ABSTRACT
Artificial reefs represent useful tools to revitalize coastal and ocean ecosystems. Their formulation determines the biofilm formation which is the prerequisite for the colonization process by marine micro- and macroorganisms. In comparison with concrete, biobased polymers offer improved characteristics, including architecture, formulation, rugosity and recycling. This article aims to explore a new scale of artificial reef made of biocomposites reinforced with a high flax fibre (Linum utilatissimum) content (30%). Cellular adhesion and resulting biofilm formation were assessed using two marine microorganisms: Pseudoalteromonas sp. 3J6 and Cylindrotheca closterium. The influence of flax fibre leachates and plastic monomers on the growth of those marine microorganisms were also evaluated. Results indicated that the introduction of flax fibres inside the polymer matrix modified its physicochemical properties thus modulating adhesion and biofilm formation depending on the microorganism. This study gives insights for further developments of novel functionalized artificial reefs made of biocomposites.
Subject(s)
Biofilms , Flax , Pseudoalteromonas , Biofilms/growth & development , Flax/microbiology , Flax/chemistry , Pseudoalteromonas/physiology , Bacterial AdhesionABSTRACT
Gram-negative bacteria usually use acyl-homoserine lactones (AHLs)-mediated LuxI/LuxR-type quorum sensing (QS) systems for cell-cell cooperation and/or bacteria-environment communication. LuxI and LuxR are AHLs synthase and receptor, respectively. These two parts could form a positive regulatory feedback loop, controlling various types of group behaviors. However, the autoregulation mechanisms between them are fragmented and could be highly differentiated in different bacteria. Here, we clarified the autoregulation mechanism between LuxI and LuxR in Pseudoalteromonas sp. R3. YasI (LuxI in strain R3) synthesizes two types of AHLs, C8-HSL and 3-OH-C8-HSL. It is worth noting that YasR (LuxR in strain R3) only responds to C8-HSL rather than 3-OH-C8-HSL. YasR-C8HSL can activate the yasI transcription by recognizing "lux box" at yasI upstream. Interestingly, YasR can directly promote the yasR expression with AHL-independent manner, but AHL absence caused by the yasI-deficiency led to the significant decrease in the yasR expression. Further study demonstrated that the yasI-deficiency can result in the decrease in the yasR mRNA stability. Notably, both yasI-deficiency and yasR-deficiency led to the significant decrease in the expression of hfq encoding RNA chaperone. Therefore, it was speculated that not only YasR itself can directly regulate the yasR transcription, but YasR-C8HSL complex indirectly affects the yasR mRNA stability by regulating Hfq.
Subject(s)
Bacterial Proteins/metabolism , Homeostasis , Pseudoalteromonas/physiology , Quorum Sensing , Acyl-Butyrolactones/metabolism , Base Sequence , Gene Expression Regulation, Bacterial , Pseudoalteromonas/genetics , RNA Stability/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Transcription, GeneticABSTRACT
A cultivated form of bacteria (strain 2202) was isolated from the hemal fluid of the bivalve mollusk Modiolus kurilensis. Based on the set of data collected by genetic and physiological/biochemical analyses, the strain was identified as the species Pseudoalteromonas piscicida. Strain 2202 exhibits antimicrobial activity against Staphylococcus aureus, Candida albicans, and Bacillus subtilis but not against Escherichia coli and Pseudomonas aeruginosa. These activities characterize the behavior of strain 2202 as predator-like and classify it as a facultative predator. Being part of the normal microflora in the hemolymph of M. kurilensis, when external conditions change, strain 2202 shows features of opportunistic microflora. The strain 2202 exhibits selective toxicity towards larvae of various invertebrates: it impairs the early development of Mytilus edulis, but not of Strongylocentrotus nudus. Thus, the selective manner in which P. piscicida strains interact with various species of microorganisms and eukaryotes should be taken into consideration when using their biotechnological potential as a probiotic in aquaculture, source of antimicrobial substances, and factors that prevent fouling.
