A D Karagouni

National and Kapodistrian University of Athens, Athínai, Attica, Greece

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Publications (66)118.26 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The deterioration of the Acropolis monuments’ surface can be attributed to a combination of mechanical, physical, chemical and biological factors. The aim of this work was to investigate the potential use of biocides suitable for marble surface in order to confront the biodeterioration phenomenon due to heterotrophic bacteria. Surface bacterial populations were studied in respect to the application of three biocide agents. A significant decrease of the bacterial counts was occurred after the biocides’ application and remained less compared with the counts occurred on the untreated surfaces for more than 14 months. A gradual diminution of bacterial diversity was also observed leading to the survival of specific Gram positive strains.
    Geomicrobiology 09/2014; 31(8). · 1.61 Impact Factor
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    ABSTRACT: The ascomycete Paecillomyces variotii was evaluated for the first time as a candidate species for the production of bioethanol from lignocellulose through consolidated bioprocessing (CBP) approaches. The examined strain (ATHUM 8891) revealed all the necessary phenotypic characteristics required for 2nd generation biofuel production. The fungus is able to efficiently ferment glucose and xylose to ethanol, with yields close to the theoretical maximum. Nitrogen supplementation greatly affected ethanol production with nitrate-nitrogen presenting the best results. Notably, ethanol yield on xylose fermentation was higher than that of glucose, while in co-fermentation of glucose-xylose mixtures no distinguished diauxic behavior was observed. Furthermore, the fungus seems to possess the necessary enzyme factory for the degradation of lignocellulosic biomass, as it was able to grow and produce ethanol on common agro-industrial derivatives. Overall, the results of our study indicate that P. variotii is a new and possibly powerful candidate for CBP applications.
    Bioresource Technology 04/2014; 162C:294-299. · 5.04 Impact Factor
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    ABSTRACT: Gene fusion and fission events are important for evolutionary studies and for predicting protein-protein interactions. Previous studies have shown that fusion events always predominate over fission events and, in their majority, they represent singular events throughout evolution. In this project, the role of fusion and fission events in the genome evolution of 104 human bacterial pathogens was studied. 141 protein pairs were identified to be involved in gene fusion or fission events. Surprisingly, we find that, in the species analyzed, gene fissions prevail over fusions. Moreover, while most events appear to have occurred only once in evolution, 23% of the gene fusion and fission events identified are deduced to have occurred independently multiple times. Comparison of the analyzed bacteria with non-pathogenic close relatives indicates that this impressive result is associated with the recent evolutionary history of the human bacterial pathogens, and thus is probably caused by their pathogenic lifestyle.
    Genomics 01/2014; · 3.01 Impact Factor
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    ABSTRACT: The ascomycete Paecillomyces variotii was evaluated for the first time as a candidate species for the production of bioethanol from lignocellulose through consolidated bioprocessing (CBP) approaches. The examined strain (ATHUM 8891) revealed all the necessary phenotypic characteristics required for 2nd generation biofuel production. The fungus is able to efficiently ferment glucose and xylose to ethanol, with yields close to the theoretical maximum. Nitrogen supplementation greatly affected ethanol production with nitrate-nitrogen presenting the best results. Notably, ethanol yield on xylose fermentation was higher than that of glucose, while in co-fermentation of glucose–xylose mixtures no distinguished diauxic behavior was observed. Furthermore, the fungus seems to possess the necessary enzyme factory for the degradation of lignocellulosic biomass, as it was able to grow and produce ethanol on common agro-industrial derivatives. Overall, the results of our study indicate that P. variotii is a new and possibly powerful candidate for CBP applications.
    Bioresource Technology 01/2014; 162:294–299. · 5.04 Impact Factor
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    ABSTRACT: Multidrug-resistant Pseudomonas aeruginosa is a serious challenge for antimicrobial therapy of nosocomial infections, as it possesses several mechanisms of antimicrobial resistance. In Central Greece, a sudden increase of infections caused by carbapenem-resistant P. aeruginosa was observed during 2011, indicating the need for further analysis. Five-hundred and sixty-eight P. aeruginosa isolates were collected consecutively during an 8-month period in 2011 from inpatients treated in three hospitals in the Thessaly region (1,000,000 habitants) of Greece. Carbapenem-resistant P. aeruginosa (n = 284) were characterized by antimicrobial susceptibility testing and beta-lactamase content, and the genetic relatedness of carbapenemase-producing isolates was assessed by BOX-PCR, multilocus sequence typing, and eBURST analysis. Mapping of the class I integrons of Verona integron-encoded metallo-beta-lactamase (VIM)-carrying isolates was also performed, and clinical data of the VIM producers were reviewed. Eighty (14.1%) out of the 568 P. aeruginosa isolates recovered from clinical specimens were VIM producers. Multilocus sequence typing revealed high prevalence of the international clones ST111 and ST235 among blaVIM-2- and blaVIM-4-positive isolates, respectively. blaVIM-17 was identified in an isolate of a novel sequence type (ST1457). blaVIM gene cassettes were carried by five distinct class I integrons, including two novel ones. Since the first report of VIM-producing P. aeruginosa in 2000, this microorganism still remains among the most prevalent multidrug resistant pathogens in Greece. The spread of VIM-producers belonging to the most common international clones (ST111 and ST235), the spread of integrons of divergent structures, and the emergence of novel integrons underscore their ongoing evolution.
