Petroleum-contaminated Soil Samples Research Articles

CHARACTERIZATION OF A NEWLY ISOLATED AZO-DYE DEGRADING KLEBSIELLA SP. STRAIN RGUDBI01

Azo-dyes such as crystal violet are commonly used ingredient in all types of dying industries which more often eventually reach water and soil due to washing and disposal practices. They are non-biodegradable inside higher organisms and are less biodegradable due to their xenobiotic character. However, some of the microbes exhibit their extensive potential to degrade such recalcitrants. This study reports the isolation and characterization of a newly isolated Klebsiella sp. strain RGUDBI01 from petroleum-contaminated soil samples. The species-level identification was done by 16S rDNA gene sequencing (ON945611.1). The isolate exhibited 88% azo-dye degradation just after 3 days of incubation under optimized conditions. The treated samples exhibited a significant increase in the growth of Cicer arietinum seeds compared to the control group. This result suggests that the dye-contaminated samples, after treatment, displayed non-cytotoxic behavior. The strain also showed its potential to tolerate and withstand a wide range of pH, salinity, and substrate concentration which supports its futuristic environmental application. In addition to the above, the strain could also produce biosurfactants with ʋC=C, ʋC=C-H, and ʋC-C functional groups which were evaluated based on FTIR spectral analysis.

Genomic and biotechnological potential of a novel oil-degrading strain Enterobacter kobei DH7 isolated from petroleum-contaminated soil

In this study, a novel oil-degrading strain Enterobacter kobei DH7 was isolated from petroleum-contaminated soil samples from the industrial park in Taolin Town, Lianyungang, China. The whole genome of the strain was sequenced and analyzed to reveal its genomic potential. The oil degradation and growth conditions including nitrogen, and phosphorus sources, degradation cycle, biological dosing, pH, and oil concentration were optimized to exploit its commercial application. The genome of the DH7 strain contains 4,705,032 bp with GC content of 54.95% and 4653 genes. The genome analysis revealed that there are several metabolic pathways and enzyme-encoding genes related to oil degradation in the DH7 genome, such as the paa gene cluster which is involved in the phenylacetic acid degradation pathway, and complete degradation pathways for fatty acid and benzoate, genes related to chlorinated alkanes and olefins degradation pathway including adhP, frmA, and adhE, etc. The strain DH7 under the optimized conditions has demonstrated a maximum degradation efficiency of 84.6% after 14 days of treatment using synthetic oil, which comparatively displays a higher oil degradation efficiency than any Enterobacter species known to date. To the best of our knowledge, this study presents the first-ever genomic studies related to the oil degradation potential of any Enterobacter species. As Enterobacter kobei DH7 has demonstrated significant oil degradation potential, it is one of the good candidates for application in the bioremediation of oil-contaminated environments.

Genomic insights revealed the environmental adaptability of Planococcus halotolerans Y50 isolated from petroleum-contaminated soil on the Qinghai-Tibet Plateau

The Tibetan Plateau niche provides unprecedented opportunities to find microbes that are functional and commercial significance. The present study investigated the physiological and genomic characteristics of Planococcus halotolerans Y50 that was isolated from a petroleum-contaminated soil sample from the Qinghai-Tibet Plateau, and it displayed psychrotolerant, antiradiation, and oil-degraded characteristics. Whole genome sequencing indicated that strain Y50 has a 3.52 Mb genome and 44.7% G + C content, and it possesses 3377 CDSs. The presence of a wide range of UV damage repair genes uvrX and uvsE, DNA repair genes radA and recN, superoxide dismutase, peroxiredoxin and dioxygenase genes provided the genomic basis for the adaptation of the plateau environment polluted by petroleum. Related experiments also verified that the Y50 strain could degrade n-alkanes from C11-C23, and approximately 30% of the total petroleum at 25 °C within 7 days. Meanwhile, strain Y50 could withstand 5 × 103 J/m2 UVC and 10 KGy gamma ray radiation, and it had strong antioxidant and high radical scavengers for superoxide anion, hydroxyl radical and DPPH. In addition, pan-genome analysis and horizontal gene transfers revealed that strains with different niches have obtained various genes through horizontal gene transfer in the process of evolution, and the more similar their geographical locations, the more similar their members are genetically and ecologically. In conclusion, P. halotolerans Y50 possesses high potential of applications in the bioremediation of alpine hydrocarbons contaminated environment.

