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The enzyme delta 6-desaturase is responsible for the conversion of linoleic acid (18:2) to gamma-linolenic acid (18:3 gamma). A cyanobacterial gene encoding delta 6-desaturase was cloned by expression of a Synechocystis genomic cosmid library in Anabaena, a cyanobacterium lacking delta 6-desaturase. Expression of the Synechocystis delta 6-desaturase gene in Anabaena resulted in the accumulation of gamma-linolenic acid (GLA) and octadecatetraenoic acid (18:4). The predicted 359 amino acid sequence of the Synechocystis delta 6-desaturase shares limited, but significant, sequence similarity with two other reported desaturases. Analysis of three overlapping cosmids revealed a delta 12-desaturase gene linked to the delta 6-desaturase gene. Expression of Synechocystis delta 6- and delta 12-desaturases in Synechococcus, a cyanobacterium deficient in both desaturases, resulted in the production of linoleic acid and gamma-linolenic acid.

The transfer of plasmids by mating from four Bacillus thuringiensis subspecies to Bacillus anthracis and Bacillus cereus recipients was monitored by selecting transcipients which acquired plasmid pBC16 (Tcr). Transcipients also inherited a specific large plasmid from each B. thuringiensis donor at a high frequency along with a random array of smaller plasmids. The large plasmids (ca. 50 between the presence of these plasmids in a strain and its corresponding donor ability. The results indicate that these large B. thuringiensis plasmids are self-transmissible plasmids which can also mobilize pBC16 and other plasmids. Several of the B. thuringiensis self-transmissible plasmids isolated in our laboratory were examined for DNA homology and entry exclusion effects, and evidence that the plasmids are distinct but related is presented. The

Gamma-linolenic acid (GLA), a nutritionally important fatty acid in human and animal diets, is not produced in oil seed crops. Many oil seed plants, however, produce significant quantities of linoleic acid, a fatty acid that could be converted to GLA by the enzyme delta 6-desaturase if it were present. As a first step to producing GLA in oil seed crops, we have cloned a cyanobacterial delta 6-desaturase gene. Expression of this gene in transgenic tobacco resulted in GLA accumulation. Octadecatetraenoic acid, a highly unsaturated, industrially important fatty acid, was also found in transgenic tobacco plants expressing the cyanobacterial delta 6-desaturase. This is the first example of engineering the production of 'novel' polyunsaturated fatty acids in transgenic plants.