SurA is a molecular chaperone in the periplasm of E.coli and has been implicated in the maturation of outer membrane proteins (OMPs). SurA consists of four domains, but only two of them, namely the N and C-­terminal domains, are necessary for chaperone function. Very little is known about which residues drive the interaction between the N and C-­termini that facilitates normal activity. We mutated several conserved residues on the C-terminus and generated additive truncations to observe the effects of each on the fitness of the cell. We found one mutation E(408):A was sufficient to reduce SurA activity by 3-­fold, but structural characterization of the mutated protein revealed little variation from wild-­‐type SurA. Most notable, we found that when at least 10 residues are removed from the C-­‐terminus, the protein is completely non-­‐functional. We introduced a random peptide library to substitute these 10 residues and found that ~1.5% of all possible sequences in the library can restore SurA function to at least 50% activity. Moreover, we observed no pattern in the sequences of 26 different variants that were chosen and characterized. Here we show for the first time that SurA can tolerate many mutations at the C-­terminus and still be active.

Människan står inför stora utmaningar med att bekämpa olika typer av miljöproblem. Många av dessa problem är orsakade av människan men det finns också de problem som orsakats av föroreningar som uppstår naturligt. En av dessa naturliga föroreningar är sura sulfatjordar. Sura sulfatjordar lakar ur förorenande metaller och riskerar således att skada omgivningen, speciellt närliggande vattendrag. Karteringen av dessa jordar har historiskt både varit kostsamma i tid och pengar. Sveriges Geologiska Undersökning (SGU) har utvecklat en modell som via ett script utför maskininlärning för att förutspå förekomsten av sura sulfatjordar på landskapsnivå. Detta förväntas att både spara tid och pengar. Hur väl modellen presterar i områden med begränsad eller helt utan fältdata är dock ej undersökt. I denna studie görs en ansats till att verifiera om modellen förutspår förekomsten av sura sulfatjordar korrekt även på större avstånd från områden med fältobservationer. Studieområdet för modellen är Mälardalen. Området är präglat av jordbruk, vilket kan påverka hur väl modellen presterar. Inom studien undersöktes även en utvecklingsmöjlighet för att lära modellen att inte peka ut områden i vatten som sur sulfatjord, vilket delvis lyckades. Verifieringen av modellens kartering skedde i två steg, den första via GIS-analys där tidigare kända indikatorers spatiala utbredning för sura sulfatjordar granskades, indikatorerna är spårämnen i rotsystemen på bäckvattenväxter. Olika spårämnesförhållanden, Ni (nickel)/Pb (bly), Y (yttrium)/Pb och Cu (koppar)/Pb, jämfördes sedan med modellens kartering. Ytterligare verifiering gjordes via fältstudie. Studien pekar på att modellens kartering går att verifiera på generell landskapsnivå. Studien pekar även på att modellen i visa fall är för konservativ, då platser som modellen pekar ut som icke aktiv sur sulfatjord har höga indikatorvärden samt vid en plats i fält där aktiv sur sulfatjord identifierades. Det kan möjligtvis åtgärdas med utökade indata eller annan utveckling av modellen.

Acid sulphate soils cover all around the world an area of approximately 170 000 km2. The soils can cause huge acidification problems for streams and lakes due to increasing concentration of hydrogen ions which will increasing the mobilization of heavy metals. This can result in huge complications for species living in the polluted water. The aim with this study was to see what kind of impact the ditching activity in a catchment area affected by sulfide soils have when it comes to the leaching of heavy metals and Al. This was studied by investigate the distribution of 27 different elements (such as heavy metals, trace metals, nutrient etc) and LOI in a 2,14 m long marine sediment core from a bay situated in the county of Västerbotten. The catchment area from the stream which has it outflow at the bay are predicted to be affected by the acid sulphate soils in a high extent. Furthermore the spatial distribution of the elements in the bay was studied, this was made by compare the results from two sediments samples taken by a HTH corer from two different locations. The results made it clear that some element highly correlated to each other followed a trend similar to the ones of Sulphur and LOI. The concentration for the elements (As, Cu, Fe, Mn, Ni, Pb och Zn) was also compared by the Canadian guidelines which indicate that As and Fe had concentration that can cause severe negative effects for biota in the water. The conclusion made from this study indicate that the majority of the elements are affected by the LOI fluctuations due to the high positive or negative correlation to LOI. Therefore the highest concentration of elements such as Al, Co, Cu Mn, Ni and Zn which will be leached by acid sulphate soils are in this situation instead caused by LOI. However there occur some trends when the ratio between S/LOI and other heavy metals sharply  increase, this could be seen as a sign of an effect caused by acid sulphate as a results of ditching activity.

