Triacylglycerol accumulation and oxidative stress in Rhodococcus species: differential effects of pro-oxidants on lipid metabolism

In general, members of Rhodococcus genus are highly resistant to desiccation. Desiccation is a complex process which includes the formation of reactive oxygen species that results in significant damage to cells. In this study, we demonstrate that extremophile actinobacterial strains isolated from diverse environments, mainly belonging to Rhodococcus genus, exhibited high tolerance to the pro-oxidants hydrogen peroxide (H₂O₂) and methyl viologen (MV). In addition, we investigated the possible interconnections between the responses of the oleaginous Rhodococcus opacus PD630 to oxidative stress and lipid metabolism, since both processes demand a metabolic reorganization of cells. Experiments with metabolic inhibitors showed differential effects of both pro-oxidants on lipid metabolism in PD630 cells. The inhibition of carotenoid biosynthesis by the addition of diphenylamine to the media negatively affected the tolerance of cells to H₂O₂, but not to MV. The inhibition of triacylglycerol (TAG) biosynthesis and accumulation in PD630 did not affect the tolerance of cells to H₂O₂ and MV; whereas, the blockage of lipolysis decreased the tolerance of cells to H₂O₂ (but not MV) under carbon-starvation conditions. Interestingly, the addition of MV to the media (but not H₂O₂) induced a reduction of TAG accumulation by cells. Resuming, results of this study revealed metabolic connections between lipid metabolism and oxidative stress responses in R. opacus PD630, and probably in other extremophile TAG-accumulating rhodococci.     

Investigation of lipid production by nitrogen-starved <Emphasis Type="Italic">Parachlorella kessleri</Emphasis> under continuous illumination and day/night cycles for biodiesel application

This study aims to investigate the triacylglycerol (TAG) productivity of Parachlorella kessleri grown under continuous illumination and to investigate its metabolism in simulated day/night cycles in order to estimate the feasibility of a large-scale production in outdoor solar photobioreactors. The strain was chosen for its ability to accumulate large amounts of triacylglycerol during nitrogen starvation. Several protocols of nitrogen starvation were tested in continuous illumination as well as in simulated day/night cycles. Sudden and progressive nitrogen starvation conditions have enhanced the TAG concentration and productivity of P. kessleri reaching up to 48 dry wt% and 4.4 × 10^?3 kg m^?2 day^?1, respectively. Microalgal cell metabolism was significantly affected by the day/night illumination cycles. The energy-rich compounds (TAGs and carbohydrates) were accumulated by P. kessleri during the photoperiods and partly consumed during the dark to sustain the microalgae vitality. This TAG oxidation ultimately led to a 26% decrease in TAG productivity in cultures exposed to day/night cycles compared to ones exposed to continuous illumination of equal 24-h average photon flux density. The results can dictate the optimal time for harvesting cells for recovering the largest amount of TAGs.     

AP2/EREBP transcription factors are part of gene regulatory networks and integrate metabolic, hormonal and environmental signals in stress acclimation and retrograde signalling

Growth of five aeroterrestrial green algal strains (Trebouxiophyceae) in response to changing water availabilities—caused by osmotic (ionic) and matric (desiccation) stresses—was investigated in comparison with a freshwater and a marine strain. All investigated algae displayed good growth under brackish conditions while four out of the five aeroterrestrial strains even grew well under full marine conditions (28–40 psu). The comparison between growth responses in liquid medium, on solid agarose, and on glass fiber filters at 100% air humidity indicated a broad growth tolerance of aeroterrestrial algae towards diminished water availability. While two aeroterrestrial strains even grew better on solid medium which mimics natural biofilm conditions, the aquatic strains showed significant growth inhibition under matric stress. Except Stichococcus sp., which contained the C6-polyol sorbitol, all other aeroterrestrial green algae investigated synthesized and accumulated the C5-polyol ribitol in response to osmotic stress. Using ¹³C NMR spectroscopy and HPLC, it could be verified that ribitol functions as an osmotically regulated organic solute. This is the first proof of ribitol in free-living aeroterrestrial green algae. The biochemical capability to synthesize polyols under environmental stress conditions seems to support algal life outside aquatic habitats.     

