Effect of glucose and other carbon compounds on the transport of α-methylglucoside in Escherichia coli K12

The effect of glucose, succinate, sorbitol, glycerol and arabinose on the rate of uptake of α-[¹⁴C]methylglucoside by Escherichia coli K12 was studied in comparison with the effect of these substances on the rate of α-methylglucoside exit from cells preloaded with the radioactive compound.

Glucose was a very potent inhibitor of uptake and greatly accelerated exit, its effect on the former reaction exceeding four-fold that on the latter. Each of the other compounds tested was much less active than glucose and affected both uptake and exit of methylglucoside to a similar extent.

The inhibition of uptake and the acceleration of exit by glucose were not affected by sodium azide. On the other hand, azide practically abolished the effect of succinate and glycerol, both on the uptake and exit reactions and reduced to 50% the effect of sorbitol.

These results provide further support for the conclusion reached by Hoffeeet al. that α-methylglucoside is transported by a glucose permease and that the inhibitory effect of metabolizable compounds on its uptake is due to energy supply for the exit reaction. Another possible mechanism for acceleration of exit in the presence of hexitols and sugars is also discussed.