Antibiofilm Activity of Biosurfactant Produced by Bacterial Strain Isolated from Petroleum-Contaminated Sites

The escalating emergences of drug-resistant strains of Pseudomonas aeruginosa coupled with the decline in the development of new antibiotics have increased the morbidity and mortality rates during the past decades. The aim of the present work was to investigate the antibacterial and antibiofilm activity of biosurfactant produced by bacterial strain IHD19 isolated from hydrocarbon-polluted soil against biofilm forming clinical isolates of Pseudomonas aeruginosa. Isolates from petroleum-contaminated soil sample were screened and evaluated for biosurfactant production. Rapid methods such as drop collapse test, emulsification test, hemolysis test, lipase test were used for screening of biosurfactant production by bacterial strain IHD19. Bacterial strain IHD19 was selected on the basis of its efficiency to produce biosurfactant. Growth study of bacterial strain IHD19 was conducted at different physicochemical conditions aiming to find out the optimal condition for growth of bacterial strain IHD19 to obtain higher biosurfactant production. Thin-layer chromatography and FTIR analyses were done to characterize the biosurfactant produced by bacterial strain IHD19. Subsequently, the antibacterial activity of biosurfactant IHD19 on multidrug-resistant clinical isolates of Pseudomonas aeruginosa was investigated by agar well-diffusion method. Biofilm-forming clinical isolates of Pseudomonas aeruginosa were identified using crystal violet assay. Finally, the antibiofilm activity of biosurfactant IHD 19 was determined using microtiter plate assay and MBIC50 and MBIC90 were calculated. Bacterial strain IHD 19 was found positive for drop collapse test, lipase test and showed β-hemolysis on blood agar. The emulsification efficiency of biosurfactant IHD19 after 24 h (E24%) was 87.5% against engine oil. The thin-layer chromatography and FTIR analysis revealed the polymeric nature of the biosurfactant. Biosurfactant IHD19 displayed significant antibacterial and antibiofilm activity against twenty-five multidrug-resistant clinical isolates of Pseudomonas aeruginosa with more than 50% (MBIC50) in concentration range of 0.5–4 µg/ml and 90% biofilms inhibition (MBIC90) in concentration range of 16–32 µg/ml, respectively. Phylogenetic tree showed biosurfactant producing bacterial strain IHD19 to be relative to Bacillus family. With 16 s rRNA analysis the isolated bacterial strain IHD19 was identified as Bacillus pumilus. The current study proposes potential exploration of biosurfactant to subdue the issue of biofilms formation by MDR Pseudomonas aeruginosa.

Comparative study of antimicrobial efficiency of biosurfactant producing Pseudomonas spp. from different soil samples

Amphiphilic biosurfactants are surface-active biological molecules secreted by hydrocarbanoclastic microorganisms. Biosurfactants are eco-friendly, less toxic, biodegradable, and low-cost material, so it has more advantages over chemical surfactants. In this research, Pseudomonas spp., biosurfactant producing microorganisms isolated from different sources of soil samples. IS1, IS2, IS3, IS4 isolates obtained from Garden soil sample; Metal contaminated soil sample; Petroleum contaminated soil sample; Oil contaminated soil sample; respectively. Each isolates identified as Pseudomonas spp. Furthermore, screened for biosurfactant producers. Each isolate showed positive results for the hemolysis test, drop collapse test, oil displacement test, and emulsification test. All isolate incubated in mineral salt medium for biosurfactant production. Biosurfactant extracted from IS1, IS2, IS3, IS4 showed 35%, 65%, 20%, 52% emulsification index respectively. Antimicrobial activity of extracted biosurfactants against pathogenic microorganisms checked by agar cup method. IS2 isolate shows the highest antimicrobial activity among all. All isolate showed a higher zone of inhibition against gram-positive microorganisms than gram-negative microbes. The purpose of this study involves the assessment of the antimicrobial activity of biosurfactant producers from the soil environment.

