Comparison of antibacterial activity in the hemolymph of marine bivalves from Galicia (NW Spain)

Potential threats of microplastics and pathogenic bacteria to the immune system of the mussels Mytilus galloprovincialis

As one of the main components of marine pollution, microplastics (MPs) inevitably enter the mussel aquaculture environment. At the same time, pathogenic bacteria, especially pathogens such as Vibrio, can cause illness outbreaks, leading to large-scale death of mussels. The potential harm of MPs and pathogenic bacteria to bivalve remains unclear. This study designed two experiments (1) mussels (Mytilus galloprovincialis) were exposed to 100 particles/L or 1,000 particles/L polymethyl methacrylate (PMMA, 17.01 ± 6.74 μm) MPs and 1 × 107 CFU/mL Vibrio parahaemolyticus at the same time (14 days), and (2) mussels were exposed to 100 particles/L or 1,000 particles/L MPs for a long time (30 days) and then exposed to 1 × 107 CFU/mL V. parahaemolyticus to explore the effects of these two stresses on the mussel immune system. The results showed that after the combined exposure of V. parahaemolyticus and MPs, the lysosomal membrane stability of hemocytes decreased, lysozyme activity was inhibited, and hemocytes were induced to produce more lectins and defensins to fight pathogenic invasion. Long-term exposure to MPs caused a large amount of energy consumption in mussels, inhibited most of the functions of humoral immunity, increased the risk of mussel infection with pathogenic bacteria, and negatively affected mussel condition factor, the number of hemocytes, and the number of byssuses. Mussels may allocate more energy to deal with MPs and pathogenic bacterial infections rather than for growth. Above all, MPs exposure can affect mussel immune function or reduce its stress resistance, which in turn has an impact on mollusk farming.

Marine glycoproteins: a mine of their structures, functions and potential applications

Many bioactive compounds are reported from marine organisms, which are significantly different from those found in terrestrial organisms regarding their chemical structures and pharmacological activities. Marine glycoproteins (MGs) have aroused increasing attention as a good nutrient source owing to their potential applications in medicine, cosmetics and food. However, there is a lack of a comprehensive study on MGs to help readers understand the current state of research on marine-derived glycoproteins. The current review compiles the recent progress made on the structures and functions of MGs with future perspectives to maximize their value and applications via bibliometric analysis methods for the first time. The current research on MGs appears mostly limited to the laboratory, with no large-scale production of marine glycoproteins developed. The sugar chains are bound to proteins through covalent bonds that can readily be cleaved leading to difficultly in their separation and purification. Health effects attributed to MGs include treatment of inflammatory diseases, as well as anti-oxidant, immune modulation, anti-tumor, hypolipidemic, hypoglycemic, anti-bacterial and anti-freeze activities. This review can not only deepen the understanding of the functions of MGs, but also lay an important foundation for the further development and utilization of marine resources.

First report of steroid derivatives isolated from starfish Acanthaster planci with anti-bacterial, anti-cancer and anti-diabetic activities

Chemical studies on Acanthaster planci have afforded two steroids, 5α-cholesta-24-en-3β,20β-diol-23-one (1) and 5α-cholesta-9(11)-en-3β, 20β-diol (2). Structures compounds 1 and 2 were determined with the help of spectroscopic studies. Compound 1 showed strong antibacterial activity (21.0 ± 0.06 mm) against P. aeruginosa. Compounds 1 and 2 were also active against human breast carcinoma cells (MCF-7) with LC₅₀ values of 49 ± 1.6 and 57.5 ± 1.5 μg/ml, respectively. This bioactivity was comparable to the currently used anticancer agent, cisplatin (LC₅₀ 46 ± 1.1 µg/ml). Compounds 1 and 2 exhibited anti-α-glucosidase activity with IC₅₀ values of 58 ± 0.8 and 55 ± 0.5 µg/ml, respectively, whereas IC₅₀ of Acarbose as a positive control was found to be 36 ± 0.4 µg/ml in our bioassay.

Antimicrobial Properties of Actively Purified Secondary Metabolites Isolated from Different Marine Organisms

BACKGROUND

The treatment of infection caused by pathogenic bacteria becomes one of the serious concerns globally. The failure in the treatment was found due to the exhibition of multiple resistance mechanisms against the antimicrobial agents. The emergence of resistant bacterial species has also been observed due to prolong treatment using conventional antibiotics. To combat these problems, several alternative strategies have been employed using biological and chemically synthesized compounds as antibacterial agents. Marine organisms are considered as one of the potential sources for the isolation of bioactive compounds due to the easily available, cost-effective, and eco-friendly.

