Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 6 de 6
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Appl Environ Microbiol ; 82(15): 4802-4810, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27235441

RESUMO

UNLABELLED: Minimizing the use of antibiotics in the food production chain is essential for limiting the development and spread of antibiotic-resistant bacteria. One alternative intervention strategy is the use of probiotic bacteria, and bacteria of the marine Roseobacter clade are capable of antagonizing fish-pathogenic vibrios in fish larvae and live feed cultures for fish larvae. The antibacterial compound tropodithietic acid (TDA), an antiporter that disrupts the proton motive force, is key in the antibacterial activity of several roseobacters. Introducing probiotics on a larger scale requires understanding of any potential side effects of long-term exposure of the pathogen to the probionts or any compounds they produce. Here we exposed the fish pathogen Vibrio anguillarum to TDA for several hundred generations in an adaptive evolution experiment. No tolerance or resistance arose during the 90 days of exposure, and whole-genome sequencing of TDA-exposed lineages and clones revealed few mutational changes, compared to lineages grown without TDA. Amino acid-changing mutations were found in two to six different genes per clone; however, no mutations appeared unique to the TDA-exposed lineages or clones. None of the virulence genes of V. anguillarum was affected, and infectivity assays using fish cell lines indicated that the TDA-exposed lineages and clones were less invasive than the wild-type strain. Thus, long-term TDA exposure does not appear to result in TDA resistance and the physiology of V. anguillarum appears unaffected, supporting the application of TDA-producing roseobacters as probiotics in aquaculture. IMPORTANCE: It is important to limit the use of antibiotics in our food production, to reduce the risk of bacteria developing antibiotic resistance. We showed previously that marine bacteria of the Roseobacter clade can prevent or reduce bacterial diseases in fish larvae, acting as probiotics. Roseobacters produce the antimicrobial compound tropodithietic acid (TDA), and we were concerned regarding whether long-term exposure to this compound could induce resistance or affect the disease-causing ability of the fish pathogen. Therefore, we exposed the fish pathogen Vibrio anguillarum to increasing TDA concentrations over 3 months. We did not see the development of any resistance to TDA, and subsequent infection assays revealed that none of the TDA-exposed clones had increased virulence toward fish cells. Hence, this study supports the use of roseobacters as a non-risk-based disease control measure in aquaculture.


Assuntos
Antibacterianos/farmacologia , Doenças dos Peixes/microbiologia , Tropolona/análogos & derivados , Vibrioses/veterinária , Vibrio/efeitos dos fármacos , Animais , Farmacorresistência Bacteriana , Peixes , Genótipo , Fenótipo , Tropolona/farmacologia , Vibrio/genética , Vibrio/patogenicidade , Vibrio/fisiologia , Vibrioses/microbiologia , Virulência/efeitos dos fármacos
2.
Appl Environ Microbiol ; 82(2): 502-9, 2016 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-26519388

RESUMO

Tropodithietic acid (TDA) is an antibacterial compound produced by some Phaeobacter and Ruegeria spp. of the Roseobacter clade. TDA production is studied in marine broth or agar since antibacterial activity in other media is not observed. The purpose of this study was to determine how TDA production is influenced by substrate components. High concentrations of ferric citrate, as present in marine broth, or other iron sources were required for production of antibacterially active TDA. However, when supernatants of noninhibitory, low-iron cultures of Phaeobacter inhibens were acidified, antibacterial activity was detected in a bioassay. The absence of TDA in nonacidified cultures and the presence of TDA in acidified cultures were verified by liquid chromatography-high-resolution mass spectrometry. A noninhibitory TDA analog (pre-TDA) was produced by P. inhibens, Ruegeria mobilis F1926, and Phaeobacter sp. strain 27-4 under low-iron concentrations and was instantaneously converted to TDA when pH was lowered. Production of TDA in the presence of Fe(3+) coincides with formation of a dark brown substance, which could be precipitated by acid addition. From this brown pigment TDA could be liberated slowly with aqueous ammonia, and both direct-infusion mass spectrometry and elemental analysis indicated a [Fe(III)(TDA)2]x complex. The pigment could also be produced by precipitation of pure TDA with FeCl3. Our results raise questions about how biologically active TDA is produced in natural marine settings where iron is typically limited and whether the affinity of TDA to iron points to a physiological or ecological function of TDA other than as an antibacterial compound.


Assuntos
Antibacterianos/biossíntese , Ferro/metabolismo , Rhodobacteraceae/metabolismo , Tropolona/análogos & derivados , Antibacterianos/química , Espectrometria de Massas , Estrutura Molecular , Rhodobacteraceae/genética , Tropolona/química , Tropolona/metabolismo
3.
Environ Microbiol ; 16(5): 1252-66, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24118907

RESUMO

In many species of the marine Roseobacter clade, periods of attached life, in association with phytoplankton or particles, are interspersed with planktonic phases. The purpose of this study was to determine whether shifts between motile and sessile life in the globally abundant Roseobacter clade species Ruegeria mobilis are associated with intracellular concentrations of the signal compound cyclic dimeric guanosinmonophosphate (c-di-GMP), which in bacteria regulates transitions between motile and sessile life stages. Genes for diguanylate cyclases and phosphodiesterases, which are involved in c-di-GMP signalling, were found in the genome of R. mobilis strain F1926. Ion pair chromatography-tandem mass spectrometry revealed 20-fold higher c-di-GMP concentrations per cell in biofilm-containing cultures than in planktonic cells. An introduced diguanylate cyclase gene increased c-di-GMP and enhanced biofilm formation and production of the potent antibiotic tropodithietic acid (TDA). An introduced phosphodiesterase gene decreased c-di-GMP and reduced biofilm formation and TDA production. tdaC, a key gene for TDA biosynthesis, was expressed only in attached or biofilm-forming cells, and expression was induced immediately after initial attachment. In conclusion, c-di-GMP signalling controls biofilm formation and biofilm-associated traits in R. mobilis and, as suggested by presence of GGDEF and EAL domain protein genes, also in other Roseobacter clade species.


