43. "Grecocyclines: New Angucyclines from Streptomyces sp. Acta 1362."
T. Paululat, A. Kulik, H. Hausmann, A.D. Karagouni, H. Zinecker, J.F. Imhoff and H.P. Fiedler.
European Journal of Organic Chemistry, vol. 12, pages 2344-2350, (2010).  View at publisher's site  Request copy
Abstract: Two novel angucyclines were isolated from the streptomycete Acta 1362. The strain was of particular interest regarding the production of characteristic metabolites that were detected by HPLC–diode array profiling of the extracts. Grecocycline A and B were isolated and their structures were determined. Grecocycline A shows cytotoxic activity and grecocycline B inhibits protein tyrosine phosphatase 1B. Moreover, shunt product grecocyline C was isolated and its structure was determined.

42. "The use of trpB gene in resolving phylogenetic diversity within the group of Streptomyces."
C. Meintanis, K.I. Chalkou, K.A. Kormas, D.S. Lymperopoulou, E.A. Katsifas and A.D. Karagouni.
Current Trends in Microbiology, vol. 5, pages 37-46, (2009).  View at publisher's site  Request copy
Abstract: In the present work, we investigated the ability of trpB gene, which encodes a primary metabolism enzyme involved in the tryptophan synthesis, to be used as an alternative to 16S rRNA for sequence similarity analysis in the Actinobacteria group. trpB DNAs (504 bp) were amplified from 13 Actinobacteria type strains, in addition to 24 environmental streptomycete isolates with different BOX-PCR profiles. The sequences and the phylogenetic tree of trpB were compared to those obtained from 16S rRNA gene analysis, for the total of the examined bacteria. The results demonstrated between 93 – 100 % (16S rRNA) and 86 – 100 % (trpB) similarity among the examined bacteria of the genus Streptomyces and suggested that trpB sequence similarity analysis allows a more accurate discrimination of the species within Streptomyces genus than the more commonly used 16S rRNA. Furthermore, DGGE analysis was also applied in habitats which exhibit a high degree of streptomycete diversity. The biodiversity patterns produced led to similar estimation of diversity, whether using 16S Actinobacteria group specific primers or the trpB novel primers. In conclusion, our study suggested that trpB sequence similarity analysis is a powerful tool for discrimination between species within the ecologically and industrially important strains of Streptomyces genus.

41. "Prevalence of tetracycline resistance gene in Greek seawater habitats."
T.L. Nikolakopoulou, E.P. Giannoutsou, A.A. Karabatsou and A.D. Karagouni.
The Journal of Microbiology, vol. 46, pages 633-640, (2008).  View at publisher's site  Request copy
Abstract: The presence of selected tetracycline resistance (TcR) genes was studied in different Greek seawater habitats, originated from wastewater treatment facilities, fishfarm, and coastal environments. The methods employed included assessment of the presence of twelve gene clusters by PCR, followed by hybridization with specific probes, in habitat extracted DNA, Tc(R) bacteria, and exogenous isolated plasmids conferring TcR. The direct DNA-based analysis showed that tet(A) and tet(K) genes were detected in all habitats, whilst tet(C) and tet(E) were present in fishfarm and wastewater effluent samples and tet(M) was detected in fish-farm and coastal samples. Resistance genes tet(A), tet(C), tet(K), and tet(M) were detected in 60 of the 89 isolates screened. These isolates were identified by fatty acid methyl ester analysis (FAME) as Stenotrophomonas, Acinetobacter, Pseudomonas, Bacillus, and Staphylococcus strains. The presence of the TcR genes in 15% of the bacterial isolates coincided with the presence of IncP plasmids. A habitat-specific dissemination of IncP alpha plasmids in wastewater effluent isolates and of IncP beta plasmids in fishfarm isolates was observed. Exogenous isolation demonstrated the presence of plasmids harbouring Tc(R) genes in all the habitats tested. Plasmids were shown to carry tet(A), tet(C), tet(E), and tet(K) genes. It is concluded that TcR genes are widespread in the seawater habitats studied and often occur on broad host range plasmids that seem to be well disseminated in the bacterial communities.

