Sh. Mangoli et al., IDENTIFICATION, MAPPING AND CHARACTERIZATION OF 2 GENES OF ESCHERICHIA-COLI K-12 REGULATING GROWTH AND RESISTANCE TO STREPTOMYCIN IN COLD, Journal of Genetics, 76(1), 1997, pp. 73-87
Escherichia coli MD1157, a routine isolate of AB1157 maintained in our
labora tory, was noticed to have spontaneously acquired two condition
al cold-dependent phenotypes: C-S (cold sensitivity) and Sm-SC (strept
omycin sensitivity in cold). C-S involved delayed appearance of visibl
e colonies on solid (LB or minimal) medium in cold (22 degrees C or be
low) without any loss of viability, and an extended lag period and lon
ger doubling time following a temperature downshift in liquid medium.
Sm-SC involved conditional suppression of the rpsL31-mediated streptom
ycin (Sm) resistance in cold, resulting in reduced colony forming abil
ity in the presence of Sm. This phenotype was seen only on LB plates a
nd weakly on minimal-medium plates containing some LB, but not on mini
mal medium alone. Genetic mapping traced these two phenotypes to mutat
ions in two genes mapping to the 14-15 min region of the standard E. c
oli map, which have been named gicA (growth in cold) and gicB respecti
vely. Comparison of MD1157 with transductants which had lost either on
e or both of these mutations showed that while gicB1 contributes only
to Sm-SC, gicA1 is associated with both C-S and Sm-SC. Comparison of t
hese strains with AB1157 suggested the involvement of a third, as yet
unidentified gene in causing these phenotypes.