Cytotoxic and apoptotic evaluations of marine bacteria isolated from brine-seawater interface of the Red Sea

A phenol amine molecule from Salinivenus iranica acts as the inhibitor of cancer stem cells in breast cancer cell lines

In recent years, the anticancer properties of metabolites from halophilic microorganisms have received a lot of attention. Twenty-nine halophilic bacterial strains were selected from a culture collection to test the effects of their supernatant metabolites on stem cell-like properties of six human cancer cell lines. Human fibroblasts were used as normal control. Sphere and colony formation assay were done to assess the stem cell-like properties. invasion and migration assay, and tumor development in mice model were done to assess the anti-tumorigenesis effect in vitro and in vivo. The metabolites from Salinivenus iranica demonstrated the most potent cytotoxic effect on breast cancer cell lines (IC50 = 100 µg/mL) among all strains, with no effect on normal cells. In MDA-MB-231 cells, the supernatant metabolites enhanced both early and late apoptosis (approximately 9.5% and 48.8%, respectively) and decreased the sphere and colony formation ability of breast cancer cells. Furthermore, after intratumor injection of metabolites, tumors developed in the mice models reduced dramatically, associated with increased pro-apoptotic caspase-3 expression. The purified cytotoxic molecule, a phenol amine with a molecular weight of 1961.73 Dalton (IC50 = 1 µg/mL), downregulated pluripotency gene SRY-Box Transcription Factor 2 (SOX-2) expression in breast cancer cells which is associated with resistance to conventional anticancer treatment. In conclusion, we suggested that the phenol amine molecule from Salinivenus iranica could be a potential anti-breast cancer component.

Shedding light on the composition of extreme microbial dark matter: alternative approaches for culturing extremophiles

More than 20,000 species of prokaryotes (less than 1% of the estimated number of Earth's microbial species) have been described thus far. However, the vast majority of microbes that inhabit extreme environments remain uncultured and this group is termed "microbial dark matter." Little is known regarding the ecological functions and biotechnological potential of these underexplored extremophiles, thus representing a vast untapped and uncharacterized biological resource. Advances in microbial cultivation approaches are key for a detailed and comprehensive characterization of the roles of these microbes in shaping the environment and, ultimately, for their biotechnological exploitation, such as for extremophile-derived bioproducts (extremozymes, secondary metabolites, CRISPR Cas systems, and pigments, among others), astrobiology, and space exploration. Additional efforts to enhance culturable diversity are required due to the challenges imposed by extreme culturing and plating conditions. In this review, we summarize methods and technologies used to recover the microbial diversity of extreme environments, while discussing the advantages and disadvantages associated with each of these approaches. Additionally, this review describes alternative culturing strategies to retrieve novel taxa with their unknown genes, metabolisms, and ecological roles, with the ultimate goal of increasing the yields of more efficient bio-based products. This review thus summarizes the strategies used to unveil the hidden diversity of the microbiome of extreme environments and discusses the directions for future studies of microbial dark matter and its potential applications in biotechnology and astrobiology.

Streptomyces sp. 1S1 isolated from Southern coast of the Red Sea as a renewable natural resource of several bioactive compounds

Red Sea represents one of the most remarkable marine ecosystems. However, it is also one of the world's least explored areas of marine biodiversity. The aims of this investigation were therefore, to isolate marine microorganisms from the seashore sediments and water in shallow region from west Yemen coast, to assess their antimicrobial potential, to identify the highly active isolate, and to purify and identify the bioactive compounds from it. In this regard, twenty-five bacterial strains have been isolated from twenty samples and tested for their antimicrobial ability against some pathogenic bacteria and yeast by using the agar disk diffusion and agar well diffusion assay. Out of the total 25 marine actinomycetes isolates only 13 exhibited interesting antimicrobial activity. The morphological, biochemical, and phylogenetic characteristics of the potential isolate 1S1 were compatible with their classification in the genus Streptomyces. The 16S rRNA gene sequences have shown that the isolate 1S1 clustered with Streptomyces longisporoflavus. The strain Streptomyces sp. 1S1 was cultivated and extracted with ethyl acetate. The GC–MS study of the extract indicated the presence of certain fatty acyl compounds e.g., tetradecanoic acid, 9-octadecenoic acid, hexadecanoic acid, and 9,12,15-octadecatrienoic acid. Using chromatographic techniques, three compounds were isolated and by spectroscopic methods e.g., IR, MS and NMR structurally elucidated. The three compounds were identified as a triacylglyceride, 9-octadecenoic acid, and hexadecanoic acid. The study reinforces the evidence of the potential of Streptomyces sp and the ability to produce several antimicrobial compounds.

