Culturable marine actinomycete diversity from tropical Pacific Ocean sediments

Dynamics and functions of biomarker taxa determine substrate-specific organic waste composting

Bacteria are an influential component of diverse composting microbiomes, but their structure and underlying dynamics are poorly understood. This study analyzed the bacterial communities of 577 compost datasets globally and constructed a substrate-dependent catalog with more than 15 million non-redundant 16S rRNA gene sequences. Using a random-forest machine-learning model, 30 biomarker taxa were identified that accurately distinguish between the food, sludge and manure waste composting microbiomes (accuracy >98 %). These biomarker taxa were closely associated with carbon and nitrogen metabolic processes, during which they contributed to the predominant stochastic process and are influenced by different factors in the substrate-specific composts. This is corroborated by the community topological characteristics, which feature the biomarkers as keystone taxa maintaining the bacterial network stability. These findings provide a theoretical basis to identify and enhance the biomarker-functional bacteria for optimizing the composting performance of different organic wastes.

Unveiling the bioactive potential of Actinomycetota from the Tagus River estuary

The increase in global travel and the incorrect and excessive use of antibiotics has led to an unprecedented rise in antibiotic resistance in bacterial and fungal populations. To overcome these problems, novel bioactive natural products must be discovered, which may be found in underexplored environments, such as estuarine habitats. In the present work, estuarine actinomycetotal strains were isolated with conventional and iChip techniques from the Tagus estuary in Alcochete, Portugal, and analysed for different antimicrobial bioactivities. Extracts were produced from the isolated cultures and tested for bioactivity against Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Aspergillus fumigatus ATCC 240305, Candida albicans ATCC 10231 and Trichophyton rubrum FF5. Furthermore, bioactive extracts were subjected to dereplication by high-performance liquid chromatography (HPLC) and high-resolution mass spectrometry (HRMS) to putatively identify their chemical components. In total, 105 isolates belonging to 3 genera were obtained. One which was isolated, MTZ3.1 T, represents a described novel taxon for which the name Streptomyces meridianus was proposed. Regarding the bioactivity testing, extracts from 12 strains proved to be active against S. aureus, 2 against E. coli, 4 against A. fumigatus, 3 against C. albicans and 10 against T. rubrum. Dereplication of bioactive extracts showed the presence of 28 known bioactive molecules, 35 hits have one or more possible matches in the DNP and 18 undescribed ones. These results showed that the isolated bacteria might be the source of new bioactive natural products.

Micromonosporaceae biosynthetic gene cluster diversity highlights the need for broad-spectrum investigations

Investigations of the bacterial family Micromonosporaceae have enabled the development of secondary metabolites critical to human health. Historical investigation of bacterial families for natural product discovery has focused on terrestrial strains, where time-consuming isolation processes often lead to the rediscovery of known compounds. To investigate the secondary metabolite potential of marine-derived Micromonosporaceae , 38 strains were sequenced, assembled and analysed using antiSMASH and BiG-SLiCE. BiG-SLiCE contains a near-comprehensive dataset of approximately 1.2 million publicly available biosynthetic gene clusters from primarily terrestrial strains. Our marine-derived Micromonosporaceae were directly compared to BiG-SLiCE’s preprocessed database using BiG-SLiCE’s query mode; genetic diversity within our strains was uncovered using BiG-SCAPE and metric multidimensional scaling analysis. Our analysis of marine-derived Micromonosporaceae emphasizes the clear need for broader genomic investigations of marine strains to fully realize their potential as sources of new natural products.

Ecobiology and distribution of Streptomyces species from distinctive metal polluted sediment of tropical estuary, Northwest coast of India

The present study aims to isolate diverse actinomycetes communities from the estuarine sediments of Patalganga located at Northwest coast of India. Total 40 actinomycetes were isolated from 24 sediment samples by dilution plating on six different isolation media. Among them, morphologically 18 distinct selected isolates of actinomycetes were verified by 16S rRNA gene sequencing and identified as Streptomyces spp. The relationship between diversity of total actinomycetes population (TAP) and its antagonistic behaviour with the physico-chemical characteristics of sediment samples were investigated. Multiple regression analysis revealed that the influencing physico-chemical factors comprises of sediment temperature, sediment pH, organic carbon and heavy metals. The results of statistical analysis showed that TAP is positively correlated (p < 0.01) with sediment organic carbon whereas, negatively correlated with Cr (p < 0.05) and Mn (p < 0.01). Based on Principle component Analysis (PCA) and cluster analysis results, the obtained six stations can be divided into three groups. Among them mobile fraction of metals, TAP could be the main factor reflecting the lower and middle estuary. The recovery of large number of actinomycete isolates suggests that Patalganga Estuary could be potential source of bioactive compounds with biosynthetic capabilities.

Draft Genome Sequence of Streptomyces sp. Strain G-5, Isolated from Marine Sponge, Kochi Prefecture, Japan

Actinomycetes isolated from the marine environment often require the presence of seawater for their growth and/or morphological development. Here, we report the isolation and genome sequencing of marine sponge-derived Streptomyces sp. strain G-5 with such a seawater requirement.

Habitat-adapted heterologous symbiont Salinispora arenicola promotes growth and alleviates salt stress in tomato crop plants

To ensure food security given the current scenario of climate change and the accompanying ecological repercussions, it is essential to search for new technologies and tools for agricultural production. Microorganism-based biostimulants are recognized as sustainable alternatives to traditional agrochemicals to enhance and protect agricultural production. Marine actinobacteria are a well-known source of novel compounds for biotechnological uses. In addition, former studies have suggested that coral symbiont actinobacteria may support co-symbiotic photosynthetic growth and tolerance and increase the probability of corals surviving abiotic stress. We have previously shown that this activity may also hold in terrestrial plants, at least for the actinobacteria Salinispora arenicola during induced heterologous symbiosis with a wild Solanaceae plant Nicotiana attenuata under in vitro conditions. Here, we further explore the heterologous symbiotic association, germination, growth promotion, and stress relieving activity of S. arenicola in tomato plants under agricultural conditions and dig into the possible associated mechanisms. Tomato plants were grown under normal and saline conditions, and germination, bacteria-root system interactions, plant growth, photosynthetic performance, and the expression of salt stress response genes were analyzed. We found an endophytic interaction between S. arenicola and tomato plants, which promotes germination and shoot and root growth under saline or non-saline conditions. Accordingly, photosynthetic and respective photoprotective performance was enhanced in line with the induced increase in photosynthetic pigments. This was further supported by the overexpression of thermal energy dissipation, which fine-tunes energy use efficiency and may prevent the formation of reactive oxygen species in the chloroplast. Furthermore, gene expression analyses suggested that a selective transport channel gene, SlHKT1,2, induced by S. arenicola may assist in relieving salt stress in tomato plants. The fine regulation of photosynthetic and photoprotective responses, as well as the inhibition of the formation of ROS molecules, seems to be related to the induced down-regulation of other salt stress response genes, such as SlDR1A-related genes or SlAOX1b. Our results demonstrate that the marine microbial symbiont S. arenicola establishes heterologous symbiosis in crop plants, promotes growth, and confers saline stress tolerance. Thus, these results open opportunities to further explore the vast array of marine microbes to enhance crop tolerance and food production under the current climate change scenario.

