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1.
Proc Natl Acad Sci U S A ; 118(4)2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33483419

RESUMO

Toxin-antitoxin (TA) loci were initially identified on conjugative plasmids, and one function of plasmid-encoded TA systems is to stabilize plasmids or increase plasmid competition via postsegregational killing. Here, we discovered that the type II TA system, Pseudoalteromonas rubra plasmid toxin-antitoxin PrpT/PrpA, on a low-copy-number conjugative plasmid, directly controls plasmid replication. Toxin PrpT resembles ParE of plasmid RK2 while antitoxin PrpA (PF03693) shares no similarity with previously characterized antitoxins. Surprisingly, deleting this prpA-prpT operon from the plasmid does not result in plasmid segregational loss, but greatly increases plasmid copy number. Mechanistically, the antitoxin PrpA functions as a negative regulator of plasmid replication, by binding to the iterons in the plasmid origin that inhibits the binding of the replication initiator to the iterons. We also demonstrated that PrpA is produced at a higher level than PrpT to prevent the plasmid from overreplicating, while partial or complete degradation of labile PrpA derepresses plasmid replication. Importantly, the PrpT/PrpA TA system is conserved and is widespread on many conjugative plasmids. Altogether, we discovered a function of a plasmid-encoded TA system that provides new insights into the physiological significance of TA systems.

2.
Nucleic Acids Res ; 48(19): 11054-11067, 2020 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-33045733

RESUMO

The two-gene module HEPN/MNT is predicted to be the most abundant toxin/antitoxin (TA) system in prokaryotes. However, its physiological function and neutralization mechanism remains obscure. Here, we discovered that the MntA antitoxin (MNT-domain protein) acts as an adenylyltransferase and chemically modifies the HepT toxin (HEPN-domain protein) to block its toxicity as an RNase. Biochemical and structural studies revealed that MntA mediates the transfer of three AMPs to a tyrosine residue next to the RNase domain of HepT in Shewanella oneidensis. Furthermore, in vitro enzymatic assays showed that the three AMPs are transferred to HepT by MntA consecutively with ATP serving as the substrate, and this polyadenylylation is crucial for reducing HepT toxicity. Additionally, the GSX10DXD motif, which is conserved among MntA proteins, is the key active motif for polyadenylylating and neutralizing HepT. Thus, HepT/MntA represents a new type of TA system, and the polyadenylylation-dependent TA neutralization mechanism is prevalent in bacteria and archaea.


Assuntos
Proteínas de Bactérias/metabolismo , Toxinas Bacterianas/metabolismo , Shewanella/metabolismo , Sistemas Toxina-Antitoxina
3.
Microb Biotechnol ; 13(4): 1132-1144, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32246813

RESUMO

Pf prophages are ssDNA filamentous prophages that are prevalent among various Pseudomonas aeruginosa strains. The genomes of Pf prophages contain not only core genes encoding functions involved in phage replication, structure and assembly but also accessory genes. By studying the accessory genes in the Pf4 prophage in P. aeruginosa PAO1, we provided experimental evidence to demonstrate that PA0729 and the upstream ORF Rorf0727 near the right attachment site of Pf4 form a type II toxin/antitoxin (TA) pair. Importantly, we found that the deletion of the toxin gene PA0729 greatly increased Pf4 phage production. We thus suggest the toxin PA0729 be named PfiT for Pf4 inhibition toxin and Rorf0727 be named PfiA for PfiT antitoxin. The PfiT toxin directly binds to PfiA and functions as a corepressor of PfiA for the TA operon. The PfiAT complex exhibited autoregulation by binding to a palindrome (5'-AATTCN5 GTTAA-3') overlapping the -35 region of the TA operon. The deletion of pfiT disrupted TA autoregulation and activated pfiA expression. Additionally, the deletion of pfiT also activated the expression of the replication initiation factor gene PA0727. Moreover, the Pf4 phage released from the pfiT deletion mutant overcame the immunity provided by the phage repressor Pf4r. Therefore, this study reveals that the TA systems in Pf prophages can regulate phage production and phage immunity, providing new insights into the function of TAs in mobile genetic elements.

