TABLE 1.
Motility and flagellar synthesis are defective in DamOP derivatives of Salmonella clinical isolates
| Straina | Serovar (serogroup) | Motilityb (area in cm2)
|
Flagellar synthesisc (mutant/wild-type)
|
||||
|---|---|---|---|---|---|---|---|
| dam+ | dam mutant | DamOP | dam+ | dam mutant | DamOP | ||
| MT2425 (FlhC−) | Typhimurium (B) | 0.031 | 0.031 | 0.031 | 0.0078 | 0.0078 | 0.0078 |
| Laboratory strains | |||||||
| LT2 | Typhimurium (B) | 11.0 | 2.3 | 10.1 | 1 | 1 | 1 |
| LT7 | Typhimurium (B) | 17.3 | 2.3 | 12.3 | 1 | 1 | 1 |
| Pathogenic strains | |||||||
| ATCC 14028 | Typhimurium (B) | 16.3 | 5.9 | 0.34 | 1 | 1 | 0.0156 |
| UK-1 | Typhimurium (B) | 16.8 | 5.1 | 0.38 | 1 | 1 | 0.0078 |
| F98 | Typhimurium (B) | 17.5 | 5.9 | 0.72 | 1 | 1 | 0.0078 |
| TY1212 | Typhimurium (B) | 14.9 | ND | 0.28 | 1 | ND | 0.0078 |
| 03-721 | Newport (C2) | 16.6 | ND | 1.81 | 1 | ND | 0.25 |
| K00-670 | O6,14,24:e,h− monophasic (H) | 14.2 | ND | 0.31 | 1 | ND | 0.0156 |
| Field isolates | |||||||
| EPIMD142 | Typhimurium var. Copenhagen (B) | 14.51 | ND | 0.45 | 1 | ND | 0.0156 |
| EPIMD144 | Istanbul (C3) | 16.61 | ND | 1.91 | 1 | ND | 0.0156 |
| BL9W2FL | Thompson (C1) | 15.19 | ND | 0.67 | 1 | ND | 0.0312 |
| CH10W4WI | Montevideo (C1) | 5.55 | ND | 0.34 | 1 | ND | 0.0156 |
| NM 1-41 | Kentucky (C3) | 16.10 | ND | 0.41 | 1 | ND | 0.0312 |
| NM 26-71 | Anatum (E1) | 16.10 | ND | 2.54 | 1 | ND | 0.0312 |
| NM 27-07 | Montevideo (C1) | 9.23 | ND | 2.08 | 1 | ND | 0.0312 |
| NM 25-06 | Meleagridis (E1) | 10.51 | ND | 0.83 | 1 | ND | 0.0312 |
| NM 25-46 | Sandiego (B) | 17.78 | ND | 7.06 | 1 | ND | 1 |
| NM 28-54 | Cerro (K) | 10.34 | ND | 0.83 | 1 | ND | 0.0625 |
| NM 30-31 | Paratyphi B var. Java (B) | 17.56 | ND | 2.16 | 1 | ND | 0.0312 |
Salmonella pathogenic strains used in this study were derived from Typhimurium strain ATCC 14028 (CDC 6516-60), UK-1 (43); F98 (6, 43); Typhimurium TY1212 and O6,14,24:e,h− monophasic K00-670 (29, 30) were recovered from recent virulent calf and poultry outbreaks, respectively, and were obtained from the California Animal Health and Food Safety Laboratory; Newport 03-721 was recovered from a recent calf outbreak and was obtained from Veterinary Medical Teaching Hospital Microbiology Lab at the University of California, Davis. All Salmonella field isolates were obtained from the USDA-ARS. Typhimurium avirulent laboratory strains were derived from LT2 (25, 89) and LT7 (54, 89). ND, not determined.
dam+, dam mutant, and DamOP derivatives of Salmonella were inoculated into the center of soft agar motility plates (38) and incubated for 7 h at 37°C, and the motility area of the swarm was determined. For each strain, the assay was performed in triplicate and the average growth diameter of the swarm was determined; the standard deviation was <10% of the mean. FlhC− (flhC5456::MudJ) strain MT2425 was used as a nonmotile control (21).
Whole-cell protein extracts prepared from ∼107 cells were processed by SDS-PAGE (∼20 μg of protein/well), transferred to PVDF membrane (Pierce), and probed with Salmonella primary antibody H antiserum i (anti-FliC) or H antiserum 1 complex (anti-FljB) for Typhimurium or H antiserum eh (anti-FliC) for S. enterica O6,14,24:e,h− monophasic (Difco); for Salmonella field isolates, E. coli flagellum monoclonal antibody 15D8 (IgG1; BioVeris) was used as a primary antibody. Signal was detected as described in Materials and Methods. Units refer to relative mutant/wild-type levels of flagellin determined by Western analysis using flagellar antibodies. Protein extracts of dam+ strains were diluted 4- to 128-fold before the signal was equal to that observed in DamOP cells; values given are representative of at least three independent Western blots. FlhC− (flhC5456::MudJ) strain MT2425 was used as a nonmotile control (21).