Subject(s)
Bivalvia , Pseudoalteromonas , Animals , Bacterial Physiological Phenomena , Bivalvia/microbiology , Candida/physiology , Hemolymph/microbiology , Microbial Interactions , Pseudoalteromonas/isolation & purification , Pseudoalteromonas/metabolism , Pseudoalteromonas/physiologyABSTRACT
Reliable and accurate in situ sensors capable of detecting and quantifying troublesome marine biofilms on metallic surfaces are increasingly necessary. A 0.2 mm diameter gold electrochemical sensor was fully characterized using cyclic voltammetry in abiotic and biotic artificial seawater media within a continuous culture flow cell to detect the growth and development of an aerobic Pseudoalteromonas sp. biofilm. Deconvolution of the abiotic and biotic responses enable the constituent extracellular electron transfer and biofilm responses to be resolved. Differentiation of enhanced oxygen reduction kinetics within the aerobic bacterial biofilm is linked to enzyme and redox mediator activities.
Subject(s)
Biofilms , Electrochemistry/instrumentation , Gold/chemistry , Pseudoalteromonas/physiology , Aerobiosis , Electrodes , Electron Transport , Kinetics , Pseudoalteromonas/metabolism , Seawater/microbiology , Surface PropertiesABSTRACT
Interfering with the quorum sensing bacterial communication systems has been proposed as a promising strategy to control bacterial biofilm formation, a key process in biofouling development. Appropriate in vitro biofilm-forming bacteria models are needed to establish screening methods for innovative anti-biofilm and anti-microfouling compounds. Four marine strains, two Pseudoalteromonas spp. and two Vibrio spp., were selected and studied with regard to their biofilm-forming capacity and sensitivity to quorum sensing (QS) inhibitors. Biofilm experiments were performed using two biofilm cultivation and quantification methods: the xCELLigence® system, which allows online monitoring of biofilm formation, and the active attachment model, which allows refreshment of the culture medium to obtain a strong biofilm that can be quantified with standard staining methods. Although all selected strains produced acyl-homoserine-lactone (AHL) QS signals, only the P. flavipulchra biofilm, measured with both quantification systems, was significantly reduced with the addition of the AHL-lactonase Aii20J without a significant effect on planktonic growth. Two-species biofilms containing P. flavipulchra were also affected by the addition of Aii20J, indicating an influence on the target bacterial strain as well as an indirect effect on the co-cultured bacterium. The use of xCELLigence® is proposed as a time-saving method to quantify biofilm formation and search for eco-friendly anti-microfouling compounds based on quorum sensing inhibition (QSI) strategies. The results obtained from these two in vitro biofilm formation methods revealed important differences in the response of biosensor bacteria to culture medium and conditions, indicating that several strains should be used simultaneously for screening purposes and the cultivation conditions should be carefully optimized for each specific purpose.
Subject(s)
Biofilms/drug effects , Biofouling/prevention & control , Quorum Sensing/drug effects , Acyl-Butyrolactones/metabolism , Pseudoalteromonas/drug effects , Pseudoalteromonas/physiology , Vibrio/drug effects , Vibrio/physiologyABSTRACT
Many Pseudoalteromonas strains can produce bioactive compounds with antimicrobial activities. This study focused on a probiotic candidate P.flavipulchra CDM8 to reveal its novel antibacterial mechanism and risks for antibiotic resistance dissemination. Strain CDM8 could form floating biofilm, displayed strikingly broad antibacterial activities against multiple Vibrio and Bacillus species, and decreased the competitor's concentration in their co-cultures in the microtiter plate tests. It could also form vesicle/pilus-like structures on the outer surface, which were indicated to participate in the bactericidal activity and represent a novel antibacterial mechanism of CDM8, according to the scanning electron microscopic observation. However, CDM8 displayed multi-antibiotic resistance, conferred by the multidrug resistance regions in hotspot 4 and variable region III of a novel SXT/R391-like integrative and conjugative element (ICEPflCDM8). Summing up, our results provided a better understanding of the bactericidal mechanism of P. flavipulchra and highlighted the role of SXT/R391-like ICEs in conferring multidrug resistance phenotype of probiotic P. flavipulchra candidates.