Nitrogen-starvation triggers cellular accumulation of triacylglycerol in Metarhizium robertsii

Nitrogen starvation can induce cellular triacylglycerol (TAG) accumulation in different organisms with an unclear mechanism. In this study, we performed nutrient starvation and lipid droplet (LD) proteomics analyses of the filamentous fungus Metarhizium robertsii. Our results indicated that nitrogen starvation activated cell autophagic activity but inhibited the internalization of LDs into vacuoles for degradation. LD proteomic analyses identified an array of differentially accumulated proteins including autophagy-related (ATG) proteins, heat shock proteins, TAG metabolic and phospholipid biosynthetic enzymes when the fungus was grown in different nutrient conditions. In contrast to the highly activated MrATG8, the ATG proteins involved in vacuolar LD internalization were down-regulated after nitrogen starvation. Cellular TAG contents were increased in different ATG-gene null mutants of M. robertsii. In addition, TAG increase could be due to the up-regulation of TAG biogenesis along with the down-regulation of TAG catabolic enzymes in fungal cells after nitrogen deprivation. The data of this study benefit our understanding of the mechanism of nitrogen starvation induced TAG increase in different cells.     

Physiological characterization of lipid accumulation and in vivo ester formation in Gordonia sp. KTR9

Previous work has demonstrated the feasibility of in vivo biodiesel synthesis in Escherichia coli, however, ethyl ester formation was dependent on an external fatty acid feedstock. In contrast to E. coli, actinomycetes may be ideal organisms for direct biodiesel synthesis because of their capacity to synthesize high levels of triacylglcerides (TAGs). In this study, we investigated the physiology and associated TAG accumulation along with the in vivo ability to catalyze ester formation from exogenous short chain alcohol sources in Gordonia sp. KTR9, a strain that possesses a large number of genes dedicated to fatty acid and lipid biosynthesis. Total lipid fatty acids content increased by 75 % and TAG content increased by 50 % under nitrogen starvation conditions in strain KTR9. Strain KTR9 tolerated the exogenous addition of up to 4 % methanol, 4 % ethanol and 2 % propanol in the media. Increasing alcohol concentrations resulted in a decrease in the degree of saturation of recovered fatty acid alcohol esters and a slight increase in the fatty acid chain length. A linear dose dependency in fatty alcohol ester synthesis was observed in the presence of 0.5–2 % methanol and ethanol compared to control KTR9 strains grown in the absence of alcohols. An inspection of the KTR9 genome revealed the presence of several putative wax ester synthase/acyl-coenzyme A?:?diacylglycerol acyltransferase (WS/DGAT) enzymes, encoded by atf gene homologs, that may catalyze the in vivo synthesis of fatty acid esters from short chain alcohols. Collectively, these results indicate that Gordonia sp. KTR9 may be a suitable actinomycete host strain for in vivo biodiesel synthesis.     

Desiccation tolerance in diapausing spider mites Tetranychus urticae and T. kanzawai (Acari: Tetranychidae)

We investigated the effects of changes in vapor pressure deficit (VPD) on the survival of diapausing (winter form) and non-diapausing (summer form) spider mites Tetranychus urticae Koch and Tetranychus kanzawai Kishida (Acari: Tetranychidae). Adult females of both species were kept without food at VPDs of 0.0, 0.4, 0.7, 1.5, 1.9, or 2.7 kPa for 3, 6, 9, 12, or 15 days at 25 °C. Diapausing females of both species kept at a VPD of ≥0.4 kPa for ≥6 days clearly tolerated desiccation. Under water-saturated conditions (VPD = 0.0 kPa), in which no desiccation occurred, diapausing females showed high starvation tolerance: 90 % survived for up to 15 days. No interspecific differences in tolerance to desiccation or starvation were observed under most conditions. These results indicate that diapause functions increase tolerance to desiccation and starvation. Such multiple tolerances to harsh environments might support winter survival in spider mites.     

High temperature enhances lipid accumulation in nitrogen-deprived <Emphasis Type="Italic">Scenedesmus obtusus</Emphasis> XJ-15

This study investigated the changes in lipid and starch contents, lipid fraction, and lipid profile in the nitrogen-starved Scenedesmus obtusus XJ-15 at different temperatures (17, 25, and 33 °C). The optimal temperature for both growth and lipid accumulation under nitrogen-sufficient condition was found to be 25 °C. However, under nitrogen deprivation, the total and neutral lipids increased with increasing temperature, and achieved the highest lipid content of 47.60 % of dry cell weight and the highest TAG content of 79.66 % of total lipid at 33 °C. In the meantime, the stored cellular starch content decreased with the increasing temperature. Thus, high temperature induced carbon flux from starch toward TAG accumulation in microalgae during nitrogen starvation. In addition, the decreased polar lipids may also serve for TAG synthesis under high temperature, and high temperature further reduced the degree of the fatty acid unsaturation and favored a better biodiesel production. These results suggested that high-temperature stress can be a good strategy for enhancing biofuel production in oleaginous microalgae during nitrogen deficiency.     