iChip-Inspired Isolation, Bioactivities and Dereplication of Actinomycetota from Portuguese Beach Sediments

Oceans hold a stunning number of unique microorganisms, which remain unstudied by culture-dependent methods due to failures in establishing the right conditions for these organisms to grow. In this work, an isolation effort inspired by the iChip was performed using marine sediments from Memoria beach, Portugal. The isolates obtained were identified by 16S rRNA gene analysis, fingerprinted using BOX-PCR and ERIC-PCR, searched for the putative presence of secondary metabolism genes associated with polyketide synthase I (PKS-I) and non-ribosomal peptide synthetases (NRPS), screened for antimicrobial activity against Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213, and had bioactive extracts dereplicated by LC/HRMS. Of the 158 isolated strains, 96 were affiliated with the phylum Actinomycetota, PKS-I and NRPS genes were detected in 53 actinomycetotal strains, and 11 proved to be bioactive (10 against E. coli, 1 against S. aureus and 1 against both pathogens). Further bioactivities were explored using an “one strain many compounds” approach, with six strains showing continued bioactivity and one showing a novel one. Extract dereplication showed the presence of several known bioactive molecules and potential novel ones in the bioactive extracts. These results indicate the use of the bacteria isolated here as sources of new bioactive natural products.

Characterization of Bioactive Actinomycetes Isolated from Kadolkele Mangrove Sediments, Sri Lanka

Exploring untapped microbial potentials in previously uncharted environments has become crucial in discovering novel secondary metabolites and enzymes for biotechnological applications. Among prokaryotes, actinomycetes are well recognized for producing a vast range of secondary metabolites and extracellular enzymes. In the present study, we have used surface sediments from ‘Kadolkele’ mangrove ecosystem located in the Negombo lagoon area, Sri Lanka, to isolate actinomycetes with bioactive potentials. A total of six actinomycetes were isolated on modified-starch casein agar and characterized. The isolates were evaluated for their antibacterial activity against four selected bacterial strains and to produce extracellular enzymes: cellulase, amylase, protease, and lipase. Three out of the six isolates exhibited antibacterial activity against Staphylococcus aureus, Escherichia coli, and Bacillus cereus, but not against Listeria monocytogenes. Five strains could produce extracellular cellulase, while all six isolates exhibited amylase activity. Only three of the six isolates were positive for protease and lipase assays separately. Ac-1, Ac-2, and Ac-9, identified as Streptomyces spp. with the 16S rRNA gene sequencing, were used for pigment extraction using four different solvents. Acetone-extracted crude pigments of Ac-1

and Ac-2 were further used in well-diffusion assays, and growth inhibition of test bacteria was observed only with the crude pigment extract of Ac-2. Further, six different commercially available fabrics were dyed with crude pigments of Ac-1. The dyed fabrics retained the yellow color after acid, alkaline, and cold-water treatments suggesting the potential of the Ac-1 pigment to be used in biotechnological applications.

Antibiotic-producing Micrococcales govern the microbiome that inhabits the fur of two- and three-toed sloths

Sloths have a dense coat on which insects, algae, and fungi coexist in a symbiotic relationship. This complex ecosystem requires different levels of control, however, most of these mechanisms remain unknown. We investigated the bacterial communities inhabiting the hair of two- (Choloepus Hoffmani) and three-toed (Bradypus variegatus) sloths and evaluated their potential for producing antibiotic molecules capable of exerting control over the hair microbiota. The analysis of 16S rRNA amplicon sequence variants (ASVs) revealed that the communities in both host species are dominated by Actinobacteriota and Firmicutes. The most abundant genera were Brevibacterium, Kocuria/Rothia, Staphylococcus, Rubrobacter, Nesterenkonia, and Janibacter. Furthermore, we isolated nine strains of Brevibacterium and Rothia capable of producing substances that inhibited the growth of common mammalian pathogens. The analysis of the biosynthetic gene clusters (BCGs) of these nine isolates suggests that the pathogen-inhibitory activity could be mediated by the presence of siderophores, terpenes, beta-lactones, Type III polyketide synthases (T3PKS), ribosomally synthesized, and post-translationally modified peptides (RiPPs), non-alpha poly-amino acids (NAPAA) like e-Polylysin, ectoine or nonribosomal peptides (NRPs). Our data suggest that Micrococcales that inhabit sloth hair could have a role in controlling microbial populations in that habitat, improving our understanding of this highly complex ecosystem. This article is protected by copyright. All rights reserved.

Anti-Tyrosinase Compounds from the Deep-Sea-Derived Actinomycete Georgenia sp. 40DY180

With the aim of finding new marine-derived skincare promoters, an assay-guided approach was employed to discover tyrosinase-modulating compounds from marine actinomycete. Here we describe a new 2,5-piperazinedione, named georgenione A (1), together with two previously described compounds, 5-(4'-hydroxybenzyl)hydantoin (2) and cyclo(Trp-Gly) (3), produced by actinomycete Georgenia sp. 40DY180, isolated from deep-sea sediments collected in the Pacific Ocean. Their structures were elucidated by a combination of spectroscopic analyses including 1D and 2D NMR and high-resolution mass spectrometric data. 5-(4'-hydroxybenzyl)hydantoin (2) displayed in vitro potent anti-tyrosinase activity with IC₅₀ value of 36 μM, comparable to the commercially used positive control kojic acid (IC₅₀ =46 μM) and arbutin (IC₅₀ =100 μM). Compounds 1-3 were firstly reported from marine actinomycete Georgenia sp.

Salsipaludibacter albus gen. nov., sp. nov., a novel actinobacterial strain isolate from a Portuguese solar saltern and proposal of Salsipaludibacteraceae fam. nov. and Salsipaludibacterales ord. nov

A novel micro-organism designated AS10T was isolated from dry salt collected from Aveiro saltern in the north of Portugal. Cells were Gram-stain-positive, non-motile, non-endospore-forming, rod-shaped and aerobic. Strain AS10T was characterized by long filaments of rod-shaped cells, presenting also coccoid cellular forms at the end of the filaments, unveiling some pleomorphism. Rod-shaped cells varied from 0.3 to 0.6 µm wide and from 0.6 to 2 µm long. Growth of AS10T occurred at 15–40 °C (optimum, 20–30 °C), 0–10% (w/v) NaCl (optimum, 2%) and pH 4.5–11.0 (optimum, pH 8.0–11.0). The peptidoglycan type was A1ϒ-type with 3-hydroxy-diaminopimelic acid. The major fatty acids were C16:0, iso-C14:0, C17:0 and C14:0. The major respiratory quinone was MK-9(H4). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AS10T was similar to actinobacterial members of the class Nitriliruptoria , with Nitriliruptor alkaliphilus ANL-iso2T being the closest relative the species with a sequence pairwise similarity of 91.21%. Average nucleotide identity, average amino acid identity and in silico DNA–DNA hybridization values between strain AS10T and N. alkaliphilus ANL-iso2T were 71.34, 53.57 and 18.90%, respectively. The genome DNA G+C content of AS10T was 71.8 mol%. Based on genomic, phylogenetic, phenotypic and chemotaxonomic studies, we describe a new species of a novel genus represented by strain AS10T (=LMG 31937T=CECT 30148T) for which we propose the name Salsipaludibacter albus gen. nov., sp. nov. We also propose that this organism represents a new family named Salsipaludibacteraceae fam. nov. of a novel order named Salsipaludibacterales ord. nov.

