TABLE 2.

Comparison of biofilm formation by Y. pseudotuberculosis and Y. pestis in different in vitro and in vivo environments

Species	Strain	Serotype	Pgm phenotypea	Biofilm formation
				In vitro		In vivo
				Microtiter wellb	Flow cellc	C. elegans nematodesd	X. cheopis flease
Y. pseudotuberculosis	K163	O1b	−	0.20 ± .03	Moderate	None	−
	K170	O2c	−	1.11 ± .12	Heavy	Intermediate	−
	K171	O3	−	0.59 ± .10	Weak	Severe	−
	YPIII(K1)	O3	−	0.49 ± .03	Moderate	Severe	−
	K174	O4a	−	0.27 ± .03	Heavy	Weak	−
	K175	O4b	−	0.25 ± .05	Heavy	None	−
	K177	O5a	−	0.17 ± .04	Weak	Intermediate	−
	K186	O9	−	0.34 ± .07	Moderate	None	−
	K199	Unknown	−	0.09 ± .05	Heavy	Weak	−
	PB1 ΔddhD-wzz	Rough	−	1.16 ± .06	Moderate	NDg	−
	PB1 ΔddhD-wzz(pHMS1.2)	Rough	+	1.37 ± .10	Heavy	NDg	−
Y. pestis	KIM6+	Rough	+	1.00	Heavy	NDg	+
	KIM6	Rough	−	0.01 ± .01	Weak	NDg	+/−f

^aShows pigmentation on Congo red agar.

^bMeans ± standard deviations of the results of three safranine-binding assays expressed relative to the results for Y. pestis KIM6⁺.

^cBiofilms were classed as heavy, moderate, or weak based on surface area coverage and depth as explained in Materials and Methods.

^dScoring for infection of C. elegans was based on accumulation of bacterial biofilm on the mouthparts of the nematodes and the effect on feeding and movement (data are from reference 29).

^e+, has the ability to form aggregates in the digestive tract and block fleas; −, does not have the ability to form aggregates in the digestive tract and block fleas.

^fForms aggregates in the midgut but does not block fleas (22).

^gND, not determined.