Strains Of Marine Bacteria Research Articles

Chemical diversity and antifouling activity of geniculate calcareous algae (Corallinales, Rhodophyta) from Brazil.

Marine biofouling is a natural process by which many organisms colonize and grow in submerged structures, causing serious economic consequences for the maritime industry. Geniculate calcareous algae (GCA; Corallinales, Rhodophyta) produce bioactive secondary metabolites and are a promise for new antifouling compounds. Here, we investigated the antifouling activity of four GCA species-Amphiroa beauvoisii, Jania sagittata (formerly Cheilosporum sagittatum), Jania crassa, and Jania prolifera (formerly Amphiroa flabellata)-from the Brazilian coast against macro- and microorganisms. Simultaneously, metabolomic tools were applied to assess the chemical profiles of these seaweeds using gas chromatography coupled to mass spectrometry (GC-MS). Data analysis by principal component and molecular networking analyses used the global natural products social molecular networking platform (GNPS). Our results showed that all extracts were active against different strains of marine bacteria and that the J. sagittata (JsSI) extract showed the highest percentage of bacterial inhibition. The J. sagittata (JsSI) extract was the most active against the mussel Perna perna, showing 100% byssus inhibition. Regarding toxicity, only the J. crassa (JcP) extract showed a 20% mortality rate. The chemical profiles of the evaluated GCA extracts differed qualitatively and quantitatively. Yet, the steroid (3β)-cholest-5-en-3-ol was the major compound commonly identified in all extracts, with the exception of J. sagittata (JsSI). Moreover, we observed intra- and interspecific chemical variabilities among GCA extracts for the different populations, which could explain their antifouling activity variability. This study contributed new information about the chemical compounds produced by this group of seaweeds and showed its antifouling potential. These GCA species may be the subject of future studies to obtain new bioactive compounds with biotechnological potential in maritime areas.

Synthesis and Antibacterial Activity of Erythromycin 9-Acylhydrazone Derivates.

Some species of Marine bacteria pose great risks to human and mariculture organisms. Meanwhile, Vibrio harveyi and Vibrio parahaemolyticus strains have acquired resistance to many antibiotics. A novel series of erythromycin 9-acylhydrazone derivatives were synthesized and evaluated for their in vitro antibacterial activity against marine pathogens. The site-selective N-acylation of erythromycin hydrazone was achieved using acid chloride/ triethylamine in methanol as the reaction system. All the synthesized target compounds were evaluated for their antibacterial activity by determination of minimum inhibitory concentrations (MICs) using the broth microdilution method. All the tested acylhydrazone compounds showed moderate to high activity with MIC value 0.125-1 μg/mL against Vibrio parahaemolyticus and Vibrio harveyi. The introduction of the acylhydrazone moiety at the C-9 position of erythromycin improved its activity against the above-mentioned marine bacteria strains.

The detection of bacterial exometabolites in marine dissolved organic matter through ultrahigh‐resolution mass spectrometry

AbstractBacteria play a key role in sustaining the chemodiversity of marine dissolved organic matter (DOM), yet there is limited direct evidence of a major contribution of bacterial exometabolites to the DOM pool. This study tests whether molecular formulae of intact exometabolites can be detected in natural DOM via untargeted Fourier‐transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS). We analyzed a series of quantitative mixtures of solid‐phase extracted DOM from the deep ocean, of a natural microbial community and selected model strains of marine bacteria. Under standard instrument settings (200 broadband scans, mass range 92–1000 Da), 77% of molecular formulae were shared between the mesocosm and marine DOM. However, there was < 10% overlap between pure bacterial exometabolome with marine DOM, and in mixing ratios closest to mimicking natural environments (1% bacterial DOM, 99% marine DOM), only 4% of the unique bacterial exometabolites remained detectable. Further experiments with the bacterial exometabolome DOM mixtures using enhanced instrument settings resulted in increased detection of the exometabolites at low concentrations. At 1000 and 10,000 accumulated scans, 23% and 29% of the unique molecular formulae were detectable at low concentrations, respectively. Moreover, windowing a specific mass range encompassing a representative fraction of exometabolites tripled the number of unique detected formulae at low concentrations. Routine FT‐ICR‐MS settings are thus not always sufficient to distinguish bacterial exometabolome patterns from a seawater DOM background. To observe these patterns at higher sensitivity, we recommend a high scan number coupled with windowing a characteristic region of the molecular fingerprint.

