Kostas Bourtzis

University of Patras, Rhion, West Greece, Greece

Are you Kostas Bourtzis?

Claim your profile

Publications (96)363.68 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cydia splendana and C. fagiglandana are two closely related chestnut feeding lepidopteran moth species. In this study, we surveyed the bacterial endosymbiont Wolbachia in these two species. Infection rates were 31% in C. splendana and 77% in C. fagiglandana. MLST analysis showed that these two species are infected with two quite diverse Wolbachia strains. C. splendana with Sequence Type (ST) 409 from the A-supergroup and C. fagiglandana with ST 150 from the B-supergroup. One individual of C. splendana was infected with ST 150, indicating horizontal transfer between these sister species. The mitochondrial DNA of the two Cydia species showed a significantly different mtDNA diversity, which was inversely proportional to their infection rates.
    PLoS ONE 11/2014; · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Bactrocera papayae Drew & Hancock, Bactrocera philippinensis Drew & Hancock, Bactrocera carambolae Drew & Hancock, and Bactrocera invadens Drew, Tsuruta & White are four horticultural pest tephritid fruit fly species that are highly similar, morphologically and genetically, to the destructive pest, the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). This similarity has rendered the discovery of reliable diagnostic characters problematic, which, in view of the economic importance of these taxa and the international trade implications, has resulted in ongoing difficulties for many areas of plant protection and food security. Consequently, a major international collaborative and integrated multidisciplinary research effort was initiated in 2009 to build upon existing literature with the specific aim of resolving biological species limits among B. papayae, B. philippinensis, B. carambolae, B. invadens and B. dorsalis to overcome constraints to pest management and international trade. Bactrocera philippinensis has recently been synonymized with B. papayae as a result of this initiative and this review corroborates that finding; however, the other names remain in use. While consistent characters have been found to reliably distinguish B. carambolae from B. dorsalis, B. invadens and B. papayae, no such characters have been found to differentiate the latter three putative species. We conclude that B. carambolae is a valid species and that the remaining taxa, B. dorsalis, B. invadens and B. papayae, represent the same species. Thus, we consider B. dorsalis (Hendel) as the senior synonym of B. papayae Drew and Hancock syn.n. and B. invadens Drew, Tsuruta & White syn.n. A redescription of B. dorsalis is provided. Given the agricultural importance of B. dorsalis, this taxonomic decision will have significant global plant biosecurity implications, affecting pest management, quarantine, international trade, postharvest treatment and basic research. Throughout the paper, we emphasize the value of independent and multidisciplinary tools in delimiting species, particularly in complicated cases involving morphologically cryptic taxa.
    Systematic Entomology 10/2014; · 2.88 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In the last decade, bacterial symbionts have been shown to play an important role in protecting hosts against pathogens. Wolbachia, a widespread symbiont in arthropods, can protect Drosophila and mosquito species against viral infections. We have investigated antiviral protection in 19 Wolbachia strains originating from 16 Drosophila species after transfer into the same genotype of Drosophila simulans. We found that approximately half of the strains protected against two RNA viruses. Given that 40% of terrestrial arthropod species are estimated to harbour Wolbachia, as many as a fifth of all arthropods species may benefit from Wolbachia-mediated protection. The level of protection against two distantly related RNA viruses – DCV and FHV – was strongly genetically correlated, which suggests that there is a single mechanism of protection with broad specificity. Furthermore, Wolbachia is making flies resistant to viruses, as increases in survival can be largely explained by reductions in viral titer. Variation in the level of antiviral protection provided by different Wolbachia strains is strongly genetically correlated to the density of the bacteria strains in host tissues. We found no support for two previously proposed mechanisms of Wolbachia-mediated protection — activation of the immune system and upregulation of the methyltransferase Dnmt2. The large variation in Wolbachia's antiviral properties highlights the need to carefully select Wolbachia strains introduced into mosquito populations to prevent the transmission of arboviruses. Copyright: ß 2014 Martinez et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files except for the sequence of Multilocus Sequence Typing genes which are available from Genbank under the accession numbers listed in Table S2.. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist.
    PLoS pathogens. 09/2014; 10(9).
  • Source
    Science. 04/2014; 344:385.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein-encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology.