4.
Environ Microbiol ; 21(11): 4212-4232, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31418995

RESUMO

Almost all bacterial genomes harbour prophages, yet it remains unknown why prophages integrate into tRNA-related genes. Approximately 1/3 of Shewanella isolates harbour a prophage at the tmRNA (ssrA) gene. Here, we discovered a P2-family prophage integrated at the 3'-end of ssrA in the deep-sea bacterium S. putrefaciens. We found that ~0.1% of host cells are lysed to release P2 constitutively during host growth. P2 phage production is induced by a prophage-encoded Rep protein and its excision is induced by the Cox protein. We also found that P2 genome excision leads to the disruption of wobble base pairing of SsrA due to site-specific recombination, thus disrupting the trans-translation function of SsrA. We further demonstrated that P2 excision greatly hinders growth in seawater medium and inhibits biofilm formation. Complementation with a functional SsrA in the P2-excised strain completely restores the growth defects in seawater medium and partially restores biofilm formation. Additionally, we found that products of the P2 genes also increase biofilm formation. Taken together, this study illustrates a symbiotic relationship between P2 and its marine host, thus providing multiple benefits for both sides when a phage is integrated but suffers from reduced fitness when the prophage is excised.


Assuntos
Bacteriófago P2/fisiologia , Shewanella putrefaciens/virologia , Simbiose/genética , Organismos Aquáticos/genética , Genoma Bacteriano/genética , Prófagos/genética , RNA Bacteriano/genética , Shewanella putrefaciens/genética
5.
Sensors (Basel) ; 19(11)2019 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-31167351

RESUMO

In industrial production processes, rotational speed is a key parameter for equipment condition monitoring and fault diagnosis. To achieve rotational speed measurement of rotational equipment under a condition of high temperature and heavy dust, this article proposes a digital approach using an electrostatic sensor. The proposed method utilizes a strip of a predetermined material stuck on the rotational shaft which will accumulate a charge because of the relative motion with the air. Then an electrostatic sensor mounted near the strip is employed to obtain the fluctuating signal related to the rotation of the charged strip. Via a signal conversion circuit, a square wave, the frequency of which equals that of the rotation shaft can be obtained. Having the square wave, the M/T method and T method are adopted to work out the rotational speed. Experiments were conducted on a laboratory-scale test rig to compare the proposed method with the auto-correlation method. The largest relative errors of the auto-correlation method with the sampling rate of 2 ksps, 5 ksps are 3.2% and 1.3%, respectively. The relative errors using digital approaches are both within ±4‰. The linearity of the digital approach combined with the M/T method or T method is also superior to that of the auto-correlation method. The performance of the standard deviations and response speed was also compared and analyzed to show the priority of the digital approach.

6.
FEMS Microbiol Ecol ; 95(6)2019 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-31077283

RESUMO

Bacterial capsular polysaccharides (CPSs) participate in environmental adaptation in diverse bacteria species. However, the role and regulation of CPS production in marine bacteria have remained largely unexplored. We previously reported that both wrinkled and translucent Pseudoalteromonas lipolytica variants with altered polysaccharide production were generated in pellicle biofilm-associated cells. In this study, we observed that translucent variants were generated at a rate of ∼20% in colony biofilms of P. lipolytica cultured on HSLB agar plates for 12 days. The DNA sequencing results revealed that nearly 90% of these variants had an IS5-like element inserted within the coding or promoter regions of nine genes in the cps operon. In contrast, IS5 insertion into the cps operon was not detected in planktonic cells. Furthermore, we demonstrated that the IS5 insertion event inactivated CPS production, which leads to a translucent colony morphology. The CPS-deficient variants showed an increased ability to form attached biofilms but exhibited reduced resistance to sublethal concentrations of antibiotics. Moreover, deleting the DNA repair gene recA significantly decreased the frequency of occurrence of CPS-deficient variants during biofilm formation. Thus, IS insertion into the cps operon is an important mechanism for the production of genetic variants during biofilm formation of marine bacteria.


Assuntos
Biofilmes , Elementos de DNA Transponíveis , DNA Bacteriano , Polissacarídeos Bacterianos/metabolismo , Pseudoalteromonas/crescimento & desenvolvimento , Óperon , Polissacarídeos Bacterianos/genética , Pseudoalteromonas/genética , Pseudoalteromonas/metabolismo
7.
Mar Drugs ; 17(4)2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30987346

