Anti Inflammatory, Antinociceptive and Central Nervous System Depressant Activities of Marine Bacterial Extracts
Marine microbes associated with macroalgae produce diverse secondary metabolites that include alkaloids, polypeptides, polyketides, etc. Some novel bioactive compounds of epiphytic origin exhibit anti-inflammatory activity against reactive oxygen species and other mediators that induce the inflammatory process in tissues. Their ability to suppress inflammatory factors indicates that they can inhibit oxidative damage and nociceptive sensitivity in vivo.
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The study examined the pharmacological properties – anti-inflammatory, antinociceptive, and CNS depressant – of epiphytic bacteria associated with seaweeds and other marine organisms. The study involved the inoculation of ectosymbionts and endosymbionts isolated from three seaweeds (C. limonoids, U. Lactuca, and E. compressa) growing on the Tuticorin coast, India, in seawater broth to grow bacterial cultures.
Epiphytic bacteria associated with ascidians were also isolated. Crude extracts from the bacterial cultures were used in the pharmacological assays. The anti-inflammatory activity of the extracts was tested using model animals (rats) with edematous paws. The antinociceptive activity analysis involved comparing the reaction time of mice treated with the extracts and the controls. The CNS depressant activity test entailed measurement of locomotor activity of mice injected with diazepam and the extract. From the results of the anti-inflammatory test, extracts from seaweed (C. compressed) associated bacterial strains (EM13 and EM14) exhibited significant anti-inflammatory activity.
The inhibitory effect was 20.4-59.5% at 200 mg/Kg dosage. The isolates significantly minimized paw edema through the bioactive compounds that mimic anti-inflammatory mediators and antioxidants. The bacterial extracts also lowered the locomotor activity and CNS depressant state in the mice. Strains EM13 and EM14 showed pharmacological potential as anti-oxidants for protecting tissues from factors that induce inflammation. The authors conclude that the isolation and characterization of the bioactive principles from the potent strains could yield pharmacological agents with antioxidant potential.
Presence of Quorum-sensing Inhibitor-like Compounds from Bacteria Isolated from the Brown Alga Colpomenia sinuosa
Marine bacterial quorum sensing (QS) antagonists are seen as potential pharmacological compounds with antioxidant activity. QS is a bacterial signaling mechanism that is mediated by autoinducers such as N-acyl homoserine lactone (AHL). Preexisting epiphytic bacteria produce QS antagonists that inhibit surface colonization by other competing strains through the disruption of QS signaling. The QS inhibitory effect of these molecules is attributed to the reduction of the signal mediators produced by epiphytes.
The study sought to screen for potent QS inhibitors produced by epiphytic bacteria using a protocol that was applied in isolating inhibitory pigments from indicator bacteria. In this study, the researchers inoculated agar plates with isolates of epibiotic bacteria attached to the surface of brown algae (C. sinuosa) growing on a Japanese Island. Selection based on colony morphology obtained 96 strains, which were cultured on agar plates.
The indicator bacterial sp. – Serratia rubidaea – was also isolated and cultured. The screening for QS inhibition involved inoculating agar plates containing the isolates with the S. rubidaea and incubating them for 48 hours. Molecular characterization of strains producing QS antagonists involved 16S rRNA analysis and BLAST searches. From the results, 12% of the epibiotic isolates secreted bioactive compounds that mimic QS inhibitors.
Their inhibitory effect was indicated by a lack of pigmentation due to S. rubidaea growth inhibition. 16S rRNA identification revealed that the potent isolates were Bacillaceae and Proteobacteria. QS inhibitors inactivate QS-regulated products that cause oxidative stress on epibiotic symbionts. They hydrolyze the AHLs produced by other bacterial strains, inhibiting their settlement on algal surfaces. The reduction of signal products indicates that QS antagonists from C. sinuosa associated bacteria have pharmacological potential as natural antioxidants.
Isolation of Seaweed-associated Bacteria and their Morphogenesis-inducing Capability in Axenic Cultures of the Green Alga
Seaweed-associated bacteria produce bioactive molecules that are regulators of algal morphogenesis and development. These bacterial symbionts, in turn, benefit from the organic nutrients secreted by the host through the bacterial-seaweed interaction. Cellular antioxidants are required for cell proliferation in eukaryotes. They create a reducing cellular environment that is ideal for the morphogenesis of green algae, e.g., Ulva fasciata.