The aim of this study was to identify and characterise peptidyl-prolyl cis-trans isomerases (PPIases) from the bacterium Burkholderia pseudomallei, the causative agent of the disease melioidosis. The longer term goal was to assess their potential as vaccine candidates or antimicrobial targets. Using bioinformatic approaches, six putative FK506-binding proteins (FKBPs) proteins and three putative parvulin proteins were identified in B. pseudomallei. Of these, six were expressed and purified as recombinant proteins. The purified proteins were used to immunise BALB/c mice, with some providing protection against a subsequent B. pseudomallei infection. These proteins could therefore be proposed as potential vaccine candidates. Homologues of Mip or SurA, which are associated with virulence in other bacterial species, were identified in B. pseudomallei and closely related B. thailandensis. Recombinant Mip or SurA homologues from B. pseudomallei were shown to have characteristic PPIase enzyme activity. To evaluate the role of the Mip homologue from B. pseudomallei in virulence, an unmarked deletion mutant was constructed. The mutant had reduced intracellular survival; defects in putative virulence mechanisms and attenuated virulence in mice. To assess the role of a SurA homologue, closely related B. thailandensis was used as a model organism, with deletion of the gene resulting in defects in intracellular infection, outer membrane integrity and virulence. This indicates that PPIases from B. pseudomallei and B. thailandensis represent novel virulence determinants and potential antimicrobial targets for therapeutics against melioidosis.

Multiple drug resistance (MDR) has been a severe issue in treatment and recovery from infection.Gram-negative bacteria intrinsically exhibit higher drug tolerance than Gram-positive microbes. In this thesis, two proteins involved in Gram-negative bacterial MDR were studied, AcrB and SurA. Resistance-nodulation-cell division pump AcrAB-TolC is the major MDR efflux system in Gram-negative bacteria and efficiently extrudes a broad range of substances from the cells. To study subtle conformational changes of AcrB in vivo, a reporter platform was designed. Cysteine pairs were introduced into different regions in the periplasmic domain of the protein, and the extents of disulfide bond formation were examined. Using this platform, an inactive mutant, AcrB∆loop, was created that existed as a well-folded monomer in vivo. Next, random mutageneses were performed on a functionally compromised mutant, AcrBP223G, to identify residues that restored the function loss. The mechanism of function restoration was examined. SurA is a periplasmic molecular chaperone for outer membrane biogenesis. Deletion of SurA decreased outer membrane density and bacterial drug resistance. The dependence of SurA function on structural flexibility and stability was examined. In addition, the effect of molecular crowding on SurA interaction with its outer membrane protein substrates was examined.