METHODS

The online search methodology was adapted for the collection of information related to the antimicrobial properties of marine-derived compounds. These compound has been isolated and purified by different purification techniques, and their structure also characterized. Furthermore, the antibacterial activities have been reported by using broth microdilution as well as disc diffusion assays.

RESULTS

The present review paper describes the antimicrobial effect of diverse secondary metabolites which are isolated and purified from the different marine organisms. The structural elucidation of each secondary metabolite has also been done in the present paper, which will help for the in silico designing of the novel and potent antimicrobial compounds.

CONCLUSION

A thorough literature search has been made and summarizes the list of antimicrobial compounds that are isolated from both prokaryotic and eukaryotic marine organisms. The information obtained from the present paper will be helpful for the application of marine compounds as antimicrobial agents against different antibiotic-resistant human pathogenic bacteria.

Inability of non-proteolytic Clostridium botulinum to grow in mussels inoculated via immersion and packaged in high oxygen atmospheres

A series of botulism challenge studies were conducted to determine if botulinum toxin would be produced in mussels (Mytilus edulis) inoculated with non-proteolytic Clostridium botulinum spores and held under modified atmosphere (MA) packaging conditions at normal (4 °C) and abusive (12 °C) temperatures. Spore mixtures of six strains of non-proteolytic C. botulinum were introduced into live mussels through immersion in a seawater solution with cultured algae. Mussels were packed in a commercial high-oxygen (60-65% O2) MA-package with a buffer, and also packed under a vacuum. Feeding live mussels cultured algae (10(4) cells/ml) with a C. botulinum spore suspension (10(3) spores/ml) in seawater at 4 °C for 6 h resulted in the uptake of spores into mussel tissue (500/g) and the mussel GI tract (100/g). Under all of the experimental conditions evaluated, none of the fresh mussels became toxic, even after spoilage and in the absence of oxygen. However, control samples using tuna or cooked mussel meats became toxic in the absence of oxygen. Botulinum toxin was not produced in fresh mussels packaged under the MA-packaging conditions evaluated, even at an abusive storage temperature (12 °C) for at least 12 days or at normal storage temperate (4 °C) for at least 21 days, which is beyond their shelf life.

Bioactive compounds from marine mussels and their effects on human health

The consumption of marine mussels as popular seafood has increased steadily over the past decades. Awareness of mussel derived molecules, that promote health, has contributed to extensive research efforts in that field. This review highlights the bioactive potential of mussel components from species of the genus Mytilus (e.g. M. edulis) and Perna (e.g. P. canaliculus). In particular, the bioactivity related to three major chemical classes of mussel primary metabolites, i.e. proteins, lipids, and carbohydrates, is evaluated. Within the group of proteins the focus is mainly on mussel peptides e.g. those obtained by bio-transformation processes, such as fermentation. In addition, mussel lipids, comprising polyunsaturated fatty acids (PUFAs), are discussed as compounds that are well known for prevention and treatment of rheumatoid arthritis (RA). Within the third group of carbohydrates, mussel polysaccharides are investigated. Furthermore, the importance of monitoring the mussel as food material in respect to contaminations with natural toxins produced by microalgae is discussed.

Botulism challenge studies of a modified atmosphere package for fresh mussels: inoculated pack studies

A series of botulism challenge studies were performed to determine the possibility of production of botulinum toxin in mussels (Mytilus edulis) held under a commercial high-oxygen (60 to 65% O(2)), modified atmosphere packaging (MAP) condition. Spore mixtures of six strains of nonproteolytic Clostridium botulinum were introduced into mussel MAP packages receiving different packaging buffers with or without the addition of lactic acid bacteria. Dye studies and package flipping trials were conducted to ensure internalization of spores by packed mussels. Inoculated mussel packages were stored at normal (4°C) and abusive (12°C) temperatures for 21 and 13 days, respectively, which were beyond the packaged mussels' intended shelf life. Microbiological and chemical analyses were conducted at predetermined intervals (a total of five sampling times at each temperature), including total aerobic plate counts, C. botulinum counts, lactic acid bacterial counts, package headspace gas composition, pH of packaging buffer and mussel meat, and botulinum toxin assays of packaging buffer and mussel meat. Results revealed that C. botulinum inoculated in fresh mussels packed under MAP packaging did not produce toxin, even at an abusive storage temperature and when held beyond their shelf life. No evidence was found that packaging buffers or gas composition influenced the lack of botulinum toxin production in packed mussels.