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1.
Environ Pollut ; 260: 114051, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32369896

RESUMO

Soil contamination by toxic heavy metals such as copper is a serious problem. In this study, the extracellular polymeric substance (EPS) extracted from Rahnella sp. LRP3 was found with the potential of immobilizing Cu-polluted in soil. The EPS could bond to Cu (II) through functional groups (polysaccharides, amide, proteins, and carboxyl groups), which further developed into the porous sphere with a diameter of 20 µm. Besides, EPS could induce the formation of Cu5(PO4)2(OH)4 crystal by the biomineralization process. Finally, the EPS in the culture solution reduced 89.4 mg/kg of DTPA-Cu content by 78.99% in soil for 10 d under the condition of 25 °C via biomineralization. The results demonstrated that EPS produced by Rahnella sp. LRP3 will be a promising factor in the remediation of Cu contaminated soil.


Assuntos
Biomineralização , Cobre/química , Matriz Extracelular de Substâncias Poliméricas , Rahnella/fisiologia , Solo/química , Rahnella/efeitos dos fármacos
2.
Chemosphere ; 237: 124452, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31376699

RESUMO

Pollution of the environment with chlorinated aromatic compounds is a problem of increasing importance, which has stimulated the search for efficient methods for the remediation of contaminated soil and water. Additionally, for better understanding of the significance of bioavailability to biodegradation, investigation of the cell surface properties is necessary. Hence, this study concerns the properties and possible application, in chlorotoluene removal, of three newly isolated environmental bacterial strains from the genera Pseudomonas, Raoultella and Rahnella. The results show the differences in the biochemical profiles of the isolated strains, their cellular fatty acid composition and their hemolytic properties. However, all three strains exhibit high biodegradation potential, degrading not less than 60% of each monochlorotoluene isomer in 21-day experiments. What is more, observations of changes in the cell surface properties indicate the possible adaptation mechanisms of the strains that enable efficient biodegradation of hydrophobic pollutants such as monochlorotoluenes.


Assuntos
Bactérias/metabolismo , Biodegradação Ambiental , Hidrocarbonetos Clorados/metabolismo , Bactérias/química , Enterobacteriaceae/química , Enterobacteriaceae/metabolismo , Pseudomonas/química , Pseudomonas/metabolismo , Rahnella/química , Rahnella/metabolismo , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo , Tolueno/análise , Tolueno/metabolismo
3.
J Appl Microbiol ; 127(3): 812-824, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31161611

RESUMO

AIMS: Bacterial decays of onion bulbs have serious economic consequences for growers, but the aetiologies of these diseases are often unclear. We aimed to determine the role of Rahnella, which we commonly isolated from bulbs in the United States and Norway, in onion disease. METHODS AND RESULTS: Isolated bacteria were identified by sequencing of housekeeping genes and/or fatty acid methyl ester analysis. A subset of Rahnella spp. strains was also assessed by multilocus sequence analysis (MLSA); most onion strains belonged to two clades that appear closely related to R. aquatilis. All tested strains from both countries caused mild symptoms in onion bulbs but not leaves. Polymerase chain reaction primers were designed and tested against strains from known species of Rahnella. Amplicons were produced from strains of R. aquatilis, R. victoriana, R. variigena, R. inusitata and R. bruchi, and from one of the two strains of R. woolbedingensis. CONCLUSIONS: Based on binational testing, strains of Rahnella are commonly associated with onions, and they are capable of causing mild symptoms in bulbs. SIGNIFICANCE AND IMPACT OF THE STUDY: While Rahnella strains are commonly found within field-grown onions and they are able to cause mild symptoms, the economic impact of Rahnella-associated symptoms remains unclear.


