Basis Of 16S rDNA Sequences Research Articles

Occurrence of lignin degradation genotypes and phenotypes among prokaryotes.

A number of prokaryotes actively contribute to lignin degradation in nature and their activity could be of interest for many applications including the production of biogas/biofuel from lignocellulosic biomass and biopulping. This review compares the reliability and efficiency of the culture-dependent screening methods currently used for the isolation of ligninolytic prokaryotes. Isolated prokaryotes exhibiting lignin-degrading potential are presented according to their phylogenetic groups. With the development of bioinformatics, culture-independent techniques are emerging that allow larger-scale data mining for ligninolytic prokaryotic functions but today, these techniques still have some limits. In this work, two phylogenetic affiliations of isolated prokaryotes exhibiting ligninolytic potential and laccase-encoding prokaryotes were determined on the basis of 16S rDNA sequences, providing a comparative view of results obtained by the two types of screening techniques. The combination of laboratory culture and bioinformatics approaches is a promising way to explore lignin-degrading prokaryotes.

In vitro Phosphate Solubilization by Bacillus sp. NPSBS 3.2.2 Obtained from the Cotton Plant Rhizosphere

Cotton is one of the important cash crops of India. Apart from being an important source of fibres, cotton seeds also form an important source of edible oil. A lot of Phosphatic fertilizers are used to during cotton cultivation but a major portion of this Phosphate gets converted into insoluble form which is not available to the plants. However, there are certain Phosphate Solubilizing Bacteria which can solubilize inorganic insoluble phosphorous to inorganic soluble form and this form of phosphate can be easily used by plants. In present study isolation of Phosphate Solubilizing Bacteria was carried out from rhizosphere soil sample of cotton plants growing in various villages of District Mahendergarh, Haryana. A total of 15 bacterial isolates were obtained which were subjected to primary and secondary screening. On the basis of secondary screening NPSBS3.2.2 was found to solubilize the maximum amount of Phosphorous (0.129¼g/ml). The isolate was grown in different conditions and it was found that sucrose was the most suitable Carbon source at pH 7 at the incubation time period of 96 hours. The isolate was characterized morphologically, biochemically and on the basis of 16s rDNA sequencing (Genebank Accession Number- KF974682) and was found to be a member of the genus Bacillus.

Campylobacter coli cultured from the stools of a patient with immunoproliferative small intestinal disease

Campylobacter has been associated with immunoproliferative small intestinal disease (IPSID), on the basis of 16S rDNA sequencing, in situ hybridization, and immunohistochemistry. Here, for the first time, we have cultured Campylobacter from the stools of a patient with IPSID. Phenotypic analysis and whole genome sequencing identified Campylobacter coli. PCR on a IPSID tissue biopsy sample was positive for Campylobacter coli and negative for Campylobacter jejuni. These findings further support a causative role for Campylobacter in the development of IPSID.

Purification and characterization of antifungal phenazines from a fluorescent Pseudomonas strain FPO4 against medically important fungi

The strain FPO4 was isolated from the rhizoplane of rice plant root and identified as a fluorescent Pseudomonas aeruginosa on the basis of 16S rDNA sequences and BLAST analysis. The extracellular metabolites produced by this strain were purified by silica gel column chromatography and isolated four pure compounds. Based on the spectral data the four compounds were identified as phenazin-1-ol, phenazine-1-carboxylic acid (PCA), 2-heptyl-3-hydroxyl-4(1H)-quinolone (PQS), and phenazine-1-carboxamide (PCN), respectively. Phenazin-1-ol and PCA were active against all the eight fungi tested. The highest activity of 4 μg/mL by PCA was recorded against Trichophyton rubrum, a human pathogen responsible for causing athlete's foot, jock itch, ringworm and fingernail fungus infections, followed by Candida albicans and Candida tropicalis. The activity of phenazin-1-ol, PCA against Candida spp. was found to be better than the standard antifungal agent amphotericin B. Furthermore, the present study reports the antimicrobial activity of the purified phenazines on major human pathogen, T. rubrum for the first time.

Bacterial Decolorization of Textile Azo Dye Acid Orange by Staphylococcus hominis RMLRT03.

