SENTIMENT ANALYSIS IN SOCIAL NETWORKS USING NAiVE BAYES ALGORITHM

This report is concerned with the opinion mining and sentiment analysis in social networks especially Twitter, it aims to give a brief insight into the ongoing research in sentiment analysis algorithms and techniques, and graphical representation of the statistical results by applying the sentiment analysis on social networks. The objectives of this project is to perform a detailed research on the latest techniques in the process, and to enhance the current approaches of sentiment analysis by building a tool with an ability to provide statistical information, graphically represented -to an acceptable degree of accuracy- to show the collective consciousness of Internet users. The implementation of this project will most probably use third party tools available on the web to reduce time needed and for rapid prototyping in the initial stages of implementation

Static Hovering Realization for Multirotor Aerial Vehicles with Tiltable Propellers

This paper presents a theoretical study on the ability of multi-rotor aerial vehicles (MRAVs) with tiltable propellers to achieve and sustain static hovering at different orientations. To analyze the ability of MRAVs with tiltable propellers to achieve static hovering, a novel linear map between the platform's control inputs and applied forces and moments is introduced. The relation between the introduced map and the platform's ability to hover at different orientations is developed. Correspondingly, the conditions for MRAVs with tiltable propellers to realize and sustain static hovering are detailed. A numerical metric is then introduced, which reflects the ability of MRAVs to sustain static hovering at different orientations. A subclass of MRAVs with tiltable propellers is defined as the Critically Statically Hoverable platforms (CSH), where CSH platforms are MRAVs that cannot sustain static hovering with fixed propellers, but can achieve static hovering with tilting propellers. Finally, extensive simulations are conducted to test and validate the above findings, and to demonstrate the effect of the proposed numerical metric on the platform's dynamics

SENTIMENT ANALYSIS IN SOCIAL NETWORKS USING NAiVE BAYES ALGORITHM

This report is concerned with the opinion mining and sentiment analysis in social networks especially Twitter, it aims to give a brief insight into the ongoing research in sentiment analysis algorithms and techniques, and graphical representation of the statistical results by applying the sentiment analysis on social networks. The objectives of this project is to perform a detailed research on the latest techniques in the process, and to enhance the current approaches of sentiment analysis by building a tool with an ability to provide statistical information, graphically represented -to an acceptable degree of accuracy- to show the collective consciousness of Internet users. The implementation of this project will most probably use third party tools available on the web to reduce time needed and for rapid prototyping in the initial stages of implementation

Emotional Intelligence and Its Relation to the Professional Competence of Lecturers Working in Palestinian Universities

The aim of the study was to identify the relationship between professional competence and emotional intelligence among lecturers working at Al-Aqsa University. Another aim was to identify the level of professional competence and emotional intelligence in the study sample. The results of the study revealed that the level of professional competence and emotional intelligence was high among Al-Aqsa University professors. Besides, the results of the study showed a positive relationship between professional competence and emotional intelligence in the study sample. It was also found that there were no differences due to sex in both professional competence and emotional intelligence of the university professors at Al-Aqsa University. Keywords: Emotional intelligence -professional efficiency

Effect of Gold Nanorods on the Performance of Polymer:Fullerene Organic Solar Cells

This research is an experimental investigation on the effect of inserting gold nanorods in various locations of conjugated polymer solar cells that comprise poly(3-hexylthiophene-2,5-diyl) as the electron donor, and [6,6]-phenyl-C61-butyric-acid-methyl-ester as the electron acceptor, on the cells performance. Since gold nanorods support at least two major plasmonic modes associated with metallic nanoparticles, incorporating such nanoparticles into thin films of polymer solar cells is supposed to trap light inside the cells in a broad wavelength range, leading to increasing absorptivity as well as power conversion efficiency. First, several experiments were performed to manufacture devices with a good and reproducible efficiency by optimizing the fabrication conditions, particularly the lithium fluoride thickness as well as the annealing process. This optimization succeeded in producing reproducible devices with an enhanced power conversion efficiency from 0.36% to 1.67%. Secondly, various approaches were used to introduce gold nanorods in our devices. Rods were deposited in contact with either the cells’ front electrode, or the rear one. They were also blended with the solution of the anodic buffer layer, or the one of the photoactive layer. We compared the photovoltaic parameters extracted from completed devices made with/without gold nanorods, as well as their spectroscopic and structure properties. We found that for each location of rods in our devices there was an optimal concentration of the rods to produce enhancement in the devices’ performance. Based on theoretical considerations, devices enhancement was related to either the far field or near field effect induced by the presence of rods. It was found that increasing or decreasing the rods density from the optimal one reduced the overall efficiency of resulting devices. We experimentally verified that there was a relationship between the enhancement in the devices efficiency and the multi-mode excitations associated with gold nanorods. We also found that the influence of plasmonics on absorption of the devices depended on the thickness of the devices’ photoactive layers. Using the rod shape of gold nanoparticles to increase the device performance is indeed a promising approach since a fairly low density of the rods in the layer succeeded in increasing remarkably the devices efficiency by up to 21.3 %