Subject(s)
Anti-Bacterial Agents/pharmacology , Bacterial Proteins/genetics , Conjugation, Genetic/genetics , DNA Transposable Elements , Drug Resistance, Multiple, Bacterial/genetics , Pseudoalteromonas/drug effects , Pseudoalteromonas/genetics , Biofilms/drug effects , Biofilms/growth & development , Conjugation, Genetic/drug effects , DNA, Bacterial/genetics , Microbial Sensitivity Tests , Probiotics , Pseudoalteromonas/physiology , Vibrio/geneticsABSTRACT
Bacteria commonly exhibit social activities through acyl-homoserine lactones (AHLs)-based quorum sensing (QS) systems to form their unique social network. The sigma factor RpoS is an important regulator that controls QS system in different bacteria. However, the upstream of RpoS involving regulation on QS system remains unclear. In Escherichia coli RpoS is regulated by stringent starvation protein A (SspA), which is dependent of histone-like nucleoid structuring protein (H-NS). To date, the connection between SspA and QS system is essentially unknown. Here, we characterized a typical LuxI/LuxR-type QS system in marine bacterium Pseudoalteromonas sp. T1lg65 which can produce four types of AHLs. The luxI encoding AHLs synthase and luxR encoding AHLs-responsive receptor are co-transcribed, providing advantages in rapidly amplifying QS signaling. Notably, SspA positively regulated luxI/luxR transcription by activating RpoS expression, which is mediated by H-NS. Interestingly, LuxR in turn positively regulated SspA expression. Therefore, SspA and QS system constitute a mutual positive regulation loop in T1lg65. In view of the crucial roles of SspA and QS system in environmental adaption, we believe that the improvement of bacterial tolerance to marine environments could be related to rapidly tuning SspA-involved QS programming.
Subject(s)
Bacterial Proteins/metabolism , Pseudoalteromonas/physiology , Quorum Sensing , Repressor Proteins/metabolism , Trans-Activators/metabolism , Transcription Factors/metabolism , Acyl-Butyrolactones/metabolism , Escherichia coli/metabolism , Escherichia coli Proteins/metabolismABSTRACT
Biofilm formation enhances the survival and persistence of microorganisms in response to environmental stresses. It has been revealed that stringent starvation protein A (SspA) can function as an important regulator dealing with environmental stresses for bacterial survival. However, the connection between SspA and biofilm formation is essentially unclear yet. In this study, we presented evidence showing SspA positively controls biofilm formation by up-regulating exopolysaccharides (EPS) production in marine bacterium Pseudoalteromonas sp. R3. Both qPCR and lacZ reporter system congruously revealed that SspA positively controls the expression of EPS biosynthesis gene cluster. Unlike generally accepted thought that SspA regulates bacterial physiology by inhibiting the expression of histone-like nucleotide structuring protein (H-NS) gene, the function of SspA on EPS production and biofilm formation in Pseudoalteromonas sp. R3 is H-NS-independent. Instead, SspA positively regulates the expression of sigma factor AlgU-encoding gene, thus affecting EPS biosynthesis and biofilm formation. In view of the important role of SspA in biofilm formation, we believe that the improvement of tolerance to marine environmental stresses could be related to tuning of SspA-involved biofilm formation.
