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Understanding the mechanisms, structuring microbial communities in oligotrophic ocean surface waters remains a major ecological endeavor. Functional redundancy and metabolic tuning are two mechanisms that have been proposed to shape microbial response to environmental forcing. However, little is known about their roles in the oligotrophic surface ocean due to less integrative characterization of community taxonomy and function. Here, we applied an integrated meta-omics-based approach, from genes to proteins, to investigate the microbial community of the oligotrophic northern Indian Ocean. Insignificant spatial variabilities of both genomic and proteomic compositions indicated a stable microbial community that was dominated by Prochlorococcus, Synechococcus, and SAR11. However, fine tuning of some metabolic functions that are mainly driven by salinity and temperature was observed. Intriguingly, a tuning divergence occurred between metabolic potential and activity in response to different environmental perturbations. Our results indicate that metabolic tuning is an important mechanism for sustaining the stability of microbial communities in oligotrophic oceans. In addition, integrated meta-omics provides a powerful tool to comprehensively understand microbial behavior and function in the ocean.

Chemical investigation on the deep-sea-derived fungus Chaetomium globosum led to the isolation of nine compounds. By extensive analyses of the1D and 2D NMR as well as HRESIMS spectra, their structures were elucidated as xylariol A ( 1 ), 1,3-dihydro-4,5,6-trihydroxy-7-methyl-isobenzofuran ( 2 ), epicoccone B ( 3 ) epicoccolide B ( 4 ), chaetoglobosin G ( 5 ), chaetoglobosin Fex ( 6 ), cochliodone A ( 7 ), cochliodone B ( 8 ), and chaetoviridin A ( 9 ), assorting as four phenolics ( 1 - 4 ), two cytochalosans ( 5 - 6 ), and three azaplilones ( 7 - 9 ). Compounds 1 - 3 were firstly reported from C. globosum . Under the concentrations of 20 μg/mL, 1 , 2 , and 3 exhibited potent in vitro anti-HIV activity with the inhibition rates of 70%, 75%, and 88%, respectively.

Andrastones are unusual 6,6,6,5-tetracyclic meroterpenoids that are rarely found in nature. Previously, three andrastones were obtained from the rice static fermentation extract of the deep-sea-derived fungus Penicillium allii-sativi MCCC 3A00580. Inspired by one strain many compounds (OSMAC) approach, the oat static fermentation on P. allii-sativi was conducted. As a result, 14 andrastones were isolated by UV-guided isolation. The chemical structures of the nine new compounds (1–9) was established by comprehensive analysis of the NMR, MS, ECD, and X-ray crystallography and the five known ones (10–14) were assigned by comparing their NMR, MS, and OR data with those reported in literature. Compound 1 bears a novel hemiketal moiety while 2 is the first example to possess a novel tetrahydrofuran moiety via C-7 and C-15. All isolates were tested for anti-allergic bioactivity. Compound 10, 3-deacetylcitreohybridonol, significantly decreased degranulation with the IC50 value of 14.8 μM, compared to that of 92.5 μM for the positive control, loratadine. Mechanism study indicated 10 could decrease the generation of histamine and TNF-α by reducing the accumulation of Ca2+ in RBL-2H3 cells. These findings indicate andrastones could be potential to discover new anti-allergic candidate drugs.