Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

MARTINS, André Gustavo Lima de Almeida. Efeitos da emissão dos efluentes domésticos na proliferação de Aeromonas Spp em águas de superfície e pescado do estuário do Rio Bacanga, São Luís - MA. 2005. 95 f. Dissertação (Mestrado em Ciências Marinhas Tropicais) - Instituto de Ciências do Mar, Universidade Federal do Ceará, Fortaleza, 2005. / Submitted by Debora Oliveira (deby_borboletinha@hotmail.com) on 2011-11-24T14:24:55Z No. of bitstreams: 1 2005_dis_agldamartins.pdf: 920756 bytes, checksum: 66a53ba547f972bf992676592529cff5 (MD5) / Approved for entry into archive by Nadsa Cid(nadsa@ufc.br) on 2011-12-05T18:37:32Z (GMT) No. of bitstreams: 1 2005_dis_agldamartins.pdf: 920756 bytes, checksum: 66a53ba547f972bf992676592529cff5 (MD5) / Made available in DSpace on 2011-12-05T18:37:32Z (GMT). No. of bitstreams: 1 2005_dis_agldamartins.pdf: 920756 bytes, checksum: 66a53ba547f972bf992676592529cff5 (MD5) Previous issue date: 2005 / This research work was designed to detect the presence of Aeromonas in the Bacanga River estuary, São Luís, Maranhão State, Brazil. The database consisted of 90 samples of the river’s surface water and 30 samples of fish, in the period from March to October, 2004. They were amenable, simultaneously, to counting of bacteria on Agar Gelatin Phosphate Salt (GSP) plus 20μg/mL of ampicilim (UFC/mL or UFC/g) and to the determination of the Most Probable Number (MPN/100mL or MPN/g), through the multiple test-tube technique using the Tripticase Soy Broth (TSB) plus 20μg/mL of ampicilim. The analyzed fish species were: catfish (Pimelodus maculatus), mullet (Mugil cephalus), flatfish (Pleuronectes platessa), golden tetra (Hemigrammus rodwayi) and Atlantic thread-herring (Opisthonema oglinum). The results showed dissemination of Aeromonas in the estuary. The counts for the water and fish samples varied from 40 to 1.3x108 UFC/mL and from 3.2x102 to 5.8x106 UFC/g, respectively, with the highest indices being registered at points next to domestic sewages outlets. The values for the MPN/100mL in water samples varied from 2.3x104 to 1.6x107 and for the MPN/g in fish samples from 230 to 24x103. The occurrence of the greatest indices of Aeromonas in April, at the height of the rainy season, and the lowest in October, at the height of the dry season, suggests there to be a probable seasonality of bacteria density in the studied environment. Out of the 751 isolated strains from water samples, 582 were positive for Aeromonas, being 52.7% A. caviae, 23.8% A. hydrophila, 19.5% A. veronii and 3.7% A. sobria. Out of the ones isolated from the fish (245 strains) 184 were identified as Aeromonas, being 43.4% A. caviae, 28.2% A. hydrophila, 26.6% A. veronii and 1.6% A. sobria. As concerns the physical and chemical parameters measured in surface waters of the Bacanga River’s estuary, temperature, salinity and pH only showed significant correlations. In general, strains of Aeromonas sp. were found to be sensitive to most of the tested antimicrobians, except for ampicillim, to which they showed 100% resistance. / Para a detecção de Aeromonas foram coletadas 90 amostras de água de superfície e 30 de peixes no estuário do rio Bacanga em São Luís/MA, no período de março a outubro de 2004. As amostras foram submetidas, simultaneamente, ao método de plaqueamento direto em Agar Gelatina Fosfato Sal (Agar GSP acrescido de 20μg/mL de ampicilina) para a contagem (UFC/mL ou g) e a determinação do Número Mais Provável (NMP/100mL ou g) pela técnica dos tubos múltiplos, utilizando-se o Caldo Tripticase Soja (Caldo TSB com 20μg/mL de ampicilina). As espécies de peixes analisadas foram: Bagre (Pimelodus maculatus), Tainha (Mugil cephalus), Solha (Pleuronectes platessa), Prata (Hemigrammus rodwayi), Sardinha (Opisthonema oglinum). Os resultados obtidos retratam uma ampla disseminação de Aeromonas no estuário. Para as amostras de água e peixes as contagens variaram de 40 a 1,3x108 UFC/mL e de 3,2x102 a 5,8x106 UFC/g respectivamente, sendo que os maiores índices foram obtidos nos pontos próximos às emissões de esgotos domésticos. Os valores para o NMP/100mL de água oscilaram entre 2,3x104 e 1,6x107 e de 230 a 24000/g para peixe. Os maiores índices de Aeromonas foram constatados no mês de maior intensidade de chuvas, abril, e os menores