The Diversity, Metabolomics Profiling, and the Pharmacological Potential of Actinomycetes Isolated from the Estremadura Spur Pockmarks (Portugal)

The Estremadura Spur pockmarks are a unique and unexplored ecosystem located in the North Atlantic, off the coast of Portugal. A total of 85 marine-derived actinomycetes were isolated and cultured from sediments collected from this ecosystem at a depth of 200 to 350 m. Nine genera, Streptomyces, Micromonospora, Saccharopolyspora, Actinomadura, Actinopolymorpha, Nocardiopsis, Saccharomonospora, Stackebrandtia, and Verrucosispora were identified by 16S rRNA gene sequencing analyses, from which the first two were the most predominant. Non-targeted LC-MS/MS, in combination with molecular networking, revealed high metabolite diversity, including several known metabolites, such as surugamide, antimycin, etamycin, physostigmine, desferrioxamine, ikarugamycin, piericidine, and rakicidin derivatives, as well as numerous unidentified metabolites. Taxonomy was the strongest parameter influencing the metabolite production, highlighting the different biosynthetic potentials of phylogenetically related actinomycetes; the majority of the chemical classes can be used as chemotaxonomic markers, as the metabolite distribution was mostly genera-specific. The EtOAc extracts of the actinomycete isolates demonstrated antimicrobial and antioxidant activity. Altogether, this study demonstrates that the Estremadura Spur is a source of actinomycetes with potential applications for biotechnology. It highlights the importance of investigating actinomycetes from unique ecosystems, such as pockmarks, as the metabolite production reflects their adaptation to this habitat.

Selective isolation, antimicrobial screening and phylogenetic diversity of marine actinomycetes derived from the Coast of Bejaia City (Algeria), a polluted and microbiologically unexplored environment

AIMS

The current study aimed to evaluate the occurrence of actinomycetes in the Coast of Bejaia City using selective isolation, as well as their bioactivity and phylogenitic diversity.

METHODS AND RESULTS

Different selective media and methods were used, leading to the isolation of 103 actinomycete strains. The number of strains was influenced by isolation procedures and their interactions based on a three-way ANOVA and a post hoc Tukey test, which revealed that using M2 medium, dilution of samples followed by moderate heat treatment, and sampling at 10-20 m yielded the highest numbers of actinomycetes. The isolates were screened for their antimicrobial activity against human pathogenic microorganisms using agar and well diffusion methods. Of all the isolates, ten displayed activity against at least one Gram-positive bacterium, of which P21 showed the highest activity against Staphylococcus aureus, Methicillin-resistant S. aureus and Bacillus subtilis, with a diameter of 32, 28 and 25 mm respectively. Subsequently, active isolates were assigned to Streptomyces spp. and Nocardiopsis spp. based on 16S rRNA gene sequencing, including a putative new Streptomyces species (S3). The phenotypic characteristics of the P21 strain were determined, and interesting enzymatic capacities were shown.

CONCLUSION

The recovery of actinomycetes along the Coast of Bejaia City was influenced by the isolation procedure. Ten strains displayed interesting antibacterial activity against Gram-positive bacteria, of which the P21 strain was selected as the most active strain.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work provides a new insight into the occurrence of actinobacteria in the Coast of Bejaia. It suggests also that polluted environments such as Bejaia Bay could provide access to interesting actinomycetes as sources of antibiotic leads.

Isolation and identification of marine microbial products

Background

The ocean is one of the world’s most important sources of bioactive chemicals in the marine environment. Microbiologists, ecologists, agronomists, taxonomists, and evolutionary biologists have been increasingly interested in marine microbial natural products (MMNPs) in recent decades.

Main body

Diverse marine bacteria appear to get the ability to manufacture an astounding diversity of MMNPs with a wide range of biological actions, including anti-tumor, antimicrobial, and anti-cardiovascular agents according to numerous studies.

Short conclusions

Innovative isolation and culture methodologies, tactics for identifying novel MMNPs via routine screens, metagenomics, genomics, combinatorial biosynthesis, and synthetic biology are all discussed in this review. There is also a discussion of potential issues and future directions for studying MMNPs.

Assessing the Diversity and Biomedical Potential of Microbes Associated With the Neptune's Cup Sponge, Cliona patera

Marine sponges are known to host a complex microbial consortium that is essential to the health and resilience of these benthic invertebrates. These sponge-associated microbes are also an important source of therapeutic agents. The Neptune's Cup sponge, Cliona patera, once believed to be extinct, was rediscovered off the southern coast of Singapore in 2011. The chance discovery of this sponge presented an opportunity to characterize the prokaryotic community of C. patera. Sponge tissue samples were collected from the inner cup, outer cup and stem of C. patera for 16S rRNA amplicon sequencing. C. patera hosted 5,222 distinct OTUs, spanning 26 bacterial phyla, and 74 bacterial classes. The bacterial phylum Proteobacteria, particularly classes Gammaproteobacteria and Alphaproteobacteria, dominated the sponge microbiome. Interestingly, the prokaryotic community structure differed significantly between the cup and stem of C. patera, suggesting that within C. patera there are distinct microenvironments. Moreover, the cup of C. patera had lower diversity and evenness as compared to the stem. Quorum sensing inhibitory (QSI) activities of selected sponge-associated marine bacteria were evaluated and their organic extracts profiled using the MS-based molecular networking platform. Of the 110 distinct marine bacterial strains isolated from sponge samples using culture-dependent methods, about 30% showed quorum sensing inhibitory activity. Preliminary identification of selected QSI active bacterial strains revealed that they belong mostly to classes Alphaproteobacteria and Bacilli. Annotation of the MS/MS molecular networkings of these QSI active organic extracts revealed diverse classes of natural products, including aromatic polyketides, siderophores, pyrrolidine derivatives, indole alkaloids, diketopiperazines, and pyrone derivatives. Moreover, potential novel compounds were detected in several strains as revealed by unique molecular families present in the molecular networks. Further research is required to determine the temporal stability of the microbiome of the host sponge, as well as mining of associated bacteria for novel QS inhibitors.

