The outermost surface structures in chroococcacean cyanobacteria

Abstract

This is the 1st comparative study on the nature and occurrence of the outermost surface structures in chroococcacean cyanobacteria. All the stuctures are similar to those of other bacteria and not specific to only cyanobacteria. Twenty-two chroococcacean strains (1 Microcystis, 7 Synechocystis, 12 Synechococcus and 2 Gloeothece) were included in the study. Two Synechocystis strains had a glycocalyx layer. The 2 Gloeothece strains had a characteristic sheath and the space between the sheath and the cells contained loosely packed material. On the basis of their preferential staining with ruthenium red, the sheath and the loosely packed material most probably consist of acidic polysaccharides. M. firma, 3 Synechocystis strains, and 1 Synechococcus strain were surrunded by a regularly structured surface layer consisting of hexagonally arranged subunits. M. firma, all 7 Synechocystis and 3 Synechococcus strains possessed pili. The pili of some strains occurred as bundles. None of the strains produced spinae. Some structures described in previous studies are reinterpreted according to the findings of the present study.