TABLE 4.

Stress response accessory genes found among the three clusters

Location and type of genetic material	Cluster, subcluster, or isolatea					Predicted resistance function(s)	Reference(s)
	1	2	3a	3b	FSL R9-4003
Plasmid-borne genes and operons
bcrABC	−	+	+	+	+	QAC	94
clpL	+	−	+	+	+	Heat	41
gbuC	−	+	−	+	+	Osmotic stress	42, 43
npr	−	+	−	+	+	Oxidative stress	44, 45
cadA	+	+	+	+	+	Heavy metal	47
cadC	+	+	+	+	+	Heavy metal	47
copB	−	−	−	+	+	Heavy metal	49, 50
copY	−	+	−	+	−	Heavy metal	51
mco	−	−	−	+	+	Heavy metal	48, 50
merAB	−	−	−	−	+	Heavy metal	53
merR	−	−	−	−	+	Heavy metal	53
zosA	−	+	−	+	+	Heavy metal	52
Chromosome-borne gene and islets
qacH	FSL M6-0204	−	−	−	−	QAC	10
SSI-1	−	−	+	+	+	Acidic stress and high salt concentrations	8
SSI-2	+	−	−	−	−	Alkaline and oxidative stress	9

^aPlus and minus signs indicate the presence and absence, respectively, of the element.