Marine Actinomycetes, New Sources of Biotechnological Products

The Actinomycetales order is one of great genetic and functional diversity, including diversity in the production of secondary metabolites which have uses in medical, environmental rehabilitation, and industrial applications. Secondary metabolites produced by actinomycete species are an abundant source of antibiotics, antitumor agents, anthelmintics, and antifungals. These actinomycete-derived medicines are in circulation as current treatments, but actinomycetes are also being explored as potential sources of new compounds to combat multidrug resistance in pathogenic bacteria. Actinomycetes as a potential to solve environmental concerns is another area of recent investigation, particularly their utility in the bioremediation of pesticides, toxic metals, radioactive wastes, and biofouling. Other applications include biofuels, detergents, and food preservatives/additives. Exploring other unique properties of actinomycetes will allow for a deeper understanding of this interesting taxonomic group. Combined with genetic engineering, microbial experimental evolution, and other enhancement techniques, it is reasonable to assume that the use of marine actinomycetes will continue to increase. Novel products will begin to be developed for diverse applied research purposes, including zymology and enology. This paper outlines the current knowledge of actinomycete usage in applied research, focusing on marine isolates and providing direction for future research.

Molecular characterization of marine bacterial isolates of Visakhapatnam coast-efficacy in dye decolorization and bioremediation of cadmium

Background

Microbial community is one of the diversified communities of the marine environment. Studies have shown that microorganisms isolated from the marine environment are metabolically active and have adapted to life in the ocean. The marine microorganisms use various survival strategies to combat heavy metal stress and decolorization of various textile dyes, thus playing an important role in the bioremediation of cadmium and degradation of textile dyes. The present study deals with the isolation and 16S rRNA molecular characterization of M3 and M8 bacterial strains isolated from marine water samples collected from Visakhapatnam harbor. M3 and M8 isolates were also checked for their efficacy in the removal of cadmium and decolorization of various textile dyes from the environment.

Results

The water sample was subjected to tube dilution method to isolate bacterial strains, and ten different isolates were screened. The biochemical tests were performed for the isolates to prove their validity and 16S rRNA molecular sequencing and phylogenetic analysis for species identification. Out of interest, two bacterial strains, namely, M3 and M8 were subjected to 16S rRNA molecular sequencing and phylogenetic analysis and were identified as Bacillus subtilis and Pseudomonas resinovorans. The two bacterial strains showed promising dye degradation property when checked with nine different textile dyes of wavelength ranging from 400 to 600 nm and removal of cadmium from the growth medium.

Conclusion

The present study demonstrates the isolates M3 and M8 to be potential strains having dye decolorization and bioremediation of cadmium applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-021-00189-0.

Grincamycins P-T: Rearranged Angucyclines from the Marine Sediment-Derived Streptomyces sp. CNZ-748 Inhibit Cell Lines of the Rare Cancer Pseudomyxoma Peritonei

While marine natural products have been investigated for anticancer drug discovery, they are barely screened against rare cancers. Thus, in our effort to discover potential drug leads against the rare cancer pseudomyxoma peritonei (PMP), which currently lacks effective drug treatments, we screened extracts of marine actinomycete bacteria against the PMP cell line ABX023-1. This effort led to the isolation of nine rearranged angucyclines from Streptomyces sp. CNZ-748, including five new analogues, namely, grincamycins P-T (1-5). The chemical structures of these compounds were unambiguously established based on spectroscopic and chemical analyses. Particularly, grincamycin R (3) possesses an S-containing α-l-methylthio-aculose residue, which was discovered in nature for the first time. All of the isolated compounds were evaluated against four PMP cell lines and some exhibited low micromolar inhibitory activities. To identify a candidate biosynthetic gene cluster (BGC) encoding the grincamycins, we sequenced the genome of the producing strain, Streptomyces sp. CNZ-748, and compared the BGCs detected with those linked to the production of angucyclines with different aglycon structures.

Phylogenetic analysis of the salinipostin γ-butyrolactone gene cluster uncovers new potential for bacterial signalling-molecule diversity

Bacteria communicate by small-molecule chemicals that facilitate intra- and inter-species interactions. These extracellular signalling molecules mediate diverse processes including virulence, bioluminescence, biofilm formation, motility and specialized metabolism. The signalling molecules produced by members of the phylum Actinobacteria generally comprise γ-butyrolactones, γ-butenolides and furans. The best-known actinomycete γ-butyrolactone is A-factor, which triggers specialized metabolism and morphological differentiation in the genus Streptomyces . Salinipostins A–K are unique γ-butyrolactone molecules with rare phosphotriester moieties that were recently characterized from the marine actinomycete genus Salinispora . The production of these compounds has been linked to the nine-gene biosynthetic gene cluster (BGC) spt . Critical to salinipostin assembly is the γ-butyrolactone synthase encoded by spt9 . Here, we report the surprising distribution of spt9 homologues across 12 bacterial phyla, the majority of which are not known to produce γ-butyrolactones. Further analyses uncovered a large group of spt -like gene clusters outside of the genus Salinispora , suggesting the production of new salinipostin-like diversity. These gene clusters show evidence of horizontal transfer and location-specific recombination among Salinispora strains. The results suggest that γ-butyrolactone production may be more widespread than previously recognized. The identification of new γ-butyrolactone BGCs is the first step towards understanding the regulatory roles of the encoded small molecules in Actinobacteria.

Flavonoids from Marine-Derived Actinobacteria as Anticancer Drugs

Flavonoids represent a large diverse group of natural products that are used as a traditional medicine against various infectious diseases. They possess many biological activities including antimicrobial, antioxidant, anti-inflammatory, anti-cancer and anti-diabetic activities. Commercially, flavonoids are mainly obtained from plants, however, several challenges are faced during their extraction. Microorganisms have been known as natural sources of a wide range of bioactive compounds including flavonoids. Actinobacteria are the most prolific group of microorganisms for the production of bioactive secondary metabolites, thus facilitating the production of flavonoids. The screening programs for bioactive compounds revealed the potential application of actinobacteria to produce flavonoids with interesting biological activities, especially anticancer activities. Since marine actinobacteria are recognized as a potential source of novel anticancer agents, they are highly expected to be potential producers of anticancer flavonoids with unusual structures and properties. In this review, we highlight the production of flavonoids by actinobacteria through classical fermentation, engineering of plant biosynthetic genes in a recombinant actinobacterium and the de novo biosynthesis approach. Through these approaches, we can control and improve the production of interesting flavonoids or their derivatives for the treatment of cancer.

Phytoplankton trigger the production of cryptic metabolites in the marine actinobacterium Salinispora tropica

Filamentous members of the phylum Actinobacteria are a remarkable source of natural products with pharmaceutical potential. The discovery of novel molecules from these organisms is, however, hindered because most of the biosynthetic gene clusters (BGCs) encoding these secondary metabolites are cryptic or silent and are referred to as orphan BGCs. While co-culture has proven to be a promising approach to unlock the biosynthetic potential of many microorganisms by activating the expression of these orphan BGCs, it still remains an underexplored technique. The marine actinobacterium Salinispora tropica, for instance, produces valuable compounds such as the anti-cancer molecule salinosporamide but half of its putative BGCs are still orphan. Although previous studies have used marine heterotrophs to induce orphan BGCs in Salinispora, its co-culture with marine phototrophs has yet to be investigated. Following the observation of an antimicrobial activity against a range of phytoplankton by S. tropica, we here report that the photosynthate released by photosynthetic primary producers influences its biosynthetic capacities with production of cryptic molecules and the activation of orphan BGCs. Our work, using an approach combining metabolomics and proteomics, pioneers the use of phototrophs as a promising strategy to accelerate the discovery of novel natural products from marine actinobacteria.

