pH stress can cause cell elongation in Bacillus and Clostridium species: aresearch note

Spoilage of low pH products by a wide range of sporeformers is often observ ed. Work was done to isolate these organisms and establish the minimum pH a llowing growth. At low pH values (below 4.3), a haziness or slight turbidit y was noted in the broths which did not correspond to an increase in cell n umbers determined by plate count. Microscopic investigations revealed the p resence of elongated cells or chains of rods in the lower pH broths which w ere not present in the higher pH broths. The elongated cell morphology disa ppeared when cells were returned to optimum pH conditions. Phillips, L. E., Humphrey, T. J., & Lappin-Scott, H. M. (1998). [Journal of Applied Microbi ology, 84 (5), 820-826] illustrated this with Salmonella when chilled. It i s concluded that cell elongation is a stress response to sub-optimal pH con ditions, which can revert and give a rapid apparent increase in cell number s when conditions become more favourable. (C) 2000 Elsevier Science Ltd. Al l rights reserved.