Das SurA-Protein ist ein wichtiger Bestandteil der periplasmatischen Faltungsmaschinerie aus Escherichia coli. Trotz zahlreicher Erkenntnisse sind die Mechanismen der Substraterkennung und -bindung noch nicht abschließend geklärt. Das SurA-Protein ist aus einem Chaperonmodul und zwei PPIase-Domänen aufgebaut. Die Bindestelle eines artifiziellen Peptides wurde zu Beginn der Arbeit in der PPIase-inaktiven Parvulin-Domäne I publiziert. Im Rahmen dieser Arbeit wurde untersucht, ob auch biologisch relevante, natürliche Peptide an dieser Bindestelle interagieren und ob es noch weitere Substratbindestellen innerhalb von SurA gibt. In ESR-spektroskopischen Versuchen wurde die Interaktion der isolierten Parvulin-Domäne I von SurA mit Peptiden aus einer LamB-Peptid-Bibliothek, sowie mit dem artifiziellen Peptid analysiert. Die Bindung des artifiziellen Peptides und eines Peptides aus der LamB-Peptid-Bibliothek an die isolierte Parvulin-Domäne I konnte nachgewiesen werden. Für weitere an SurA-bindende Peptide konnte an dieser Position keine Interaktion nachgewiesen werden. Mittels des genetischen Indikatorsystems ToxR wurden gezielt Kontaktpunkte zwischen dimerisierten SurA-Untereinheiten bzw. zwischen SurA und Peptid unterbunden, um deren Einfluss auf die wechselseitige Interaktion zu untersuchen. Hierbei wurden einzelne Positionen in isolierten SurA-Domänen identifiziert, die an einer Interaktion beteiligt sind. Die Mutation dieser Interaktionsstellen führten zu keinem signifikanten Verlust der in vivo-Funktion, welche mittels der Fähigkeit der SurA-Varianten zur Komplementation des synthetisch letalen Phänotypen einer surA skp-Doppelmutante untersucht wurde. Die Grundlagen für die Methodik der photoaktivierbaren, ortsspezifischen Quervernetzung von OMP-Polypeptiden an SurA- bzw. SurAI-Proteine wurden etabliert. / The SurA protein is an important part of the periplasmic folding machinery in Escherichia coli. Despite numerous findings are the mechanisms of substrate recognition and folding not yet completely resolved. The SurA protein consists of a chaperone module and two parvulin domains. In the beginning of this work a peptide binding site was published which was located in the PPIase inactive parvulin domain I. It was investigated in this thesis whether biological relevant, natural peptides would also bind with this binding site and if additional substrate binding sites exist within the SurA protein. In ESR-spectroscopy experiments both the interaction of the isolated parvulin domain I of SurA with peptides of a LamB peptide library and with the artificial peptide were examined. Binding of the artificial peptide and one peptide of the LamB peptide library to the isolated parvulin domain I could be detected. For the remaining tested peptides, which are confirmed to be SurA binders, no interaction could be verified at this position. By use of the genetic indicator system ToxR the contact points between dimerized SurA subunits respectively between SurA and peptide were prevented site-specifically to examine their influence on the mutual interaction. Here single positions in isolated SurA-domains were identified, which are part of an interaction. The mutation of these interaction sites lead to no significant loss of the in vivo function, which was analyzed by the capability of the SurA variants to complement the synthetic lethal phenotype of a surA skp double mutant. The fundamentals for the method of photoactivated site-specific crosslinking of OMP polypeptides to SurA respectively SurAI were established.

