To determine the possible pathogenic effects of bacterial microflora in plant cells, we used a B. cereus strain and B. subtilis recombinant strains capable of producing HlyII in varying degrees. We also studied the effect of purified HlyII toxin on plant cells. The cell membrane of the freshwater alga Chara corallina was used, as cell membranes are the primary target of any interaction with microorganisms. Our choice was determined by the following considerations: 1) to date, the influence of hemolysin II on plant cells has not been investigated; 2) the assay is not purely artificial, because B. cereus and B. subtilis are widespread, occupy the same niche as Chara corallina and can interact with it in the environment [17], [18], [19], [20] and [21]; 3) cell size of this alga is more than one centimeter, which enables studies of a separate isolated cell; 4) existence of the cell wall with microfibrillar network makes it possible to study pore formation step by step; and 5) the stonewort alga is a convenient floral object with electrically excitable membrane, whose main channel types (calcium channels and calcium-activated chlorine channels) involved in the generation of action potentials have been adequately described [22] and [23]; therefore, any change in its parameters can be easily construed.
This study shows that B. cereus and B. subtilis strains secreting membrane-active toxin HlyII into the environment efficiently influence cells of the freshwater alga Chara corallina. Despite the cell wall formed by cellulose microfibrils, this hemolysin is capable of penetrating, with somewhat lower efficiency, into the algal membrane by passing through the periplasmic space and ultimately forming ion-conducting pores.