em outubro, correspondente ao pico de estiagem na região, evidenciando assim uma possível sazonalidade na incidência da bactéria no ambiente estudado. Das 751 cepas isoladas das amostras de água, 582 foram positivas para Aeromonas, sendo que 52,7% eram A. caviae, 23,8% A. hydrophila, 19,5%, A. veronii e 3,7% A. sobria. Para as isoladas do pescado (245 cepas) 184 foram identificadas como Aeromonas sendo 43,4% de A. caviae, 28,2% de A. hydrophila, 26,6% A. veronii e 1,6% de A. sobria. Com relação aos parâmetros físico-químicos medidos nas águas de superfície do estuário do rio Bacanga, apenas a temperatura, a salinidade e o pH, tiveram correlações significativas. De modo geral, as cepas de Aeromonas sp. foram sensíveis a maioria dos antimicrobianos testados, com exceção de ampicilina, ao qual 100% das cepas foram resistentes.

Orientadora : Profª. Drª. Cyntia Maria Telles Fadel-Picheth / Coorientador : Prof. Dr. Leonardo Magalhães Cruz / Tese (doutorado) - Universidade Federal do Paraná, Setor de Ciências da Saúde, Programa de Pós-Graduação em Ciências Farmacêuticas. Defesa: Curitiba, 03/07/2017 / Inclui referências : f. 85-108 / Resumo: Aeromonas sao bacilos gram-negativos, encontrados em ambientes aquaticos, capazes de causar diversas infeccoes em humanos destacando-se a diarreia. Os objetivos deste trabalho foram sequenciar o genoma da estirpe A. caviae 8LM, isolada a partir de fezes diarreicas, e realizar analises de genomica comparativa. O sequenciamento foi realizado empregando os sistemas 454 GS Junior, Illumina MiSeq e PacBio. Nas analises de genomica comparativa foram empregadas diversas ferramentas de bioinformatica para analise estrutural e do conteudo genico de estirpes de Aeromonas. O genoma de A. caviae 8LM apresenta 4,6Mb, conteudo GC de 61,7%, dispondo de 4.101 CDS e 10 operons de rRNA distribuidos proximos da origem de replicacao. Foram identificados diversos genes relacionados com virulencia incluindo motilidade e adesao, toxinas, sistemas de secrecao tipo II e VI, entre outros. As analises de genomica comparativa mostram a similaridade do genoma de A. caviae 8LM com outras estirpes da especie. As analises realizadas indicaram divergencias na identificacao de algumas Aeromonas e outras, identificadas apenas ao nivel de genero puderam ser identificadas ao nivel de especie. O pan-genoma de Aeromonas e formado por 9.785 genes e o core genoma 701 genes. Foram detectadas regioes do genoma que podem conter possiveis marcadores moleculares para a especie A. caviae. Os resultados deste trabalho trazem informacoes sobre o genoma e virulencia de A. caviae 8LM, e sugerem a presenca de possiveis marcadores moleculares com potencial para o desenvolvimento de testes diagnosticos. Palavras-chave: Aeromonas. Genoma completo. Genomica comparativa. / Abstract: Aeromonas are gram-negative bacilli, found in aquatic environments, are capable of causing several human infections, highlighting diarrhea. The proposes of this work were to sequence the genome of strain A. caviae 8LM, isolated from diarrheal feces, and carry out comparative genomics analyzes. Sequencing was performed applying the 454 GS Junior, Illumina MiSeq and PacBio systems. In comparative genomics analyzes, several bioinformatics tools were applied for structural and gene content analysis of Aeromonas strains. The genome of A. caviae 8LM presents 4.6Mb, GC content of 61.7%, 4,101 CDS and 10 distributed rRNA operons close to the origin of replication. Several genes related to virulence including motility and adhesion, toxins, type II and VI secretion systems, among others were identified. Comparative genomics analyzes exhibited the similarity of the genome of A. caviae 8LM with other strains of the species. The analyzes indicated differences in identification of some Aeromonas and others that were only identified at genus level could be identified at species level. The pan-genome of Aeromonas consists of 9,785 genes and the core genome 701 genes. Genomic regions containing possible molecular markers for A. caviae species were detected. The results of this work provide information about the genome and virulence of A. caviae 8LM, and suggest the presence of possible molecular markers with potential for the development of diagnostic tests. Key-words: Aeromonas. Complete genome. Comparative genomics.