Global environmental concerns arise when marine deposits with fine-grained iron sulfide-rich sediments (FeS and FeS2), now situated above sea level, oxidize from anthropogenic lowering of the groundwater table. The oxidation of iron sulfides decreases the soil pH and the acidic environment of these Acid Sulfate Soils (AS) soils increase weathering and mobilization of metals into adjacent watercourses, lakes and estuaries. Low pH and enhanced concentrations of metals are known to influence water quality negatively, causing fish kills and reduced aquatic diversity. Sulfide rich sediments were deposited in the Baltic Sea after the last glaciation and are now abundantly found along the coasts of for example the Bothnian Bay as a result of isostatic rebound. Recent studies from Finland have stated associations between leached (AS) soils and increased concentrations of metals in estuary sediments, thus the effects are likely to be similar in Sweden. With financial support from the Interreg Nord project “Ecological restoration in coastal river basins in the Bothnian Bay” in cooperation with the Geological Survey of Sweden (SGU), sediments from three lakes and two estuarine sites in the Rosån catchment in Norrbotten county, northern Sweden, were sampled and analyzed with fpXRF, ICP-MS and LOI methods. Elemental concentrations and organic contents were compared to establish accumulation trends over time and relationships between metal concentrations in recently deposited sediments and potential influence from previously sampled (AS) soils. Correlations in time, to anthropogenic activity, such as ditching were also considered. A primary allover trend with increasing concentrations of Aluminum (Al), Arsenic (As), Cadmium (Cd), Cobalt (Co), Cupper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb), Rare Earth Elements (REE) and Zinc (Zn), was noticed in a majority of the lake and estuary sediment samples. With some site variation, also two discrete peaks at different depth, were found in the upper 20 to 30 cm of the sampled sediments. Significant correlations to organic matter were also found for a considerable amount of the elements. Soil samples from (AS) soils in areas related to Rosån show pH values as low as 2.62 and oxidation depths down to 170 cm. Substantial elemental depletion in the oxidized zone suggest increased weathering, leaching and mobilization of Al, Cd, Co, Mn, Ni, REE, Zn and to some extent As, Cu, Fe and Pb from the soil, as a consequence of the acidic environment. A relationship between (AS) soils and increased metal concentrations is therefore likely. The sedimentation rate of roughly 0.2 cm/year was calculated from the separation age of the lakes and the sediment depth to an interpreted transition from more marine environment to lake settings. Consequently the distinct peaks of increased metal concentrations are thus suggested to be related to anthropogenic activities as for example improved drainage methods after the Second World War, but proper dating of the sediments is needed to establish any certain correlations. / På senare tid har man uppmärksammat de miljöproblem som uppstår när finkorniga sediment, innehållande järnsulfider, oxiderar på grund av mänsklig påverkan, t ex. dikning, eller annan typ av aktivitet som sänker grundvattennivån. När järnsulfiderna oxiderar bildas svavelsyra som gör att pH- värdet i marken blir väldigt lågt. Den sura miljön i dessa så kallade sura sulfatjordar, gör i sin tur att mineraler i marken vittrar fortare med påföljden att både surt vatten och ökade mängder metaller, sprids till närliggande vattendrag, sjöar och hav. Lågt pH och höga halter av metaller i vatten påverkar även vattenkvalitén negativt och har rapporterats orsaka fiskdöd och minskad akvatisk mångfald. Sura sulfatjordar är globalt förekommande och återfinns bland annat längs Bottenvikens kuster. De har kunnat bildas genom att sulfidhaltiga sediment, som avsattes i Östersjön efter den senaste istiden, nu befinner sig ovan havsnivån på grund av landhöjningen. I Finland har man i flera studier sett ett samband mellan sura sulfatjordar och ökade metallhalter i nyligen avsatta kustsediment och man kan anta att liknande förhållande gäller även i Sverige. Med finansiellt stöd från EU-projektet “Kustmynnande Vattendrag i Bottenviken-Metodutveckling och Ekologisk Restaurering” (Interreg Nord) genom Sveriges geologiska undersökning (SGU) och i samarbete med Länsstyrelsen i Norrbotten, har bottensediment från tre sjöar och två fjärdar i Rosåns avrinningsområde i Norrbotten provtagits och analyserats. För att fastställa hur koncentrationerna har förändrats över tiden har metallhalterna i de nyligen avsatta sedimenten jämförts med koncentrationerna i äldre sediment. Även jordprofiler från sura sulfatjordar i området har studerats för att kunna utvärdera ett ev. samband mellan urlakade ämnen i jordarna och ökade halter i sedimenten. Granskning av hur långt metallerna transporteras i systemet har gjorts, liksom försök att hitta kopplingar i tiden till mänsklig påverkan som t.ex. dikning. I de översta sedimenten kan man, förutom en generellt ökande trend av aluminium (Al), arsenik (As), kadmium (Cd), kobolt (Co), koppar (Cu), järn (Fe), mangan (Mn), nickel, (Ni) bly (Pb), sällsynta jordartsmetaller (REE) och zink (Zn), också se tydliga toppar med ökade halter av dessa ämnen på minst två specifika djup. De sura sulfatjordarna, som uppmätte pH-värden ner till 2,62, visade tecken på urlakning av Al, Cd, Co, Ni, Mn, REE, Zn och till viss del också As, Cu, Fe och Pb, varpå en trolig relation mellan sura sulfatjordar och ökade metallhalter i nyligen avsatta sediment kan fastställas. En uppskattning av ackumulationshastigheten, som gjordes utifrån när de provtagna sjöarna skiljdes från havet, och sedimentdjupet som visar övergången från hav till sjö, visar att de observerade topparna av ökade metallkoncentrationer i sedimenten skulle kunna vara förknippade med dikning i början av 1900-talet och efter andra världskriget. För en säker bestämning av sambandet till specifika händelser behövs dock en riktig datering.

