FIG 6.
Effect of csrA on the activity of BarA. (A) Cultures of IFC5010 (csrA) harboring or not plasmid pMX539 (expressing uvrY and indicated as pUvrY), pMX540 (expressing uvrYD54Q and indicated as pUvrYD54Q), pMX541 (expressing both uvrY and barA and indicated as pUvrY-BarA), or pMX543 (having uvrY under control of the barA promoter and 5′-UTR and indicated as pUvrYPbarA), IFC5017 (csrA barA) harboring pMX543 (indicated as pUvrYPbarA), and IFC5015 (csrA pta::ackA) harboring pMX539 (indicated as pUvrY) were grown in LB medium the pH of which had been adjusted and buffered to 5.0, using 0.1 M homopiperazine-N,N′-bis-2-(ethanesulfonic acid) (HOMOPIPES). At an OD600 of 0.2, a sample was withdrawn, 7 mM acetate or formate was added to the medium, and samples were withdrawn every 10 min. Total RNA isolated from these samples was analyzed by Northern blotting using a CsrB-specific probe. The experiment was repeated three times in its entirety with essentially identical results. (B) Overnight cultures of the csrB-lacZ transcriptional fusion carrying IFC5010 (csrA), IFC5010 harboring plasmid pMX539 (indicated as pUvrY), pMX540 (indicated as pUvrYD54Q), pMX541 (indicated as pUvrY-BarA), or pMX543 (indicated as pUvrYPbarA), IFC5017 (csrA barA) harboring pMX543 (indicated as pUvrYPbarA), and IFC5015 (csrA pta::ackA) harboring pMX539 (indicated as pUvrY) were diluted to an OD600 of ∼0.05 in LB medium at pH 5.0 as described for Fig. 1B alone (squares) or in the presence of acetate (circles) and formate (diamonds). The average from four independent experiments is presented (standard deviations were less than 5% from the mean).