FIGURE 1.

Organization of the S. meliloti acpXL-lpxXL gene cluster and analysis of cluster mutant LPS. A, the S. meliloti acpXL-lpxXL gene cluster is encoded on the chromosome of strain Rm1021. All gene products are predicted to be involved in the biosynthesis of the lipid A VLCFA. The vertical arrows below indicate the position of the plasmid insertions in the mutant strains. The expected sizes of the RT-PCR/PCR products (1–4) using the different primer pairs are indicated (see “Experimental Procedures” for primers used). B, RT-PCR was performed using the primer pairs shown in A with S. meliloti Rm1021 RNA. 16 S rRNA primers were used as a positive control for the integrity of the RNA. Reactions with (+) and without reverse transcriptase (−) added are shown. For control reactions (c), the RNA was replaced with a colony of Rm1021. C, SDS-PAGE analysis of the LPS from the indicated strains (pRF771 is a broad host range control plasmid; pSmacpXL, pSmfabZXL, pSmfabF2XL, pSmfabF1XL, pSmadhA2XL, and pSmlpxXL are wild-type versions of the disrupted genes cloned into pRF771). HMW and LMW LPS species are shown.