    Science 04/2014; 344(6182):380-386. · 31.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tsetse flies are the sole vectors of human African trypanosomiasis throughout sub-Saharan Africa. Both sexes of adult tsetse feed exclusively on blood and contribute to disease transmission. Notable differences between tsetse and other disease vectors include obligate microbial symbioses, viviparous reproduction, and lactation. Here, we describe the sequence and annotation of the 366-megabase Glossina morsitans morsitans genome. Analysis of the genome and the 12,308 predicted protein–encoding genes led to multiple discoveries, including chromosomal integrations of bacterial (Wolbachia) genome sequences, a family of lactation-specific proteins, reduced complement of host pathogen recognition proteins, and reduced olfaction/chemosensory associated genes. These genome data provide a foundation for research into trypanosomiasis prevention and yield important insights with broad implications for multiple aspects of tsetse biology.
    Science 04/2014; 344:380. · 31.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tsetse flies (Glossina spp.) are the cyclical vectors of Trypanosoma spp., which are unicellular parasites responsible for multiple diseases, including nagana in livestock and sleeping sickness in humans in Africa. Glossina species, including Glossina morsitans morsitans (Gmm), for which the Whole Genome Sequence (WGS) is now available, have established symbiotic associations with three endosymbionts: Wigglesworthia glossinidia, Sodalis glossinidius and Wolbachia pipientis (Wolbachia). The presence of Wolbachia in both natural and laboratory populations of Glossina species, including the presence of horizontal gene transfer (HGT) events in a laboratory colony of Gmm, has already been shown. We herein report on the draft genome sequence of the cytoplasmic Wolbachia endosymbiont (cytWol) associated with Gmm. By in silico and molecular and cytogenetic analysis, we discovered and validated the presence of multiple insertions of Wolbachia (chrWol) in the host Gmm genome. We identified at least two large insertions of chrWol, 527,507 and 484,123 bp in size, from Gmm WGS data. Southern hybridizations confirmed the presence of Wolbachia insertions in Gmm genome, and FISH revealed multiple insertions located on the two sex chromosomes (X and Y), as well as on the supernumerary B-chromosomes. We compare the chrWol insertions to the cytWol draft genome in an attempt to clarify the evolutionary history of the HGT events. We discuss our findings in light of the evolution of Wolbachia infections in the tsetse fly and their potential impacts on the control of tsetse populations and trypanosomiasis.
    PLoS Neglected Tropical Diseases 04/2014; 8(4):e2728. · 4.57 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rhagoletis cerasi (Diptera: Tephritidae) is a major pest of sweet and sour cherries in Europe and parts of Asia. Despite its economic significance, there is a lack of studies on the genetic structure of R. cerasi populations. Elucidating the genetic structure of insects of economic importance is crucial for developing phenological-predictive models and environmental friendly control methods. All natural populations of R. cerasi have been found to harbor the endosymbiont Wolbachia pipientis, which widely affects multiple biological traits contributing to the evolution of its hosts, and has been suggested as a tool for the biological control of insect pests and disease vectors. In the current study, the analysis of 18 R. cerasi populations collected in Greece, Germany, and Russia using 13 microsatellite markers revealed structuring of R. cerasi natural populations, even at close geographic range. We also analyzed the Wolbachia infection status of these populations using 16S rRNA-, MLST- and wsp-based approaches. All 244 individuals screened were positive for Wolbachia. Our results suggest the fixation of the wCer1 strain in Greece while wCer2, wCer4, wCer5, and probably other uncharacterized strains were also detected in multiply infected individuals. The role of Wolbachia and its potential extended phenotypes needs a thorough investigation in R. cerasi. Our data suggest an involvement of this symbiont in the observed restriction in the gene flow in addition to a number of different ecological factors.
    Ecology and Evolution 04/2014; · 1.66 Impact Factor
  • Source
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Mosquito species, members of the genera Aedes, Anopheles and Culex, are the major vectors of human pathogens including protozoa (Plasmodium spp.), filariae and of a variety of viruses (causing dengue, chikungunya, yellow fever, West Nile). There is lack of efficient methods and tools to treat many of the diseases caused by these major human pathogens, since no efficient vaccines or drugs are available; even in malaria where insecticide use and drug therapies have reduced incidence, 219 million cases still occurred in 2010. Therefore efforts are currently focused on the control of vector populations. Insecticides alone are insufficient to control mosquito populations since reduced susceptibility and even resistance is being observed more and more frequently. There is also increased concern about the toxic effects of insecticides on non-target (even beneficial) insect populations, on humans and the environment. During recent years, the role of symbionts in the biology, ecology and evolution of insect species has been well-documented and has led to suggestions that they could potentially be used as tools to control pests and therefore diseases. Wolbachia is perhaps the most renowned insect symbiont, mainly due to its ability to manipulate insect reproduction and to interfere with major human pathogens thus providing new avenues for pest control. We herein present recent achievements in the field of mosquito-Wolbachia symbiosis with an emphasis on Aedes albopictus. We also discuss how Wolbachia symbiosis can be harnessed for vector control as well as the potential to combine the sterile insect technique and Wolbachia-based approaches for the enhancement of population suppression programs.
