TABLE 2.

Spontaneous modifications in the gacS gene isolated from phase II sectors and phase II mutants of Pseudomonas sp. strain PCL1171

Origin	Mutation in gacS genea		Functional gene		Remarks	Affected GacS domain
	Nucleotide	Amino acid	gacA	gacS
Phase II Tn5luxAB mutantsb
Wild-type phase I	−	−	+	+	No mutations
PCL1574	cT899c-cG899c	L300-R300	+	−	Point mutation	Phosphotransfer
PCL1575	C154aa-T154aa	Q52-stop	+	−	gacS mutation	Periplasmic loop
PCL1575a			−	+	gacA mutation
PCL1575b	C154aa-T154aa	Q52-stop	−	−	gacA and gacS mutations	Periplasmic loop
PCL1576	aA329c-aG329c	N110-S110	+	−	Inverted repeat	Periplasmic loop
	115-bp inversion	N110-R147 (stop134)			Inversiond
Wild-type phase II sectorsc
Sector 1	12-bp deletion	A54PL56	NDe	−	Deletiond and point mutations	Periplasmic loop
	cT263t-cC263t	L88-P88
	gA1813g-gG1813g	Silent
Sector 3	ND	ND	ND	−	gacS mutation
Sector 4	C1981cg-T1981cg	P661-S661	ND	−	Point mutation	Phosphotransfer
Sector 9	ct_caat-ctT309caat	L103-frameshift	ND	−	1-bp insertiond	Periplasmic loop
Sector 16	tT2231a-tC2231a	L744-S744	ND	−	Tandem repeat	Phosphotransfer
	307-bp deletion				Deletiond
	ggC663-ggA663	Silent
Sector 18	cT182g-cC182g	L61-P61	ND	−	Point mutations	Periplasmic loop
	gC1124c-gT1124c	A375-V375				Phosphotransfer
Sector 5			ND	+	gacA mutation
Sector 2	cT443g-cC443g	L148-P148	ND	+	gacA mutation

^aNumbers indicate positions in the wild-type gacS sequence.

^bThe functional gacA/gacS component was determined by the introduction of pMP6562 (gacS) and pMP5565 (gacA). A plus sign indicates which component is functional; a minus sign indicates which component harbors mutations and is nonfunctional. In addition, strains PCL1565, PCL1568, and another eight phase II mutants had a functional gacA gene (gacS mutants), while PCL1564, PCL1573, PCL1566, PCL1568, and another eight phase II mutants had a functional gacA gene (gacS mutants), while PCL1564, PCL1573, PCL1566, PCL1567, and another nine phase II mutants had a functional gacS gene (gacA mutants).

^cThe functional gacA/gacS component was determined by complementation of PCL1572 (gacS::Tn5luxAB) by the gacS gene isolated from a phase II sector. A plus sign indicates that a phase I morphology was restored in PCL1572; a minus sign indicates that a phase II morphology was maintained after introduction of the gacS gene. In addition, the gacS genes isolated from another five sectors did complement PCL1572 (gacS::Tn5luxAB), suggesting that mutation of the gacA gene was responsible for the phase II phenotype in these sectors.

^dSee Fig. 1.

^eND, not determined.