Nevin Keskin

Diversity and distribution of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) in Turkey

The diversity and distribution of entomopathogenic nematodes in thefamilies Steinernematidae and Heterorhabditidae were assessed throughout anextensive soil survey in Turkey during 1999 and 2000. Entomopathogenic nematodeswere recovered from six out of seven regions sampled, with 22 positive sites(2%) out of 1080 sites sampled. A single nematode isolate was recovered at eachof the positive sites, of which 15 were steinernematid isolates and seven wereheterorhabditid isolates representing a total of four species. Based onmorphometric and molecular data, the nematode species were identified asHeterorhabditis bacteriophora, Steinernemafeltiae, S. affine, andSteinernema n. sp. The most common species was S.feltiae, which was isolated from 10 sites in six regions, followed byH. bacteriophora from seven sites in five regions,S. affine from four sites in two regions, andSteinernema n. sp. from one site. Heterorhabditisbacteriophora and S. feltiae have been found inmany parts of the world, whereas S. affine, so far, hasonly been recovered in Europe until our survey. Steinernemaaffine was isolated from the European (Marmara) as well as theAsiatic region (Middle Anatolia) of Turkey. A new undescribedSteinernema sp. was isolated from the most eastern region(East Anatolia) of Turkey. Soils of the positive sites were classified as sandy,sandy loam, or loam (68.2%) and sandy–clay–loam or clay loam (31.8%) and the pHranged from 5.6 to 7.9. The habitats from which the entomopathogenic nematodeswere isolated were broadly classified as disturbed (59.1%), which includedagricultural fields and poplar planted for lumber and wind breaks, andundisturbed (40.9%), which included pine forest, grassland, marsh and reed sites.Steinernema feltiae, S. affine, andH. bacteriophora were recovered from both disturbed andundisturbed habitats. The new Steinernema sp. was recoveredfrom grassland. Our survey showed that these nematodes occur widely throughoutTurkey, but at a frequency below that reported for other parts of the world.

Theoretical investigation of quercetin and its radical isomers

The structural and electronic properties of quercetin and its five radical isomers have been investigated theoretically by performing semi-empirical molecular orbital theory calculations. The geometry of the systems have been optimized and the electronic properties of the systems considered have been calculated by semi-empirical self-consistend-field molecular orbital theory at the level AM1 within UHF formalism in their ground state. Conclusions have been drawn by comparing with experimental results.

Two new subspecies of Photorhabdus luminescens, isolated from Heterorhabditis bacteriophora (Nematoda: Heterorhabditidae): Photorhabdus luminescens subsp. kayaii subsp. nov. and Photorhabdus luminescens subsp. thracensis subsp. nov.

Bacterial isolates from nematodes from Turkish soil samples were initially characterized by molecular methods and seven members of the genus Photorhabdus identified to the species level, using riboprint analyses and metabolic properties. Strain 07-5 (DSM 15195) was highly related to the type strain of Photorhabdus luminescens subsp. laumondii DSM 15139T, and was regarded a strain of this subspecies. Strains 1121T (DSM 15194T), 68-3 (DSM 15198) and 47-10 (DSM 15197) formed one, strain 39-8T (DSM 15199T), 39-7 (DSM 15196) and 01-12 (DSM 15193) formed a second cluster that branched intermediate the three subspecies of Photorhabdus luminescens. Based upon moderate 16S rRNA gene sequence similarities and differences in metabolic properties among themselves and with type strains of the three subspecies we consider the two clusters to represent two new subspecies of Photorhabdus luminescens for which the names Photorhabdus luminescens subsp. kayaii, type strain 1121T (DSM 15194T, NCIMB 13951T), and Photorhabdus luminescens subsp. thracensis subsp. nov., type strain 39-8T (DSM 15199T, NCIMB 13952T) are proposed.

Antibacterial Activity and Chemical Composition of Turkish Propolis

Abstract The antibacterial activities of propolis samples have been examined in vitro, according to the principles accepted for the determination of a similar activity of antibiotics with the use of solid and liquid media. It has been found that propolis extracts showed antibacterial activity through a range of commonly encountered gram positive cocci (5. aureus, beta hem. Streptococus), but had weak activity against gram negative bacteria (E . coli, P. aeruginosa). GC/MS analysis showed that propolis samples contain a variety of chemical compounds in cluding aromatic compounds, fatty acid esters and sesquiterpenes.

Diversity and distribution of nematodes associated with wild bees in Turkey.

