Antarctic Coastal Seawater Research Articles

Genome analysis of a new biosurfactants source: The Antarctic bacterium Psychrobacter sp. TAE2020.

Biosurfactants are considered a possible green alternative to chemical surfactants for countless commercial products including detergents and cleaners, personal care products, cosmetics, pharmaceuticals and therapeutics, food additives, emulsifiers, and dispersants for bioremediation. Organisms from extreme environments are well-adapted to the harsh conditions and represent an exciting avenue of discovery of naturally occurring biosurfactants. In this study, we report the genome analysis of Psychrobacter sp. TAE2020, an aerobic ƴ-proteobacterium isolated from an Antarctic coastal seawater sample collected in the vicinity of the French Antarctic station Dumont d'Urville, Terre Adelie (66°40' S; 140° 01' E) which has been shown to produce biosurfactants. Biochemical assays indicate that Psychrobacter sp. TAE2020 can produce one or more excellent emulsifiers and a biosurfactant which is able to reduce the surface tension of a Gut medium. Next generation sequencing and genome mining allowed the identification of a plethora of biosynthetic gene clusters possibly involved in the production of emulsifying agents, just waiting to be isolated and characterized. This study paves the way for a more thorough investigation into the potential biotechnological applications of this new Antarctic strain.

Horizontal gene transfer and silver nanoparticles production in a new Marinomonas strain isolated from the Antarctic psychrophilic ciliate Euplotes focardii

We isolated a novel bacterial strain from a prokaryotic consortium associated to the psychrophilic marine ciliate Euplotes focardii, endemic of the Antarctic coastal seawater. The 16S rDNA sequencing and the phylogenetic analysis revealed the close evolutionary relationship to the Antarctic marine bacterium Marinomonas sp. BSw10506 and the sub antarctic Marinomonas polaris. We named this new strain Marinomonas sp. ef1. The optimal growth temperature in LB medium was 22 °C. Whole genome sequencing and analysis showed a reduced gene loss limited to regions encoding for transposases. Additionally, five genomic islands, e.g. DNA fragments that facilitate horizontal gene transfer phenomena, were identified. Two open reading frames predicted from the genomic islands coded for enzymes belonging to the Nitro-FMN-reductase superfamily. One of these, the putative NAD(P)H nitroreductase YfkO, has been reported to be involved in the bioreduction of silver (Ag) ions and the production of silver nanoparticles (AgNPs). After the Marinomonas sp. ef1 biomass incubation with 1 mM of AgNO3 at 22 °C, we obtained AgNPs within 24 h. The AgNPs were relatively small in size (50 nm) and had a strong antimicrobial activity against twelve common nosocomial pathogenic microorganisms including Staphylococcus aureus and two Candida strains. To our knowledge, this is the first report of AgNPs biosynthesis by a Marinomonas strain. This biosynthesis may play a dual role in detoxification from silver nitrate and protection from pathogens for the bacterium and potentially for the associated ciliate. Biosynthetic AgNPs also represent a promising alternative to conventional antibiotics against common pathogens.

Complete genome sequence of Granulosicoccus antarcticus type strain IMCC3135T, a marine gammaproteobacterium with a putative dimethylsulfoniopropionate demethylase gene

Granulosicoccus, the only genus of the family Granulosicoccaceae, occupies a distinct phylogenetic position within the order Chromatiales of the Gammaproteobacteria. The genus has been found in various marine regions, especially associated with diverse marine macroalgae. No genomes have been reported for the genus Granulosicoccus thus far, hampering studies on physiology and lifestyles of this genus. Here we report the complete genome sequence of strain IMCC3135T, the type strain of Granulosicoccus antarcticus isolated from Antarctic coastal seawater. The genome was 7.78Mbp long and harbored many genes involved in sulfur metabolism. In particular, a gene for dimethylsulfoniopropionate (DMSP) demethylase was found in the genome, rendering strain IMCC3135T one of the few marine gammaproteobacteria equipped with the potential for DMSP demethylation.

Deinococcus rubrus sp. nov., a Bacterium Isolated from Antarctic Coastal Sea Water.

