Bacillibactins E and F from a Marine Sponge-Associated Bacillus sp

Area of Science:

• Natural Product Chemistry
• Microbiology
• Biochemistry

Background:

• Marine sponges harbor diverse microbial communities, including bacteria like *Bacillus* species.
• Siderophores are crucial for microbial iron acquisition, with enterobactin being a well-studied example.
• The structural diversity of bacterial siderophores is key to understanding microbial adaptation and competition.

Purpose of the Study:

• To isolate and characterize novel secondary metabolites from a marine sponge-associated *Bacillus* species.
• To elucidate the structures and absolute configurations of newly discovered compounds, bacillibactins E and F.
• To propose a biosynthetic pathway for the novel siderophores, highlighting unique enzymatic activities.

Main Methods:

• Chemical investigation involving isolation and purification techniques.
• Extensive spectroscopic analyses (NMR, MS) for structural elucidation.
• Marfey's method for determining absolute configurations.
• Bioinformatic and biochemical approaches to propose biosynthetic pathways.

Main Results:

• Discovery and structural determination of bacillibactins E and F, novel cyclic triester siderophores.
• Identification of nicotinic and benzoic acid moieties within the siderophore structures, a first for bacterial siderophores.
• Elucidation of absolute configurations using Marfey's method.
• Proposal of a biosynthetic pathway involving a promiscuous enzyme (DhbE) responsible for incorporating the unique moieties.

Conclusions:

• Bacillibactins E and F represent a new class of bacterial siderophores with unique structural features.
• The findings expand the known structural diversity of iron-binding natural products.
• The proposed biosynthetic pathway provides insights into the enzymatic mechanisms governing siderophore production in bacteria.