Improvement of nitrogen and phosphorus availability by Pseudoalteromonas sp. during salt-washing in saline-alkali soil

In saline-alkali soils, the inactivation of phosphorus and loss of nitrogen resulting in soil infertility could be intensified by salt, which simultaneously leads to pollution of water sphere. However, there is no complete solution for this challenge due to the weak nutrients biological turnover caused by salt dynamic accumulation. In this study, halophilic marine bacteria strains with carriers were screened to decrease the leaching of nitrogen and phosphorus inactivation in saline-alkali soil during salt-washing. Results showed the combination of Pseudoalteromonas sp. CF8-6 and corn cob significantly increased not only soil available phosphorus by 37.03%, but also the soil bioavailable phosphorus content. Moreover, the concentration of TN, NO3−, TP and PO43− in salt washing eluents reduced by corn cob colonized with CF8-6 significantly. It was also found that the abundance of nitrogen-fixing bacteria (such as Azotobacter), and abundance of Proteobacteria and Actinobacteria in soil were all increased by this combination, which were corresponding for the turnover of nitrogen and phosphorus. We demonstrated that the combination of CF8-6 and corn cob has promising potential in improvement of bioavailability of soil nitrogen and phosphorus during the salt-washing process in saline-alkali soil.

Insights into the planktonic to sessile transition in a marine biofilm-forming Pseudoalteromonas isolate using comparative proteomic analysis

Bacterial biofilms play an important role in marine biofouling. The formation of a biofilm starts when marine bacterial cells transition from a planktonic to an attached state. However, the molecular mechanisms involved in this transition are poorly understood. Here, 51 strains of marine bacteria were isolated from natural biofilms growing on submerged artificial surfaces (glass slides, epoxy panels, and bridge pillars) and evaluated for their biofilm-forming capacity. Eleven strains formed relatively strong biofilms and 16S rRNA gene sequence analysis indicated that they belonged to the genera Leisingera, Roseobacter, Pseudoalteromonas, Alteromonas, Tenacibaculum, Vibrio, Chryseobacterium, Aquimarina, and Acinetobacter. Strain Pseudoalteromonas sp. W-7 showed efficient and rapid attachment and was therefore chosen for further study. An iTRAQ-based comparative proteomic analysis of planktonic and attached strain W-7 cells was carried out. A total of 3468 proteins were identified, of which 163 showed significant differential expression (120 down-regulated and 43 up-regulated in attached cells relative to planktonic cells). KEGG (Kyoto encyclopedia of genes and genomes) analysis indicated that pyruvate metabolism, carbon fixation, and carbon metabolism were significantly affected in attached cells. Up-regulated proteins such as UTP-glucose-1-phosphate uridylyltransferase, acetyltransferase component of pyruvate dehydrogenase complex, OmpA-like protein, and acetyl-coenzyme A synthetase may be important during initial adhesion. Our findings provide a deeper understanding of the planktonic to sessile transition of marine fouling bacteria.

Removal of high-molecular-weight polycyclic aromatic hydrocarbons by a microbial consortium immobilized in magnetic floating biochar gel beads

A bacterial consortium immobilized in magnetic floating biochar gel beads is proposed to remove high-molecular-weight polycyclic aromatic hydrocarbons. The microbial consortium performed better than single strains and consisted of four strains of marine bacteria for degrading pyrene (PYR), two strains for benzo(a)pyrene (BAP), and three strains for indeno(1,2,3-cd)pyrene (INP), which were isolated from oil-contaminated seawater. The immobilized cells could biodegrade 89.8%, 66.9% and 78.2% of PYR, BAP and INP, respectively, and had better tolerance to pH, temperature and salinity than free cells. The Andrews model was used to explore the biodegradation kinetics, and when the initial concentrations of PYR, BAP, and INP were 7.80, 3.05, and 3.41 mg/L, the specific biodegradation rates reached maximum values of 0.2507, 0.1286, and 0.1930 d−1, respectively. The immobilized microbial consortium had a high HMW-PAH removal ability and good floatability and magnetic properties and could be collected by an external magnetic field.

