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A rapid Method for the Quantitative Isolation of Green Algae from lichens

AuthorsAscaso, Carmen CSIC ORCID
KeywordsParmelia conspersa (Ach)
Lasallia pustulata (L)
Green algae
Issue Date1980
CitationAnnals of Botany 45: 483 (1980)
AbstractThis report describes a rapid and quantitative method for the isolation of green algae from lichen thalli. Several qualitative techniques have been described (see Richardson, 1971, for a review), but until now a quantitative method for blue-green algae only has been published (Millbank and Kershaw, 1969). Two grams of washed thalli of Parmelia conspersa (Ach.) or Lasallia pustulata (L.), were minced with scissors and then ground up in a mortar with distilled water. The macérate was further homogenized with six strokes in a teflon-glass Elvehjem-Potter homogenizer and then filtered through three layers of gauze of standard mesh size. The volume of the fíltrate was adjusted to 100 mi with distilled water and centrifuged five times at 100 g for 10 s. The pellets were mixed and re-processed as above. The supernatants were mixed and algal cells were pelleted by centrifugation at 500 g for 10 min. The algae were resuspended in 0-25 M sucrose in a final volume of 2 mi and the algal suspensión was layered over 3 mi of a CsCl solution of a density of l-550gcm~3 (refractive Índex at 25 °C r¡z& = 1-3856). After centrifugation at 4500 rev min'1 in the swinging-bucket rotor of a clinical centrifuge for 10 min, algal cells banded at the interphase and were recovered, washed and resuspended in 0-25 M sucrose. Algal symbionts of two lichen species (P. conspersa and L. pustulata) were quantitatively isolated and puriñed by the method described above. No appreciable contamination by fungal hyphae was observed on microscopic examination and the recovery of puré algae was about 50 mg of wet weight per gram of thallus. Caesium chloride can be replaced by potassium iodide which is cheaper and so is preferable, particularly for larger-scale isolations than the one described here. An 80 per cent (w/v) solution of KI has approximately the same density as the CsCl solution used above. The yield of algae was sufficient to allow chemical analysis of phycobiont freshly isolated from lichens. Furthermore, only a small fraction (about 10 per cent) of the algal cells were altered in their appearance under the microscope. The two lichen species studied in this paper have Trebouxia as phycobiont (Ascaso and Galvan, 1976), but the method described here might be used successfully on other lichen species with different algal components. In this case some modification in the density of CsCl or KI solutions may be required.
Description1 page. Short Communication.
Appears in Collections:(IRN) Artículos

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