RESUMO

Toxin-antitoxin (TA) systems are ubiquitous and abundant genetic elements in bacteria and archaea. Most previous TA studies have focused on commensal and pathogenic bacteria, but have rarely focused on marine bacteria, especially those isolated from the deep sea. Here, we identified and characterized three putative TA pairs in the deep-sea-derived Streptomyces sp. strain SCSIO 02999. Our results showed that Orf5461/Orf5462 and Orf2769/Orf2770 are bona fide TA pairs. We provide several lines of evidence to demonstrate that Orf5461 and Orf5462 constitute a type-II TA pair that are homologous to the YoeB/YefM TA pair from Escherichia coli. Although YoeB from SCSIO 02999 was toxic to an E. coli host, the homologous YefM antitoxin from SCSIO 02999 did not neutralize the toxic effect of YoeB from E. coli. For the Orf2769/Orf2770 TA pair, Orf2769 overexpression caused significant cell elongation and could lead to cell death in E. coli, and the neighboring Orf2770 could neutralize the toxic effect of Orf2769. However, no homologous toxin or antitoxin was found for this pair, and no direct interaction was found between Orf2769 and Orf2770. These results suggest that Orf2769 and Orf2770 may constitute a novel TA pair. Thus, deep-sea bacteria harbor typical and novel TA pairs. The biochemical and physiological functions of different TAs in deep-sea bacteria warrant further investigation.


Assuntos
Organismos Aquáticos/fisiologia , Proteínas de Bactérias/genética , Streptomyces/fisiologia , Sistemas Toxina-Antitoxina/genética , Proteínas de Bactérias/isolamento & purificação , Toxinas Bacterianas , Escherichia coli/fisiologia , Proteínas de Escherichia coli/fisiologia , Loci Gênicos/fisiologia , Sedimentos Geológicos/microbiologia , Interações Microbianas/fisiologia , Oceanos e Mares , Homologia de Sequência do Ácido Nucleico
8.
Environ Microbiol ; 21(8): 2707-2723, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30882983

RESUMO

Toxin/antitoxin (TA) systems are ubiquitous in bacteria and archaea and participate in biofilm formation and stress responses. The higBA locus of the opportunistic pathogen Pseudomonas aeruginosa encodes a type II TA system. Previous work found that the higBA operon is cotranscribed and that HigB toxin regulates biofilm formation and virulence expression. In this study, we demonstrate that HigA antitoxin is produced at a higher level than HigB and that higA mRNA is expressed separately from a promoter inside higB during the late stationary phase. Critically, HigA represses the expression of mvfR, which is an important virulence-related regulator, by binding to a conserved HigA palindrome (5'-TTAAC GTTAA-3') in the mvfR promoter, and the binding of HigB to HigA derepresses this process. During the late stationary phase, excess HigA represses the expression of mvfR and higBA. However, in the presence of aminoglycoside antibiotics where Lon protease is activated, the degradation of HigA by Lon increases P. aeruginosa virulence by simultaneously derepressing mvfR and higB transcription. Therefore, this study reveals that the antitoxin of the P. aeruginosa TA system is integrated into the key virulence regulatory network of the host and functions as a transcriptional repressor to control the production of virulence factors.


Assuntos
Proteínas de Bactérias/genética , Pseudomonas aeruginosa/genética , Sistemas Toxina-Antitoxina , Proteínas de Bactérias/metabolismo , Expressão Gênica , Regulação Bacteriana da Expressão Gênica , Óperon , Regiões Promotoras Genéticas , Pseudomonas aeruginosa/metabolismo , Pseudomonas aeruginosa/patogenicidade , Sistemas Toxina-Antitoxina/genética , Virulência/genética , Fatores de Virulência
9.
Mol Microbiol ; 111(2): 495-513, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30475408

RESUMO

Pf filamentous prophages are prevalent among clinical and environmental Pseudomonas aeruginosa isolates. Pf4 and Pf5 prophages are integrated into the host genomes of PAO1 and PA14, respectively, and play an important role in biofilm development. However, the genetic factors that directly control the lysis-lysogeny switch in Pf prophages remain unclear. Here, we identified and characterized the excisionase genes in Pf4 and Pf5 (named xisF4 and xisF5, respectively). XisF4 and XisF5 represent two major subfamilies of functional excisionases and are commonly found in Pf prophages. While both of them can significantly promote prophage excision, only XisF5 is essential for Pf5 excision. XisF4 activates Pf4 phage replication by upregulating the phage initiator gene (PA0727). In addition, xisF4 and the neighboring phage repressor c gene pf4r are transcribed divergently and their 5'-untranslated regions overlap. XisF4 and Pf4r not only auto-activate their own expression but also repress each other. Furthermore, two H-NS family proteins, MvaT and MvaU, coordinately repress Pf4 production by directly repressing xisF4. Collectively, we reveal that Pf prophage excisionases cooperate in controlling lysogeny and phage production.