Two Gram-staining-negative, red-pinkish, coccus-shaped, non-motile, and aerobic bacterial strains, designated Ant21T and Ant22, were isolated from the Antarctic coastal sea water. Strains Ant21T and Ant22 showed UVC and gamma radiation resistance. Phylogenetic analyses based on 16S rRNA gene sequences determined that these strains belong to the genus Deinococcus. Through the analyses of the 16S rRNA gene sequences, strains Ant21T and Ant22 were found to have 97.7% and 97.8% similarity to Deinococcus marmoris DSM 12784T and 97.0% and 97.2% similarity to Deinococcus saxicola AA-1444T, respectively. The sequence similarity with the type strains of other Deinococcus species was less than 96.9% for both strains. Strains Ant21T and Ant22 shared relatively high 16S rRNA gene sequence similarity (99.3%) and had a closely related DNA reassociation value of 84 ± 0.5%. Meanwhile, they showed a low level of DNA-DNA hybridization (<30%) with other closely related species of the genus Deinococcus. The two strains also showed typical chemotaxonomic features for the genus Deinococcus, in terms of the major polar lipid (phosphoglycolipid) and the major fatty acids (C16:0, C16:1ω6c/ω7c, iso-C17:0 , and iso-C15:0). They grew at temperatures between 4°C and 30°C and at pH values of 6.0-8.0. Based on the physiological characteristics, the 16S rRNA gene sequence analysis results, and the low DNA-DNA reassociation level with Deionococcus marmoris, strains Ant21T (= KEMB 9004-167T =JCM 31436T) and Ant22 (KEMB 9004-168 =JCM 31437) represent novel species belonging to the genus Deinococcus, for which the name Deinococcus rubrus is proposed.

Diversity of the aerobic anoxygenic phototrophy gene pufM in Arctic and Antarctic coastal seawaters

Aerobic anoxygenic phototrophic (AAP) bacteria serve important functions in marine carbon and energy cycling because of their capability to utilize dissolved organic substrates and harvest light energy. AAP bacteria are widely distributed in marine environments, and their diversity has been examined in marine habitats. However, information about AAP bacteria at high latitudes remains insufficient to date. Therefore, this study determined the summer AAP bacterial diversity in Arctic Kongsfjorden and in the Antarctic coastal seawater of King George Island on the basis of pufM, a gene that encodes a pigment-binding protein subunit of the reaction center complex. Four pufM clone libraries were constructed, and 674 positive clones were obtained from four investigated stations (two in Kongsfjorden and two in the Antarctic Maxwell Bay). Arctic clones were clustered within the Alphaproteobacteria, whereas Antarctic clones were classified into the Alphaproteobacteria and Betaproteobacteria classes. Rhodobacteraceae-like pufM genes dominated in all samples. In addition, sequences closely related to pufM encoded on a plasmid in Sulfitobacter guttiformis were predominant in both Arctic and Antarctic samples. This result indicates the transpolar or even global distribution of pufM genes in marine environments. Meanwhile, differences between the Arctic and Antarctic sequences may prove polar endemism. These results indicate the important role of Rhodobacteraceae as AAP bacteria in bipolar coastal waters.

Effects of nutrient and temperature on degradation of petroleum hydrocarbons in sub-Antarctic coastal seawater

In an attempt to evaluate the potential of petroleum bioremediation at high latitudes environments, microcosm studies using Antarctic coastal seawater contaminated with diesel or crude oil were conducted in Kerguelen Archipelago (49°22′S, 70°12′E). Microcosms were incubated at three different temperatures (4, 10 and 20°C). During experiments, changes observed in microbial assemblages (total direct count, heterotrophic cultivable microorganisms and hydrocarbon-degrading microorganisms) were generally similar for all incubation temperatures, but chemical data showed only some slight changes in biodegradation indices [Σ(C12–C20)/Σ(C21–C32) and C17/pristane]. The complete data set provided strong evidence of the presence of indigenous hydrocarbon-degrading bacteria in Antarctic seawater and their high potential for hydrocarbon bioremediation. The rate of oil degradation could be increased by the addition of a commercial fertilizer, but water temperature had little effects on biodegradation efficiency which is in conflict with the typical temperature-related assumption predicting 50% rate reduction when temperature is reduced by 10°C. Global warming of Antarctic seawater should not increase significantly the rate of oil biodegradation in these remote regions.

