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1.
Modelling the marine eutrophication: A review.
Ménesguen, A, Lacroix, G
The Science of the total environment. 2018;:339-354
Abstract
In the frame of a national, joint scientific appraisal, 45 scientific French-speaking experts have been mandated in 2015-2016 by the French ministries of Environment and Agriculture to perform a global review of scientific literature dealing with the eutrophication phenomenon, in freshwater as well as in marine waters. This paper summarizes the main results of this review restricted to a sub-domain, the modelling approach of the marine eutrophication. After recalling the different aims pursued, an overview is given on the historical time course of this modelling effort, its world distribution and the various tools used. Then, the main results obtained are examined, highlighting the specific strengths and weaknesses of the present models. Needs for future improvement are then listed.
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2.
Genome-Guided Identification of Organohalide-Respiring Deltaproteobacteria from the Marine Environment.
Liu, J, Häggblom, MM
mBio. 2018;(6)
Abstract
Organohalide compounds are widespread in the environment as a result of both anthropogenic activities and natural production. The marine environment, in particular, is a major reservoir of organohalides, and reductive dehalogenation is thought to be an important process in the overall cycling of these compounds. Deltaproteobacteria are important members of the marine microbiota with diverse metabolic capacities, and reductive dehalogenation has been observed in some Deltaproteobacteria In this study, a comprehensive survey of Deltaproteobacteria genomes revealed that approximately 10% contain reductive dehalogenase (RDase) genes, which are found within a common gene neighborhood. The dehalogenating potential of select RDase A-containing Deltaproteobacteria and their gene expression were experimentally verified. Three Deltaproteobacteria strains isolated from marine environments representing diverse species, Halodesulfovibrio marinisediminis, Desulfuromusa kysingii, and Desulfovibrio bizertensis, were shown to reductively dehalogenate bromophenols and utilize them as terminal electron acceptors in organohalide respiration. Their debrominating activity was not inhibited by sulfate or elemental sulfur, and these species are either sulfate- or sulfur-reducing bacteria. The analysis of RDase A gene transcripts indicated significant upregulation induced by 2,6-dibromophenol. This study extends our knowledge of the phylogenetic diversity of organohalide-respiring bacteria and their functional RDase A gene diversity. The identification of reductive dehalogenase genes in diverse Deltaproteobacteria and confirmation of their organohalide-respiring capability suggest that Deltaproteobacteria play an important role in natural organohalide cycling.IMPORTANCE The marine environment is a major reservoir for both anthropogenic and natural organohalides, and reductive dehalogenation is thought to be an important process in the overall cycling of these compounds. Here we demonstrate that the capacity of organohalide respiration appears to be widely distributed in members of marine Deltaproteobacteria The identification of reductive dehalogenase genes in diverse Deltaproteobacteria and the confirmation of their dehalogenating activity through functional assays and transcript analysis in select isolates extend our knowledge of organohalide-respiring Deltaproteobacteria diversity. The presence of functional reductive dehalogenase genes in diverse Deltaproteobacteria implies that they may play an important role in organohalide respiration in the environment.
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3.
Microbial ecology of deep-sea hypersaline anoxic basins.
Merlino, G, Barozzi, A, Michoud, G, Ngugi, DK, Daffonchio, D
FEMS microbiology ecology. 2018;(7)
Abstract
Deep hypersaline anoxic basins (DHABs) are unique water bodies occurring within fractures at the bottom of the sea, where the dissolution of anciently buried evaporites created dense anoxic brines that are separated by a chemocline/pycnocline from the overlying oxygenated deep-seawater column. DHABs have been described in the Gulf of Mexico, the Mediterranean Sea, the Black Sea and the Red Sea. They are characterized by prolonged historical separation of the brines from the upper water column due to lack of mixing and by extreme conditions of salinity, anoxia, and relatively high hydrostatic pressure and temperatures. Due to these combined selection factors, unique microbial assemblages thrive in these polyextreme ecosystems. The topological localization of the different taxa in the brine-seawater transition zone coupled with the metabolic interactions and niche adaptations determine the metabolic functioning and biogeochemistry of DHABs. In particular, inherent metabolic strategies accompanied by genetic adaptations have provided insights on how prokaryotic communities can adapt to salt-saturated conditions. Here, we review the current knowledge of the diversity, genomics, metabolisms and ecology of prokaryotes in DHABs.
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4.
Fengycins, Cyclic Lipopeptides from Marine Bacillus subtilis Strains, Kill the Plant-Pathogenic Fungus Magnaporthe grisea by Inducing Reactive Oxygen Species Production and Chromatin Condensation.