Draft Genome Sequence of Salinispora sp. Strain H7-4, Isolated from Deep-Sea Sediments of the Shikoku Basin

Salinispora spp. are obligate marine actinomycetes reported mainly from shallow tropical and subtropical marine habitats. In this announcement, we present the isolation and the draft genome sequence of Salinispora sp. strain H7-4 of a new 16S rDNA phylotype from deep-sea sediments of the Shikoku Basin.

Salinispora spp. are obligate marine actinomycetes reported mainly from shallow tropical and subtropical marine habitats. In this announcement, we present the isolation and draft genome sequence of Salinispora sp. strain H7-4 of a new 16S rDNA phylotype from deep-sea sediments of the Shikoku Basin.

Diversity and Bioactive Potential of Actinobacteria Isolated from a Coastal Marine Sediment in Northern Portugal

Natural compounds have had increasing applications in the biotechnological sector, with a large fraction of these substances being channeled to the pharmaceutical industry due to their important pharmacological properties. The discovery of new bioactive molecules with novel mechanisms of action constitutes a promising solution for the design of alternative therapeutic solutions. Actinobacteria are a large group of morphologically and physiologically diverse bacteria well known for their production of biotechnologically relevant compounds. The Portuguese coast is scantly explored in terms of Actinobacteria diversity and respective bioactive potential, offering a good opportunity to find new Actinobacteria taxa and bioactive natural products. In this study, we investigated the Actinobacteria diversity associated with a sediment sample collected from the intertidal zone of a beach in northern Portugal, through a cultivation-dependent approach, and screened its antimicrobial and cytotoxic potential. A total of 52 Actinobacteria strains were recovered from the marine sediment, with the largest fraction of the isolates belonging to the genus Micromonospora. Bioactivity screening assays identified crude extracts of six Streptomyces strains active against C. albicans, exhibiting minimum inhibition concentration (MIC) values in the range of 3.90-125 μg mL^-1. Twenty-five Actinobacteria crude extracts (obtained from strains of the genera Micromonospora, Streptomyces and Actinomadura) exhibited significant effects on the viability of at least one tested cancer cell line (breast ductal carcinoma T-47D and liver hepatocellular carcinoma HepG2). The Actinobacteria extracts demonstrating activity in the antimicrobial and/or cytotoxic assays were subjected to metabolomic analysis (Mass spectrometry (MS)-based dereplication and molecular networking analyses), indicating the presence of four clusters that may represent new natural products. The results obtained demonstrate the importance of bioprospecting underexplored environments, like the Portuguese coast, for enhancing the discovery of new natural products, and call attention to the relevance of preserving the natural genetic diversity of coastal environments.

Six novel species of the obligate marine actinobacterium Salinispora, Salinispora cortesiana sp. nov., Salinispora fenicalii sp. nov., Salinispora goodfellowii sp. nov., Salinispora mooreana sp. nov., Salinispora oceanensis sp. nov. and Salinispora vitiensis sp. nov., and emended description of the genus Salinispora

Ten representative actinobacterial strains isolated from marine sediments collected worldwide were studied to determine their taxonomic status. The strains were previously identified as members of the genus Salinispora and shared >99 % 16S rRNA gene sequence similarity to the three currently recognized Salinispora species. Comparative genomic analyses resulted in the delineation of six new species based on average nucleotide identity and digital DNA-DNA hybridization values below 95 and 70 %, respectively. The species status of the six new groups was supported by a core-genome phylogeny reconstructed from 2106 orthologs detected in 118 publicly available Salinispora genomes. Chemotaxonomic and physiological studies were used to complete the phenotypic characterization of the strains. The fatty acid profiles contained the major components iso-C_16 : 0, C_15 : 0, iso-_17 : 0 and anteiso C_17 : 0. Galactose and xylose were common in all whole-sugar patterns but differences were found between the six groups of strains. Polar lipid compositions were also unique for each species. Distinguishable physiological and biochemical characteristics were also recorded. The names proposed are Salinispora cortesiana sp. nov., CNY-202^T (=DSM 108615^T=CECT 9739^T); Salinispora fenicalii sp. nov., CNT-569^T (=DSM 108614^T=CECT 9740^T); Salinispora goodfellowii sp. nov., CNY-666^T (=DSM 108616^T=CECT 9738^T); Salinispora mooreana sp. nov., CNT-150^T (=DSM 45549^T=CECT 9741^T); Salinispora oceanensis sp. nov., CNT-138^T (=DSM 45547^T=CECT 9742^T); and Salinispora vitiensis sp. nov., CNT-148^T (=DSM 45548^T=CECT 9743^T).

Microbiota composition of captive bluestreak cleaner wrasse Labroides dimidiatus (Valenciennes, 1839)

The Labroides dimidiatus is one of the most traded marine ornamental fishes worldwide, yet not much is known about the microflora associated with this fish. This study is designed to investigate the bacteria composition associated with captive L. dimidiatus and its surrounding aquarium water. The fish and carriage water were obtained from well-known ornamental fish suppliers in Terengganu Malaysia. Bacteria present on the skin and in the stomach and the aquarium water were enumerated using culture-independent approaches and next-generation sequencing (NGS) technology. A total of 3,238,564 valid reads and 828 total operational taxonomic units (OTUs) were obtained from the three metagenomic libraries using NGS analysis. Of all the 15 phyla identified in this study, Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria were the most prevalent in all samples. Also, 170 families belonging to 36 bacteria classes were identified. Although many of the bacteria families were common in the skin, gut, and aquarium water (39%), about 26% of the families were exclusive to the aquarium water alone. Therefore, any substantial change in the structure and abundance of microbiota (especially pathogenic bacteria) reported in this study may serve as an early sign for disease infection in the species under captivity. KEY POINTS: • Proteobacteria was the most dominant. • The microbiota was either shared or exclusively in samples.

Addition of insoluble fiber to isolation media allows for increased metabolite diversity of lab-cultivable microbes derived from zebrafish gut samples

There is a gap in measured microbial diversity when comparing genomic sequencing techniques versus cultivation from environmental samples in a laboratory setting. Standardized methods in artificial environments may not recapitulate the environmental conditions that native microbes require for optimal growth. For example, the intestinal tract houses microbes at various pH values as well as minimal oxygen and light environments. These microbes are also exposed to an atypical source of carbon: dietary fiber compacted in fecal matter. To investigate how the addition of insoluble fiber to isolation media could affect the cultivation of microbes from zebrafish intestines, an isolate library was built and analyzed using the bioinformatics pipeline IDBac. While all isolation media encouraged the growth of species from several phyla, the extent of growth was greater with the addition of fiber allowing for easier isolation. Furthermore, fiber addition altered the metabolism of the cultivated gut-derived microbes and induced the production of unique metabolites that were not produced when microbes were otherwise grown on standard isolation media. Addition of this inexpensive carbon source to the media supported the cultivation of a diverse community whose secondary metabolite production may more closely replicate their metabolite production in vivo.

