The Ultrastructure of the Vegetative Cell of Blue-Green Algae

Abstract

SummaryAn electron.microscopic study has been made of thG vegetative cells of eight genera of the blue-green algae. A basic structure has been defined for the vegetative cell. There is a cytoplasmic matrix which extends throughout the cell. No membranebound organelles of the categories chloroplast, mitochondrion, nucleus, golgi body, and endoplasmic reticulum can be recognized therein. There are two regions within the cell. The peripheral region is distinguished by the presence of "photosynthetic" lamellae and various granular inclusions. The central region is distinguished by the presence of crystalline granules, and areas of low electron density which resemble the nucleoid regions of bacteria. Ribosome.like granules are seen scattered throughout the cytoplasmic matrix.Intercellular connections, involving the plasma membranes of adjacent cells, have been seen.

Functions, Compositions, and Evolution of the Two Types of Carboxysomes: Polyhedral Microcompartments That Facilitate CO 2 Fixation in Cyanobacteria and Some Proteobacteria

“…Carboxysomes were first identified as polyhedral cell inclusion bodies of unknown function in cyanobacteria and chemotrophic gammaproteobacteria (74)(75)(76)(77)(78) (Fig. 2 shows examples of electron micrographs of cyanobacterial carboxysomes).…”

Requirement of Fra proteins for communication channels between cells in the filamentous nitrogen-fixing cyanobacteriumAnabaenasp. PCC 7120

“…The other proposed means of communication requires structures between adjacent cells in the filament. Several structures connecting vegetative cells and heterocysts and vegetative cells with each other have been observed using freeze-fracture, conventional electron microscopy and cryo fixation with electron tomography (13)(14)(15)(16)(17). Different names have been given to these structures: microplasmodesmata, septosomes, septal junctions, or nanopores (12,13,18,19).…”

An immunological and electrophoretic comparison of the thylakoids from vegetative cells and heterocysts ofAnabaena cylindrica

“…These differences are supported by deficiencies in the polypeptide composition of the heterocyst thylakoids. In kinetic terms, such differences may arise during heterocyst differentiation and vegetative thylakoid dissolution (Wildon & Mercer, 1963;Lang & Fay, 1971). De novo synthesis of intracytoplasmic membranes may occur during heterocyst differentiation as proposed by Lang & Fay (1971), however, our SDS-electrophoresis studies imply that any such synthesis must only be of pre-existing molecular weight polypeptide species.…”

“…The photosynthetic lamellae (thylakoids) of the vegetative cells of Anabaena cylindrica typically have a concentric peripheral arrangement (Wildon & Mercer, 1963;Lang & Fay, 1971). In contrast, the heterocyst lamellar system exhibits a more even reticulate distribution throughout the cell.…”