Electrochemical estimation of protoplast population

Abstract

The protoplast concentration of Bacillus licheniformis FDO150 was estimated with a combined electrode composed of a platinum anode, a platinum cathode and a saturated calomel electrode (S.C.E.). The anode was adjusted at +0.4 V vs. S.C.E. When the electrode was inserted in a protoplast suspension, the anodic current increased slightly. Addition of dichlorophenol-indophenol (DCIP) caused considerable increase in the output current. When protoplasts (0.5 mg ml −1 wet cells) were suspended in a high osmotic solution, the rate of current increase was 0.8 μA min −1. On the other hand, no anodic current was obtained when protoplasts were suspended in a low osmotic pressure solution. However, in the case of whole cells of B. licheniformis, an increase of anodic current was observed in a low as well as a high osmotic solution. The difference of the rates of current increase obtained both in a high and low osmotic solutions was correlated with protoplast concentration in the range from 10 −2 to 10 −5 unit, where 1 unit is defined as the frequency of osmotically sensitive cells.