Distribution of glyphosate and methylphosphonate catabolism systems in soil bacteria <Emphasis Type="Italic">Ochrobactrum anthropi</Emphasis> and <Emphasis Type="Italic">Achromobacter</Emphasis> sp

Bacterial strains capable of utilizing methylphosphonic acid (MP) or glyphosate (GP) as the sole sources of phosphorus were isolated from soils contaminated with these organophosphonates. The strains isolated from MP-contaminated soils grew on MP and failed to grow on GP. One group of the isolates from GP-contaminated soils grew only on MP, while the other one grew on MP and GP. Strains Achromobacter sp. MPS 12 (VKM B-2694), MP degraders group, and Ochrobactrum anthropi GPK 3 (VKM B-2554D), GP degraders group, demonstrated the best degradative capabilities towards MP and GP, respectively, and were studied for the distribution of their organophosphonate catabolism systems. In Achromobacter sp. MPS 12, degradation of MP was catalyzed by C–P lyase incapable of degrading GP (C–P lyase I). Adaptation to growth on GP yielded the strain Achromobacter sp. MPS 12A, which retained its ability to degrade MP via C–P lyase I and was capable of degrading GP with formation of sarcosine, thus suggesting the involvement of a GP-specific C–P lyase II. O. anthropi GPK 3 also degraded MP via C–P lyase I, but degradation of GP in it was initiated by glyphosate oxidoreductase, which was followed by product transformation via the phosphonatase pathway.     

Analysis of the Anaerobic Microbial Community Capable of Degrading p-Toluene Sulfonate

Three strains of Clostridium sp., 14 (VKM B-2201), 42 (VKM B-2202), and 21 (VKM B-2279), two methanogens, Methanobacterium formicicum MH (VKM B-2198) and Methanosarcina mazei MM (VKM B-2199), and one sulfate-reducing bacterium, Desulfovibrio sp. SR1 (VKM B-2200), were isolated in pure cultures from an anaerobic microbial community capable of degrading p-toluene sulfonate. Strain 14 was able to degrade p-toluene sulfonate in the presence of yeast extract and bactotryptone and, like strain 42, to utilize p-toluene sulfonate as the sole sulfur source with the production of toluene. p-Toluene sulfonate stimulated the growth of Ms. mazei MM on acetate. The sulfate-reducing strain Desulfovibrio sp. SR1 utilized p-toluene sulfonate as an electron acceptor. The putative scheme of p-toluene sulfonate degradation by the anaerobic microbial community is discussed.     

Carbohydrate-containing cell wall polymers of some strains of the <Emphasis Type="Italic">Bacillus subtilis</Emphasis> group

A comparative study of the structures of carbohydrate-containing cell wall polymers isolated from the strains of the Bacillus subtilis group was performed by means of chemical and NMR spectroscopic meth ods. Polymers of different structure were revealed, namely, 1,3-poly(glycerol phosphates) with β-glucopyranose in Bacillus subtilis strains VKM B-520, VKM B-723, and VKM B-763 (= VKM B-911); 1,5-poly(ribitol phosphate) with α-glucopyranose in B. subtilis strains VKM B-722 and VKM B-922 (the structure is reported for the first time); and simultaneously two polymers in B. subtilis VKM B-761, 1,5-poly(ribitol phosphate) with β-glucopyranose and the disaccharide 1-phosphate polymer with the following repeating unit: -6)-α-D-Galp-(1-P-4)-gB-D-GlcpNAc-(1-, in which the hydroxyls at C3 and C6 of glucosamine residues are partially O-acetylated (the structure is reported for the first time). Heterogeneity of the B. subtilis group is con firmed by variations in the structure and composition of the cell wall polymers. The cell surface polymers are useful for discrimination of closely related bacilli strains and are cell wall marker components that may be an indispensable element of the Bacillus subtilis group taxonomy along with the genomosystematic methods.     