Therapeutic applications and biological activities of bacterial bioactive extracts

Bacteria are rich in a wide variety of secondary metabolites, such as pigments, alkaloids, antibiotics, and others. These bioactive microbial products serve a great application in human and animal health. Their molecular diversity allows these natural products to possess several therapeutic attributes and biological functions. That's why the current natural drug industry focuses on uncovering all the possible ailments and diseases that could be combated by bacterial extracts and their secondary metabolites. In this paper, we review the major utilizations of bacterial natural products for the treatment of cancer, inflammatory diseases, allergies, autoimmune diseases, infections and other diseases that threaten public health. We also elaborate on the identified biological activities of bacterial secondary metabolites including antibacterial, antifungal, antiviral and antioxidant activities all of which are essential nowadays with the emergence of drug-resistant microbial pathogens. Throughout this review, we discuss the possible mechanisms of actions in which bacterial-derived biologically active molecular entities could possess healing properties to inspire the development of new therapeutic agents in academia and industry.

Deep Hypersaline Anoxic Basins as Untapped Reservoir of Polyextremophilic Prokaryotes of Biotechnological Interest

Deep-sea hypersaline anoxic basins (DHABs) are considered to be among the most extreme ecosystems on our planet, allowing only the life of polyextremophilic organisms. DHABs’ prokaryotes exhibit extraordinary metabolic capabilities, representing a hot topic for microbiologists and biotechnologists. These are a source of enzymes and new secondary metabolites with valuable applications in different biotechnological fields. Here, we review the current knowledge on prokaryotic diversity in DHABs, highlighting the biotechnological applications of identified taxa and isolated species. The discovery of new species and molecules from these ecosystems is expanding our understanding of life limits and is expected to have a strong impact on biotechnological applications.

Halophiles and Their Biomolecules: Recent Advances and Future Applications in Biomedicine

The organisms thriving under extreme conditions better than any other organism living on Earth, fascinate by their hostile growing parameters, physiological features, and their production of valuable bioactive metabolites. This is the case of microorganisms (bacteria, archaea, and fungi) that grow optimally at high salinities and are able to produce biomolecules of pharmaceutical interest for therapeutic applications. As along as the microbiota is being approached by massive sequencing, novel insights are revealing the environmental conditions on which the compounds are produced in the microbial community without more stress than sharing the same substratum with their peers, the salt. In this review are reported the molecules described and produced by halophilic microorganisms with a spectrum of action in vitro: antimicrobial and anticancer. The action mechanisms of these molecules, the urgent need to introduce alternative lead compounds and the current aspects on the exploitation and its limitations are discussed.

Mining the deep Red-Sea brine pool microbial community for anticancer therapeutics

BACKGROUND

Microbial species in the brine pools of the Red Sea and the brine pool-seawater interfaces are exposed to high temperature, high salinity, low oxygen levels and high concentrations of heavy metals. As adaptations to these harsh conditions require a large suite of secondary metabolites, these microbes have a huge potential as a source of novel anticancer molecules.

METHODS

A total of 60 ethyl-acetate extracts of newly isolated strains from extreme environments of the Red-Sea were isolated and tested against several human cancer cell lines for potential cytotoxic and apoptotic activities.

RESULTS

Isolates from the Erba brine-pool accounted for 50% of active bacterial extracts capable of inducing 30% or greater inhibition of cell growth. Among the 60 extracts screened, seven showed selectivity towards triple negative BT20 cells compared to normal fibroblasts.

