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Identification of Asparagopsis armata-associated bacteria and characterization of their bioactive potential.

ABSTRACT: Macroalgae-associated bacteria have already proved to be an interesting source of compounds with therapeutic potential. Accordingly, the main aim of this study was to characterize Asparagopsis armata-associated bacteria community and evaluate their capacity to produce substances with antitumor and antimicrobial potential. Bacteria were selected according to their phenotype and isolated by the streak plate technique. The identification was carried out by the RNA ribosomal 16s gene amplification through PCR techniques. The antimicrobial activities were evaluated against seven microorganisms (Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Salmonella enteritidis, Staphylococcus aureus, Saccharomyces cerevisiae, Candida albicans) by following their growth through spectrophotometric readings. Antitumor activities were evaluated in vitro on human cell lines derived from hepatocellular (HepG-2) and breast carcinoma (MCF-7) using the MTT method. The present work identified a total of 21 bacteria belonging to the genus Vibrio, Staphylococcus, Shewanella, Alteromonadaceae, Bacillus, Cobetia, and Photobacterium, with Vibrio being the most abundant (42.86%). The extract of Shewanella sp. ASP 26 bacterial strain induced the highest antimicrobial activity, namely against Bacillus subtilis and Staphylococcus aureus with an IC₅₀ of 151.1 and 346.8 μg/mL, respectively. These bacteria (Shewanella sp.) were also the ones with highest antitumor potential, demonstrating antiproliferative activity on HepG-2 cells. Asparagopsis armata-associated bacteria revealed to be a potential source of compounds with antitumor and antibacterial activity.

SUBMITTER: Horta A

PROVIDER: S-EPMC6854849 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundAntibiotic resistance in bacteria spreads quickly, overtaking the pace at which new compounds are discovered and this emphasizes the immediate need to discover new compounds for control of infectious diseases. Terrestrial bacteria have for decades been investigated as a source of bioactive compounds leading to successful applications in pharmaceutical and biotech industries. Marine bacteria have so far not been exploited to the same extent; however, they are believed to harbor a multitude of novel bioactive chemistry. To explore this potential, genomes of 21 marine Alpha- and Gammaproteobacteria collected during the Galathea 3 expedition were sequenced and mined for natural product encoding gene clusters.ResultsIndependently of genome size, bacteria of all tested genera carried a large number of clusters encoding different potential bioactivities, especially within the Vibrionaceae and Pseudoalteromonadaceae families. A very high potential was identified in pigmented pseudoalteromonads with up to 20 clusters in a single strain, mostly NRPSs and NRPS-PKS hybrids. Furthermore, regulatory elements in bioactivity-related pathways including chitin metabolism, quorum sensing and iron scavenging systems were investigated both in silico and in vitro. Genes with siderophore function were identified in 50% of the strains, however, all but one harboured the ferric-uptake-regulator gene. Genes encoding the syntethase of acylated homoserine lactones were found in Roseobacter-clade bacteria, but not in the Vibrionaceae strains and only in one Pseudoalteromonas strains. The understanding and manipulation of these elements can help in the discovery and production of new compounds never identified under regular laboratory cultivation conditions. High chitinolytic potential was demonstrated and verified for Vibrio and Pseudoalteromonas species that commonly live in close association with eukaryotic organisms in the environment. Chitin regulation by the ChiS histidine-kinase seems to be a general trait of the Vibrionaceae family, however it is absent in the Pseudomonadaceae. Hence, the degree to which chitin influences secondary metabolism in marine bacteria is not known.ConclusionsUtilizing the rapidly developing sequencing technologies and software tools in combination with phenotypic in vitro assays, we demonstrated the high bioactive potential of marine bacteria in an efficient, straightforward manner - an approach that will facilitate natural product discovery in the future.

Project description:Crocodiles thrive in unsanitary conditions, feed on rotten meat, are exposed to heavy metals and are among the very few species to endure the catastrophic Cretaceous-Tertiary extinction event, and yet they can live up to 100 years. We hypothesized that crocodiles have developed mechanisms to achieve such longevity while surviving under stressful conditions. We speculate that their microbial gut flora may produce substances contributing to their “hardiness” and “longevity”. Previously we characterized selected microbial gut bacteria colonizing the gastrointestinal tract of Crocodylus porosus (CP) using 16S rDNA sequencing. Next, bacterial conditioned media containing gut microbial metabolites were prepared. Bioassay-guided testing of selected bacterial conditioned media using LC-TIMS-QTOF MS, revealed the identity of gut microbial metabolites. Among two bacterial conditioned media, i.e., CP27 and 36, the analyses resulted in 141 highly confidently (MS/MS) identified metabolites in both samples. The pairwise comparison of the two samples indicated that 109 metabolites change significantly between them (p <0.05). Among abundant metabolites more prevalent in CP36 there were 2-Methyl-4-nitroimidazole, N-Acetyl-L-tyrosine, Acetaminophen, Trans-Ferulic acid, N, N-Dimethylformamide, Pyrocatechol, Cyclohexanone, 3, 4-Dihydrozphenylglycol, Diphenhydramine, Melatonin, Gamma –terpinene. Whereas in CP27 samples the most abundant metabolites were Carbamazepin, deoxyninosine, Cysteamine, Benzylnicotinate, 3-phenoxypropionic acid, Indole-3-carbinol, Benzaldehyde, Benzocaine, 2-Aminobenzoic acid, 3-Methylindole. Functional enrichment analysis of all identified metabolites with metabolite sets based on drug pathways showed that they were enriched for drug action of top ten pathways associating with enalapril metabolism pathway, diphenhydramine H1-Antihistamine action, enalarpil action pathway, benzocaine action pathway, mepivacaine action pathway, oxybuprocaine action pathways, nifedipine action pathway, propranolol action pathway, acetaminophen metabolism pathway, carbamazepine metabolism pathway. These findings suggest that analyses of crocodile gut bacteria may reveal potential drug leads, intensive future research is needed to realize these expectations.

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Identification of Asparagopsis armata-associated bacteria and characterization of their bioactive potential.

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