Amino sugar sensitivity in Escherichia coli mutants unable to grow on N-acetylglucosamine

Abstract

Studies were conducted on two mutants of Escherichia coli that lack either glucosamine-6-phosphate deaminase or N-acetylglucosamine-6-phosphate deacetylase and which accumulate glucosamine-6-phosphate or N-acetylglucosamine-6-phosphate, respectively, when grown in the presence of N-acetylglucosamine. The addition of 10(-4) to 10(-5)mN-acetylglucosamine to these mutant strains caused a rapid and complete inhibition of growth on substrates that enter the catabolic pathways at or below the level of fructose-6-phosphate. Growth on glucose was inhibited to a lesser degree, whereas only minor inhibition occurred when the pentoses were used as substrates. Growth on gluconate was found to be totally unaffected by these levels of N-acetylglucosamine. The objective of this investigation was to determine the nature of this "amino sugar sensitivity" phenomenon and the conditions under which it could be overcome. It was found that this amino sugar sensitivity was abolished when an exogenous source of pentose such as uridine was included in the culture medium. Experiments are described indicating that the accumulated amino sugar phosphate metabolites interfere with an early step in hexose metabolism of both mutants, resulting in a pentose deficiency and consequent inhibition of growth on certain substrates.