CONCLUSION

In this study, we identified several extracts able to induce caspase-dependent apoptosis in various cancer cell lines. Further investigations and isolation of the active compounds of these Red Sea brine pool microbes may offer a chemotherapeutic potential for cancers with limited treatment options.

Marine anticancer drugs and their relevant targets: a treasure from the ocean

Marine organisms comprising animals and plants are wealthiest sources of bioactive compounds possessing various pharmacological properties specifically: free radical scavenging, antitumor, antimicrobial, analgesic, neuroprotective and immunomodulatory. Marine drugs provide an alternative source to meet the demand of effective, safe and low-cost drugs that are rising with the continuously growing world population. Cancer is one of the leading reasons of mortality in western nations in contrast to communicable diseases of developing nations. In spite of outstanding developments in cancer therapy in past three decades, there is still an insistent necessity for innovative drugs in the area of cancer biology, especially in the unexplored area of marine anticancer compounds. However, recent technological innovations in structure revelation, synthetic creation of new compounds and biological assays have made possible the isolation and clinical assessment of innumerable unique anticancer compounds from marine environment. This review provides an insight into the anticancer research so far conducted in the area of the marine natural products/synthetic derivatives, their possible molecular targets and the current challenges in the drug development. Graphical abstract.

Antibacterial and anticancer activities of orphan biosynthetic gene clusters from Atlantis II Red Sea brine pool

BACKGROUND

Cancer and infectious diseases are problematic because of continuous emergence of drug resistance. One way to address this enormous global health threat is bioprospecting the unlikeliest environments, such as extreme marine niches, which have tremendous biodiversity that is barely explored. One such environment is the Red Sea brine pool, Atlantis II Deep (ATII). Here, we functionally screened a fosmid library of metagenomic DNA isolated from the ATII lower convective layer (LCL) for antibacterial and anticancer activities.

RESULTS

Selected clones, 14-7E and 10-2G, displayed antibacterial effects on the marine strain Bacillus sp. Cc6. Moreover, whole cell lysates from 14-7E and 10-2G exhibited decreased cell viability against MCF-7 (39.1% ± 6.6, 42% ± 8.1 at 50% v/v) and U2OS cells (35.7% ± 1.9, 79.9% ± 5.9 at 50% v/v), respectively. By sequencing the insert DNA from 14-7E and 10-2G, we identified two putative orphan biosynthetic gene clusters. Both clusters harbored putative ATP-binding cassette (ABC) transporter permeases and S-adenosylmethionine-related genes. Interestingly, the biosynthetic gene cluster identified on 14-7E is of archaeal origin and harbors a putative transcription factor. Several identified genes may be responsible for the observed antibacterial and anticancer activities. The 14-7E biosynthetic gene cluster may be encoding enzymes producing a specialized metabolite (effect of detected genes involved in C-C bond formation and glycosylation). The bioactivity may also be due to predicted subtilases encoded by this cluster. The 10-2G cluster harbored putative glycosyltransferase and non-ribosomal peptide synthase genes; thus the observed activity of this clone could be caused by a bioactive peptide.

CONCLUSIONS

The ATII LCL prokaryotic metagenome hosts putative orphan biosynthetic gene clusters that confer antibiotic and anticancer effects. Further biochemical studies should characterize the detected bioactive components, and the potential use of 14-7E metabolite for antibiosis and 10-2G metabolite as a selective anti-breast cancer drug.