Signature-based Tree for Finding Frequent Itemsets

The efficiency of a data mining process depends on the data structure used to find frequent itemsets. Two approaches are possible: use the original transaction dataset or transform it into another more compact structure. Many algorithms use trees as compact structure, like FP-Tree and the associated algorithm FP-Growth. Although this structure reduces the number of scans (only 2), its efficiency depends on two criteria: (i) the size of the support (small or large); (ii) the type of transaction dataset (sparse or dense). But these two criteria can generate very large trees. In this paper, we propose a new tree-based structure that emphasizes on transactions and not on itemsets. Hence, we avoid the problem of support values that have a negative impact on the generated tree

Combustion performance of a two-layer porous inert medium burner at different low powers

Abstract- Improving the performance of modern combustion systems in many engineering application fields has great favorable impact on the energy conservation and global environmental pollution. This can be done through developing state of the art techniques for this purpose. One of them is the combustion within porous media burners. The two-layer porous inert medium burner (PIM) has significant merits such as high burning ratios, very low emission levels, high levels of the combustion stability, and operation at ultra-lean excess air ratios. The main work is to examine a new PIM design has a square cross-section area with two porous layers namely, aluminum oxide as the subcritical layer (quenching layer) and silicon carbide (SiC) as the supercritical layer each of 130 x 130 mm. The burner performance was estimated by recording the axial temperature profile at the selected operated thermal powers. The extent of the combustion stability limits between the flashback limit to the blow-off limit was improved. The excess air ratios of the stability limits at powers 0.7, 1.5, 2.5 kW were deduced to be (1.9-2.8), (1.8-2.6), and (1.5-2.4), respectively. The exhaust emissions were measured by a gas analyzer. The results revealed low levels of the CO emissions and decreased with increasing the operated thermal power. The CO ppm recorded the order of hundreds at powers 0.7 and 1.5 kW but reached the order of tens at power 2.5 kW. The NOx emission recorded ultra-low levels and increase with increasing the thermal power but not exceed 2 ppm

Molekulare Studien an Bakteriophagen des Lebensmittel-Starterbakteriums Streptococcus thermophilus