    BMC Infectious Diseases 10/2013; 13(1):505. · 3.03 Impact Factor
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    ABSTRACT: AIMS: To examine the biocontrol potential of multi-active Greek indigenous Streptomyces isolates carrying antifungal activity against Rhizoctonia solani that causes damping-off symptoms on beans. METHODS AND RESULTS: A total of 605 Streptomyces isolates originated from 12 diverse Greek habitats were screened for antifungal activity against R. solani DSM843. Almost one third of the isolates proved to be antagonistic against the fungus. From the above isolates, six were selected due to their higher antifungal activity, identified by analyzing their 16rRNA gene sequence and studied further. The obtained data showed: firstly, that the isolates ACTA1383 and ACTA1557, exhibited the highest antagonistic activity and therefore they were selected for in vivo experiments using bean seeds as target; secondly, in solid and liquid culture experiments under optimum antagonistic conditions, the medium extracts from the isolates OL80, ACTA1523, ACTA1551 and ACTA1522 suppressed the growth of the fungal mycelium, whilst extracts from ACTA 1383 and ACTA1557 did not show any activity. CONCLUSIONS: These results corresponded important indications for the utility of two Greek indigenous Streptomyces isolates (ACTA1557 and ACTA1383) for the protection of the bean crops from Rhizoctonia solani damping-off symptoms while four of them (isolates OL80, ACTA1523, ACTA1551 and ACTA1522) seem to be promising producers of antifungal metabolites. © 2013 The Authors Journal of Applied Microbiology © 2013 The Society for Applied Microbiology.
    Journal of Applied Microbiology 01/2013; · 2.20 Impact Factor
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    ABSTRACT: Aim. Tracking the dispersal patterns and habitat use of migratory species is necessary to delineate optimal areas for protection, with large sample sizes being more representative of the population. Here, we examine the dispersal patterns of a key Mediterranean loggerhead turtle (Caretta caretta) breeding population to identify priority foraging sites for protection. Location. Zakynthos Island, Greece and the wider Mediterranean. Method. We examined the dispersal patterns and foraging sites of 75 adult loggerheads (n = 38 males and 37 females) tracked from the breeding area of Zakynthos Island (Greece) from 2004 to 2011. We then combined our data with published sea turtle literature to identify key foraging sites for protection. Results. While both males and females exhibited similar dispersal patterns, about 25% males remained < 100 km of Zakynthos, whereas all females (except one) migrated > 200 km. Integration of our data with the wider literature isolated 10 core sites in proximity to existing protected areas, which could potentially protect 64% of the Zakynthos population, while five sites support individuals from at least 10 other loggerhead breeding populations. Main conclusions. Due to the widespread availability of neritic foraging grounds across the Mediterranean, sea turtles from Zakynthos exhibit disparate dispersal patterns. However, protecting only a few objectively defined important sites can encompass a large proportion of the foraging areas used and hence have considerable conservation benefit.
    Diversity and Distributions 01/2013; · 6.12 Impact Factor
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    ABSTRACT: In a bioprospecting effort towards novel thermostable lipases, we assessed the lipolytic profile of 101 bacterial strains isolated from the volcanic area of Santorini, Aegean Sea, Greece. Screening of lipase activity was performed both in agar plates and liquid cultures using olive oil as carbon source. Significant differences were observed between the two screening methods with no clear correlation between them. While the percentage of lipase producing strains identified in agar plates was only 17%, lipolytic activity in liquid culture supernatants was detected for 74% of them. Nine strains exhibiting elevated extracellular lipase activities were selected for lipase production and biochemical characterization. The majority of lipase producers revealed high phylogenetic similarity with Geobacillus species and related genera, whilst one of them was identified as Aneurinibacillus sp. Lipase biosynthesis strongly depended on the carbon source that supplemented the culture medium. Olive oil induced lipase production in all strains, but maximum enzyme yields for some of the strains were also obtained with Tween-80, mineral oil, and glycerol. Partially purified lipases revealed optimal activity at 70-80°C and pH 8-9. Extensive thermal stability studies revealed marked thermostability for the majority of the lipases as well as a two-step thermal deactivation pattern.
