Structural Characterization and Rat Aortic Vascular Reactivity of Bradykinin-Potentiating Peptides (BPPs) from the Snake Venom of Bothrops moojeni from Delta do Parnaíba Region, Brazil.

Snake venoms contain various bradykinin-potentiating peptides (BPPs). First studied for their vasorelaxant properties due to angiotensin converting enzyme (ACE) inhibition, these molecules present a range of binding partners, among them the argininosuccinate synthase (AsS) enzyme. This has renewed interest in their characterization from biological sources and the evaluation of their pharmacological activities. In the present work, the low molecular weight fraction of Bothrops moojeni venom was obtained and BPPs were characterized by mass spectrometry. Eleven BPPs or related peptides were sequenced, and one of them, BPP-Bm01, was new. Interestingly, some oxidized BPPs were detected. The three most abundant peptides were BPP-Bm01, BPP-Bax12, and BPP-13a, and their putative interactions with the AsS enzyme were investigated in silico. A binding cavity for these molecules was predicted, and docking studies allowed their ranking. Three peptides were synthesized and submitted to vasorelaxation assays using rat aortic rings. While all BPPs were active, BPP-Bm01 showed the highest potency in this assay. This work adds further diversity to BPPs from snake venoms and suggests, for the first time, a putative binding pocket for these molecules in the AsS enzyme. This can guide the design of new and more potent AsS activators.

The Peptide Salamandrin-I Modulates Components Involved in Pyroptosis and Induces Cell Death in Human Leukemia Cell Line HL-60.

Amphibian secretions have been extensively investigated for the production of bioactive molecules. Salamandrin-I is an antioxidant peptide, isolated from the skin secretion of the fire salamander, that has induced no toxicity in microglia or erythrocytes. Importantly, the administration of antioxidants may constitute an adequate therapeutic approach to cancer treatment. Here, with the purpose of better characterizing the therapeutic potential of salamandrin-I, we investigated whether this antioxidant peptide also exerts anticancer activity, using the human leukemia cell line HL-60 as a cancer model. Salamandrin-I treatment induced a significant reduction in HL-60 proliferation, which was accompanied by cell cycle arrest. Furthermore, the peptide-induced cell death showed a significant increase in the LDH release in HL-60 cells. The cellular toxicity exerted by salamandrin-I is possibly related to pyroptosis, since the HL-60 cells showed loss of mitochondrial membrane potential and hyperexpression of inflammasome components following the peptide treatment. This is the first demonstration of the anticancer potential of the salamandrin-I peptide. Such results are important, as they offer relevant insights into the field of cancer therapy and allow the design of future bioactive molecules using salamandrin-I as a template.

Antioxidant and Neuroprotective Effects of the First Tryptophyllin Found in Snake Venom (Bothrops moojeni).

In this study, we report the isolation, characterization, and synthesis of the peptide BmT-2 belonging to the tryptophyllins family, isolated from the venom of the snake Bothrops moojeni. This is the first time a tryptophyllin is identified in snake venom. We tested whether BmT-2 had cytotoxic effects and antioxidant activity in a set of experiments that included both in vitro and cell-based assays. BmT-2 presented a radical scavenging activity toward ABTS• and AAPH-derived radicals. BmT-2 protected fluorescein, DNA molecules, and human red blood cells (RBCs) from free radicals generated by the thermal decomposition of AAPH. The novel tryptophyllin was not toxic in cell viability tests, where it (up to 0.4 mg/mL) did not cause hemolysis of human RBCs and did not cause significant loss of cell viability, showing a CC50 > 1.5 mM for cytotoxic effects against SK-N-BE(2) neuroblastoma cells. BmT-2 prevented the arsenite-induced upregulation of Nrf2 in Neuro-2a neuroblasts and the phorbol myristate acetate-induced overgeneration of reactive oxygen species and reactive nitrogen species in SK-N-BE(2) neuroblastoma cells. Electronic structure calculations and full atomistic reactive molecular dynamics simulations revealed the relevant contribution of aromatic residues in BmT-2 to its antioxidant properties. Our study presents a novel peptide classified into the family of the tryptophyllins, which has been reported exclusively in amphibians. Despite the promising results on its antioxidant activity and low cytotoxicity, the mechanisms of action of BmT-2 still need to be further elucidated.

Neuroprotective effects on microglia and insights into the structure-activity relationship of an antioxidant peptide isolated from Pelophylax perezi.