Assuntos
Cebolas/microbiologia , Rahnella/fisiologia , Genes Essenciais , New York , Noruega , Filogenia , Doenças das Plantas/microbiologia , Folhas de Planta/microbiologia , Raízes de Plantas/microbiologia , Reação em Cadeia da Polimerase , Rahnella/genética , Rahnella/isolamento & purificação
4.
J Appl Microbiol ; 126(4): 1096-1107, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30706635

RESUMO

AIMS: Rahnella aquatilis is a Gram-negative bacterial species with potential for agricultural and industrial applications, as well as a human pathogen. This study aims to identify an optimal reference gene to explore antibiotic resistance and stress tolerance in R. aquatilis using reverse-transcription quantitative polymerase chain reaction (RT-qPCR). METHODS AND RESULTS: Expression levels of 14 housekeeping genes in R. aquatilis were estimated by RT-qPCR under six different conditions: exponential phase, stationary phase, acid, salinity, antibiotic and oxidative stresses. BestKeeper and the ΔCt method were used to evaluate the stability of each gene. The atpD gene was stably expressed in all conditions, thus was selected and validated as an optimal reference gene. Transcript levels of 17 putative ampicillin-resistance genes in R. aquatilis strain HX2 were evaluated using the proposed RT-qPCR. Six genes encoding efflux transporters and ß-lactamase were overexpressed after ampicillin treatment. Additionally, the expression of seven putative stress response genes in strain HX2 was assessed, and five genes were up-regulated by respective stress treatments. CONCLUSIONS: The atpD gene has been identified as an optimal reference gene for expression analysis of R. aquatilis responses to abiotic stresses by RT-qPCR. SIGNIFICANCE AND IMPACT OF THE STUDY: The proposed RT-qPCR is suitable for gene expression analysis in R. aquatilis, thus useful for studying antimicrobial resistance and stress tolerance in this bacterium and others closely related.


Assuntos
Resistência Microbiana a Medicamentos/genética , Perfilação da Expressão Gênica/normas , Genes Bacterianos/genética , Rahnella/genética , Estresse Fisiológico/genética , Antibacterianos/metabolismo , Regulação Bacteriana da Expressão Gênica , Genes Essenciais/genética , Rahnella/fisiologia , Reação em Cadeia da Polimerase em Tempo Real/normas , Padrões de Referência
5.
J Basic Microbiol ; 59(4): 402-411, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30644572

RESUMO

Rahnella aquatilis HX2 was isolated from Beijing vineyard soil and used as a plant growth-promoting rhizobacterium in the field. Previous studies have shown that it has a broad in vitro antimicrobial spectrum and could inhibit a variety of plant pathogenic bacteria and fungi. In this study, a gene, acdS, encoding 1-aminocyclopropane-1-carboxylic acid-deaminase was disrupted by in-frame deletion in the HX2 strain. Compared to the wild-type, the acdS-mutant had higher rates of nitrogen fixation, reduced indole-3-acetic acid production, lowered efficacy as a biological control agent against the grape crown gall pathogen Agrobacterium vitis. Under saline stress conditions, plant height, above-ground fresh weight, root fresh weight of corn plants were increased by treatment with HX2 but this increase was compromised by the disruption of acdS gene. Our data confirmed the function of HX2 on plant growth promoting and demonstrated that acdS gene plays a major role in its PGPR activities.


Assuntos
Proteínas de Bactérias/genética , Carbono-Carbono Liases/genética , Rahnella/fisiologia , Tolerância ao Sal , Zea mays/fisiologia , Agrobacterium , Antibacterianos/metabolismo , Germinação , Ácidos Indolacéticos/metabolismo , Mutação , Nitrogenase/metabolismo , Rahnella/genética , Rahnella/metabolismo , Zea mays/crescimento & desenvolvimento
6.
Microb Genom ; 5(1)2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30625111

