Pantothenate auxotrophy inZymomonas mobilisZM4 is due to a lack of aspartate decarboxylase activity

Abstract

AbstractThe bacteriumZymomonas mobilisnaturally produces ethanol at near theoretical maximum yields, making it of interest for industrial ethanol production.Z. mobilisrequires the vitamin pantothenate for growth. Here we characterized the genetic basis for theZ. mobilispantothenate auxotrophy. We found that this auxotrophy is due to the absence of a single gene,panD, encoding aspartate-decarboxylase. Heterologous expression ofEscherichia coliPanD inZ. mobilisor supplementation of the growth medium with the product of PanD activity, β-alanine, eliminated the need for exogenous pantothenate. We also determined that IlvC, an enzyme better known for branched-chain amino acid synthesis, is required for pantothenate synthesis inZ. mobilis, as it compensates for the absence of PanE, another pantothenate synthesis pathway enzyme. In addition to contributing to an understanding of the nutritional requirements ofZ. mobilis, our results have led to the design of a more cost-effective growth medium.