Marine-derived antimicrobial molecules from the sponges and their associated bacteria

Marine natural products

Covering: January to the end of December 2023This review covers the literature published in 2023 for marine natural products (MNPs), with 582 citations (541 for the period January to December 2023) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, the submerged parts of mangroves and other intertidal plants. The emphasis is on new compounds (1220 in 340 papers for 2023), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the progress in the study of prokaryote involvement in macro-invertebrate MNP production is discussed.

Epibiotic bacterial community composition varies during different developmental stages of Octopus mimus: Study of cultivable representatives and their secondary metabolite production

Marine microbial communities colonizing the skin of invertebrates constitute the primary barrier between host and environment, potentially exerting beneficial, neutral, or detrimental effects on host fitness. To evaluate the potential contribution of epibiotic bacteria to the survival of early developmental stages of Octopus mimus, bacterial isolates were obtained from eggs, paralarvae, and adults. Their enzymatic activities were determined, and antibacterial properties were assessed against common marine pathogens. The isolates belonged to the phyla Proteobacteria, Actinomycetota, Bacteroidota, and Bacillota, represented by 21 genera and 27 species. Specific taxa were associated with each developmental stage, with only three species shared among different stages: Bacillus pumilus, B. megaterium, and Shewanella algae, which also inhibited the growth of all assayed pathogens. Organic extracts from Bacillus megaterium M8-1 were obtained, and UHPLC-MS analysis detected seventeen putative compounds, including two phenolic acids, three indole derivatives, and twelve oxylipins. Our findings provide novel data on cultivable bacterial representatives isolated from Octopus mimus capable of synthesizing chemical compounds with bioactive properties. These results contribute to a better understanding of the role of microbial communities in the survival of this invertebrate species during critical early life stages.

Oceanic Breakthroughs: Marine-Derived Innovations in Vaccination, Therapy, and Immune Health

The vast, untapped potential of the world's oceans is revealing groundbreaking advancements in human health and vaccination. Microalgae such as Nannochloropsis spp. and Dunaliella salina are emerging as resources for recombinant vaccine development with specific and heterologous genetic tools used to boost production of functional recombinant antigens in Dunaliella salina and Nannochloropsis spp. to induce immunoprotection. In humans, several antigens produced in microalgae have shown potential in combating diseases caused by the human papillomavirus, human immunodeficiency virus, hepatitis B virus, influenza virus, Zika virus, Zaire Ebola virus, Plasmodium falciparum, and Staphylococcus aureus. For animals, microalgae-derived vaccine prototypes have been developed to fight against the foot-and-mouth disease virus, classical swine fever virus, vibriosis, white spot syndrome virus, and Histophilus somni. Marine organisms offer unique advantages, including the ability to express complex antigens and sustainable production. Additionally, the oceans provide an array of bioactive compounds that serve as therapeutics, potent adjuvants, delivery systems, and immunomodulatory agents. These innovations from the sea not only enhance vaccine efficacy but also contribute to broader immunological and general health. This review explores the transformative role of marine-derived substances in modern medicine, emphasizing their importance in the ongoing battle against infectious diseases.

Diversity and Activity of Bacteria Cultured from a Cup-The Sponge Calyx nicaeensis

Marine sponges are well-known for hosting rich microbial communities. Sponges are the most prolific source of marine bioactive compounds, which are frequently synthesized by their associated microbiota. Calyx nicaeensis is an endemic Mediterranean sponge with scarce information regarding its (bioactive) secondary metabolites. East Mediterranean specimens of mesophotic C. nicaeensis have never been studied. Moreover, no research has inspected its associated bacteria. Thus, we studied the sponge's bacterial diversity and examined bacterial interspecific interactions in search of a promising antibacterial candidate. Such novel antimicrobial agents are needed since extensive antibiotic use leads to bacterial drug resistance. Bacteria cultivation yielded 90 operational taxonomic units (OTUs). A competition assay enabled the testing of interspecific interactions between the cultured OTUs. The highest-ranked antagonistic bacterium, identified as Paenisporosarcina indica (previously never found in marine or cold habitats), was mass cultured, extracted, and separated using size exclusion and reversed-phase chromatographic methods, guided by antibacterial activity. A pure compound was isolated and identified as 3-oxy-anteiso-C15-fatty acid-lichenysin. Five additional active compounds await final cleaning; however, they are lichenysins and surfactins. These are the first antibacterial compounds identified from either the C. nicaeensis sponge or P. indica bacterium. It also revealed that the genus Bacillus is not an exclusive producer of lichenysin and surfactin.

Increasing outer membrane complexity: the case of the lipopolysaccharide lipid A from marine Cellulophaga pacifica

Gram-negative bacteria living in marine waters have evolved peculiar adaptation strategies to deal with the numerous stress conditions that characterize aquatic environments. Among the multiple mechanisms for efficient adaptation, these bacteria typically exhibit chemical modifications in the structure of the lipopolysaccharide (LPS), which is a fundamental component of their outer membrane. In particular, the glycolipid anchor to the membrane of marine bacteria LPSs, i.e. the lipid A, frequently shows unusual chemical structures, which are reflected in equally singular immunological properties with potential applications as immune adjuvants or anti-sepsis drugs. In this work, we determined the chemical structure of the lipid A from Cellulophaga pacifica KMM 3664T isolated from the Sea of Japan. This bacterium showed to produce a heterogeneous mixture of lipid A molecules that mainly display five acyl chains and carry a single phosphate and a D-mannose disaccharide on the glucosamine backbone. Furthermore, we proved that C. pacifica KMM 3664T LPS acts as a weaker activator of Toll-like receptor 4 (TLR4) compared to the prototypical enterobacterial Salmonella typhimurium LPS. Our results are relevant to the future development of novel vaccine adjuvants and immunomodulators inspired by marine LPS chemistry.

A Novel Inhibitor against the Biofilms of Non-Tuberculous Mycobacteria

Non-tuberculous Mycobacteria (NTM), previously classified as environmental microbes, have emerged as opportunistic pathogens causing pulmonary infections in immunocompromised hosts. The formation of the biofilm empowers NTM pathogens to escape from the immune response and antibiotic action, leading to treatment failures. NF1001 is a novel thiopeptide antibiotic first-in-class compound with potent activity against planktonic/replicating and biofilm forms of various NTM species. It is potent against both drug-sensitive and -resistant NTM. It has demonstrated a concentration-dependent killing of replicating and intracellularly growing NTM, and has inhibited and reduced the viability of NTM in biofilms. Combination studies using standard-of-care (SoC) drugs for NTM exhibited synergetic/additive effects, but no antagonism against both planktonic and biofilm populations of Mycobacterium abscessus and Mycobacterium avium. In summary, the activity of NF1001 alone or in combination with SoC drugs projects NF1001 as a promising candidate for the treatment of difficult-to-treat NTM pulmonary diseases (NTM-PD) and cystic fibrosis (CF) in patients.