Supernatant Metabolites from Halophilic Archaea to Reduce Tumorigenesis in Prostate Cancer In-vitro and In-vivo

Halophilic archaea are known as the novel producers of natural products and their supernatant metabolites could have cytotoxic effects on cancer cells. In the present study, we screened the anticancer potential of supernatant metabolites from eight native haloarchaeal strains obtained from a culture collection in Iran. Five human cancer cell lines including breast, lung, prostate and also human fibroblast cells as the normal control were used in the present study. Moreover, to evaluate the anti-tumor effect of the selected supernatant, inhibition of sphere formation and tumor development was assessed in-vitro and in-vivo, respectively. Among all strains, supernatant metabolites from Halobacterium salinarum IBRC M10715 had the most potent cytotoxic effect on prostate cancer cell lines (IC50 = 0.5 mg/mL) without any effects on normal cells. It significantly increased both early and late apoptosis (about 11% and 9%, respectively) in the androgen-dependent PC3 cell line, reduced sphere formation ability of DU145 and PC3 cells with down-regulation of SOX2 gene expression. Furthermore, our results revealed that tumors developed in nude mice significantly shrank post intratumor injection of metabolites of the haloarchaeal strain. In conclusion, we suggested here for the first time that supernatant metabolites from Halobacterium salinarum IBRC M10715 could be a novel component against prostate cancer in-vitro and in-vivo with remarkable reduction in stem-like properties of tumor.

Antimicrobial activity of bacteria isolated from Red Sea marine invertebrates

Marine invertebrates-associated microorganisms were considered to be important sources of marine bioactive products. This study aims to isolate marine invertebrates associated bacteria with antimicrobial activity from the Red Sea and test their biosynthetic potential through the detection of PKS and NRPS gene clusters involved with the production of bioactive secondary metabolites. In this respect, fifty bacterial strains were isolated from eight different Red Sea marine invertebrates and screened for their antimicrobial activity against standard pathogenic bacteria (Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Bacillus subtilis ATCC 6633) and yeast (Candida albicans ATCC 10231) using the standard well diffusion assay. Five isolates showed antifungal activity against Candida albicans with no activity recorded against other pathogenic bacterial strains. On the other hand when these isolates were screened for the presence of biosynthetic gene clusters (PKS and NRPS) by PCR using five sets of degenerative primers, 60% of the isolates were shown to contain at least one type of PKS and NRPS gene clusters, which indicates the biosynthetic potential of these isolates even if the isolates didn't express any biological activity in vitro. Moreover the 16S rRNA molecular identification of the isolates reveal the biodiversity of the red sea marine invertebrates associated bacteria as they were found to belong to several bacterial groups present in Alphaproteobacteria, Gammaproteobacteria, Actinobacteria and Firmicutes.

Genome sequence analysis of Zooshikella ganghwensis strain VG4 and its potential for the synthesis of antimicrobial metabolites

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Draft genome sequence of Z. ganghwensis VG4 is reported.

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Culture supernatant of Z. ganghwensis VG4 exhibit antimicrobial properties.

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A total of 7634 genes are identified out of which 74% were annotated.

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Z. ganghwensis VG4 has genetic potential to synthesize bioactive secondary metabolites, such as, polyketides and nonribosomal peptides.

With antimicrobial resistance on the rise, the discovery of new compounds with novel structural scaffolds exhibiting antimicrobial properties has become an important area of research. Such compounds can serve as starting points for the development of new antimicrobials. In this report, we present the draft genome sequence of the Zooshikella ganghwensis strain VG4, isolated from Red Sea sediments, that produces metabolites with antimicrobial properties. A genomic analysis reveals that it carries at least five gene clusters that have the potential to direct biosynthesis of bioactive secondary metabolites such as polyketides and nonribosomal peptides. By using in-silico approaches, we predict the structure of these metabolites.

