The marine sponge Suberea ianthelliformis was investigated for new chemistry after the recent discovery that polyamines ianthelliformisamines A–C (1–3) – originally sourced from this Australian sponge – act as Pseudomonas aeruginosa biofilm inhibitors and antibiotic enhancers. Large-scale extraction and isolation studies resulted in the discovery of four new and minor natural products, ianthelliformisamines D–G (4–7) and the known steroid, aplysterol (8). Compounds 4–7 were fully characterised following 1D/2D NMR, MS and UV data analyses. All compounds were assessed for their inhibition on planktonic growth of P. aeruginosa PAO1 in addition to their ability to inhibit the formation of biofilms. None of the tested natural products inhibited planktonic growth or biofilm formation of PAO1 when screened at 50 µM. Ianthelliformisamine D (4) contains a rare N-(3-aminopropyl)-2-pyrrolidone moiety only found in <30 natural products. Owing to the novelty of compound 4, we undertook the first total synthesis of this natural product, which was achieved in three steps.

Aquaculture has become a crucial component of global food and nutrition security, offering a sustainable alternative to meet the growing demand for seafood while alleviating pressure on wild fish populations. Among various strategies to enhance aquaculture productivity, probiotics have gained considerable attention for their ability to improve fish growth performance, overall health and environmental farming conditions. This review explores the potential of Bacillus spp. as probiotics in fish farming, with particular emphasis on B. subtilis , B. licheniformis , B. amyloliquefaciens , B. velezensis , B. pumilus , B. coagulans and B. megaterium . Evidence indicates that Bacillus spp. can enhance fish growth performance by improving feed efficiency, promoting gut health and innate immune responses and contributing to improved water quality through enhanced nutrient cycling and reduced environmental pollutants. Among these species, B. subtilis emerges as the most extensively studied and applied, likely due to its robustness, abundance, safety and multifunctional probiotic properties. In contrast, other Bacillus spp. remain relatively underexplored, despite their potential to provide complementary or strain‐specific benefits. This review also highlights key knowledge gaps, including the limited understanding of probiotic mechanisms at the metabolomic level. Future research integrating multi‐omics approaches and evaluating both single‐ and multi‐strain Bacillus probiotics will be essential for optimising probiotic design and advancing sustainable aquaculture practices.

The marine environment is an underutilised resource in probiotic research despite its potential for unique and beneficial microbes. Bacterial probionts derived from the ocean are emerging in the probiotic research field as an area of interest. Bacillus species (spp.) are Gram-positive, endospore-forming bacteria. Due to their unique resilience and their generally recognised as safe (GRAS) status, they have gained traction as putative probiotics. Existing large-scale reviews into the probiotic potential of Bacillus spp. have focused on terrestrial species, with limited attention given to marine-derived species. This review aims to address this gap by evaluating marine-derived Bacillus spp. with a focus on their diversity, origins, sources and demonstrated potential as probionts.

Probiotics are known to improve gut microbiota balance, enhance food digestion, and support overall health. Among these, Bacillus species are particularly promising due to their safety, spore-forming ability, environmental resilience, and diverse enzymatic activities. However, most Bacillus probiotics used in industry are of terrestrial origin, leaving marine-derived strains largely unexplored. Utilising the untapped potential of marine microbial biomass, this study presents a multi-stage methodology for identifying and evaluating marine-derived Bacillus strains with probiotic potential. A structured screening pipeline was applied to 67 microbial isolates from the Great Barrier Reef sponges. Initial selection focused on essential probiotic characteristics, including growth, stability, safety, and survival under gastrointestinal conditions. Strains meeting these criteria were then assessed for desirable properties, including digestive enzyme production and pathogen inhibition. Using this workflow, three marine-derived Bacillus strains were identified as potential probiotics, one of which demonstrated strong antimicrobial activity against Salmonella enterica at 5 and 10 mg/mL (p < 0.01). These findings demonstrate the capability of marine-associated Bacillus as novel bioproducts with functional antimicrobial properties.

Tyrosinase catalyzes the rate-limiting steps of melanin production, posing as an important target for treating skin pigmentation. This study investigates bioactive human tyrosinase inhibitors from Xanthium strumarium L. using a combined strategy of cell lysate, cell-based, and zebrafish assays. In this study, the methanol extract of Xanthium strumarium L. was identified as a potent inhibitor against tyrosinase in a cell lysate assay utilizing human MM418C1 melanoma cells. Subsequent phytochemical analysis resulted in the isolation of 11 natural products, including 4-hydroxybenzoic acid (4HB), three nucleotides, four caffeoylquinic acids and three alkaloids. Biological activity evaluation of isolated compounds suggested that 4HB was a potent inhibitor against tyrosinase with an IC₅₀ value of 59.5 μg/mL. Further evaluations revealed that 4HB significantly reduced the melanin content by 40% at the concentration of 500 mg/mL in human MM418C1 melanoma cells. 4HB activity was finally confirmed in vivo, by the demonstration of 40% reduction in melanin production in live zebrafish at the concentration of 15.63 μg/mL.