Assuntos
DNA Nucleotidiltransferases/metabolismo , Lisogenia , Prófagos/enzimologia , Prófagos/crescimento & desenvolvimento , Fagos de Pseudomonas/enzimologia , Pseudomonas aeruginosa/virologia , Proteínas Virais/metabolismo , Replicação Viral , Regulação Viral da Expressão Gênica , Prófagos/genética , Fagos de Pseudomonas/genética , Fagos de Pseudomonas/crescimento & desenvolvimento
10.
Rev Sci Instrum ; 89(5): 055106, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29864826

RESUMO

In this paper, the electrical method combines the electrostatic sensor and capacitance sensor to measure the phase concentration of pulverized coal/biomass/air three-phase flow through data fusion technology. In order to eliminate the effects of flow regimes and improve the accuracy of the phase concentration measurement, the mel frequency cepstrum coefficient features extracted from electrostatic signals are used to train the Continuous Gaussian Mixture Hidden Markov Model (CGHMM) for flow regime identification. Support Vector Machine (SVM) is introduced to establish the concentration information fusion model under identified flow regimes. The CGHMM models and SVM models are transplanted on digital signal processing (DSP) to realize on-line accurate measurement. The DSP flow regime identification time is 1.4 ms, and the concentration predict time is 164 µs, which can fully meet the real-time requirement. The average absolute value of the relative error of the pulverized coal is about 1.5% and that of the biomass is about 2.2%.

11.
Environ Microbiol ; 20(3): 1224-1239, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29411516

RESUMO

Toxin/antitoxin (TA) loci are commonly found in mobile genetic elements such as plasmids and prophages. However, the physiological functions of these TA loci in prophages and cross-regulation among these TA loci remain largely unexplored. Here, we characterized a newly discovered type II TA pair, ParESO /CopASO , in the CP4So prophage in Shewanella oneidensis. We demonstrated that ParESO /CopASO plays a critical role in the maintenance of CP4So in host cells after its excision. The toxin ParESO inhibited cell growth, resulting in filamentous growth and eventually cell death. The antitoxin CopASO neutralized the toxicity of ParESO through direct protein-protein interactions and repressed transcription of the TA operon by binding to a DNA motif in the promoter region containing two inverted repeats [5'-GTANTAC (N)3 GTANTAC-3']. CopASO also repressed transcription of another TA system PemKSO /PemISO in megaplasmid pMR-1 of S. oneidensis through binding to a highly similar DNA motif in its promoter region. CopASO homologs are widely spread in Shewanella and other Proteobacteria, either as a component of a TA pair or as orphan antitoxins. Our study thus illustrated the cross-regulation of the TA systems in different mobile genetic elements and expanded our understanding of the physiological function of TA systems.


Assuntos
Antitoxinas/genética , Toxinas Bacterianas/genética , Sequências Repetitivas Dispersas/genética , Prófagos/genética , Shewanella/genética , Sistemas Toxina-Antitoxina/genética , Proteínas de Bactérias/metabolismo , Sequências Repetidas Invertidas/genética , Óperon/genética , Plasmídeos/genética , Regiões Promotoras Genéticas/genética , Shewanella/fisiologia
12.
Front Microbiol ; 9: 3304, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30687283

RESUMO

Quorum sensing (QS) promotes in situ extracellular enzyme (EE) activity via the exogenous signal N-acylhomoserine lactone (AHL), which facilitates marine particle degradation, but the species that engage in this regulatory mechanism remain unclear. Here, we obtained AHL-producing and AHL-degrading strains from marine particles. The strain Ruegeria mobilis Rm01 of the Roseobacter group (RBG), which was capable of both AHL producing and degrading, was chosen to represent these strains. We demonstrated that Rm01 possessed a complex QS network comprising AHL-based QS and quorum quenching (QQ) systems and autoinducer-2 (AI-2) perception system. Rm01 was able to respond to multiple exogenous QS signals through the QS network. By applying self-generated AHLs and non-self-generated AHLs and AI-2 QS signal molecules, we modulated biofilm formation and lipase production in Rm01, which reflected the coordination of bacterial metabolism with that of other species via eavesdropping on exogenous QS signals. These results suggest that R. mobilis might be one of the participators that could regulate EE activities by responding to QS signals in marine particles.