A bacterial strain RMLRT03 with ability to decolorize textile dye Acid Orange dye was isolated from textile effluent contaminated soil of Tanda, Ambedkar Nagar, Uttar Pradesh (India). The decolorization studies were performed in Bushnell and Haas medium (BHM) amended with Acid Orange dye. The bacterial strain was identified as Staphylococcus hominis on the basis of 16S rDNA sequence. The bacterial strain exhibited good decolorization ability with glucose and yeast extract supplementation as cosubstrate in static conditions. The optimal condition for the decolorization of Acid Orange dye by Staphylococcus hominis RMLRT03 strain were at pH 7.0 and 35°C in 60 h of incubation. The bacterial strain could tolerate high concentrations of Acid Orange dye up to 600 mg l-1. The high decolorizing activity under natural environmental conditions indicates that the bacterial strain has practical application in the treatment of dye containing wastewaters.

Utilization of endophytic strain Bacillus sp. SBER3 for biodegradation of polyaromatic hydrocarbons (PAH) in soil model system

Total eight endophytic bacteria were isolated from the roots of Populus deltoides growing in non-contaminated sites at natural vegetation of Garhwal Himalayas, Uttarakhand, India. Among these eight, only SBER3 isolate was able to metabolize wide range of polyaromatic hydrocarbons (PAH) and other hydrocarbon used in the study i.e. anthracene, naphthalene, benzene, toluene and xylene on minimal salt basal medium (MSB) as sole source of carbon and energy. It was identified as Bacillus sp. on the basis of 16S rDNA sequence. Furthermore, quantitatively Bacillus sp. SBER3 was able to produced 22 μg ml−1 of IAA after 4 days and solubilized 0.96 μg ml−1 of available phosphorus respectively after 120 h. In addition, Bacillus sp. SBER3 also produced siderophore and 1 aminocyclopropane-1-carboxylate (ACC) deaminase. Along with these traits, SBER3 under in vitro condition inhibited the phytopathogenic fungi Rhizoctonia solani, Macrophomina phaseolina, Fusarium oxysporum and Fusarium solani with (percent growth inhibition) PGI of 60%, 61.5%, 64.3% and 12%, respectively. Microscopic examination under the influence of Bacillus sp. SBER3 revealed abnormalities of mycelia structure in case of R. solani, F. oxysporum and M. phaseolina. Although, mean growth rate and survival under varying osmotic stress regime were also evaluated under in vitro condition. Interestingly, in liquid culture medium Bacillus sp. SBER3 reduced appreciable amount i.e. 83.4% and 75.1% of anthracene and naphthalene, respectively after 6 days of incubation. Notwithstandingly, isolate SBER3 proved to be a competent rhizobacteria in rhizosphere niche in treatments T1 (Sterile soil + plant cuttings + bacterization) and T2 (sterile soil + anthracene + plant cuttings + bacterization). Rhizoremediation potential of Bacillus sp. SBER3 was demonstrated in polyaromatic hydrocarbon contaminated soil model system. Significant enhancement in shoot, root length, root and shoot biomass including stem girth of P. deltoides with respective to control was also recorded and concurrently endophytic isolate Bacillus sp. SBER3 degraded 45.6% of PAH in soil model system after 120 days as determined by HPLC analysis.

A bacterial pathogen infecting gametophytes of Saccharina japonica (Laminariales, Phaeophyceae)

A newly identified bacterial disease of kelp (Saccharina japonica) gametophytes was found in clone cultures. It is characterized by swollen gametophyte cells in the early period of infection followed by filamentous fading. An alginolytic marine bacterium referred to as A-1 was isolated from the diseased gametophytes. On the basis of 16S rDNA sequencing and morphological, physiological and biochemical characteristics, the bacterium was identified as a strain of the genus Alteromonas. By testing Koch’s postulates, Alteromonas sp. A-1 was further confirmed as the pathogen. The infection process was also investigated using both scanning electron and light microscopy.

Identification of Oplophorus Gracilirostris from South-East and South-West Coast of India using Mitochondrial Genetic Marker

The present study reports the occurrence of Oplophorus gracilirostris A. Milne-Edwards, 1881 from south- east and south-west coast of India on the basis of morphological as well as molecular data. It is the first report of insight into the mitochondrial genetic variation of O. gracilirostris. For this study, the DNA sequences of three mitochondrial genes, large subunit ribosomal DNA (16S rDNA), cytochrome oxidase I (COI) and cytochrome b (Cyt b) were submitted in the GenBank. Morphological examination of the specimen confirmed the identity of the species as O. gracilirostris. The pairwise genetic distance analysis, sequence identity and phylogenetic tree have shown that the specimen has identity with O. gracilirostris only on the basis of 16S rDNA sequence of earlier reports. In the case of COI it has shown some identity towards Oplophorus typus and Oplophorus spino- sus, but with a high genetic difference. This is the first submission of Cyt b sequence of O. gracilirostris. This study with sequence data of O. gracilirostris in GenBank will provide molecular support to the taxonomical identifications carried out on morphological basis.