RESUMO

The UK's native oak is under serious threat from Acute Oak Decline (AOD). Stem tissue necrosis is a primary symptom of AOD and several bacteria are associated with necrotic lesions. Two members of the lesion pathobiome, Brenneria goodwinii and Gibbsiella quercinecans, have been identified as causative agents of tissue necrosis. However, additional bacteria including Lonsdalea britannica and Rahnella species have been detected in the lesion microbiome, but their role in tissue degradation is unclear. Consequently, information on potential genome-encoded mechanisms for tissue necrosis is critical to understand the role and mechanisms used by bacterial members of the lesion pathobiome in the aetiology of AOD. Here, the whole genomes of bacteria isolated from AOD-affected trees were sequenced, annotated and compared against canonical bacterial phytopathogens and non-pathogenic symbionts. Using orthologous gene inference methods, shared virulence genes that retain the same function were identified. Furthermore, functional annotation of phytopathogenic virulence genes demonstrated that all studied members of the AOD lesion microbiota possessed genes associated with phytopathogens. However, the genome of B. goodwinii was the most characteristic of a necrogenic phytopathogen, corroborating previous pathological and metatranscriptomic studies that implicate it as the key causal agent of AOD lesions. Furthermore, we investigated the genome sequences of other AOD lesion microbiota to understand the potential ability of microbes to cause disease or contribute to pathogenic potential of organisms isolated from this complex pathobiome. The role of these members remains uncertain but some such as G. quercinecans may contribute to tissue necrosis through the release of necrotizing enzymes and may help more dangerous pathogens activate and realize their pathogenic potential or they may contribute as secondary/opportunistic pathogens with the potential to act as accessory species for B. goodwinii. We demonstrate that in combination with ecological data, whole genome sequencing provides key insights into the pathogenic potential of bacterial species whether they be phytopathogens, part-contributors or stimulators of the pathobiome.


Assuntos
Enterobacteriaceae/genética , Microbiota/genética , Doenças das Plantas/microbiologia , Quercus/microbiologia , Rahnella/genética , Doenças das Plantas/genética
7.
Mycorrhiza ; 29(1): 69-75, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30368606

RESUMO

An increasing number of studies have demonstrated that arbuscular mycorrhizal fungi can cooperate with other soil microorganisms, e.g., bacteria, which develop near or on the surface of the extraradical hyphae where they perform multiple functions. However, the mechanisms involved in this privileged relationship are still poorly known. In the present study, we investigated how the arbuscular mycorrhizal fungus Rhizophagus irregularis MUCL 43194 influences the three pace-making enzymes (i.e., citrate synthase, isocitrate dehydrogenase, and α-oxoglutarate dehydrogenase) of the tricarboxylic acid (TCA) cycle in the phosphate-solubilizing bacterium Rahnella aquatilis HX2. The study was conducted under strict in vitro culture conditions and analysis made at the transcriptional level. Results showed that R. irregularis induced the expression of the gene-encoding citrate synthase (gltA), the pace-making enzyme involved in the first step of the TCA cycle, in R. aquatilis at all time points of observation (i.e., 1, 6, 12, 24, 48, and 72 h). The expression of the gene-encoding isocitrate dehydrogenase (icd) significantly decreased at 6, 12, 24, 48, and 72 h and the expression of the gene-encoding α-oxoglutarate dehydrogenase E1 component (kgdhc) significantly increased at 1, 6, and 48 h. The above results suggested that R. irregularis may influence the level of adenosine triphosphate production in R. aquatilis and thus the metabolism of the bacterium by stimulating the expression of gltA involved in the TCA cycle. Our results suggest a fine-tuned dialog between R. irregularis MUCL 43194 and R. aquatilis HX2 and emphasize the complexity of the interactions that might take place at the hyphal surface of arbuscular mycorrhizal fungi hosting communities of microbes.


Assuntos
Proteínas de Bactérias/genética , Citrato (si)-Sintase/genética , Glomeromycota/fisiologia , Rahnella/genética , Transcrição Genética , Proteínas de Bactérias/metabolismo , Citrato (si)-Sintase/metabolismo , Ciclo do Ácido Cítrico , Isocitrato Desidrogenase/genética , Isocitrato Desidrogenase/metabolismo , Complexo Cetoglutarato Desidrogenase/genética , Complexo Cetoglutarato Desidrogenase/metabolismo , Micorrizas/fisiologia , Fosfatos/metabolismo , Rahnella/metabolismo
8.
ISME J ; 12(10): 2339-2351, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-29899507

