Carbon catabolite repression in Thermoanaerobacterium saccharolyticum

Vasiliki Tsakraklides,David A Hogsett,Bethany B Miller,Christopher D Herring,A Joe Shaw

doi:10.1186/1754-6834-5-85

Abstract

BackgroundThe thermophilic anaerobe Thermoanaerobacterium saccharolyticum is capable of directly fermenting xylan and the biomass-derived sugars glucose, cellobiose, xylose, mannose, galactose and arabinose. It has been metabolically engineered and developed as a biocatalyst for the production of ethanol.ResultsWe report the initial characterization of the carbon catabolite repression system in this organism. We find that sugar metabolism in T. saccharolyticum is regulated by histidine-containing protein HPr. We describe a mutation in HPr, His15Asp, that leads to derepression of less-favored carbon source utilization.ConclusionCo-utilization of sugars can be achieved by mutation of HPr in T. saccharolyticum. Further manipulation of CCR in this organism will be instrumental in achieving complete and rapid conversion of all available sugars to ethanol.

Highlights

The thermophilic anaerobe Thermoanaerobacterium saccharolyticum is capable of directly fermenting xylan and the biomass-derived sugars glucose, cellobiose, xylose, mannose, galactose and arabinose
Results Cyclic adenosine monophosphate (cAMP)-independent carbon catabolite repression (CCR) in T. saccharolyticum M2476, the parent strain used in this study, was derived from the ethanologen strain M1442 [20] by deletion of the perR gene
We added 2deoxyglucose to microwell cultures containing a single sugar as the main carbon source. 2-deoxyglucose delayed growth in cellobiose (Figure 1B) but not glucose cultures (Figure 1A), indicating that 2-deoxyglucose led to CCR of cellobiose utilization

Summary

Introduction

The thermophilic anaerobe Thermoanaerobacterium saccharolyticum is capable of directly fermenting xylan and the biomass-derived sugars glucose, cellobiose, xylose, mannose, galactose and arabinose. It has been metabolically engineered and developed as a biocatalyst for the production of ethanol. The order in which sugars are utilized is frequently determined by a mechanism known as carbon catabolite repression (CCR) [1]. CCR ensures that the cell’s energy expenditure on sugar import and metabolism will be directed to the carbon source that is most accessible and allows for fastest growth [2,3]. Studies of CCR in firmicutes have revealed the importance of the Histidinecontaining Protein HPr [3,4,5]. Histidine-dephosphorylated HPr is phosphorylated by HPr kinase (HPrK) at Ser46 [6,7,8] and this form of the protein mediates repression in

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