40. "Purification and partial characterization of the xanthine-uric acid transporter (UapA) of Aspergillus nidulans".
N. D. Lemuh, G. Diallinas, S. Frillingos, G. Mermelekas, A. D. Karagouni and D. G. Hatzinikolaou.
Protein Expression and Purification, vol. 63, pages 33-39, (2009).  View at publisher's site  Request copy
Abstract: UapA, the uric acid-xanthine permease from the filamentous ascomycete Aspergillus nidulans, is one of the most thoroughly characterized purine/H⁺ transporters in eukaryotes. Detailed studies have addressed its regulation of expression, at both the transcriptional and post-translational levels, in response to physiological and developmental signals. An extensive kinetic profile towards a plethora of purines and mutational analyses have established models on how UapA recognizes the purine ring and revealed specific amino acid residues involved in proper folding, topogenesis, function and specificity. The present work describes for the first time the purification of the UapA transporter of A. nidulans through overexpression via the strong, ethanol-inducible, glucose-repressible, alcA promoter. Purification, almost to homogeneity, was achieved by Ni²⁺ affinity chromatography using a functional His-tagged UapA protein version. It is subsequently shown, by Circular Dichroism (CD) spectroscopy, that the purified protein is structured with a high α-helical content, as expected from the in silico predictions. The result of this work opens the way for further, analytical and biochemical studies on UapA at the protein level.

39. "A refinery sludge deposition site: presence of nahH and alkJ genes and crude oil biodegradation ability of bacteria isolates."
N. Arvanitis, E.A. Katsifas, K.I. Chalkou, C. Meintanis and A.D. Karagouni.
Biotechnology Letters, vol. 30, pages 2105-2110, (2008).  View at publisher's site  Request copy
Abstract: 204 bacterial isolates from four Greek refinery sludge deposition sites were investigated for the presence of nahH and alkJ genes encoding key enzymes of both aromatic and aliphatic hydrocarbon degradation pathways by PCR and DNA hybridisation. Members of Pseudomonas, Acinetobacter, Bacillus, Rhodococcus and Arthrobacter play important role in bioremediation processes in sandy/loam soil contaminated with oil and nahH and alkJ genes were present in the 73% of the isolates. Consortia of bacterial isolates that were used for biodegradation of aliphatic and aromatic hydrocarbons in crude oil using liquid cultures exhibited rates from 35% to 48% within 10 days of incubation.

38. "Grecoketides A and B, new naphthoquinones from Streptomyces sp. Acta 1362."
T. Paululat, E.A. Katsifas, A.D. Karagouni and H.P. Fiedler.
European Journal of Organic Chemistry, vol. 31, pages 5283-5288, (2008).  View at publisher's site  Request copy
Abstract: Two novel naphthoquinones were produced by the streptomycete Acta 1362. It was determined by HPLC/diode-array screening that freshly isolated actinomycete strains from selected European ecosystems produce new compounds. Grecoketides A and B were isolated and their structures determined. Both compounds have the same aglycon grecoketidone with a sugar side-chain that differs in one of the two attached sugar units. Moreover, the biosynthesis of grecoketidone was studied by feeding singly and fully labelled acetate. The hexaketide formed is cyclized after s-mode folding.

