Identification and characterization of the Myxococcus xanthus argE gene

Abstract

The chromosomal acetylornithine deacetylase (argE) gene of Myxococcus xanthus was identified via homology to acetylornithine deacetylases from other bacterial species. A mutant carrying a disruption in argE was unable to grow on minimal media lacking supplemental arginine and formed fruiting bodies and spores in response to arginine starvation at high cell density.

FIG. 1

Partial restriction map of the 2.8-kb M. xanthus DK101 argE chromosomal region. Arrows indicate putative directions of transcription. The region 3′ to argE including the 3′ end of M. xanthus trcF is shown (for reference, see Garza et al. [4]). Restriction enzymes are abbreviated as follows: A, AccI; B, BamHI; E, EagI; S, SmaI (not all sites shown); S1, SacI. Solid lines indicate DNA regions used for insertion mutagenesis in orf2 (pBAR100) or argE (pBAR113) and expression of argE on the pBluescript lac promoter (pBAR114). A possible ribosome binding site (RBS) and initiator codon (ATG) for argE are shown.

FIG. 2

Best-fit alignments of the deduced acetylornithine deacetylase (argE) amino acid sequences from M. xanthus and E. coli. Black boxes with white lettering indicate amino acid identities, and gray boxes indicate similarities within groups by side chain.

FIG. 3

Complementation of an E. coli argE mutation by the M. xanthus argE gene. E. coli cells carrying a point mutation in argE were transformed with either pBluescript KS(+) (pBS KS+) or pBAR114 and assayed for growth on M9 minimal agar plates (14) with or without supplemental arginine (Arg). (Each quadrant of a single plate contains a separate isolate, and corresponding quadrants of the two plates contain the same isolate.) Both strains show growth on plates with supplemental arginine, but only the strain with pBAR114 grows in the absence of arginine.

FIG. 4

Fruiting body formation in the absence of supplemental arginine (Arg). Cells were spotted at high density (5 × 10⁹ cells/ml) on 0.8% agarose A1 plates with or without 0.1 mg of supplemental arginine/ml. M. xanthus MS2014 (sglA1 argE::pBAR113) forms fruiting bodies on A1 minimal media in response to arginine starvation, while strain DK101 (sglA1) does not. Magnification, ×8. Both strains show normal growth in the presence of supplemental arginine. Development of strain DK101 on TPM starvation agar is shown for reference. Magnification, ×6.