    Acta tropica 11/2013; · 2.79 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Tsetse flies (Diptera: Glossinidae) harbour three known vertically transmitted bacterial symbionts (Wigglesworthia, Sodalis, and/or Wolbachia) that modulate the reproduction and immune competence of the flies. Wigglesworthia and Sodalis are both intra- and extra-cellular, while Wolbachia is strictly intracellular. Wigglesworthia resides in the midgut bacteriocytes or in the milk glands and does not infect reproductive tissues. Sodalis resides in the reproductive tract and infects the mid-guts, hemolymph and milk glands, while Wolbachia exclusively infects germ tissues. Some tsetse species such as G. pallidipes also harbour Glossina pallidipes salivary gland hypertrophy virus (GpSGHV), whose infection phenotypes can be either asymptomatic or symptomatic. In mosquitoes, aphids and tsetse the removal of the symbionts by antibiotics impacts host fitness and increases host susceptibility to pathogen infections. We therefore hypothesized that suppression of the G. pallidipes symbionts would alter GpSGHV titres and/or expression of salivary gland hypertrophy (SGH) in parent and their progenies. Injected virus replicated in the parents, but was not secreted via saliva during fly feeding. Whereas GpSGHV-injected parents did not exhibit SGH, the incidence of SGH symptoms increased from 4.5% to > 95% from the first to the fourth larviposition cycles of the F1 progenies. Ampicillin had negligible impacts on the virus titres in adult parents. However, the antibiotic reduced titres of GpSGHV, Sodalis and Wigglesworthia, and negated expression of SGH symptoms in the F1 progenies. Wolbachia was not detected in any of the analysed samples. The results indicated that the fat body tracheal system may provide a conduit for the trans-generational GpSGHV transmission via milk gland secretions, and that the removal of the microbiome suppresses this transmission. These data suggest that the G. pallidipes microbiome may have co-evolved with GpSGHV, and plays key roles in the mother-to-progeny transmission of the virus.
    EFS-EMBO Symposium; Integrated insect immunology: From basic biology to environmental applications, Polonia Castle in Pultusk, Poland; 09/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Etoliko, an anoxic semi-enclosed basin, is part of a complex wetland in Western Greece extremely rich in biodiversity. It covers an area of 1,700 ha with an atypical orientation that has been formed tectonically. In order to identify the main factors influencing the bacterial profile at the Etoliko basin, 48 samples were collected, representing seasonal variation at four sampling stations. Physico-chemical analysis of the samples indicates the presence of three layers in the Etoliko basin: (1) low-density surface layer, (2) a layer with a steep density gradient, and (3) dense water below a depth of 20 m. A permanent halocline, whose thickness is varying seasonally, has been identified in the Etoliko basin water column, while the spatiotemporal salinity distribution was highly affected by the basin’s interaction with the nearby Messolonghi lagoon. The anoxic zone extends from 20 m below the surface to the bottom of the Etoliko basin in summer, while the bottom layer was hypoxic during winter. Bacterial populations were analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA). Bacterial richness and diversity were calculated and compared across samples. Hierarchical analysis showed that ARISA clustered the surface water samples according to seasonal variation, while sediment and near-to-bottom water samples appear to be stable and to cluster together. Non-metric multidimensional scaling (MDS) indicates that bacterial composition depends on dissolved oxygen and salinity. Increase in salinity of the ecosystem leads to a significant reduction of the microbial diversity.