Bacillus aryabhattai FACU: A promising bacterial strain capable of manipulate the glyphosate herbicide residues

Glyphosate is a commonly used organophosphate herbicide that has an adverse impact on humans, mammals and soil microbial ecosystems. The redundant utilize of glyphosate to control weed growth cause the pollution of the soil environment by this chemical. The discharge of glyphosate in the agricultural drainage can also cause serious environmental damage and water pollution problems. Therefore, it is important to develop methods for enhancing glyphosate degradation in the soil through bioremediation. In this study, thirty bacterial isolates were selected from an agro-industrial zone located in Sadat City of Monufia Governorate, Egypt. The isolates were able to grow in LB medium supplemented with 7.2 mg/ml glyphosate. Ten isolates only had the ability to grow in a medium containing different concentrations of glyphosate (50, 100, 150, 200 and 250 mg/ml). The FACU3 bacterial isolate showed the highest CFU in the different concentrations of glyphosate. The FACU3 isolate was Gram-positive, spore-forming and rod-shape bacteria. Based on API 50 CHB/E medium kit, biochemical properties and 16S rRNA gene sequencing, the FACU3 isolate was identified as Bacillus aryabhattai. Different bioinformatics tools, including multiple sequence alignment (MSA), basic local alignment search tool (BLAST) and primer alignment, were used to design specific primers for goxB gene amplification and isolation. The goxB gene encodes FAD-dependent glyphosate oxidase enzyme that responsible for biodegradation process. The selected primers were successfully used to amplify the goxB gene from Bacillus aryabhattai FACU3. The results indicated that the Bacillus aryabhattai FACU3 can be utilized in glyphosate-contaminated environments for bioremediation. According to our knowledge, this is the first time to isolate of FAD-dependent glyphosate oxidase (goxB) gene from Bacillus aryabhattai.     

News & Notes: Bioremediation of Crude Oil Contamination with Acinetobacter sp. A3

Acinetobacter sp. A3 is able to extensively degrade Bombay High Crude Oil (BHCO) and utilize it as the sole source of carbon. A total degradation of 70% BHCO was noted by the end of 120 h of growth of Acinetobacter sp. A3 under shake flask condition, 60% of which was due to biodegradation. In crude oil-contaminated soil (5%) amended with Acinetobacter sp. A3, there was both an increase in colony-forming units (CFU) and crude oil degradation. This is in contrast to a decrease in CFU of the indigenous microorganisms and lower degradation in unamended soil within the same 30-day period. Also, Acinetobacter sp. A3-treated soil permitted better germination of Mung beans (Phaseolus aureus) and growth as evidenced by better length and weight of the plants and chlorophyll content of its leaves, which was attributed to the reduction in phytotoxicity of the crude oil owing to its degradation. This crude oil degradative capability of Acinetobacter sp. A3 could be exploited for bioremediation purposes. Received: 16 December 1996 / Accepted: 10 February 1997     

Two Phosphate- and Potassium-solubilizing Bacteria Isolated from Tianmu Mountain, Zhejiang, China

Summary Two phosphate- and potassium-solubilizing strains (KNP413 and KNP414) were isolated from the soil of Tianmu Mountain, Zhejiang Province (China) and they were phenotypically and phylogenetically characterized. Both isolates effectively dissolved mineral phosphate and potassium, while strain KNP414 showed higher dissolution capacity even than Bacillus mucilaginosus AS1.153, the inoculant of potassium fertilizer widely used in China. When grown on Aleksandrov medium, both strains were rod-shaped spore-formers with a large capsule, and they formed slimy and translucent colonies. The DNA G+C contents were 57.7 mol% for strain KNP413 and 56.1 mol% for strain KNP414. Strain KNP413 shared a 16S rRNA gene sequence similarity of more than 99.1% with strain KNP414 and Bacillus mucilaginosus strains HSCC 1605 and YNUC0001, and a 94.6% similarity with Bacillus mucilaginosus VKM B-1480D, the type strain of Bacillus mucilaginosus. Strains KNP413 and KNP414 together with other Bacillus mucilaginosus were clustered with Paenibacillus strains in a group. The use of a specific PCR primer PAEN515F designed for differentiating the genus Paenibacillus from other members of the Bacillaceae showed that strains KNP413 and KNP414 had the same amplified 16S rRNA gene fragment (0.9-kb) as members of the genus Paenibacillus. In conclusion, phosphate- and potassium-solubilizing strains KNP413 and KNP414 should be integrated into the same species different from strain VKM B-1480D and they might be transferred to the genus of Paenibacillus, i.e. Paenibacillus mucilaginosus.The GenBank accession numbers of the 16S rRNA gene sequences are AY646227 for KNP413 and AY646228 for KNP414.     