Lactic acid bacteria play divergent and important roles for human beings: On the one hand they include major bacterial pathogens like Streptococcus pyogenes and S. pneumoniae and on the other hand many species are used as starter cultures for the manufacture of fermented food (i.e., dairy products, meat, vegetables, wine, sour dough, cocoa) and silage. S. thermophilus is one of the most important lactic acid bacteria required for the manufacture of yogurt, mozzarella and other cheese varieties (e.g. Cheddar and Swiss-type cheeses). Bacteriophage attacks are always a serious problem in industrial fermentations leading to significant financial losses. Characterization of bacteriophage populations is therefore the first step of efficient phage control in dairies and other food fermentation industries. The aim of the work described in Chapter 1 was to identify and characterize a new temperate S. thermophilus phage (i.e., phage TP-778) that was induced from its lysogenic host strain S. thermophilus SK778. Phage TP-778 revealed the typical morphology of all known S. thermophilus phages with isometric heads and long non-contractile tails. It was classified as a pac-type phage with a genome size of ca. 44 kb. No prophage-cured strain could be obtained, indicating that correct excision of prophage DNA from the host chromosomal DNA was prevented. Phage TP-778 could be propagated lytically on the non-lysogenic S. thermophilus strain B106, and a lytically propagated derivative (i.e., TP-778L) was isolated and also characterised as described in this chapter. When phage TP-778 DNA was used as a probe for Southern blot analysis of the chromosomal DNAs of a set of non-lysogenic S. thermophilus strains, an unexpected high background of unspecific hybridization signals appeared in the DNAs of all strains. This indicated that the phage TP-778 genome could (1) either carry DNA homologous to the chromosomal DNA of S. thermophilus starter strains or (2) that the phage would be capable to package (and consequently transduce) chromosomal DNA during phage proliferation. In order to address these questions, a detailed DNA sequence analysis was performed for the lysogeny module of the phage genome and its flanking regions from the phage lysin gene to the phage cro regulatory protein gene. This genomic region was selected since it should reveal all genetic determinants for prophage integration/excision (i.e. integrase gene), for establishing the lysogenic/lytic phage life cycle (i.e., regulatory genes of the genetic switch) and furthermore the junction sites between prophage and bacterial DNA (i.e., attL and attR). The 2 neighbouring prophage regions from the left prohage/chromosome junction site (attL-site) to cro gene (fragment attL-cro) and from the lysin gene to the expected attR-site (fragment lysin-attR) located on the opposite flanking region of the prophage DNA were amplified by PCR and sequenced. Sequence analysis of the lysin-attR prophage DNA revealed the presence of about 1.9-kb prophage remnant DNA. A truncated 398-bp integrase gene was present on the phage remnant. A functional attR-site was also deleted from this prophage fragment, indicating that integration or excision of the prophage could not occur by the site-specific recombination via homologous attP and attB sites. Hence, this fragment was renamed as lysin-attR fragment. While only a non-functional (truncated) integrase was identified on the lysin-attR prophage fragment, a complete 1080-bp integrase gene was identified on the attL-cro DNA fragment. This core region of the TP-778 lysogeny module was highly homologous to the corresponding region of the well-characterized S. thermophilus temperate phage TP-J34 (Neve et al., 2003) and did also code for a unique lipoprotein (Orf142TP-778). Hence it was concluded that prophage TP-778 is directly associated with a prophage remnant in the lysogenic host strain. In order to confirm that TP-778 can package extra DNA, a 16S rDNA region was amplified from purified phage particles treated with DNase I to destroy any non-packaged chromosomal DNA contaminations. The positive PCR reaction was confirmed by Southern blot analysis using the 16S rDNA probe. It was concluded that phage TP-778 and its lytic derivative (TP-778L) were both capable of packaging chromosomal host DNA. The core region of the lysogeny