Lewinella antarctica sp. nov., a marine bacterium isolated from Antarctic seawater

A marine bacterium, designated IMCC3223T, was isolated from Antarctic coastal seawater and subjected to a polyphasic taxonomic investigation. Cells of the strain were Gram-negative, short to elongated rods that were orange-coloured but negative for flexirubin-type pigments, obligately aerobic, chemoheterotrophic and devoid of gliding or flagellar motility. On the basis of 16S rRNA gene sequence comparisons, the strain was closely related to members of the genus Lewinella (86.3-93.1 %) of the family 'Saprospiraceae' in the phylum Bacteroidetes; the most closely related species was Lewinella lutea (93.1 % similarity to the type strain). The DNA G+C content of the strain was 50.3 mol% and the major respiratory quinone was MK-7. The predominant cellular fatty acids were C(16 : 1)omega7c/iso-C(15 : 0) 2-OH (39.4 %), iso-C(15 : 0) (15.9 %), C(17 : 1)omega7c (10.5 %) and C(15 : 1)omega6c (8.9 %). 16S rRNA gene sequence analyses and the phenotypic and chemotaxonomic tests allowed the differentiation of strain IMCC3223T from all recognized species of the genus Lewinella. Therefore, strain IMCC3223T represents a novel species of the genus Lewinella, for which the name Lewinella antarctica sp. nov. is proposed. The type strain is IMCC3223T (=KCCM 42688T =NBRC 103142T).

Ulvibacter antarcticus sp. nov., isolated from Antarctic coastal seawater

A seawater bacterium, designated IMCC3101(T), was isolated from Antarctic coastal seawater. The strain was Gram-negative, chemoheterotrophic, obligately aerobic, pigmented dark yellow (flexirubin-type pigments) and devoid of gliding and flagellar motility. On the basis of 16S rRNA gene sequence comparisons, the most closely related species was Ulvibacter litoralis (96.6 %). Phylogenetic trees generated by using 16S rRNA gene sequences confirmed that the strain belonged to the genus Ulvibacter in the family Flavobacteriaceae. The DNA G+C content was 37.0 mol% and the major respiratory quinone was MK-6. Several phenotypic characteristics, including cell and colony morphology, the absence of gliding motility and the temperature range for growth, serve to differentiate the strain from the only species in the genus Ulvibacter with a validly published name (U. litoralis). Therefore, strain IMCC3101(T) represents a novel species of the genus Ulvibacter, for which the name Ulvibacter antarcticus sp. nov. is proposed. The type strain is IMCC3101(T) (=KCCM 42686(T)=NBRC 102682(T)).

Oleispira antarctica gen. nov., sp. nov., a novel hydrocarbonoclastic marine bacterium isolated from Antarctic coastal sea water.

The taxonomic characteristics of two bacterial strains, RB-8(T) and RB-9, isolated from hydrocarbon-degrading enrichment cultures obtained from Antarctic coastal marine environments (Rod Bay, Ross Sea), were determined. These bacteria were psychrophilic, aerobic and Gram-negative with polar flagella. Growth was not observed in the absence of NaCl, occurred only at concentrations of Na+ above 20 mM and was optimal at an NaCl concentration of 3-5% (w/v). The major cellular fatty acids were monounsaturated straight-chain fatty acids. The strains were able to synthesize the polyunsaturated fatty acid eicosapentaenoic acid (20: 5omega3) at low temperatures. The DNA G + C contents were 41-42 mol%. The strains formed a distinct phyletic line within the gamma-Proteobacteria, with less than 89.6% sequence identity to their closest relatives within the Bacteria with validly published names. Both isolates exhibited a restricted substrate profile, with a preference for aliphatic hydrocarbons, that is typical of marine hydrocarbonoclastic micro-organisms such as Alcanivorax, Marinobacter and Oleiphilus. On the basis of ecophysiological properties, G + C content, 16S rRNA gene sequences and fatty acid composition, a novel genus and species within the gamma-Proteobacteria are proposed, Oleispira antarctica gen. nov., sp. nov.; strain RB-8(T) (= DSM 14852(T) = LMG 21398(T)) is the type strain.

Divergence between two Antarctic species of the ciliate Euplotes, E. focardii and E. nobilii, in the expression of heat‐shock protein 70 genes

Most organisms oppose many environmental stresses by rapidly enhancing synthesis of the highly conserved Hsp70 family of heat-shock proteins. Two ciliates which are endemic in Antarctic coastal seawater, Euplotes focardii and E. nobilii, and behave as psychrophile and psychrotroph micro-organisms, respectively, revealed a divergence in the capacity to respond to thermal stress with an activation of the transcription of their hsp70 genes. In both species, these genes were shown to be represented by thousands of copies in the cell's somatic functional nucleus (macronucleus). However, while a strong transcriptional activity of hsp70 genes was induced in E. nobilii cells transferred from 4 to 20 degrees C, a much smaller increase was revealed in heat-shocked cells of E. focardii. These findings suggest a closer adaptation to the stably cold Antarctic waters in the genetic response of E. focardii to thermal stress.

