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.

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-methylthioaculose 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.

Inosine differs from the guanosine nucleoside only by the absence of the N2 amino group. Both nucleosides also have similar electrostatic potentials. Therefore, substituting I for G has been used to probe various properties of nucleic acids and to facilitate the interpretation of binding studies. In particular, the absence of the amino group permits the assessment of its importance in the binding of ligands to the minor groove of duplex DNA. It has been known for some time that an I-C base pair is of lower stability than a regular G-C base pair, which needs to be considered when making DNA constructs containing inosine. However, it is generally assumed that both base pairs are structurally highly similar. To test this assumption in an identical sequence environment, we have determined the fine structure of two hairpin DNA substrates that differ only in the substitution of an I-C base pair for a G-C base pair. The structures have been solved using nuclear magnetic resonance (NMR) restraints in conjunction with Mardigras and molecular dynamics. The structural data are complemented with thermodynamic and dynamic data to get a comprehensive evaluation of the consequences of G-C vs I-C base pair substitutions. Our data show a strong similarity in the structures of the hairpins, but a significant difference in the melting temperatures, T m . This difference is also reflected in the drastically decreased base pair lifetime of 7.4 milliseconds compared to the G-C base pair lifetime of 155 milliseconds. The substitution of I-C for G-C is to probe for specific effect due to the amino group is satisfactory, as long as the lowered thermal stability and the drastically increased local dynamics are considered.

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 leverage multi-omics big data analysis to directly establish a negative correlation between sulfonolipid (SoL) biosynthesis in the human gut microbiome and inflammatory bowel disease (IBD). We experimentally validate this informatic correlation in a mouse model of IBD, showing that SoLs are produced in higher abundance in non-IBD mice compared to IBD mice. We determine that SoLs consistently contribute to the immunoregulatory activity of SoL-producing human gut commensal strains. We further reveal that sulfobacin A (SoL A), a representative member of SoLs, primarily mediates its dual immunomodulatory activity through Toll-like receptor 4 (TLR4). We also demonstrate that SoL A interacts with TLR4 via direct binding to myeloid differentiation factor 2 and that SoL A competes with the natural ligand, lipopolysaccharide, for binding. Together, these results suggest that SoLs mediate a protective effect against IBD through TLR4 signaling and also showcase a widely applicable informatics-based approach to directly linking the biosynthesis of functional metabolites to human health.