Isolation, Phylogenetic Analysis of the Microbial Community Associated with the Red Sea Sponge Ircinia Echinata and Biological Evaluation of their Secondary Metabolites

Mohamed A Shreadah*¹, Nihad M Abdel Monem², Galila A Yakout² and Haiam M Aboul Ela¹

Received: December 02, 2018;   Published: December 17, 2018

DOI: 10.26717/BJSTR.2018.12.002218

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Abstract

The present study was undertaken to provide information about bioactive compounds of the microbial community associated with Ircinia echinata marine sponge collected from the Red Sea. This work investigated the antioxidant and cytotoxicity properties of the tested extracted crude extract. Sponge was taxonomically identified as Ircinia echinata. Moreover, taxonomic and phylogenetic analyses of the bacteria on the basis of 16S rRNA gene sequences showed that dominant phylum was proteobacteria. The results of HPLC analysis revealed that the bacterial crude extracts exhibited highly significant quantities of total phenolic contents in crude extracts of the two tested bacterial isolates. The highest level of total phenolic contents was measured in the extract was shown in extracts HA-MS-41 (3.238±0.03 mg gallic equivalent/ml). Whereas, the lowest value was shown in extract HA-MS-118 (2.946±0.10 mg gallic equivalent/ml).

The results of the current study cleared out that extract HA-MS-41[JX484800] contained gallic and tannic acids (1.084 and 1.413 mg/ml), whereas extract HA-MS-118 [JX484801] contained gallic (1.005 mg/ml) but didn’t contain tannic acid. The highest level of total flavonoid content was measured in the extract HA-MS-41 extract (5±0.23 mg catechin equivalent / ml). Whereas, much lower value was shown in the HA-MS-118 extract (2.5±0.26 mg catechin equivalent / ml). Carotenoid compounds significantly varied among the two bacterial extracts; the highest total carotenoid concentration was observed in the extract HA-MS-41 (1.165μg/ml). Whereas, lower valuesobserved in the extract HA-MS-118 (0.185 μg/ml). In the meantime, GC/MS profiling for the ethyl acetate extract of the studied sponge-associated bacteria revealed the presence of various phytochemical compounds having different biological activities. Results of FTIR spectroscopic studies have revealed the presence of various chemical constituents in ethyl acetate extract of the HA-MS-41 and HA-MS-118 bacterial isolates.

The results of the elemental analysis indicated that the bacterial extracts contained major elements like Na, Mg, Al, Si, S, K, Ca, P and Cl, besides the major elemental constituents in all living organisms; C, N and O. The results showed considerable concentrations of many halides (Fe, Cu, Zn and Br). DPPH scavenging activity in terms of IC50 values was shown to be high in case of the extract HA-MS-41 (1.045 mg/ml) and in case of the extract HA-MS-118 (1. 450 mg/ml). IC50 values of the antioxidant activity of bacterial extracts using NO assay for the tested two extracts were 5.98 and 6.222 %. Moreover, potent antioxidant activity using ABTS+ assay with percentages inhibition of IC50 = 3.404 and 1.64 mg/ml for HA-MS-41and HA-MS-118, respectively. In the present study highly significant total antioxidant capacity values was also obtained by using phosphomolybdenum assay in the bacterial extract suggesting the presence of effective antioxidants in the bacterial extract.

The high potency of these isolates is mainly attributed to the presence of various classes of potentially active secondary metabolites detected in them. Indeed phenols, tannins, and alkaloids identified in the tested extracts have been reported to possess antioxidant and anticancer activities. The relative wide range of these biologically properties may results from the individual or from the combined modes of action of compounds belonging to the identified groups of constituents. The cytotoxicity screening studies revealed that the maximum cell growth inhibitory effects of bacterial crude extracts against the tested cancer cell lines; HepG2; HCT and MCF-7 were found to be 22.7, 14.6, and 12.2 μg/ml, respectively for HA-MS-41, and 36.5, 23.6, and 11.9 μg/ml, respectively for HA-MS-118. These results were confirmed by a protein kinase inhibition specialized screening revealing an inhibition activity of 87.93±0.51and 94.24±1.15 % for HA-Ms-41and HA-Ms-118.

Keywords :Sponge Associated Bacteria; Phylogenetic Analysis; Bioactive Metabolites

Abbreviations : NIWA: National Institute of Water and Atmospheric Research; PCR: Polymerase Chain Reaction; SEM: Electron Microscope; EDX: X-ray Spectrophotometer, DPPH: Diphenyl–α-picrylhydrazyl, RP: Reversed-Phase, BHT: Butylated Hydroxytoluene; BHA: Butylated Hydroxyanisole; TAO: Total Antioxidant Capacity; HepG2: Hepatocellular Carcinoma