Cadmium, Lead and Copper Complexation in Antarctic Coastal Seawater. Evolution during the Austral Summer

The evolution of cadmium, lead and copper complexation by organic ligands was studied along the water column during the 1990/91 summer in the Gerlache Inlet (Antarctica). The complexation was estimated by determination of the total dissolved concentration of metals, the labile concentration, the ligand concentrations and the relative conditional stability constants. The mean value of the total dissolved cadmium concentration was 0.83 nM until mid-December; the concentration was gradually depleted initially in the subsurface layer then down to the bottom. The mean concentration along the water column in February was 0.15 nM. The labile fraction represented 90% of the total until December, and it was reduced to about 20% in the upper 50 m by February. The cadmium was complexed by one class of ligands detectable after mid-December. Initially it was present only in the surface layers and later was extended to the bottom. The ligand concentration reached a maximum (2.2 nM) during the phytoplankton bloom in December. The mean total dissolved concentration for lead ranged from 0.083 nM until December to 0, 030 nM in the upper 100m at the end of the summer. The labile fraction did not change during the season and meanly represented 39% of the total dissolved concentration. The lead was complexed by one class of ligands, its mean concentration ranges between 0.60 nM at the beginning of the summer to 1.2 nM at the end of the season. The total dissolved copper concentration ranged between 1.6 to 3.8 nM. The labile fraction was strongly dependent on depth and time, ranging from values lower than 1% in surface water to a maximum value of 40% in deep water. The copper was complexed by two classes of ligand, the first present only in surface layers and the second homogeneously distributed along the water column. The results for the three metals are compared to those obtained for surface samples collected in the whole of Terra Nova Bay between summer 1987/88 and summer 1989/90.

Effectiveness of bioremediation for oil-polluted Antarctic seawater

The effectiveness of a specific fertiliser (INIPOL EAP 22) addition on bioremediation of oil-contaminated Antarctic coastal seawater was determined in the “Terre Adelie” area. Mesocosm studies were conducted to evaluate the effects of “Arabian light” crude oil contamination on coastal bacterioplanktonic communities. After oil addition, regular surveys of the bacterial changes of the oil-contaminated seawater were performed during 5-week periods during the austral summer of 1992/1993 and 1993/1994. All results (total, saprophytic and hydrocarbon-utilising bacterial abundance) clearly revealed a significant response of Antarctic bacterial communities to hydrocarbon contamination. A 1 order of magnitude increase of bacterial microflora occurred in seawater after crude oil contamination. A concomitant enrichment in oil-degrading bacteria was generally observed, from less than 0.001% of the community in uncontaminated samples to up to 50% after 3 weeks of contamination. Addition of fertiliser (INIPOL EAP 22) induced clear enhancement of both saprophytic and hydrocarbon-utilising microflora. Chemical analysis of the residual hydrocarbon fractions confirmed that fertiliser application increased the rate of oil biodegradation.

Evolution of Cadmium and Lead Contents in Antarctic Coastal Sea Water During The Austral Summer

The seasonal evolution of the cadmium and lead distribution in the water column of the Gerlache Inlet (Ross Sea) was studied during the 1990–91 austral summer. Measurements were carried out by Anodic Stripping Voltammetry in Antarctica immediately after the collection and filtration of samples. The concentrations of both metals were homogeneous before the phytoplankton bloom with mean values of 0.71 (SD 0.10) and 0.116 (SD 0.014) nmol/1 for cadmium and lead respectively. A subsequent depletion in metal concentration was observed in the shallow waters. The surface concentration of cadmium decreased to about 0.1 nmol/1 at the end of the season. The vertical distribution of lead was less affected by the seasonal evolution and the mean surface concentration decreased to 0.044 nmol/1 in the same period. The results are evaluated with respect to physical and biological processes in the area examined and compared with those obtained on previous expeditions in the same area.

Short-term changes of marine bacterioplankton in antarctic coastal environment

Observations of the short-term changes of seawater bacterioplankton were carried out during the summer of 1988 in Antarctic coastal surface waters. The studies were designed to compare the variations of bacterioplankton in freemoving and enclosed seawater. Even when a diurnal cycle is present the data collected from the enclosed seawater experiments remain much more constant than the corresponding data in free-moving seawater. The wide range of parameters used in the two experiments reveals common properties which illustrate the major role of displacements of water masses at a fixed sampling station in the temporal changes observed in free-moving Antarctic coastal seawater.