The diversity and distribution of nematodes associated with soil-dwelling bees in Turkey were examined. A total of 9456 wild bees were collected and dissected to detect nematodes and 173 female and 22 male bees were positive for an overall association level of 2.1%. Halictus resurgens was the most commonly collected bee found with nematodes with 82 and 19 nematode-infested female and male bees, respectively. Sixty-four of the nematode isolates were recovered from the Black Sea region (32.8%), 59 from Central Anatolia (30.3%), 35 from the Mediterranean (17.9%), 24 from the Aegean (12.3%), six from Eastern Anatolia (3.1%) and seven from Southeast Anatolia (3.6%). In 3.9% of all bees of the family Halictidae (173/4417), nematodes were observed in the Dufours gland, poison sac, oviduct, bursa copulatrix and abdominal cavity of dissected female bees and from the genital capsule of male bees. Only abdominal glands of 0.6% (21/3279) of female bees from the family Andrenidae were observed with nematodes. Nematodes were isolated from the genital capsule of one male bee from the family Melittidae. The poison sac was the organ where nematodes were most often observed but the highest number of nematodes occurred in the abdominal cavity. Most nematodes were in the dauer juvenile stage making identification difficult. Sequence analysis using LSU D2/D3 domains and a fragment of mitochondrial cytochrome oxidase I (mtCOI) allowed for putative identification of nematode isolates. Two or three species of Bursaphelenchus ( B. anatolius , B. debrae , and potentially one or more cryptic species closest in morphology to B. anatolius ) were isolated from six different halictid species (two genera; Halictus and Lasioglossum ) from different geographical regions in Turkey. An additional four species of diplogastrid were recovered from the abdominal glands of andrenids; a new species of Koerneria from Andrena limata and a separate sister clade to Mononchoides composed of three other possible species from four Andrena species. An additional unknown species in the order Tylenchida (near Allantonematinae) was recovered from three species of Lasioglossum . No molecular data were obtained from three mermithid juveniles from two Andrena and one Halictus species because samples were lost in transit. The associations of most nematode isolates with bees of the families Halictidae and Andrenidae were hypothesised to be phoretic, whereas the tylenchid and mermithids were parasites.

Evaluation of some essential oils as alternative antibiotics against American foulbrood agent Paenibacillus larvae on honey bees Apis mellifera L

In this study, antibacterial activities of some essential oils against Paenibacillus larvae were investigated as an alternative to synthetic antibiotics used against American foulbrood (AFB), which causes serious damage to the beekeeping industry. Ten essential oils belonging to various species and carvacrol, the major component of Origanum onites oil, were analyzed. Besides examining the antibacterial activities of the essential oils in the experiments, composition of the oils was investigated by gas chromatography (GC) and GC–mass spectroscopy (GC–MS) analysis. The minimum inhibition concentrations (MICs) of the effective essential oils were also determined. The conclusions resulting from these observations were that Origanum onites oil showed the strongest antibacterial activity. Rosmarinus officinalis, Seseli andronakii, Pimpinella anisum, Heracleum platytaenium, Anethum graveolens, Bifora radians, and Seseli tortuosum were respectively found to be effective coming after Origanum onites. Seseli petraeum and Seseli resinosum, two different species within the same genus showed no antibacterial activity against AFB. The results show that composition of the essential oils is very important for antibacterial effect; in fact antibacterial effect is determined by the major component in the essential oil composition. However, intercomponent synergetic effect is as important as the major component itself according to the results of carvacrol experiments.

Theoretical investigation of hydroxytyrosol and its radicals

Abstract The structural and electronic properties of hydroxytyrosol, its three radical isomers, and its three analogues hydroxytyrosol-dihydroxyl isomers have been investigated theoretically by performing semi-empirical self-consistent field molecular orbital theory calculations. The geometry of the systems have been optimized and the electronic properties have been calculated at the level of AM1 method.

Molecular variability of Schistonchus caprifici (Nematoda: Aphelenchoididae) from Ficus carica in Turkey

An extensive biogeographical survey was conducted from 2004 through part of 2007 of nematodes associated with the edible fig, Ficus carica, in seven different regions of Turkey. Figs (syconia) were collected, dissected and harvested for nematodes from 308 apparently wild or naturalised F. carica trees along roadsides and trails. Nematode specimens were examined morphologically and molecular analyses of sequences of the D2/D3 expansion segments of the large subunit (LSU) rDNA and partial mitochondrial DNA COI (mtCOI) were done. Of the 308 fig trees, 150 (49%) were positive for what was morphologically confirmed to be Schistonchus caprifici. Figs on one tree in Kahramanmaras city, South East Turkey, were found to contain S. caprifici and dauer juveniles of what appears to be a diplogastrid nematode. Molecular analyses produced congruent trees for both sequenced loci supporting the hypothesis that S. caprifici from different locations in Turkey are part of a well supported clade with some inherent variability. No geographic patterns were observed for either locus suggesting that the sequences generated represent inherent intraspecific variation for S. caprifici and that human activities related to the culture of the edible fig have allowed for mixing of any previously allopatric lineages.

Bursaphelenchus debrae n. sp. (Nematoda: Parasitaphelenchidae), an associate of the bee Halictus brunnescens in Turkey

Bursaphelenchus species are mostly known as phoretic associates of bark beetles (Scolytidae), weevils (Curculionidae) and longhorn beetles (Cerambycidae), but a few other insects are known as vectors and there are several species that have not yet been linked to a host. During a 2-year field survey of soil-dwelling bees from several geographical regions in Turkey, a mycophagous species of Bursaphelenchus was recovered and cultured from an adult female of Halictus brunnescens Eversmann from Ankara, Turkey. Sixty entomophilic dauer juveniles were observed in the poison sac of this bee. Halictus brunnescens is a member of the subgenus Halictus Latreille which is widely distributed in the Palaearctic region and

Theoretical investigation of melatonin and its hydroxy isomers

The structural and electronic properties of melatonin and its six hydroxy isomers have been investigated theoretically by performing semi-empirical and ab initio molecular orbital theory calculations. The geometry of the systems has been optimized considering the semi-empirical molecular orbital theory at the level of AM1, and the electronic properties of the systems have been calculated by ab initio RHF including full MP2 correlation correction in their ground state. Conclusions were drawn by comparing with experimental results.