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Kochan K, Lai E, Richardson Z, Nethercott C, Peleg AY, Heraud P, Wood BR. Vibrational Spectroscopy as a Sensitive Probe for the Chemistry of Intra-Phase Bacterial Growth. SENSORS 2020; 20:s20123452. [PMID: 32570941 PMCID: PMC7348983 DOI: 10.3390/s20123452] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 06/05/2020] [Accepted: 06/15/2020] [Indexed: 01/22/2023]
Abstract
Bacterial growth in batch cultures occurs in four phases (lag, exponential/log, stationary and death phase) that differ distinctly in number of different bacteria, biochemistry and physiology. Knowledge regarding the growth phase and its kinetics is essential for bacterial research, especially in taxonomic identification and monitoring drug interactions. However, the conventional methods by which to assess microbial growth are based only on cell counting or optical density, without any insight into the biochemistry of cells or processes. Both Raman and Fourier transform infrared (FTIR) spectroscopy have shown potential to determine the chemical changes occurring between different bacterial growth phases. Here, we extend the application of spectroscopy and for the first time combine both Raman and FTIR microscopy in a multimodal approach to detect changes in the chemical compositions of bacteria within the same phase (intra-phase). We found a number of spectral markers associated with nucleic acids (IR: 964, 1082, 1215 cm−1; RS: 785, 1483 cm−1), carbohydrates (IR: 1035 cm−1; RS: 1047 cm−1) and proteins (1394 cm−1, amide II) reflecting not only inter-, but also intra-phase changes in bacterial chemistry. Principal component analysis performed simultaneously on FTIR and Raman spectra enabled a clear-cut, time-dependent discrimination between intra-lag phase bacteria probed every 30 min. This demonstrates the unique capability of multimodal vibrational spectroscopy to probe the chemistry of bacterial growth even at the intra-phase level, which is particularly important for the lag phase, where low bacterial numbers limit conventional analytical approaches.
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Affiliation(s)
- Kamila Kochan
- Centre for Biospectroscopy and School of Chemistry, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (E.L.); (Z.R.); (P.H.)
- Correspondence: (K.K.); (B.R.W.)
| | - Elizabeth Lai
- Centre for Biospectroscopy and School of Chemistry, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (E.L.); (Z.R.); (P.H.)
| | - Zack Richardson
- Centre for Biospectroscopy and School of Chemistry, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (E.L.); (Z.R.); (P.H.)
| | - Cara Nethercott
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (C.N.); (A.Y.P.)
| | - Anton Y. Peleg
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (C.N.); (A.Y.P.)
- Department of Infectious Diseases, The Alfred Hospital and Central Clinical School, Monash University, Melbourne, VIC 3004, Australia
| | - Philip Heraud
- Centre for Biospectroscopy and School of Chemistry, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (E.L.); (Z.R.); (P.H.)
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (C.N.); (A.Y.P.)
| | - Bayden R. Wood
- Centre for Biospectroscopy and School of Chemistry, Clayton Campus, Monash University, Clayton, VIC 3800, Australia; (E.L.); (Z.R.); (P.H.)
- Correspondence: (K.K.); (B.R.W.)
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Relationships in Gas Chromatography—Fourier Transform Infrared Spectroscopy—Comprehensive and Multilinear Analysis. SEPARATIONS 2020. [DOI: 10.3390/separations7020027] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Molecular spectroscopic detection techniques, such as Fourier transform infrared spectroscopy (FTIR), provides additional specificity for isomers where often mass spectrometry (MS) fails, due to similar fragmentation patterns. A hyphenated system of gas chromatography (GC) with FTIR via a light-pipe interface is reported in this study to explore a number of GC–FTIR analytical capabilities. Various compound classes were analyzed—aromatics, essential oils and oximes. Variation in chromatographic peak parameters due to the light-pipe was observed via sequentially-located flame ionization detection data. Unique FTIR spectra were observed for separated mixtures of essential oil isomers having similar mass spectra. Presentation of GC×FTIR allows a ‘comprehensive’-style experiment to be developed. This was used to obtain spectroscopic/separation profiles for interconverting oxime species with their individual spectra in the overlap region being displayed on a color contour plot. Partial least square regression provides multivariate quantitative analysis of co-eluting cresol isomers derived from GC–FTIR data. The model resulted in an R2 of 0.99. Prediction was obtained with R2 prediction value of 0.88 and RMSEP of 0.57, confirming the method’s suitability. This study explores the potential of GC–FTIR hyphenation and re-iterates its value to derive unambiguous and detailed molecular information which is complementary to MS.
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Tiernan H, Byrne B, Kazarian SG. Insight into Heterogeneous Distribution of Protein Aggregates at the Surface Layer Using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopic Imaging. Anal Chem 2020; 92:4760-4764. [PMID: 32129602 DOI: 10.1021/acs.analchem.0c00250] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Monoclonal antibodies (mAbs) have been used as therapeutics for the last few decades. It is necessary to investigate the stability of these mAbs under stress conditions and to elucidate aggregation mechanisms as a means of developing approaches which minimize the problem. Attenuated total reflection (ATR)-FTIR spectroscopic imaging allows probing of a sample at a depth of penetration of around 0.5-5 μm, which makes it suitable for the study of aggregated proteins when accumulated as a layer close to the surface of the ZnSe internal reflection element (IRE). Here, macro ATR-FTIR spectroscopic imaging, along with a variable angle of incidence accessory, have been used to differentiate between the secondary structure of proteins in bulk solution and those that have precipitated onto or near the ZnSe IRE surface. IgG spectra obtained from protein samples in individual wells have been averaged, extracted, and preprocessed, and the Amide I bands of the protein samples were compared and further analyzed to reveal protein distribution at the ZnSe IRE surface. These findings show depth profiling of IgG aggregates at the ZnSe IRE surface (0.5-5 μm) and do not follow a trend of decreasing protein presence with an increasing angle of incidence or increasing depth of penetration, suggesting an irregular distribution of aggregates in the z-direction.
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Affiliation(s)
- Hannah Tiernan
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.,Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Bernadette Byrne
- Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Sergei G Kazarian
- Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
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