Biodegradation of trinitrotoluene (TNT) by indigenous microorganisms from TNT-contaminated soil,and their application in TNT bioremediation

Soil and groundwater contaminated by munitions compounds is a crucial issue in environmental protection. Trinitrotoluene (TNT) is highly toxic and carcinogenic; therefore, the control and remediation of TNT contamination is a critical environmental issue. In this study, the authors characterized the indigenous microbial isolates from a TNT-contaminated site and evaluated their activity in TNT biodegradation. The bacteria Achromobacter sp. BC09 and Citrobacter sp. YC4 isolated from TNT-contaminated soil by enrichment culture with TNT as the sole carbon and nitrogen source (strain BC09) and as the sole nitrogen but not carbon source (strain YC4) were studied for their use in TNT bioremediation. The efficacy of degradation of TNT by indigenous microorganisms in contaminated soil without any modification was insufficient in the laboratory-scale pilot experiments. The addition of strains BC09 and YC4 to the contaminated soil did not significantly accelerate the degradation rate. However, the addition of an additional carbon source (e.g., 0.25% sucrose) could significantly increase the bioremediation efficiency (ca. decrease of 200 ppm for 10 days). Overall, the results suggested that biostimulation was more efficient as compared with bioaugmentation. Nevertheless, the combination of biostimulation and bioaugmentation using these indigenous isolates is still a feasible approach for the development of bioremediation of TNT pollution.     

抗草甘膦酵母菌ZM-1的分离鉴定及其生长降解特性

以福州市郊区的耕作土壤为研究材料, 利用草甘膦为选择压力, 通过富集、驯化培养, 分离出一株对草甘膦具有高耐受和降解作用的酵母菌菌株ZM-1, 结合生理生化特征及26S rDNA D1/D2区序列分析将其初步鉴定为胶红酵母菌(Rhodotorula mucilaginosa)。菌株ZM-1能以草甘膦为唯一碳、氮源生长, 对草甘膦的最高耐受浓度为50 g/L。在草甘膦初始浓度为1 g/L的无机盐培养基中, 30°C、150 r/min 摇床振荡培养7 d, 草甘膦降解率为85.38%。适合菌株ZM-1生长及降解草甘膦的最佳条件为: 草甘膦初始浓度1 g/L, 接种量4%, 温度30°C, pH 值5.5-6.0, 装料量50 mL/250 mL。菌株ZM-1是一株良好的草甘膦耐受菌, 可用于草甘膦污染环境的生物修复, 也可能成为转基因抗草甘膦作物的一个很好资源。     

Analysis of the anaerobic microbial community capable of degrading p-toluene sulphonate

Three strains of Clostridium sp., 14 (VKM B-2201), 42 (VKM B-2202), and 21 (VKM B-2279), two methanogens, Methanobacterium formicicum MH (VKM B-2198) and Methanosarcina mazei MM (VKM B-2199), and one sulfate-reducing bacterium, Desulfovibrio sp. SR1 (VKM B-2200), were isolated in pure cultures from an anaerobic microbial community capable of degrading p-toluene sulfonate. Strain 14 was able to degrade p-toluene sulfonate in the presence of yeast extract and bactotryptone and, like strain 42, to utilize p-toluene sulfonate as the sole sulfur source with the production of toluene. p-Toluene sulfonate stimulated the growth of Ms. mazei MM on acetate. The sulfate-reducing strain Desulfovibrio sp. SR1 utilized p-toluene sulfonate as an electron acceptor. The putative scheme of p-toluene sulfonate degradation by the anaerobic microbial community is discussed.     

