Table 2.
Properties of rpo suppressors of ΔpriB and ΔpriB ΔrecG
| Suppressorisolatea | Gene affected | DNA sequence change(s)b | Allele designation | RNAP feature affected | Rifampicin resistancec | Stringent phenotyped | rpo* activitye |
|---|---|---|---|---|---|---|---|
| AM2064/2066 | rpoA | CCT (Pro293) to CTT (Leu) | rpoA[P293L] | Alpha C-terminal domain | < 5 | ND | Weak negative |
| AM2072/2075 | |||||||
| AM2067 | rpoA | CTG (Leu253) to CGG (Arg) | rpoA[L253R] | Alpha C-terminal domain | < 5 | ND | Weak negative |
| AM2074 | rpoA | GAA (Glu273) to GAT (Asp) | rpoA[E273D] | Alpha C-terminal domain | < 5 | None | Neutral |
| AM2174 | rpoA | AAA (Lys298) to AAT (Asn) | rpoA[K298N] | Alpha C-terminal domain | < 5 | ND | Weak negative |
| AM2071 | rpoA | TCA (Ser49) to ACA (Thr) | rpoA[S49T,S309P] | Alpha C-terminal domain (S309P) | < 5 | ND | Negative |
| TCC (Ser309) to CCC (Pro) | |||||||
| AM2070 | rpoB | CGT (Arg452) to CTT (Leu) | rpoB[R452L] | Non-transcribed ssDNA channel | 10 | Very weak | Weak negative |
| AM2073 | rpoB | GGT (Gly1260) to GAT (Asp) | rpoB[G1260D] | RNA exit channel | 10 | Strong | Positive |
| AM2060/2069 | rpoB | TCG (Ser1332) to TTG (Leu) | rpoB[S1332L] | RpoB:RpoC interface; RNA exit? | < 5 | Strong | Weak positive |
| AM2063 | rpoB | Δ(G1336-C1344) | rpoB[ΔD446-L448] | Point of template DNA re-annealing | 5 | Very weak | Positive |
| AM2059 | rpoC | Δ(A643-T660) | rpoC[ΔK215-R220] | β′B rudder in the DNA channel? | < 5 | Strong | Negative |
Except for AM2174, the suppressor isolates are derivatives of strain AM2055 (ΔlacIZYA ΔrecG::apra zjf920::Tn10 ΔpriB202) selected for their resistance to mitomycin C. AM2064 and AM2066 came from the same culture of AM2055 and therefore may be siblings. AM2072 and AM2075 could also be siblings, but are independent of AM2064 and AM2066. AM2174 is a mitomycin C-resistant derivative of AM2167 (ΔlacIZYA ΔrecG::apra zjf920::Tn10 ΔpriB202 yheR::kan). The rpoA[P293L] allele was also identified in two other independent isolates, namely AM2173 and AM2191 (Table S1).
As defined in parentheses by the amino acid substitution(s) or deletion.
Strains were tested for growth on LB agar supplemented with rifampicin to a final concentration of 5, 10, 15, 20 or 50 μg ml−1. The parent strains show no resistance to rifampicin at 5 μg ml−1. The maximum concentration of rifampicin allowing growth to single colonies is indicated.
As determined by the ability of the rpo allele to allow a relA spoT strain to grow on minimal agar, i.e. to confer prototrophy (Cashel et al., 1996).
As determined from the survival of a ΔruvABC derivative irradiated with UV light at doses ranging from 5 to 60 J per m2 (McGlynn and Lloyd, 2000). Neutral: no effect; positive: improves survival; negative: reduces survival.