Genome-Wide Analyses of Proteome and Acetylome in Zymomonas mobilis Under N2-Fixing Condition

Zymomonas mobilis, a promising candidate for industrial biofuel production, is capable of nitrogen fixation naturally without hindering ethanol production. However, little is known about the regulation of nitrogen fixation in Z. mobilis. We herein conducted a high throughput analysis of proteome and protein acetylation in Z. mobilis under N2-fixing conditions and established its first acetylome. The upregulated proteins mainly belong to processes of nitrogen fixation, motility, chemotaxis, flagellar assembly, energy production, transportation, and oxidation–reduction. Whereas, downregulated proteins are mainly related to energy-consuming and biosynthetic processes. Our acetylome analyses revealed 197 uniquely acetylated proteins, belonging to major pathways such as nitrogen fixation, central carbon metabolism, ammonia assimilation pathway, protein biosynthesis, and amino acid metabolism. Further, we observed acetylation in glycolytic enzymes of central carbon metabolism, the nitrogenase complex, the master regulator NifA, and the enzyme in GS/GOGAT cycle. These findings suggest that protein acetylation may play an important role in regulating various aspects of N2-metabolism in Z. mobilis. This study provides new knowledge of specific proteins and their associated cellular processes and pathways that may be regulated by protein acetylation in Z. mobilis.

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Characterization of Mutations That Affect the Nonoxidative Pentose Phosphate Pathway in Sinorhizobium meliloti

Journal of Bacteriology ◽

10.1128/jb.00436-17 ◽

2017 ◽

Vol 200 (2) ◽

Cited By ~ 3

Author(s):

Justin P. Hawkins ◽

Patricia A. Ordonez ◽

Ivan J. Oresnik

Keyword(s):

Nitrogen Fixation ◽

Mutant Strain ◽

Pentose Phosphate Pathway ◽

Carbon Metabolism ◽

Sinorhizobium Meliloti ◽

Iron Acquisition ◽

Central Carbon Metabolism ◽

Pentose Phosphate ◽

Content Type ◽

Central Carbon

ABSTRACTSinorhizobium melilotiis a Gram-negative alphaproteobacterium that can enter into a symbiotic relationship withMedicago sativaandMedicago truncatula. Previous work determined that a mutation in thetkt2gene, which encodes a putative transketolase, could prevent medium acidification associated with a mutant strain unable to metabolize galactose. Since the pentose phosphate pathway inS. melilotiis not well studied, strains carrying mutations in eithertkt2andtal, which encodes a putative transaldolase, were characterized. Carbon metabolism phenotypes revealed that both mutants were impaired in growth on erythritol and ribose. This phenotype was more pronounced for thetkt2mutant strain, which also displayed auxotrophy for aromatic amino acids. Changes in pentose phosphate pathway metabolite concentrations were also consistent with a mutation in eithertkt2ortal. The concentrations of metabolites in central carbon metabolism were also found to shift dramatically in strains carrying atkt2mutation. While the concentrations of proteins involved in central carbon metabolism did not change significantly under any conditions, the levels of those associated with iron acquisition increased in the wild-type strain with erythritol induction. These proteins were not detected in either mutant, resulting in less observable rhizobactin production in thetkt2mutant. While both mutants were impaired in succinoglycan synthesis, only thetkt2mutant strain was unable to establish symbiosis with alfalfa. These results suggest thattkt2andtalplay central roles in regulating the carbon flow necessary for carbon metabolism and the establishment of symbiosis.IMPORTANCESinorhizobium melilotiis a model organism for the study of plant-microbe interactions and metabolism, especially because it effects nitrogen fixation. The ability to derive the energy necessary for nitrogen fixation is dependent on an organism's ability to metabolize carbon efficiently. The pentose phosphate pathway is central in the interconversion of hexoses and pentoses. This study characterizes the key enzymes of the nonoxidative branch of the pentose phosphate pathway by using defined genetic mutations and shows the effects the mutations have on the metabolite profile and on physiological processes such as the biosynthesis of exopolysaccharide, as well as the ability to regulate iron acquisition.

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