Subject(s)
Bacterial Proteins/metabolism , Biofilms/growth & development , Polysaccharides, Bacterial/biosynthesis , Pseudoalteromonas/physiology , Bacterial Proteins/genetics , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Gene Expression Regulation, Bacterial , Genes, Bacterial , Microscopy, Electron, Scanning , Multigene Family , Mutation , Pseudoalteromonas/genetics , Pseudoalteromonas/ultrastructure , Sigma Factor/genetics , Sigma Factor/metabolism , Up-RegulationABSTRACT
The aim of this work was to investigate the bacteria-surface interactions occurring during the first hour of adhesion of marine Pseudoalteromonas NCIMB 2021 at the surface of 2304 lean duplex stainless steel in artificial seawater. A complete characterization of the biofilm and the passive film was performed coupling epifluorescence microscopy, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and time of flight secondary ion mass spectrometry (ToF-SIMS). The coupling of XPS and ToF-SIMS analyses revealed that (1) protein and polysaccharide contents in the biofilm are similar in the presence or absence of nutrients, (2) the biofilm is mainly composed of proteins and the protein content is similar to the one of Tightly Bound EPS, (3) increased bacterial activity due to nutrients leads to chromium enrichment in the passive film in close vicinity to the bacteria.
Subject(s)
Biofilms/growth & development , Pseudoalteromonas/physiology , Stainless Steel/chemistry , Bacterial Adhesion/drug effects , Biofilms/drug effects , Microscopy, Electron, Scanning , Microscopy, Fluorescence , Seawater/microbiology , Spectrometry, Mass, Secondary Ion , Stainless Steel/pharmacology , Surface PropertiesABSTRACT
Pseudoalteromonas luteoviolacea is a globally distributed marine bacterium that stimulates the metamorphosis of marine animal larvae, an important bacteria-animal interaction that can promote the recruitment of animals to benthic ecosystems. Recently, different P. luteoviolacea isolates have been shown to produce two stimulatory factors that can induce tubeworm and coral metamorphosis; Metamorphosis-Associated Contractile structures (MACs) and tetrabromopyrrole (TBP) respectively. However, it remains unclear what proportion of P. luteoviolacea isolates possess the genes encoding MACs, and what phenotypic effect MACs and TBP have on other larval species. Here, we show that 9 of 19 sequenced P. luteoviolacea genomes genetically encode both MACs and TBP. While P. luteoviolacea biofilms producing MACs stimulate the metamorphosis of the tubeworm Hydroides elegans, TBP biosynthesis genes had no effect under the conditions tested. Although MACs are lethal to larvae of the cnidarian Hydractinia symbiologicarpus, P. luteoviolacea mutants unable to produce MACs are capable of stimulating metamorphosis. Our findings reveal a hidden complexity of interactions between a single bacterial species, the factors it produces and two species of larvae belonging to different phyla.
Subject(s)
Bacterial Proteins/metabolism , Metamorphosis, Biological , Pseudoalteromonas/physiology , Animals , Bacterial Proteins/genetics , Biofilms , Genome, Bacterial/genetics , Hydrozoa/growth & development , Hydrozoa/microbiology , Larva/growth & development , Larva/microbiology , Mutation , Polychaeta/growth & development , Polychaeta/microbiology , Pseudoalteromonas/genetics , Pseudoalteromonas/metabolism , Pyrroles/metabolism , Species SpecificityABSTRACT
It is commonly thought that when multiple carbon sources are available, bacteria metabolize them either sequentially (diauxic growth) or simultaneously (co-utilization). However, this view is mainly based on analyses in relatively simple laboratory settings. Here we show that a heterotrophic marine bacterium, Pseudoalteromonas haloplanktis, can use both strategies simultaneously when multiple possible nutrients are provided in the same growth experiment. The order of nutrient uptake is partially determined by the biomass yield that can be achieved when the same compounds are provided as single carbon sources. Using transcriptomics and time-resolved intracellular 1H-13C NMR, we reveal specific pathways for utilization of various amino acids. Finally, theoretical modelling indicates that this metabolic phenotype, combining diauxie and co-utilization of substrates, is compatible with a tight regulation that allows the modulation of assimilatory pathways.