Highly enantioselective oxidation of phenyl methyl sulfide and its derivatives into optically pure (S)-sulfoxides with Rhodococcus sp. CCZU10-1 in an n-octane–water biphasic system

Enantiopure sulfoxides can be prepared via the asymmetric oxidation of sulfides using sulfide monooxygenases. The n-octane–water biphasic system was chosen for the bio-oxidation of a water-insoluble phenyl methyl sulfide (PMS) by Rhodococcus sp. CCZU10-1. In this n-octane–water system, the optimum reaction conditions were obtained. (S)-phenyl methyl sulfoxide ((S)-PMSO) with >99.9 % enantiomeric excess formed at 55.3 mM in the n-octane–water biphasic system. Using fed-batch method, a total of 118 mM (S)-PMSO accumulated in 1-L reaction mixture after the 7th feed, and no (R)-PMSO and sulfone were detected. Moreover, Rhodococcus sp. CCZU10-1 displayed fairly good activity and enantioselectivity toward other sulfides. In conclusion, Rhodococcus sp. CCZU10-1 is a promising biocatalyst for synthesizing highly optically active sulfoxides.     

Analysis of storage lipid accumulation in Alcanivorax borkumensis: Evidence for alternative triacylglycerol biosynthesis routes in bacteria

Marine hydrocarbonoclastic bacteria, like Alcanivorax borkumensis, play a globally important role in bioremediation of petroleum oil contamination in marine ecosystems. Accumulation of storage lipids, serving as endogenous carbon and energy sources during starvation periods, might be a potential adaptation mechanism for coping with nutrient limitation, which is a frequent stress factor challenging those bacteria in their natural marine habitats. Here we report on the analysis of storage lipid biosynthesis in A. borkumensis strain SK2. Triacylglycerols (TAGs) and wax esters (WEs), but not poly(hydroxyalkanoic acids), are the principal storage lipids present in this and other hydrocarbonoclastic bacterial species. Although so far assumed to be a characteristic restricted to gram-positive actinomycetes, substantial accumulation of TAGs corresponding to a fatty acid content of more than 23% of the cellular dry weight is the first characteristic of large-scale de novo TAG biosynthesis in a gram-negative bacterium. The acyltransferase AtfA1 (ABO_2742) exhibiting wax ester synthase/acyl-coenzyme A:diacylglycerol acyltransferase (WS/DGAT) activity plays a key role in both TAG and WE biosynthesis, whereas AtfA2 (ABO_1804) was dispensable for storage lipid formation. However, reduced but still substantial residual TAG levels in atfA1 and atfA2 knockout mutants compellingly indicate the existence of a yet unknown WS/DGAT-independent alternative TAG biosynthesis route. Storage lipids of A. borkumensis were enriched in saturated fatty acids and accumulated as insoluble intracytoplasmic inclusions exhibiting great structural variety. Storage lipid accumulation provided only a slight growth advantage during short-term starvation periods but was not required for maintaining viability and long-term persistence during extended starvation phases.     

Use of sodium bicarbonate to stimulate triacylglycerol accumulation in the chlorophyte Scenedesmus sp. and the diatom Phaeodactylum tricornutum

