Studies of<i>Euglena gracilis</i>in aging cultures. I. Light microscopy and cytochemistry

Abstract

Cells of synchronously growing populations of Euglena gracilis Klebs were studied at intervals from logarithmic into late stationary phases of growth to determine morphological and cytochemical changes related to aging. Morphological changes included transformation of dividing to non-dividing cells as generation time (GT) reached infinity; decrease in cell counts as viability of cells decreased; increase in pH of the culture medium; clumping of cells and giant cell formation; loss of motility; and accumulation of orange-to-brown aging pigments. Cytochemical studies using Gomori technique and Burstone's azo-dye method revealed increase in acid-phosphatase precipitate reaction with increasing age of cultures. Localised initially near the reservoir, the reaction product subsequently spread towards the perinuclear area and, eventually, throughout the cytoplasm until the acid-phosphatase precipitate was widely distributed. Using NBT and TPT, SDH activity of comparable cell samples showed varied activity. Fluorochrome labelling with acridine orange, quinacrine mustard and benzpyrene suggested change in autofluorescence properties of certain organelles, such as the lipid bodies.