    Annals of Microbiology 09/2013; · 1.55 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: When considering a mosquito release programme, one of the first issues to be addressed is how to eliminate/separate the females. The greatest number of options might eventually be available for those who can use transgenic mosquitoes, but the inherent characteristics of the target species may also provide possibilities for interim measures until more efficient methods can be developed. Differences in intrinsic size, in behaviour and in development rate between females and males are often available and useful for sexing. Efficient species-specific systems for eliminating females at the embryo stage have been developed, but most have since been discarded due to lack of use. Ideal systems specifically kill female embryos using some treatment that can be manipulated during production. Such killing systems are far more efficient than using intrinsic sexual differences, but they systems require selectable genetic markers and sex-linkage created by rare random chromosomal rearrangements. While intrinsic sexual differences should not be considered as long-term candidates for the development of robust and efficient sexing approaches, in the absence of these, the accessibility and integration of less efficient systems can provide a stop-gap measure that allows rapid start up with a minimum of investment. The International Atomic Energy Agency is funding over a 5 year period (2013-2018) a new Coordinated Research Project on "Exploring Genetic, Molecular, Mechanical and Behavioural Methods of Sex Separation in Mosquitoes" to network researchers and to address the critical need of genetic sexing strains for the implementation of the sterile insect technique (using radiation-sterilised or transgenic male mosquitoes) and for insect incompatibility technique programmes against disease-transmitting mosquitoes.
    Acta tropica 08/2013; · 2.79 Impact Factor
  • Source
    Spyridon Ntougias, Kostas Bourtzis, George Tsiamis
    [Show abstract] [Hide abstract]
    ABSTRACT: Olive mill wastes (OMWs) are high-strength organic effluents, which upon disposal can degrade soil and water quality, negatively affecting aquatic and terrestrial ecosystems. The main purpose of this review paper is to provide an up-to-date knowledge concerning the microbial communities identified over the past 20 years in olive mill wastes using both culture-dependent and independent approaches. A database survey of 16S rRNA gene sequences (585 records in total) obtained from olive mill waste environments revealed the dominance of members of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Actinobacteria. Independent studies confirmed that OMW microbial communities' structure is cultivar dependant. On the other hand, the detection of fecal bacteria and other potential human pathogens in OMWs is of major concern and deserves further examination. Despite the fact that the degradation and detoxification of the olive mill wastes have been mostly investigated through the application of known bacterial and fungal species originated from other environmental sources, the biotechnological potential of indigenous microbiota should be further exploited in respect to olive mill waste bioremediation and inactivation of plant and human pathogens. The implementation of omic and metagenomic approaches will further elucidate disposal issues of olive mill wastes.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The vertically transmitted endosymbionts (Sodalis glossinidius and Wigglesworthia glossinidia) of the tsetse fly (Diptera: Glossinidae) are known to supplement dietary deficiencies and modulate the reproductive fitness and the defense system of the fly. Some tsetse fly species are also infected with the bacterium, Wolbachia and with the Glossina hytrosavirus (GpSGHV). Laboratory-bred G. pallidipes exhibit chronic asymptomatic and acute symptomatic GpSGHV infection, with the former being the most common in these colonies. However, under as yet undefined conditions, the asymptomatic state can convert to the symptomatic state, leading to detectable salivary gland hypertrophy (SGH +) syndrome. In this study, we investigated the interplay between the bacterial symbiome and GpSGHV during development of G. pallidipes by knocking down the symbionts with antibiotic. Intrahaemocoelic injection of GpSGHV led to high virus titre (10 9 virus copies), but was not accompanied by either the onset of detectable SGH + , or release of detectable virus particles into the blood meals during feeding events. When the F 1 generations of GpSGHV-challenged mothers were dissected within 24 h post-eclosion, SGH + was observed to increase from 4.5% in the first larviposition cycle to .95% in the fourth cycle. Despite being sterile, these F 1 SGH + progeny mated readily. Removal of the tsetse symbiome, however, suppressed transgenerational transfer of the virus via milk secretions and blocked the ability of GpSGHV to infect salivary glands of the F 1 progeny. Whereas GpSGHV infects and replicates in salivary glands of developing pupa, the virus is unable to induce SGH + within fully differentiated adult salivary glands. The F 1 SGH + adults are responsible for the GpSGHV-induced colony collapse in tsetse factories. Our data suggest that GpSGHV has co-evolved with the tsetse symbiome and that the symbionts play key roles in the virus transmission from mother to progeny.