English

A novel phosphate-solubilizing bacterium HPP16 from plant rhizosphere of Shandong University of Science and Technology districts of Qingdao (China) was isolated and the effects on promoting growth of mung bean (Phaseolus radiatus) seedlings in Campus and Jinshatan; two kinds of acidic soils were studied. HPP16 was identified as Enterobacter asburiae on the basis of 16S rDNA sequencing. It was Indole-3-acetic acid producer, synthesized siderophores and showed acid phosphatase activity. After mung bean was inoculated with HPP16, the germination rate and healthy stand in A-2 (inoculated with fermentation liquid) increased by 26 and 25% compared to A-4 (inoculated with the distilled water; negative control), and were 26 and 31.7% in B-2 (inoculated with fermentation liquid) compared to B-4 (inoculated with the distilled water, negative control). The individual plant height, fresh weight and dry weight in A-2 increased by 7, 10 and 6% compared to A-4,  and increased by 8.5, 24 and 9% in B-2 compared to B-4. Mung bean could also increase to absorb K+, Na+ and Mg2+ and improve the production of endogenous indole acetic acid (IAA), and also it reduced the production of abscisic acid (ABA). Findings of this study suggest that HPP16 may be exploited for developing a potential source of biofertilizer.   Key words: Plant growth promoting rhizobacteria, indole-3-acetic acid, siderophore, Enterobacter asburiae HPP16, mung bean, abscisic acid, phosphate-solubilizing bacteria (PSB).

Diversity of culturable sodium dodecyl sulfate (SDS) degrading bacteria isolated from detergent contaminated ponds situated in Varanasi city, India

In the present investigation, an attempt has been made to isolate and identify SDS-degrading bacteria from different detergent contaminated ponds situated in Varanasi city, UP, India. Initial survey of ponds indicated that these ponds were contaminated with detergents. Employing enrichment technique in minimal medium (PBM) with SDS as a sole carbon source, a total of 24 isolates were recovered from 7 detergent contaminated ponds. Studies on rates of SDS degradation indicated that the rate of SDS degradation varied from 97.2% to 19.6% after 12h incubation under identical conditions. An estimation of alkyl sulfatase activity indicated that the activity varied from 0.168 ± 0.004 to 0.024 ± 0.005 μmol SDS/mg protein/min. Molecular characterization of these isolates was performed on the basis of ARDRA and ERIC PCR, which indicated that these isolates were broadly divided in 8 groups. Some selected isolates were identified on the basis of 16S rDNA sequencing. It was found that these isolates belonged to Pseudomonas aeruginosa, Pseudomonas mendocina, Pseudomonas stutzeri, Pseudomonas alcaligenes, Pseudomonas pseudoalcaligenes, Pseudomonas putida and Pseudomonas otitidis respectively. Among these isolates P. aeruginosa, P. putida and P. otitidis have been previously shown to degrade and metabolize SDS, the rest of the isolates appear to be new.

English

114 diazotrophic bacteria from the rice rhizosphere of five districts of Eastern Uttar Pradesh (India) were isolated and screened for plant growth promoting (PGP) activities employing standard microbiological and biochemical techniques. All these isolates showed nitrogenase activity in the range of 0.23 to 1.72 µmol C2H4 mg-1protein h-1. Further analysis showed that 84 (73.68%) isolates were Indole-3-acetic acid (IAA) producer; the value of IAA production ranged from 10.1 to 353.0 µg IAA mg-1 protein. IAA production occurred solely in the medium supplemented with tryptophan. P solubilization activity was observed in 28 (24.56%) isolates, the activity being in the range of 38.50 to 321.0 P released μg mg-1 protein. 45 (39.46%) isolates were capable of producing siderophore, the range of production being 4.50 to 223.26 μg mg-1 protein. Analysis of molecular diversity was made by amplified ribosomal DNA restriction analysis (ARDRA) and denaturating gradient gel electrophoresis (DGGE), which exhibited distinct differences among all the isolates.Of the 114 isolates, twenty one (21) isolates showed multiple plant growth promoting traits and were potent in terms of PGP activities. These isolates were identified on the basis of 16S rDNA sequencing and belonged to the generaPantoea, Bacillus, Microbacterium, Pseudomonas, Sphingomonas, Ancylobacter,Enterobacter, Advenella, g-proteobacterium strain VA3S1, Rhizobium  andAgrobacterium. Findings of this study suggest that certain isolates may be exploited for developing a potential source of biofertilizer.   Key words: Plant growth promoting rhizobacteria, N2 fixation, amplified ribosomal DNA restriction analysis, indole-3-acetic acid, siderophore, denaturing gradient gel electrophoresis, temperature gradient gel electrophoresis

