TEMPERATURE-DEPENDENT MEMBRANE FATTY-ACID AND CELL PHYSIOLOGY CHANGESIN COCCOID FORMS OF CAMPYLOBACTER-JEJUNI

The effect of temperature and the availability of nutrients on the tra nsition of spiral Campylobacter jejuni cells to coccoid forms was inve stigated. Ageing of spiral C. jejuni cells in either nutrient-poor or nutrient-rich environments resulted in the formation of nonculturable coccoid cells at 4, 12, and 25 degrees C after different periods, with the cells incubated at 4 degrees C in nutrient-deficient media remain ing culturable the longest. To study the phenomenon, ATP levels, prote in profiles, and fatty acid compositions were monitored under conditio ns where the transition from spiral to coccoid cells occurred. During storage, the levels of intracellular ATP were highest in cells incubat ed at low temperatures (4 and 12 degrees C) and remained constant afte r a small initial decrease. During the transformation from spiral to c occoid forms, no alteration in protein profiles could be detected; ind eed, inhibition of protein synthesis by chloramphenicol did not influe nce the transition. Furthermore, DNA damage by gamma irradiation had n o effect on the process. Membrane fatty acid composition of cocci form ed at low temperatures was found to be almost identical to that of spi ral cells, whereas that of cocci formed at 25 degrees C was clearly di fferent. Combining these results, it is concluded that the formation o f cocci is not an active process. However, distinctions between cocci formed at different temperatures were observed. Cocci formed at 4 degr ees C show characteristics comparable to those of spirals, and these c occi may well play a role in the contamination cycle of C. jejuni. How ever, spiral campylobacters can also play an important role in this cy cle, since these cells remain culturable for a long period, especially under nutrient-poor and low-temperature conditions.