Cytotoxicity of the Ascidian Cystodytes dellechiajei Against Tumor Cells and Study of the Involvement of Associated Microbiota in the Production of Cytotoxic Compounds

Many cytotoxic compounds of therapeutic interest have been isolated from marine invertebrates, and some of them have been reported to be of microbial origin. Pyridoacridine alkaloids are the main compounds extracted from the ascidian Cystodytes dellechiajei. Here we describe the in vitro antiproliferative activity against different tumor cell lines of the ascidian extracts and provide some insights on the role of the microbial community associated with the tunicate in the production of these compounds. C. dellechiajei extracts showed remarkably high antiproliferative activity (IC50 ≤5 μg/mL) in human lung carcinoma A-549, colon adenocarcinoma H-116, pancreatic adenocarcinoma PSN-1 and breast carcinoma SKBR3 cell lines. Moreover, we found that the maximum activity was located in the tunic tissue of the colony, which harbours a microbial community. In order to ascertain the involvement of this community in the synthesis of the bioactive compounds different approachs that included culture and culture independent methods were carried out. We undertook a screening for antiproliferative activities of the bacterial isolates from the ascidian, as well as a comprative analysis of the cytotoxic activities and the microbial communities from two color morphs of the ascidian, green and blue. In addition, the changes of the antiproliferative activities and the composition of the microbial communities were studied from ascidians kept in aquaria and treated with antibiotics for one month. Our data obtained from the different experiments did not point out to bacteria as the source of the cytotoxic compounds, suggesting thus an ascidian origin

Coral microbiome composition along the northern Red Sea suggests high plasticity of bacterial and specificity of endosymbiotic dinoflagellate communities

Background The capacity of reef-building corals to tolerate (or adapt to) heat stress is a key factor determining their resilience to future climate change. Changes in coral microbiome composition (particularly for microalgal endosymbionts and bacteria) is a potential mechanism that may assist corals to thrive in warm waters. The northern Red Sea experiences extreme temperatures anomalies, yet corals in this area rarely bleach suggesting possible refugia to climate change. However, the coral microbiome composition, and how it relates to the capacity to thrive in warm waters in this region, is entirely unknown. Results We investigated microbiomes for six coral species (Porites nodifera, Favia favus, Pocillopora damicornis, Seriatopora hystrix, Xenia umbellata, and Sarcophyton trocheliophorum) from five sites in the northern Red Sea spanning 4° of latitude and summer mean temperature ranges from 26.6 °C to 29.3 °C. A total of 19 distinct dinoflagellate endosymbionts were identified as belonging to three genera in the family Symbiodiniaceae (Symbiodinium, Cladocopium, and Durusdinium). Of these, 86% belonged to the genus Cladocopium, with notably five novel types (19%). The endosymbiont community showed a high degree of host-specificity despite the latitudinal gradient. In contrast, the diversity and composition of bacterial communities of the surface mucus layer (SML)—a compartment particularly sensitive to environmental change—varied significantly between sites, however for any given coral was species-specific. Conclusion The conserved endosymbiotic community suggests high physiological plasticity to support holobiont productivity across the different latitudinal regimes. Further, the presence of five novel algal endosymbionts suggests selection of certain genotypes (or genetic adaptation) within the semi-isolated Red Sea. In contrast, the dynamic composition of bacteria associated with the SML across sites may contribute to holobiont function and broaden the ecological niche. In doing so, SML bacterial communities may aid holobiont local acclimatization (or adaptation) by readily responding to changes in the host environment. Our study provides novel insight about the selective and endemic nature of coral microbiomes along the northern Red Sea refugia

Effects of grazing, phosphorus and light on the growth rates of major bacterioplankton taxa in the coastal NW Mediterranean

10 pages, 3 figures, 3 tables, supporting information https://dx.doi.org/10.1111/1758-2229.12535Estimation of growth rates is crucial to understand the ecological role of prokaryotes and their contribution to marine biogeochemical cycling. However, there are only a few estimates for individual taxa. Two top-down (grazing) and bottom-up (phosphorus (P) availability) manipulation experiments were conducted under different light regimes in the NW Mediterranean Sea. Growth rate of different phylogenetic groups, including the Bacteroidetes, Rhodobacteraceae, SAR11, Gammaproteobacteria and its subgroups Alteromonadaceae and the NOR5/OM60 clade, were estimated from changes in cell numbers. Maximal growth rates were achieved in the P-amended treatments but when comparing values between treatments (response ratios), the response to predation removal was in general larger than to P-amendment. The Alteromonadaceae displayed the highest rates in both experiments followed by the Rhodobacteraceae, but all groups largely responded to filtration and P-amendment, even the SAR11 which presented low growth rates. Comparing light and dark treatments, growth rates were on average equal or higher in the dark than in the light for all groups, except for the Rhodobacteraceae and particularly the NOR5 clade, groups that contain photoheterotrophic species. These results are useful to evaluate the potential contributions of different bacterial types to biogeochemical processes under changing environmental conditionsThis work was supported by grant REMEI (CTM2015-70340-R) from the Spanish Ministry of Economy, Industry and Competitivity. MK was supported by the Czech GA CR project 13-11281S and MSMT Project Algatech PlusPeer Reviewe