Cell wall teichoic acids of Bacillus licheniformis VKM B-511T, Bacillus pumilus VKM B-508T, and other strains previously assigned to Bacillus pumilus

The teichoic acids (TAs) of type strains, viz. Bacillus licheniformis VKM B-511^T and Bacillus pumilus VKM B-508^T, as well as phylogenetically close bacteria VKM B-424, VKM B-1554, and VKM B-711 previously assigned to Bacillus pumilus on the basis of morphological, physiological, and biochemical properties, were investigated. Three polymers were found in the cell wall of each of the 5 strains under study. Strains VKM B-508^T, VKM B-424, and VKM B-1554 contained polymers of the same core: unsubstituted 1,3-poly(glycerol phosphate) (TA I) and 1,3-poly(glycerol phosphate) with O-D-Ala and N-acetyl-??-D-glucosamine substituents (TA II and TA III??, respectively). The cell walls of two remaining strains contained TA I, TA II, and a poly(glycosylpolyol phosphate) with the following structure of repeating units: -6)-??-D-GlcpNAc(1??1)-snGro-(3-P-(TA III?) in ??Bacillus pumilus?? VKM B-711 (100% 16S rRNA gene similarity with the type strain of Bacillus safensis) and -6)-??-D-Galp-(1??2)-snGro-(3-P-(TA III?) in Bacillus licheniformis VKM B-511^T. The simultaneous presence of three different TAs in the cell walls was confirmed by the NMR spectroscopic DOSY methods. The structure of the polymers and localization of O-D-Ala residues were investigated by the chemical and NMR spectroscopic methods.     

Teichoic acids of three type strains of the Bacillus subtilis group, Bacillus mojavensis VKM B-2650, Bacillus amyloliquefaciens subsp. amyloliquefaciens VKM B-2582, and Bacillus sonorensis VKM B-2652

Cell walls of three type strains of the Bacillus subtilis group, Bacillus mojavensis VKM B-2650, Bacillus amyloliquefaciens subsp. amyloliquefaciens VKM B-2582, and Bacillus sonorensis VKM B-2652, are characterized by the individual set of teichoic acids. All strains contained 1,3-poly(glycerol phosphates), unsubstituted, acylated with D-alanine, and glycosylated. The latter differ in the nature of the monosaccharide residue. Teichoic acids of B. mojavensis VKM B-2650^T and B. amyloliquefaciens subsp. amyloliquefaciens VKM B-2582^T contained α-glucopyranose, while those of B. sonorensis VKM B-2652^T contained β-glucopyranose and N-acetyl-α-D-glucosamine. Moreover, cell walls of B. mojavensis VKM B-2650^T contained a teichoic acid of poly(glycosylglycerol phosphate) nature with the following structure of the repeating unit: -4)-α-D-α-D-GlcpNAc-(1 → 3)]-Glcp-(1 → 2)-sn-Gro-(3-P-. The type strains have been characterized according to the composition of cell wall sugars and polyols. Application of teichoic acids (set and structure) as chemotaxonomic characteristics is discussed for six type strains of the Bacillus subtilis group. Polymer structures were determined by chemical and NMR spectroscopic techniques.     