Assuntos
Antibacterianos/biossíntese , Biofilmes/crescimento & desenvolvimento , GMP Cíclico/análogos & derivados , Rhodobacteraceae/fisiologia , Tropolona/análogos & derivados , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , GMP Cíclico/metabolismo , Proteínas de Escherichia coli/genética , Dados de Sequência Molecular , Diester Fosfórico Hidrolases/genética , Fósforo-Oxigênio Liases/genética , Estrutura Terciária de Proteína , Rhodobacteraceae/metabolismo , Tropolona/metabolismo
4.
PLoS One ; 7(8): e43996, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22928051

RESUMO

Phaeobacter gallaeciensis can antagonize fish-pathogenic bacteria in vitro, and the purpose of this study was to evaluate the organism as a probiont for marine fish larvae and their feed cultures. An in vivo mechanism of action of the antagonistic probiotic bacterium is suggested using a non-antagonistic mutant. P. gallaeciensis was readily established in axenic cultures of the two microalgae Tetraselmis suecica and Nannochloropsis oculata, and of the rotifer Brachionus plicatilis. P. gallaeciensis reached densities of 10(7) cfu/ml and did not adversely affect growth of algae or rotifers. Vibrio anguillarum was significantly reduced by wild-type P. gallaeciensis, when introduced into these cultures. A P. gallaeciensis mutant that did not produce the antibacterial compound tropodithietic acid (TDA) did not reduce V. anguillarum numbers, suggesting that production of the antibacterial compound is important for the antagonistic properties of P. gallaeciensis. The ability of P. gallaeciensis to protect fish larvae from vibriosis was determined in a bath challenge experiment using a multidish system with 1 larva per well. Unchallenged larvae reached 40% accumulated mortality which increased to 100% when infected with V. anguillarum. P. gallaeciensis reduced the mortality of challenged cod larvae (Gadus morhua) to 10%, significantly below the levels of both the challenged and the unchallenged larvae. The TDA mutant reduced mortality of the cod larvae in some of the replicates, although to a much lesser extent than the wild type. It is concluded that P. gallaeciensis is a promising probiont in marine larviculture and that TDA production likely contributes to its probiotic effect.


Assuntos
Doenças dos Peixes/prevenção & controle , Gadus morhua/microbiologia , Microalgas/microbiologia , Rhodobacteraceae/fisiologia , Rotíferos/microbiologia , Vibrioses/veterinária , Vibrio/patogenicidade , Animais , Clorófitas/crescimento & desenvolvimento , Clorófitas/microbiologia , Técnicas de Cultura , Doenças dos Peixes/microbiologia , Larva/microbiologia , Microalgas/crescimento & desenvolvimento , Probióticos , Rotíferos/crescimento & desenvolvimento , Estramenópilas/crescimento & desenvolvimento , Estramenópilas/microbiologia , Vibrioses/microbiologia , Vibrioses/prevenção & controle
5.
FEMS Microbiol Lett ; 312(1): 84-92, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20846143

RESUMO

Adherent growth of Pseudomonas putida KT2440 with and without the TOL plasmid (pWWO) at the solid-liquid and air-liquid interface was examined. We compared biofilm formation on glass in flow cells, and assayed pellicle (air-liquid interface biofilm) formation in stagnant liquid cultures by confocal laser scanning microscopy. The TOL-carrying strains formed pellicles and thick biofilms, whereas the same strains without the plasmid displayed little adherent growth. Microscopy using fluorescent nucleic acid-specific stains revealed differences in the production of extracellular polymeric substances: TOL carriage leads to more extracellular DNA (eDNA) in pellicles and biofilms. Pellicles were dissolved by DNase I treatment. Enhanced cell lysis due to plasmid carriage was ruled out as the mechanism for eDNA release. We report, for the first time, that carriage of a conjugative plasmid leads to increased biofilm formation by production of eDNA.


Assuntos
Biofilmes , DNA Bacteriano/metabolismo , Espaço Extracelular/genética , Espaço Extracelular/metabolismo , Plasmídeos/genética , Pseudomonas putida/fisiologia , DNA Bacteriano/genética , Espaço Extracelular/química , Plasmídeos/metabolismo , Pseudomonas putida/química , Pseudomonas putida/genética
6.
Appl Environ Microbiol ; 76(7): 2366-70, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20118354

RESUMO

The purpose of the present study was to investigate the inhibition of Vibrio by Roseobacter in a combined liquid-surface system. Exposure of Vibrio anguillarum to surface-attached roseobacters (10(7) CFU/cm(2)) resulted in significant reduction or complete killing of the pathogen inoculated at 10(2) to 10(4) CFU/ml. The effect was likely associated with the production of tropodithietic acid (TDA), as a TDA-negative mutant did not affect survival or growth of V. anguillarum.


Assuntos
Antibiose , Viabilidade Microbiana , Roseobacter/fisiologia , Vibrio/fisiologia , Microbiologia da Água , Antibacterianos/metabolismo , Antibacterianos/farmacologia , Contagem de Colônia Microbiana , Tropolona/análogos & derivados , Tropolona/metabolismo , Tropolona/farmacologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...