Optimization of Antimicrobial Production by a Marine Actinomycete Streptomyces afghaniensis VPTS3-1 Isolated from Palk Strait, East Coast of India

Totally 25 marine soil samples were collected from the region of Palk Strait of Bay of Bengal, Tamil Nadu, and were subjected to the isolation of actinomycetes. Sixty-eight morphologically distinct isolates were obtained and 37% (25) of them had antimicrobial activity. The potential producer was named as Streptomyces sp. VPTS3-1 and the phylogenetic evaluation on the basis of 16S rDNA sequence further categorized the organism as Streptomyces afghaniensis VPTS3-1. Further, the antimicrobial compound was extracted from the isolate using various solvents and the antimicrobial efficacies were tested against bacterial and fungal pathogens. In addition, in vitro optimization of parameters for the antimicrobial compound production revealed that the suitable pH as 7-8, the period of incubation as 9days, temperature (30°C), salinity (2%), and starch and KNO3 as the suitable carbon and nitrogen sources respectively in starch-casein medium.

Metagenomic characterization of oyster shell dump reveals predominance of Firmicutes bacteria

Metagenomic analyses were conducted to evaluate the biodiversity of oyster shell bacteria, under storage conditions, on the basis of 16s rDNA sequences. Temperature was recorded during a one year storage period, and the highest temperature (about 60 degrees C) was observed after five months ofstorage. Bacterial diversity was greatest in the initial stage sample, with 33 different phylotypes classified under seven phyla (Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia and unclassified bacteria), with 42.22% ofphylotypes belonging to Proteobacteria. The lowest diversity was found in the high temperature (fermentation) stage sample, with 10 different phylotypes belonging to Firmicutes (78.57%) and Bacteroidetes. In the final stage sample, bacteria were found belonging to Proteobacteria, Bacteroidetes, and Firmicutes, and some were unclassified bacteria. Of the bacteria constituting the final stage metagenome, 69.70% belonged to Firmicutes. Our results show that bacteria belonging to phylum Firmicutes were predominant during fermentation, and during the final stages of oyster shell storage, which suggests that these bacteria supposed to be the key players for oyster shell biodegradation.

Heavy metal resistance by two bacteria strains isolated from a copper mine tailing in China

Two highly heavy metal resistant indigenous bacterial strains, DX-T3-01 and DX-T3-03, were isolated from the biggest tailing in Asia-Dexing copper mine 4# tailing. The strain DX-T3-01 exhibited high tolerance to cadmium: 10 mM Cd2+ with yeast tryptophan peptone glucose (YTPG) agar plates and 18 mM in liquid medium. The strain DX-T3-03 was highly resistant to zinc and could endure 35 mM Zn2+ with YTPG agar plates and 40 mM in liquid medium. They also showed tolerance to other heavy metals, such as copper, lead and nickel. The morphology, physiological and biochemical characteristics of the two strains were examined by scanning electron microscope (SEM) and BIOLOG. The strains showed different metabolic patterns of carbon sources. The strain DX-T3-03 had a larger range of antibiotic resistance than DX-T3-01. On the basis of 16S rDNA sequencing, the two strains were identified as Ralstonia pickettii strain DX-T3-01 and Sphingomonas sp. strain DX-T3-03, respectively. This study supplied potential bacterial materials for tailing bioremediation in the future. Key words: Heavy metals, tolerant bacteria, isolation, mine tailing.

First Report of Herbaspirillum rubrisubalbicans Causing Mottled Stripe Disease on Sugarcane in China.

