Cell surface structure of Synechocystis sp. PCC6803 differs between the wild type and the glucose-tolerant strains

Abstract

Synechocystis sp. PCC6803 is a Gram-negative bacterium and has a cell surface structure composed of peptidoglycan, outer membrane, and surface layer (S-layer) from the inner side. We have shown that abundant hemolysin-like protein (HLP) binds to the S-layer of the glucose-tolerant strain (GT). Physiological function of HLP is unknown, although purified HLP is shown to be a trimer that binds Ca²⁺. In the present study, the wild type (WT) and the GT strains were compared in terms of Western blotting and immunoelectron microscopy with polyclonal antibodies to HLP. The results revealed that no HLP was present in WT. Furthermore, it was suggested that HLP binds Ca²⁺ in the S-layer. The existence of abundant Ca²⁺ on the cell surface may have some physiological and/or ecological meanings in GT.