Table 1.
Properties of two types of FNR variant
| Class | Modification or replacement | Codon changes | Hemolytic phenotype | Anaerobic β-galactosidase activities with different promoter-lacZ reporters
|
|||
|---|---|---|---|---|---|---|---|
| hlyE- | FFpmelR- | FF+20pmelR- | FF-71.5pmelR- | ||||
| Parental and hybrid | FNR | − | 100 | 100 | 100 | 100 | |
| FNR-HlyX | +++ | 265 | nd | nd | nd | ||
| HlyX-FNR | ++++ | 215 | nd | nd | nd | ||
| HlyX | +++++ | 455 | nd | nd | nd | ||
| Type A (AR1) | Q41R + F92L (1) | CAG-CGG + TTC-CTC | ++++ | 305 | 91 | 507 | 118 |
| A95P (1) | GCA-CCA | ++ | 160 | 95 | 131 | 120 | |
| R197H (3) | CGT-CAT | ++++ | 210 | 100 | 128 | 110 | |
| S73F* | TCC-TTC | − | 43 | 34 | 8 | 5 | |
| Type B (AR3) | I81T (2) | ATC-ACC | ++ | 205 | 33 | 259 | 188 |
| G85D (3) | GAT-GAC | ++++ | 210 | 10 | 443 | 230 | |
| D86Q (1) | GAC-AAC | ++ | 240 | 24 | 252 | 189 | |
| F112S (2) | TTC-TCC | ++ | 240 | 36 | 237 | 163 | |
| G85A* | GGC-GCC | ++++ | 205 | 17 | 255 | 193 | |
The hemolytic phenotypes were scored after 16 h of anaerobic growth on blood agar using a scale of − to +++++, where − denotes no detectable hemolysis and +++++ represents the level observed with HlyX-containing cultures. The values for anaerobic hlyE-lacZ (hlyE), FFpmelR-lacZ (FFpmelR), FF+20pmelR-lacZ (FF+20pmelR), and FF-71.5pmelR-lacZ (FF-71.5pmelR) expression were derived from the β-galactosidase specific activities of different strains expressed as percentages of the values (610 Miller units for hlyE, 7,890 for FFpmelR, 470 for FF+20pmelR, and 3,680 for FF-71.5pmelR) observed with cultures containing a wild-type fnr plasmid (pGS24): three independent anaerobic cultures of each strain were grown in sealed bottles for 16 h at 37°C and assayed in duplicate. Figures in parentheses denote the numbers of independent isolates of a given type that were recovered.
*Archetypal FNR variants (13) that define AR1 (S73F) and AR3 (G85A).
nd, not determined.