Narrow, red stripes were observed on leaves and sheaths of sugarcane in 2007 in DanZhou County of Hainan Province and XuWen County of GuangDong Province, China. Stripes were parallel to the leaf veins. Some stripes were short (2 to 10 cm) and some were >1 m long, extending from the base of leaves. Width of the stripes was 2 to 4 mm. Symptoms varied with the cultivar. Cv. Taiwang 25, which was the most affected, exhibited red stripes and stalk death from the apex. Cvs. Taiwang 26 and Guang Dong 00236 were slightly affected with only red stripes. Symptoms on cv. Taiwang 22 were mottled stripes. Severe losses were observed in the infected fields that were planted with cv. Taiwang 25, but there were no obvious losses in fields planted with the other three cultivars. Isolations were made from 10 individual plants from different cultivars and provinces that had red stripes, two of which also had apex death. Five independent bacterial isolates were obtained from tissue showing the red stripe symptoms on potato dextrose agar medium. The percentage of positive samples was 50%. No bacteria were obtained from necrotic apex tissue. Bacterial cells were 0.92 to 1.55 × 0.20 to 0.22 μm slightly curved rods that were motile with one to two polar flagella. Colonies on nutrient agar were 2 to 3 mm in diameter, circular, smooth, entire, and milky white. Colonies on King's medium B were nonfluorescent under 365-nm UV light. Five bacterial strains were inoculated by injecting bacterial suspensions (1 × 108 CFU/ml) into the base of the leaves of 6-month-old cv. Taiwang 25 plants (1). Red stripes appeared 7 to 10 days after inoculation and bacteria were reisolated. The reisolated bacteria were identical to the original strains in colony morphology and 16S rDNA sequence. A hypersensitive response appeared within 24 h when 1 × 108 CFU/ml bacteria suspensions were infiltrated into tobacco leaves. Approximately 1,000-bp DNA fragments were amplified with universal primers UP1 (5'-TACGTGCCAGCAGCCGCGGTAATA-3') and UP2 (5'-AGTAAGGAGGGTATCCAACCGCA-3') (3). Primers UP1 and UP2 are complementary to nucleotide sequence 509 to 523 and 1541 to 1522, respectively, of the Escherichia coli 16S rDNA gene. The fragment amplified by these primers was approximately 1,032 bp. The 16S rDNA sequences of the five strains were deposited in GenBank as Accession Nos. GQ476791-5. They all shared 99% nucleotide identity with the type strain of Herbaspirillum rubrisubalbicans (GenBank No. AJ238356.1). All five strains were identified as H. rubrisubalbicans on the basis of 16S rDNA sequence and pathogenicity to sugarcane, and the disease was identified as mottled stripe disease (2). Since we were not able to isolate bacteria from necrotic apex tissue, this symptom on cv. Taiwang 25 may not be related to the H. rubrisubalbicans infection. To our knowledge, this is the first report of mottled stripe disease in China.

Investigation of biological behavior and colonization ability of Iranian indigenous phosphate solubilizing bacteria

Soil phosphorous (P) uptake mechanisms by the interaction of plants and soil microorganisms benefit plant growth with preparing agriculture inoculants. But it is influenced by soil factors. The present study was performed to identify three effective strains of phosphate solubilizing bacteria (PSB) on the basis of 16S rDNA sequence in vitro. Bacillus lentus strain PS5, Bacillus licheniformis strain PS7 and Pseudomonas putida strain PS13 were isolated from an alkaline soil in Iran and the rhizosphere of Beta vulgaris and Solanum tuberosom. Their high root colonization ability and P solubilizing activity was detected in relation to soil physical and chemical properties influenced by environmental factors including salinity of 800 mM/L and temperature of 42 °C. Root colonization assays were performed to determine the distribution and metabolic activity of the bacterial isolates obtained from the potato rhizosphere. The seedling was planted in the soil sample inoculated with three strains after lux bioluminescence gene insertion and also marking for resistance to kanamycine and rifampin. Then it was placed in non-sterile natural soil. The introduced bacterial strains were quantified by dilution plating on antibiotic media together with observation of bioluminescence. The results demonstrated that these strains could survive in the potato root system at high temperature, high H + concentrations and high salt concentrations. These three bacterial isolates possessed the ability to solubilize phosphate under stress conditions of alkaline soils in Iran as high salinity, high H + concentrations and high temperature.

