown from the xylitol-exposed mother cells in a xylitol-free medium for 24 h. This behavior was not observed in the E. coli K-12. In both viridans group streptococcus and the E. coli C derivative HF4714, the metabolic intermediates are stably formed to create an anomaly in bacterial normal survival. The uptake of xylitol by Gram-positive and Gram-negative pathogens occurs even in the presence of other high-calorie sugars, and its stable integration within the bacterial cell wall may discontinue bacterial multiplication. This could be a contributing factor for the known efficacy of xylitol when taken as a prophylactic measure to prevent or reduce occurrences of persistent infection. Specifically, these bacteria are causative agents for several important diseases of children such as pneumonia, otitis media, meningitis, and dental caries. If properly explored, such an inexpensive and harmless sugar-alcohol, alone or used in conjunction with fluoride, would pave the way to an alternative preventive therapy for these childhood diseases when the causative pathogens have become resistant to modern medicines such as antibiotics and vaccine immunotherapy.

Use of Polyols in Oral Biology Research

“…The above findings and earlier clinical observations on the caries-limiting role of xylitol receive interesting support from the Raman spectroscopy studies of Palchaudhuri et al (2011), who suggested that uptake of xylitol by Gram-positive and Gram-negative pathogens occurs even in the presence of other high-calorie sugars. Stable integration of xylitol within the bacterial cell wall may discontinue bacterial multiplication.…”

Methods and Applications of Raman Microspectroscopy to Single-Cell Analysis

“…[79][80][81][82][83][84] In early work, Choo-Smith et al 85 86 used Raman spectroscopy to quantify filtered waterborne pathogenic microbial contamination, and Pasteris et al 87 used Raman spectroscopy to identify sulfur inclusions in sulfur-oxidizing marine bacteria. Recently, Palchaudhuri et al 88 investigated the uptake and metabolism of the five-carbon sugar alcohol xylitol by gram-positive viridian group Streptococcus and two gram-negative Escherichia coli strains. In assessing Bacillus strains, Hutsebaut et al 89 characterized the influence of culture conditions on the ability of Raman spectroscopy to discriminate between Bacillus cereus, Bac i l l u s p u m i l u s , a n d B a c i l l u s licheniformis.…”

Flow Cytometry Monitors Xylitol Metabolism of Streptococcus mitis

“…Our Raman spectroscopic studies have recently confirmed the formation of this xylitol intermediate by the metabolism of xylitol in both Gram-positive and Gram-negative bacteria, provided they contained the xylitol operons [15]. Moreover, we have shown that xylitol exposure interferes with the ability of these bacteria to retain the crystal violet, a dye essential in Gram staining technique [15]. A thinning of bacterial cell wall thickness may have occurred during their growth in xylitol, resulting in this reduced retention of crystal violet molecules.…”

“…These pathogens have similar diplococcic morphology and it is known that Streptococcus mitis bacterial species has several similar physiological characteristics common to S. pneumoniae including the ability to partially metabolize xylitol to produce a toxic xylitol intermediate, probably xylitol-5-phosphate [8][9][10][11][12][13][14]. Our Raman spectroscopic studies have recently confirmed the formation of this xylitol intermediate by the metabolism of xylitol in both Gram-positive and Gram-negative bacteria, provided they contained the xylitol operons [15]. Moreover, we have shown that xylitol exposure interferes with the ability of these bacteria to retain the crystal violet, a dye essential in Gram staining technique [15].…”