Table II. Bacterial strains and plasmids.

Designation	Genotype/relevant characteristics	Source/reference
E.coli strains
BL21(DE3)	F–ompT hsdS (rB–mB–) gal λDE3 lysogen	Studier and Moffatt (1986)
XL1-Blue	recA1 endA1 gyrA96 thi-1 hsdR17 (rK–mK+) supE44 relA1 lac λ– [F′ lacIqZΔM15 proAB+ Tn10]	Bullock et al. (1987)
DH5α	F– recA1 endA1 gyrA96 thi-1 hsdR17 (rK–mK+) supE44 relA1 Δ(lacZYA-argF)U169 deoR phoA λ– φ80dlacZΔM15	Jessee (1986)
M182	Δ(lacIPOZYA)X74 galU galK rpsL150 (strA) mel	Casadaban and Cohen (1980)
M182 Δcrp	Δcrp derivative of M182	Busby et al. (1983)
DM0068	MG1655Δcrp::Cm	Kim et al. (1992)
RLG4649	M182 carrying chromosomal λCC(–41.5)-lacZ prophage	Savery et al. (1998)
RLG4650	M182 carrying chromosomal λCC(–61.5)-lacZ prophage	Savery et al. (in preparation)c
NJS1020	M182 carrying chromosomal λCC(–71.5)-lacZ prophage	Savery et al. (in preparation)c
NJS1001	Δcrp::Cm derivative of RLG4649	this work
NJS1011	Δcrp::Cm derivative of RLG4650	this work
WAM137	Δcrp::Cm derivative of NJS1020	this work
Plasmidsa
pHTT7f1NHαb	T7 φ10 promoter directing expression of rpoA on pET21a. His6-tag coding sequence present between the first two codons of rpoA	Tang et al. (1995)
pHTT7f1NHαΔ235	pHTT7f1NHα deleted for the C–terminal 94 codons of rpoA	Tang et al. (1995)
pMGM1b	pHTT7f1NHα with Bsu36I site overlapping codons 233–235 of rpoA	this work
pMGM2-pMGM11, pMGM31, pMGM34b	pMGM1 derivatives containing deletions or insertions within the linker coding region of rpoA	this work
pMKSe2	pUC19 derivative carrying rpoB (encoding RNA polymerase β subunit) under control of the lac promoter	Severinov et al. (1993)
pT7β′	pT76 derivative carrying rpoC (encoding RNA polymerase β′ subunit) under control of the T7 φ10 promoter	Zalenskaya et al. (1990)
pLHN12σ	pBR322 derivative carrying rpoD (encoding RNA polymerase σ subunit) under control of the T7 φ10 promoter	Savery et al. (1998)
pSR/lacUV5	pBR322 derivative carrying lacUV5 promoter cloned upstream of transcription terminator	Savery et al. (1998)
pSR/CC(–41.5)	pBR322 derivative carrying CC(–41.5) promoter cloned upstream of transcription terminator	Savery et al. (1998)
pSR/CC(–61.5)	pBR322 derivative carrying CC(–61.5) promoter cloned upstream of transcription terminator	Savery et al. (in preparation)c
pLAW2b	pBR322 derivative carrying rpoA under lpp/lacUV5 promoter control	Zou et al. (1992)
pMGM12-pMGM22, pMGM32, pMGM35b	pLAW2 derivatives in which rpoA contains the modified linker coding sequences from pMGM1-pMGM11, pMGM31 and pMGM34	this work
pBR322	general purpose cloning vector	Bolivar et al. (1977)

^aAll plasmids encode resistance to ampicillin.

^bα linker coding sequences are shown in Table I; α linker amino acid sequences are shown in Figure 1.

^cN.J.Savery, G.S.Lloyd, S.J.W.Busby, M.S.Thomas, R.H.Ebright and R.L.Gourse, in preparation.