PMID:135755

Citation	Bassford, PJ Jr, Bradbeer, C , Kadner, RJ and Schnaitman, CA (1976) Transport of vitamin B12 in tonB mutants of Escherichia coli. J. Bacteriol. 128:242-7
Abstract	It is known that the tonB mutation in Escherichia coli is responsible for a defect in the transport of iron chelates. These are transported by systems that involve outer membrane components. We found that tonB mutants were also deficient in the secondary, energy-dependent phase of vitamin B12 transport, although the mutants have normal levels of B12 receptors on their cell surface. In addition, tonB mutants derived from vitamin B12 auxotrophs required elevated levels of B12 for normal growth. Maltose uptake, mediated by another transport system involving an outer membrane component, was unaffected by the tonB mutation.
Links	PubMed PMC232849
Keywords	Amino Acids/metabolism; Biological Transport, Active; Enterobactin/metabolism; Escherichia coli/growth & development; Escherichia coli/metabolism; Genes; Maltose/metabolism; Mutation; Protein Biosynthesis; Receptors, Drug; Vitamin B 12/metabolism
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Phenotype of	Taxon Information	Genotype Information (if known)	Condition Information	OMP ID	OMP Term Name	ECO ID	ECO Term Name	Notes
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: RK4126 NCBI Taxon ID: 83333	Genotype of Reference Strain: tonB⁺ Genotype of Experimental Strain : tonB2 in RK4128	Reference Condition:	0000252	metabolite accumalation	0000134	Transport assay evidence	Mutation in the tonB gene caused decreased uptake in Vitamin B₁₂. See Figure 1 for experiment results.
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: RK4126 NCBI Taxon ID: 83333	Genotype of Reference Strain: tonB⁺ Genotype of Experimental Strain : tonB(del)-trp in 1485F^-	Reference Condition:	0000252	metabolite accumalation	0000134	Transport assay evidence	Mutation in the tonB gene caused decreased uptake in Vitamin B₁₂. See Figure 1 for experiment results.
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: RK4126 NCBI Taxon ID: 83333	Genotype of Reference Strain: metE tonB⁺ Genotype of Experimental Strain : metE tonB2	Reference Condition:	0000252	metabolite accumalation	0000172	biochemical trait analysis evidence	It was seen through the use of a growth assay that the tonB mutation caused a decrease in Vitamin B₁₂ uptake. This was also seen in mutant strain's RK4128, RK4129 and RK4130. See table 3 for full experimental results.
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