module of lytically propagated phage derivative TP-778L was also analysed by DNA sequencing. Phage TP-778L contained a 398-bp truncated recombinant integrase gene remnant. By alignment with the intact 1080-bp integrase gene of phage TP-778 and with the 398-bp integrase gene fragment present on the prophage remnant, it was shown that the TP-778L integrase fragment exhibited a recombinant structure originating from a homologous recombination event between the two integrase determinants present in the lysogenic SK778 cells. In Chapter 2 comparisons of genes ltpTP-778 (orf142TP-778) of phage TP-778 and ltpTP-J34 (orf142TP-778) of phage TP-J34 and their corresponding gene products are presented. The lipoprotein gene ltpTP-778 of phage TP-778 is closely related to the corresponding gene ltpTP-J34 of phage TP-J34. Previously, ltpTP-J34 has been shown to code for a unique superinfection exclusion system. This phage resistance mechanism was also active in a lactococcal host background against the isometric-headed phage P008 but not aggainst the prolate-headed phage P001 (Sun et al., 2006). The amino acid sequences of both deduced lipoproteins differed only by 10 amino acids. The ltpTP-778 gene was cloned into the expression vector pMG36e. The resulting recombinant plasmid pYAL1 was also transformed into the Lactococcus lactis strain Bu2-60 in order to assess its effect of ltpTP-778 on the phage resistance phenotype of the cells. Gene expression of LtpTP-778 in strain Bu2-60 was confirmed by SDS-PAGE analysis, but the protein did not react with a polyclonal antiserum raised against LtpTP-J34 coded by phage TP-J34. When 3 Bu2-60(pYAL1) transformants were challenged with phages P008 and P001, 2 of them were partially resistant to phage P001 but not to phage P008. The 3rd transformant was still sensitive to both phages. The deviation of phage resistance phenotypes observed in Bu2-60 transformants harbouring the ltpTP-778 or the ltpTP-J34 gene was suggested to be due to the variability of one or more of the 10 amino acids that differ in the lipoproteins coded by ltpTP-778 and ltpTP-J34. Due to the high economical losses that may result from a phage infection of starter cultures, a rapid and sensitive method is required for phage detection and identification in the dairy. In Chapter 3, a rapid and reliable multiplex-PCR method is described allowing the simultaneous detection of S. thermophilus phages and their differentiation into the 2 well-known pac- and cos-type subgroups. Since pac- and cos-type phages are composed of different structural proteins, 2 sets of primers were designed from the internal highly conserved region of the major head protein gene of 8 completely sequenced S. thermophilus pac-type phages (TP-J34, O1205, Sfi11, 2972) and cos-type phages (Sfi21, 2701, Sfi19, DT1). The 2 primer sets could be used simultaneously in a multiplex PCR assay to detect and distinguish S. thermophilus phages, because the PCR-products differed in fragment size (432-bp product for pac-type phages versus 514-bp product of cos-type phages). The reliability of the multiplex PCR protocol was validated and confirmed by the following 3 controls: (I) restriction enzyme analysis of the DNA of cos- and pac-type DNA phages with and without a heating step at 74°C required for the melting of fragments harbouring cos-sites, (II) SDS-PAGE analysis of the structural proteins of pac-type phages (3 major bands) and cos-type phages (2 major bands), and furthermore by (III) immuno electron microscopy of the phages treated with a polyclonal antiserum raised against the pac-type phage TP-778. The multiplex PCR yielded results in a short time of approximately 2.5 h. The method is highly sensitive with a limit of detection as low as ca. 103 phages per ml of acidic whey. The protocol was also used in a colony PCR approach to detect and identify 3 new lysogenic S. thermophilus strains harbouring inducible pac-type prophages within a set of 60 S. thermophilus strains isolated from traditional Egyptian yoghurt (Zabady) samples. When a number of newly isolated S. thermophilus phages was screened by the multiplex-PCR developed in Chapter 3, phage P738 failed to deliver a PCR product. In order to confirm that this phage represents a new phage species for S. thermophilus phages, a detailed characterization was performed for