12 - Lipids of Blue-Green Algae (Cyanobacteria)

Abstract

This chapter discusses the lipids of blue-green algae. The blue-green algae constitute a large group within the prokaryotic kingdom. They are; however, similar to eukaryotic plants and algae in performing oxygenic photosynthesis with two types of photochemical reactions and having chlorophyll a as the major photosynthetic pigment. The blue-green algae are classified as Gram-negative bacteria, and their cell envelope is composed of the outer membrane and plasma membrane separated by a peptidoglycan layer. In addition, they have intracellular photosynthetic membranes, that is, the thylakoid membranes. Their membrane structure is similar to that of eukaryotic plant chloroplast, containing outer and inner envelope membranes, surrounding the thylakoid membranes. The thylakoid membranes of the blue-green algae contain chlorophyll α and β-carotene, and contain phycobilisomes attached to their outer surface. They are the site of both photosynthetic and respiratory electron transport. The plasma membrane and outer membrane, on the other hand, contain xanthophylls, but little or no chlorophyll α or β-carotene, and phycobilisomes are never seen attached to these membranes.