    BioMed research international. 01/2013; 2013:703130.
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    ABSTRACT: Cyanobacteria cause aesthetic damage to marble surfaces and in particular their endolithic mode of life contributes to the breakdown of rock crystalline structures. The aim of this work was to estimate, with both phenotypical and molecular approach, the composition of cyanobacterial communities on the Propylaea marbles of the Acropolis Monuments. The two selected sampling sites were treated and untreated with a commercial biocide in order to estimate its effect on the cyanobacterial diversity. Our study revealed that in both sampling sites were present 13 phenotypes and 10 phylotypes and that the cyanobacterial taxa were considerably lower in the treated site.
    Geomicrobiology 01/2013; 30(4):371-378. · 1.61 Impact Factor
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    ABSTRACT: Marine Protected Areas (MPAs) now form an important part of marine conservation and fisheries management; hence, there is broad interest in developing procedures that optimize their design. We used data collected over a 10-year period (2003–2012) from direct surveys and >100 adult male and female loggerhead sea turtles (Caretta caretta) tracked with devices, includ ing GPS loggers and Fastloc GPS Argos, to consider the optimum design for a MPA at a globally important breeding area, where there is already an existing national marine park aiming to protect the population (Zakynthos, Greece). Turtles primarily used areas very close to shore (approx. 7 km in length by 1 km in width, within the <10 m isobath) for breeding and foraging activity at different times of the year. We calculated that this small nearshore coastal zone encompassed 72% of all turtle GPS locations recorded in the MPA, and is therefore important for conservation management. We developed an index to evaluate the suitability of the existing and proposed conservation zones based on (1) home range area use by turtles in these zones versus (2) zone size, so that the benefit to turtles could be maximized while minimizing the negative impacts to other stakeholders (e.g., boat operators). With this evidence-based approach, we propose a modification to the existing MPA that might both enhance local economic tourism activities and better safeguard this key sea turtle breeding population. The approaches used here will have general application for the design of MPAs used by mobile species that can be tracked.
    Biological Conservation 01/2013; 161:101-109. · 3.79 Impact Factor
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    ABSTRACT: Many studies have shown that several Greek ecosystems inhabit very interesting bacteria with biotechnological properties. Therefore Streptomyces isolates from diverse Greek habitats were selected for their antifungal activity against the common phytopathogenic fungus Fusarium oxysporum. The isolate encoded ACTA1551, member of Streptomyces genus, could strongly suppress the fungal growth when examined in antagonistic bioassays in vitro. The isolate was found phylogenetically relative to Streptomyces rochei after analyzing its 16S rDNA sequence. The influence of different environmental conditions, such as medium composition, temperature, and pH on the expression of the antifungal activity was thoroughly examined. Streptomyces rochei ACTA1551 was able to protect tomato seeds from F. oxysporum infection in vivo while it was shown to promote the growth of tomato plants when the pathogen was absent. In an initial effort towards the elucidation of the biochemical and physiological nature of ACTA1551 antifungal activity, extracts from solid streptomycete cultures under antagonistic or/and not antagonistic conditions were concentrated and fractionated. The metabolites involved in the antagonistic action of the isolate showed to be more than one and produced independently of the presence of the pathogen. The above observations could support the application of Streptomyces rochei ACTA1551 as biocontrol agent against F. oxysporum.
    BioMed research international. 01/2013; 2013:387230.
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    ABSTRACT: Xanthan gum is a polysaccharide that is widely used as stabilizer and thickener with many industrial applications in food industry. Our aim was to estimate the ability of Xanthomonas campestris ATCC 13951 for the production of xanthan gum by using whey as a growth medium, a by-product of dairy industry. X. campestris ATCC 13951 has been studied in batch cultures using a complex medium for the determination of the optimal concentration of glucose, galactose and lactose. In addition, whey was used under various treatment procedures (de-proteinated, partially hydrolyzed by β-lactamase and partially hydrolyzed and de-proteinated) as culture medium, to study the production of xanthan in a 2 l bioreactor with constant stirring and aeration. A production of 28 g/l was obtained when partially hydrolysed β-lactamase was used, which proved to be one of the highest xanthan gum production reported so far. At the same time, an effort has been made for the control and selection of the most appropriate procedure for the preservation of the strain and its use as inoculant in batch cultures, without loss of its viability and its capability of xanthan gum production. The pre-treatment of whey (whey permeate medium hydrolyzed, WPH) was very important for the production of xanthan by the strain X. campestris ATCC 13951 during batch culture conditions in a 2 l bioreactor. Preservation methods such as lyophilization, cryopreservation at various glycerol solution and temperatures have been examined. The results indicated that the best preservation method for the producing strain X. campestris ATCC 13951 was the lyophilization. Taking into account that whey permeate is a low cost by-product of the dairy industry, the production of xanthan achieved under the studied conditions was considered very promising for industrial application.