13.
Methods Mol Biol ; 1673: 297-309, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29130182

RESUMO

Although it has been more than a decade since the first discovery of AHL lactonase AiiA in Bacillus sp. 240B1, we are only beginning to understand the diversity of quorum quenching (QQ) enzymes. Most of the previously identified QQ enzymes are derived from nonmarine microorganisms. A novel marine-derived secretory AHL lactonase, MomL, was found in Muricauda olearia in our previous work and represents a novel type of AHL lactonase widespread in the ocean. Herein, we describe a culture-dependent method for the identification of microbial QQ enzymes, especially the high-throughput method for screening QQ bacteria from cultivable bacterial strains. This method should be capable of efficiently identifying QQ enzymes from various microbial origins. The discovery of more QQ enzymes will help us to understand their ecological roles and may provide potential as therapeutic agents.


Assuntos
Bactérias/enzimologia , Técnicas de Cultura de Células/métodos , Percepção de Quorum , Ensaios de Triagem em Larga Escala , beta-Galactosidase/metabolismo
14.
Sensors (Basel) ; 17(12)2017 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-29232850

RESUMO

Electrical capacitance tomography (ECT) is a promising imaging technology of permittivity distributions in multiphase flow. To reduce the effect of charging phenomenon on ECT measurement, an improved extreme learning machine method combined with adaptive soft-thresholding (AST-ELM) is presented and studied for image reconstruction. This method can provide a nonlinear mapping model between the capacitance values and medium distributions by using machine learning but not an electromagnetic-sensitive mechanism. Both simulation and experimental tests are carried out to validate the performance of the presented method, and reconstructed images are evaluated by relative error and correlation coefficient. The results have illustrated that the image reconstruction accuracy by the proposed AST-ELM method has greatly improved than that by the conventional methods under the condition with charging object.

15.
Front Microbiol ; 8: 840, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28536573

RESUMO

Bacterial toxin/antitoxin (TA) systems have received increasing attention due to their prevalence, diverse structures, and important physiological functions. In this study, we identified and characterized a type II TA system in a soil bacterium Pseudomonas putida KT2440. This TA system belongs to the MqsR/MqsA family. We found that PP_4205 (MqsR) greatly inhibits cell growth in P. putida KT2440 and Escherichia coli, the antitoxin PP_4204 (MqsA) neutralizes the toxicity of the toxin MqsR, and the two genes encoding them are co-transcribed. MqsR and MqsA interact with each other directly in vivo and MqsA is a negative regulator of the TA operon through binding to the promoter. Consistent with the MqsR/MqsA pair in E. coli, the binding of the toxin MqsR to MqsA inhibits the DNA binding ability of MqsA in P. putida KT2440. Disruption of the mqsA gene which induces mqsR expression increases persister cell formation 53-fold, while overexpressing mqsA which represses mqsR expression reduces persister cell formation 220-fold, suggesting an important role of MqsR in persistence in P. putida KT2440. Furthermore, both MqsR and MqsA promote biofilm formation. As a DNA binding protein, MqsA can also negatively regulate an ECF sigma factor AlgU and a universal stress protein PP_3288. Thus, we revealed an important regulatory role of MqsR/MqsA in persistence and biofilm formation in P. putida KT2440.

16.
FEMS Microbiol Ecol ; 91(2): 1-13, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25764555

RESUMO

Marine snow is a continuous shower of organic and inorganic detritus, and plays a crucial role in transporting materials from the sea surface to the deep ocean. The aims of the current study were to identify N-acyl homoserine lactone (AHL)-based quorum sensing (QS) signaling molecules directly from marine snow particles and to investigate the possible regulatory link between QS signals and extracellular hydrolytic enzymes produced by marine snow bacteria. The marine snow samples were collected from the surface water of China marginal seas. Two AHLs, i.e. 3OC6-HSL and C8-HSL, were identified directly from marine snow particles, while six different AHL signals, i.e. C4-HSL, 3OC6-HSL, C6-HSL, C10-HSL, C12-HSL and C14-HSL were produced by Pantoea ananatis B9 inhabiting natural marine snow particles. Of the extracellular hydrolytic enzymes produced by P. ananatis B9, alkaline phosphatase activity was highly enhanced in growth medium supplemented with exogenous AHL (C10-HSL), while quorum quenching enzyme (AiiA) drastically reduced the enzyme activity. To our knowledge, this is the first report revealing six different AHL signals produced by P. ananatis B9 and AHL-based QS system enhanced the extracellular hydrolytic enzyme in P. ananatis B9. Furthermore, this study first time revealing 3OC6-HSL production by Paracoccus carotinifaciens affiliated with Alphaproteobacteria.