Factors affecting in situ analysis of total petroleum hydrocarbons in contaminated soils by using a mid-infrared diffuse reflectance spectroscopy

The hand-held mid-infrared diffuse reflectance infrared Fourier transform (MIR-DRIFT) spectrometer was used to assess the applicability of on-site and real time monitoring of total petroleum hydrocarbons (TPH) in contaminated soils during site characterization and remediation. Field measurement devices (MIR-DRIFT and turbidimetric screening test kits) were used to analyze reference soils with concentration ranging from 713 to 54790 mg/kg and compared with the results by a gas chromatography/mass spectrometry method (GC/MS). In situ field measurement of 147 petroleum-contaminated soil samples from 11 contaminated sites was correlated with laboratory-determined soil TPH levels by GC/MS. The concentrations of TPH by MIR-DRIFT were significantly correlated to the concentrations of TPH by GC/MS. Detection of TPH by the MIR spectrometer was not affected by the weathering effects of diesel-contaminated soils. Soils contaminated by mixed fuels with high content of gasoline constituents may cause the potential interference in MIR measurement. In field practice, interference may be attributed to soil moisture, soil organic matter, and soil texture. Soil moisture below 5% is required to reduce variation of infrared beam reflected from high level of surface liquid. When measuring the contaminated soil with a high organic matter content, the results may be overestimated due to the possible effects of surface reflection and interference. Clay and partial silty clay soils were not suitable for MIR spectrometer detection due to a potential shielding effect to reduce the infrared radiation absorbed by TPH. Future research is warranted to reduce the variation caused by soil texture and heterogeneity in TPH prediction.

Distribution of Bacterial Communities in Petroleum-Contaminated Soils from the Dagang Oilfield, China

Diversity in bacterial communities was investigated along a petroleum hydrocarbon content gradient (0–0.4043 g/g) in surface (5–10 cm) and subsurface (35–40 cm) petroleum-contaminated soil samples from the Dagang Oilfield, China. Using 16S rRNA Illumina high-throughput sequencing technology and several statistical methods, the bacterial diversity of the soil was studied. Subsequently, the environmental parameters were measured to analyze its relationship with the community variation. Nonmetric multidimensional scaling and analysis of similarities indicated a significant difference in the structure of the bacterial community between the nonpetroleum-contaminated surface and subsurface soils, but no differences were observed in different depths of petroleum-contaminated soil. Meanwhile, many significant correlations were obtained between diversity in soil bacterial community and physicochemical properties. Total petroleum hydrocarbon, total organic carbon, and total nitrogen were the three important factors that had the greatest impacts on the bacterial community distribution in the long-term petroleum-contaminated soils. Our research has provided references for the bacterial community distribution along a petroleum gradient in both surface and subsurface petroleum-contaminated soils of oilfield areas.

Isolation and characterization of biosurfactant producing microorganisms from petroleum contaminated soil samples for EOR and bioremediation

ABSTRACTUsing of biosurfactant producing microorganisms for pipeline cleaning, bioremediation, enhanced oil recovery, etc. is a much soughed approach of petroleum industry. Although, many alternatives are available to serve these purposes, being ecofriendly and economic, microbial application is considered superior than most of the alternatives. This paper presents a comprehensive study on effectiveness of bacterial strain isolated from oil contaminated soil sample of Lakwa oilfield for required purposes. Its temperature sustainability and surfactant production capability was studied. Further characteristics of the produced biosurfactant were assessed through Emulsification Index measurement, Fourier Transform Infrared Spectra, Drop Collapse Test, Contact Angle and Viscosity measurement.

Influence of oil pollution on soil microbial community diversity

Bacteria, actinomycetes and fungi are the three major groups of soil microbes. Soil microbes play a critical role in ecological and biodegradation processes in petroleum-contaminated soils. Based on the actual situation, this study took the oil polluted soil around the abandoned oil well in Shehong County, Suining City, Sichuan Province as the test soil. First, we determined the physiochemical properties of the tested soil; then we analyzed the changes of physiochemical properties and the three major microbes in petroleum contaminated soils. The number of the three major microbes in contaminated soils was relatively fewer than uncontaminated samples, and the water content of the soil was in positive correlation with the number of microbes. Also we assessed the soil bacteria community diversity and changes therein in petroleum-contaminated soils using 454 pyrosequencing of 16S rRNA genes. No less than 23 982 valid reads and 6 123 operational taxonomic units (OTUs) were obtained from all 4 studied samples. OTU richness was relatively higher in contaminated soils than uncontaminated samples. Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Planctomycetes and Proteobacteria were the dominant phyla among all the soil samples. However, the prokaryotes community abundance of phyla was significantly different in the four samples. The most abundant OTUs associated with petroleum-contaminated soil sample were the sequences related to Acidobacteria, Actinobacteria and Proteobacteria, whereas the most abundance sequences with uncontaminated sample were those related to Actinobacteria, Bacteroidetes and Proteobacteria.

Dual bioremediation of phenol and Cr(VI) by mixed microbial cultures in the presence of molasses.