RESUMO

Cooperation is a prevalent phenomenon in nature and how it originates and maintains is a fundamental question in ecology. Many efforts have been made to understand cooperation between individuals in the same species, while the mechanisms enabling cooperation between different species are less understood. Here, we investigated under strict in vitro culture conditions if the exchange of carbon and phosphorus is pivotal to the cooperation between the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis and the phosphate solubilizing bacterium (PSB) Rahnella aquatilis. We observed that fructose exuded by the AMF stimulated the expression of phosphatase genes in the bacterium as well as the rate of phosphatase release into the growth medium by regulating its protein secretory system. The phosphatase activity was subsequently increased, promoting the mineralization of organic phosphorus (i.e., phytate) into inorganic phosphorus, stimulating simultaneously the processes involved in phosphorus uptake by the AMF. Our results demonstrated for the first time that fructose not only is a carbon source, but also plays a role as a signal molecule triggering bacteria-mediated organic phosphorus mineralization processes. These results highlighted the molecular mechanisms by which the hyphal exudates play a role in maintaining the cooperation between AMF and bacteria.


Assuntos
Frutose/metabolismo , Micorrizas/fisiologia , Fosfatos/metabolismo , Ácido Fítico/metabolismo , Rahnella/metabolismo , Carbono/metabolismo , Frutose/farmacologia , Glomeromycota/genética , Hifas/metabolismo , Nutrientes , Rahnella/efeitos dos fármacos
9.
Appl Microbiol Biotechnol ; 102(14): 6191-6205, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29806064

RESUMO

Rahnella aquatilis HX2 (proteobacteria) shows tolerance to selenium (Se). The minimum inhibitory concentrations of selenomethionine (Se-Met), selenite [Se (IV)], and selenate [Se (VI)] to HX2 are 4.0, 85.0, and 590.0 mM, respectively. HX2 shows the ability to reduce Se (IV) and Se (VI) to elemental Se nanoparticles (SeNPs). The maximum production of SeNPs by HX2 strain is 1.99 and 3.85 mM in Luria-Bertani (LB) broth with 5 mM Se (IV) and 10 mM Se (VI), respectively. The morphology of SeNPs and cells were observed by transmission electron microscope, environmental scanning electron microscope, and selected area electric diffraction detector. Spherical SeNPs with amorphous structure were found in the cytoplasm, membrane, and exterior of cells. Morphological variations of the cell membrane were further confirmed by the release of cellular materials absorbed at 260 nm. Flagella were inhibited and cell sizes were 1.8-, 1.6-, and 1.2-fold increases with the Se-Met, Se (VI), and Se (IV) treatments, respectively. The real-time quantitative PCR analysis indicated that some of the genes controlling Se metabolism or cell morphology, including cysA, cysP, rodA, ZntA, and ada, were significantly upregulated, while grxA, fliO, flgE, and fliC genes were significantly downregulated in those Se treatments. This study provided novel valuable information concerning the cell morphology along with biological synthesis process of SeNPs in R. aquatilis and demonstrated that the strain HX2 could be applied in both biosynthesis of SeNPs and in management of environmental Se pollution.


Assuntos
Nanopartículas , Rahnella/efeitos dos fármacos , Ácido Selênico/farmacologia , Ácido Selenioso/farmacologia , Selênio/química , Selenometionina/farmacologia , Antibacterianos/farmacologia , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Testes de Sensibilidade Microbiana , Rahnella/citologia , Rahnella/crescimento & desenvolvimento
10.
ISME J ; 12(2): 386-399, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29028005

RESUMO

Decline-diseases are complex and becoming increasingly problematic to tree health globally. Acute Oak Decline (AOD) is characterized by necrotic stem lesions and galleries of the bark-boring beetle, Agrilus biguttatus, and represents a serious threat to oak. Although multiple novel bacterial species and Agrilus galleries are associated with AOD lesions, the causative agent(s) are unknown. The AOD pathosystem therefore provides an ideal model for a systems-based research approach to address our hypothesis that AOD lesions are caused by a polymicrobial complex. Here we show that three bacterial species, Brenneria goodwinii, Gibbsiella quercinecans and Rahnella victoriana, are consistently abundant in the lesion microbiome and possess virulence genes used by canonical phytopathogens that are expressed in AOD lesions. Individual and polyspecies inoculations on oak logs and trees demonstrated that B. goodwinii and G. quercinecans cause tissue necrosis and, in combination with A. biguttatus, produce the diagnostic symptoms of AOD. We have proved a polybacterial cause of AOD lesions, providing new insights into polymicrobial interactions and tree disease. This work presents a novel conceptual and methodological template for adapting Koch's postulates to address the role of microbial communities in disease.


