TABLE 1.
R. capsulatus Tn5 mutants showing an increased expression of nifH-lacZ in the presence of ammonium
| Strain | Localization of Tn5a | Size of cloned EcoRI fragmentb | β-Galactosidase activityc
|
|
|---|---|---|---|---|
| NH4+ | Serine | |||
| Parental straind | 30 | 1200 | ||
| M3-4 | hvrA (nt. 326/327) | 2.8 kb | 680 | 1980 |
| M7-1 | PnifH (nt. 1237/1238) | 9.8 kb | 1150 | 900 |
| M8-20 | PnifH (nt. 1234/1235) | 9.8 kb | 790 | 640 |
a
Numbers in parentheses correspond to the sites of Tn5 insertions relative to the previously published sequences of hvrA (3) and nifH (29), respectively.
b
The given numbers do not include the size of Tn5.
c
Cells were cultivated in RCV medium with either 7.5 mM NH4+ or 9.5 mM serine as nitrogen source. β-Galactosidase activities expressed in mU/mg of protein (nmoles of o-nitrophenol × min−1 × mg of protein−1) were determined as described elsewhere (6, 24). Data are means of at least three independent experiments and standard error was less than 20% in each case.
d
The parental strain was R. capsulatus W49I/R372I [nifA1(Con) nifH- lacZYA].