Simultaneous phenol and Cr(VI) bioremoval by two different mixed cultures, from petroleum-contaminated soil (PS) and boron-contaminated wastewater (BW), was investigated in regard to different culture media, pH levels (6-8), initial phenol (25-100 mg/L) and Cr(VI) (15-50 mg/L) concentrations. The optimum medium was found to be mineral salt medium tested, which contained 1% (v/v) molasses (MSM). Optimum pH values were 6 for PS and 8 for BW. All of the phenol present in the samples was mineralized regardless of its concentrations tested, Cr(VI) bioremoval was enhanced by the increase in phenol concentrations, and molasses also exerted a positive effect on Cr(VI) removal, and the yields reached 100% for both pollutants, even at 13.1 mg/L Cr(VI) and 91.1 mg/L phenol concentration in PS samples. In MSM containing PS samples approximate efficiency was 100% for phenol removal; but Cr(VI) removal ratios were 64.9% and 41.7% at 25.8 mg/L and 41.3 mg/L concentrations, respectively. Finally it can be concluded that molasses stimulated Cr(VI) bioremoval at elevated phenolic conditions in the mixed microbial culture, and molasses might be of use for the bioremediation of phenol and Cr(VI) polluted wastewaters.

Effects of nutrition optimization strategy on rhamnolipid production in a Pseudomonas aeruginosa strain DN1 for bioremediation of crude oil

Abstract An indigenous rhamnolipid biosurfactant-producing Pseudomonas aeruginosa strain DN1 was isolated from petroleum-contaminated soil samples which could use crude oil as the sole carbon and energy source. A high yield of 25.9 g/L rhamnolipid mixture was achieved in a shake flask by nutrition optimization strategy based on high throughput screening of strain DN1, supplemented with palm oil and 5.0 g/L sodium nitrate at a C/N ratio of 20. These rhamnolipids reduced the surface tension of water from 45.23 to 25.88 mN/m with a critical micelle concentration of 50 mg/L, and were able to emulsify several hydrocarbons and showed excellent emulsification (100%). A total number of 6 monorhamnolipid homologues (Rha-C8-C8; Rha-C10:1-C8; Rha-C12:2; Rha-C12; Rha-C14-C16; Rha-C16-C16) and 7 dirhamnolipid homologues (Rha-Rha-C10; Rha-Rha-C12; Rha-Rha-C14; Rha-Rha-C8-C10; Rha-Rha-C10-C8:1; Rha-Rha-C10-C10; Rha-Rha-C10-C12) were detected by liquid chromatography/ mass spectrometry analysis allied to electrospray ionization mass spectrometry. In addition, strain DN1 exhibited an enhanced capacity to degrade crude oil (90.52%) by its rhamnolipids. The results indicated that the use of nutrition optimization strategy will be the most popular process strategy for high rhamnolipids productivity by this strain for in situ bioremediation of crude oil.

Degenerate primers as biomarker for gene-targeted metagenomics of the catechol 1, 2-dioxygenase-encoding gene in microbial populations of petroleum-contaminated environments

Catechol 1, 2-dioxygenase (1, 2-CTD) plays an important role in the biodegradation of most aromatic pollutants (e.g. phenol) by cleaving the bond between the phenolic hydroxyl groups. In this study, we analysed microbial populations in petroleum-contaminated soil samples by the culture-dependent approach and chose one population as a sample location for metagenomic studies. This population showed the largest number of phenol-degrading isolates and the most phylogenetic diversity based on repetitive sequence-based PCR and 16S rDNA analyses. The isolates were assigned mainly to the bacterial genera Acinetobacter and Pseudomonas. To enable maximum recovery of 1, 2-CTD coding sequence from the genomic pool of bacterial populations, we extracted the substrate-induced RNA, reverse-transcribed it to the specific cDNA using primers designed for this purpose and constructed a metagenomic library. Alignment analysis of one recombinant sequence indicated a significant divergence, with the 1, 2-CTD gene of Pseudomonas aeruginosa DK2 as the closest species according to sequence similarity. This result indicates that such specifically designed primers are likely suitable candidates as biomarkers to construct 1, 2-CTD gene-targeted metagenomic libraries. By sequencing the larger clones of this metagenomic library, we hope to obtain novel and unpredicted 1, 2-CTD genes that can contribute to our knowledge of microbial diversity of these genes.