Assuntos
Besouros/microbiologia , Enterobacteriaceae/genética , Microbiota , Doenças das Plantas/microbiologia , Quercus/microbiologia , Rahnella/genética , Algoritmos , Animais , Enterobacteriaceae/patogenicidade , Genoma Bacteriano , Genoma de Planta , Metagenoma , Necrose , Filogenia , Rahnella/patogenicidade , Biologia de Sistemas , Transcriptoma
11.
PLoS One ; 12(11): e0187492, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29091941

RESUMO

BACKGROUND: Rahnella aquatilis is ubiquitous and its certain strains have the applicative potent as a plant growth-promoting rhizobacteria. R. aquatilis HX2 is a biocontrol agent to produce antibacterial substance (ABS) and showed efficient biocontrol against crown gall caused by Agrobacterium vitis on sunflower and grapevine plants. The regulatory network of the ABS production and biocontrol activity is still limited known. METHODOLOGY/PRINCIPAL FINDINGS: In this study, a transposon-mediated mutagenesis strategy was used to investigate the regulators that involved in the biocontrol activity of R. aquatilis HX2. A 366-nt noncoding RNA CsrB was identified in vitro and in vivo, which regulated ABS production and biocontrol activity against crown gall on sunflower plants, respectively. The predicted product of noncoding RNA CsrB contains 14 stem-loop structures and an additional ρ-independent terminator harpin, with 23 characteristic GGA motifs in the loops and other unpaired regions. CsrB is required for ABS production and biocontrol activity in the biocontrol regulation by a two-component regulatory system BarA/UvrY in R. aquatilis HX2. CONCLUSION/SIGNIFICANCE: The noncoding RNA CsrB regulates BarA-dependent ABS production and biocontrol activity in R. aquatilis HX2. To the best of our knowledge, this is the first report of noncoding RNA as a regulator for biocontrol function in R. aquatilis.


Assuntos
Proteínas de Bactérias/fisiologia , Controle Biológico de Vetores , RNA Bacteriano/fisiologia , RNA não Traduzido/fisiologia , Rahnella/fisiologia , Doenças das Plantas/prevenção & controle , RNA
12.
Dis Aquat Organ ; 123(3): 205-212, 2017 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-28322207

RESUMO

Rahnella aquatilis infection is rare in aquaculture. Here, a Gram-negative rod-shaped bacterium was isolated from diseased crucian carp Carassius auratus in Xuzhou City, Jiangsu Province, eastern China. The isolate was tentatively named strain KCL-5, and subsequently identified as R. aquatilis by biochemical properties and molecular techniques. The results showed that the isolate KCL-5 was most closely related to the type strain ATCC33071 (= DSM4594) of R. aquatilis, which shared 99.67, 96.26 and 99.58% nucleotide sequence identities for 16S rDNA, gyrB and toxin yhaV genes, respectively. Experimental challenges were conducted which demonstrated pathogenicity of the isolate in crucian carp. Antimicrobial susceptibility testing showed that the isolated strain was susceptible to piperacillin, gentamicin, kanamycin, nalidixic acid, norfloxacin, ofloxacin, azithromycin and erythromycin. To our knowledge, this is the first report on R. aquatilis infection in crucian carp, and the first evidence of pathogenicity in fish.