Zhang, L, Sun, C
Applied and environmental microbiology. 2018;(18)
Abstract
Rice blast caused by the phytopathogen Magnaporthe grisea poses a serious threat to global food security and is difficult to control. Bacillus species have been extensively explored for the biological control of many fungal diseases. In the present study, the marine bacterium Bacillus subtilis BS155 showed a strong antifungal activity against M. grisea The active metabolites were isolated and identified as cyclic lipopeptides (CLPs) of the fengycin family, named fengycin BS155, by the combination of high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS/MS). Analyses using scanning and transmission electron microscopy revealed that fengycin BS155 caused morphological changes in the plasma membrane and cell wall of M. grisea hyphae. Using comparative proteomic and biochemical assays, fengycin BS155 was demonstrated to reduce the mitochondrial membrane potential (MMP), induce bursts of reactive oxygen species (ROS), and downregulate the expression level of ROS-scavenging enzymes. Simultaneously, fengycin BS155 caused chromatin condensation in fungal hyphal cells, which led to the upregulation of DNA repair-related protein expression and the cleavage of poly(ADP-ribose) polymerase (PARP). Altogether, our results indicate that fengycin BS155 acts by inducing membrane damage and dysfunction of organelles, disrupting MMP, oxidative stress, and chromatin condensation, resulting in M. grisea hyphal cell death. Therefore, fengycin BS155 and its parent bacterium are very promising candidates for the biological control of M. grisea and the associated rice blast and should be further investigated as such.IMPORTANCE Rice (Oryza sativa L.) is the most important crop and a primary food source for more than half of the world's population. Notably, scientists in China have developed several types of rice that can be grown in seawater, avoiding the use of precious freshwater resources and potentially creating enough food for 200 million people. The plant-affecting fungus Magnaporthe grisea is the causal agent of rice blast disease, and biological rather than chemical control of this threatening disease is highly desirable. In this work, we discovered fengycin BS155, a cyclic lipopeptide material produced by the marine bacterium Bacillus subtilis BS155, which showed strong activity against M. grisea Our results elucidate the mechanism of fengycin BS155-mediated M. grisea growth inhibition and highlight the potential of B. subtilis BS155 as a biocontrol agent against M. grisea in rice cultivation under both fresh- and saltwater conditions.
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5.
Strains of the toxic and bloom-forming Nodularia spumigena (cyanobacteria) can degrade methylphosphonate and release methane.
Teikari, JE, Fewer, DP, Shrestha, R, Hou, S, Leikoski, N, Mäkelä, M, Simojoki, A, Hess, WR, Sivonen, K
The ISME journal. 2018;(6):1619-1630
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Abstract
Nodularia spumigena is a nitrogen-fixing cyanobacterium that forms toxic blooms in the Baltic Sea each summer and the availability of phosphorous is an important factor limiting the formation of these blooms. Bioinformatic analysis identified a phosphonate degrading (phn) gene cluster in the genome of N. spumigena suggesting that this bacterium may use phosphonates as a phosphorus source. Our results show that strains of N. spumigena could grow in medium containing methylphosphonic acid (MPn) as the sole source of phosphorous and released methane when growing in medium containing MPn. We analyzed the total transcriptomes of N. spumigena UHCC 0039 grown using MPn and compared them with cultures growing in Pi-replete medium. The phnJ, phosphonate lyase gene, was upregulated when MPn was the sole source of phosphorus, suggesting that the expression of this gene could be used to indicate the presence of bioavailable phosphonates. Otherwise, growth on MPn resulted in only a minor reconstruction of the transcriptome and enabled good growth. However, N. spumigena strains were not able to utilize any of the anthropogenic phosphonates tested. The phosphonate utilizing pathway may offer N. spumigena a competitive advantage in the Pi-limited cyanobacterial blooms of the Baltic Sea.
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6.
Muricauda iocasae sp. nov., isolated from deep sea sediment of the South China Sea.
Liu, SQ, Sun, QL, Sun, YY, Yu, C, Sun, L
International journal of systematic and evolutionary microbiology. 2018;(8):2538-2544
Abstract
In this study, we reported a novel yellow-pigmented, Gram-stain-negative bacterium with appendages, designated as strain L2T, isolated from the South China Sea. Growth of strain L2T occurred at 22-40 °C (optimum, 37 °C), pH 6.0-10.0 (pH 7.0) and with 0-8 % (w/v) NaCl (2 %). Phylogenetic analysis based on its 16S rRNA gene sequence indicated that strain L2T belonged to the genus Muricauda. The close phylogenetic neighbours of strain L2T were Muricauda marina H19-56T, Muricauda ruestringensis B1T, Muricauda antarctica Ar-22T, Muricauda taeanensis 105T and Muricauda flavescens SW-62T (96.4 %, 95.9 %, 95.9 %, 95.8 % and 94.5 % identities, respectively). The genomic DNA G+C content of strain L2T was 51.3±4.6 mol%. Theg major isoprenoid quinone was MK-6 (100.0 %). The polar lipids contained phosphatidylethanolamine and two unidentified lipids. The major fatty acids (>10 % of total fatty acids) were iso-C17 : 0 3-OH (30.3 %), iso-C15 : 1 G (20.6 %) and iso-C15 : 0 (17.6 %). Phylogenetic, physiological, biochemical and morphological analysis suggested that this strain represents a novel species of genus Muricauda, and the name Muricauda iocasae sp. nov. is proposed with the type species L2T (=CCTCC AB 2017193 T=KCTC 62196T).
