Cobalt-rich crusts are important metallic mineral resources with great economic potential, usually distributed on seamounts located in the Pacific Oc

A new agarase, AgaA _CN41 , cloned from Vibrio sp. strain CN41, consists of 990 amino acids, with only 49% amino acid sequence identity with known β-agarases. AgaA _CN41 belongs to the GH50 (glycoside hydrolase 50) family but yields neoagarotetraose as the end product. AgaA _CN41 was expressed and characterized.

Halometabolites, an important group of natural products, generally require halogenases for their biosynthesis. Actinomycetes from the Arctic Ocean have rarely been investigated for halogenases and their gene clusters associated, albeit great potential of halometabolite production has been predicted. Therefore, we initiated this research on the screening of halogenases from Arctic marine actinomycetes isolates to explore their genetic potential of halometabolite biosynthesis. Nine halogenase genes were discovered from sixty Arctic marine actinomycetes using in-house designed or previously reported PCR primers. Four representative genotypes were further cloned to obtain full coding regions through genome walking. The resulting halogenases were predicted to be involved in halogenation of indole groups, antitumor agent ansamitocin-like substrates, or unknown peptide-like compounds. Genome sequencing revealed a potential gene cluster containing the halogenase predicted to catalyze peptide-like compounds. However, the gene cluster was probably silent under the current conditions. PCR-based screening of halogenase genes is a powerful and efficient tool to conduct bioprospecting of halometabolite-producing actinomycetes from the Arctic. Genome sequencing can also identify cryptic gene clusters potentially producing new halometabolites, which might be easily missed by traditional isolation and chemical characterization. In addition, our study indicates that great genetic potential of new halometabolites can be expected from mostly untapped actinomycetes from the polar regions.

Three new indolyl diketopiperazine derivatives, penillines A and B (1 and 3), isopenilline A (2), together with seven known alkaloid compounds (E)-3-(1H-imidazole-4-yimethylene)-6-(1H-indl-3-ylmethyl)-2,5-piperazinediol (4), penilloid A (5), meleagrin (6), neoxaline (7), questiomycin A (8), N-(2-hydroxyphenyl)-acetamide (9), 2-benzoxazolinone (10), were isolated from the Antarctic soil-derived fungus Penicillium sp. SCSIO 05705. The new structures of 1–3 were elucidated on the basis of 1D and 2D NMR, mass spectra, CD spectra, and quantum chemical calculations. All the isolated compounds were tested for their antiviral (H1N1 and H3N2), antituberculosis, antibacterial, and cytotoxic activities. Among them, compounds 6–8 had significant in vitro cytotoxicities against the K562, MCF-7, A549, U937, Hela, DU145, HL60, and HT29 cell lines, with IC₅₀ values ranging from 2.73 to 17.7 μM. In addition, compound 8 showed potent antituberculosis activity with an MIC value of 3.91 μM, and the inhibition effect was close to the positive control INH (isoniazid, MIC 2.04 μM). A possible biogenesis pathway for compounds 1–7 was proposed.