Microbial diversity of saline environments: searching for cytotoxic activities

In order to select halophilic microorganisms as a source of compounds with cytotoxic activities, a total of 135 bacterial strains were isolated from water and sediment samples collected from the Zipaquirá salt mine in the Colombian Andes. We determined the cytotoxic effects of 100 crude extracts from 54 selected organisms on the adherent murine mammary cell carcinoma 4T1 and human mammary adenocarcinoma MCF-7 cell lines. These extracts were obtained from strains of Isoptericola, Ornithinimicrobium, Janibacter, Nesterenkonia, Alkalibacterium, Bacillus, Halomonas, Chromohalobacter, Shewanella, Salipiger, Martellela, Oceanibaculum, Caenispirillum and Labrenzia. The extracts of 23 strains showed an IC₅₀ of less than 100 μg mL⁻¹. They were subsequently analyzed by LC/MS allowing dereplication of 20 compounds. The cytotoxic effect was related to a complex mixture of diketopiperazines present in many of the extracts analyzed. The greatest cytotoxic activity against both of the evaluated cell lines was obtained from the chloroform extract of Labrenzia aggregata USBA 371 which had an IC₅₀ < 6 μg mL⁻¹. Other extracts with high levels of cytotoxic activity were obtained from Bacillus sp. (IC₅₀ < 50 μg mL⁻¹) which contained several compounds such as macrolactin L and A, 7-O-succinoylmacrolactin F and iturin. Shewanella chilikensis USBA 344 also showed high levels of cytotoxic activity against both cell lines in the crude extract: an IC₅₀ < 15 μg mL⁻¹ against the 4T1 cell line and an IC₅₀ < 68 μg mL⁻¹ against the MCF-7 cell line. Nesterenkonia sandarakina CG 35, which has an IC₅₀ of 118 µg mL⁻¹ against 4T1, is a producer of diketopiperazines and 1-acetyl-β-carboline. Also, Ornithinimicrobium kibberense CG 24, which has IC₅₀ < 50 μg mL⁻¹, was a producer of diketopiperazines and lagunamycin. Our study demonstrates that these saline environments are habitats of halophilic and halotolerant bacteria that have previously unreported cytotoxic activity.

Antibacterial efficacy of silver nanoparticles and ethyl acetate's metabolites of the potent halophilic (marine) bacterium, Bacillus cereus A30 on multidrug resistant bacteria

Bacteria are generally responsible for the prevalence of several diseases and pathogenic bacteria are showing increasing resistance to different antibacterials. During the present study an extremophilic bacterium-A30 isolated from the marine waters was characterized and evaluated against four multi-drug resistant (MDR) pathogens, viz; Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The sensitivity pattern of the selected pathogens was tested with 31 antibiotics. Among the 47 marine microbial extracts tested on 4-MDR pathogens viz: Methicillin-resistant Staphylococcus aureus (MRSA), E. coli, K. pneumoniae and P. aeruginosa, only our strain A30 strain exhibited highest efficacy. This strain was subsequently subjected to 16S rDNA sequencing which confirmed its allocation as Bacillus cereus. Silver nanoparticle (AgNPs) synthesis and ethyl acetate extraction were performed using the supernatant of B. cereus. The synthesized AgNPs were characterized by UV-Visible, Fourier-transform infra-red (FT-IR), X-ray diffraction (XRD), Field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and Zeta potential analyses. The presence of functional groups and 13 bioactive components in the ethyl acetate extract were analyzed using FT-IR and gas chromatography-mass spectrometry (GC-MS). The synthesized of AgNPs and the ethyl acetate extract showed preponderant activity against P. aeruginosa and MRSA, respectively. The effects of AgNPs were significant when compared to ethyl acetate extract. Therefore, the halophilic bacterium, B. cereus mediated AgNPs could provide antibacterial applications in the biomedical industries.

Building a bio-based industry in the Middle East through harnessing the potential of the Red Sea biodiversity

The incentive for developing microbial cell factories for production of fuels and chemicals comes from the ability of microbes to deliver these valuable compounds at a reduced cost and with a smaller environmental impact compared to the analogous chemical synthesis. Another crucial advantage of microbes is their great biological diversity, which offers a much larger "catalog" of molecules than the one obtainable by chemical synthesis. Adaptation to different environments is one of the important drives behind microbial diversity. We argue that the Red Sea, which is a rather unique marine niche, represents a remarkable source of biodiversity that can be geared towards economical and sustainable bioproduction processes in the local area and can be competitive in the international bio-based economy. Recent bioprospecting studies, conducted by the King Abdullah University of Science and Technology, have established important leads on the Red Sea biological potential, with newly isolated strains of Bacilli and Cyanobacteria. We argue that these two groups of local organisms are currently most promising in terms of developing cell factories, due to their ability to operate in saline conditions, thus reducing the cost of desalination and sterilization. The ability of Cyanobacteria to perform photosynthesis can be fully exploited in this particular environment with one of the highest levels of irradiation on the planet. We highlight the importance of new experimental and in silico methodologies needed to overcome the hurdles of developing efficient cell factories from the Red Sea isolates.