this phage as described in Chapter 4. Phage P738 was originally propagated on the well-described S. thermophilus strain S4 but could also infect a set of 15 other S. thermophilus strains illustrating its broad host range. Notably, it was not possible to propagate phage P738 lytically in liquid cultures at the standard incubation temperature of 40°C used for these thermophilic cultures. Efficient cell lysis and phage proliferation was only possible at a lower temperature of 30°C. Phage P738 had a unique morphotype with an isometric head (57 nm ), a remarkably short, non-contractile tail (124 nm length x 10 nm ) and a distinct tail fiber (54 nm length). By SDS-PAGE analysis it was documented that phage P738 revealed a distinct structural protein profile with one major protein band (33 kDa) and 5 minor protein bands (sizes: 50 kDa, 60 kDa, 72 kDa, 91 kDa, 150 kDa). By pulsed-field gel electrophoresis and restriction enzyme analysis, phage P738 was identified as a pac-type phage with a genome size of ca. 35 kb. The P738 DNA did neither hybridize with the DNA from other S. thermophilus reference phages (phages TP-J34, TP-778L, P53) nor with the DNA of different L. lactis reference phages (phages BK5-T, P335, r1t, TP901-1, P001, P008, sk1, P446). A 2.8-kb EcoRV fragment of the P738 genome was cloned into the plasmid vector pJET1.2/blunt. Using a primer walking strategy, the DNA sequence was determined from a 6.2 kb genomic region. Seven open reading frames (orfs) were identified which were transcribed in the same direction. By in silico DNA sequence analysis it was shown that the genes putatively code for the large subunit of terminase (TerL) and furthermore for the structural proteins required for head morphogenesis. These putative proteins revealed high similarity with proteins from S. pyogenes prophages. Only very little similarity was found to the corresponding gene products of S. thermophilus phages. By MALDI-TOF mass spectrometry of the phage structural proteins, 2 protein bands were identified that could be correlated with orf430 (50-kDa product; portal protein) and with orf302 (33-kDa product; major head protein). A P738 specific set of PCR primers was selected for targeting the structural gene of the major head protein of this new S. thermophilus phage species and was included in the multiplex PCR tool developed in Chapter 3.Milchsäurebakterien nehmen wichtige aber gegensätzliche Funktionen für den Menschen wahr. Einerseits findet man unter ihnen bedeutsame bakterielle Krankheitserreger (z.B. Streptococcus pyogenes und S. pneumoniae), andererseits werden sie als Starterkulturen für die Herstellung fermentierter Lebensmittel (Milchprodukte, Fleisch, Gemüse, Sauerteig, Wein und Kakao) und Silage verwendet. S. thermophilus ist eines der wichtigsten Milchsäurebakterien und wird für die Herstellung von Joghurt, Mozzarella und verschiedenen Käsesorten (z.B. Cheddar und Schweizer Hartkäse) verwendet. Infektion der Kulturen durch Bakteriophagen stellt stets ein großes Problem bei der industriellen Fermentation dar, aus der erhebliche finanzielle Verluste resultieren. Die Charakterisierung der Phagenpopulationen ist deshalb ein wichtiger erster Schritt zur effizienten Phagenkontrolle in Molkereien und in anderen Industriezweigen, in denen Lebensmittelfermentationen stattfinden. Ziel der im Kapitel 1 beschriebenen Arbeit war die Identifizierung und Charakterisierung eines neuen temperenten S. thermophilus Phagen (Phage TP-778), der aus dem lysogenen Wirtstamm S. thermophilus SK778 durch Induktion freigesetzt wurde. Der Phage TP-778 zeigte die typische Morphologie aller S. thermophilus Phagen mit isodiametrischen Köpfen und langen, nicht-kontraktilen Schwänzen. Dieser Phage wurde als pac-Typ Phage mit einer Genomgröße von ca. 44 kb klassifiziert. Es ließen sich keine prophagenkurierte Stämme isolieren – ein Hinweis darauf, dass keine normale Excision der Prophagen-DNA aus der chromosomalen DNA erfolgt. Der Phage TP-778 konnte auf dem nicht-lysogenen Wirtsstamm S. thermophilus B106 lytisch vermehrt werden Ein auf diesem Wirt angezüchtetes Einzelplaque-Isolat (TP-778L) wurde später genauer charakterisiert. Die TP-778 DNA wurde in einer „Southern-Blot“ Analyse mit den chromosomalen DNAs aus nicht-lysogenen S. thermophilus Stämmen hybridisiert, dabei traten viele unspezifische Hybridisierungssignale