    MIRCEN Journal of Applied Microbiology and Biotechnology 08/2012; 28(8):2759-64. · 1.08 Impact Factor
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    ABSTRACT: The biomass degrading enzymatic potential of 101 thermophilic bacterial strains isolated from a volcanic environment (Santorini, Aegean Sea, Greece) was assessed. 80 % of the strains showed xylanolytic activity in Congo Red plates, while only eight could simultaneously hydrolyze cellulose. Fifteen isolates were selected on the basis of their increased enzyme production, the majority of which was identified as Geobacilli through 16S rDNA analysis. In addition, the enzymatic profile was evaluated in liquid cultures using various carbon sources, a procedure that revealed lack of correlation on xylanase levels between the two cultivation modes and the inability of solid CMC cultures to fully unravel the cellulose degrading potential of the isolates. Strain SP24, showing more than 99 % 16S DNA similarity with Geobacillus sp. was further studied for its unique ability to simultaneously exhibit cellulase, xylanase, β-glucosidase and β-xylosidase activities. The first two enzymes were produced mainly extracellularly, while the β-glycosidic activities were primarily detected in the cytosol. Maximum enzyme production by this strain was attained using a combination of wheat bran and xylan in the growth medium. Bioreactor cultures showed that aeration was necessary for both enhanced growth and enzyme production. Aeration had a strong positive effect on cellulase production while it negatively affected expression of β-glucosidase. Xylanase and β-xylosidase production was practically unaffected by aeration levels.
    MIRCEN Journal of Applied Microbiology and Biotechnology 06/2012; 28(9):2889-902. · 1.08 Impact Factor
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    ABSTRACT: Two-phase olive-mill waste, the so-called "ecological", has been treated with a Paecilomyces variotii isolate in solid state fermentation experiments. The growth of the microorganism was estimated by measuring the production of carbon dioxide, using gas chromatography. A 46% increase of the protein content was achieved at the fermented product, after molasses addition at the initial mixture. The amino acid profile of the produced protein, as far as the essential amino acids are concerned, was significantly improved, resulting in a product that has the potential to be used as animal feed. Furthermore, it contains lysine, one of the essential amino acids that did not exist at the original product and is produced during fermentation. This is the first report on solid state fermentation of the two-phase olive mill waste (TPOMW) as a substrate, using a Paecilomyces variotii strain.
    MIRCEN Journal of Applied Microbiology and Biotechnology 03/2012; 28(3):849-56. · 1.08 Impact Factor
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    ABSTRACT: We report on the sequence type and beta-lactamase content of 174 carbapenem-resistant Acinetobacter baumannii isolates recovered from clinical specimens during 2010 and 2011 in a tertiary care hospital in central Greece. Carbapenem resistance was associated mainly with carriage of the bla(OXA-23) gene (in 72.4% of the isolates). To our knowledge, this is the first description of A. baumannii strains producing OXA-23 in Greece. During 2011, in our hospital they rapidly ‘replaced’ the previously predominant OXA-58- positive A. baumannii strains.
    Euro surveillance: bulletin europeen sur les maladies transmissibles = European communicable disease bulletin 01/2012; 17(11). · 5.49 Impact Factor
  • New Biotechnology 01/2012; 29:S5. · 1.71 Impact Factor
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    ABSTRACT: Domain Fusion Analysis takes advantage of the fact that certain proteins in a given proteome A, are found to have statistically significant similarity with two separate proteins in another proteome B. In other words, the result of a fusion event between two separate proteins in proteome B is a specific full-length protein in proteome A. In such a case, it can be safely concluded that the protein pair has a common biological function or even interacts physically. In this paper, we present the Fusion Events Database (FED), a database for the maintenance and retrieval of fusion data both in prokaryotic and eukaryotic organisms and the Software for the Analysis of Fusion Events (SAFE), a computational platform implemented for the automated detection, filtering and visualization of fusion events (both available at: http://www.bioacademy.gr/bioinformatics/projects/ProteinFusion/index.htm). Finally, we analyze the proteomes of three microorganisms using these tools in order to demonstrate their functionality.