Development of a hybrid proximal sensing method for rapid identification of petroleum contaminated soils

Using 108 petroleum contaminated soil samples, this pilot study proposed a new analytical approach of combining visible near-infrared diffuse reflectance spectroscopy (VisNIR DRS) and portable X-ray fluorescence spectrometry (PXRF) for rapid and improved quantification of soil petroleum contamination. Results indicated that an advanced fused model where VisNIR DRS spectra-based penalized spline regression (PSR) was used to predict total petroleum hydrocarbon followed by PXRF elemental data-based random forest regression was used to model the PSR residuals, it outperformed (R2=0.78, residual prediction deviation (RPD)=2.19) all other models tested, even producing better generalization than using VisNIR DRS alone (RPD's of 1.64, 1.86, and 1.96 for random forest, penalized spline regression, and partial least squares regression, respectively). Additionally, unsupervised principal component analysis using the PXRF+VisNIR DRS system qualitatively separated contaminated soils from control samples. CapsuleFusion of PXRF elemental data and VisNIR derivative spectra produced an optimized model for total petroleum hydrocarbon quantification in soils.

Lipopeptide biosurfactant production bacteria Acinetobacter sp. D3-2 and its biodegradation of crude oil

In this work, a hydrocarbon-degrading bacterium D3-2 isolated from petroleum contaminated soil samples was investigated for its potential effect in biodegradation of crude oil. The strain was identified as Acinetobacter sp. D3-2 based on morphological, biochemical and phylogenetic analysis. The optimum environmental conditions for growth of the bacteria were determined to be pH 8.0, with a NaCl concentration of 3.0% (w/v) at 30 °C. Acinetobacter sp. D3-2 could utilize various hydrocarbon substrates as the sole carbon and energy source. From this study, we also found that the strain had the ability to produce biosurfactant, with the production of 0.52 g L(-1). The surface tension of the culture broth was decreased from 48.02 to 26.30 mN m(-1). The biosurfactant was determined to contain lipopeptide compounds based on laboratory analyses. By carrying out a crude oil degradation assay in an Erlenmeyer flask experiment and analyzing the hydrocarbon removal rate using gas chromatography, we found that Acinetobacter sp. D3-2 could grow at 30 °C in 3% NaCl solution with a preferable ability to degrade 82% hydrocarbons, showing that bioremediation does occur and plays a profound role during the oil reparation process.

Screening of a Thermophilic Hydrocarbon-Degrading Bacterial Consortium and Community Structure Analysis

5 highly efficient hydrocarbon-degrading mixed bacteria were obtained from the petroleum-contaminated soil samples by the traditional method of enrichment and acclimation. The KL9-1 consortium had a wide temperature tolerance range and higher hydrocarbon degrading ability. The degradation rate of thin oil and heavy oil was up to 43.27% and 20.09% respectively through 7 d at 45oC. After several times of isolation and purification, three dominant strains with the capability of hydrocarbon-degrading were obtained, and their petroleum degradation rates were all over 30%. According to its morphological and 16S rDNA sequence characteristics, KL9-1-1 and KL9-1-2 were identified as Pseudomonas sp., and the KL9-1-3 was identified as Rhodococcus sp..

Characterization of Aromatic Hydrocarbon Rading Bacteria from Petroleum Contaminated Sites

Aromatic hydrocarbons such as benzene, hexane, toluene, naphthalene and xylene degrading bacteria such as Flavobacterium spp.1 & 2 and Pseudomonas spp.1 & 2 were isolated from petroleum contaminated soil samples. They were resistant to heavy metals such as lead, iron, zinc, cobalt and mercury. The optimum pH for hydrocarbon degradation by Flavobacterium spp.1 was 9. Flavobacterium spp.2, Pseudomonas spp.1 & 2 have shown optimum pH 7 for their degradation. The optimum temperature for hydrocarbon degradation by Flavobacterium spp.1 & 2 and Pseudomonas spp.1 & 2 were at 40°C & 45°C .

Novel rhamnolipid biosurfactants produced by a polycyclic aromatic hydrocarbon-degrading bacterium Pseudomonas aeruginosa strain NY3

A novel rhamnolipid biosurfactant-producing and Polycyclic Aromatic Hydrocarbon (PAH)-degrading bacterium Pseudomonas aeruginosa strain NY3 was isolated from petroleum-contaminated soil samples. Strain NY3 was characterized by its extraordinary capacity to produce structurally diverse rhamnolipids. A total of 25 rhamnolipid components and 37 different parent molecular ions, representing various metal ion adducts (Na +, 2Na + and K +), were detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Among these compounds are ten new rhamnolipids. In addition to its biosurfactant production, strain NY3 was shown to be capable of efficient degradation of PAHs as well as synergistic improvement in the degradation of high molecular weight PAHs by its biosurfactant. These findings have added novel members to the rhamnolipid group and expanded current knowledge regarding the diversity and productive capability of rhamnolipid biosurfactants from a single specific strain with variation of only one carbon source. Additionally, this paper lays the foundation for improvement in the yield of NY3BS and study of the degradation pathway(s) of PAHs in P. aeruginosa strain NY3.