Molecular diversity and catalytic activity of Thermus DNA polymerases

Thermus aquaticus DNA polymerase (Taq polymerase) made the polymerase chain reaction feasible and led to a paradigm shift in genomic analysis. Other Thermus polymerases were reported to have comparable performance in PCR and there was an analysis of their properties in the 1990s. We re-evaluated our earlier phylogeny of Thermus species on the basis of 16S rDNA sequences and concluded that the genus could be divided into eight clades. We examined 22 representative isolates and isolated their DNA polymerase I genes. The eight most diverse polymerase genes were selected to represent the eight clades and cloned into an expression vector coding for a His-tag. Six of the eight polymerases were expressed so that there was sufficient protein for purification. The proteins were purified to homogeneity and examination of the biochemical characteristics showed that although they were competent to perform PCR, none was as thermostable as commercially available Taq polymerase; all had similar error-frequencies to Taq polymerase and all showed the expected 5'-3' exonuclease activity. We conclude that the initial selection of T. aquaticus for DNA polymerase purification was a far-reaching and fortuitous choice but simple mutagenesis procedures on other Thermus-derived polymerases should provide comparable thermostability for the PCR reaction.

Selection and characterization of aerobic bacteria capable of degrading commercial mixtures of low-ethoxylated nonylphenols

Isolation and characterization of new bacterial strains capable of degrading nonylphenol ethoxylates (NPnEO) with a low ethoxylation degree, which are particularly recalcitrant to biodegradation. Seven aerobic bacterial strains were isolated from activated sludges derived from an Italian plant receiving NPnEO-contaminated wastewaters after enrichment with a low-ethoxylated NPnEO mixture. On the basis of 16S rDNA sequence, the strains were positioned into five genera: Ochrobactrum, Castellaniella, Variovorax, Pseudomonas and Psychrobacter. Their degradation capabilities have been evaluated on two commercial mixtures, i.e. Igepal CO-210 and Igepal CO-520, the former rich in low ethoxylated congeners and the latter containing a broader spectrum of NPnEO, and on 4-n-nonylphenol (NP). The strains degraded Igepal CO-210, Igepal CO-520 and 4-n-NP all applied at the initial concentration of 100 mg l(-1), by 35-75%, 35-90% and 15-25%, respectively, after 25 days of incubation. Some of the isolated strains, in particular the Pseudomonas strains BCb12/1 and BCb12/3, showed interesting degradation capabilities towards low ethoxylated NPnEO congeners maintaining high cell vitality. Increased knowledge of bacteria involved in NPnEO degradation and the possibility of using the isolated strains in tailored process for a tertiary biological treatment of effluents of wastewater treatment plants.

Production of SacI and SacII isoschizomers by soil streptomycetes

Five fresh soil Streptomyces spp. strains were isolated, phylogenetically characterized on the basis of 16S rDNA sequences and analyzed for the presence of restriction modification systems. Three type II site-specific endonucleases were detected and partially purified. Two isolated enzymes were isoschizomers of SacI restriction endonuclease recognizing 5′-GAGCTC-3′ sequence; the third one recognised 5′-CCGCGG-3′ sequence and it was an isoschizomer of SacII. SacII like modification was observed in other two isolates having no detectable restriction activity. The lack of correlation between restriction and modification phenotypes and phylogenetic classification of the isolates indicates efficient gene transfer mechanism in the Streptomyces genus.

Molecular and physiological characterisation of psychrotrophic hydrocarbon-degrading bacteria isolated from Terra Nova Bay (Antarctica)

A set of 21 Antarctic marine bacteria isolated from the Ross Sea and able to utilise diesel fuel as the sole carbon and energy source was characterised. Isolates were analysed by amplified 16S rDNA restriction analysis using the enzyme AluI, resulting in two different groups corresponding to different bacterial species. These species were assigned to the genera Rhodococcus and Alcaligenes, on the basis of 16S rDNA sequencing. This low degree of inter-specific biodiversity was parallel to a low intra-specific biodiversity, as shown by Random Amplified Polymorphic DNA analysis. Then, a 550-bp DNA fragment coding for the inner region of alkane mono-oxygenase was PCR-amplified from the genome of each strain. The phylogenetic analysis of the sequence of the putative AlkB protein coded for by the amplified DNA fragment revealed that these alkB genes were very likely inherited by horizontal gene transfer. Lastly, the analysis of the biodegradation ability of four strains revealed two different strategies of hydrocarbon uptake, mediated either by bio-surfactants and peculiar of Rhodococcus isolates, or by membrane modifications and shown by Alcaligenes isolates. In order to understand the interrelationships between hydrocarbon-degrading isolates, the dynamics of two strains, belonging to Rhodococcus and Alcaligenes, grown together in a co-culture was also followed over a seventeen days period.