    Evolutionary bioinformatics online 01/2012; 8:47-60. · 1.33 Impact Factor
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    ABSTRACT: The structure of the Bacteria and Archaea community in a large drinking water reservoir (Marathonas, Greece; MR) was investigated in October 2007 and September 2008, using 16S rRNA gene clone libraries. The bacterial communities were more diverse than archaeal communities (Shannon diversity index H' 0.81-3.28 and 1.36-1.77, respectively). The overall bacterial community composition was comparable to bacterioplankton community described in other freshwater habitats. Within the Bacteria, Betaproteobacteria dominated, while representatives of Alpha-, Gamma- and Deltaproteobacteria also occurred. Other important phyla were Actinobacteria and Bacteroidetes, while representatives of Acidobacteria, Cyanobacteria, Chloroflexi, Planctomycetes and Verrucomicrobia were also retrieved. Several phylotypes in Alpha- and Betaproteobacteria and Bacteroidetes were related to bacteria capable of cyanotoxin degradation and with aromatic compounds/iron oxidizers or polymer degraders. Euryarchaeota dominated (60.5%) the Archaea community mostly with phylotypes related to Methanobacteriales and Methanosarcinales. Among the Thaumarchaeota, the two most abundant phylotypes were affiliated (97% similarity) with the only cultivated mesophilic thaumarchaeote of marine origin, Nitrosopumilus maritimus. Temporal and spatial comparison of the prokaryotic community structure revealed that three of the most abundant prokaryotic phylotypes, belonging to Actinobacteria, were recovered from all sites both years, suggesting that these Actinobacteria could be important key players in MR ecosystem functioning.
    Microbes and Environments 10/2011; 27(1):1-8. · 2.44 Impact Factor
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    ABSTRACT: In an effort to increase ethanol productivity during the consolidated bioprocessing (CBP) of lignocellulosics by Fusarium oxysporum, we attempted the constitutive homologous overexpression of one of the key process enzymes, namely an endo-xylanase. The endo-β-1,4-xylanase 2 gene was incorporated into the F. oxysporum genome under the regulation of the gpdA promoter of Aspergillus nidulans. The transformation was effected through Agrobacterium tumefaciens and resulted in 12 transformants, two of which were selected for further study due to their high extracellular xylanase activities under normally repressing conditions (glucose as sole carbon source). During natural induction conditions (growth on xylan) though, the extracellular enzyme levels of the transformants were only marginally higher (5-10%) compared to the wild type despite the significantly stronger xylanase 2 mRNA signals. SDS-PAGE verified enzyme assay results that there was no intracellular xylanase 2 accumulation in the transformants, suggesting the potential regulation in a post transcriptional or translational level. The fermentative performance of the transformants was evaluated and compared to that of the wild type in simple CBP systems using either corn cob or wheat bran as sole carbon sources. Both transformants produced approximately 60% more ethanol compared to the wild type on corn cob, while for wheat bran this picture was repeated for only one of them. This result is attributed to the high extracellular xylanase activities in the transformants' fermentation broths that were maintained 2-2.5-fold higher compared to the wild type.
    Journal of Biotechnology 01/2011; 152(1-2):16-23. · 3.18 Impact Factor
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    ABSTRACT: Four sampling sites were selected in the area of Velouhi mountain, Greece in order to screen for Pseudomonas syringae isolates with high ice nucleation activity from a ski resort environment. Bacterial isolates (n=147) were obtained from soil and phyllosphere samples. Seven isolates exhibited morphological, biochemical and physiological profile similar to P. syringae. Phylogenetic relationships of the seven isolates were determined by 16S rRNA gene sequencing. Two isolates were phylogenetically affiliated to P. syringae, three to P. viridiflava, one to P. avellanae, and one Pseudomonas strain could not be assigned to a known species. The seven isolates were examined for their ice-nucleation activity properties. Three out of the seven studied isolates exhibited ice nucleation activity from –4.67 to –4.35 ice nuclei per cell, values similar to those obtained from a known ice-nucleation protein producer P. syringae strain and therefore could be used for the production of artificial snow in ski resort areas with short snow periods.
    Journal of Biological Research. 01/2011; 15:67-73.

Publication Stats

497 Citations
118.26 Total Impact Points

Institutions

  • 2004–2014
    • National and Kapodistrian University of Athens
      • • Division of Biology
      • • Department of Botany
      • • Faculty of Biology
      Athínai, Attica, Greece
  • 1998–2012
    • Athens State University
      • Department of Biology
      Athens, Alabama, United States