The fish pathogenic bacterium Aeromonas salmonicida is the causative agent of furunculosis in salmonids, a systemic disease that causes important economic losses in salmon aquaculture. Since the paracrystalline S-layer of Aeromonas salmonicida, known as the A-layer, is essential for virulence, the virulence mechanisms associated with this structure were studied. Structural studies demonstrated that the A-layer is flexible and plastic, being capable of acquiring different conformations and/or structural patterns, in which divalent cations play an important role. It was rigorously demonstrated that the A-layer acts as an adhesin, promoting adherence to macrophages, and fish cell lines. Since the macrophage is a professional phagocyte involved in ingesting and destroying bacteria, the ability of A. salmonicida to replicate inside macrophages was examined. A. salmonicida replicated inside macrophages and eventually destroyed them. This characteristic, together with the fact that A. salmonicida also penetrated epithelial fish cells, make it a facultatively intracellular, invasive pathogen. The A-layer provided an initial protection against oxidative agents, increasing the opportunities for A. salmonicida cells to induce an A-layer-independent mechanism involved in high resistance to oxidative agents, and thereby increase survival inside macrophages. Studies with in vivo grown. A. salmonicida provided further insight into the pathogenic process of furunculosis, and suggested that the A-layer plays a crucial role in colonization and penetration of the host, as well as survival inside the host (early events of the infectious process). However, it was found that in vivo grown A. salmonicida is capable of expressing a slime layer that shields its entire surface and provides full protection against complement-mediated killing an phagocytosis, thus relegating the A-layer to a secondary or minor role in the later stages of infection. The results presented have contributed significantly to our knowledge of the virulence factors of A. salmonicida, and could by used practically in the prevention of furunculosis in the salmon aquacultural industry. / Graduate

Aeromonas calmonicida is a Gram negative rod shaped bacterium capable of causing furunculosis in salmonid fish and other chronic and inflammatory diseases in goldfish, carp and also salmonids. The surface layer of A. salmonicida, the A-layer, has been demonstrated to be a major virulence factor for the organism , and its subunit A -protein has been purified and its Structural gene vapA has been cloned. The vapA gene from A. salmonicida strain A450 was subcloned (pSC150) and expressed in Escherichia coli. Its DNA sequence was then determined to consist of 1,506 bp encoding a 502-amino acid residue protein, containing a 21- residue signal peptide and a mature protein of 50,778 Dalton. The A-protein assembled on the cell surface in the form of an S-layer was refractile to trypsin cleavage while trypsin digestion of the purified mature protein revealed a highly resistant 39,400 Dalton N-terminal fragment and a 16,700 Dalton C-terminal fragment with moderate resistance, These trypsin-resistant fragments may form distinct structural domains, consistent with three-dimensional ultrastructural observations. The plasmid pSC150 contained 62 bp of Aeromonas DNA in front of the vapA structural gene. A promoter (P2) was predicted in this region which showed sequence homology to the E. coli c70 promoter. However, prim er extension in the wild type strain A449 showed a transcriptional start site 181 bp upstream from the gene, and thus, another promoter (P1) was shown to be the major promoter. The DNA sequence coding for the untranslated leader mRNA contained two stem-loop structures, a putative small open reading frame spanning the stem-loop structures, and a palindromic sequence which overlaps the predicted ribosome binding site. Northern analyses of A449 vapA mRNA showed that incubation at 15°C produced the highest level of the transcript, and the transcript half-life was 22 m in in cells grown at 15°C compared to 11 min in cells grown at 20°C. DNA gyrase inhibitors nalidixic acid and novobiocin significantly reduced the vapA transcript level. A. salmcnicida 30°C mutants were found to produce significantly reduced levels of A-protein and some of them were shown to have the native insertion elements, ISA1 and