Absorption microspectroscopy, theory and applications in the case of the photosynthetic compartment

Evangelista

et al. 2016

Journal of Microscopy

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A novel procedure for deriving the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its image is presented. Any digital image acquired by a microscope can be used; typical applications are the analysis of cellular/subcellular metabolic processes under physiological conditions and in response to environmental stressors (e.g. heavy metals), and the measurement of chromophore composition, distribution and concentration in cells. In this paper, we challenged the procedure with images of algae, acquired by means of a CCD camera mounted onto a microscope. The many colours algae display result from the combinations of chromophores whose spectroscopic information is limited to organic solvents extracts that suffers from displacements, amplifications, and contraction/dilatation respect to spectra recorded inside the cell. Hence, preliminary processing is necessary, which consists of in vivo measurement of the absorption spectra of photosynthetic compartments of algal cells and determination of spectra of the single chromophores inside the cell. The final step of the procedure consists in the reconstruction of the absorption spectrum of the cell spot from the colour values of the corresponding pixel(s) in its digital image by minimization of a system of transcendental equations based on the absorption spectra of the chromophores under physiological conditions.

Section: Resultsmentioning

confidence: 99%

“…3200 K) (Levi, 1968), an oil immersion condenser (N.A. For a complete analysis and descriptions of the microspectrophotometry theory see Barsanti et al (2007). 0.75) and 20× (N.A.…”

Section: Microspectroscopymentioning

confidence: 99%

Reconstruction of the absorption spectrum of an object spot from the colour values of the corresponding pixel(s) in its digital image: the challenge of algal colours

Coltelli

Evangelista

et al. 2016

Journal of Microscopy

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“…The relative contribution of the individual pigment classes to the absorption spectra was estimated by applying a decomposition procedure as described by Barsanti et al. ().…”

Section: Methodsmentioning

confidence: 99%

Tetraflagellochloris mauritanica gen. et sp. nov. (Chlorophyceae), a New Flagellated Alga from the Mauritanian Desert: Morphology, Ultrastructure, and Phylogenetic Framing

Frassanito

Passarelli

et al. 2012

Journal of Phycology

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Morphological, ultrastructural, and molecular-sequence data were used to assess the phylogenetic position of a tetraflagellate green alga isolated from soil samples of a saline dry basin near F'derick, Mauritania. This alga can grow as individual cells or form non-coenobial colonies of up to 12 individuals. It has a parietal chloroplast with an embedded pyrenoid covered by a starch sheath and traversed by single parallel thylakoids, and an eyespot located in a parietal position opposite to the flagellar insertion. Lipid vacuoles are present in the cytoplasm. Microspectroscopy indicated the presence of chlorophylls a and b, with lutein as the major carotenoid in the chloroplast, while the eyespot spectrum has a shape typical of green-algal eyespots. The cell has four flagella, two of them long and two considerably shorter. Sequence data from the 18S rRNA gene and ITS2 were obtained and compared with published sequences for green algae. Results from morphological and ultrastructural examinations and sequence analysis support the placement of this alga in the Chlorophyceae, as Tetraflagellochloris mauritanica L. Barsanti et A. Barsanti, gen. et sp. nov.

“…These red algae are able to survive in the dark blue sea because they possess accessory pigments, including carotenoids, xantophylls and phycobiliproteins, that absorb light in spectral regions different from those of the green chlorophylls a and b. This absorbed light energy is channeled to chlorophyll a, which is the only molecule able to convert sunlight energy into chemical energy (Barsanti et al, 2007). Due to the presence of these pigments, the green of their chlorophylls is masked and these algae look dark purple.…”

Section: Low Depthmentioning

confidence: 99%

Oddities and Curiosities in the Algal World

NATO Science for Peace and Security Series A: Chemistry and Biology

Coltelli

Evangelista

et al. 2008

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assemblage, of O 2 -evolving, photosynthetic organisms. The profound diversity of size, shape, habitat, metabolic traits and growth strategies makes this heterogeneous assemblage of both prokaryotic and eukaryotic species an almost unlimited source of curious and unusual features. Algae display an incredible adaptability to most environments, and provide an excellent system for testing hypotheses concerning the evolution of ecological tolerance. In fact, they are not limited to temperate waters, but can survive at very low depth and very low irradiance, and thrive beneath polar ice sheets. Upon adaptation to life on land, algae have colonized such surprising places, as catacombs, tree trunks, hot springs, and can also resist desiccation in the desert regions of the world. Moreover, relations between them and other organisms, which include competition within and between species for space, light, nutrient or any limiting source, are based on a variety of associations, which includes epiphytism, parasitism, and symbiosis. Algae can share their life with animals, growing on sloth hair, inside the jelly capsule of amphibian eggs, upon the carapaces of turtles or shells of mollusks, camouflaging the dorsal scute of harvestmen. They can also light up the sea at night, and cause infections in animals and humans.______ *To whom correspondence should be addressed. Paolo Gualtieri, Istituto di Biofisica C.N.R., Area della Ricerca di Pisa, Via Moruzzi 1, 56124, Pisa, Italy. Email: paolo.gualtieri@pi.ibf.cnr.it 353 Abstract: The term algae refers to a polyphyletic, non-cohesive and artificial