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ABSTRACT: Classification of Raman spectra recorded from single cells is commonly applied to bacteria that exhibit small sizes of approximately 1 to 2 μm. Here, we study the possibility to adopt this classification approach to filamentous bacteria of the genus Streptomyces. The hyphae can reach extensive lengths of up to 35 μm, which can correspond to a single cell identified in light microscopy. The classification of Raman bulk spectra will be demonstrated. Here, ultraviolet resonance Raman (UV RR) spectroscopy is chosen to classify six Streptomyces species by the application of a tree-like classifier. For each knot of the hierarchical classifier, estimated classification accuracies of over 94% are accomplished. In contrast to the classification of bulk spectra, the classification of single-cell spectra requires a homogenous substance distribution within the cell. Consequently, the bacterial cell chemistry can be represented by one individual spectrum. This requirement is not fulfilled when different spectra are processed from different locations within the cell. Bacteria of the investigated genus Streptomyces exhibit, besides the normal bacterial spectra, lipid-rich spectra. The occurrence of lipid enrichment depends on culture age and nutrition availability. With this study, we investigate the cell substance distribution, especially of lipid-rich fractions. The classification utilizing a tree-like classifier is also applied to the Streptomyces single-cell spectra, resulting in classification accuracies between 80 and 93% for the investigated Streptomyces species.
Applied Spectroscopy 10/2011; 65(10):1116-25. · 1.66 Impact Factor
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ABSTRACT: Bacterial resistances against antibiotics are increasingly problematic for medical treatment of pathogenic bacteria, e.g., in hospitals. Resistances are, among other genes, often encoded on plasmids which can be transmitted between bacteria not only within one species, but also between different species, genera, and families. The plasmid pDrive is transformed into bacteria of the model strain Escherichia coli DH5α. Within this investigation, we applied micro-Raman spectroscopy with two different excitation wavelengths in combination with support vector machine (SVM) and linear discriminant analysis (LDA) to differentiate between bacterial cultures according to their cultural plasmid content. Recognition rates of about 92% and 90% are achieved by Raman excitation at 532 and 244 nm, respectively. The SVM loadings reveal that the pDrive transformed bacterial cultures exhibit a higher DNA content compared to the untransformed cultures. To elucidate the influence of the antibiotic, ampicillin-treated cultures are also comprised within this study and are classified with rates of about 97% and 100% for 532 and 244 nm Raman excitation, respectively. The Raman spectra recorded with 532 nm excitation wavelength show differences of the secondary protein structure and enhanced stress-related respiration rates for the ampicillin-treated cultures. Independent cultural replicates of either ampicillin-challenged or non-challenged cultures are successfully identified with identification rates of over 90%.
Analytical and Bioanalytical Chemistry 03/2011; 400(9):2763-73. · 3.78 Impact Factor
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ABSTRACT: The use of microorganisms for the extraction of contaminants like solved metals from drainage or surface waters was investigated using strains adapted to a polluted environment at a former uranium mining site near Kauern, Eastern Thuringia, Germany. Soil respiration data showed increasing variation indicating stress response and hence need for adaptation. Thus, isolation of single strains was performed for more detailed analyses. Of the isolated fungi and bacteria (single-celled bacteria as well as filamentous actinobacteria), 15 were grown in mine drainage waters in order to test their capacity to retain (heavy) metals including rare earth elements and radioisotopes. Out of the 15 strains (respectively 5 single-celled bacteria, actinobacteria and fungi), 11 strains could grow in media containing acid mine drainage waters diluted by half which is representative of the conditions a few meters downstream of the entry point of the acid mine drainage. Two strains showed promising capacity for aluminum or uranium retention. Using rare earth elements as tracers, selective biosorption or uptake of heavy rare earth elements was prominent in one sample, a fungal isolate. The actinobacterial strains also showed capacity for bioremediation of contaminated seepage waters. Different reactions to single elements varying between all isolates indicate biologically controlled transport processes because such strong fractionation would not be expected from physico-chemical adsorption processes.
Journal of Geochemical Exploration.
