Applications of Raman Spectroscopy to Virology and Microbial Analysis - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 450

SERS spectroscopy in combination with biochips to detect the antibody signal
of microbes [101]. Premasiri et al. established the first SERS classification of
single bacteria for six different species under defined cultivation conditions
[102].
TERS experiments were performed to study the bacterial cell surface. Biju
et al. combined silver island films on glass coverslips with an AFM to inves-
tigate the effect of electron-acceptor limitation on the outer cell membrane of
Shewanella oneidensis [103].
Neugebauer et al. performed the first TERS spectra on bacteria [104].
Staph. epidermidis cells exhibit TERS signals of cell wall components which
showed a time-dependent behavior [61, 105].
19.4 Eukaryotes
Besides the development of novel approaches for a fast bacterial detection
and identification, many efforts have also been made for the analysis of yeast
cells. For clinical purposes rapid methodologies for the diagnosis of inva-
sive yeast infections, e.g., by Candida species, have yet emerged to advise
antifungal drugs or to adjust empirical therapy when resistant species are
isolated.
Conventional microbiological identification of isolates from patients can
normally be obtained with a total turnaround time of 48-96 h. Ibelings et al.
[106] and Maquelin et al. [46] developed alternatively a Raman spectroscopic
approach for the identification of clinically relevant Candida species from
smears and microcolonies in peritonitis patients taking at least overnight
(smears) or about 6 h (microcolonies). Hereby, a prediction accuracy of 90%
was obtained for Raman spectroscopy in combination with multivariate sta-
tistical data analysis.
Raman spectroscopy appears to offer an accurate and non-invasive moni-
toring technique of the microbial fermentation progress when combined with
the appropriate chemometric method. The online monitoring of carotenoid
synthesis [107] as well as the online detection of alcoholic fermentation in
living yeast cells for ethanol production from glucose was investigated by
in situ Raman measurements. Furthermore, the influence of the activity of
several enzymes of the glycolytic pathway in dependency of different hydro-
static pressures can be monitored [108]. Since cell wall structure and the
metabolic state of the cell depend on substrate composition, the growth in
different media influences the uptake of special substances. Dostalek et al.
investigated the influence of specific growth conditions on the biosorption ca-
pacity and selectivity for several heavy metals for Saccharomyces cerevisiae
[109].
For single yeast cell investigations it is not sucient to characterize a
yeast cell by means of a single Raman spectrum equivalently to the bacte-
rial analysis described above. Yeast cells as eukaryotes exhibit in contrast to