INTERCOLONIAL VARIABILITY IN MACROMOLECULAR COMPOSITION IN P‐STARVED AND P‐REPLETE SCENEDESMUS POPULATIONS REVEALED BY INFRARED MICROSPECTROSCOPY¹

Abstract

Macromolecular variability in microalgal populations subject to different nutrient environments was investigated, using the chlorophyte alga Scenedesmus quadricauda (Turpin) Bréb. as a model organism. The large size of the four-cell coenobia in the strain used in this study (∼35 μm diameter) conveniently allowed high quality spectra to be obtained from individual coenobia using a laboratory-based Fourier transform infrared (FTIR) microscope with a conventional globar source of IR. By drawing sizable subpopulations of coenobia from two Scenedesmus cultures grown under either nutrient-replete or P-starved conditions, the population variability in macromolecular composition, and the effects of nutrient change upon this, could be estimated. On average, P-starved coenobia had higher carbohydrate and lower protein absorbance compared with P-replete coenobia. These parameters varied between coenobia with histograms of the ratio of absorbance of the largest protein and carbohydrate bands being Gaussian distributed. Distributions for the P-replete and P-starved subpopulations were nonoverlapping, with the difference in mean ratios for the two populations being statistically significant. Greater variance was observed in the P-starved subpopulation. In addition, multivariate models were developed using the spectral data, which could accurately predict the nutrient status of an independent individual coenobium, based on its FTIR spectrum. Partial least squares discriminant analysis (PLS-DA) was a better prediction method compared with soft independent modeling by class analogy (SIMCA).

Evaluation of autotrophic and mixotrophic regimen Chlorella pyrenoidosa cells in various wastes water for its biochemical composition and biomass production

“…Many researchers have identified FTIR as a tool to investigate the changes in cellular components, including carbohydrates, lipids and proteins as well as a response to a nutrient stress, such as low-N (Giordano et al, 2001;Heraud et al, 2008;Stehfest et al, 2005) and low-P (Dean et al, 2012;Dean et al, 2010;Sigee et al, 2007). FTIR spectra of C. pyrenoidosa cells showed distinct absorption bands over the wavenumber range 4000-800cm -1 (Fig.…”

Snapshot prediction of carbon productivity, carbon and protein content in a Southern Ocean diatom using FTIR spectroscopy

“…Spectroscopic approaches offer substantial benefits over traditional methods, being inexpensive, quantitative, objective, rapid, high throughput, sensitive and inherently multivariate (Hirschmugl et al, 2005;Heraud et al, 2005Heraud et al, , 2007aHeraud et al, , 2008Jebsen et al, 2012;Sackett et al, 2013). The use of spectroscopic techniques such as Raman and Fourier transform infrared (FTIR) spectroscopy in phytoplankton studies has been widely explored (Heraud et al, 2007b;Heraud et al, 2008;Domenighini and Giordano, 2009;Dean et al, 2012Dean et al, , 2010.…”

“…The use of spectroscopic techniques such as Raman and Fourier transform infrared (FTIR) spectroscopy in phytoplankton studies has been widely explored (Heraud et al, 2007b;Heraud et al, 2008;Domenighini and Giordano, 2009;Dean et al, 2012Dean et al, , 2010. These techniques involve irradiating a sample with specific wavelengths of light and measuring light scattering (Raman spectroscopy) or absorbance (FTIR spectroscopy) by the sample.…”

Taxon-specific responses of Southern Ocean diatoms to Fe enrichment revealed by synchrotron radiation FTIR microspectroscopy

“…Differences in variability were not observed when data were pooled across the four taxa, suggesting that community averages may not necessarily reflect the macromolecular composition of F. kerguelensis, despite its relatively high abundance within the assemblage. Although studies of intraspecific variability in microalgae are rare, higher levels of population variability have been previously reported for laboratory cultured microalgae under nutrient stress using SR-FTIR microspectroscopy (Heraud et al, 2008). Also, in a previous study of the Southern Ocean diatoms Fragilariopsis cylindrus, Chaetoceros simplex and Pseudo-nitzschia subcurvata, higher intraspecific variability was shown, particularly for F. cylindrus, under extreme salinity and temperature conditions (Sackett et al, 2013).…”

“…Data were initially screened for quality using Principal Component Analysis (PCA) to remove obvious outliers, prior to the calculation of average spectra and analysis by Partial Least Squares Discriminant Analysis (PLSDA) (Heraud et al, 2008;Sackett et al, 2013;Wold et al, 2001). Outliers were identified using the Leverage versus Residual Xvariance plots, with a threshold of 5 % set nominally.…”