Differential utilization of pyrene as the sole source of carbon by Bacillus subtilis and Pseudomonas aeruginosa strains: role of biosurfactants in enhancing bioavailability

Our goal is to compare the efficiency of utilization of pyrene as the sole source of carbon for growth and energy by two nonactinomycetous groups of bacteria viz., Bacillus subtilis DM-04 and Pseudomonas aeruginosa mucoid (M) and nonmucoid (NM) strains, isolated from a petroleum-contaminated soil sample of north-east India. Bacillus subtilis DM-04 and P. aeruginosa M and NM bacterial strains were capable of secreting biosurfactant in the culture medium while growing on pyrene and their pyrene utilizing efficiency was demonstrated by correlating the bacterial growth in the presence of pyrene as the sole source of carbon along with a concomitant decrease in pyrene content from the culture medium with respect to time. The biosurfactant secreted by the respective bacterial strains enhanced the apparent solubility of pyrene by factors of 5-7 and influenced the bacterial cell surface hydrophobicity resulting in higher uptake and utilization of pyrene by bacteria. The growth of B. subtilis DM-04 and P. aeruginosa M and NM strains at the expense of pyrene after 96 h showed an assimilation of about 48.0 +/- 1.1% (mean +/- SD) and 32.0 +/- 0.6% (mean +/- SD) of pyrene carbon, respectively, showing differences in metabolism of pyrene by these bacterial strains. Bacillus subtilis DM-04 strain exhibited higher utilization and cellular assimilation of pyrene compared with P. aeruginosa M and NM strains. Further, the biosurfactants produced by the bacteria under study are capable of enhancing the solubility of pyrene in aqueous media and can influence the cell surface hydrophobicity of the biosurfactant-producing strains that results in a higher uptake of pyrene. It may be suggested that the bacteria used in this study are suitable candidates for practical field application for effective in situ bioremediation of pyrene-contaminated sites.

Crude petroleum-oil biodegradation efficiency of Bacillus subtilis and Pseudomonas aeruginosa strains isolated from a petroleum-oil contaminated soil from North-East India

The efficiency of Bacillus subtilis DM-04 and Pseudomonas aeruginosa M and NM strains isolated from a petroleum contaminated soil sample from North-East India was compared for the biodegradation of crude petroleum-oil hydrocarbons in soil and shake flask study. These bacterial strains could utilize crude petroleum-oil hydrocarbons as sole source of carbon and energy. Bioaugmentation of TPH contaminated microcosm with P. aeruginosa M and NM consortia and B. subtilis strain showed a significant reduction of TPH levels in treated soil as compared to control soil at the end of experiment (120 d). P. aeruginosa strains were more efficient than B. subtilis strain in reducing the TPH content from the medium. The plate count technique indicated expressive growth and biosurfactant production by exogenously seeded bacteria in crude petroleum-oil rich soil. The results showed that B. subtilis DM-04 and P. aeruginosa M and NM strains could be effective for in situ bioremediation.

Correlation between diverse cyclic lipopeptides production and regulation of growth and substrate utilization by Bacillus subtilis strains in a particular habitat

The two Bacillus subtilis strains (DM-03 and DM-04) were isolated from two extremely different habitats; one from the traditional fermented food and another one from a petroleum contaminated soil sample. These strains produced quantitatively and qualitatively different cyclic lipopeptides isoforms under laboratory culture conditions. MALDI-TOF mass spectral analysis revealed that lipopeptide profile varied according to the producing B. subtilis strains; iturins and surfactins isoforms were pre-dominant cyclic lipopeptides produced by B. subtilis DM-03 and DM-04 strains, respectively. A comparative study showed that these strains possessed distinct preferences for the carbon and nitrogen substrates, temperature and pH for optimal growth and biosurfactant production. Our study documented that the cyclic lipopeptide isoforms produced by the respective strains played an important role in the utilization of available hydrophobic substrate(s) from their natural habitats and conferred some kind of competitive advantage to the producing B. subtilis strains in their parent ecological niche.