ISA2, inserted in the vapA area. These insertion elements have been cloned and sequenced, and also identified in the wild type strains A449 and A450. ISA2 was shown to have sequence similarity to other bacterial insertion elements. Plasmid encoded vapA expression in E. coli was also affected by a downstream gene abcA, which, when deleted from the clone, significantly reduced vapA expression. This reduction could be complemented by the abcA gene carried on a second plasmid. In addition, the lipopolysaceharide (LPS) O-chain deficient phenotype of A449 mutant strain TM4, which has the abcA gene interrupted by ISA1, was also complemented by abcA. DNA sequence analysis showed that the abcA gene coded for a 308 amino acid residue protein, which was confirmed by in vivo and in vitro expression and gene fusion with lacZ, and was localized in the inner membrane fraction of E. coli. At the N-terminal part of the protein, the predicted sequence of AbcA displayed high homology with a bacterial transport protein super family, including a well conserved nucleotide binding sequence. This binding sequence was shown by site-directed mutagenesis to be required for LPS O-chain complementation in TM4. ATP binding activity was confirmed in the purified AbcA-LacZ fusion protein. A leucine zipper-basic region sequence with predominantly α-helical conformation was predicted further downstream, with leucine residues in four of the five heptad repeats and a valine residue in the remaining heptad repeat. / Graduate

As bactérias do gênero Aeromonas são importantes microrganismos aquáticos e agentes causais de doenças infecciosas em animais, inclusive o homem. Sua ampla distribuição em ambientes aquáticos continentais e marinhos é indicativa da sua capacidade de adaptação a distintos níveis de salinidade, fato por sua vez relevante na contaminação de alimentos. A tolerância bacteriana ao estresse salino está associada à manutenção da homeostase celular através de sistemas de transporte de íons e acúmulo de solutos orgânicos, como betaína, prolina, entre outros. A betaína é um osmoprotetor encontrado em plantas, animais e microrganismos sendo transportado em bactérias através de um sistema de transporte do tipo ABC específico codificado pelo operon ProU. Neste contexto, os objetivos deste trabalho foram: avaliar a tolerância ao estresse salino em Aeromonas, incluindo determinar o crescimento e a viabilidade celular em Aeromonas em estresse salino, avaliar a expressão dos genes de transporte de betaína após estresse salino e realizar uma análise in silico do operon proU em bactérias Gram negativas. Os resultados mostram que Aeromonas trota apresenta mais tolerância à salinidade do que Aeromonas hydrophila, sendo que algumas espécies de Aeromonas podem crescer em meio mínimo contendo até 0,42M de NaCl, concentração utilizada como agente de preservação de alimentos. A betaína atua como osmoprotetor em Aeromonas, determinando a sua capacidade de sobrevivência e crescimento em concentrações mais elevadas de cloreto de sódio (0,51 a 0,68M). Por outro lado, a colina, considerada importante precursor da betaína em algumas bactérias, não apresenta efeito osmoprotetor em Aeromonas. Avaliação de pré-crescimento com betaína mostram que este osmoprotetor é acumulado mesmo na ausência de estresse, determinando uma pré-adaptação bacteriana a mudanças de osmolaridade. Análise in silico do operon proU, responsável pelo transporte de betaína, mostra elevada conservação do mesmo em bactérias, indicando a importância deste transportador ABC. Experimentos de expressão do operon proU em A. hdydrophila mostraram expressão constitutiva basal e aumento significativo da expressão do operon proU em bactérias submetidas a estresse osmótico, mesmo na ausência do osmoprotetor. Assim sendo, a expressão do operon proU em A. hydrophila é modulada pelo estresse intracelular, de tal forma que a mesma volta a níveis próximos do basal quando a célula atinge a homeostase. / Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-16T12:41:24Z No. of bitstreams: 1 Dissertacao Evanise Visentini.pdf: 1544112 bytes, checksum: 79ad3b4bbbad93df773fea021178cdd0 (MD5) / Made available in DSpace on 2014-06-16T12:41:24Z (GMT). No. of bitstreams: 1 Dissertacao Evanise Visentini.pdf: 1544112 bytes, checksum: 79ad3b4bbbad93df773fea021178cdd0 (MD5) / The bacteria from the Aeromonas genus are important aquatic microorganisms