Optimization of liquid-state fermentation conditions for the glyphosate degradation enzyme production of strain Aspergillus oryzae by ultraviolet mutagenesis

This study aimed to obtain strains with high glyphosate-degrading ability and improve the ability of glyphosate degradation enzyme by the optimization of fermentation conditions. Spore from Aspergillus oryzae A-F02 was subjected to ultraviolet mutagenesis. Single-factor experiment and response surface methodology were used to optimize glyphosate degradation enzyme production from mutant strain by liquid-state fermentation. Four mutant strains were obtained and named as FUJX 001, FUJX 002, FUJX 003, and FUJX 004, in which FUJX 001 gave the highest total enzyme activity. Starch concentration at 0.56%, GP concentration at 1,370?mg/l, initial pH at 6.8, and temperature at 30°C were the optimum conditions for the improved glyphosate degradation endoenzyme production of A. oryzae FUJX 001. Under these conditions, the experimental endoenzyme activity was 784.15?U/100?ml fermentation liquor. The result (784.15?U/100?ml fermentation liquor) was approximately 14-fold higher than that of the original strain. The result highlights the potential of glyphosate degradation enzyme to degrade glyphosate.     

Disaccharide 1-phosphate polymers of some representatives of the Bacillus subtilis group

Disaccharide 1-phosphate polymers as well as teichoic acids of various structures have been found in the cell walls of the representatives of the Bacillus subtilis group, namely Bacillus subtilis subsp. spizizenii VKM B-720 and VKM B-916, B. subtilis VKM B-517, and Bacillus vallismortis VKM B-2653^T. Disaccharide 1-phosphate polymers are composed of repeating units of the following structure: -P-4)-β-D-GlcpNAc-(1→6)-α-D-Galp-(1-, the N-acetylglucosamine residues are partially acetylated at positions O3 and O6 (VKM B-720 and VKM B-916); -P-4)-β-D-Glcp-(1→6)-α-D-GlcpNAc-(1-, the glucopyranose residues are partially acetylated at positions O2 or O3 (VKM B-517); -P-6)-α-D-GlcpNH ₃ ⁺ /α-D-GlcpNAc-(1→2)-α-D-Glcp-(1-, the N-acetylglucosamine residues are partially deacetylated (VKM B-2653^T). The structures of the two last disaccharide 1-phosphate polymers have not been reported so far for Gram-positive bacteria. The teichoic acids in the studied strains are O-D-alanyl-1,5-poly(ribitol phosphates) substituted with β-D-glucopyranose (VKM B-517, VKM B-720, VKM B-916) or 2-acetamido-2-deoxy-β-D-glucopyranose (VKM B-2653^T). The structures of the phosphate-containing polymers have been studied by chemical methods and by NMR spectroscopy.     

Impacts of gene bioaugmentation with pJP4-harboring bacteria of 2,4-D-contaminated soil slurry on the indigenous microbial community

Gene bioaugmentation is a bioremediation strategy that enhances biodegradative potential via dissemination of degradative genes from introduced microorganisms to indigenous microorganisms. Bioremediation experiments using 2,4-dichlorophenoxyacetic acid (2,4-D)-contaminated soil slurry and strains of Pseudomonas putida or Escherichia coli harboring a self-transmissible 2,4-D degradative plasmid pJP4 were conducted in microcosms to assess possible effects of gene bioaugmentation on the overall microbial community structure and ecological functions (carbon source utilization and nitrogen transformation potentials). Although exogenous bacteria decreased rapidly, 2,4-D degradation was stimulated in bioaugmented microcosms, possibly because of the occurrence of transconjugants by the transfer of pJP4. Terminal restriction fragment length polymorphism analysis revealed that, although the bacterial community structure was disturbed immediately after introducing exogenous bacteria to the inoculated microcosms, it gradually approached that of the uninoculated microcosms. Biolog assay, nitrate reduction assay, and monitoring of the amoA gene of ammonia-oxidizing bacteria and nirK and nirS genes of denitrifying bacteria showed no irretrievable depressive effects of gene bioaugmentation on the carbon source utilization and nitrogen transformation potentials. These results may suggest that gene bioaugmentation with P. putida and E. coli strains harboring pJP4 is effective for the degradation of 2,4-D in soil without large impacts on the indigenous microbial community.     