Roseobacter-Like Bacteria in Red and Mediterranean Sea Aerobic Anoxygenic Photosynthetic Populations

Bacteriochlorophyll a-containing aerobic anoxygenic phototrophs (AAnP) have been proposed to account for up to 11% of the total surface water microbial community and to potentially have great ecological importance in the world's oceans. Recently, environmental and genomic data based on analysis of the pufM gene identified the existence of α-proteobacteria as well as possible γ-like proteobacteria among AAnP in the Pacific Ocean. Here we report on analyses of environmental samples from the Red and Mediterranean Seas by using pufM as well as the bchX and bchL genes as molecular markers. The majority of photosynthesis genes retrieved from these seas were related to Roseobacter-like AAnP sequences. Furthermore, the sequence of a novel photosynthetic operon organization from an uncultured Roseobacter-like bacterial artificial chromosome retrieved from the Red Sea is described. The data show the presence of Roseobacter-like bacteria in Red and Mediterranean Sea AAnP populations in the seasons analyzed

Genome sequence of the marine photoheterotrophic bacterium erythrobacter sp. strain NAP1.

Here we report the full genome sequence of marine phototrophic bacterium Erythrobacter sp. strain NAP1. The 3.3-Mb genome contains a full set of photosynthetic genes organized in one 38.9-kb cluster; however, it does not contain genes for CO2 or N2 fixation, thereby confirming that the organism is a photoheterotroph

Distribution and Growth of Aerobic Anoxygenic Phototrophs in the Mediterranean Sea

9 pages, 6 figures, 2 tablesThe distribution of aerobic anoxygenic phototrophs (AAPs) was surveyed in various regions of the Mediterranean Sea in spring and summer. These phototrophic bacteria were present within the euphotic layer at all sampled stations. The AAP abundances increased with increasing trophic status ranging from 2.5 × 103 cells per ml in oligotrophic Eastern Mediterranean up to 90 × 103 cells per ml in the Bay of Villefranche. Aerobic anoxygenic phototrophs made up on average 1–4% of total prokaryotes in low nutrient areas, whereas in coastal and more productive stations these organisms represented 3–11% of total prokaryotes. Diel bacteriochlorophyll a decay measurements showed that AAP community in the Western Mediterranean grew rapidly, at rates from 1.13 to 1.42 day−1. The lower AAP abundances registered in the most oligotrophic waters suggest that they are relatively poor competitors under nutrient limiting conditions. Instead, AAPs appear to be metabolically active organisms, which thrive better in more eutrophic environments providing the necessary substrates to maintain high growth ratesThis research was supported by AV Cˇ R project M200200903, project Algatech (CZ.1.05/2.1.00/03.0110) and the Inst. research concepts MSM6007665808 and AV0Z50200510. The June 2007 cruise in the eastern Mediterranean Sea was carried out under the framework of the Italian project VECTOR. The Modivus cruise was funded by Spanish project CTM2005-04795/MAR to J.M. GasolPeer reviewe

Seasonal changes and diversity of aerobic anoxygenic phototrophs in the Baltic Sea

The community of aerobic anoxygenic phototrophs was investigated in the Baltic Sea using infrared epifluorescence microscopy from September 2004 to October 2005. The majority of these bacteriochlorophyll-containing organisms exhibited a specific sickle-shaped morphology, with rods or other morphotypes observed only occasionally. Aerobic anoxygenic phototrophs were observed mostly from April to September (1 to 12% of total prokaryotes), peaking in May 2005 at a concentration of up to 0.38 × 106 cells ml–1. This peak was associated with the later phase of the spring bloom. In the later months, the amount of phototrophic bacteria gradually declined until the beginning of the fall mixing, and remained low from November to March, contributing only 0 to 2% of total prokaryotes. A novel technique combining fluorescent in situ hybridization (FISH) and infrared epifluorescence microscopy indicated that the Baltic aerobic anoxygenic phototrophs were mostly Gammaproteobacteria, with a smaller fraction of Alphaproteobacteria

Marine heterotrophic bacteria synthesize non-phosphorus lipids upon phosphorus stress

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainPhosphorus (P) is an essential nutrient for life. The replacement of membrane phospholipids with non-phosphorus lipids constitutes an important strategy to allow growth on phosphate-limited environments. In the ocean, this strategy has been reported in phytoplankton, but not in heterotrophic bacteria. A phospholipase C was recently identified to be required for lipid remodelling in a soil bacterium during P-limitation. In this study we show this enzyme is widespread in bacterial taxa and frequently found in ocean metagenomes. In SAR11 and other proteobacterial isolates, this gene is frequently neighbour to a glycosyltransferase that could be involved in glycolipid biosynthesis. Experiments with marine isolates showed up-regulation of transcription of both the phospholipase C and the glycosyltransferase upon P-starvation. These results suggest that marine heterotrophic bacteria may substitute phospholipids for glycolipids to reduce their P-demand. Lipid measurements in environmental samples confirmed that indeed there is an important enrichment in glycolipids in the heterotrophic bacterial fraction under P-depleted conditions. Hence, lipid remodelling seems to be a widespread mechanism among marine microbes for surviving in the vast oligotrophic areas of the oceanPeer Reviewe