title: Simultaneous presence of fhs and purT genes is disadvantageous for the fitness of Escherichia coli growth.
abstract: In bacteria, alternate mechanisms are known to synthesize N(10)-formyltetrahydrofolate (N(10)-formyl-THF) and formyl glycinamide ribotide (fGAR), which are important in purine biosynthesis. In one of the mechanisms, a direct transfer of one carbon unit from formate allows Fhs to convert tetrahydrofolate to N(10)-formyl-THF, and PurT to convert glycinamide ribotide (GAR) to fGAR. Our bioinformatics analysis of fhs and purT genes (encoding Fhs and PurT) showed that in a majority of bacteria (∼94%), their presence was mutually exclusive. A large number of organisms possessing fhs lacked purT and vice versa. The phenomenon is so penetrating that even within a genus (Bacillus) if a species possessed fhs it lacked purT and vice versa. To investigate physiological importance of this phenomenon, we used Escherichia coli, which naturally lacks fhs (and possesses purT) as model. We generated strains, which possessed fhs and purT genes in singles or together. Deletion of purT from E. coli in the presence or absence of fhs did not confer a detectable growth disadvantage in pure cultures. However, growth competition assays revealed that the strains possessing either of the single genes outcompeted those possessing both the genes suggesting that mutual exclusion of purT and fhs in organisms confers fitness advantage in mixed cultures.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Srinivas
authors.initials: S
authors.lastname: Aluri
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India.
authors.forename: Kervin
authors.initials: K
authors.lastname: Rex
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India varshney@mcbl.iisc.ernet.in uvarshney@gmail.com.
authors.forename: Umesh
authors.initials: U
authors.lastname: Varshney
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D019295:Computational Biology; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics*; D005574:Formate-Tetrahydrofolate Ligase / Q000235:genetics*; D017353:Gene Deletion; D056084:Genetic Fitness; D005998:Glycine / Q000031:analogs & derivatives / Q000378:metabolism; D019877:Hydroxymethyl and Formyl Transferases / Q000235:genetics*; D012265:Ribonucleotides / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D012265:Ribonucleotides; C402896:glycinamide ribonucleotide; D019877:Hydroxymethyl and Formyl Transferases; C494825:purT protein, E coli; D005574:Formate-Tetrahydrofolate Ligase; D005998:Glycine
keywords: anti-correlative presence of genes; growth competitions; growth fitness advantage