and causative agents of infectious diseases in animals, and even to mankind. Its wide distribution in continental aquatic and marine environments is an indicative of its ability to adapt to different levels of salinity, which is a relevant fact concerning food contamination. The bacterial tolerance to saline stress is associated with the maintenance of cellular homeostasis through ion transportation systems and the accumulation of organic solutes, such as betaine, proline, among others. Betaine is an osmoprotectant found in plants, animals and microorganisms, transported in bacteria by a transportation system of the ABC specific type, encoded by operon ProU. In this context, the objectives of this study were: to measure the tolerance to saline stress in Aeromonas, including determining the growth and cell viability in Aeromonas in saline stress, evaluate the expression of betaine transport genes after saline stress and create an in silico analysis of the proU operon in Gram negative bacteria. The results demonstrate that Aeromonas trota present more salinity tolerance than Aeromonas hydrophila, and that some Aeromonas species can grow in minimal environment containing up to 0.42 M of NaCl, concentration used as a food preservative agent. The betaine acts as an osmoprotectant in Aeromonas, determining their capacity to survive and grow in higher concentrations of sodium chloride (0.51 to 0.68 M). On the other hand, the choline, considered as an important betaine precursor in some bacteria, presents no osmoprotectant effect on Aeromonas. The evaluation of pre-growth with betaine show that this osmoprotectant is accumulated even in the absence of stress, determining a bacterial pre-adaptation to changes in osmolarity. The in silico analysis of the operon proU, responsible for betaine transportation, shows their high conservation in bacteria, indicating the importance of this ABC transporter. Expression experiments of the operon proU in A. hdydrophila showed constitutive basal expression and significant increase of the operon proU expression in bacteria exposed to osmotic stress, even in the absence of the osmoprotectant. Therefore, the operon proU expression in A. hydrophila is modulated by intracellular stress, in such manner, that it returns to close baseline levels when the cell reaches homeostasis.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2015-05-28T14:19:03Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE Lívia Christina Alves da Silva.pdf: 1170035 bytes, checksum: 96b18862f19b9793a3fc764d10ee4638 (MD5) / Made available in DSpace on 2015-05-28T14:19:03Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE Lívia Christina Alves da Silva.pdf: 1170035 bytes, checksum: 96b18862f19b9793a3fc764d10ee4638 (MD5) Previous issue date: 2015-03-04 / Aeromonas são habitantes nativos de ambientes aquáticos e, recentemente, têm sido considerados patógenos humanos emergentes. As gastroenterites são as infecções mais comumente relacionadas a esse gênero. Nesse estudo, 119 isolados clínicos e ambientais de Aeromonas, obtidos durante um surto de diarreia ocorrido em São Bento do Una, Pernambuco, foram avaliados quanto à prevalência das espécies, estrutura genética da população e potencial de virulência. A análise das sequências dos genes 16S rRNA e gyrB revelou a predominância de A. caviae (66,4%), seguida por A. veronii (14,2%); A. aquariorum (9,2%); A. hydrophila e A. trota (3,4%) e A. jandaei (1,7%). Dois isolados não foram identificados entre as espécies conhecidas de Aeromonas, sugerindo pertencerem a novas espécies. A rede filogenética construída com base no gene 16S rRNA revelou uma estrutura populacional epidêmica, envolvendo quase todos os isolados de A. caviae, sendo possível identificar um genótipo fundador e seus descendentes. Os genes de virulência alt, ast e hlyA foram detectados entre os isolados com frequências de 81,5%; 13,4% e 11,8%, respectivamente. Este estudo revelou que a análise filogenética de sequências concatenadas dos genes 16S rRNA e gyrB é um eficiente marcador taxonômico para o gênero Aeromonas. Foi detectado elevado potencial de virulência entre as espécies de Aeromonas identificadas, principalmente entre A. hydrophila, A. aquariorum e A. caviae. As características marcantes observadas sugerem que a espécie A. caviae teve importante participação nos casos de diarreia relatados em São Bento do Una, Pernambuco.