Bioprospecting Red Sea Coastal Ecosystems for Culturable Microorganisms and Their Antimicrobial Potential

Microorganisms that inhabit unchartered unique soil such as in the highly saline and hot Red Sea lagoons on the Saudi Arabian coastline, represent untapped sources of potentially new bioactive compounds. In this study, a culture-dependent approach was applied to three types of sediments: mangrove mud (MN), microbial mat (MM), and barren soil (BS), collected from Rabigh harbor lagoon (RHL) and Al-Kharrar lagoon (AKL). The isolated bacteria were evaluated for their potential to produce bioactive compounds. The phylogenetic characterization of 251 bacterial isolates based on the 16S rRNA gene sequencing, supported their assignment to five different phyla: Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, and Planctomycetes. Fifteen putative novel species were identified based on a 16S rRNA gene sequence similarity to other strain sequences in the NCBI database, being ≤98%. We demonstrate that 49 of the 251 isolates exhibit the potential to produce antimicrobial compounds. Additionally, at least one type of biosynthetic gene sequence, responsible for the synthesis of secondary metabolites, was recovered from 25 of the 49 isolates. Moreover, 10 of the isolates had a growth inhibition effect towards Staphylococcus aureus, Salmonella typhimurium and Pseudomonas syringae. We report the previously unknown antimicrobial activity of B. borstelensis, P. dendritiformis and M. salipaludis against all three indicator pathogens. Our study demonstrates the evidence of diverse cultured microbes associated with the Red Sea harbor/lagoon environments and their potential to produce antimicrobial compounds.

A catalogue of 136 microbial draft genomes from Red Sea metagenomes

Earth is expected to continue warming and the Red Sea is a model environment for understanding the effects of global warming on ocean microbiomes due to its unusually high temperature, salinity and solar irradiance. However, most microbial diversity analyses of the Red Sea have been limited to cultured representatives and single marker gene analyses, hence neglecting the substantial uncultured majority. Here, we report 136 microbial genomes (completion minus contamination is ≥50%) assembled from 45 metagenomes from eight stations spanning the Red Sea and taken from multiple depths between 10 to 500 m. Phylogenomic analysis showed that most of the retrieved genomes belong to seven different phyla of known marine microbes, but more than half representing currently uncultured species. The open-access data presented here is the largest number of Red Sea representative microbial genomes reported in a single study and will help facilitate future studies in understanding the physiology of these microorganisms and how they have adapted to the relatively harsh conditions of the Red Sea.

Cytotoxic Effects of Tropodithietic Acid on Mammalian Clonal Cell Lines of Neuronal and Glial Origin

The marine metabolite tropodithietic acid (TDA), produced by several Roseobacter clade bacteria, is known for its broad antimicrobial activity. TDA is of interest not only as a probiotic in aquaculture, but also because it might be of use as an antibacterial agent in non-marine or non-aquatic environments, and thus the potentially cytotoxic influences on eukaryotic cells need to be evaluated. The present study was undertaken to investigate its effects on cells of the mammalian nervous system, i.e., neuronal N2a cells and OLN-93 cells as model systems for nerve cells and glia. The data show that in both cell lines TDA exerted morphological changes and cytotoxic effects at a concentration of 0.3–0.5 µg/mL (1.4–2.4 µM). Furthermore, TDA caused a breakdown of the mitochondrial membrane potential, the activation of extracellular signal-regulated kinases ERK1/2, and the induction of the small heat shock protein HSP32/HO-1, which is considered as a sensor of oxidative stress. The cytotoxic effects were accompanied by an increase in intracellular Ca²⁺-levels, the disturbance of the microtubule network, and the reorganization of the microfilament system. Hence, mammalian cells are a sensitive target for the action of TDA and react by the activation of a stress response resulting in cell death.

