Campylobacter jejuni growing in liquid culture was found to exhibit gr
oss morphological changes with time. Exponentially growing cells showe
d typical short spiral forms. At mid-stationary phase the cells became
approximately twice the length of the exponential forms. Late station
ary/early decline phase cells were seen to be a mixture of coccal form
s and cells which were between 3 and 4 times the length of exponential
ly growing cells. Continued incubation of cultures eventually resulted
in a population largely of coccal forms. These morphological changes
have not previously been observed when Camp. jejuni has been grown on
agar-based solid medium. It is likely that such changes result from th
e differential expression of genes that control the timing of cell div
ision.