Subject(s)
Carbon/metabolism , Heterotrophic Processes/physiology , Models, Biological , Pseudoalteromonas/physiology , Biomass , Carbon-13 Magnetic Resonance Spectroscopy , Culture Media/metabolism , Kinetics , Proton Magnetic Resonance SpectroscopyABSTRACT
Background: Freeze-drying is known as one of the best methods to preserve bacterial strains. Protectant is the key factor affecting the survival rate of freeze-dried strains. In addition, salinity, bacterial suspension concentration, drying time, and other factors can also affect the survival rate of strains to varying degrees. At present, there are relatively few studies on freeze-drying preservation of marine bacteria. In the present study, we performed the freeze-drying protectant screening and optimized the preservation conditions for Pseudoalteromonas nigrifaciens, which is widely distributed in marine environment. The protective effects of the screened protectants were verified by 18 other marine bacterial strains. Results: The results indicated that the combination of 5.0% (w/v) lactose, 5.0% (w/v) mannitol, 5.0% (w/v) trehalose, 10.0% (w/v) skim milk powder, 0.5% (w/v) ascorbic acid and 0.5% (w/v) gelatin was the best choice for the preservation of P. nigrifaciens. The suggested salinity and concentration of initial cell suspension were 10 g/L NaCl and 1.0 × 109 CFU/mL, respectively. Furthermore, stationary-phase cells were the best choice for the freeze-drying process. The highest survival rate of P. nigrifaciens reached 52.8% when using 510% (w/v) skim milk as rehydration medium. Moreover, the other 18 marine strains belonging to Pseudoalteromonas, Vibrio, Photobacterium, Planomicrobium, Edwardsiella, Enterococcus, Bacillus, and Saccharomyces were freezedried under the abovementioned conditions. Their survival rates were 2.395.1%. Conclusion: Collectively, our results supported that the protectant mixture and parameters were beneficial for lyophilization of marine bacteria
Subject(s)
Preservation, Biological/methods , Pseudoalteromonas/physiology , Freeze Drying/methods , Trehalose/chemistry , Cell Survival , Bacterial Physiological Phenomena , Disaccharides/chemistry , Microbial Viability , Salinity , Lactose/chemistry , Mannitol/chemistryABSTRACT
Predator-prey interactions play important roles in the cycling of marine organic matter. Here we show that a Gram-negative bacterium isolated from marine sediments (Pseudoalteromonas sp. strain CF6-2) can kill Gram-positive bacteria of diverse peptidoglycan (PG) chemotypes by secreting the metalloprotease pseudoalterin. Secretion of the enzyme requires a Type II secretion system. Pseudoalterin binds to the glycan strands of Gram positive bacterial PG and degrades the PG peptide chains, leading to cell death. The released nutrients, including PG-derived D-amino acids, can then be utilized by strain CF6-2 for growth. Pseudoalterin synthesis is induced by PG degradation products such as glycine and glycine-rich oligopeptides. Genes encoding putative pseudoalterin-like proteins are found in many other marine bacteria. This study reveals a new microbial interaction in the ocean.