Search and Selection of Bacteriocin-Producing Strains of Marine Bacteria in the Aquatic Ecosystems of the Sea of Japan

Given the increasing antibiotic resistance of pathogenic bacteria, alternative antimicrobial strategies are being investigated. One promising area is the study of the antibacterial activity of bacteriocins, special peptides produced by bacteria, which play an important role in regulating the competitive inter- and intraspecific relationships in natural microbial systems. Marine microorganisms are a rich and promising source of bacteriocins. Marine ecosystems contain a huge variety of organisms, up to 90% of which are bacteria living in highly competitive and extreme conditions. Isolation and study of the antibacterial activity of bacteriocins of marine origin is a promising and unexplored area of innovative biotechnology. This article presents the results of a pilot study on the search and selection of bacteriocin-producing strains of marine bacteria from ecosystems of the Sea of Japan. Pseudoalteromonas elyakovii, Cobetia amphilecti, Paraglaciecola mesophila, and Idiomarina abyssalis clusters contain genes similar to Escherichia coli K12: J62 DNA, which are involved in the biosynthesis of colicins (microcin V MccV). This suggests a bacteriocinogenic potential of the studied strains of marine bacteria. The subsequent isolation and study of biological activity of these peptides will make it possible to draw a conclusion about the biological properties and mechanisms of the antagonistic action of these important compounds and the prospects for their use in industrial breeding of seafood (mariculture), as well as for medical and veterinary purposes.

Marine bacterial extracts as a new rich source of drugs against Alzheimer's disease.

Alzheimer's disease (AD) is a prevalent, progressive and irreversible, neurodegenerative disease with no disease modifying treatment yet available. The projected burden of AD on our healthcare system is immense and thus there is an immediate need for new drugs that prevent or attenuate AD symptoms. While most efforts in the field are directed at treatments that reduce amyloid or tau burden in the brain, we have taken an alternate approach - a model based on reducing AD-associated neuronal cell cycle events. Using this model, we have screened a largely unexplored source of compounds with therapeutic potential - the natural products created by diverse strains of marine bacteria. Two hundred and twenty-five bacterial extracts from different strains were tested for both toxicity and neuroprotective properties by crystal violet and In-cell Western -first in HT22 cells andthen in mouse primary neuronal cultures. Based on these screens, we have identified several promising leads, and here we focus on the most promising of these. We found that we could directly assay even a crude bacterial extract in our E16 mouse cortical neuronal cultures and screen for activities that prevent cell cycle reentry and preserve synaptic structure. Preliminary tests in 1-month-old animals from a mouse model of Ataxia telangiectasia, showed that blockage of cell cycle-related neuronal death could also be successful in vivo. This adds an important extension to our in vitro studies. These findings showcase a new effective and efficient assay system and validate the use of marine natural compounds as a novel source for new drugs to fight Alzheimer's disease. Cover Image for this issue: doi: 10.1111/jnc.14733.

Natural rubber based films integrating Zosteric acid analogues as bioactive monomers

This article describes the synthesis and the evaluation of the biological activity of antibacterial bio-based elastomeric materials. The synthesis strategy relies on the photo-copolymerization of macromonomers containing an isoprenic repeating unit (obtained from Natural Rubber) and original monomers designed from Zosteric Acid scaffold (known for its antifouling activity) and covalently bound to the polymer network. The materials were obtained as cross-linked thick films and were characterized by InfraRed Spectroscopy, contact angle, and thermal analyses. No significant release of any bioactive substance was observed after immersions in water, confirming the non-leaching property. Biological assays were carried out with five strains of pathogenic bacteria and three strains of marine bacteria and the results highlighted the antibacterial and fouling release properties of these novel promising materials.

Integrated Genomic and Metabolomic Approach to the Discovery of Potential Anti-Quorum Sensing Natural Products from Microbes Associated with Marine Samples from Singapore.

With 70% of the Earth’s surface covered in water, the marine ecosystem offers immense opportunities for drug discovery and development. Due to the decreasing rate of novel natural product discovery from terrestrial sources in recent years, many researchers are beginning to look seaward for breakthroughs in new therapeutic agents. As part of an ongoing marine drug discovery programme in Singapore, an integrated approach of combining metabolomic and genomic techniques were initiated for uncovering novel anti-quorum sensing molecules from bacteria associated with subtidal samples collected in the Singapore Strait. Based on the culture-dependent method, a total of 102 marine bacteria strains were isolated and the identities of selected strains were established based on their 16S rRNA gene sequences. About 5% of the marine bacterial organic extracts showed quorum sensing inhibitory (QSI) activity in a dose-dependent manner based on the Pseudomonas aeruginosa QS reporter system. In addition, the extracts were subjected to mass spectrometry-based molecular networking and the genome of selected strains were analysed for known as well as new biosynthetic gene clusters. This study revealed that using integrated techniques, coupled with biological assays, can provide an effective and rapid prioritization of marine bacterial strains for downstream large-scale culturing for the purpose of isolation and structural elucidation of novel bioactive compounds.