bei allen Stämmen auf. Dies war ein Hinweis, dass das TP-778 Phagengenom entweder (1) DNA-Regionen enthält, die Ähnlichkeiten zur chromosomalen Wirts-DNA zeigen, oder dass (2) der Phage in der Lage ist, während der Phagenvermehrung in den Wirtszellen deren chromosomale DNA mit zu verpacken (und auch zu transduzieren). Zur Klärung wurde eine DNA-Sequenzanalyse des Lysogeniemoduls und der flankierenden Phagengenom-Bereiche (vom Phagenlysin-Gen bis zum regulatorischen cro Phagengen) durchgeführt. Dieser Genomabschnitt wurde ausgewählt, da dort alle genetischen Determinanten für die Integration / Excision der Prophagen-DNA (z.B. das Integrasegen), zur Festlegung des lysogenen / lytischen Phagenvermehrungszyklus (z.B. regulatorische Gene des genetischen Schalters) und weiterhin die Kontaktstellen zwischen Prophagen-DNA und bakterieller DNA (attL und attR) lokalisiert sind. Die beiden im Prophagen gegenüberliegenden DNA Regionen („attL-cro“ DNA-Fragment von der linken Prophagen/Chromosom-Kontaktstelle (attL-Site“) bis zum cro Gen; „lysin-attR“ DNA-Fragment vom Lysin-Gen bis zur mutmaßlichen attR-site auf der gegenüberliegenden Kontaktstelle) wurden mittels PCR amplifiziert und sequenziert. Durch die Sequenzanalyse der lysin-attR Prophagen DNA wurde ein 1,9-kb Prophagen-Überrest („Remnant“) mit einem auf 398-bp verkürzten Integrasegen identifiziert. Dieser Region fehlte eine funtionelle attR-„Site“, sie wurde daher in lysin-attR Fragment umbenannt. Das bedeutet, dass der TP-778 Prophage keine normale Integration / Excision durch ortsspezifische Rekombination zwischen den homologen attP- und attB-„Sites“ ausführen kann. Während ein nicht-funktionelles, deletiertes Integrasegen auf dem lysin-rattR Prophagen Fragment gefunden wurde, wies das attL-cro Fragment ein komplettes Integrasegen (1080 bp) auf. Außerdem zeigt diese Kernregion des TP-778 Lysogenie-Moduls sehr hohe Homologie zu dem temperenten Phagen TP-J34 (Neve et al., 2003) und kodiert – wie auch die TP-J34 DNA – für ein Lipoprotein (Orf142TP778). Es wurde geschlussfolgert, dass der TP-778 Prophage direkt mit dem 1,9-kb Prophagen-„Remnant“ im lysogenen Wirtstamm verknüpft ist. Zur Bestätigung, dass der Phage TP-778 zusätzliche DNA verpacken kann, wurden Phagen mit DNase I behandelt, um Kontamination mit chromosomaler Wirts-DNA auszuschließen. Von der extrahierten Phagen-DNA konnte dann ein Fragment der 16S rDNA amplifiziert werden. Die positive PCR-Reaktion wurde in einer „Southern Blot“ Analyse mit einer 16S rDNA Sonde bestätigt. Somit ist der temperente Phage TP-778 (und auch das lytische Derivat TP-778L) befähigt, chromosomale DNA der Wirtszellen zu verpacken. Die Kernregion des Lysogeniemoduls des lytisch vermehrten Phagenderivats TP-778L wurde ebenfalls durch DNA-Sequenzierung analysiert. Dort wies der Phage TP-778L ein auf 398 bp deletiertes Integrase-Gens auf. Dessen Sequenzvergleich mit dem intakten Integrasegen des Phagen TP-778 und dem Integrase-Genfragment des 1,9-kb Prophagen-„Remnants“ dokumentierte eine rekombinante „Hybrid“-Struktur für das TP-778L Integrase-Genfragment gezeigt - resultierend aus einer homologen Rekombination der beiden Integrase-Determinanten in lysogenen SK778 Zellen. Kapitel 2 beschreibt den Vergleich der Gene ltpTP-778 (orf142TP-778) des Phagen TP-778 und ltpTP-J34 (orf142TP-J34) des Phagen TP-J34 und deren abgeleitete Genprodukte. Das Lipoproteingen ltpTP-778 des Phagen TP-778 ist eng verwandt mit dem entsprechenden ltpTP-J34 Gen des Phagen TP-J34. Kürzlich wurde gezeigt, dass orf142TP-J34 (ltp) für ein spezifisches „Superinfection Exclusion System“ kodiert. Dieser Phagenresistenzmechanismus war ebenfalls in Laktokokken-Wirtszellen gegen den isodiametrischen Phagen P008 wirksam, allerdings nicht gegen den prolaten Phagen P001 (Sun et al., 2006). Die Aminosäuresequenz der beiden abgeleiteten Lipoproteine unterschied sich nur in 10 Aminosäuren. Das ltpTP-778 Gen wurde in den Expressionsvektor pMG36e kloniert. Der rekombinante Vektor pYAL1 wurde ebenfalls in Lactococcus lactis Bu2-60 transformiert, um den ltpTP-778 Effekt auf den Phagenresistenz-Phänotyp der Zellen zu bestimmen. Die ltpTP-778 Genexpression in Bu2-60-Zellen wurde durch SDS-PAGE Analyse bestätigt, jedoch reagierte das Protein nicht mit einem polyklonalen Antiserum gegen das LtpTP-J34 Lipoprotein des Phagen TP-J34. Von 3 