Pseudomonas aeruginosais an opportunistic pathogen that infects cystic fibrosis (CF) patients contributing to their high morbidity and mortality. P. aeruginosaundergoes a phenotypic conversion in the CF lung, from nonmucoid to mucoid, by constitutively producing a polysaccharide called alginate. These mucoid strains often revert to nonmucoid in vitrodue to second-site suppressor mutations. We hypothesized that mapping these mutations would lead to the identification of novel genes involved in alginate production. In a previous study, a mucoid strain, PDO300 (PAOmucA22), was used to isolate suppressors of alginate phenotype (sap). One of the uncharacterized nonmucoid revertants, sap27, is the subject of this study. The mucoid phenotype in sap27was restored by pMO012217 from a minimal tiling path cosmid library. The cosmid pMO012217 harbors 18 P. aeruginosaopen reading frames (ORF). The cosmid was mutagenized with a transposon to map the contributing gene. It was mapped tolptD(PA0595) encoding lipopolysaccharide transport protein. E. coliLptD transports lipopolysaccharide to the outer leaflet of the outer membrane. The Alg+phenotype was restored upon complementation with P. aeruginosa lptDalone, suggesting that sap27likely harbor a chromosomal mutation inlptD. Sequencing analysis of sap27showed the presence of a mutation not in lptDbut in algO, which encodes a periplasmic protease protein. This suggests LptD is able to bypass analgO mutation by positively regulating alginate production. The lptD is a part of a three-gene operon lptD-surA-pdxA. SurA is an essential protein for survival in starvation and a major chaperone protein for all outer membrane proteins and PdxA is a NAD-dependent dehydrogenase and is involved in the vitamin B6biosynthetic pathway. Pyridoxal 5’-phosphate (PLP) is the active form of vitamin B6.P. aeruginosagrown in a media supplemented with PLP increased production of pyocyanin, a virulence factor. The PLP and aromatic amino acids are synthesized from a common precursor chorismic acid. We demonstrated an increase in pyocyanin production when the bacteria were cultured supplemented by the aromatic amino acids phenylalanine. We concluded that the lptDoperon plays a role in the P. aeruginosavirulence by regulating alginate and pyocyanin production.

