Porphyridium purpureum microalga physiological and ultrastructural changes under copper intoxication

Abstract

The present work assessed the effect of copper (Cu) on cell dynamics and structure of the microalga Porphyridium purpureum (Rhodophyta, Bangiophycidae). Ultrastructure of the microalga was investigated and fluorescence of chlorophyll a and phycoerythrin, and content of reactive oxygen species (ROS) were estimated by flow cytometry. The number of cells did not show statistically significant differences at concentrations of 50 and 100 μg/L of Cu compared to the control, whereas 150 μg/L of Cu inhibited population growth. The fluorescence of chlorophyll a increased following exposure to Cu 100 μg/L and fluorescence of phycoerythrin enhanced by Cu 150 μg/L. There was no alteration in the above indicators at other concentrations. The content of ROS increased with increasing Cu concentration in a dose-dependent manner. The population size structure was also changed by Cu as the number of cells sized 4-6 μm was increased in the presence of Cu, especially with Cu 150 μg/L. Changes in the topography of thylakoids grew larger with Cu concentration.

Keywords: Aquatic pollution; Copper; Fluorescence; Photosynthetic pigments; Porphyridium purpureum; Reactive oxygen species; Rhodophyta; Ultrastructure.

Graphical abstract

Fig. 1

Size structure of the microalgae Porphyridium purpureum population in control and presence of copper in the medium. A – the third day; B – the seventh day.

Fig. 2

Ultrastructure of the microalga Porphyridium purpureum in presence of copper in the medium. A – control, general view, arrow indicates to mucopolysaccharide envelope; B – control, the location of thylakoids in the chloroplast: arrows indicate to phycobilisomes; C – copper content of 50 μg/L, general view, arrow indicates a mucopolysaccharide envelope; D – copper content of 50 μg/L, the location of thylakoids in the chloroplast: arrows indicate phycobilisomes; E – copper content of 100 μg/L, general view, arrow indicates a mucopolysaccharide mucous envelope; F – copper content of 100 μg/L, the location of thylakoids in the chloroplast: arrows indicate phycobilisomes; G – with a copper content of 150 μg/L, general view; nucleolus is indicated with a short arrow; the long arrow indicates the mucopolysaccharide mucous envelope; H – with a copper content of 150 μg/L, the location of thylakoids in the chloroplast; arrows indicate phycobilisomes. Designations: ch – chloroplast, p – pyrenoid, arrow indicates to mucopolysaccharide mucous envelope, nu – nucleus.