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Results: 3

1.
FIG. 1

FIG. 1. From: The Pseudomonas Quinolone Signal Regulates rhl Quorum Sensing in Pseudomonas aeruginosa.

Effect of PQS on expression of quorum-sensing components in P. aeruginosa. Cultures of P. aeruginosa strain PAO-R1 (lasR) containing the indicated plasmid were grown for 18 h in the presence (black bars) or absence (hatched bars) of 50 μM PQS and assayed for β-Gal activity. Results are expressed in Miller units ± ςn−1 and are the means for duplicate β-Gal assays from at least three separate experiments. Reporter fusions contained on plasmids: pLPRI, rhlI′-lacZ; pPCS223, lasI′-lacZ; pPCS1001, lasR′-lacZ; pPCS1002, rhlR′-lacZ; pLP170, control vector with promoterless lacZ.

Susan L. McKnight, et al. J Bacteriol. 2000 May;182(10):2702-2708.
2.
FIG. 2

FIG. 2. From: The Pseudomonas Quinolone Signal Regulates rhl Quorum Sensing in Pseudomonas aeruginosa.

PQS production is initiated in early stationary phase. (A) PQS bioassays (see Materials and Methods) were performed on culture supernatant extracts prepared throughout the growth cycle of P. aeruginosa strain PAO-JP2(pECP39). Results were derived from duplicate β-Gal assays from at least four separate experiments and are expressed as the mean percentage + ςn−1 of the maximal activation seen during each separate growth curve experiment. (B) Viability and optical density curves for strains PAO-JP2(pECP39) (closed symbols) and PAO1 (open symbols). Cultures were sampled at various times during the growth cycle, and optical density (absorbance at 660 nm) was determined (squares). Samples were also serially diluted and plated to determine CFU per milliliter (triangles). Data are from at least two separate experiments performed in duplicate and are presented as the mean ± ςn−1.

Susan L. McKnight, et al. J Bacteriol. 2000 May;182(10):2702-2708.
3.
FIG. 3

FIG. 3. From: The Pseudomonas Quinolone Signal Regulates rhl Quorum Sensing in Pseudomonas aeruginosa.

Model of the P. aeruginosa quorum-sensing hierarchy. The quorum-sensing cascade begins with the induction of the las quorum-sensing system when cells reach a threshold density. Vfr induces lasR (1), and the concentration of 3-oxo-C12-HSL increases to the point where it binds to and activates LasR. The LasR–3-oxo-C12-HSL complex induces genes controlled by the las quorum-sensing system, including a negative regulator gene (rsaL) (3), rhlR, and an unidentified gene required for PQS production. PQS either directly or indirectly induces rhlI, which leads to the production of C4-HSL that binds to and activates RhlR. The RhlR–C4-HSL complex can then induce genes controlled by the rhl quorum-sensing system. At this time it is not known whether PQS is capable of directly activating RhlR or acts through another regulator. (Two additional unanalyzed LuxR homologs, which may play a role in the activity of PQS, are encoded by P. aeruginosa [www.pseudomonas.com].) Genes and proteins are indicated by thick arrows and unfilled circles, respectively. Plus or minus symbols indicate transcriptional activation or repression of the gene(s) at the end of an arrow, respectively. Blocking of the association between RhlR and C4-HSL by 3-oxo-C12-HSL is indicated by a minus symbol next to the arrow between 3-oxo-C12-HSL and C4-HSL at the bottom of the figure. Question marks indicate an unknown member(s) of the PQS synthesis pathway that is affected by LasR–3-oxo-C12-HSL.

Susan L. McKnight, et al. J Bacteriol. 2000 May;182(10):2702-2708.

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