In Rhizobium leguminosarum biovar viciae, the nodABC and nodFEL operons are involved in the production of lipo-oligosaccharide signals which mediate host specificity. The structure of these metabolites and those produced in nod mutants links the nodE and nodL genes to specific chemical features of the signal molecules. A nodE-determined, highly unsaturated fatty acid and a nodL-determined O-acetyl substituent are essential for the ability of the signals to induce nodule meristems on the host plant Vicia sativa.

A 2-0-methylfucose moiety is present in the lipo-oligosaccharide ABSTRACTBradyrhizobiumjaponicum is a soil bacterium that forms nitrogen-fixing nodules on the roots of the agronomically important legume soybean. Microscopic observation of plant roots showed that butanol extract of B. japonicum strain USDA110 cultures induced for nod gene expression elicited root hair deformation, an early event in the modulation process. The metabolite produced by B. japonicum responsible for root hair deformation activity was purified. Chemical analysis of the compound revealed it to be a pentasaccharide of N-acetylglucosamine modified by a Ci8:, fatty acyl chain at the

Dense time-series metabolomics data are essential for unraveling the underlying dynamic properties of metabolism. Here we extend high-resolution-magic angle spinning (HR-MAS) to enable continuous in vivo monitoring of metabolism by NMR (CIVM-NMR) and provide analysis tools for these data. First, we reproduced a result in human chronic lymphoid leukemia cells by using isotope-edited CIVM-NMR to rapidly and unambiguously demonstrate unidirectional flux in branched-chain amino acid metabolism. We then collected untargeted CIVM-NMR datasets for Neurospora crassa , a classic multicellular model organism, and uncovered dynamics between central carbon metabolism, amino acid metabolism, energy storage molecules, and lipid and cell wall precursors. Virtually no sample preparation was required to yield a dynamic metabolic fingerprint over hours to days at ~4-min temporal resolution with little noise. CIVM-NMR is simple and readily adapted to different types of cells and microorganisms, offering an experimental complement to kinetic models of metabolism for diverse biological systems.

The communities of bacteria that assemble around marine microphytoplankton are predictably dominated by Rhodobacterales, Flavobacteriales, and families within the Gammaproteobacteria. Yet whether this consistent ecological pattern reflects the result of resource-based niche partitioning or resource competition requires better knowledge of the metabolites linking microbial autotrophs and heterotrophs in the surface ocean. We characterized molecules targeted for uptake by three heterotrophic bacteria individually co-cultured with a marine diatom using two strategies that vetted the exometabolite pool for biological relevance by means of bacterial activity assays: expression of diagnostic genes and net drawdown of exometabolites, the latter detected with mass spectrometry and nuclear magnetic resonance using novel sample preparation approaches. Of the more than 36 organic molecules with evidence of bacterial uptake, 53% contained nitrogen (including nucleosides and amino acids), 11% were organic sulfur compounds (including dihydroxypropanesulfonate and dimethysulfoniopropionate), and 28% were components of polysaccharides (including chrysolaminarin, chitin, and alginate). Overlap in phytoplankton-derived metabolite use by bacteria in the absence of competition was low, and only guanosine, proline, and N-acetyl-d-glucosamine were predicted to be used by all three. Exometabolite uptake pattern points to a key role for ecological resource partitioning in the assembly marine bacterial communities transforming recent photosynthate.

Analysis of the lipids of Mycobacterium tuberculosis H37Rv, by both normal- and reverse-phase thin-layer chromatography, revealed a series of novel glycolipids based on 2,3-di-O-acyltrehalose. The structures of these acylated trehaloses were elucidated by a combination of gas chromatography-mass spectrometry, 1H, 13C, two-dimensional 1H-1H, and 1H-13C nuclear magnetic resonance spectrometry. The fatty acyl substituents were mainly of three types: saturated straight-chain C16-C19 acids; C21-C25 "mycosanoic acids"; and C24-C28 "mycolipanolic acids." Analysis of one of the major 2,3-di-O-acyltrehaloses by two-dimensional 1H-chemical shift correlated and 1H-detected heteronuclear multiple-bond correlation spectroscopy established that the C18 saturated straight-chain acyl group was located at the 2 position and that the C24 mycosanoyl substituent was at the 3 position of the same "right-hand" glucosyl residue. At least six molecular species differing only in their fatty acid content comprised this family of di-O-acylated trehaloses. We regard these acyltrehaloses as elemental forms of the multiglycosylated acyltrehaloses (the lipooligosaccharides) perhaps due to an inability of the majority of isolates of virulent tubercle bacilli to glycosylate core acyltrehaloses. The acyltrehaloses are minor but consistent components of virulent M. tuberculosis and apparently the basis of the specific serological activity long associated with its lipid fractions.