Acid sulphate soils is a wide spread problem along the northern coast of Sweden. This is causing great damage through low pH and leaching of metals out into the streams. These soils are estimated to be found in several places in Sweden but also in many other areas in the world. One of these areas in Sweden that are believed to contain these sediments is Mälardalen. The purpose of this study is to evaluate the extension of the acid sulphate soils in this area. This has been accomplished through measurements of pH in the field as well as laboratorial work such as measuring the organic substance in the soil. The soils sulphur content was also analysed in a number of the samples. A total of 29 places has been visited in the area. The examination has been done as a pilot survey for the SGU. The study wanted to confirm if the acid sulphate soils are a problem in Mälardalen and if there is a connection between the soils that has a high organic matter and by what time they were deposited, and that those attributes would be a link to a low pH. The results is indicating that there is some correlation, mainly when it comes to soils with high organic content that has been deposited around 1000 years ago. With these quality’s the probability is going to be higher to find a soil that has a low pH. When examining diagrams showing these relations, we get an R-square value for the trend lines from both cases showing a correlation of 30%. This give us the indication that there are also other factors which will affect the pH. In this study the pH has been used as an indicator to where acid sulphate soils could be located. One cannot say that a high pH will exclude the possibility for a soil to become an acid sulphate soil, in the cases where the oxidized zone is small or absent. To ensure this fact, the soil will need to be oxidized as well as analysed to establish the sulphur content in the sample. This thesis has not shown any difference when it comes to the potential of acidification caused by these soils and the event of different kinds of sulphur compounds in Norrland and Mälardalen. According to our fulfilled literature studies the main difference are supposed to lay in the variation of the grain size in the different kinds of sediments. Air diffuse slower into a soil with a high content of clay compared to a soil with more silt. Clay may also have a bigger buffer system though high CaCo3 content or a high cation exchange capacity. The samples from the sites of Brantshammar, Kungsängen and Hova got time to oxidize as well as going through a sulphur analysis. Though these examinations as well as evaluations in the field, these sites could be confirmed to be acid sulphate soils. The number of parameters that was analysed for the other sites in this study are said to be too few, and gave inadequate results, and not the amount of information needed to be able to confirm the soils as acid sulphate soils. However, the correlation and the probability did increase with the number of consistent variables. The area would need another survey when there have been findings of acid sulphate soils as well as potential acid sulphate soils in this area. Further investigations can supplement the results from this current study and give a more apparent picture of the area, due to the fact that only a smaller amount of places could be reached within the time range of this survey. / Sura sulfatjordar är ett utbrett problem längs Sveriges nordligaste kust och orsakar skada genom låga pH och urlakning av metaller ut i vattendrag. Ett av dessa områden i Sverige tros vara Mälardalen och syftet med det här arbetet var att undersöka utbredningen utav sura sulfatjordar där. Genom att mäta pH på olika djup ute i fält, analysera organisk halt i labb samt svavelhalt i ett antal prover, så har 29 olika platser i området undersökts. Arbetet utfördes som en pilotstudie åt SGU. Målet var att se om sura sulfatjordar utgör ett problem i Mälardalen, och huruvida det finns ett samband mellan jordar med högt organiskt innehåll, vid vilken tidpunkt då avsättningen bildats och om dessa egenskaper sammanfaller med låga pH. Resultaten tyder på att ett visst samband finns, främst när det gäller högre organisk halt i jorden och områden som torrlagts genom landhöjning under de senaste 1000 åren. Sammanfaller dessa parametrar ökar sannolikheteten för att jorden kommer ha låga pH. I diagram över dessa samband visar R-kvadratvärdet för trendlinjen i båda fallen en korrelation på ca 30 % vilket antyder att det även finns andra faktorer som pH är beroende av. Det ska dock tilläggas att pH i den här undersökningen har använts som en indikator på om en jord kan klassificeras som en sur sulfatjord. På en del platser där pH i nuläget är högt skulle sura sulfatjordar kunna bildas om grundvattenytan sänktes. För att säkerställa detta skulle jorden behöva oxideras och pH mätas igen för att sedan analyseras för att ta reda på svavelhalten. Studien har inte visat någon skillnad gällande försurningspotential till följd av olika sulfidföreningar i Norrland gentemot Mälardalen. Enligt utförda litteraturstudier skall skillnaden i stället främst ligga i kornstorleken hos de olika jordarterna. Luft har svårare att tränga ned i en jord med hög lerhalt än i en siltigare jord. Lera kan också ofta ha en större buffrande effekt genom hög katjonutbyteskapacitet. Tidigare undersökningar visar även att Mälardalens gyttjeleror kan ha ett högre CaCO3- innehåll än normalt, vilket även verkar buffrande. Från platserna Brantshammar, Kungsängen och Hova togs prover som fick oxidera och genomgå svavelanalys. Genom dessa undersökningar, samt bedömning i fält, kunde jordarna med säkerhet fastställas som sura sulfatjordar. Antalet parametrar som analyserats på de övriga platserna i undersökning gav inte tillräckligt underlag för att kunna klassificera jordarna som sur sulfatjord, däremot ökade sannolikheten med antal överensstämmande parametrar. Området skulle behöva undersökas grundligare då det har hittats sura sulfatjordar med låga pH, samt områden som potentiellt skulle kunna bli det i framtiden. Vidare undersökningar kan komplettera resultaten från denna undersökning och ge en tydligare bild över området då endast en mindre mängd platser hann undersökas i denna studie.