Subject(s)
Bacterial Proteins/metabolism , Geologic Sediments/microbiology , Gram-Positive Bacteria/physiology , Microbial Interactions/physiology , Pseudoalteromonas/physiology , Alanine/metabolism , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Crystallography, X-Ray , Glutamic Acid/metabolism , Metalloproteases/chemistry , Metalloproteases/genetics , Metalloproteases/metabolism , Molecular Docking Simulation , Mutation , Peptidoglycan/metabolism , Seawater/microbiology , Staphylococcus/physiology , Type II Secretion Systems/metabolismABSTRACT
Biofilms are critical components of most marine systems and provide biochemical cues that can significantly impact overall community composition. Although progress has been made in the bacteria-animal interaction, the molecular basis of modulation of settlement and metamorphosis in most marine animals by bacteria is poorly understood. Here, Pseudoalteromonas marina showing inducing activity on mussel settlement and metamorphosis was chosen as a model to clarify the mechanism that regulates the bacteria-mussel interaction. We constructed a flagellin synthetic protein gene fliP deletion mutant of P. marina and checked whether deficiency of fliP gene will impact inducing activity, motility, and extracellular polymeric substances of biofilms. Furthermore, we examined the effect of flagellar proteins extracted from bacteria on larval settlement and metamorphosis. The deletion of the fliP gene caused the loss of the flagella structure and motility of the ∆fliP strain. Deficiency of the fliP gene promoted the biofilm formation and changed biofilm matrix by reducing ß-polysaccharides and increasing extracellular proteins and finally reduced biofilm-inducing activities. Flagellar protein extract promoted mussel metamorphosis, and ∆fliP biofilms combined with additional flagellar proteins induced similar settlement and metamorphosis rate compared to that of the wild-type strain. These findings provide novel insight on the molecular interactions between bacteria and mussels.
Subject(s)
Biofilms/growth & development , Bivalvia/physiology , Flagellin/genetics , Host Microbial Interactions/physiology , Larva/physiology , Metamorphosis, Biological/physiology , Pseudoalteromonas/genetics , Animals , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Bivalvia/microbiology , China , Flagellin/metabolism , Host Microbial Interactions/genetics , Larva/microbiology , Marine Biology , Mutation , Mytilus/microbiology , Mytilus/physiology , Pseudoalteromonas/cytology , Pseudoalteromonas/physiology , TranscriptomeABSTRACT
Significance: Temperature is one of the most important drivers in shaping protein adaptations. Many biochemical and physiological processes are influenced by temperature. Proteins and enzymes from organisms living at low temperature are less stable in comparison to high-temperature adapted proteins. The lower stability is generally due to greater conformational flexibility. Recent Advances: Adaptive changes in the structure of cold-adapted proteins may occur at subunit interfaces, distant from the active site, thus producing energy changes associated with conformational transitions transmitted to the active site by allosteric modulation, valid also for monomeric proteins in which tertiary structural changes may play an essential role. Critical Issues: Despite efforts, the current experimental and computational methods still fail to produce general principles on protein evolution, since many changes are protein and species dependent. Environmental constraints or other biological cellular signals may override the ancestral information included in the structure of the protein, thus introducing inaccuracy in estimates and predictions on the evolutionary adaptations of proteins in response to cold adaptation. Future Directions: In this review, we describe the studies and approaches used to investigate stability and flexibility in the cold-adapted globins of the Antarctic marine bacterium Pseudoalteromonas haloplanktis TAC125. In fact, future research directions will be prescient on more detailed investigation of cold-adapted proteins and the role of fluctuations between different conformational states.
Subject(s)
Bacterial Proteins/chemistry , Bacterial Proteins/physiology , Cold-Shock Response/physiology , Globins/chemistry , Globins/physiology , Pseudoalteromonas/chemistry , Pseudoalteromonas/physiology , Adaptation, Physiological , Cold Temperature , Protein Conformation , Pseudoalteromonas/enzymology , Structure-Activity RelationshipABSTRACT
Bacteria usually produce, release and detect quorum sensing (QS)-based signal molecules, and successively orchestrate gene expression in respond to environmental changes. Pseudoalteromonas are typical marine bacteria, but knowledge on their QS systems is extremely fragmentary. In this study, genome sequencing of Pseudoalteromonas sp. R3 was performed. Accordingly, a QS working model including three sets of hierarchically organized QS systems was proposed in strain R3. Among them, the typical LuxI/R-type QS system using acyl-homoserine lactones (AHLs) as signal molecules was characterized. Sequence similarity analysis indicated luxI encoding AHLs synthase is novel. The luxR encoding AHLs receptor is directly adjacent to luxI downstream. Notably, mutagenesis demonstrated LuxI and LuxR affect each other at transcriptional level, and both control the AHLs formation. Interestingly, it was found that LuxI/R-type QS system positively involves resistance to streptomycin. Thin-layer chromatography analysis showed strain R3 can produce 3-OH-C6-HSL and C8-HSL, which was supported by heterologous expression of LuxI in Escherichia coli. Sequence alignment analysis indicated that the N-terminal region of LuxI is more conservative than the C-terminal region, revealing the importance of N-terminal region in AHLs synthesis. The obtained findings enrich our knowledge on LuxI/R-type QS system in Pseudoalteromonas and its regulation on adaptation to marine environments.