Assuntos
Acil-Butirolactonas/metabolismo , Pantoea/metabolismo , Percepção de Quorum , Neve/microbiologia , Fosfatase Alcalina/metabolismo , China , Oceanos e Mares , Pantoea/enzimologia , Pantoea/genética , Microbiologia da Água
17.
BMC Genomics ; 16: 38, 2015 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-25652846

RESUMO

BACKGROUND: Intestinal microbes play significant roles in fish and can be possibly used as probiotics in aquaculture. In our previous study, Flaviramulus ichthyoenteri Th78(T), a novel species in the family Flavobacteriaceae, was isolated from fish intestine and showed strong quorum quenching (QQ) ability. To identify the QQ enzymes in Th78(T) and explore the potential roles of Th78(T) in fish intestine, we sequenced the genome of Th78(T) and performed extensive genomic analysis. RESULTS: An N-acyl homoserine lactonase FiaL belonging to the metallo-ß-lactamase superfamily was identified and the QQ activity of heterologously expressed FiaL was confirmed in vitro. FiaL has relatively little similarity to the known lactonases (25.2 ~ 27.9% identity in amino acid sequence). Various digestive enzymes including alginate lyases and lipases can be produced by Th78(T), and enzymes essential for production of B vitamins such as biotin, riboflavin and folate are predicted. Genes encoding sialic acid lyases, sialidases, sulfatases and fucosidases, which contribute to utilization of mucus, are present in the genome. In addition, genes related to response to different stresses and gliding motility were also identified. Comparative genome analysis shows that Th78(T) has more specific genes involved in carbohydrate transport and metabolism compared to other two isolates in Flavobacteriaceae, both isolated from sediments. CONCLUSIONS: The genome of Th78(T) exhibits evident advantages for this bacterium to survive in the fish intestine, including production of QQ enzyme, utilization of various nutrients available in the intestine as well as the ability to produce digestive enzymes and vitamins, which also provides an application prospect of Th78(T) to be used as a probiotic in aquaculture.


Assuntos
Peixes/microbiologia , Flavobacteriaceae/genética , Percepção de Quorum , Análise de Sequência de DNA , Sequência de Aminoácidos , Animais , Hidrolases de Éster Carboxílico/genética , Intestinos/microbiologia , beta-Lactamases/genética
18.
Int J Syst Evol Microbiol ; 65(Pt 4): 1347-1353, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25667395

RESUMO

A Gram-stain-negative, orange-coloured, rod-shaped bacterium, designated strain Th68(T), was isolated from the intestine of flounder (Paralichthys olivaceus). The isolate required sea salts for growth. Gliding motility was not observed. Flexirubin-type pigments were present. 16S rRNA gene sequence analysis indicated that strain Th68(T) represented a distinct phyletic line within the family Flavobacteriaceae with less than 96.1% similarity to members of the recognized genera of the family. The DNA G+C content was 33.0 mol%. The major fatty acids were iso-C(15 : 0), iso-C(15 : 1) G, iso-C(17 : 0) 3-OH and iso-C(15 : 0) 3-OH. The major polar lipids were phosphatidylethanolamine, two unidentified aminolipids and two unidentified polar lipids. Menaquinone 6 (MK-6) was the only respiratory quinone. On the basis of the phenotypic, chemotaxonomic and phylogenetic data, strain Th68(T) represents a novel species of a new genus in the family Flavobacteriaceae , for which the name Flavirhabdus iliipiscaria gen. nov., sp. nov. is proposed. The type strain of Flavirhabdus iliipiscaria is Th68(T) ( = JCM 18637(T) = KCTC 32141(T)).