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7.
Alteromonas oceani sp. nov., isolated from deep-sea sediment of a hydrothermal field.
Jin, QW, Hu, YH, Sun, L
International journal of systematic and evolutionary microbiology. 2018;(2):657-662
Abstract
A novel rod-shaped, Gram-stain-negative, aerobic bacterium, designated S35T, was isolated from deep-sea sediment collected from the Pacmanus hydrothermal field, Manus Basin, Papua New Guinea. Strain S35T grew optimally at 28 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. 16S rRNA gene sequence analysis indicated that strain S35T shared 97.38-98.55% similarity with the type strains of Alteromonas lipolytica, Alteromonas mediterranea and Aestuariibacterhalophilus. Phylogenetic analysis showed that strain S35T belonged to the genus Alteromonas. The strain contained ubiquinone-8 as the predominant respiratory lipoquinone. Summed feature 3 (C16 : 1ω7c and/or C16 : 1ω7c), summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c) and C16 : 0 were the major fatty acids. The DNA G+C content of strain S35T was 51.3 mol%. These results indicated that strain S35T represents a novel species of the genus Alteromonas, for which the name Alteromonas oceani sp. nov. (type strain S35T=KCTC 52449T=CGMCC 1.16029T) is proposed.
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8.
Iron-oxidizing bacteria in marine environments: recent progresses and future directions.
Makita, H
World journal of microbiology & biotechnology. 2018;(8):110
Abstract
Iron-oxidizing bacteria (FeOB) refers to a group of bacteria with the ability to exchange and accumulate divalent iron dissolved in water as trivalent iron inside and outside the bacterial cell. Most FeOB belong the largest bacterial phylum, Proteobacteria. Within this phylum, FeOB with varying physiology with regards to their response to oxygen (obligate aerobes, facultative and obligate anaerobes) and pH optimum for proliferation (neutrophiles, moderate and extreme acidophiles) can be found. Although FeOB have been reported from a wide variety of environments, most of them have not been isolated and their biochemical characteristics remain largely unknown. This is especially true for those living in the marine realm, where the properties of FeOB was not known until the isolation of the Zetaproteobacteria Mariprofundus ferrooxydans, first reported in 2007. Since the proposal of Zetaproteobacteria by Emerson et al., the detection and isolation of those microorganisms from the marine environment has greatly escalated. Furthermore, FeOB have also recently been reported from works on ocean drilling and metal corrosion. This review aims to summarize the current state of phylogenetic and physiological diversity in marine FeOB, the significance of their roles in their environments (on both global and local scales), as well as their growing importance and applications in the industry.
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9.
Vibrio vulnificus infection: a persistent threat to public health.
Yun, NR, Kim, DM
The Korean journal of internal medicine. 2018;(6):1070-1078
Abstract
Vibrio vulnificus is a gram-negative bacterium that can cause serious, potentially fatal infections. V. vulnificus causes three distinct syndromes: an overwhelming primary septicemia caused by consuming contaminated seafood, wound infections acquired when an open wound is exposed to contaminated warm seawater, and gastrointestinal tract-limited infections. Case-fatality rates are higher than 50% for primary septicemia, and death typically occurs within 72 hours of hospitalization. Risk factors for V. vulnificus infection include chronic liver disease, alcoholism, and hematological disorders. When V. vulnificus infection is suspected, appropriate antibiotic treatment and surgical interventions should be performed immediately. Third-generation cephalosporin with doxycycline, or quinolone with or without third-generation cephalosporin, may be potential treatment options for patients with V. vulnificus infection.
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10.
The Use of a Sea Salt-based Spray for Diabetic Foot Ulcers: A Novel Concept.
Pougatsch, DA, Rader, A, Rogers, LC
Wounds : a compendium of clinical research and practice. 2017;(2):E5-E9
Abstract
Several patients present to wound healing specialists seeking a natural or alternative medical approach to their wounds. The purpose of this prospective, case-cohort study of 10 patients was to evaluate the use of Oceanzyme Wound Care Spray (Ocean Aid, Inc, Boynton Beach, FL) in improving healing in diabetic foot ulcers during a 12-week period. This product contains water purified by reverse osmosis, coral reef sea salt, lysozyme, and sodium benzoate. The primary endpoint was wound closure, and secondary endpoints were infection rate and wound area reduction. Overall, 2 patients healed, 2 withdrew, and the remaining 6 had an average of 73% reduction in wound area. While more study is needed, the use of this sea salt-based spray may provide a viable alternative for patients seeking a natural therapy for their wound care.