Chryseochelins—structural characterization of novel citrate-based siderophores produced by plant protecting Chryseobacterium spp.

Abstract

Bacteria secrete siderophores whose function is to acquire iron. In recent years, the siderophores of several Chryseobacterium species were shown to promote the health and growth of various plants such as tomato or rice. However, the chemical nature of Chryseobacterium siderophores remained unexplored despite great interest. In this work, we present the purification and structure elucidation by NMR and MS/MS of chryseochelin A, a novel citrate-based siderophore secreted by three Chryseobacterium strains involved in plant protection. It contains the unusual building blocks 3-hydroxycadaverine and fumaric acid. Furthermore, the unstable structural isomer chryseochelin B and its stable derivative containing fatty acid chains, named chryseochelin C, were identified by mass spectrometric methods. The latter two incorporate an unusual ester connectivity to the citrate moiety showing similarities to achromobactin from the plant pathogen Dickeya dadantii. Finally, we show that chryseochelin A acts in a concentration-dependent manner against the plant-pathogenic Ralstonia solanacearum strain by reducing its access to iron. Thus, our study provides valuable knowledge about the siderophores of Chryseobacterium strains, which have great potential in various applications.

Chryseobacterium metallicongregator, sp. nov., a bacterium possessing metallophore activity towards rare earth elements

“…In regards to metallophore activity, when looking at the genome one can see ES2 T possess all the required genes for siderophore production and activity, specifically the mixed-type, citrate-hydroxamate based, aerobactin [46], similar to other Chryseobacterium , which also have mixed-type siderophores [6]. Specific genes for the chelation of other metals, such as the rare earth elements, have not been identified.…”

“…C138 siderophores to tomato plants also demonstrated a sufficient supply of iron for plant growth thus suggesting this genus’ dual ability of not only sequestering iron from the environment, but then resupplying to agriculture as necessary [5]. Other Chryseobacterium species possess siderophore activity [6, 7], suggesting that they may also be of use in similar fashion to C. herbae and Chryseobacterium sp. C138.…”

Siderophore synthetase-receptor gene coevolution reveals habitat- and pathogen-specific bacterial iron interaction networks

“…There is increasing evidence that siderophore-mediated interactions play a key role in this process 44,52 . For example, it was shown that plant-beneficial Chryseobacterium strains use their siderophores to suppress the plant-pathogen Ralstonia solanacearum 53 . The approach has recently been extended to human pathogens, which were found to be suppressed by exclusive siderophores from environmental Pseudomomnas spp.…”

SIDERITE: Unveiling Hidden Siderophore Diversity in the Chemical Space Through Digital Exploration

“…Digitalized natural product databases do not offer publicly accessible and searchable instances of "siderophore" and only contain a fraction of currently known siderophores. Previous case-by-case research on siderophores reported their siderophore discoveries by images of the structural formula [10][11][12][13][14] , as do previous reviews and the siderophore base. Although tools are available for converting chemical structure images to SMILES, their accuracy is limited [23][24][25] .…”

“…However, the database was last updated in 2013 and is no longer maintained. Moreover, new siderophore molecules (12)(13)(14)(15), and even new siderophore functional group types (diazeniumdiolate and 2-nitrosophenol) (16)(17)(18)(19), are constantly being discovered in various microorganisms. (3) Information regarding these siderophores is currently dispersed across various publications and needs to be systematically recorded.…”