TABLE 2.

Chemotactic and metabolic response of R. solanacearum strain K60 to various chemicals

Chemical	Utilization as the sole carbon sourcea	Halo by the semisolid motility plate chemotaxis assayb	Agarose plug assay
			Relative chemotactic responsec	Chemotactic response ratingd
d-Sugars
Fructose	+	−	0.92	−
Galactose	+	+	0.91	−
Glucose	+	−	0.71	−
Maltose	−	NA	0.91	−
Sucrose	+	−	0.93	−
Xylose	+	−	0.96	−
Organic acids
Citric acid	+	+	1.75	+
Malic acid	+	+	1.68	+
Succinic acid	+	+	1.01	−
Glucuronic acid	+	−	0.55	−
Galacturonic acid	+	+	0.69	−
l-Amino acids
Alanine	++	+	2.21	+
Arginine	+	−	1.18	−
Aspartic acid	++	+	3.83	++
Asparagine	++	+	2.62	++
Cysteine	−	NA	1.01	−
Glutamic acid	++	+	2.76	++
Glutamine	++	+	3.01	++
Glycine	−	NA	1.84	+
Histidine	++	−	1.27	−
Isoleucine	−	NA	2.78	++
Leucine	−	NA	2.76	+
Lysine	−	NA	1.75	+
Methionine	−	NA	2.02	+
Phenylalanine	−	NA	2.06	+
Proline	++	+	3.22	++
Serine	+	−	2.00	+
Threonine	+	−	1.23	−
Tryptophan	+	−	0.75	−
Tyrosine	++	+	1.62	+
Valine	+	−	1.96	+
Other
Mannitol	−	NA	0.70	−
Glycerol	+	−	0.37	−
Casamino Acids	+	+	4.58	++
Peptone	+	+	5.41	++
Yeast extract	+	+	1.96	++

^aUtilization of the chemicals as the sole carbon source was determined by culturing strain K60 starting at an OD₆₀₀ of 0.01 in defined BMM broth with the chemicals at the following concentrations: 10 mM for d-sugars, 10 mM for organic acids, 4 mM for l-amino acids, and 0.2% (wt/vol) for the other chemicals. After 24 h, the turbidity of culture was measured by OD₆₀₀, which indicated the multiplication of bacteria defined as follows: −, no growth (OD₆₀₀, <0.05); +, moderate growth (OD₆₀₀ between 0.05 and 0.3); ++, vigorous growth (OD₆₀₀, >0.3).

^bDetermined by the size of the swimming halo on minimal medium semisolid motility plate plus the tested compounds at the following concentrations: 10 mM for d-sugars, 10 mM for organic acids, 10 mM for l-amino acids, and 0.1% (wt/vol) for the other chemicals. Symbols: −, halo size is equal to that of nonmotile mutant K701; +, halo size at least twice as big as that of nonmotile mutant K701. NA, not assayed, because the chemical was not utilized by K60.

^cRCR is calculated as the number of bacterial cells per 0.01 mm² adjacent to the agarose plug containing the tested compound divided by the bacterial number per 0.01 mm² adjacent to the buffer-only agarose plug (negative control). The compounds were tested at the following concentrations: 1 mM for d-sugars, organic acids, l-amino acids, and 0.1% (wt/vol) for the other chemicals.

^dThe chemotactic response was rated and shown as follows: −, RCR of <1.60; +, RCR between 1.60 and 2.60; ++, RCR of >2.60.