    PLoS ONE 04/2013; 8(4):e61150. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The importance of host-specialization to speciation processes in obligate host-associated bacteria is well known, as is also the ability of recombination to generate cohesion in bacterial populations. However, whether divergent strains of highly recombining intracellular bacteria, such as Wolbachia, can maintain their genetic distinctness when infecting the same host is not known. We first developed a protocol for the genome sequencing of uncultivable endosymbionts. Using this method, we have sequenced the complete genomes of the Wolbachia strains wHa and wNo, which occur as natural double infections in Drosophila simulans populations on the Seychelles and in New Caledonia. Taxonomically, wHa belong to supergroup A and wNo to supergroup B. A comparative genomics study including additional strains supported the supergroup classification scheme and revealed 24 and 33 group-specific genes, putatively involved in host-adaptation processes. Recombination frequencies were high for strains of the same supergroup despite different host-preference patterns, leading to genomic cohesion. The inferred recombination fragments for strains of different supergroups were of short sizes, and the genomes of the co-infecting Wolbachia strains wHa and wNo were not more similar to each other and did not share more genes than other A- and B-group strains that infect different hosts. We conclude that Wolbachia strains of supergroup A and B represent genetically distinct clades, and that strains of different supergroups can co-exist in the same arthropod host without converging into the same species. This suggests that the supergroups are irreversibly separated and that barriers other than host-specialization are able to maintain distinct clades in recombining endosymbiont populations. Acquiring a good knowledge of the barriers to genetic exchange in Wolbachia will advance our understanding of how endosymbiont communities are constructed from vertically and horizontally transmitted genes.
    PLoS Genetics 04/2013; 9(4):e1003381. · 8.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A study on the phylogenetic relationships of aphids (Hemiptera: Aphididae) from different regions of Greece, has been carried out using fragments of cytochrome c oxidase I (COI) and 12S rRNA genes. Species belonging in Aphidinae, Chaitophorinae, Lachninae, Calaphidinae and Eriosomatinae subfamilies were included in our survey, although the majority is classified within the Aphidini and Macrosiphini tribes. Based on our data, estimated genetic divergence ranged from 1.3% to 15.5% with Cinara tujafilina (Lachninae) being the most distant species. Neighbour-Joining (NJ), maximum parsimony (MP) and Bayesian inference analysis (BI) phylogenetic trees showed a similar topology, which was compatible with the currently accepted systematic classification of aphids at the subfamily and tribe-subtribe level. Positioning of C. tujafilina as basal group in the dendrogram indicates the early separation of Lachninae from the other aphid species studied. Moreover a sistership relationship between the Aphidina and Rhopalosiphina subtribes was also observed in the dendrogram, although the monophyly of the genus Rhopalosiphum has not been resolved. Aphis nerii and Toxoptera aurantii, positioned at the basal node of the Aphidini-Aphidina cluster, apart from the rest of the Aphis species, while within this genus some groupings include species with similar morphological characteristics. Finally, the Macrosiphini group was also monophyletic; however within this group, there were several polytomies which might reflect cryptic or convergent morphological differences. Our results corroborate the findings of previous studies based on molecular data; however, there are still unresolved issues which need further clarification in order to fully understand this family’s complex phylogeny.
    Journal of Biological Research 01/2013; 20. · 0.62 Impact Factor
  • Source
    Spyridon Ntougias, Kostas Bourtzis, George Tsiamis
    [Show abstract] [Hide abstract]
    ABSTRACT: Olive mill wastes (OMWs) are high-strength organic effluents, which upon disposal can degrade soil and water quality, negatively affecting aquatic and terrestrial ecosystems. The main purpose of this review paper is to provide an up-to-date knowledge concerning the microbial communities identified over the past 20 years in olive mill wastes using both culture-dependent and independent approaches. A database survey of 16S rRNA gene sequences (585 records in total) obtained from olive mill waste environments revealed the dominance of members of Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Actinobacteria. Independent studies confirmed that OMW microbial communities' structure is cultivar dependant. On the other hand, the detection of fecal bacteria and other potential human pathogens in OMWs is of major concern and deserves further examination. Despite the fact that the degradation and detoxification of the olive mill wastes have been mostly investigated through the application of known bacterial and fungal species originated from other environmental sources, the biotechnological potential of indigenous microbiota should be further exploited in respect to olive mill waste bioremediation and inactivation of plant and human pathogens. The implementation of omic and metagenomic approaches will further elucidate disposal issues of olive mill wastes.