Assuntos
Doenças dos Peixes/microbiologia , Carpa Dourada , Infecções por Bactérias Gram-Negativas/veterinária , Rahnella , Animais , China/epidemiologia , Doenças dos Peixes/epidemiologia , Infecções por Bactérias Gram-Negativas/epidemiologia , Infecções por Bactérias Gram-Negativas/microbiologia , Filogenia , RNA Bacteriano/genética , RNA Ribossômico 16S/genética , Rahnella/genética
13.
Plasmid ; 90: 38-43, 2017 03.
Artigo em Inglês | MEDLINE | ID: mdl-28300545

RESUMO

pHW126 belongs to a small group of rolling circle plasmids. So far, the region mediating autonomous replication has been identified and it was shown that the rep gene is required for replication. However, the regulation of rep expression remained elusive. Here evidence is presented that expression of the replication gene rep is auto-regulated. Sequence analysis revealed a conserved stretch in the rep promoter consisting of three imperfect direct repeats (DR2.1, DR2.2 and DR2.3). Assays for promoter activity showed that these direct repeats act as an enhancer of transcriptional activity. Interestingly, the activating effect was reduced in the presence of Rep protein. Electrophoretic mobility shift assays demonstrated that the Rep protein can directly bind to direct repeats DR2.1 and DR2.3 while DR2.2 is not bound but places DR2.1 and DR2.3 in an appropriate distance. These results show that the synthesis of Rep protein is auto-regulated. In the absence of Rep protein the promoter is, due to the presence of the direct repeats acting as a transcriptional enhancer, highly active. Binding of Rep to the direct repeats reduces the transcription rate significantly. Since this regulation mechanism is independent of a specialised regulator protein it is presumably a very economic strategy.


Assuntos
DNA Helicases/genética , Replicação do DNA , DNA Bacteriano/genética , Regulação Bacteriana da Expressão Gênica , Vetores Genéticos/metabolismo , Rahnella/genética , Transativadores/genética , Transcrição Genética , Sequência de Aminoácidos , Sítios de Ligação , Clonagem Molecular , DNA Helicases/metabolismo , DNA Bacteriano/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Escherichia coli/genética , Escherichia coli/metabolismo , Expressão Gênica , Vetores Genéticos/química , Regiões Promotoras Genéticas , Ligação Proteica , Rahnella/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Transativadores/metabolismo
14.
Carbohydr Polym ; 162: 10-15, 2017 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-28224885

RESUMO

R-ß-Gal is a cold-adapted ß-galactosidase that is able to hydrolyze lactose and has the potential to produce low-lactose or lactose-free dairy products at low temperatures (4°C). Cold-adapted enzymes unfold at moderate temperatures due to the lower intramolecular stabilizing interactions necessary for flexibility at low temperatures. To increase stability and usage-performance, R-ß-Gal was encapsulated in gellan gum by injecting an aqueous solution into two different hardening solutions (10mM CaCl2 or 10mM MgCl2). Enzyme characteristics of both free and encapsulated R-ß-Gal were carried out, and the different effects of two cations were investigated. R-ß-Gal showed better thermal and pH stability after encapsulation. Ca2+ gels had higher encapsulation efficiency (71.4%) than Mg2+ (66.7%) gels, and Ca2+ formed larger inner and surface pores. R-ß-Gal was released from the Ca2+ hydrogel beads more rapidly than the Mg2+ hydrogels during storage in aqueous solution due to the larger inner/surface pores of the matrix.


Assuntos
Microesferas , Polissacarídeos Bacterianos/química , Rahnella/enzimologia , beta-Galactosidase/metabolismo , Temperatura Baixa
15.
Mycorrhiza ; 27(1): 13-22, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27541158

