http://www.mdpi.com/journal/marinedrugs/special_issues/marine_microorganisms/ Guest Editor's Introduction Bioactive Compounds from Marine Microorganisms Marine environments are massively complex and contain diverse assemblage of life forms, which occur in environments with extreme variations in pressure, salinity, and temperature. As a result, marine microorganisms have developed unique metabolic and physiological capabilities to be able to survive in such extreme habitats that led them to produce different kind of metabolites, which could not be produced by the terrestrial microorganisms. It is now becoming evident that marine microorganisms are emerging as a significant chemical resource with novel compounds in clinical trials deriving from these micro-organisms. However, the lack of in-depth knowledge on the physiology and true nutritional requirements of marine microorganisms still hampers the development of effective isolation techniques, which in turn delays the detection of potent therapeutic agents. This special issue dedicated to “Bioactive Compounds from Marine Microorganisms” aims to place emphasis on the importance of understanding and linking the true ecological and functional roles of these microorganisms in marine environments on the route to biodiscovery. As the Guest Editor, I invite scientists working with marine bioactive compounds to report recent advances in the field (e.g. marine microbial ecology; detection and selective isolation of bioactive compound producing marine microorganisms; marine microbial physiology; fermentation and identification of bioactive compounds). I look forward to working with you towards a successful special issue of the journal Marine Drugs dedicated to marine bioactive compounds. Dr Ipek Kurtböke University of the Sunshine Coast Australia   Manuscript submission Manuscripts should be prepared according to the Instructions for Authors and submitted by e-mail to marinedrugs@mdpi.com, with copy to Guest Editor, Dr. Ipek Kurtböke (ikurtbok@usc.edu.au) and Prof. Dr. Peter Proksch (proksch@uni-duesseldorf.de). The subject title of the message should be "Manuscript for Special Issue on Bioactive Compounds from Marine Microorganisms". Deadline for article submission: 31 December 2008 http://www.mdpi.com/1660-3397/7/1/45/ D. salina is one of the recognized natural sources to produce β-carotene, and an useful model for studying the role of inhibitors and enhancers of carotenogenesis. However there is little information in D. salina regarding whether the isoprenoid substrate can be influenced by stress factors (carotenogenic) or selective inhibitors which in turn may further contribute to elucidate the early steps of carotenogenesis and biosynthesis of β-carotene. In this study,Dunaliella salina (BC02) isolated from La Salina BC Mexico, was subjected to the method of isoprenoids-β-carotene interference in order to promote the interruption or accumulation of the programmed biosynthesis of carotenoids. When Carotenogenic and non-carotenogenic cells of D. salina BC02 were grown under photoautotrophicgrowth conditions in the presence of 200 µM fosmidomycin, carotenogenesis and the synthesis of β-carotene were interrupted after two days in cultured D. salina cells. This result is an indirect consequence of the inhibition of the synthesis of isoprenoids and activity of the recombinant DXR enzyme thereby preventing the conversionof 1-deoxy-D-xylulose 5-phosphate (DXP) to 2-C-methyl-D-erythritol (MEP) and consequently interrupts the early steps of carotenogenesis in D. salina. The effect at the level of proteins and RNA was not evident. Mevinolin treated D. salina cells exhibited carotenogenesis and β-carotene levels very similar to those of control cell cultures indicating that mevinolin not pursued any indirect action in the biosynthesis of isoprenoids and had no effect at the level of the HMG-CoA reductase, the key enzyme of the Ac/MVA pathway. http://www.mdpi.com/1660-3397/7/1/45/ Tue, 10 Feb 2009 00:00:00 CET Marine Drugs 2009-02-10 7 1 Article 45 56 1660-3397 The Carotenogenesis Pathway via the Isoprenoid-β-carotene Interference Approach in a New Strain of Dunaliella salina Isolated from Baja California Mexico 2009-02-10 doi: 10.3390/md7010045 J. Paniagua-Michel