Comparative transcriptomics as a guide to natural product discovery and biosynthetic gene cluster functionality

Bacterial natural products remain an important source of new medicines. DNA sequencing has revealed that a majority of natural product biosynthetic gene clusters (BGCs) maintained in bacterial genomes have yet to be linked to the small molecules whose biosynthesis they encode. Efforts to discover the products of these orphan BGCs are driving the development of genome mining techniques based on the premise that many are transcriptionally silent during normal laboratory cultivation. Here, we employ comparative transcriptomics to assess BGC expression among four closely related strains of marine bacteria belonging to the genus Salinispora The results reveal that slightly more than half of the BGCs are expressed at levels that should facilitate product detection. By comparing the expression profiles of similar gene clusters in different strains, we identified regulatory genes whose inactivation appears linked to cluster silencing. The significance of these subtle differences between expressed and silent BGCs could not have been predicted a priori and was only revealed by comparative transcriptomics. Evidence for the conservation of silent clusters among a larger number of strains for which genome sequences are available suggests they may be under different regulatory control from the expressed forms or that silencing may represent an underappreciated mechanism of gene cluster evolution. Coupling gene expression and metabolomics data established a bioinformatic link between the salinipostins and their associated BGC, while genetic manipulation established the genetic basis for this series of compounds, which were previously unknown from Salinispora pacifica.

Marine yeasts and bacteria as biological control agents against anthracnose on mango

AbstractThe potential of four yeasts (Debaryomyces hansenii, Rhodotorula minuta, Cryptococcus laurentii and Cryptococcus diffluens) and three bacteria (Bacillus amyloliquefaciens, Bacillus subtilis and Stenotrophomonas rhizophila) with antagonistic capacity against anthracnose caused by Colletotrichum gloeosporioides in mango cv. Ataulfo fruit was investigated. Germination of C. gloeosporioides spores was significantly inhibited by all marine yeasts and bacteria strains of an in vitro test. When yeasts and bacteria were tested on mango fruit, the marine yeast D. hansenii 1R11CB strain and marine bacteria S. rhizophilaKM02 strain were the best antagonists to anthracnose (C. gloeosporioides), which significantly decreased disease incidence by 56% and 89%, respectively, and reduced lesion diameter by 91% and 92%, respectively. All the isolated strains of the phytopathogen, yeasts and bacteria were molecularly identified. Our results from in vitro and in vivo experiments suggest that marine yeasts and bacteria strains can be used as some effective biological control agents for anthracnose in mango.

Structure of aryl O-demethylase offers molecular insight into a catalytic tyrosine-dependent mechanism

Some strains of soil and marine bacteria have evolved intricate metabolic pathways for using environmentally derived aromatics as a carbon source. Many of these metabolic pathways go through intermediates such as vanillate, 3-O-methylgallate, and syringate. Demethylation of these compounds is essential for downstream aryl modification, ring opening, and subsequent assimilation of these compounds into the tricarboxylic acid (TCA) cycle, and, correspondingly, there are a variety of associated aryl demethylase systems that vary in complexity. Intriguingly, only a basic understanding of the least complex system, the tetrahydrofolate-dependent aryl demethylase LigM from Sphingomonas paucimobilis, a bacterial strain that metabolizes lignin-derived aromatics, was previously available. LigM-catalyzed demethylation enables further modification and ring opening of the single-ring aromatics vanillate and 3-O-methylgallate, which are common byproducts of biofuel production. Here, we characterize aryl O-demethylation by LigM and report its 1.81-Å crystal structure, revealing a unique demethylase fold and a canonical folate-binding domain. Structural homology and geometry optimization calculations enabled the identification of LigM's tetrahydrofolate-binding site and protein-folate interactions. Computationally guided mutagenesis and kinetic analyses allowed the identification of the enzyme's aryl-binding site location and determination of its unique, catalytic tyrosine-dependent reaction mechanism. This work defines LigM as a distinct demethylase, both structurally and functionally, and provides insight into demethylation and its reaction requirements. These results afford the mechanistic details required for efficient utilization of LigM as a tool for aryl O-demethylation and as a component of synthetic biology efforts to valorize previously underused aromatic compounds.

Preparation of Antioxidant Peptides from Salmon Byproducts with Bacterial Extracellular Proteases.