37. "Application of rpoB sequence similarity analysis, REP-PCR and BOX-PCR for the differentiation of species within the genus Geobacillus".
C. Meintanis, K. I. Chalkou, K. A. Kormas, D. S. Lymperopoulou, E. A. Katsifas, D. G. Hatzinikolaou and A. D. Karagouni.
Letters in Applied Microbiology, vol. 46, pages 395-401, (2008).  View at publisher's site  Request copy
Abstract: AIM: To investigate the applicability of rpoB gene, which encodes the β-subunit of RNA polymerase, to be used as an alternative to 16S rRNA for sequence similarity analysis in the thermophilic genus Geobacillus. Rapid and reproducible repetitive extragenic palindromic fingerprinting techniques (REP- and BOX-polymerase chain reaction) were also used. METHODS AND RESULTS: rpoB DNA (458 bp) were amplified from 21 Geobacillus- and Bacillus type strains, producing different BOX- and REP-PCR profiles, in addition to 11 thermophilic isolates of Geobacillus and Bacillus species from a Santorini volcano habitat. The sequences and the phylogenetic tree of rpoB were compared with those obtained from 16S rRNA gene analysis. The results demonstrated between 90–100% (16S rRNA) and 74–100% (rpoB) similarity among examined bacteria. CONCLUSION: BOX- and REP-PCR can be applied for molecular typing within Geobacillus genus. rpoB sequence similarity analysis permits a more accurate discrimination of the species within the Geobacillus genus than the more commonly used 16S rRNA. SIGNIFICANCE AND IMPACT OF THE STUDY: The obtained results suggested that rpoB sequence similarity analysis is a powerful tool for discrimination between species within the ecologically and industrially important strains of Geobacillus genus.

36. "Effect of ionising radiattion on the quantification of genetically modified foods."
A.M. Batrinou, D. Koraki, V.J. Sinanoglou, A.D. Karagouni, K. Sflomos and V. Pletsa.
Food Biotechnology, vol. 22, pages 338-351, (2008).  View at publisher's site  Request copy
Abstract: The rapid spread of Genetically Modified (GM) crops globally and the mandatory labeling of GM food and feed imposed by many countries has led to the development of relevant detection techniques. Polymerase Chain Reaction (PCR) – based methods are presently the most effective and reliable for GM detection even in processed food products. This study evaluated the effect of electron beam irradiation, used for food pasteurization, on the detection and quantification of dry GM soyabean and maize products; qualitative and quantitative (real-time TaqManTM probe) PCR analysis showed that electron beam irradiation treatment, even at a high dose (10 kGy), did not affect the traceability of transgenes.

35. "Fluostatins C~E, novel members of the fluostatin family produced by Streptomyces strain Acta 1383."
S. Baur, J. Niehaus, A.D. Karagouni, E.A. Katsifas, K. Chalkou, C. Meintanis, A.L. Jones, M. Goodfellow, A.C. Ward, W. Beil, K. Schneider, R.D. Süssmuth and H.P. Fiedler.
Journal of Antibiotics, vol. 59, pages 293-297, (2006).  View at publisher's site  Request copy
Abstract: Three new members of the fluostatin family, fluostatins C-E, were discovered in a culture filtrate extract of strain Acta 1383 during an HPLC screening program. The producing strain belongs to the genus Streptomyces and is closely related to type strains classified in the Streptomyces lavendulae 16S rRNA subclade. Fluostatins are named by their characteristic fluorenone chromophore. Fluostatin C shows moderate activity against selected human tumor cell lines.

34. "Biodegradation of Crude Oil by Thermophilic Bacteria Isolated from a Volcano Island."
C. Meintanis, K. Chalkou, K.A. Kormas and A.D. Karagouni A.D..
Biodegradation, vol. 17, pages 105-111, (2006).  View at publisher's site  Request copy
Abstract: One-hundred and fifty different thermophilic bacteria isolated from a volcanic island were screened for detection of an alkane hydroxylase gene using degenerated primers developed to amplify genes related to the Pseudomonas putida and Pseudomonas oleovorans alkane hydroxylases. Ten isolates carrying the alkJ gene were further characterized by 16s rDNA gene sequencing. Nine out of ten isolates were phylogenetically affiliated with Geobacillus species and one isolate with Bacillus species. These isolates were able to grow in liquid cultures with crude oil as the sole carbon source and were found to degrade long chain crude oil alkanes in a range between 46.64% and 87.68%. Results indicated that indigenous thermophilic hydrocarbon degraders of Bacillus and Geobacillus species are of special significance as they could be efficiently used for bioremediation of oil-polluted soil and composting processes. .