Degradation of hexadecane by Enterobacter cloacae strain TU that secretes an exopolysaccharide as a bioemulsifier

Microbial remediation of oil-contaminated shorelines: a review

Frequent marine oil spills have led to increasingly serious oil pollution along shorelines. Microbial remediation has become a research hotspot of intertidal oil pollution remediation because of its high efficiency, low cost, environmental friendliness, and simple operation. Many microorganisms are able to convert oil pollutants into non-toxic substances through their growth and metabolism. Microorganisms use enzymes' catalytic activities to degrade oil pollutants. However, microbial remediation efficiency is affected by the properties of the oil pollutants, microbial community, and environmental conditions. Feasible field microbial remediation technologies for oil spill pollution in the shorelines mainly include the addition of high-efficiency oil degrading bacteria (immobilized bacteria), nutrients, biosurfactants, and enzymes. Limitations to the field application of microbial remediation technology mainly include slow start-up, rapid failure, long remediation time, and uncontrolled environmental impact. Improving the environmental adaptability of microbial remediation technology and developing sustainable microbial remediation technology will be the focus of future research. The feasibility of microbial remediation techniques should also be evaluated comprehensively.

Nanogap traps for passive bacteria concentration and single-point confocal Raman spectroscopy

A microfluidic device enabling the isolation and concentration of bacteria for analysis by confocal Raman spectroscopy is presented. The glass-on-silicon device employs a tapered chamber surrounded by a 500 nm gap that serves to concentrate cells at the chamber apex during sample perfusion. The sub-micrometer gap retains bacteria by size exclusion while allowing smaller contaminants to pass unimpeded. Concentrating bacteria within the fixed volume enables the use of single-point confocal Raman detection for the rapid acquisition of spectral signatures for bacteria identification. The technology is evaluated for the analysis of E. cloacae, K. pneumoniae, and C. diphtheriae, with automated peak extraction yielding distinct spectral fingerprints for each pathogen at a concentration of 103 CFU/ml that compare favorably with spectra obtained from significantly higher concentration reference samples evaluated by conventional confocal Raman analysis. The nanogap technology offers a simple, robust, and passive approach to concentrating bacteria from dilute samples into well-defined optical detection volumes, enabling rapid and sensitive confocal Raman detection for label-free identification of focused cells.

Characteristics of exopolysaccharides produced by isolates from natural bioflocculant of Ruditapes philippinarum conglutination mud

Three novel types of exopolysaccharides (EPS) EPS-S8, EPS-S5, and EPS-F10 were extracted and purified from bacterial isolates Bacillus sp. GHS8, Pseudoalteromonas sp. GHS5 and Psychrobacter sp. GHF10, which were originated from natural bioflocculant of Ruditapes philippinarum conglutination mud (RPM), respectively. The EPS had similar function groups C-H, N-H, C-O, and C = O. The EPS were composed of different monosaccharides (EPS-F10, Man: GlcN: GlcUA: GalUA = 1:0.66:5.75:0.51; EPS-S5, Man: Gal: GlcN: Rib = 1: 0.50: 2.94: 0.26; EPS-S8, Man: Gal: GlcN = 1:1.54:7.69). The molecular weights (Mw) of EPS were ordered as 51.4 kDa (EPS-S5) > 9.15 kDa (EPS-S8) > 4.41 kDa (EPS-F10). Three types of EPS all showed higher peak flocculation activities than the reported crude EPS from the RPM. Besides, the EPS also exhibited efficient decoloration and antioxidation activities, especially for EPS-S8, which might be due to the low Mw and specific monosaccharide composition.

Comparison of the efficiency and microbial mechanisms of chemical- and bio-surfactants in remediation of petroleum hydrocarbon