Subject(s)
Acyl-Butyrolactones/metabolism , Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Pseudoalteromonas/genetics , Quorum Sensing/genetics , Repressor Proteins/genetics , Trans-Activators/genetics , Transcription Factors/genetics , Amino Acid Sequence , Anti-Bacterial Agents/pharmacology , Base Sequence , Gene Expression Regulation, Bacterial/genetics , Genome, Bacterial/genetics , Pseudoalteromonas/drug effects , Pseudoalteromonas/physiology , Sequence Alignment , Signal Transduction/genetics , Streptomycin/pharmacology , Whole Genome SequencingABSTRACT
Quorum sensing is a system of stimuli and response correlated to population density and involves in pathogen infection, colonization, and pathogenesis. Quorum quenching enzymes as quorum sensing inhibitors have been identified in a number of bacteria and been used to control by triggering the pathogenic phenotype. The marine bacteria of Pseudoalteromonas had wide activity of degrading AHLs as a type of signal molecule associated with quorum sensing. We screened many Pseudoalteromonas strains in large scale to explore genes of quorum quenching enzymes from the China seas by whole-genome sequencing rather than genomic library construction. Nine target strains were obtained and an acylases gene APTM01 from the strain MQS005 belonging to PvdQ type on sub-branch in phylogenetic tree. And the heterogenous host containing the vector with target gene could degrade C10-HSL, C12-HSL and OC12-HSL. The obtained AHL acylase gene would be a candidate quorum quenching gene to apply in some fields. We identified that the strains of Pseudoalteromonas have wide AHL-degrading ability depending on quorum quenching. The strains would be a resource to explore new quorum quenching enzymes.
Subject(s)
Amidohydrolases/metabolism , Bacterial Proteins/metabolism , Lactones/metabolism , Pseudoalteromonas/enzymology , Seawater/microbiology , Amidohydrolases/chemistry , Amidohydrolases/genetics , Amino Acid Sequence , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , China , Gene Expression Regulation, Bacterial , Genome, Bacterial , Lactones/chemistry , Phylogeny , Pseudoalteromonas/genetics , Pseudoalteromonas/isolation & purification , Pseudoalteromonas/physiology , Quorum Sensing , Sequence Alignment , Substrate SpecificityABSTRACT
Sponges, which are in close contact with numerous bacteria in prey/predator, symbiotic and pathogenic relationships, must provide an appropriate response in such situations. This starts with a discriminating recognition of the partner either by a physical contact or through secreted molecules or both. We investigated the expression of the Toll-like receptor, Caspase 3/7, Tumor Necrosis Factor receptor-associated factor 6, Bcl-2 homology protein-2 and macrophage expressed genes of axenic sponge cells in the presence of a symbiotic bacterium (Endozoicomonas sp. Hex311), a pathogen bacterium (Pseudoalteromonas sp. 1A1), their exoproducts and lipopolysaccharides. The vast majority of answers are in line with what could be observed with the symbiotic bacterium. The pathogenic bacterium seems to profit from the eukaryotic cell: suppression of the production of the antibacterial compound, inhibition of the apoptosis caspase-dependent pathway, deregulation of bacterial recognition. This work contributes new scientific knowledge in the field of immunology and apoptosis in early branching metazoan harboring within its tissue and cells a large number of symbiotic bacteria.
