Biosynthetic Enzyme-guided Disease Correlation Connects Gut Microbial Metabolites Sulfonolipids to Inflammatory Bowel Disease Involving TLR4 Signaling.

The trillions of microorganisms inhabiting the human gut are intricately linked to human health. At the species abundance level, correlational studies have connected specific bacterial taxa to various diseases. While the abundances of these bacteria in the gut serve as good indicators for disease progression, understanding the functional metabolites they produce is critical to decipher how these microbes influence human health. Here, we report a unique biosynthetic enzyme-guided disease correlation approach to uncover microbial functional metabolites as potential molecular mechanisms in human health. We directly connect the expression of gut microbial sulfonolipid (SoL) biosynthetic enzymes to inflammatory bowel disease (IBD) in patients, revealing a negative correlation. This correlation is then corroborated by targeted metabolomics, identifying that SoLs abundance is significantly decreased in IBD patient samples. We experimentally validate our analysis in a mouse model of IBD, showing that SoLs production is indeed decreased while inflammatory markers are increased in diseased mice. In support of this connection, we apply bioactive molecular networking to show that SoLs consistently contribute to the immunoregulatory activity of SoL-producing human microbes. We further reveal that sulfobacins A and B, two representative SoLs, primarily target Toll-like receptor 4 (TLR4) to mediate immunomodulatory activity through blocking TLR4's natural ligand lipopolysaccharide (LPS) binding to myeloid differentiation factor 2, leading to significant suppression of LPS-induced inflammation and macrophage M1 polarization. Together, these results suggest that SoLs mediate a protective effect against IBD through TLR4 signaling and showcase a widely applicable biosynthetic enzyme-guided disease correlation approach to directly link the biosynthesis of gut microbial functional metabolites to human health.

Identification and Biosynthesis of Pro-Inflammatory Sulfonolipids from an Opportunistic Pathogen Chryseobacterium gleum.

Sulfonolipids (SoLs) are a unique class of sphingolipids featuring a sulfonate group compared to other sphingolipids. However, the biological functions and biosynthesis of SoLs in human microbiota have been poorly understood. Here, we report the discovery and isolation of SoLs from a human opportunistic pathogen Chryseobacterium gleum DSM16776. We show for the first time the pro-inflammatory activity of SoLs with mice primary macrophages. Furthermore, we used both in vivo heterologous expression and in vitro biochemical reconstitution to characterize two enzymes, cysteate synthase and cysteate fatty acyltransferase, that are specifically involved in the biosynthesis of SoLs rather than other sphingolipids. Based on these two SoL-specific enzymes, our bioinformatics analysis showed a wider distribution of SoL biosynthetic genes in microbes that had not been reported as SoL producers. We selected four of these strains and verified their cysteate synthase and cysteate fatty acyltransferase activities in SoL biosynthesis. Considering this wider distribution of SoL-specific biosynthetic enzymes in the context of SoLs' activity in mediating inflammation, a common and fundamental biological process, it may suggest a more comprehensive function of SoLs at play.

Grincamycins P-T: Rearranged Angucyclines from the Marine Sediment-Derived Streptomyces sp. CNZ-748 Inhibit Cell Lines of the Rare Cancer Pseudomyxoma Peritonei.

While marine natural products have been investigated for anticancer drug discovery, they are barely screened against rare cancers. Thus, in our effort to discover potential drug leads against the rare cancer pseudomyxoma peritonei (PMP), which currently lacks effective drug treatments, we screened extracts of marine actinomycete bacteria against the PMP cell line ABX023-1. This effort led to the isolation of nine rearranged angucyclines from Streptomyces sp. CNZ-748, including five new analogues, namely, grincamycins P-T (1-5). The chemical structures of these compounds were unambiguously established based on spectroscopic and chemical analyses. Particularly, grincamycin R (3) possesses an S-containing α-l-methylthio-aculose residue, which was discovered in nature for the first time. All of the isolated compounds were evaluated against four PMP cell lines and some exhibited low micromolar inhibitory activities. To identify a candidate biosynthetic gene cluster (BGC) encoding the grincamycins, we sequenced the genome of the producing strain, Streptomyces sp. CNZ-748, and compared the BGCs detected with those linked to the production of angucyclines with different aglycon structures.