Metagenomic studies of the Red Sea

Metagenomics has significantly advanced the field of marine microbial ecology, revealing the vast diversity of previously unknown microbial life forms in different marine niches. The tremendous amount of data generated has enabled identification of a large number of microbial genes (metagenomes), their community interactions, adaptation mechanisms, and their potential applications in pharmaceutical and biotechnology-based industries. Comparative metagenomics reveals that microbial diversity is a function of the local environment, meaning that unique or unusual environments typically harbor novel microbial species with unique genes and metabolic pathways. The Red Sea has an abundance of unique characteristics; however, its microbiota is one of the least studied among marine environments. The Red Sea harbors approximately 25 hot anoxic brine pools, plus a vibrant coral reef ecosystem. Physiochemical studies describe the Red Sea as an oligotrophic environment that contains one of the warmest and saltiest waters in the world with year-round high UV radiations. These characteristics are believed to have shaped the evolution of microbial communities in the Red Sea. Over-representation of genes involved in DNA repair, high-intensity light responses, and osmoregulation were found in the Red Sea metagenomic databases suggesting acquisition of specific environmental adaptation by the Red Sea microbiota. The Red Sea brine pools harbor a diverse range of halophilic and thermophilic bacterial and archaeal communities, which are potential sources of enzymes for pharmaceutical and biotechnology-based application. Understanding the mechanisms of these adaptations and their function within the larger ecosystem could also prove useful in light of predicted global warming scenarios where global ocean temperatures are expected to rise by 1-3°C in the next few decades. In this review, we provide an overview of the published metagenomic studies that were conducted in the Red Sea, and the bio-prospecting potential of the Red Sea microbiota. Furthermore, we discuss the limitations of the previous studies and the need for generating a large and representative metagenomic database of the Red Sea to help establish a dynamic model of the Red Sea microbiota.

Induction of apoptosis in cancer cell lines by the Red Sea brine pool bacterial extracts

BACKGROUND

Marine microorganisms are considered to be an important source of bioactive molecules against various diseases and have great potential to increase the number of lead molecules in clinical trials. Progress in novel microbial culturing techniques as well as greater accessibility to unique oceanic habitats has placed the marine environment as a new frontier in the field of natural product drug discovery.

METHODS

A total of 24 microbial extracts from deep-sea brine pools in the Red Sea have been evaluated for their anticancer potential against three human cancer cell lines. Downstream analysis of these six most potent extracts was done using various biological assays, such as Caspase-3/7 activity, mitochondrial membrane potential (MMP), PARP-1 cleavage and expression of γH2Ax, Caspase-8 and -9 using western blotting.

RESULTS

In general, most of the microbial extracts were found to be cytotoxic against one or more cancer cell lines with cell line specific activities. Out of the 13 most active microbial extracts, six extracts were able to induce significantly higher apoptosis (>70%) in cancer cells. Mechanism level studies revealed that extracts from Chromohalobacter salexigens (P3-86A and P3-86B(2)) followed the sequence of events of apoptotic pathway involving MMP disruption, caspase-3/7 activity, caspase-8 cleavage, PARP-1 cleavage and Phosphatidylserine (PS) exposure, whereas another Chromohalobacter salexigens extract (K30) induced caspase-9 mediated apoptosis. The extracts from Halomonas meridiana (P3-37B), Chromohalobacter israelensis (K18) and Idiomarina loihiensis (P3-37C) were unable to induce any change in MMP in HeLa cancer cells, and thus suggested mitochondria-independent apoptosis induction. However, further detection of a PARP-1 cleavage product, and the observed changes in caspase-8 and -9 suggested the involvement of caspase-mediated apoptotic pathways.

CONCLUSION

Altogether, the study offers novel findings regarding the anticancer potential of several halophilic bacterial species inhabiting the Red Sea (at the depth of 1500-2500 m), which constitute valuable candidates for further isolation and characterization of bioactive molecules.