Surfactant-enhanced remediation (SER) is one of the most effective methods for petroleum hydrocarbon-contaminated sites compared to single physical and chemical methods. However, biosurfactants are not as commonly used as chemical surfactants, and the actual remediation effects and related mechanisms remain undefined. Therefore, to comprehensively compare the remediation effects and biological mechanisms of biosurfactants and chemical surfactants, soil column leaching experiments including two biosurfactants (rhamnolipids and lipopeptide) and three commercially used chemical surfactants (Tween 80, Triton X-100, and Berol 226SA) were conducted. After seven days of leaching, rhamnolipids exhibited the highest petroleum hydrocarbon removal rate of 61.01%, which was superior to that of chemical surfactants (11.73-18.75%) in n-alkanes C10-C30. Meanwhile, rhamnolipids exhibited a great degradation advantage of n-alkanes C13-C28, which was 1.22-30.55 times that of chemical surfactants. Compared to chemical surfactants, biosurfactants significantly upregulated the soil's biological functions, including soil conductivity (80.90-155.56%), and soil enzyme activities of lipase (90.31-497.10%), dehydrogenase (325.00-655.56%), core enzyme activities of petroleum hydrocarbon degradation, and quorum sensing between species. Biosurfactants significantly changed the composition of Pseudomonas, Citrobacter, Acidobacteriota, and Enterobacter at the genus level. Meanwhile, chemical surfactants had less influence on the bacterial community and interactions between species. Moreover, the biosurfactants enhanced the microbial interactions and centrality of petroleum hydrocarbon degraders in the community based on the network. Overall, this work provides a systematic comparison and understanding of the chemical- and bio-surfactants used in bioremediation. In the future, we intend to apply biosurfactants to practical petroleum hydrocarbon-contaminated fields to observe realistic remediation effects and compare their functional mechanisms.

Characterization of exopolysaccharide derived from Enterobacter ludwigii and its possible role as an emulsifier

Enterobacter ludwigii is an oral growing bacteria responsible for teeth blackening. It can form biofilm. The exopolysaccharide (EPS) cluster associated with biofilm formation was isolated using ethanol precipitation and the formaldehyde-sodium hydroxide method. The chemical characterization of EPS was done using UV spectroscopy, Fourier transforms infrared spectroscopy, and gas chromatography-mass spectrometry. Energy-dispersive X-ray spectroscopy (EDS) analysis of  EPS has revealed the presence of carbon > boron > nitrogen > phosphorous > calcium > sulfur > iron > potassium > magnesium. The carbon content was quite high (72.72-77.63%) in the EPS due to polysaccharide composition. The study showed the presence of different monosaccharides glucose (16.91%), galactose (4.25%), mannose (4.04%), and xylose (8.06%) as the major components of EPS. It appears such as thin filaments with three-dimensional structure, compact, irregular lumps and stacked flakes of polysaccharides. The EPS was also examined using different 1D, 2D Nuclear Magnetic Resonance (NMR) spectroscopy techniques (1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC) with different deuterated solvents (Protic and aprotic solvents for exchangeable protons), which showed eight distinguished monomers (seven confirmed by HSQC spectrum and one from 1H spectrum). Semi-crystalline nature and thermal stability were confirmed by X-ray diffractogram and differential scanning calorimetry analysis, respectively. The EPS further shows antioxidant potential in a concentration-dependent manner. It can form a stable emulsion against different edible oil that makes it promising alternative for use in food, and pharmaceutical industries.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03279-z.

Complete Genome Analysis of Rhodococcus opacus S8 Capable of Degrading Alkanes and Producing Biosurfactant Reveals Its Genetic Adaptation for Crude Oil Decomposition

Microorganisms capable of decomposing hydrophobic substrates in cold climates are of considerable interest both in terms of studying adaptive reactions to low temperatures and in terms of their application in biotechnologies for cleaning up oil spills in a crude-oil polluted soil. The aim of this work was to investigate the genome of Rhodococcus opacus S8 and explore behavior traits of this strain grown in the presence of hexadecane. The genome size of strain S8 is 8.78 Mb, of which the chromosome size is 7.75 Mb. The S8 strain contains 2 circular plasmids of 135 kb and 105 kb and a linear plasmid with a size of 788 kb. The analysis of the genome revealed the presence of genes responsible for the degradation of alkanes and synthesis of biosurfactants. The peculiarities of morphology of microbial cells when interacting with a hydrophobic substrate were revealed. An adaptive mechanism responsible in the absence of oxygen for maintaining the process of degradation of hexadecane is discussed. The data obtained show that the strain S8 has great potential to be used in biotechnologies.

Bioremediation of PAHs and heavy metals co-contaminated soils: Challenges and enhancement strategies

