Random Tn5 mutagenesis over Azotobacter vinelandii mucoid strain ATCC 9046 produced strain LA21, a non-mucoid, non-encysting mutant, carrying the Tn5 insertion within a gene homologous to algK from Pseudomonas aeruginosa encoding a periplasmic protein. algK, algJ and algG were shown to be transcribed as part of the palg8-alg44-algK-algJ-algG operon. A non-polar algK mutant was constructed and showed a non-mucoid phenotype, indicating that algK is essential for alginate production.