Subject(s)
Gammaproteobacteria/physiology , Pseudoalteromonas/physiology , Suberites/immunology , Suberites/microbiology , Symbiosis , Animals , Apoptosis/drug effects , Caspase 3/metabolism , Caspase 7/metabolism , Gammaproteobacteria/drug effects , Gammaproteobacteria/metabolism , Immunity , Lipopolysaccharides/pharmacology , Macrophages/immunology , Proto-Oncogene Proteins c-bcl-2/metabolism , Pseudoalteromonas/drug effects , Pseudoalteromonas/metabolism , Pseudoalteromonas/pathogenicity , Suberites/genetics , Toll-Like Receptors/metabolism , Tumor Necrosis Factor Receptor-Associated Peptides and Proteins/metabolismABSTRACT
The hemolymph of healthy marine invertebrates is known to harbor antibiotic-producing bacteria belonging to the genus Pseudoalteromonas. Such strains are potential probiotics to control infectious diseases in aquaculture. In the present study, we screened a collection of Pseudoalteromonas strains isolated from the hemolymph of oyster and mussel for antimicrobial activity against Vibrio harveyi, a pathogenic species responsible for high mortality in abalone. Subsequently, the protective efficacy of the most active strain named hCg-6 was investigated in abalone culture faced with a Vibrio harveyi ORM4 infection. First, we have controlled the Pseudoalteromonas hCg-6 safety for abalone health. To that end, animals were immersed for 4 h in Pseudoalteromonas hCg-6 suspensions in seawater. The abalone viability was monitored and Pseudoalteromonas hCg-6 was tracked by quantitative-PCR in abalone hemolymph. After immersion, no abalone death occurred while the strain hCg-6 was significantly detected in hemolymph. Therefore, the strain hCg-6 was considered safe for abalone and evaluated for its ability to protect abalone against V. harveyi (injection of 1 × 103Vibrio per animal). A 4-h long immersion of abalone in a seawater suspension of Pseudoalteromonas hCg-6 (1 × 106 CFU mL-1) prior to infection with Vibrio harveyi significantly improved the abalone viability. Indeed, 15 days post infection, the hCg-6 treatment used increased the abalone survival rate from 16% in untreated animals to 40% in treated abalone. We hypothesized that Pseudoalteromonas hCg-6 antibacterial activity increased the hemomicrobiota shielding effect. In conclusion, Pseudoalteromonas hCg-6 is a promising anti-Vibrio strain for abalone culture.
Subject(s)
Gastropoda/microbiology , Pseudoalteromonas/physiology , Vibrio Infections/prevention & control , Animals , Bacterial Load , Gastropoda/growth & development , Hemolymph/microbiologyABSTRACT
OBJECTIVES: This study reports the draft genome sequence of Pseudoalteromonas piscicida strain 36Y_RITHPW, a marine Gammaproteobacteria that synthesises bioactive compounds with antagonistic activity against Vibrio parahaemolyticus, a multidrug-resistant strain that is the causative agent of acute hepatopancreatic necrosis disease (AHPND), reported in shrimp farm outbreaks from Asia to Mexico with mortality rates of 80-100%. METHODS: The genome of P. piscicida 36Y_RITHPW was sequenced with an Ion Torrent™ Personal Genome Machine™ (PGM) platform. A total of 606805 reads were constructed for a 308.48Mbp and 33.5×coverage. A high-quality draft assembly and ordering of contigs was obtained with Mauve. The annotation was obtained with RAST and antiSMASH. RESULTS: The genome size consists of 5.15Mbp, with a total of 4548 genes, 4217 protein-coding sequences and a GC content of 43.3%. Several resistance genes as well as other genes involved in the production of bacteriocins and ribosomally synthesised antibacterial peptides are also present. CONCLUSIONS: Mining of this draft genome provides valuable information to explain the antagonistic capacity of P. piscicida 36Y_RITHPW, a useful strain as a potential probiotic in shrimp aquaculture against pathogenic V. parahaemolyticus.