Two recombinant plasmids, expressing ice nucleation activity, were constructed and named pCPP30inaZ and pCPP38inaZ. They were transferred to the ice-negative, xanthan-producing Xanthomonas campestris pv. campestris by electroporation. The transformants were used for co-production of xanthan gum and ice nuclei from sugar beet molasses. The highest values obtained were 20 g l(-1) and 10(18) ice nuclei ml(-1), respectively. The above values fulfil the criteria for industrial manipulation. This is the first report on co-formation of two products by a transformed X. campestris strain.