Tryptophyllins constitute a heterogeneous group of peptides that are one of the first classes of peptides identified from amphibian's skin secretions. Here, we report the structural characterization and antioxidant properties of a novel tryptophyllin-like peptide, named PpT-2, isolated from the Iberian green frog Pelophylax perezi. The skin secretion of P. perezi was obtained by electrical stimulation and fractionated using RP-HPLC. De novo peptide sequencing was conducted using MALDI MS/MS. The primary structure of PpT-2 (FPWLLS-NH2 ) was confirmed by Edman degradation and subsequently investigated using in silico tools. PpT-2 shared physicochemical properties with other well-known antioxidants. To test PpT-2 for antioxidant activity in vitro, the peptide was synthesized by solid phase and assessed in the chemical-based ABTS and DPPH scavenging assays. Then, a flow cytometry experiment was conducted to assess PpT-2 antioxidant activity in oxidatively challenged murine microglial cells. As predicted by the in silico analyses, PpT-2 scavenged free radicals in vitro and suppressed the generation of reactive species in PMA-stimulated BV-2 microglia cells. We further explored possible bioactivities of PpT-2 against prostate cancer cells and bacteria, against which the peptide exerted a moderate antiproliferative effect and negligible antimicrobial activity. The biocompatibility of PpT-2 was evaluated in cytotoxicity assays and in vivo toxicity with Galleria mellonella. No toxicity was detected in cells treated with up to 512 µg/ml and in G. mellonella treated with up to 40 mg/kg PpT-2. This novel peptide, PpT-2, stands as a promising peptide with potential therapeutic and biotechnological applications, mainly for the treatment/prevention of neurodegenerative disorders.

BR-bombesin: a novel bombesin-related peptide from the skin secretion of the Chaco tree frog (Boana raniceps) with physiological gastric effects.

Bombesin mediates several biological activities in the gastrointestinal (GI) tract and central nervous system in mammals, including smooth muscle contraction, secretion of GI hormones and regulation of homeostatic mechanisms. Here, we report a novel bombesin-like peptide isolated from Boana raniceps. Its amino acid sequence, GGNQWAIGHFM-NH2, was identified and structurally confirmed by HPLC, MS/MS and 454-pyrosequencing; the peptide was named BR-bombesin. The effect of BR-bombesin on smooth muscle contraction was assessed in ileum and esophagus, and its anti-secretory activity was investigated in the stomach. BR-bombesin exerted significant contractile activity with a concentration-response curve similar to that of commercially available bombesin in ileum strips of Wistar rats. In esophageal strips, BR-bombesin acted as an agonist, as many other bombesin-related peptides act, although with different behavior compared to the muscarinic agonist carbachol. Moreover, BR-bombesin inhibited stomach secretion by approximately 50% compared to the untreated control group. This novel peptide has 80% and 70% similarity with the 10-residue C-terminal domain of human neuromedin B (NMB) and human gastrin releasing peptide (GRP10), respectively. Molecular docking analysis revealed that the GRP receptor had a binding energy equal to - 7.3 kcal.mol-1 and - 8.5 kcal.mol-1 when interacting with bombesin and BR-bombesin, respectively. Taken together, our data open an avenue to investigate BR-bombesin in disorders that involve gastrointestinal tract motility and acid gastric secretion.

The peptide secreted at the water to land transition in a model amphibian has antioxidant effects.

In addition to the morphophysiological changes experienced by amphibians during metamorphosis, they must also deal with a different set of environmental constraints when they shift from the water to the land. We found that Pithecopus azureus secretes a single peptide ([M + H]+ = 658.38 Da) at the developmental stage that precedes the onset of terrestrial behaviour. De novo peptide and cDNA sequencing revealed that the peptide, named PaT-2, is expressed in tandem and is a member of the tryptophyllins family. In silico studies allowed us to identify the position of reactive sites and infer possible antioxidant mechanisms of the compounds. Cell-based assays confirmed the predicted antioxidant activity in mammalian microglia and neuroblast cells. The potential neuroprotective effect of PaT-2 was further corroborated in FRET-based live cell imaging assays, where the peptide prevented lipopolysaccharide-induced ROS production and glutamate release in human microglia. In summary, PaT-2 is the first peptide expressed during the ontogeny of P. azureus, right before the metamorphosing froglet leaves the aquatic environment to occupy terrestrial habitats. The antioxidant activity of PaT-2, predicted by in silico analyses and confirmed by cell-based assays, might be relevant for the protection of the skin of P. azureus adults against increased O2 levels and UV exposure on land compared with aquatic environments.