The study entailed the screening for the morphogenesis-stimulating activity of bacteria associated with cultured Ulva spp. and Gracilaria spp. It also examined the strain’s subsequent reproduction-inducing ability on U. fasciata and characterized them based on 16S rRNA. In this study, 53 isolates from three algal species belonging to two genera (Ulva and Gracilaria) native to Veraval, India, were grown on algal plates to obtain pure colonies.
The next step involved the inoculation of the bacterial isolates on axenic algal cultures developed from U. fasciata zoospores to test their effect on morphogenesis. Five isolates that induced algal morphogenesis were inoculated on algal stock culture to determine their zoospore inducing activity. DNA samples isolated from the colonies were PCR amplified for 16S rRNA-based characterization. The study isolated five epiphytes that showed significant morphogenesis inducing activity on U. fasciata thallus cultures, including spine development. Further, two isolates associated with Glacilaria spp and exhibited a significant zoospore induction when inoculated on U. fasciata (107,700 spores per gram of thallus).
Based on16S rRNA sequence homology, one of the five strains belonged to Marinomonas spp., while the rest were Bacillus spp. The morphogenesis-stimulating activity of these isolates on U. fasciata indicates that epiphytes play a role in the growth and development of green algae. They work by secreting antioxidants that provide a reducing cellular environment that is required for algal differentiation.
Epiphytes Modulate Posidonia oceanica Photosynthetic Production, Energetic Balance, Antioxidant Mechanisms, and Oxidative Damage
Epiphytes prevent light from reaching algal surfaces, leading to free radical (ROS) accumulation that causes oxidative stress. Light attenuation due to a high concentration of bacterial communities activates the algal antioxidant system for protection against oxidative damage. The ROS accumulation in seagrasses is seen as a protective mechanism against bacterial epiphytes. Some bacterial strains synthesize antioxidants, including phenolic compounds, which enable them to colonize algal surfaces.
The study compared the modulation effect of epiphytic bacteria on photosynthesis and oxidative stress responses in a seagrass species (P. oceanica) with controls. P. oceanica samples colonized by epiphytic bacteria and those without heavy epiphyte load from Isleta del Moro were obtained. The epiphytes were washed off from the leaves, and in situ photosynthetic rate measured. The authors also measured photosynthetic pigments, antioxidant enzyme activity, and antioxidant compound quantity (phenolic compounds) in the leaf samples.
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The results indicated that the epibiotic communities did not affect the net photosynthetic production in the shoots. However, chlorophyll b levels were lower in colonized shoots than in leaves without epiphytic bacteria. The antioxidant content was elevated in epiphyte-associated leaves, especially at noon. However, the level of antioxidants and phenolic compounds was lower between dawn and noon in all samples. The epiphytic bacteria were associated with elevated peroxidation of membranes before dawn.
The results show that epiphytes modulate oxidative stress in seagrasses due to the shading effect on leaf surfaces. Under the conditions of light limitation and photoinhibition, ROS accumulates in P. oceanica. To prevent oxidative stress, the macroalgae and epiphytic bacteria synthesize antioxidants, such as phenolic compounds, to neutralize the effects of oxidative damage. For epiphytic bacteria, a higher antioxidant capacity is required to colonize algae surfaces.
Costa, M. M., Barrote, I., Silva, J., Olive, I., Alexandre, A., Albano, S., & Santos, R. (2015). Epiphytes modulate Posidonia oceanica photosynthetic production, energetic balance, antioxidant mechanisms, and oxidative damage. Frontiers in Marine Science, 2, 1-10. Web.
Kanagasabhapathy, M., Yamazaki, G., Ishida, A., Sasaki, H., & Nagata, S. (2009). Presence of quorum-sensing inhibitor-like compounds from bacteria isolated from the brown alga Colpomenia sinuosa. Letters in Applied Microbiology, 49, 573–579. Web.
Ramasamy, M. S., & Kumar, S. S. (2009). Anti inflammatory, antinociceptive and central nervous system depressant activities of marine bacterial extracts. Journal of Pharmacology and Toxicology, 4(4), 152-159. Web.
Singh, R. P., Mantri, V. A., Reddy, C. R. K., & Jha, B. (2011). Isolation of seaweed-associated bacteria and their morphogenesis-inducing capability in axenic cultures of the green alga. Aquatic Biology, 12, 13-21. Web.