Assuntos
Flavobacteriaceae/classificação , Linguado/microbiologia , Intestinos/microbiologia , Filogenia , Animais , Técnicas de Tipagem Bacteriana , Composição de Bases , China , DNA Bacteriano/genética , Ácidos Graxos/química , Flavobacteriaceae/genética , Flavobacteriaceae/isolamento & purificação , Dados de Sequência Molecular , Fosfatidiletanolaminas/química , Pigmentação , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Vitamina K 2/análogos & derivados , Vitamina K 2/química
19.
Int J Syst Evol Microbiol ; 65(Pt 4): 1186-1192, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25604342

RESUMO

A novel marine bacterium isolated from the intestine of cultured flounder (Paralichthys olivaceus) was studied by using a polyphasic taxonomic approach. The isolate was Gram-stain-negative, pleomorphic, aerobic, yellow and oxidase- and catalase-negative. Phylogenetic analysis of 16S rRNA gene sequences indicated that isolate Th6(T) formed a distinct branch within the family Flavobacteriaceae and showed 96.6% similarity to its closest relative, Bizionia hallyeonensis T-y7(T). The DNA G+C content was 29 mol%. The major respiratory quinone was MK-6. The predominant fatty acids were iso-C(15 : 1) G, iso-C(15 : 0), iso-C(15 : 0) 3-OH, iso-C(17 : 0) 3-OH and summed feature 3 (C(15 : 1)ω6c and/or C(16 : 1)ω7c). On the basis of the phenotypic, chemotaxonomic and phylogenetic characteristics, the novel bacterium has been assigned to a novel species of a new genus for which the name Ichthyenterobacterium magnum gen. nov., sp. nov. is proposed. The type strain is Th6(T) ( = JCM 18636(T) = KCTC 32140(T)).


Assuntos
Flavobacteriaceae/classificação , Linguado/microbiologia , Filogenia , Animais , Técnicas de Tipagem Bacteriana , Composição de Bases , China , DNA Bacteriano/genética , Ácidos Graxos/química , Flavobacteriaceae/genética , Flavobacteriaceae/isolamento & purificação , Intestinos/microbiologia , Dados de Sequência Molecular , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Vitamina K 2/análogos & derivados , Vitamina K 2/química
20.
Appl Environ Microbiol ; 81(2): 774-82, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25398866

RESUMO

Gram-negative bacteria use N-acyl homoserine lactones (AHLs) as quorum sensing (QS) signaling molecules for interspecies communication, and AHL-dependent QS is related with virulence factor production in many bacterial pathogens. Quorum quenching, the enzymatic degradation of the signaling molecule, would attenuate virulence rather than kill the pathogens, and thereby reduce the potential for evolution of drug resistance. In a previous study, we showed that Muricauda olearia Th120, belonging to the class Flavobacteriia, has strong AHL degradative activity. In this study, an AHL lactonase (designated MomL), which could degrade both short- and long-chain AHLs with or without a substitution of oxo-group at the C-3 position, was identified from Th120. Liquid chromatography-mass spectrometry analysis demonstrated that MomL functions as an AHL lactonase catalyzing AHL degradation through lactone hydrolysis. MomL is an AHL lactonase belonging to the metallo-ß-lactamase superfamily that harbors an N-terminal signal peptide. The overall catalytic efficiency of MomL for C6-HSL is ∼2.9 × 10(5) s(-1) M(-1). Metal analysis and site-directed mutagenesis showed that, compared to AiiA, MomL has a different metal-binding capability and requires the histidine and aspartic acid residues for activity, while it shares the "HXHXDH" motif with other AHL lactonases belonging to the metallo-ß-lactamase superfamily. This suggests that MomL is a representative of a novel type of secretory AHL lactonase. Furthermore, MomL significantly attenuated the virulence of Pseudomonas aeruginosa in a Caenorhabditis elegans infection model, which suggests that MomL has the potential to be used as a therapeutic agent.


Assuntos
Acil-Butirolactonas/metabolismo , Hidrolases de Éster Carboxílico/isolamento & purificação , Hidrolases de Éster Carboxílico/metabolismo , Flavobacteriaceae/enzimologia , Flavobacteriaceae/genética , Animais , Caenorhabditis elegans/microbiologia , Hidrolases de Éster Carboxílico/genética , Domínio Catalítico , Cromatografia Líquida , Análise Mutacional de DNA , DNA Bacteriano/química , DNA Bacteriano/genética , Modelos Animais de Doenças , Cinética , Espectrometria de Massas , Metais/metabolismo , Militares , Dados de Sequência Molecular , Ligação Proteica , Sinais Direcionadores de Proteínas , Pseudomonas aeruginosa/patogenicidade , Pseudomonas aeruginosa/fisiologia , Percepção de Quorum , Análise de Sequência de DNA , Virulência
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