RESUMO

Biofilm formation on abiotic and biotic surfaces was studied with two hyphobacteria, strongly attached to the surface of the arbuscular mycorrhizal fungus (AMF) Rhizoglomus irregulare (Ri) DAOM 197198 and two mycorrhizobacteria, loosely attached to the roots of different mycorrhizal plants. When the sparingly soluble igneous phosphate rock (PR) from Quebec, or when the chemical hydroxyapatite were used as sole phosphorus (P) source, hyphobacteria Rhizobium miluonense Rm3 and Burkholderia anthina Ba8 produced significantly more biofilms than mycorrhizobacteria Rahnella sp. Rs11 and Burkholderia phenazinium Bph12, as indicated by the crystal violet assay or by quantifying biofilm exopolysaccharides. As previously observed with planktonic bacteria, biofilms mobilized P by lowering the pH and releasing gluconic acid. The high efficiency of P mobilization by the hyphobacteria Ba8 was linked to the presence of more viable cells in its biofilm as revealed by the hydrolysis of fluorescein diacetate. Scanning electron microscopy micrographs showed a high adherence of the best P-solubilizer hyphobacteria Ba8 on the surface of Quebec PR. Hydroxyapatite porous structure did not allow a good adherence of Ba8. Ba8 formed an important biofilm on the hyphae of Ri DAOM 197198 with low reactive Quebec PR while no biofilm was observed with the high reactive hydroxyapatite. Results confirm the possible presence of specificity between the Ri DAOM 197198 and the hyphobacteria and suggest that the interaction would be regulated by the availability of P.


Assuntos
Biofilmes/crescimento & desenvolvimento , Burkholderia/fisiologia , Glomeromycota/fisiologia , Micorrizas/fisiologia , Rahnella/fisiologia , Rhizobium/fisiologia , Concentração de Íons de Hidrogênio
16.
Curr Microbiol ; 72(1): 64-7, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26424139

RESUMO

The paper presents first description of class 1 integron in an environmental strain of Rahnella aquatilis, a rarely isolated Gram-negative bacterium of the family Enterobacteriaceae. The strain was isolated from the Warta river water, Poland. Class 1 integrase gene was detected by a PCR assay. Sequencing of the integron's variable region showed the presence of a dfrA1-aadA1 gene cassette array. The integron was located in a 54-kbp plasmid that was transferable to Escherichia coli J-53 recipient strain in a conjugation assay. The integron-bearing R. aquatilis strain was resistant to aminoglycosides, penicillins, trimethoprim, sulfamethoxazole, and trimethoprim/sulfamethoxazole. This paper confirms that water environment play a major role in the spread of integrons and, consequently, antimicrobial resistance, among bacteria of various genera.


Assuntos
Integrons , Rahnella/genética , Rahnella/isolamento & purificação , Rios/microbiologia , Antibacterianos/farmacologia , Conjugação Genética , DNA Bacteriano/genética , Farmacorresistência Bacteriana , Escherichia coli/genética , Transferência Genética Horizontal , Plasmídeos/análise , Polônia , Reação em Cadeia da Polimerase , Rahnella/efeitos dos fármacos
17.
Braz J Infect Dis ; 19(6): 648-50, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26410540

RESUMO

Rahnella aquatilis is an environmental Gram-negative bacillus that is rarely reported as human pathogen, being mainly associated with infections in immunocompromised patients. Herein we describe two cases of R. aquatilis isolates recovered from endotracheal aspirate cultures of different patients in a tertiary hospital located in the city of São Paulo, Brazil. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 16S rDNA gene sequencing were performed to confirm bacterial identification after the isolates being erroneously identified as Pantoea spp. by automated system. Both isolates showed the same PFGE pattern and presented the ß-lactamase encoding gene blaRAHN-1, responsible for resistance to cephalothin. The isolates were susceptible to broad-spectrum cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and polymyxin B. This report shows the presence and transmission of uncommon bacteria in the nosocomial environment and alerts us about the need for new tools of correct microbiologic diagnosis.