Bioremediation via In Situ Electrotransformation

Bioremediation of polluted sites relies on bacteria to degrade or transform contaminants into less noxious chemicals. To do so, bacteria require genes that encode the degradation enzymes and the capacity to properly express them, which may be lacking in indigenous bacteria. To increase the ability of indigenous bacteria to bioremediate a contaminated site, this research proposes the use of electrotransformation to facilitate bacterial uptake of exogenous degradation genes. As a proof of concept, a lindane degradation gene (linA) located on a broad host-spectrum expression plasmid (pBLN) was introduced into soil bacteria by electroporation both in vitro, in liquid media, and in situ, in soil. In both cases, the electrotransformed bacteria displayed an increase in lindane degradation and an increase in the linA gene copy number. The use of in situ electrotransformation could improve pollutant degradation rates and could provide another tool for bioremediation.     

Glyphosate bioavailability in soil

Biodegradation of glyphosate in sod-podzol soil by both the indigenous micro flora and the introduced strain Ochrobactrum anthropi GPK 3 was studied with respect to its sorption and mobility. The experiments were carried out in columns simulating the vertical soil profile. Soil samples studied were taken from soil horizons 0–10, 10–20, and 20–30 cm deep. It was found out that the most of the herbicide (up to 84%) was adsorbed by soil during the first 24 h; the rest (16%) remained in the soluble fraction. The adsorbed glyphosate was completely extractable by alkali. No irreversible binding of glyphosate was observed. By the end of the experiment (21st day), glyphosate was only found in extractable fractions. The comparison of the effect of the introduced O. anthropi GPK 3 and indigenous microbial community on the total toxicant content (both soluble and absorbed) in the upper 10 cm soil layer showed its reduction by 42% (21 mg/kg soil) and 10–12% (5 mg/kg soil), respectively. Simultaneously, 14–18% glyphosate moved to a lower 10–20 cm layer. Watering (that simulated rainfall) resulted in a 20% increase of its content at this depth; 6–8% of herbicide was further washed down to the 20–30 cm layer. The glyphosate mobility down the soil profile reduced its density in the upper layer, where it was available for biodegradation, and resulted in its concentration in lower horizons characterized by the absence (or low level) of biodegradative processes. It was shown for the first time how the herbicide biodegradation in soil can be increased manifold by introduction of the selected strain O. anthropi GPK 3.     

Restoration of a Mediterranean forest after a fire: bioremediation and rhizoremediation field‐scale trial

Forest fires pose a serious threat to countries in the Mediterranean basin, often razing large areas of land each year. After fires, soils are more likely to erode and resilience is inhibited in part by the toxic aromatic hydrocarbons produced during the combustion of cellulose and lignins. In this study, we explored the use of bioremediation and rhizoremediation techniques for soil restoration in a field‐scale trial in a protected Mediterranean ecosystem after a controlled fire. Our bioremediation strategy combined the use of Pseudomonas putida strains, indigenous culturable microbes and annual grasses. After 8 months of monitoring soil quality parameters, including the removal of monoaromatic and polycyclic aromatic hydrocarbons as well as vegetation cover, we found that the site had returned to pre‐fire status. Microbial population analysis revealed that fires induced changes in the indigenous microbiota and that rhizoremediation favours the recovery of soil microbiota in time. The results obtained in this study indicate that the rhizoremediation strategy could be presented as a viable and cost‐effective alternative for the treatment of ecosystems affected by fires.     