Mechanistic Insights into the Leishmanicidal and Bactericidal Activities of Batroxicidin, a Cathelicidin-Related Peptide from a South American Viper (Bothrops atrox).

Snake venoms are important sources of bioactive molecules, including those with antiparasitic activity. Cathelicidins form a class of such molecules, which are produced by a variety of organisms. Batroxicidin (BatxC) is a cathelicidin found in the venom of the common lancehead (Bothrops atrox). In the present work, BatxC and two synthetic analogues, BatxC(C-2.15Phe) and BatxC(C-2.14Phe)des-Phe1, were assessed for their microbicidal activity. All three peptides showed a broad-spectrum activity on Gram-positive and -negative bacteria, as well as promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. Circular dichroism (CD) and nuclear magnetic resonance (NMR) data indicated that the three peptides changed their structure upon interaction with membranes. Biomimetic membrane model studies demonstrated that the peptides exert a permeabilization effect in prokaryotic membranes, leading to cell morphology distortion, which was confirmed by atomic force microscopy (AFM). The molecules considered in this work exhibited bactericidal and leishmanicidal activity at low concentrations, with the AFM data suggesting membrane pore formation as their mechanism of action. These peptides stand as valuable prototype drugs to be further investigated and eventually used to treat bacterial and protozoal infections.

Cytotoxic activity of poly-ɛ-caprolactone lipid-core nanocapsules loaded with lycopene-rich extract from red guava (Psidium guajava L.) on breast cancer cells.

The aims of this study were to produce poly-ɛ-caprolactone lipid-core nanocapsules containing lycopene-rich extract from red guava (LEG), to characterize those nanoparticles and to evaluate their cytotoxic effects on human breast cancer cells. Lipid-core nanocapsules containing the extract (nanoLEG) were produced by the method of interfacial deposition of the preformed polymer. The nanoparticles were characterized by Dynamic Light Scattering (DLS), Polydispersity Index, Zeta Potential, pH, Encapsulation Efficiency, Nanoparticle Tracking Analysis (NTA), Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM). Cell viability was evaluated by the MTT dye reduction method in the human breast cancer MCF-7 cell line and inhibition of ROS and NF-κB was assayed in living human microglial cell line (HMC3) by time-lapse images microscopy. A hemolytic activity assay was carried out with sheep blood. Data showed that nanoparticles average size was around 200 nm, nanoparticles concentration/mL was around 0.1 µM, negative zeta potential, pH < 5.0 and spherical shape, with low variation during a long storage period (7 months) at 5 °C, indicating stability of the system and protection against lycopene degradation. The percentage of encapsulation varied from 95% to 98%. The nanoLEG particles significantly reduced the viability of the MCF-7 cells after 24 h (61.47%) and 72 h (55.96%) of exposure, even at the lowest concentration tested (6.25-200 µg/ml) and improved on the cytotoxicity of free LEG to MCF-7. NanoLEG inhibited LPS-induced NF-kB activation and ROS production in microglial cells. The particles did not affect the membrane integrity of sheep blood erythrocytes at the concentrations tested (6.25-200 µg/mL). Thus, the formulation of lipid-core nanocapsules with a polysorbate 80-coated poly-ɛ-caprolactone wall was efficiently applied to stabilize the lycopene-rich extract from red guava, generating a product with satisfactory physico-chemical and biological properties for application as health-promoting nanotechnology-based nutraceutical, emphasizing its potential to be used as a cancer treatment.

The Antioxidant Peptide Salamandrin-I: First Bioactive Peptide Identified from Skin Secretion of Salamandra Genus (Salamandra salamandra).

Amphibian skin is a multifunctional organ that plays key roles in defense, breathing, and water balance. In this study, skin secretion samples of the fire salamander (Salamandra salamandra) were separated using RP-HPLC and de novo sequenced using MALDI-TOF MS/MS. Next, we used an in silico platform to screen antioxidant molecules in the framework of density functional theory. One of the identified peptides, salamandrin-I, [M + H]+ = 1406.6 Da, was selected for solid-phase synthesis; it showed free radical scavenging activity against DPPH and ABTS radicals. Salamandrin-I did not show antimicrobial activity against Gram-positive and -negative bacteria. In vitro assays using human microglia and red blood cells showed that salamandrin-I has no cytotoxicity up to the concentration of 100 µM. In addition, in vivo toxicity tests on Galleria mellonella larvae resulted in no mortality at 20 and 40 mg/kg. Antioxidant peptides derived from natural sources are increasingly attracting interest. Among several applications, these peptides, such as salamandrin-I, can be used as templates in the design of novel antioxidant molecules that may contribute to devising strategies for more effective control of neurological disease.

