Bacillus cereus can attack the cell membranes of the alga Chara corallina by means of HlyII

We studied the influence of Bacillus cereus bacteria on cells of the freshwater alga Chara corallina. These bacteria and recombinant Bacillus subtilis strains are capable of producing the secreted toxin HlyII, which changes the electrophysiological parameters of the algal electrically excitable plasma membrane by forming pores. Cooperative incubation of bacterial cells, which carry active hlyII gene, and Chara corallina cells caused a decrease in the resting potential (V-m) and plasma membrane resistance (R-m) of algal cells. The efficiency of each strain was commensurable with its ability to produce HlyII. Purified hemolysin II caused a similar effect on V-m and R-m of intact and perfused cells. This protein changed the kinetics and magnitude of transient voltage-dependent calcium and calcium-activated chloride currents owing to the formation of additional Ca2+-permeable pores in algal cell membrane. Occurrence of the cellulose cell wall with pores 2.1 to 4.6 nm in diameter suggests that HlyII molecules reach the plasma membrane surface strictly as monomers. (C) 2012 Elsevier B.V. All rights reserved.