As bactérias do gênero Aeromonas são importantes microrganismos aquáticos e agentes causais de doenças infecciosas em animais, inclusive o homem. Sua ampla distribuição em ambientes aquáticos continentais e marinhos é indicativa da sua capacidade de adaptação a distintos níveis de salinidade, fato por sua vez relevante na contaminação de alimentos. A tolerância bacteriana ao estresse salino está associada à manutenção da homeostase celular através de sistemas de transporte de íons e acúmulo de solutos orgânicos, como betaína, prolina, entre outros. A betaína é um osmoprotetor encontrado em plantas, animais e microrganismos sendo transportado em bactérias através de um sistema de transporte do tipo ABC específico codificado pelo operon ProU. Neste contexto, os objetivos deste trabalho foram: avaliar a tolerância ao estresse salino em Aeromonas, incluindo determinar o crescimento e a viabilidade celular em Aeromonas em estresse salino, avaliar a expressão dos genes de transporte de betaína após estresse salino e realizar uma análise in silico do operon proU em bactérias Gram negativas. Os resultados mostram que Aeromonas trota apresenta mais tolerância à salinidade do que Aeromonas hydrophila, sendo que algumas espécies de Aeromonas podem crescer em meio mínimo contendo até 0,42M de NaCl, concentração utilizada como agente de preservação de alimentos. A betaína atua como osmoprotetor em Aeromonas, determinando a sua capacidade de sobrevivência e crescimento em concentrações mais elevadas de cloreto de sódio (0,51 a 0,68M). Por outro lado, a colina, considerada importante precursor da betaína em algumas bactérias, não apresenta efeito osmoprotetor em Aeromonas. Avaliação de pré-crescimento com betaína mostram que este osmoprotetor é acumulado mesmo na ausência de estresse, determinando uma pré-adaptação bacteriana a mudanças de osmolaridade. Análise in silico do operon proU, responsável pelo transporte de betaína, mostra elevada conservação do mesmo em bactérias, indicando a importância deste transportador ABC. Experimentos de expressão do operon proU em A. hdydrophila mostraram expressão constitutiva basal e aumento significativo da expressão do operon proU em bactérias submetidas a estresse osmótico, mesmo na ausência do osmoprotetor. Assim sendo, a expressão do operon proU em A. hydrophila é modulada pelo estresse intracelular, de tal forma que a mesma volta a níveis próximos do basal quando a célula atinge a homeostase. / The bacteria from the Aeromonas genus are important aquatic microorganisms and causative agents of infectious diseases in animals, and even to mankind. Its wide distribution in continental aquatic and marine environments is an indicative of its ability to adapt to different levels of salinity, which is a relevant fact concerning food contamination. The bacterial tolerance to saline stress is associated with the maintenance of cellular homeostasis through ion transportation systems and the accumulation of organic solutes, such as betaine, proline, among others. Betaine is an osmoprotectant found in plants, animals and microorganisms, transported in bacteria by a transportation system of the ABC specific type, encoded by operon ProU. In this context, the objectives of this study were: to measure the tolerance to saline stress in Aeromonas, including determining the growth and cell viability in Aeromonas in saline stress, evaluate the expression of betaine transport genes after saline stress and create an in silico analysis of the proU operon in Gram negative bacteria. The results demonstrate that Aeromonas trota present more salinity tolerance than Aeromonas hydrophila, and that some Aeromonas species can grow in minimal environment containing up to 0.42 M of NaCl, concentration used as a food preservative agent. The betaine acts as an osmoprotectant in Aeromonas, determining