Antibacterial activity of novel peptide derived from Cry1Ab16 toxin and development of LbL films for foodborne pathogens control.

Escherichia coli is one of the most common etiological agents of diarrhea in developing countries. The appearance of resistant E. coli prevents treatment of these infections. Biotechnological products incorporating antimicrobial peptides are currently being considered in applications to prevent intestinal infections by these bacteria. The aim of this study was to evaluate the antibacterial activity of the peptide PcL342-354C, which is derived from the toxin Cry1Ab16 from Bacillus thuringiensis, against E. coli strains. We also report the preparation, characterization and evaluation of the antibacterial activity of LbL films containing PcL342-354C. The results showed that the PcL342-354C peptide inhibited the growth of different strains of E. coli with minimal inhibitory concentration ranging from 15.62-31.25µg/mL and minimal bactericidal concentration was 250µg/mL, indicating a potential antibacterial activity. The morphology of an ITO/Cashew gum/PcL342-354C film was analysed using atomic force microscopy which showed an increase of roughness due to the increase in the number of layers. The LbL films showed significant antibacterial activity against E. coli NCTC 9001 in both conditions tested (10 and 20 bilayers). Our results indicate that the peptide exhibits an antibacterial potential that can be tapped to develop biomaterials with antibacterial activity for use against foodborne pathogens.

Synergistic effects of in vitro combinations of piplartine, epiisopiloturine and praziquantel against Schistosoma mansoni.

Schistosomiasis is a world health problem, and praziquantel is the only drug currently used for the treatment. There is some evidence that extensive monotherapy of praziquantel may be leading to drug resistance in the parasite. In order to find alternative treatments, the effects of the combination of epiisopiloturine (EPI), piplartine (PPT) and praziquantel (PZQ) were evaluated. Similarity analysis of these compounds was performed using optimized molecular structures to compare the shape and the charge modeling of combinations between PZQ and EPI or PPT. Supported by this data, in vitro association of PZQ-PPT, PZQ-EPI, and EPI-PPT was carried out, and the activity of these combinations against Schistosoma mansoni was assessed. The results showed synergistic activity with a combination index (CI) of 0.42 for the treatment with PZQ-PPT. Both PZQ-EPI and EPI-PPT combinations also showed synergistic effects, with CI values of 0.86 and 0.61, respectively. Surface alterations in the tegument of adult schistosomes after the treatments were observed using laser confocal microscopy and scanning electron microscopy. Additionally, the association of EPI-PPT decreased the cytotoxicity when compared with both isolated compounds in three different lines of mammalian cells. Thus, synergistic combinations of PZQ-PPT, PZQ-EPI, and EPI-PPT create the possibility of reduced doses to be used against Schistosoma mansoni.

Thaulin-1: The first antimicrobial peptide isolated from the skin of a Patagonian frog Pleurodema thaul (Anura: Leptodactylidae: Leiuperinae) with activity against Escherichia coli.

Patagonia's biodiversity has been explored from many points of view, however, skin secretions of native amphibians have not been evaluated for antimicrobial peptide research until now. In this sense, Pleurodema thaul is the first amphibian specie to be studied from this large region of South America. Analysis of cDNA-encoding peptide in skin samples allowed identification of four new antimicrobial peptides. The predicted mature peptides were synthesized and all of them showed weak or null antimicrobial activity against Klebsiella pneumoniae, Staphylococcus aureus and Escherichia coli with the exception of thaulin-1, a cationic 26-residue linear, amphipathic, Gly- and Leu-rich peptide with moderate antimicrobial activity against E. coli (MIC of 24.7µM). AFM and SPR studies suggested a preferential interaction between these peptides and bacterial membranes. Cytotoxicity assays showed that thaulin peptides had minimal effects at MIC concentrations towards human and animal cells. These are the first peptides described for amphibians of the Pleurodema genus. These findings highlight the potential of the Patagonian region's unexplored biodiversity as a source for new molecule discovery.

Antibacterial, antibiofilm and cytotoxic activities of Terminalia fagifolia Mart. extract and fractions.

