COMPETITIVE ACCUMULATION OF BETAINES BY ESCHERICHIA-COLI K-12 AND DERIVATIVE STRAINS LACKING BETAINE PORTERS

Escherichia coli was grown in hyperosmotic media containing both glyci ne betaine and one other betaine. E. coli K-12 derivative WG439 (putP( -) proP(-) proU(-)) did not accumulate any of 15 betaines. Strains WG4 45 (putP(-) proP(-) proU(+)), WG443 (putP(-) proP(+) proU(-)) and the control strains all accumulated less betaine, (CH3N+-(CH2)(n)-COO-, wh en n was greater than 1. Accumulation was not detectable when n = 5. B oth L-and D-isomers of or-substituted betaines were accumulated by bot h strains WG443 and WG445, the D-isomers more slowly. Hydroxylated alp ha-substituted betaines were accumulated relatively more through the o smoregulated transport protein ProU than through ProP. In actively gro wing cultures glycine betaine appeared to be the preferred substrate f or accumulation, but the proportion of the second accumulated betaine increased as cultures approached stationary phase.