A Gram-stain-negative, aerobic, non-spore-forming, rod-shaped, non-motile, yellow-pigmented bacteria, designated strain G5-32T, belonging to the genus Kaistella was isolated from soil collected in the Antarctic. The strain was identified using a polyphasic taxonomic approach. The strain grew in the presence of 0–5% (w/v) NaCl (optimum, 1%), at pH 6.0–9.0 (optimum, pH 8.0) and at 4–28 °C (optimum, 20 °C). The predominant menaquinone was MK-6 (99.4%). The major fatty acids were anteiso-C15:0 (28.2%), iso-C15:0 (16.4%), summed feature 9 (comprising iso-C17:1 ω9c and/or 10-methyl C16:0; 10.6%) and iso-C16:0 (5.9%). A phylogenetic tree based on 16S rRNA gene sequences showed that strain G5-32T formed a lineage within the genus Kaistella with the closest phylogenetic neighbours Kaistella yonginensis HMD1043T, Kaistella chaponensis DSM 23145T, Kaistella jeonii DSM 17048T and Kaistella carnis NCTC 13525T (97.9, 97.8, 97.8 and 98.0 % 16S rRNA gene sequence similarity, respectively). The ANI values between strain G5-32T and K. jeonii DSM 17048T, K. chaponensis DSM 23145T, K. carnis NCTC 13525T and K. yonginensis HMD1043T were 90.9, 82.6, 77.1 and 76.3%. Concurrently, digital DNA–DNA hybridization values of strain G5-32T assessed against K. jeonii DSM 17048T, K. chaponensis DSM 23145T, K. carnis NCTC 13525T and K. yonginensis HMD1043T were 42.3, 25.9, 21.7 and 21.3%, respectively. Based on phenotypic, phylogenetic and genotypic data, a novel species, Kaistella gelatinilytica sp. nov., is proposed. The type strain is G5-32T (=CCTCC AA 2019083T=KCTC 72766T).

Depsides and their derivatives are a class of polyketides predominantly found in fungal extracts. Herein, a silent nonreducing polyketide synthase (TalsA)-containing gene cluster, which was identified from the Antarctic sponge-derived fungus Talaromyces sp. HDN1820200, was successfully activated through heterologous expression in Aspergillus nidulans. This activation led to the production of two novel depsides, talaronic acid A (1) and B (2), alongside three known compounds (3–5). The further co-expression of TalsA with the decarboxylase (TalsF) demonstrated that it could convert 2 into its decarboxylated derivative 1. The structural elucidation of these compounds was achieved using comprehensive 1D and 2D-NMR spectroscopy, which was complemented by HR-MS analysis. Talaronic acids A and B were firstly reported heterodimers of 3-methylorsellinic acid (3-MOA) and 5-methylorsellinic acid (5-MOA). All isolated compounds (1–5) were tested for their anti-inflammatory potential. Notably, compounds 1 and 2 exhibited anti-inflammatory activity comparable to that of the positive control. These results further enrich the structural class of depside natural products.

A membrane-dependent methyltransferase acts as a molecular switch, diverting a dihydroxybenzyl alcohol precursor toward dedicated para -quinone methide biosynthesis and oligomerization.

Three new structures named naphpyrone I–K (1–3) that contain a 6/6/6/6 oxaphenalene pyranone skeleton were isolated and purified from a marine-derived Streptomyces sp. HDN155000. Their chemical structures, including configurations, were elucidated by extensive NMR, MS, single-crystal X-ray diffraction, theoretical NMR calculations, DP4+ probability analysis, and ECD analyses. Naphpyrone K (3) showed cytotoxic activities against L-02, K562, NCI-H446/EP, MDA-MB-231, and NCI-H446 cancer cells with IC₅₀ values of 5.13, 3.34, 2.50, 2.61, and 2.20 μM, respectively. These findings highlight the potential for screening and developing therapeutic drugs from aromatic polyketides derived from marine actinobacteria.