Article Figures & Data
Figures
- FIG. 1.
Colony morphology of P. fluorescens F113. (A) F113 colonies recovered on SA plates after 4 weeks of alfalfa rhizosphere colonization. Colonies of different morphology are clearly observed. (B) Colonies of phenotypic variants C, F, and S after isolation and subculture on SA plates. The morphology of the colonies was maintained on subsequent cultures.
- FIG. 2.
Swimming (0.3% agar) and swarming (0.5 and 1% agar) of C, F, and S variants on SA plates. Swimming motility displayed on 0.3% agar plates presented concentric haloes, while swarming had a dendritic pattern. The C variant showed no swarming ability at any agar concentration.
- FIG. 3.
Flagellin production by P. fluorescens F113 phenotypic variants. (A) Polyacrylamide gel electrophoresis of total extracellular proteins. The overproduced FliC, of approximately 35 kDa, is marked with an arrow. Molecular size markers are indicated on the left. (B) Western blot analysis using an antiflagellin antiserum. Only the band corresponding to flagellin (marked with an arrow) was detected. Staining shows overproduction of FliC in variants F and S.
- FIG. 4.
Transmission electron microscopy of phenotypic variants. (A) C variant possesses one or two normal polar flagella. Bar, 500 nm. (B) F variant, and also S variant (not shown), possesses flagella more than twofold longer than those of variant C. Bar, 300 nm.
Tables
- TABLE 1.
Phenotypic variants isolated from different parts of alfalfa roots after rhizosphere colonization by P. fluorescens F113a
Root partb CFU (104) of phenotypic variants Total CFU (104) per root % of phenotypic variants per root Basal part <1 69.6 <1 Medium part 87.7 896.4 9.8 Root tip 13.1 55.7 23.5 ↵ a Roots were collected 3 weeks after inoculation. Experiments were done in triplicate, and results showed less than 15% standard variation.
↵ b Basal part, from the stem base to the beginning of secondary roots; medium part, the rest of the root system, including secondary roots; root tip, the last centimeter of the root.
- TABLE 3.
Summary of the phenotypic features of C, F and S variants
Characteristic C F S Colony morphology Compact, opaque Diffuse, translucent Diffuse, translucent Motility Normal Enhanced Enhanced fliC expression Normal Overexpressed Overexpressed Avg flagellum length (μm) 2.3 7.0 6.6 LPS profilea 3 4 3 Flocculation in liquid medium − + − Pyoverdin production on LB − + − Pyoverdin production on SA + ++ + Cyanide production + − + Exoprotease production + − + ↵ a Number of bands in the LPS O antigen.