Assuntos
Infecção Hospitalar/microbiologia , Infecções por Bactérias Gram-Positivas/microbiologia , Rahnella/isolamento & purificação , Adulto , Antibacterianos/farmacologia , Infecção Hospitalar/transmissão , Infecções por Bactérias Gram-Positivas/transmissão , Humanos , Masculino , Testes de Sensibilidade Microbiana , Pessoa de Meia-Idade , Rahnella/efeitos dos fármacos
18.
Toxicon ; 104: 46-51, 2015 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-26238172

RESUMO

Toxic goby fish (Yongeichthys criniger) containing tetrodotoxin (TTX), from Zhanjiang, Guangdong province, China, were screened for TTX-producing bacteria. Two toxic bacterial strains were isolated from the liver of Y. criniger and respectively denoted XC3-3 and XL-1. TTX production by the strains was confirmed by mouse bioassay, enzyme-linked immunosorbent assay and high performance liquid chromatography coupled with mass spectrometry. Based on morphological, physiological and biochemical characteristics and 16S rDNA phylogenetic analysis, strain XC3-3 was identified as Enterobacter cloaca and XL-1 was closely related to Rahnella aquatilis. These findings show for the first time that TTX-producing bacteria are symbiotic bacteria in goby and suggest that bacterial strains are at least partially responsible for TTX accumulation in Y. criniger.


Assuntos
Enterobacter cloacae/isolamento & purificação , Peixes/microbiologia , Tetrodotoxina/biossíntese , Animais , China , Cromatografia Líquida de Alta Pressão , Ensaio de Imunoadsorção Enzimática , Fígado/microbiologia , Camundongos , Filogenia , Rahnella/isolamento & purificação , Simbiose
19.
Protein Expr Purif ; 115: 158-64, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26145832

RESUMO

A novel gene was isolated for the first time from a psychrophilic gram-negative bacterium Rahnella sp. R3. The gene encoded a cold-adapted ß-galactosidase (R-ß-Gal). Recombinant R-ß-Gal was expressed in Escherichia coli BL21 (DE3), purified and characterized. R-ß-gal belongs to the glycosyl hydrolase family 42. Circular dichroism spectrometry of the structural stability of R-ß-Gal with respect to temperature indicated that the secondary structures of the enzyme were stable to 45°C. In solution, the enzyme was a homo-trimer and was active at temperatures as low as 4°C. The enzyme did not require the presence of metal ions to be active, but Mg(2+), Mn(2+), and Ca(2+) enhanced its activity slightly, whereas Fe(3+), Zn(2+) and Al(3+) appeared to inactive it. The purified enzyme displayed K(m) values of 6.5 mM for ONPG and 2.2mM for lactose at 4°C. These values were lower than the corresponding K(m)s reported for other cold-adapted ß-Gals.


Assuntos
Rahnella/enzimologia , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , beta-Galactosidase/química , beta-Galactosidase/metabolismo , Clonagem Molecular , Temperatura Baixa , Estabilidade Enzimática , Escherichia coli/genética , Concentração de Íons de Hidrogênio , Cinética , Metais Pesados , Rahnella/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificação , beta-Galactosidase/genética , beta-Galactosidase/isolamento & purificação
20.
Microbiol Res ; 176: 38-47, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26070691

RESUMO

The changes in cell surface properties of Rahnella sp. strain EK12 and modifications in genetic material after long-term contact with saponins and rhamnolipids, were investigated. Rhamnolipids caused a decrease of hydrophobicity in liquid cultures compared with saponins. On the other hand, in cultures with rhamnolipids, the addition of diesel oil results in a rapid rise of cell surface hydrophobicity. The similar effect was not so significant in the presence of saponins. For the bacteria grown in the presence of saponins or rhamnolipids, but without diesel oil, the ratio of unsaturated to saturated fatty acids decreased, in comparison to the control culture. The differences observed in hydrophobicity, zeta potential and fatty acids profiles, indicated various mechanisms of an interaction between a surfactant and a bacterial cells. The results have also shown an impact of the long-term contact on changes in genetic material of Rahnella sp. strain EK12 cells. Moreover, the presence of saponins led to significant increase of diesel oil biodegradation.


Assuntos
Parede Celular/química , Gasolina , Óleos/metabolismo , Rahnella/isolamento & purificação , Rahnella/metabolismo , Propriedades de Superfície , Biotransformação , Membrana Celular/química , Ácidos Graxos/análise , Glicolipídeos/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Rahnella/crescimento & desenvolvimento , Saponinas/metabolismo , Tensoativos/metabolismo
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