OSMOLARITY MODULATES THE EXPRESSION OF THE HHA PROTEIN FROM ESCHERICHIA-COLI

The effect of the osmolarity of the culture medium on the expression o f the hha gene of Escherichia coli was investigated. When cells were g rown in LB medium, expression reached a maximum in the exponential pha se of growth and decreased in the stationary phase. Increasing the osm olarity of the LB medium had no significant effect on the expression o f the hha gene, bur depletion of NaCl led to a significant decrease in expression. Expression of the hha gene is thus sensitive to the osmol arity of the growth medium. High levels of expression of the hha gene when cells are grown at medium to high osmolarity are consistent with the finding that the Hha protein appears to play Its main modulatory r ole when cells grow under these conditions. (C) 1998 Federation of Eur opean Microbiological Societies. Published by Elsevier Science B.V.