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Antifouling activity of bacterial extracts associated with soft coral and macroalgae from the Red Sea

Tunkal Rabab Ibrahim, Jamal Mamdoh T., Abdulrahman Idris, Pugazhendi Arulazhagan, Satheesh Sathianeson

Oceanological and Hydrobiological Studies

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2022

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Vol. 51, No. 4

325--336

EN

In marine environments where biofouling occurs and has an impact on the maritime economy and environment, compounds that inhibit the attachment, growth and survival of microorganisms in a biofilm complex as well as settlement of larvae are considered potential antifouling compounds. In this study, the extracellular metabolites from two surface- associated bacteria isolated from soft coral and macroalga were evaluated for antibiofilm and antisettlement activity. The bacteria were identified using 16S rRNA gene sequencing, and the culture supernatant extract of each strain was evaluated for antibiofilm activity. The compounds present in the extracts were analysed using GC-MS. The two bacterial strains were identified as Bacillus licheniformis MBR1 and Vibrio alginolyticus MBR4 for the isolates from soft coral and macroalgae, respectively. The extracts inhibited the growth of biofilm-forming bacteria, biofilm formation and barnacle larval settlement. The GC-MS analysis of the extract detected the presence of compounds such as tetrapentacontane, octadecanoic acid, 2,3-dihydroxypropyl ester, hexadecanoic acid, 2-hydroxy-1-(hydroxymethyl) ethyl ester and 17-pentatriacontene. The results of the study show that extracellular metabolites of the bacteria associated with marine organisms could be used as natural antifouling compounds to control biofouling.

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LC-MS/MS profiling, antibiofilm, antimicrobial and bacterial growth kinetic studies of Pluchea dioscoridis extracts

El-Shazly Maha A.M., Hamed Ahmed A., Kabary Hoda A., Ghareeb Mosad A.

Acta Chromatographica

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2022

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Vol. 34, no. 3

338--350

EN

The therapeutical applications of ornamental plants have been categorized to be of a great effectiveness in multiple industries from ancient times until present days. Pluchea dioscoridis is widely known Egyptian wooden plant that has been extensively applied for different medicinal purposes. In this study, LC-ESI-MS/MS analysis of the potent antimicrobial ethyl acetate and n-butanol extracts of P. dioscoridis leaves led to identification of 28 and 21 compounds, respectively. The identified compounds were categorized as phenolic acids, phenolic acids derivatives, organic acids, flavonoids (aglycones and glycosides), secoiridoids, coumarin derivatives, and gallotannins derivatives. Among them, caffeic acid 3-sulfate was the most predominate in the investigated extracts followed by ferulic acid and dicaffeoyl-quinic acid. Also, the antimicrobial potentiality of different extracts was evaluated against different pathogenic microbes including Enterobacter cloacae, Micrococcus leutus, Aeromonas hydrophila, Bacillus subtilis, Bacillus cereus, Bacillus lichneformis and Clostridium species. Furthermore, different concentrations of the most potent extract were assayed for antibacterial efficacy on growth curve kinetics against the susceptible bacteria along 4days incubation period. Our gathered data confirmed that, the antimicrobial activity against tested bacteria was different according to the solvent used in the extraction process. Mostly, all the extracts showed a wide spectrum antibacterial activity except the plant water extract which shows a mild activity against Clostridium sp. only. Based on the highest inhibition zone diameter, the ethyl acetate extract followed by butanol extract exhibited the highest inhibition zone with Micrococcus luteus and B. subtilis (20.0 and 18.5 mm) respectively. Determining the effect of ethyl acetate extract at different concentration (0, 0.66, 1.66, 3.33, 6.67, 13.34 and 20.01 mg mL⁻¹) on M. luteus growth kinetics, the data assured that the antibacterial activity shows concentration dependent manner with the highest antibacterial activity at 20.01 mg mL⁻¹ culture. The data also confirmed that, none of the selected concentration showed bactericidal activity in the prepared cultures, and with the prolonged incubation period the bacteria acquire resistance against the extract beginning from second or third day of incubation.

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Effects of copper and cadmium on physiology and antifouling defense of the marine macroalga Ulva reticulata

Al-Khaldi Wejdan Ahmed, Al Solami Lafi, Satheesh Sathianeson

Oceanological and Hydrobiological Studies

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2021

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Vol. 50, No. 2

184--197

EN

Heavy metals are major stressors for benthic macroalgal communities in marine ecosystems. In this study, the effects of copper and cadmium on some physiological parameters along with antifouling defense of the marine macroalga Ulva reticulata were assessed under laboratory conditions. Macroalgal samples were treated with three concentrations (1 mg l−1, 3 mg l−1 and 5 mg l−1) of copper and cadmium for 2 and 7 days. After treatment, algal samples were analyzed for chlorophyll-a, carotenoid, total polyphenol and total antioxidant capacity. Also, algal extracts were tested against biofilm-forming bacteria strains to understand differences in antifouling activity. The results indicated that exposure of U. reticulata to copper and cadmium, on the one hand, induced protective mechanisms such as total phenol production and antioxidant capacity against metal stress and, on the other hand, reduced photosynthesis. While the extract obtained from control algal samples showed a strong inhibitory effect on the growth of biofilm-forming bacteria, treatment with heavy metals resulted in reduced antibiofilm activity. In general, the results revealed that exposure of macroalgae to heavy metals can affect antifouling defense traits in addition to changes in photosynthetic pigment content.