posted on 2021-07-02, 16:04authored byNguyet
A. Nguyen, Zhenjian Lin, Ipsita Mohanty, Neha Garg, Eric W. Schmidt, Vinayak Agarwal
Marine
sponges are prolific sources of bioactive natural products,
several of which are produced by bacteria symbiotically associated
with the sponge host. Bacteria-derived natural products, and the specialized
bacterial symbionts that synthesize them, are not shared among phylogenetically
distant sponge hosts. This is in contrast to nonsymbiotic culturable
bacteria in which the conservation of natural products and natural
product biosynthetic gene clusters (BGCs) is well established. Here,
we demonstrate the widespread conservation of a BGC encoding a cryptic
ribosomally synthesized and post-translationally modified peptide
(RiPP) in microbiomes of phylogenetically and geographically dispersed
sponges from the Pacific and Atlantic oceans. Detection of this BGC
was enabled by mining for halogenating enzymes in sponge metagenomes,
which, in turn, allowed for the description of a broad-spectrum regiospecific
peptidyl tryptophan-6-brominase which possessed no chlorination activity.
In addition, we demonstrate the cyclodehydrative installation of azoline
heterocycles in proteusin RiPPs. This is the first demonstration of
halogenation and cyclodehydration for proteusin RiPPs and the enzymes
catalyzing these transformations were found to competently interact
with other previously described proteusin substrate peptides. Within
a sponge microbiome, many different generalized bacterial taxa harbored
this BGC with often more than 50 copies of the BGC detected in individual
sponge metagenomes. Moreover, the BGC was found in all sponges queried
that possess high diversity microbiomes but it was not detected in
other marine invertebrate microbiomes. These data shed light on conservation
of cryptic natural product biosynthetic potential in marine sponges
that was not detected by traditional natural product-to-BGC (meta)genome
mining.