The transcriptional programme of Salmonella enterica serovar Typhimurium reveals a key role for tryptophan metabolism in biofilms

Table 3 Phenotypic characteristics of deletion mutants and WT strain tested for motility, RpoS activity, calcofluor binding and changes in extracellular matrix.

Strain	Genotype	Biofilm Capacity^a	Motility	RpoS activity^b	Calcofluor binding^c			EPS production
					25°C	37°C	25°C^d	Morphology	37°C^d	Morphology
SL1344	wild-type	+	+	+	L	L	DR	R	DR	R
JH3185	ΔtrpE	---	+	+	L	L	DR	S	R	R/S
JH3187	ΔSTM0341	---	+	+	L	L	DR	R	DR	R
JH3180	ΔssrA	---	+	+	L	H	DR	R	DR	R
JH3181	ΔssrA/pssrAB	+	+	+	L	H	DR	S	DR	S
JH3179	ΔORF319	+	+	+	L	H	DR	R	DR	R
JH3182	ΔSTM2779	+	+	+	H	L	DR	S	DR	R
JH3183	ΔygaT	+	+	+	H	L	DR	R	DR	R
JH3184	ΔybaY	+	+	+	H	L	DR	R	DR	R
JH3186	ΔyhfG	+	+	+	H	L	DR	R	DR	R
JH3188	Δmtr	+	+	+	H	L	DR	R	DR	R
JH3189	ΔpspABCDEF	+	+	+	H	L	DR	R	DR	R
JH3142	ΔrpoS	---	+	---	---	---	W	R	W	S

a. Biofilm formation is based on attachment under static conditions after 24 and 48 h of growth in CFA medium at 25°C. Symbols: (+) = WT biofilm growth; (-) = severely reduced attachment.
b. RpoS activity as defined by catalase activity in the semi-quantitative assay as described by Zambrano et al., [106].
c. Calcofluor binding was assessed following growth of SL1344 and mutant strains at 25 and 37°C on CFA agar supplemented with fluorescent brightener 28. Fluorescence levels are reported as low (L) or high (H) as compared to a cellulose-deficient rpoS mutant (-).
d. Colony colour was reported as dark red (DR), red (R), or white (W) with dark red indicating WT EPS production. Colony morphology was assessed as rough (R) or smooth (S) following overnight growth on CFA agar supplemented with CR dye at 25 and 37°C. Colony morphology of WT SL1344 and mutant strains were compared to strain positive (S. Typhimurium LT2) and negative (ΔrpoS) for the rdar morphotype.

ISSN: 1471-2164