Scanning electron microscopy investigations on bis(2-ethylhexyl)phthalate treated Mycobacterium cells

Comparative investigation of steroid transforming activity and ultrastructural changes of bis(2-ethylhexyl)phthalate (BEHP, phthalate) treated Mycobacterium sp. NRRL B-3805 cells was carried out. Transformation of β-sitosterol into androstenedione (AD) and androstadienedione (ADD) was performed in phthalate medium by resting cells preincubated in the organic solvent for a period from 3 to 24 h. It was observed that a preincubation greater than 12 h leads to the development of dense formations on the cells surface, reduction in the cell turgor, disruption in the cell walls, and formation of zones with reduced electron density. The preincubation for 24 h causes deeper changes in the cell ultrastructure but the treated cells retain their steroid transforming activity, allowing up to 80% of the substrate to be converted into AD and ADD. A preincubation of the resting Mycobacterium cells in BEHP for 6 h might be recommended as it leads to an achievement of stoichiometrical transformation of the substrate into AD and ADD and slightly higher initial rate of the reaction performed.