BACKGROUND: The methicillin resistance of bacteria from the genus Staphylococcus and its ability to form biofilms are important factors in pathogenesis of these microorganisms. Thus, the search for new antimicrobials agents, especially from plants, has been intensified. In this context, Terminalia species have been the subject of research for many pharmacological activities. In this study we evaluated the antibacterial, antibiofilm and cytotoxic activities of the ethanol extract (EtE) from Terminalia fagifolia stem bark as well as that of three fractions of the extract (AqF, HaF and WSF). METHODS: We determined the minimum inhibitory concentration (MIC) by microdilution in 96-well plates, where the strains were exposed to serial dilutions of the ethanol extract and fractions, ranging from 12.5 to 400 µg/mL. We then determined the minimum bactericidal concentration (MBC), seeding the inoculum (10 µL) with concentrations equal to or greater than the MIC in Mueller-Hinton agar. To test the antibiofilm activity biofilm formation was induced in the presence of concentrations equivalent to 1/2, 1/4 and 1/8 of the MIC extract or fraction tested. In addition, the effect of the EtE and the fractions on cell viability was tested by the MTT assay on human MCF-7 breast cancer and mouse fibroblast NIH/3T3. To obtain high-resolution images of the effect of the aqueous fraction on the bacterial morphology, atomic force microscopy (AFM) imaging of treated S. aureus cells was performed. RESULTS: We observed antibacterial activity of EtE and fractions with MICs ranging from 25-200 µg/mL and MBCs ranging from 200-400 µg/mL. Regarding antibiofilm activity, both the EtE as the AqF, HaF and WSF fractions showed significant inhibition of the biofilm formation, with inhibition of biofilms formation of over 80% for some strains. The EtE and fractions showed a moderate cytotoxicity in cell line NIH/3T3 viability and potential antitumoral activity on human breast cancer cell line MCF-7. The microscopic images obtained revealed morphological changes to the S. aureus ATCC 29213 surface caused by AqF, as well as significant size alterations. CONCLUSIONS: The results show potential antibacterial, antibiofilm and antitumoral activities of the ethanol extract and fractions of T. fagifolia.

Anthelmintic activity in vivo of epiisopiloturine against juvenile and adult worms of Schistosoma mansoni.

Schistosomiasis is a serious disease currently estimated to affect more that 207 million people worldwide. Due to the intensive use of praziquantel, there is increasing concern about the development of drug-resistant strains. Therefore, it is necessary to search for and investigate new potential schistosomicidal compounds. This work reports the in vivo effect of the alkaloid epiisopiloturine (EPI) against adults and juvenile worms of Schistosoma mansoni. EPI was first purified its thermal behavior and theoretical solubility parameters charaterised. In the experiment, mice were treated with EPI over the 21 days post-infection with the doses of 40 and 200 mg/kg, and 45 days post-infection with single doses of 40, 100 and 300 mg/kg. The treatment with EPI at 40 mg/kg was more effective in adult worms when compared with doses of 100 and 300 mg/kg. The treatment with 40 mg/kg in adult worms reduced parasite burden significantly, lead to reduction in hepatosplenomegaly, reduced the egg burden in faeces, and decreased granuloma diameter. Scanning electron microscopy revealed morphological changes to the parasite tegument after treatment, including the loss of important features. Additionally, the in vivo treatment against juvenile with 40 mg/kg showed a reduction of the total worm burden of 50.2%. Histopathological studies were performed on liver, spleen, lung, kidney and brain and EPI was shown to have a DL50 of 8000 mg/kg. Therefore EPI shows potential to be used in schistosomiasis treatment. This is the first time that schistosomicidal in vivo activity of EPI has been reported.

A soft strategy for covalent immobilization of glutathione and cysteine capped quantum dots onto amino functionalized surfaces.

A novel strategy for immobilization of CdTe quantum dots (QDs) onto amino functionalized solid supports was developed. QDs capped with compounds holding an amino group were covalently bonded to the substrate under mild reaction conditions, exhibiting great stability and strong luminescence.

Infection by Plasmodium changes shape and stiffness of hepatic cells.

