The transmembrane behaviors of Ca²⁺ to Escherichia coli cells have been studied by use of Fura-2 fluorescence probe. It has been found that Ca²⁺ is able to induce the formation of the so called competence of some bacterial cells, such as Escherichia coli, which results in the Horizonal Gene Transfer phenomenon. But it is not yet well known the role of Ca²⁺ in the procedure. It is significant to make it clear whether Ca²⁺ can transfer across the cellular membrane. In the present work, Fura-2, a kind of new fluorescence probe, was used to study the transmembrane behaviors of Ca²⁺ to Escherichia coli HB101 cells. It was found that extracellular Ca²⁺ could cross the cellular membrane of Escherichia coli cells and the amount of inpouring Ca²⁺ was correlative to the concentration of extracellular Ca²⁺. Kinetics based on stopped flow spectrofluorimetry indicated that the transmembrane behavior of Ca²⁺ to Escherichia coli cells was a quite fast process, i.e., within only 1 s. What is more, the cell in early log phase had the lowest concentration of intracellular Ca²⁺ and the highest capability of incepting extracellular Ca²⁺, as compared with cells in late log phase and stationary phase.

Key words: Fura-2, fluorescence probe, calcium ion, transmembrane behavior, Escherichia coli