Bacterial extracellular proteases from six strains of marine bacteria and seven strains of terrestrial bacteria were prepared through fermentation. Proteases were analyzed through substrate immersing zymography and used to hydrolyze the collagen and muscle proteins from a salmon skin byproduct, respectively. Collagen could be degraded much more easily than muscle protein, but it commonly showed weaker antioxidant capability. The hydrolysate of muscle proteins was prepared with crude enzymes from Pseudoalteromonas sp. SQN1 displayed the strongest activity of antioxidant in DPPH and hydroxyl radical scavenging assays (74.06% ± 1.14% and 69.71% ± 1.97%), but did not perform well in Fe2+ chelating assay. The antioxidant fractions were purified through ultrafiltration, cation exchange chromatography, and size exclusion chromatography gradually, and the final purified fraction U2-S2-I displayed strong activity of antioxidant in DPPH, hydroxyl radical scavenging assays (IC50 = 0.263 ± 0.018 mg/mL and 0.512 ± 0.055 mg/mL), and oxygen radical absorption capability assay (1.960 ± 0.381 mmol·TE/g). The final purified fraction U2-S2-I possessed the capability to protect plasmid DNA against the damage of hydroxyl radical and its effect was similar to that of the original hydrolysis product. It indicated that U2-S2-I might be the major active fraction of the hydrolysate. This study proved that bacterial extracellular proteases could be utilized in hydrolysis of a salmon byproduct. Compared with collagen, muscle proteins was an ideal material used as an enzymatic substrate to prepare antioxidant peptides.

CO2 leaking from sub-seabed storage: Responses of two marine bacteria strains

Carbon capture and storage (CCS) in stable geological locations is one of the options to mitigate the negative effects of global warming produced by the increase in CO2 concentrations in the atmosphere. A CO2 leak is one of the risks associated with this strategy. Marine bacteria attached to the sediment may be affected by an acidification event. Responses of two marine strains (Roseobacter sp. CECT 7117 and Pseudomonas litoralis CECT 7670) were assessed under different scenarios using a range of pH values (7.8, 7, 6.5, 6, and 5.5) to mimic a CO2 leak. A CO2 injection system was used to simulate an escape from a stable sub-seabed. Growth rate (μ), cell number, inhibition of Relative Inhibitory Effect (RI CO2) and inhibited population were analysed as endpoints. P. litoralis showed more sensitivity to high CO2 concentrations than Roseobacter sp. Our results highlight the diversity and resistance in marine bacteria and their capacity to adapt under a stressful CO2 leakage.

Application of Multi-Species Microbial Bioassay to Assess the Effects of Engineered Nanoparticles in the Aquatic Environment: Potential of a Luminous Microbial Array for Toxicity Risk Assessment (LumiMARA) on Testing for Surface-Coated Silver Nanoparticles.

Four different manufactured surface-coated silver nanoparticles (AgNPs) with coating of citrate, tannic acid, polyethylene glycol, and branched polyethylenimine were used in this study. The toxicity of surface-coated AgNPs was evaluated by a luminous microbial array for toxicity risk assessment (LumiMARA) using multi-species of luminescent bacteria. The salt stability of four different AgNPs was measured by UV absorbance at 400 nm wavelength, and different surface-charged AgNPs in combination with bacteria were observed using scanning electron microscopy (SEM). Both branched polyethylenimine (BPEI)-AgNPs and polyethylene glycol (PEG)-AgNPs were shown to be stable with 2% NaCl (non-aggregation), whereas both citrate (Cit)-AgNPs and tannic acid (Tan)-AgNPs rapidly aggregated in 2% NaCl solution. The values of the 50% effective concentration (EC50) for BPEI-AgNPs in marine bacteria strains (1.57 to 5.19 mg/L) were lower than those for the other surface-coated AgNPs (i.e., Cit-AgNPs, Tan-AgNPs, and PEG-AgNPs). It appears that the toxicity of AgNPs could be activated by the interaction of positively charged AgNPs with the negatively charged bacterial cell wall from the results of LumiMARA. LumiMARA for toxicity screening has advantageous compared to a single-species bioassay and is applicable for environmental samples as displaying ranges of assessment results.

Assessing the antimicrobial activity of polyisoprene based surfaces.