There is potential for algal-derived biofuel to help alleviate part of the world’s dependency on petroleum based fuels. However, research must still be done on strain selection, induction of triacylglycerol (TAG) accumulation, and fundamental algal metabolic studies, along with large-scale culturing techniques, harvesting, and biofuel/biomass processing. Here, we have advanced the knowledge on Scenedesmus sp. strain WC-1 by monitoring growth, pH, and TAG accumulation on a 14:10 light–dark cycle with atmospheric air or 5% CO₂ in air (v/v) aeration. Under ambient aeration, there was a loss of pH-induced TAG accumulation, presumably due to TAG consumption during the lower culture pH observed during dark hours (pH 9.4). Under 5% CO₂ aeration, the growth rate nearly doubled from 0.78 to 1.53 d^?1, but the pH was circumneutral (pH 6.9) and TAG accumulation was minimal. Experiments were also performed with 5% CO₂ during the exponential growth phase, which was then switched to aeration with atmospheric air when nitrate was close to depletion. These tests were run with and without the addition of 50 mM sodium bicarbonate. Cultures without added bicarbonate showed decreased growth rates with the aeration change, but there was no immediate TAG accumulation. The cultures with bicarbonate added immediately ceased cellular replication and rapid TAG accumulation was observed, as monitored by Nile Red fluorescence which has previously been correlated by gas chromatography to cellular TAG levels. Sodium bicarbonate addition (25 mM final concentration) was also tested with the marine diatom Phaeodactylum tricornutum strain Pt-1 and this organism also accumulated TAG.     

Conversion of membrane lipid acyl groups to triacylglycerol and formation of lipid bodies upon nitrogen starvation in biofuel green algae Chlorella UTEX29

Algal lipids are ideal biofuel sources. Our objective was to determine the contributors to triacylglycerol (TAG) accumulation and lipid body formation in Chlorella UTEX29 under nitrogen (N) deprivation. A fivefold increase in intracellular lipids following N starvation for 24 h confirmed the oleaginous characteristics of UTEX29. Ultrastructural studies revealed increased number of lipid bodies and decreased starch granules in N-starved cells compared to N-replete cells. Lipid bodies were observed as early as 3 h after N removal and plastids collapsed after 48 h of stress. Moreover, the identification of intracellular pyrenoids and differences in the expected nutritional requirements for Chlorella protothecoides (as UTEX29 is currently classified) led us to conduct a phylogenetic study using 18S and actin cDNA sequences. This indicated UTEX29 to be more phylogenetically related to Chlorella vulgaris. To investigate the fate of different lipids after N starvation, radiolabeling using ¹⁴C-acetate was used. A significant decrease in ¹⁴C-galactolipids and phospholipids matched the increase in ¹⁴C-TAG starting at 3 h of N starvation, consistent with acyl groups from structural lipids as sources for TAG under N starvation. These results have important implications for the identification of key steps controlling oil accumulation in N-starved biofuel algae and demonstrate membrane recycling during lipid body formation.     

Intracellular Metabolic Changes of <Emphasis Type="Italic">Rhodococcus</Emphasis> sp. LH During the Biodegradation of Diesel Oil

In recent years, some marine microbes have been used to degrade diesel oil. However, the exact mechanisms underlying the biodegradation are still poorly understood. In this study, a hypothermophilous marine strain, which can degrade diesel oil in cold seawater was isolated from Antarctic floe-ice and identified and named as Rhodococcus sp. LH. To clarify the biodegradation mechanisms, a gas chromatography-mass spectrometry (GC-MS)-based metabolomics strategy was performed to determine the diesel biodegradation process-associated intracellular biochemical changes in Rhodococcus sp. LH cells. With the aid of partial least squares-discriminant analysis (PLS-DA), 17 differential metabolites with variable importance in the projection (VIP) value greater than 1 were identified. Results indicated that the biodegradation of diesel oil by Rhodococcus sp. LH was affected by many different factors. Rhodococcus sp. LH could degrade diesel oil through terminal or sub-terminal oxidation reactions, and might also possess the ability to degrade aromatic hydrocarbons. In addition, some surfactants, especially fatty acids, which were secreted by Rhodococcus into medium could also assist the strain in dispersing and absorbing diesel oil. Lack of nitrogen in the seawater would lead to nitrogen starvation, thereby restraining the amino acid circulation in Rhodococcus sp. LH. Moreover, nitrogen starvation could also promote the conversation of relative excess carbon source to storage materials, such as 1-monolinoleoylglycerol. These results would provide a comprehensive understanding about the complex mechanisms of diesel oil biodegradation by Rhodococcus sp. LH at the systematic level.     

