Frankobactin Metallophores Produced by Nitrogen-Fixing Frankia Actinobacteria Function in Toxic Metal Sequestration

Abstract

A series of new metallophores, referred to as frankobactins, were extracted from cultures of the symbiotic and nitrogen-fixing actinobacterium Frankia sp. CH37. Structure elucidation revealed a 2-hydroxyphenyl-substituted oxazoline core and a chain composed of five proteinogenic and nonproteinogenic amino acids, suggesting nonribosomal peptide synthesis as the biosynthetic origin. By whole-genome sequencing, bioinformatic analysis, and comparison with other Frankia strains, the genetic locus responsible for the biosynthesis was detected. Spectrophotometric titration of frankobactin with Fe(III) and Cu(II) and mass spectrometry established the 1:1 (metal:frankobactin) coordination. Uptake experiments suggested that frankobactin A 1 (1) did not serve to recruit iron, but to detoxify Cu(II). As frankobactin A 1 prevents the cellular entry of Cu(II), it could play a crucial role in the symbiosis of Frankia sp. and its host in the reclamation of copper-contaminated soil.

Cyclopeptide Alkaloids from Discaria chacaye (Rhamnaceae) as Result of Symbiosis with Frankia (Actinomycetales)

“…CH37. Structure elucidation revealed a 2‐hydroxyphenyl‐substituted oxazoline core and a chain composed of five proteinogenic and nonproteinogenic amino acids, suggesting nonribosomal peptide synthesis as the biosynthetic origin [65] …”

“…Structure elucidation revealed a 2-hydroxyphenylsubstituted oxazoline core and a chain composed of five proteinogenic and nonproteinogenic amino acids, suggesting nonribosomal peptide synthesis as the biosynthetic origin. [65] The above mentioned work allows indicates that the presence of cyclopeptide alkaloids is strongly related to the presence of the symbiont Frankia sp. This result correlates with the bioinformatics analysis performed by Udwary et al, [24] where the gene sequence inspection for the strains of Frankia ACN14a, CcI3, and EAN1pec, revealed an unexpected number of secondary groups of metabolic biosynthesis genes, among which would occur those responsible for the biosynthesis of cyclopeptide alkaloids.…”

Genome Sequence of Halomonas sp. Strain MS1, a Metallophore-Producing, Algal Growth-Promoting Marine Bacterium Isolated from the Green Seaweed Ulva mutabilis (Chlorophyta)

“…The genome of Halomonas sp. strain MS1 was thus sequenced to study organic ligands as potential algal growth- and morphogenesis-promoting factors (AGMPFs) in Ulva development ( 9 ) through their contributions to metal acquisition and detoxification ( 8 – 10 ). To compensate for low iron bioavailability, bacteria frequently produce an excess of siderophores ( 11 ).…”

Crystallographic Deciphering of Spontaneous Self‐Assembly of Achiral Calciphores to Chiral Complexes

“…However, it remains largely unknown whether the production of the secondary metabolites is related to the extreme environmental stimuli to which the microbes are exposed. Among the microorganisms dwelled in specialized niches, some yielded siderophores [2] and metallophores [3] in response to the perturbations of the surrounding metallic ions to maintain the homeostasis of their metabolisms. The production of siderophores is the predominant defense mechanism of many pathogens, and they are essential in iron scavenging; siderophores usually act as virulence factors during interspecies competitions [4] .…”