Heterogeneous set of cell wall teichoic acids in strains of <Emphasis Type="Italic">Bacillus subtilis</Emphasis> VKM B-760 and VKM B-764

Cell walls of Bacillus subtilis VKM B-760 and VKM B-764 are characterized by heterogeneous composition of teichoic acids. Polymer I with structure -6)-β-D-Galp-(1→1)-sn-Gro-(3-P-, polymer II with structure -6)-α-D-Glcp-(1→1)-sn-Gro-(3-P-, and a small amount of unsubstituted 1,3-poly(glycerol phosphate) were detected in strain VKM B-760. Strain VKM B-764 contains an analogous set of teichoic acids, but a characteristic feature of polymer II is the presence of disubstituted glycerol residue with α-glucopyranose localization in the integral chain at C-1 hydroxyl and β-glucopyranose as a side branch at C-2 hydroxyl (polymer III): -6)-α-D-Glcp-(1→1)-[β-D-Glcp-(1→2)]-sn-Gro-(3-P-. The structures of polymer I in bacilli and polymer III in Gram-positive bacteria are described for the first time. Teichoic acids were studied by chemical methods and on the basis of combined analysis of one-dimensional ¹H-, ¹³C-, and ³¹P-NMR spectra, homonuclear two-dimensional ¹H/¹H COSY, TOCSY, and ROESY, and heteronuclear two-dimensional ¹H/¹³C gHSQC- and HMQC-TOCSY experiments. Simultaneous presence of several different structure teichoic acids in the bacillus cell walls as well as chemotaxonomical perspectives of the application of these polymers as species-specific markers for members of the Bacillus genus is discussed.     

Development of thermotolerant bacterial consortium,the basis for biopreparation for remediation of petroleum-contaminated soils and waters in hot climates

The consortium of thermotolerant petroleum-oxidizing bacteria containing strains Gordonia sp. 1D VKM Ac-2720 D, Rhodococcus sp. Par7 VKM Ac-2722 D, and R. pyridinivorans L5A-BSU VKM Ac-2721 for destruction of oil and oil products in hot climates was developed for the first time. The consortium was effective in soils and liquid media at temperature as high as 50°C, at salinity up to 7%, and soil moisture of about 10%. The efficiency of petroleum destruction for 21 days was 70 and 59% at 24 and 45°C, respectively. The consortium of thermotolerant petroleum-destructing strains could be used as basis for the biopreparation for remediation of petroleum-contaminated soils and waters in hot climates.     

Bacterial Community Dynamics during Bioremediation of Diesel Oil-Contaminated Antarctic Soil

The effect of nutrient and inocula amendment in a bioremediation field trial using a nutrient-poor Antarctic soil chronically contaminated with hydrocarbons was tested. The analysis of the effects that the treatments caused in bacterial numbers and hydrocarbon removal was combined with the elucidation of the changes occurring on the bacterial community, by 16S rDNA-based terminal restriction fragment length polymorphism (T-RFLP) typing, and the detection of some of the genes involved in the catabolism of hydrocarbons. All treatments caused a significant increase in the number of bacteria able to grow on hydrocarbons and a significant decrease in the soil hydrocarbon content, as compared to the control. However, there were no significant differences between treatments. Comparison of the soil T-RFLP profiles indicated that there were changes in the structure and composition of bacterial communities during the bioremediation trial, although the communities in treated plots were highly similar irrespective of the treatment applied, and they had a similar temporal dynamics. These results showed that nutrient addition was the main factor contributing to the outcome of the bioremediation experiment. This was supported by the lack of evidence of the establishment of inoculated consortia in soils, since their characteristic electrophoretic peaks were only detectable in soil profiles at the beginning of the experiment. Genetic potential for naphthalene degradation, evidenced by detection of nahAc gene, was observed in all soil plots including the control. In treated plots, an increase in the detection of catechol degradation genes (nahH and catA) and in a key gene of denitrification (nosZ) was observed as well. These results indicate that treatments favored the degradation of aromatic hydrocarbons and probably stimulated denitrification, at least transiently. This mesocosm study shows that recovery of chronically contaminated Antarctic soils can be successfully accelerated using biostimulation with nutrients, and that this causes a change in the indigenous bacterial communities and in the genetic potential for hydrocarbon degradation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.