Bacillus caeni sp. nov., isolated from mangrove sediment

A Gram-variable, aerobic, motile and irregular rod-shaped bacterium, designated HB172195^T, was isolated from a mangrove sediment sample collected from Bamen Bay mangrove forest, China. Cells of the strain were oxidase-negative but positive for catalase and nitrate reduction. Strain HB172195^T was found to grow at 15-50 °C (optimum, 25-40 °C), pH 5.0-9.0 (optimum, pH 7.0) and in 1.0-11.0 % (w/v) NaCl (optimum, 3-6 %). Chemotaxonomic analysis indicated that the sole respiratory quinone was MK-7 and the cell-wall peptidoglycan was meso-diaminopimelic acid. The predominant cellular fatty acids were anteiso-C_{15 : 0}, anteiso-C_{17 : 0} and C_{16 : 1}ω7c alcohol. The major polar lipids consisted of phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol and an unidentified phospholipid. The genomic DNA G+C content was 40.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain was closely related to Bacillus hwajinpoensis SW-72^T (96.3%), Bacillus algicola KMM 3737^T (96.2 %) and Bacillus haemicentroti JSM 076093^T (95.5 %). Based on polyphasic taxonomic characterization, strain HB172195^T is considered to represent a novel species, for which the name Bacillus caeni sp. nov. is proposed. The type strain is HB172195^T (=CGMCC 1.16730^T=JCM 33411^T).

Anthracycline Shunt Metabolites From Philippine Marine Sediment-Derived Streptomyces Destroy Cell Membrane Integrity of Multidrug-Resistant Staphylococcus aureus

The rise of antibiotic resistance (ABR) and the drying up of the pipeline for the development of new antibiotics demands an urgent search for new antibiotic leads. While the majority of clinically available antibiotics were discovered from terrestrial Streptomyces, related species from marine sediments as a source of antibiotics remain underexplored. Here, we utilized culture-dependent isolation of thirty-five marine sediment-derived actinobacterial isolates followed by a screening of their antibacterial activity against multidrug-resistant S. aureus ATCC BAA-44. Our results revealed that the crude extract of Streptomyces griseorubens strain DSD069 isolated from marine sediments collected in Romblon, Philippines displays the highest antibacterial activity, with 96.4% growth inhibition. The S. aureus ATCC BAA-44 cells treated with crude extract of Streptomyces griseorubens strain DSD069 showed cell membrane damage as demonstrated by (a) leakage and loss of vital cell constituents, including DNA and proteins, (b) irregular shrinkage of cells, and (c) increase membrane permeability. The antibiotic compounds were identified as Bisanhydroaklavinone and 1-Hydroxybisanhydroaklavinone with MIC value of 6.25 μg/mL and 50.00 μg/mL, respectively. Bisanhydroaklavinone and 1-Hydroxybisanhydroaklavinone are shunt metabolites in the biosynthesis of anticancer anthracycline derivatives namely doxorubicin, daunorubicin, and cinerubins. It is rare, however, that shunt metabolites are accumulated during fermentation of marine sediment-derived Streptomyces strain without genetic modification. Thus, our study provides evidence that natural bacterial strain can produce Bisanhydroaklavinone and 1-Hydroxybisanhydroaklavinone as antibiotic leads to combat ABR.

Metabolomic Diversity and Identification of Antibacterial Activities of Bacteria Isolated From Marine Sediments in Hawai'i and Puerto Rico

Antibiotic resistance is a growing concern worldwide and consequently metabolomic tools are being applied increasingly in efforts aimed at identifying new antimicrobial compounds. Marine bacteria-derived compounds have shown great promise in this area. A metabolomics-based study was undertaken to study the diversity of secondary metabolites from marine sediment bacteria isolated from different locations of Hawai’i and Puerto Rico. This effort included characterizing the biodiversity in the sediment samples and searching for antibacterial activity and associated compounds. Bacterial strains were isolated using several different nutrient agars and culture conditions. DNA sequencing (16s rDNA) was used for phylogenetic characterization. Antibacterial activity was assessed against antibiotic-resistant strains of Escherichia coli, Salmonella enterica, Acinetobacter baumannii, Staphylococcus aureus, and Enterococcus faecalis. Ethyl acetate extracted bacterial secondary metabolites were measured by ultra-performance liquid chromatography-mass spectrometry, processed in Progenesis QI and further analyzed by partial least squares-discriminant analysis using MetaboAnalyst 3. Among the strains (n = 143) that were isolated from these two geographical areas and tested for antibiotic activity, 19 exhibited antibacterial activity against at least one antibiotic-resistant human pathogen. One strain from Hawai’i possessed broad-spectrum activity against all five pathogens. Metabolite profiles were diverse and separated the strains into two clusters in PCA analysis that mirrored geographical origin of the isolated strains. A diversity of bacteria and potential antibacterial compounds were observed in this study. Marine environments represent an opportunity to discover a rich diversity of antibacterial compounds for which resistance mechanisms may be uncommon in human pathogens.

Isolation and characterization of bioactive compounds with antibacterial, antioxidant and enzyme inhibitory activities from marine-derived rare actinobacteria, Nocardiopsis sp. SCA21

A rare actinobacteria strain designated SCA21, producing bioactive metabolites was isolated from marine sediment of Havelock Island, Andaman and Nicobar Islands, India. Analysis of 16S rRNA sequences suggested that the strain SCA21 belonged to the genus Nocardiopsis. Chemical investigation of the fermentation broth led to the isolation of two pure bioactive compounds (1-2). Compound 1: 4-bromophenol, a bromophenol derivative; Compound 2: Bis (2-ethylhexyl) phthalate, a phthalate ester. The structure of compound 1 and 2 were elucidated by the detailed analysis of FT-IR, HR-ESI-MS, 1D and 2D NMR, along with literature data analysis. The isolated metabolites were evaluated for enzyme inhibition activity against α-glucosidase and α-amylase, free radical scavenging activity against DPPH and ABTS radicals, metal chelating and antibacterial activity against clinical pathogens. 1 and 2 exhibited remarkable enzyme inhibitory activities against α-glucosidase. However, Compound 2 was found less active against α-amylase. They showed significant free radical scavenging activity against DPPH and ABTS radicals. In addition, except the strain Salmonella typhi ATCC 25241 and Listeria cytogens ATCC 13932, 1 and 2 showed broad spectrum inhibitory activity against MRSA ATCC NR-46171, MRSA ATCC-46071, Klebsiella pneumonia ATCC 13883, Bacillus subtilis ATCC 6633, Staphylococcus aureus ATCC 12600. In conclusion, to best of our knowledge these findings are the first report of isolation of 4-bromophenol and Bis (2-ethylhexyl) phthalate from genus Nocardiopsis, thus suggesting that rare actinomycetes are promising source of therapeutically important bioactive metabolites.