Ethyl tert-butyl ether (ETBE) biodegradation by a syntrophic association of Rhodococcus sp. IFP 2042 and Bradyrhizobium sp. IFP 2049 isolated from a polluted aquifer

Ethyl tert-butyl ether (ETBE) enrichment was obtained by adding contaminated groundwater to a mineral medium containing ETBE as the sole carbon and energy source. ETBE was completely degraded to biomass and CO₂ with a transient production of tert-butanol (TBA) and a final biomass yield of 0.37?±?0.08 mg biomass (dry weight).mg^?1 ETBE. Two bacterial strains, IFP 2042 and IFP 2049, were isolated from the enrichment, and their 16S rRNA genes (rrs) were similar to Rhodococcus sp. (99 % similarity to Rhodococcus erythropolis) and Bradyrhizobium sp. (99 % similarity to Bradyrhizobium japonicum), respectively. Rhodococcus sp. IFP 2042 degraded ETBE to TBA, and Bradyrhizobium sp. IFP 2049 degraded TBA to biomass and CO₂. A mixed culture of IFP 2042 and IFP 2049 degraded ETBE to CO₂ with a biomass yield similar to the original ETBE enrichment (0.31?±?0.02 mg?biomass.mg^?1 ETBE). Among the genes previously described to be involved in ETBE, MTBE, and TBA degradation, only alkB was detected in Rhodococcus sp. IFP 2042 by PCR, and none were detected in Bradyrhizobium sp. IFP 2049.     

Extracellular secretion of free fatty acids by the chrysophyte Ochromonas danica under photoautotrophic and mixotrophic growth

Recently, microalgae have gained a lot of attention because of their ability to produce fatty acids in their surrounding environments. The present paper describes the influence of organic carbon on the different fatty acid pools including esterified fatty acids, intracellular free fatty acids and extracellular free fatty acids in Ochromonas danica. It also throws light on the ability of O. danica to secrete free fatty acids in the growth medium under photoautotrophic and mixotrophic conditions. Biomass production of photoautotrophically grown O. danica was higher than that of mixotrophically grown, where a cellular biomass formation of 1.8 g L^?1 was observed under photoautotrophic condition which was about five folds higher than that under mixotrophic conditions. Contrary, the esterified fatty acid content reached up to 99 mg g^?1 CDW under photoautotrophic conditions at the late exponential phase, while during mixotrophic conditions a maximum of 212 mg g^?1 CDW was observed at the stationary phase. Furthermore, O. danica cells grown under mixotrophic conditions showed higher intracellular free fatty acid and extracellular free fatty acid contents (up to 51 and 20 mg g^?1 CDW, respectively) than cells grown under photoautotrophic conditions (up to 26 and 4 mg g^?1 CDW, respectively). The intra- and extracellular free fatty acids consisted of a high proportion of polyunsaturated fatty acids, mainly C18:2n?6, C18:3n?3 and C20:4n?6.     

Effects of initial population density (IPD) on growth and lipid composition of Nannochloropsis sp.

The microalga Nannochloropsis sp. was cultured under different initial population densities (IPDs) ranging from 0.11 to 9.09 g L^?1. The IPD affected the biomass and lipid accumulation significantly. The algal cultured with higher IPD resulted higher biomass concentration (up to 13.07 g L^?1) in 10 days growth. The biomass productivity with 0.98 g L^?1 IPD was 0.75 g L^?1 d^?1 which was higher than that of other IPDs. For IPDs ranging from 0.11 to 0.98 g L^?1, with the increase of IPD, the biomass productivity increased, while for IPD over 0.98 g L^?1, the biomass productivity decreased. Lipid content of the algal culture started with 0.11 g L^?1 IPD reached to 42 % of dry weight. But with the increase of IPD, the lipid content decreased. Lipid composition was analyzed using thin layer chromatography coupled with flame ionization detection (TLC/FID). Seven lipid classes were identified and quantified. The main reserve lipid, triacylglyceride (TAG), accumulated under all different IPD conditions. However, with the increasing IPD values, TAG content decreased from 59.1 to 23.5 % of the total lipids. Based on these results, to obtain the maximal biomass productivity and lipid productivity of Nannochloropsis sp. in mass cultivation systems, it is necessary to select an appropriate IPD.     

