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Loss of malic enzymes leads to metabolic imbalance and altered levels of trehalose and putrescine in the bacterium Sinorhizobium meliloti

Overview of attention for article published in BMC Microbiology, July 2016
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Title
Loss of malic enzymes leads to metabolic imbalance and altered levels of trehalose and putrescine in the bacterium Sinorhizobium meliloti
Published in
BMC Microbiology, July 2016
DOI 10.1186/s12866-016-0780-x
Pubmed ID
Authors

Ye Zhang, Laura Anne Smallbone, George C. diCenzo, Richard Morton, Turlough M. Finan

Abstract

Malic enzymes decarboxylate the tricarboxylic acid (TCA) cycle intermediate malate to the glycolytic end-product pyruvate and are well positioned to regulate metabolic flux in central carbon metabolism. Despite the wide distribution of these enzymes, their biological roles are unclear in part because the reaction catalyzed by these enzymes can be by-passed by other pathways. The N2-fixing alfalfa symbiont Sinorhizobium meliloti contains both a NAD(P)-malic enzyme (DME) and a separate NADP-malic enzyme (TME) and to help understand the role of these enzymes, we investigated growth, metabolomic, and transcriptional consequences resulting from loss of these enzymes in free-living cells. Loss of DME, TME, or both enzymes had no effect on growth with the glycolytic substrate, glucose. In contrast, the dme mutants, but not tme, grew slowly on the gluconeogenic substrate succinate and this slow growth was further reduced upon the addition of glucose. The dme mutant strains incubated with succinate accumulated trehalose and hexose sugar phosphates, secreted malate, and relative to wild-type, these cells had moderately increased transcription of genes involved in gluconeogenesis and pathways that divert metabolites away from the TCA cycle. While tme mutant cells grew at the same rate as wild-type on succinate, they accumulated the compatible solute putrescine. NAD(P)-malic enzyme (DME) of S. meliloti is required for efficient metabolism of succinate via the TCA cycle. In dme mutants utilizing succinate, malate accumulates and is excreted and these cells appear to increase metabolite flow via gluconeogenesis with a resulting increase in the levels of hexose-6-phosphates and trehalose. For cells utilizing succinate, TME activity alone appeared to be insufficient to produce the levels of pyruvate required for efficient TCA cycle metabolism. Putrescine was found to accumulate in tme cells growing with succinate, and whether this is related to altered levels of NADPH requires further investigation.

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Geographical breakdown

Country Count As %
Canada 1 5%
Unknown 20 95%

Demographic breakdown

Readers by professional status Count As %
Student > Ph. D. Student 4 19%
Researcher 3 14%
Student > Master 3 14%
Other 2 10%
Student > Bachelor 1 5%
Other 3 14%
Unknown 5 24%
Readers by discipline Count As %
Agricultural and Biological Sciences 8 38%
Biochemistry, Genetics and Molecular Biology 4 19%
Veterinary Science and Veterinary Medicine 1 5%
Social Sciences 1 5%
Medicine and Dentistry 1 5%
Other 0 0%
Unknown 6 29%
Attention Score in Context

Attention Score in Context

This research output has an Altmetric Attention Score of 1. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 27 July 2016.
All research outputs
#20,336,031
of 22,881,154 outputs
Outputs from BMC Microbiology
#2,694
of 3,195 outputs
Outputs of similar age
#319,787
of 365,298 outputs
Outputs of similar age from BMC Microbiology
#85
of 100 outputs
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