their capacity to survive and grow in higher concentrations of sodium chloride (0.51 to 0.68 M). On the other hand, the choline, considered as an important betaine precursor in some bacteria, presents no osmoprotectant effect on Aeromonas. The evaluation of pre-growth with betaine show that this osmoprotectant is accumulated even in the absence of stress, determining a bacterial pre-adaptation to changes in osmolarity. The in silico analysis of the operon proU, responsible for betaine transportation, shows their high conservation in bacteria, indicating the importance of this ABC transporter. Expression experiments of the operon proU in A. hdydrophila showed constitutive basal expression and significant increase of the operon proU expression in bacteria exposed to osmotic stress, even in the absence of the osmoprotectant. Therefore, the operon proU expression in A. hydrophila is modulated by intracellular stress, in such manner, that it returns to close baseline levels when the cell reaches homeostasis.

Aeromonas salmonicida sous-espèce salmonicida est un agent pathogène opportuniste responsable chaque année d’importantes pertes économiques pour les aquaculteurs de Salmonidés. Dans cette étude, plusieurs analyses ont été effectuées dans l’objectif de trouver une méthode pour distinguer entre différents isolats de cette bactérie au niveau génomique. Suite à l’alignement chromosomique des souches A449 et 01-B526, trente-deux altérations génomiques ont été répertoriées et elles peuvent être classées en cinq groupes : séquences d’insertions (13), séquences répétées en tandem (12), séquences insérées dans des gènes (5), site de polymorphisme multi-évènementiel (1) et îlot génomique (AsaGEI1a) (1). Des criblages PCR et des séquençages génomiques ont révélé l’existence de trois autres îlots génomiques (AsaGEI1b; AsaGEI2a; AsaGEI2b). Chaque AsaGEI est hautement spécifique à une région géographique. Les AsaGEI(1a; 2a) sont seulement observés en Amérique du Nord et les AsaGEI(1b; 2b) en Europe. Dans ces travaux, plusieurs marqueurs pouvant permettre d’identifier l’origine géographique des souches pathogènes ont été découverts. / Aeromonas salmonicida subsp. salmonicida is an opportunistic pathogen, which causes significant economic loss in salmonid aquaculture. In this work, analyses were conducted with the objective to find a way to distinguish between different isolates of the bacterium at the genomic level. Following the chromosomal alignment between A449 and 01-B526 strains, thirty-two genomic alterations were found and were classified in five groups: insertion sequences (13), tandem repeat sequences (12), CDS-modeling sequences (5), multi-event polymorphism site (1) and genomic island (AsaGEI1a) (1). PCR assays and genomic sequencing revealed the existence of four forms (AsaGEI(1a; 1b; 2a; 2b)) of the genomic island. Each GEI appeared to be strongly associated with a specific geographic region. AsaGEI(1a; 2a) were exclusively found in North American isolates and AsaGEI(1b; 2b) in those from Europe. In this study, several indicators useful to identify the geographical origin of pathogenic strains of this bacterium were discovered.

Wretlind, Heden, and Wadstrom found ammonium sulfate to be inhibitory for the formation of extracellular protease in Aeromonas hydrophila grown in Brain Heart Infusion medium. They demonstrated by manipulating the iron and zinc content within their medium that it is possible to differentially affect the accumulation of hemolysin and protease by A. hydrophila grown in batch culture. Further manipulation of the composition of this medium was done in the present study to determine the effect of other components on the production of protease. The purpose of this study was to determine the factors affecting the level of A. hydrophila protease produced in a chemically defined medium.