Merck
  • Home
  • Search Results
  • A substrate ambiguous enzyme facilitates genome reduction in an intracellular symbiont.

A substrate ambiguous enzyme facilitates genome reduction in an intracellular symbiont.

BMC biology (2014-12-21)
Daniel R G Price, Alex C C Wilson
ABSTRACT

Genome evolution in intracellular microbial symbionts is characterized by gene loss, generating some of the smallest and most gene-poor genomes known. As a result of gene loss these genomes commonly contain metabolic pathways that are fragmented relative to their free-living relatives. The evolutionary retention of fragmented metabolic pathways in the gene-poor genomes of endosymbionts suggests that they are functional. However, it is not always clear how they maintain functionality. To date, the fragmented metabolic pathways of endosymbionts have been shown to maintain functionality through complementation by host genes, complementation by genes of another endosymbiont and complementation by genes in host genomes that have been horizontally acquired from a microbial source that is not the endosymbiont. Here, we demonstrate a fourth mechanism. We investigate the evolutionary retention of a fragmented pathway for the essential nutrient pantothenate (vitamin B5) in the pea aphid, Acyrthosiphon pisum endosymbiosis with Buchnera aphidicola. Using quantitative analysis of gene expression we present evidence for complementation of the Buchnera pantothenate biosynthesis pathway by host genes. Further, using complementation assays in an Escherichia coli mutant we demonstrate functional replacement of a pantothenate biosynthesis enzyme, 2-dehydropantoate 2-reductase (E.C. 1.1.1.169), by an endosymbiont gene, ilvC, encoding a substrate ambiguous enzyme. Earlier studies have speculated that missing enzyme steps in fragmented endosymbiont metabolic pathways are completed by adaptable endosymbiont enzymes from other pathways. Here, we experimentally demonstrate completion of a fragmented endosymbiont vitamin biosynthesis pathway by recruitment of a substrate ambiguous enzyme from another pathway. In addition, this work extends host/symbiont metabolic collaboration in the aphid/Buchnera symbiosis from amino acid metabolism to include vitamin biosynthesis.

MATERIALS
Product Number
Brand
Product Description

Calcium pantothenate, European Pharmacopoeia (EP) Reference Standard
USP
Glycerin, United States Pharmacopeia (USP) Reference Standard
Isoleucine, European Pharmacopoeia (EP) Reference Standard
Sigma-Aldrich
Glycerol solution, puriss. p.a., 86-89% (T)
Sigma-Aldrich
Glycerol solution, puriss., meets analytical specification of Ph. Eur., BP, 84-88%
USP
Calcium Pantothenate, United States Pharmacopeia (USP) Reference Standard
Sigma-Aldrich
Tetracycline, 98.0-102.0% (HPLC)
Sigma-Aldrich
Glycerin, meets USP testing specifications
Sigma-Aldrich
Ampicillin, meets USP testing specifications
Sigma-Aldrich
D-Pantothenic acid hemicalcium salt, ≥98.0%
Sigma-Aldrich
Glycerol solution, 83.5-89.5% (T)
Supelco
Glycerin, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
D-Pantothenic acid hemicalcium salt, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture
Sigma-Aldrich
Tetracycline, 98.0-102.0% (HPLC)
Sigma-Aldrich
Calcium pantothenate, meets USP testing specifications, monograph mol wt. 476.53 (C18H32CaN2O10)
Sigma-Aldrich
L-Isoleucine, reagent grade, ≥98% (HPLC)
Sigma-Aldrich
L-Isoleucine, from non-animal source, meets EP, JP, USP testing specifications, suitable for cell culture, 98.5-101.0%
Sigma-Aldrich
β-D-Allose, rare aldohexose sugar
Sigma-Aldrich
Glycerol, tested according to Ph. Eur., anhydrous
SAFC
L-Isoleucine
Sigma-Aldrich
Glycerol, FCC, FG
Sigma-Aldrich
Glycerol, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for electrophoresis, ≥99% (GC)
Sigma-Aldrich
Glycerol, for molecular biology, ≥99.0%
Sigma-Aldrich
Glycerol, BioXtra, ≥99% (GC)
Sigma-Aldrich
Glycerol, ≥99.5%
Sigma-Aldrich
Ampicillin, anhydrous, 96.0-102.0% (anhydrous basis)
Sigma-Aldrich
L-Isoleucine, BioUltra, ≥99.5% (NT)
Sigma-Aldrich
Glycerol, BioUltra, for molecular biology, anhydrous, ≥99.5% (GC)
Supelco
L-Isoleucine, certified reference material, TraceCERT®
Sigma-Aldrich
L-Isoleucine, 99%, FCC, FG