Provided herein are mutant strains of Neisseria meningitidis which produce Kdo-free lipid A as well as the Kdo-free lipid A molecules and immunogenic compositions containing such Kdo-free lipid A molecules from a Neisseria strain containing a genetically stable mutation which inactivates a gene selected from the group consisting of genes encoding arabinose-5-phosphate isomerase, CMP-Kdo synthetase and CMP-Kdo transferase. N. meningitidis NMB206 is a specifically exemplified strain which harbors a stable insertion mutation in the gene (kpsF) encoding A5P isomerase; strain NMB-249 is a specifically exemplified strain with a stable insertion mutation in the gene (kdtA) encoding CMP-Kdo synthetase, and strain NMB259 is specifically exemplified strain with a stable insertion mutation in the gene (kdsB) encoding CMP-Kdo transferase. Also provided by the present invention are methods for the production of Lipid A flee of 3-keto-3-deoxyoctanoic acid using these genetically stable N. meningitidis mutants. Also describes is pYT250, a plasmid functional in neisseriae and in enterics such as Escherichia coli.