Willian Capa-Robles Jorge Olmos-Soto Luis Enrique Gutierrez-Millan http://www.mdpi.com/1660-3397/6/4/620/ The water surface microlayer is still poorly explored, although it has been shown to contain a high density of metabolically active bacteria, often called bacterioneuston. Actinomycetes from the surface microlayer in the Trondheim fjord, Norway, have been isolated and characterized. A total of 217 isolates from two separate samples morphologically resembling the genus Streptomyces have been further investigated in this study. Antimicrobial assays showed that about 80% of the isolates exhibited antagonistic activity against nonfilamentous fungus, Gram-negative, and Gram-positive bacteria. Based on the macroscopic analyses and inhibition patterns from the antimicrobial assays, the sub-grouping of isolates was performed. Partial 16S rDNAs from the candidates from each subgroup were sequenced and phylogenetic analysis performed. 7 isolates with identical 16S rDNA sequences were further studied for the presence of PKS type I genes. Sequencing and phylogenetic analysis of the PKS gene fragments revealed that horizontal gene transfer between closely related species might have taken place. Identification of unique PKS genes in these isolates implies that dereplication can not be performed based solely on the 16S rDNA sequences. The results obtained in this study suggest that streptomycetes from the neuston population may be an interesting source for discovery of new antimicrobial agents. http://www.mdpi.com/1660-3397/6/4/620/ Mon, 01 Dec 2008 00:00:00 CET Marine Drugs 2008-12-01 6 4 Article 620 635 1660-3397 Characterization of Streptomyces spp. Isolated from the Sea Surface Microlayer in the Trondheim Fjord, Norway 2008-12-01 doi: 10.3390/md6040620 Sigrid Hakvåg Espen Fjærvik Kjell D. Josefsen Elena Ian Trond E. Ellingsen Sergey B. Zotchev http://www.mdpi.com/1660-3397/6/4/550/ Microbial marine biodiscovery is a recent scientific endeavour developing at a time when information and other technologies are also undergoing great technical strides. Global visualisation of datasets is now becoming available to the world through powerful and readily available software such as Worldwind ™, ArcGIS Explorer ™ and Google Earth ™. Overlaying custom information upon these tools is within the hands of every scientist and more and more scientific organisations are making data available that can also be integrated into these global visualisation tools. The integrated global view that these tools enable provides a powerful desktop exploration tool. Here we demonstrate the value of this approach to marine microbial biodiscovery by developing a geobibliography that incorporates citations on tropical and near-tropical marine microbial natural products research with Google Earth ™ and additional ancillary global data sets. The tools and software used are all readily available and the reader is able to use and install the material described in this article. http://www.mdpi.com/1660-3397/6/4/550/ Mon, 13 Oct 2008 00:00:00 CEST Marine Drugs 2008-10-13 6 4 Article 550 577 1660-3397 A Tropical Marine Microbial Natural Products Geobibliography as an Example of Desktop Exploration of Current Research Using Web Visualisation Tools 2008-10-13 doi: 10.3390/md20080028 Joydeep Mukherjee Lyndon E. Llewellyn Elizabeth A. Evans-Illidge http://www.mdpi.com/1660-3397/6/2/243/ Screening strategies based on the ecological knowledge of antibiotic producing microorganisms and their roles in the natural environment are being increasingly employed in the search for novel antibiotic agents. Micromonosporae are common inhabitants of aquatic habitats and have proved to be a continuing source of novel bioactive compounds including antibacterial and antitumor agents. The ecological distribution and frequency of bioactive micromonosporae in Sunshine Coast region aquatic habitats were studied through a range of selective isolation procedures designed to negatively select against the isolation of unwanted microbial taxa commonly associated with marine environments. It was revealed that bioactive compound producing species of micromonosporae were present in the aquatic habitats of the Sunshine Coast region in Australia. http://www.mdpi.com/1660-3397/6/2/243/ Thu, 05 Jun 2008 00:00:00 CEST Marine Drugs 2008-06-05 6 2 Article 243 261 1660-3397 The Occurrence of Bioactive Micromonosporae in Aquatic Habitats of the Sunshine Coast in Australia 2008-06-05 doi: 10.3390/md6020243 Glen P. Eccleston Peter R. Brooks D. Ipek Kurtböke http://www.mdpi.com/1660-3397/6/1/12/ The marine environment represents a largely untapped source for isolation of new microorganisms with potential to produce biologically active secondary metabolites. Among such microorganisms, Gram-positive actinomycete bacteria are of special interest, since they are known to produce chemically diverse compounds with a wide range of biological activities. We have set out to isolate and characterize actinomycete bacteria from the sediments in one of the largest Norwegian fjords, the Trondheim fjord, with respect to diversity and antibiotic-producing potential. Approximately 3,200 actinomycete bacteria were isolated using four different agar media from the sediment samples collected at different locations and depths (4.5 to 450 m). Grouping of the isolates first according to the morphology followed by characterization of isolates chosen as group representatives by molecular taxonomy revealed that Micromonospora was the dominating actinomycete genus isolated from the sediments. The deep water sediments contained a higher relative amount of Micromonospora compared to the shallow water samples. Nine percent of the isolates clearly required sea water for normal growth, suggesting that these strains represent obligate marine organisms. Extensive screening of the extracts from all collected isolates for antibacterial and antifungal activities revealed strong antibiotic-producing potential among them. The latter implies that actinomycetes from marine sediments in Norwegian fjords can be potential sources for the discovery of novel anti-infective agents. http://www.mdpi.com/1660-3397/6/1/12/ Fri, 01 Feb 2008 00:00:00 CET Marine Drugs 2008-02-01 6 1 Article 12 24 1660-3397 Actinomycetes from Sediments in the Trondheim Fjord, Norway: Diversity and Biological Activity 2008-02-01 doi: 10.3390/md6010012 Harald Bredholt Espen Fjærvik Geir Johnsen Sergey B. Zotchev http://www.mdpi.com/1660-3397/5/4/220/ The genus Pseudoalteromonas is a marine group of bacteria belonging to theclass Gammaproteobacteria that has come to attention in the natural product andmicrobial ecology science fields in the last decade. Pigmented species of the genus havebeen shown to produce an array of low and high molecular weight compounds withantimicrobial, anti-fouling, algicidal and various pharmaceutically-relevant activities.Compounds formed include toxic proteins, polyanionic exopolymers, substitutedphenolic and pyrolle-containing alkaloids, cyclic peptides and a range of bromine-substituted compounds. Ecologically, Pseudoalteromonas appears significant and to datehas been shown to influence biofilm formation in various marine econiches; involved inpredator-like interactions within the microbial loop; influence settlement, germinationand metamorphosis of various invertebrate and algal species; and may also be adopted bymarine flora and fauna as defensive agents. Studies have been so far limited to arelatively small subset of strains compared to the known diversity of the genussuggesting that many more discoveries of novel natural products as well as ecologicalconnections these may have in the marine ecosystem remain to be made. http://www.mdpi.com/1660-3397/5/4/220/ Tue, 18 Dec 2007 00:00:00 CET Marine Drugs 2007-12-18 5 4 Review 220 241 1660-3397 Bioactive Compound Synthetic Capacity and Ecological Significance of Marine Bacterial Genus Pseudoalteromonas 2007-12-18 doi: 10.3390/md504220 John P. Bowman http://www.mdpi.com/1660-3397/5/3/52/ 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. http://www.mdpi.com/1660-3397/5/3/52/ Thu, 19 Jul 2007 00:00:00 CEST Marine Drugs 2007-07-19 5 3 Article 52 70 1660-3397 Cytotoxicity of the Ascidian Cystodytes dellechiajei Against Tumor Cells and Study of the Involvement of Associated Microbiota in the Production of Cytotoxic Compounds 2007-07-19 doi: 10.3390/md503052 Manuel Martínez-García Marta Díaz-Valdés Alfonso Ramos-Esplá Nélida Salvador Patricia Lopez Eduardo Larriba Josefa Antón