Une monographie sur la ville antique de Sura s’imposait pour mettre l’accent sur un site-clef, peu étudié, parmi les villes fortifiées du Moyen-Euphrate. L’objectif de ce travail est d’en offrir une description et une analyse poussées et d’élargir le champ des recherches à l’ensemble de la région. À 22 km à l’ouest de Raqqa et à 29 km au nord de Resafa, à l’emplacement du village moderne d’«el-Hammam», Sura (autrefois «Souriya») domine la rive droite de l’Euphrate. Le site est une agglomération fortifiée de forme rectangulaire (76,5 ha) divisée en deux parties, enceinte nord-est et enceinte sud-ouest. Nous présentons Sura de l’époque romaine jusqu’au début de l’époque omeyyade (Ier-VIIIe s.), d’après les résultats de nos recherches qui, entre 2003 et 2011, se sont concentrées sur trois pôles : fortifications, structures domestiques et édifices civils (fouilles intra-muros), nécropole(fouilles extra-muros). Nous étudions ensuite sa culture matérielle à travers le mobilier archéologique et les éléments architecturaux issus des fouilles. Les résultats de ces recherches doivent enrichir le dossier des sites de référence de l’Antiquité tardive pour la région de l’Euphrate et de la Syrie du Nord, en offrant une base de comparaison de premier ordre pour l’architecture civile et funéraire et, surtout, pour le matériel céramique, le verre, les inscriptions. Occupant une position géographique stratégique, Sura fut florissante pendant l’époque romaine et byzantine, jusqu’à la conquête arabe de la région en 639-640, qui scella son déclin – contrairement aux autres villes de l’Euphrate –, puis elle ne fut plus occupée que par des chrétiens locaux, dans des habitats modestes. / A monograph about the ancient city of Sura was necessary in order to bring to light a site little studied so far, in spite of its key importance among the Middle Euphrates fortified towns. The present work aims at offering a thorough description and analysis of it, while broadening the scope of comparison to its larger region. Sura(previously “Suriya”) is situated 22 km west of Raqqa and 29 km north of Resafa, on the location where nowadays stands the village of “el-Hammam”, overlooking the right bank of the river Euphrates. The site, a fortified agglomeration of rectangular shape (76,5 ha), is divided into two parts, the northeast and the southwest enclosures. We present Sura from Roman times until the beginning of the Umayyad period (1st-8th cent.), through the results of our researches, which, from 2003 to 2011, have been focusing, intra-muros, on its fortifications, on its domestic and public structures, and, extra-muros, on its necropolis, then through its material culture, that is, thesmall finds and architectural elements. Such a research should contribute to enhancing the extant knowledge about Late Antiquity in the Euphrates region and North Syria, by bringing forth an additional reference site, especially for civil and funerary architecture and, above all, pottery, glass, and inscriptions. The floruit of Sura, set in a strategic location, lasted from the Roman through Byzantine times, until the Arab conquest of the region, in 639-640, threw it into oblivion – a fate not shared by other cities on the Euphrates. Afterwards, only local Christians maintained some modest settlement there.