Phylogenetic Analysis and Screening of Antimicrobial and Antiproliferative Activities of Culturable Bacteria Associated with the Ascidian Styela clava from the Yellow Sea, China

Over 1,000 compounds, including ecteinascidin-743 and didemnin B, have been isolated from ascidians, with most having bioactive properties such as antimicrobial, antitumor, and enzyme-inhibiting activities. In recent years, direct and indirect evidence has shown that some bioactive compounds isolated from ascidians are not produced by ascidians themselves but by their symbiotic microorganisms. Isolated culturable bacteria associated with ascidians and investigating their potential bioactivity are an important approach for discovering novel compounds. In this study, a total of 269 bacteria were isolated from the ascidian Styela clava collected from the coast of Weihai in the north of the Yellow Sea, China. Phylogenetic relationships among 183 isolates were determined using their 16S rRNA gene sequences. Isolates were tested for antimicrobial activity against seven indicator strains, and an antiproliferative activity assay was performed to test for inhibition of human hepatocellular carcinoma Bel 7402 and human cervical carcinoma HeLa cell proliferation. Our results showed that the isolates belonged to 26 genera from 18 families in four phyla (Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes). Bacillus and Streptomyces were the most dominant genera; 146 strains had potent antimicrobial activities and inhibited at least one of the indicator strains. Crude extracts from 29 strains showed antiproliferative activity against Bel 7402 cells with IC₅₀ values below 500 μg·mL^-1, and 53 strains showed antiproliferative activity against HeLa cells, with IC₅₀ values less than 500 μg·mL^-1. Our results suggest that culturable bacteria associated with the ascidian Styela clava may be a promising source of novel bioactive compounds.

Minimizing Taxonomic and Natural Product Redundancy in Microbial Libraries Using MALDI-TOF MS and the Bioinformatics Pipeline IDBac

Libraries of microorganisms have been a cornerstone of drug discovery efforts since the mid-1950s, but strain duplication in some libraries has resulted in unwanted natural product redundancy. In the current study, we implemented a workflow that minimizes both the natural product overlap and the total number of bacterial isolates in a library. Using a collection expedition to Iceland as an example, we purified every distinct bacterial colony off isolation plates derived from 86 environmental samples. We employed our mass spectrometry (MS)-based IDBac workflow on these isolates to form groups of taxa based on protein MS fingerprints (3-15 kDa) and further distinguished taxa subgroups based on their degree of overlap within corresponding natural product spectra (0.2-2 kDa). This informed the decision to create a library of 301 isolates spanning 54 genera. This process required only 25 h of data acquisition and 2 h of analysis. In a separate experiment, we reduced the size of an existing library based on the degree of metabolic overlap observed in natural product MS spectra of bacterial colonies (from 833 to 233 isolates, a 72.0% size reduction). Overall, our pipeline allows for a significant reduction in costs associated with library generation and minimizes natural product redundancy entering into downstream biological screening efforts.

Antibacterial Salinaphthoquinones from a Strain of the Bacterium Salinispora arenicola Recovered from the Marine Sediments of St. Peter and St. Paul Archipelago, Brazil

Salinaphthoquinones A-E (1-5) were isolated from a marine Salininispora arenicola strain, recovered from sediments of the St. Peter and St. Paul Archipelago, Brazil. The structures of the compounds were elucidated using a combination of spectroscopic (NMR, IR, HRESIMS) data, including single-crystal X-ray diffraction analysis. A plausible biosynthetic pathway for 1-5 is proposed. Compounds 1 to 4 displayed moderate activity against Staphylococcus aureus and Enterococcus faecalis with MIC values of 125 to 16 μg/mL.

Extreme Environment Streptomyces: Potential Sources for New Antibacterial and Anticancer Drug Leads?

Antimicrobial resistance (AR) is recognized as one of the greatest threats to public health and in global concern. Consequently, the increased morbidity and mortality, which are associated with multidrug resistance bacteria, urgently require the discovery of novel and more efficient drugs. Conversely, cancer is a growing complex human disease that demands new drugs with no or fewer side effects. Most of the drugs currently used in the health care systems were of Streptomyces origin or their synthetic forms. Natural product researches from Streptomyces have been genuinely spectacular over the recent years from extreme environments. It is because of technical advances in isolation, fermentation, spectroscopy, and genomic studies which led to the efficient recovering of Streptomyces and their new chemical compounds with distinct activities. Expanding the use of the last line of antibiotics and demand for new drugs will continue to play an essential role for the potent Streptomyces from previously unexplored environmental sources. In this context, deep-sea, desert, cryo, and volcanic environments have proven to be a unique habitat of more extreme, and of their adaptation to extreme living, environments attribute to novel antibiotics. Extreme Streptomyces have been an excellent source of a new class of compounds which include alkaloids, angucycline, macrolide, and peptides. This review covers novel drug leads with antibacterial and cytotoxic activities isolated from deep-sea, desert, cryo, and volcanic environment Streptomyces from 2009 to 2019. The structure and chemical classes of the compounds, their relevant bioactivities, and the sources of organisms are presented.

Antimicrobial potential of Streptomyces sp. to the Gram positive and Gram negative pathogens

BACKGROUND

The occurrence of drug resistant infectious disease causing microbial pathogens was highly spreaded because of the wide level application of the commercially available antimicrobial agents. However, the eradication of the microbial pathogens was of huge demand. Although, many antimicrobial compounds were commercially available in the market however the spreading of the pathogens were hugely increased. Actinomycetes produce various secondary metabolites against pathogenic bacteria and fungi. The present investigation aimed to study the antimicrobial potential of the Streptomyces sp. towards infectious diseases causing pathogens.

METHODS

Culture dependable isolation techniques were followed for the isolation of the active actinomycetes isolates and the antimicrobial properties of the actinomcyetes were detected by primary screening techniques using modified starch casein agar medium. The active isolate was confirmed by various biochemical and morphological techniques.

RESULTS

In this study, 10 actinomycetes were isolated and later five were selected for secondary screening and noted significant activity against Enterobacter aerogenes and Proteus mirabilis. Among the selected Streptomyces sp., ES2 showed potent activity against selected microbes and was identified as Streptomyces sp. The studied isolates were resisitant towards streptomycin (10μg), ampicillin (50μg) and ciprofloxacin (5μg). The organic solvent extracts of the promising isolate ES2 prononunced comparatively better inhibitory properties towards the studied pathogenic bacteria.

CONCLUSION

Overall, the present study evidenced that the actinomycetes were promising candidate for the eradication of the pathogenic strains.