Bu2-60(pYAL1) Transformanten waren 2 Stämme weitestgehend resistent gegen den Phagen P001, aber nicht gegen den Phagen P008. Die dritte Transformante war sensitiv für beide Phagen. Diese abweichenden Phagenresistenz-Phänotypen der Bu2-60 Transformanten resultiert vermutlich aus den wenigen variablen Aminosäuren, in denen sich die LtpTP-778 und LtpTP-J34 Lipoproteine unterscheiden. Bedingt durch die hohen finanziellen Schäden, die durch eine Bakteriophageninfektion der Starterkulturen entstehen können, besteht Bedarf für schnelle und sensitive Methoden zur Phagendetektion und –identifikation in Molkereien. In Kapitel 3 wird eine schnelle und zuverlässige Multiplex-PCR Methode beschrieben, die die gleichzeitige Detektion von S. thermophilus Phagen und deren Differenzierung in die 2 bekannten pac- und cos-Typ Untergruppen erlaubt. Da pac- und cos-Typ Phagen unterschiedliche Strukturproteine aufweisen, wurden 2 Primerpaare aus der jeweils hochkonservierten Region der Hauptkopfprotein-Gene von 8 vollständig sequenzierten S. thermophilus pac-Typ Phagen (TP-J34, O1205, Sfi11, 2972) und cos-Typ Phagen (Sfi21, 2701, Sfi19, DT1) ausgewählt. Die 2 Primerpaare konnten simultan in einem Multiplex-PCR Ansatz verwendet werden, da sich die PCR-Produkte in ihrer Fragmentgröße unterschieden (432-bp Produkt für pac-Typ Phagen bzw. 514-bp Produkt für cos-Typ Phagen). Die Zuverlässigkeit des Multiplex-PCR Protokolls wurde durch die folgenden drei Kontrollen validiert und bestätigt: (I) Restriktionsenzym-Analyse der DNA aus cos- und pac-Typ Phagen mit und ohne Erhitzungsschritt bei 74 °C, der nötig ist zum „Schmelzen“ der DNA-Fragmente, die cos-Enden aufweisen, (II) SDS-PAGE Analyse der Strukturproteine von pac-Typ (3 Hauptbanden) und cos-Typ Phagen (2 Hauptbanden), und zusätzlich durch (III) Immunoelektronenmikroskopie der Phagen, die mit einem polyklonalen Antiserum gegen den pac-Typ Phagen TP-778 behandelt wurden. Die Multiplex-PCR lieferte bereits nach ca. 2,5 h Resultate. Die Methode ist sehr sensitiv mit einer Nachweisgrenze von ca. 103 Phagen pro ml Sauermolke. Das Protokoll wurde auch in einem Kolonie-PCR Ansatz an 60 S. thermophilus Stämmen, die aus traditionell fermentierten, ägyptischen Joghurtproben (Zabady) isoliert worden waren, verwendet. Dabei wurden 3 lysogene S. thermophilus Stämme mit induzierbaren pac-Typ Phagen detektiert und identifiziert. Bei dem Screening von neu isolierten S. thermophilus Phagen mit der Multiplex-PCR Methode, die in Kapitel 3 entwickelt wurde, wurde bei dem Phagen P738 kein PCR Produkt nachgewiesen. Um zu überprüfen, ob dieser Phage eine neue Phagenspecies der S. thermophilus Phagen repräsentiert, wurde, wie in Kapitel 4 beschrieben, eine detaillierte Charakterisierung dieses Phagen durchgeführt. Der Phage P738 wurde zunächst auf dem gut beschrieben S. thermophilus Stamm S4 angezüchtet, jedoch konnte der Phage auch 15 weitere S. thermophilus Stämme infizieren, womit ein breites Wirtsspektrum dokumentiert wurde. Es war außergewöhnlich, dass die lytische Anzucht des Phagen in Flüssigkultur bei der Standard-Inkubationstemperatur von 40°C nicht möglich war. Eine effiziente Zell-Lyse und Phagenvermehrung war nur bei einer niedrigeren Temperatur von 30°C möglich. Der Phage P738 wies eine einzigartige Morphologie auf, mit einem isodiametrischen Kopf ( 57 nm), einem bemerkenswert kurzen, nicht-kontraktilen Schwanz (Länge 124 nm, 10 nm) und einer ausgeprägten Schwanzfiber (Länge 54 nm). Durch SDS-PAGE Analyse wurde für den Phagen P738 ein eigenständiges Muster an Strukturproteinen mit einer Hauptproteinbande (33 kDa) und 5 Minorproteinbanden (50 kDa, 60 kDa, 72 kDa, 91 kDa, 150 kDa) gezeigt. Durch Pulsfeld-Gelelektrophorese und Restriktionsenzym-Analyse wurde der Phage P738 als pac-Typ Phage identifiziert mit einer Genomgröße von ca. 35 kb. Die DNA des Phagen P738 hybridisierte weder mit der DNA anderer S. thermophilus Referenzphagen (TP-J34, TP-778L, P53), noch mit der DNA unterschiedlicher Lactococcus lactis Referenzphagen (BK5-T, P335, r1t, TP901-1, P001, P008, sk1, P446). Ein 2,8-kb EcoRV Fragment des P738 Phagengenoms wurde in den Plasmidvektor PJET1.2/blunt kloniert. Damit konnte mittels „Primer-Walking“ die DNA-Sequenz eines 6,2-kb langen Genomabschnitts bestimmt werden. Sieben offene Leseraster (orfs) wurden erfasst, die alle in der gleichen Richtung transkribiert wur