    BioMed research international. 01/2013; 2013:784591.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ankyrin repeat domain-encoding genes are common in the eukaryotic and viral domains of life, but they are rare in bacteria, the exception being a few obligate or facultative intracellular Proteobacteria species. Despite having a reduced genome, the arthropod strains of the alphaproteobacterium Wolbachia contain an unusually high number of ankyrin repeat domain-encoding genes ranging from 23 in wMel to 60 in wPip strain. This group of genes has attracted considerable attention for their astonishing large number as well as for the fact that ankyrin proteins are known to participate in protein-protein interactions, suggesting that they play a critical role in the molecular mechanism that determines host-Wolbachia symbiotic interactions. We present a comparative evolutionary analysis of the wMel-related ankyrin repeat domain-encoding genes present in different Drosophila-Wolbachia associations. Our results show that the ankyrin repeat domain-encoding genes change in size by expansion and contraction mediated by short directly repeated sequences. We provide examples of intra-genic recombination events and show that these genes are likely to be horizontally transferred between strains with the aid of bacteriophages. These results confirm previous findings that the Wolbachia genomes are evolutionary mosaics and illustrate the potential that these bacteria have to generate diversity in proteins potentially involved in the symbiotic interactions.
    PLoS ONE 01/2013; 8(2):e55390. · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The kinetics of hexavalent chromium bio-reduction in draw-fill suspended and attached growth reactors was examined using sugar as substrate and indigenous microorganisms from the industrial sludge of the Hellenic Aerospace Industry. Initially, experiments in suspended growth batch reactors for Cr (VI) concentrations of 1.4-110 mg/l were carried out, to extensively study the behaviour of a mixed culture. The maximum Cr(VI) reduction rate of 2 mg/l h was achieved for initial concentration 12.85 mg/l with biomass production rate 4.1 mg biomass/l h. Analysis of the microbial structure in the batch reactor culture indicated that the dominant bacterial communities were constituted by bacterial members of Raoultella sp., Citrobacter sp., Klebsiella sp., Salmonella sp., Achromobacter sp. and Kerstersia sp. while the dominant fungal strain was that of Pichia jadinii. Experiments using the same mixed culture were also carried out in packed-bed reactors with plastic support media. High removal rates were achieved (2.0 mg/l h) even in high initial concentrations (109 mg/l). A combination of the model of Tsao and Hanson for growth enhancement and that of Aiba and Shoda for growth inhibition was used in order to describe and predict the process of Cr(VI) bio-reduction in suspended growth and packed-bed reactors. Kinetic constants of the equation obtained from both batch (or draw-fill) culture experiments. In the draw-fill experiments at the packed-bed reactor, hexavalent chromium inhibitory effects were minimized increasing the inhibitory constant value K(i)(') at 148.5 mg/l, compared to suspended growth experiments which was K(i) = 8.219 mg/l. The model adequately predicts hexavalent chromium reduction in both batch reactors for all initial concentrations tested.
    Water Research 11/2012; · 4.66 Impact Factor

Publication Stats

2k Citations
363.68 Total Impact Points

Institutions

  • 2013–2014
    • University of Patras
      • Department of Environmental and Natural Resources Management
      Rhion, West Greece, Greece
    • International Atomic Energy Agency (IAEA)
      Wien, Vienna, Austria
  • 2012–2014
    • University of Western Greece
      Agrínio, West Greece, Greece
    • N.AG.RE.F. - NATIONAL AGRICULTURAL RESEARCH FOUNDATION
      Megalokastro, Crete, Greece
  • 2011–2012
    • Biomedical Sciences Research Center Alexander Fleming
      Βάρη, Attica, Greece
  • 2004–2012
    • University of Crete
      • School of Medicine
      Retimo, Crete, Greece
  • 1970–2012
    • University of Ioannina
      • Department of Environmental and Natural Resources Management
      Ioánnina, Ipeiros, Greece
  • 2010
    • Bielefeld University
      Bielefeld, North Rhine-Westphalia, Germany
    • Università degli Studi di Modena e Reggio Emilia
      Modène, Emilia-Romagna, Italy
  • 2009
    • Aristotle University of Thessaloniki
      • Department of Genetics, Development and Molecular Biology
      Thessaloníki, Kentriki Makedonia, Greece
    • Technological Educational Institute of Crete
      Megalokastro, Crete, Greece
  • 2004–2009
    • University of Pavia
      • Department of Biology and Biotechnology "Lazzaro Spallanzani"
      Ticinum, Lombardy, Italy
  • 2008
    • Vanderbilt University
      Nashville, Michigan, United States
  • 1999–2001
    • Yale-New Haven Hospital
      New Haven, Connecticut, United States
  • 1994
    • Institute of Genetics and Molecular Medicine
      Edinburgh, Scotland, United Kingdom