There has been an intense research effort in the last decades in the field of biofouling prevention as it concerns many aspects of everyday life and causes problems to devices, the environment, and human health. Many different antifouling and antimicrobial materials have been developed to struggle against bacteria and other micro- and macro-organism attachment to different surfaces. However the “miracle solution” has still to be found. The research presented here concerns the synthesis of bio-based polymeric materials and the biological tests that showed their antifouling and, at the same time, antibacterial activity. The raw material used for the coating synthesis was natural rubber. The polyisoprene chains were fragmented to obtain oligomers, which had reactive chemical groups at their chain ends, therefore they could be modified to insert polymerizable and biocidal groups. Films were obtained by radical photopolymerization of the natural rubber derived oligomers and their structure was altered, in order to understand the mechanism of attachment inhibition and to increase the efficiency of the anti-biofouling action. The adhesion of three species of pathogenic bacteria and six strains of marine bacteria was studied. The coatings were able to inhibit bacterial attachment by contact, as it was verified that no detectable leaching of toxic molecules occurred.

Phenotypic characterization of culturable marine luminous bacteria isolated from coastal waters of the southern Adriatic Sea (Otranto, Italy)

To determine the abundance and species composition of luminous bacteria in the coastal waters of the southern Adriatic Sea (Otranto, Italy), samples were collected from three sites affected by different degrees of anthropogenic pollution. A total of 116 strains of marine luminous bacteria were isolated and subjected to phenotypic characterization, which included 36 biochemical tests. Numerical analysis of the data revealed five clusters with > 86% similarity, which were readily identified as Photobacterium leiognathi, Vibrio fischeri, Vibrio harveyi, Vibrio splendidus biovar I, and Shewanella hanedai. The relative abundance of each species shows that culturable luminous bacteria in the monitored waters are composed mainly of V. harveyi (69.0%), followed by V. fischeri (13.8%) and P. leiognathi (12.1%). In addition, human activity appears to affect the total abundance of luminous bacteria but not the selection of individual species, since the frequencies of the bacteria were similar at all examined sites.

세라믹 담체에 적용된 해양박테리아 4종의 저농도 질소-인 제거

세라믹담체에 적용한 4종의 해양박테리아 (Aeromonas hydrophila, Chryseomonas indologenes, Pseudomonas diminuta, Vibrio parahaemolyticus)의 저농도 질소 인 제거 효율의 변화를 분석하였다. 해양박테리아는 광양만에서 분리 동정하였다. 담체에 적용한 4종의 해양박테리아 모두 대조군에 보다 약 3배 정도의 성장률이 증가하였으며, 암모니아서 질소 제거효율도 30% 이상 증가하였다. 질산성 질소의 제거 효율은 A. hydrophila 균주가 가장 높았으며, 인의 제거는 P. diminuta 균주가 가장 높은 것으로 나타났다. 본 연구의 결과는 세라믹담체는 질소-인 제거 효율 증진에 좋은 재료이며, 분리된 해양박테리아는 현장의 저농도 질소-인 조절에 유용할 수 있음을 보여준다. 【Changes of low concentrated nitrogen-phosphate removal efficiency were investigated in 4 strains of marine bacteria applied to ceramic media. Marine bacteria were isolated and identified from Gwangyang bay. Growth rates and removal efficiencies of $NH_3$ -N of 4 strains of marine bacteria applied to ceramic media were increased approximately 3 fold and over 30% than control group, respectively. A. hydrophila and P. diminuta had highest ${NO_3}^-$ -N and phosphate removal efficiencies, respectively. This results showed that ceramic media is very nice material for improvement of nitrogen-phosphate removal efficiency and isolated marine bacteria may be useful to control nitrogen-phosphate at low concentration in field.】

Detection of quorum sensing systems of bacteria isolated from fouled marine organisms

Abstract N-Acyl homoserine lactones (AHLs or N-AHLs) are a class of signaling molecules involved in bacterial quorum sensing (qs) that have recently been proposed as mediators of the fouling process. In this study, we determined the presence of AHLs in the following marine bacteria strains, which were collected in Santa Marta Bay (Colombia) from heavily fouled surfaces: Ochrobactrum sp., Vibrio sp. (23-6PIN), Vibrio campbellii, Vibrio sp. (11-6DEP), Ochrobactrum pseudogringnonense, Shewanella sp., Vibrio harveyi and Alteromonas sp. The detection and identification of AHLs was conducted using the microbial biosensor Escherichia coli (pSB401) and GC–MS and HPLC-MS analyses. We found that all isolated marine strains had quorum sensing systems mediated by either N-butanoyl homoserine lactone or N-hexanoyl homoserine lactone and in some cases by both. These results are in agreement with the theory that qs is involved in the fouling process. It is noteworthy to mention that we identified qs systems for the first time in bacteria of the genera Ochrobactrum and Alteromonas.