Marine Rare Actinomycetes: A Promising Source of Structurally Diverse and Unique Novel Natural Products

Rare actinomycetes are prolific in the marine environment; however, knowledge about their diversity, distribution and biochemistry is limited. Marine rare actinomycetes represent a rather untapped source of chemically diverse secondary metabolites and novel bioactive compounds. In this review, we aim to summarize the present knowledge on the isolation, diversity, distribution and natural product discovery of marine rare actinomycetes reported from mid-2013 to 2017. A total of 97 new species, representing 9 novel genera and belonging to 27 families of marine rare actinomycetes have been reported, with the highest numbers of novel isolates from the families Pseudonocardiaceae, Demequinaceae, Micromonosporaceae and Nocardioidaceae. Additionally, this study reviewed 167 new bioactive compounds produced by 58 different rare actinomycete species representing 24 genera. Most of the compounds produced by the marine rare actinomycetes present antibacterial, antifungal, antiparasitic, anticancer or antimalarial activities. The highest numbers of natural products were derived from the genera Nocardiopsis, Micromonospora, Salinispora and Pseudonocardia. Members of the genus Micromonospora were revealed to be the richest source of chemically diverse and unique bioactive natural products.

Naphthomycin-derived macrolactams with two new carbon skeletons from endophytic Streptomyces

A cytotoxic ansamycin class of natural products with two new carbon skeletons was isolated and characterized from endophytic Streptomyces.

Eyes in the sea: Unlocking the mysteries of the ocean using industrial, remotely operated vehicles (ROVs)

For thousands of years humankind has sought to explore our oceans. Evidence of this early intrigue dates back to 130,000BCE, but the advent of remotely operated vehicles (ROVs) in the 1950s introduced technology that has had significant impact on ocean exploration. Today, ROVs play a critical role in both military (e.g. retrieving torpedoes and mines) and salvage operations (e.g. locating historic shipwrecks such as the RMS Titanic), and are crucial for oil and gas (O&G) exploration and operations. Industrial ROVs collect millions of observations of our oceans each year, fueling scientific discoveries. Herein, we assembled a group of international ROV experts from both academia and industry to reflect on these discoveries and, more importantly, to identify key questions relating to our oceans that can be supported using industry ROVs. From a long list, we narrowed down to the 10 most important questions in ocean science that we feel can be supported (whole or in part) by increasing access to industry ROVs, and collaborations with the companies that use them. The questions covered opportunity (e.g. what is the resource value of the oceans?) to the impacts of global change (e.g. which marine ecosystems are most sensitive to anthropogenic impact?). Looking ahead, we provide recommendations for how data collected by ROVs can be maximised by higher levels of collaboration between academia and industry, resulting in win-win outcomes. What is clear from this work is that the potential of industrial ROV technology in unravelling the mysteries of our oceans is only just beginning to be realised. This is particularly important as the oceans are subject to increasing impacts from global change and industrial exploitation. The coming decades will represent an important time for scientists to partner with industry that use ROVs in order to make the most of these 'eyes in the sea'.

Engineering Salinispora tropica for heterologous expression of natural product biosynthetic gene clusters

The marine actinomycete genus Salinispora is a remarkably prolific source of structurally diverse and biologically active secondary metabolites. Herein, we select the model organism Salinispora tropica CNB-440 for development as a heterologous host for the expression of biosynthetic gene clusters (BGCs) to complement well-established Streptomyces host strains. In order to create an integratable host with a clean background of secondary metabolism, we replaced three genes (salA-C) essential for salinosporamide biosynthesis with a cassette containing the Streptomyces coelicolor ΦC31 phage attachment site attB to generate the mutant S. tropica CNB-4401 via double-crossover recombination. This mutagenesis not only knocks-in the attachment site attB in the genome of S. tropica CNB-440 but also abolishes production of the salinosporamides, thereby simplifying the strain's chemical background. We validated this new heterologous host with the successful integration and expression of the thiolactomycin BGC that we recently identified in several S. pacifica strains. When compared to the extensively engineered superhost S. coelicolor M1152, the production of thiolactomycins from S. tropica CNB-4401 was approximately 3-fold higher. To the best of our knowledge, this is the first example of using a marine actinomycete as a heterologous host for natural product BGC expression. The established heterologous host may provide a useful platform to accelerate the discovery of novel natural products and engineer biosynthetic pathways.

Antimicrobial-producing Pseudoalteromonas from the marine environment of Panama shows a high phylogenetic diversity and clonal structure

Pseudoalteromonas is a genus of marine bacteria often found in association with other organisms. Although several studies have examined Pseudoalteromonas diversity and their antimicrobial activity, its diversity in tropical environments is largely unexplored. We investigated the diversity of Pseudoalteromonas in marine environments of Panama using a multilocus phylogenetic approach. Furthermore we tested their antimicrobial capacity and evaluated the effect of recombination and mutation in shaping their phylogenetic relationships. The reconstruction of clonal relationships among 78 strains including 15 reference Pseudoalteromonas species revealed 43 clonal lineages, divided in pigmented and non-pigmented strains. In total, 39 strains displayed moderate to high activity against Gram-positive and Gram-negative bacteria and fungi. Linkage disequilibrium analyses showed that the Pseudoalteromonas strains of Panama have a highly clonal structure and that, although present, recombination is not frequent enough to break the association among alleles. This clonal structure is in contrast to the high rates of recombination generally reported for aquatic and marine bacteria. We propose that this structure is likely due to the symbiotic association with marine invertebrates of most strains analyzed. Our results also show that there are several putative new species of Pseudoalteromonas in Panama to be described.

Characterization and partial purification of an antibacterial agent from halophilic actinomycetes Kocuria sp. strain rsk4

Introduction: The inevitable rise of antibiotic-resistant bacteria is a global health problem. These pathogens erode the utility of available antibiotics. Staphylococcus aureus is one of the major causes of community-acquired infections. The aim of work was to evaluate the marine actinomycetes for production of the antibacterial agent against pathogens.

Methods: Halophilic actinomycetes were isolated, characterized and screened for production of antibacterial agent against pathogenic bacteria. The antibacterial compounds were extracted by solvent extraction and separated by TLC based bioautography. Antibacterial compound was further purified by flash chromatography followed by high-performance liquid chromatography (HPLC) techniques. The active fraction was characterized by spectroscopy techniques. The minimum inhibitory concentration of antibiotic was determined against pathogens.

Results: A new halophilic actinomycetes strain rsk4 was isolated from marine water. It was designated as Kocuria sp. based on the physiological, biochemical and 16S rDNA sequencebased characters. It was able to produce broad-spectrum antibacterial compound and exhibited significant inhibitory activities against antibiotic-resistant S. aureus. The antibacterial compound was secreted optimally at 5% NaCl and neutral pH in the starch casein medium during stationary phase. The crude ethyl acetate extract was separated by chloroform-methanol, 24:1, v/v having Rf value 0.45. Bioassay of HPLC fractions confirms the presence of antibiotics picks at retention time: 3.24 minutes. The UV-Visible and mass spectra of the compound revealed that the active compound was different from other known antibiotics. The lowest minimum inhibitory concentration was recorded against S. aureus (30 µg/mL).

Conclusion: The result suggests that a broad-spectrum antibacterial compound obtained from halophilic actinomycetes is effective against pathogenic bacteria. This compound may be a good alternative treatment against antibiotic-resistant pathogen S. aureus.