<Emphasis Type="Italic">Rhodococcus</Emphasis> bacteria as a promising source of oils from olive mill wastes

The accumulation of triacylglycerols (TAG) is a common feature among actinobacteria belonging to Rhodococcus genus. Some rhodococcal species are able to produce significant amounts of those lipids from different single substrates, such as glucose, gluconate or hexadecane. In this study we analyzed the ability of different species to produce lipids from olive oil mill wastes (OMW), and the possibility to enhance lipid production by genetic engineering. OMW base medium prepared from alperujo, which exhibited high values of chemical oxygen demand (127,000 mg/l) and C/N ratio (508), supported good growth and TAG production by some rhodococci. R. opacus, R. wratislaviensis and R. jostii were more efficient at producing cell biomass (2.2–2.7 g/l) and lipids (77–83% of CDW, 1.8–2.2 g/l) from OMW than R. fascians, R. erythropolis and R. equi (1.1–1.6 g/l of cell biomass and 7.1–14.0% of CDW, 0.1–0.2 g/l of lipids). Overexpression of a gene coding for a fatty acid importer in R. jostii RHA1 promoted an increase of 2.2 fold of cellular biomass value with a concomitant increase in lipids production during cultivation of cells in OMW. This study demonstrates that the bioconversion of OMW to microbial lipids is feasible using more robust rhodococal strains. The efficiency of this bioconversion can be significantly enhanced by engineering strategies.     

Polyhydroxyalkanoate biosynthesis and simultaneous remotion of organic inhibitors from sugarcane bagasse hydrolysate by Burkholderia sp.

Burkholderia sp. F24, originally isolated from soil, was capable of growth on xylose and removed organic inhibitors present in a hemicellulosic hydrolysate and simultaneously produced poly-3-hydroxybutyrate (P3HB). Using non-detoxified hydrolysate, Burkholderia sp. F24 reached a cell dry weight (CDW) of 6.8 g L^?1, containing 48 % of P3HB and exhibited a volumetric productivity (P_P3HB) of 0.10 g L^?1 h^?1. Poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (P3HB-co-3HV) were produced using xylose and levulinic acid (LA) as carbon sources. In shake flask cultures, the 3HV content in the copolymer increased from 9 to 43 mol% by adding LA from 1.0 to 5.0 g L^?1. In high cell density cultivation using concentrated hemicellulosic hydrolysate F24 reached 25.04 g L^?1 of CDW containing 49 % of P3HB and P_P3HB of 0.28 g L^?1 h^?1. Based on these findings, second-generation ethanol and bioplastics from sugarcane bagasse is proposed.     

The atf2 gene is involved in triacylglycerol biosynthesis and accumulation in the oleaginous Rhodococcus opacus PD630

Rhodococcus opacus PD630 is an oleaginous bacterium able to accumulate large amounts of triacylglycerols (TAG) in different carbon sources. The last reaction for TAG biosynthesis is catalyzed by the bifunctional wax ester synthase/acyl-CoA:diacylglycerol acyltransferase (WS/DGAT) enzymes encoded by atf genes. R. opacus PD630 possesses at least 17 putative atf homologous genes in its genome, but only atf1 and atf2 exhibited a significant DGAT activity when expressed in E. coli, as revealed in a previous study. The contribution of atf1 gene to TAG accumulation by strain PD630 has been demonstrated previously, although additional Atfs may also contribute to lipid accumulation, since the atf1-disrupted mutant is still able to produce significant amounts of TAG (Alvarez et al., Microbiology 154:2327–2335, 2008). In this study, we investigated the in vivo role of atf2 gene in TAG accumulation by R. opacus PD630 by using different genetic strategies. The atf2-disrupted mutant exhibited a decrease in TAG accumulation (up to 25–30 %, w/w) and an approximately tenfold increase in glycogen formation in comparison with the wild-type strain. Surprisingly, in contrast to single mutants, a double mutant generated by the disruption of atf1 and atf2 genes only showed a very low effect in TAG and in glycogen accumulation under lipid storage conditions. Overexpression of atf1 and atf2 genes in strain PD630 promoted an increase of approximately 10 % (w/w) in TAG accumulation, while heterologous expression of atf2 gene in Mycobacterium smegmatis caused an increase in TAG accumulation during cultivation in nitrogen-rich media. This study demonstrated that, in addition to atf1 gene, atf2 is actively involved in TAG accumulation by the oleaginous R. opacus PD630.     

Genome sequence of Sphingomonas sp. S17, isolated from an alkaline, hyperarsenic, and hypersaline volcano-associated lake at high altitude in the Argentinean Puna

The high-altitude Andean lakes (HAAL) in the Argentinean Puna-high Andes region represent an almost unexplored ecosystem exposed to extreme conditions (high UV irradiation, hypersalinity, drastic temperature changes, desiccation, and high pH). Here we present the first genome sequence, a Sphingomonas sp., isolated from this extreme environment.