Infection of liver cells by Plasmodium, the malaria parasite, is a clinically silent, obligatory step of the parasite's life cycle. The authors studied the progression of Plasmodium infection in hepatic cells by atomic force microscopy, measuring both topographical and nanomechanical changes upon infection. In recent years, several studies have suggested that cellular nanomechanical properties can be correlated with disease progression. The authors' results show that infected cells exhibit considerable topographical changes, which can be correlated with the presence of the parasite, leading to a significant roughening of the cell membrane. The nanomechanical measurements showed that infected cells were significantly stiffer than noninfected cells. Furthermore, the stiffening of the cells appeared to be a cellular reaction to the Plasmodium infection, rather than a result of the stiffness of the invading parasites themselves. This article provides the first evidence of mechanical changes occurring in hepatic cells in response to Plasmodium infection. FROM THE CLINICAL EDITOR: The authors have studied the progression of Plasmodium infection in hepatic cells by atomic force microscopy, measuring topographical and nanomechanical changes upon infection. The nanomechanical measurements demonstrated that infected cells were significantly stiffer than noninfected cells.

AFM and electron microscopy study of the unusual aggregation behavior of metallosurfactants based on iron(II) complexes with bipyridine ligands.

The aggregation behavior in water-rich solutions of five iron(II) complexes with alkylated derivatives of 2,2'-bipyridine was studied by electron microscopy (cryo-SEM, SEM, and TEM) and AFM. The results obtained by cryo-SEM on frozen colloidal solutions show that the morphology of the aggregates strongly depends on the length of the alkyl chains in the bipyridine ligands, with shorter alkyl chains forming rod-like structures, whereas for compounds with longer alkyl chains, only spherical structures were detected. The self-aggregates were further characterized by SEM and TEM. The results show that their overall morphology depends only on the length of the alkyl chain of the bipyridine ligands and that the samples show a broad size distribution. In addition, TEM and SEM were used to study the stability of the self-aggregates in solution, the effect of addition of methanol, and the temperature used in the preparation of the colloidal solutions. AFM studies of the aggregates either dried in ambient conditions or dehydrated by long drying under vacuum showed partially collapsed self-aggregates in the latter case, showing that the aggregates contain water in their core, indicating that the self-aggregation leads to vesicle-type structures.

Gold and gold-iron oxide magnetic glyconanoparticles: synthesis, characterization and magnetic properties.

The preparation, characterization and the magnetic properties of gold and gold-iron oxide glyconanoparticles (GNPs) are described. Glyconanoparticles were prepared in a single step procedure in the presence of aqueous solution of thiol functionalized neoglycoconjugates and either gold salts or both gold and iron salts. Neoglycoconjugates of lactose and maltose disaccharides with different linkers were used. Iron-free gold or gold-iron oxide GNPs with controlled gold-iron ratios were obtained. The average core-size diameters are in the range of 1.5-2.5 nm. The GNPs are fully characterized by (1)H NMR spectrometry, transmission electron microscopy (TEM), and UV-vis and X-ray absorption (XAS) spectroscopies. Inductive plasma-atomic emission spectrometry (ICP) and elemental analysis gave the average number of neoglycoconjugates per cluster. The magnetic properties were measured in a SQUID magnetometer. The most remarkable results was the observation of a permanent magnetism up to room temperature in the iron-free gold GNPs, that was not present in the corresponding gold-iron oxide GNPs.

Desulfovibrio alaskensis sp. nov., a sulphate-reducing bacterium from a soured oil reservoir.

A novel sulphate-reducing bacterium (Al1T) was recovered from a soured oil well in Purdu Bay, Alaska. Light and atomic force microscopy observations revealed that cells were Gram-negative, vibrio-shaped and motile by means of a single polar flagellum. The carbon and energy sources used by the isolate and the salinity, temperature and pH ranges facilitating its growth proved to be typical of a partial lactate-oxidizing, moderately halophilic, mesophilic, sulphate-reducing bacterium. Analysis of the fatty acid profile revealed that C(18 : 0), isoC(15 : 0) and isoC(17 : 1)omega7c were the predominant species. Fatty acid profile and complete 16S rRNA gene sequencing demonstrated the similarity between strain Al1T and members of the genus Desulfovibrio. The position of strain Al1T within the phylogenetic tree indicated that it clustered closely with Desulfovibrio vietnamensis DSM 10520T (98.9 % sequence similarity), a strain recovered from a similar habitat. However, whole-cell protein profiles, Fourier-transform infrared studies and DNA-DNA hybridization demonstrated that, in spite of the high level of 16S rRNA gene sequence similarity, there is sufficient dissimilarity at the DNA sequence level between D. vietnamensis DSM 10520T and strain Al1T (10.2 % similarity) to propose that strain Al1T belongs to a separate species within the genus Desulfovibrio. Based on the results obtained, the name Desulfovibrio alaskensis sp. nov. is therefore proposed, with Al1T (= NCIMB 13491T = DSM 16109T) as the type strain.