Systemic studies on the bioremediation of co-contaminated PAHs and heavy metals are lacking, and this paper provides an in-depth review on the topic. The released sources and transport of co-contaminated PAHs and heavy metals, including their co-occurrence through formation of cation-π interactions and their adsorption in soil are examined. Moreover, it is investigated that co-contamination of PAHs and heavy metals can drive a synergistic positive influence on bioremediation through enhanced secretion of extracellular polymeric substances (EPSs), production of biosynthetic genes, organic acid and enzymatic proliferation. However, PAHs molecular structure, PAHs-heavy metals bioavailability and their interactive cytotoxic effects on microorganisms can exert a challenging influence on the bioremediation under co-contaminated conditions. The fluctuations in bioavailability for microorganisms are associated with soil properties, chemical coordinative interactions, and biological activities under the co-contaminated PAHs-heavy metals conditions. The interactive cytotoxicity caused by the emergence of co-contaminants includes microbial cell disruption, denaturation of DNA and protein structure, and deregulation of antioxidant biological molecules. Finally, this paper presents the emerging strategies to overcome the bioavailability problems and recommends the use of biostimulation and bioaugmentation along with the microbial immobilization for enhanced bioremediation of PAHs-heavy metals co-contaminated sites. Better knowledge of the bioremediation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of PAHs and heavy metals co-contamination in the near future.

Structural Selectivity of PAH Removal Processes in Soil, and the Effect of Metal Co-Contaminants

Polycyclic aromatic hydrocarbons (PAHs) form a convenient structural series of molecules with which to examine the selectivity exerted on their removal by soil microbiota. It is known that there is an inverse relationship between PAH molecular size and degradation rates in soil. In this paper, we look at how the magnitude of the slope for this relationship, m, can be used as an indicator of the effect of metal co-contaminants on degradation rates across a range of PAH molecular weights. The analysis utilises data collected from our previous microcosm study (Deary, M.E.; Ekumankama, C.C.; Cummings, S.P. Development of a novel kinetic model for the analysis of PAH biodegradation in the presence of lead and cadmium co-contaminants. Journal of Hazard Materials 2016, 307, 240–252) in which we followed the degradation of the 16 US EPA PAHs over 40 weeks in soil microcosms taken from a high organic matter content woodland soil. The soil was amended with a PAH mixture (total concentration of 2166 mg kg−1) and with a range of metal co-contaminant concentrations (lead, up to 782 mg kg−1; cadmium up to 620 mg kg−1; and mercury up to 1150 mg kg−1). It was found that the magnitude of m increases in relation to the applied concentration of metal co-contaminant, indicating a more adverse effect on microbial communities that participate in the removal of higher molecular weight PAHs. We conclude that m is a useful parameter by which we might measure the differential effects of environmental contaminants on the PAH removal. Such information will be useful in planning and implementing remediation strategies.

Optimization and characterization of biosurfactant produced by indigenous Brevibacillus borstelensis isolated from a low permeability reservoir for application in MEOR

Biosurfactants are expected to be a key factor for microbial enhanced oil recovery (MEOR). In this study, we described the novel biosurfactant-producing strain Brevibacillus borstelensis YZ-2 isolated from a low permeability oil reservoir. We purified and characterized the biosurfactants produced by this YZ-2 strain via thin-layer chromatography and MALDI-TOF-MS, revealing them to be fengycins. We additionally used a Box–Behnken design approach to optimize fermentation conditions in order to maximize the biosurfactants production. Core flooding experiments showed that biosurfactants produced by YZ-2 can significantly enhance crude oil recovery. Micro-model tests showed that emulsification and IFT reduction was the main EOR mechanism of the YZ biosurfactant in the oil wet model. In summary, these findings highlight the potential of Brevibacillus borstelensis YZ-2 and its metabolites for MEOR.

Biosurfactants are expected to be a key factor for microbial enhanced oil recovery (MEOR).

How humic acid and Tween80 improve the phenanthrene biodegradation efficiency: Insight from cellular characteristics and quantitative proteomics

Polycyclic aromatic hydrocarbons (PAHs) are toxic and recalcitrant pollutants, with an urgent need for bioremediation. Systematic biodegradation studies show that surfactant-mediated bioremediation is still poorly understood. Here, we investigated a comprehensive cellular response pattern of the PAH degrading strain B. subtilis ZL09-26 to (non-)green surfactants at the cellular and proteomic levels. Eight characteristic cellular factor investigations and detailed quantitative proteomics analyses were performed to understand the highly enhanced phenanthrene (PHE) degradation efficiency (2.8- to 3-fold improvement) of ZL09-26 by humic acid (HA) or Tween80. The commonly upregulated pathway and proteins (Arginine generation, LacI-family transcriptional regulator, and Lactate dehydrogenase) and various metabolic pathways (such as phenanthrene degradation upstream pathway and central carbon metabolism) jointly govern the change of cellular behaviors and improvement of PHE transport, emulsification, and degradation in a network manner. The obtained molecular knowledge empowers engineers to expand the application of surfactants in the biodegradation of PAHs and other pollutants.

Performance and microbial community analysis of a bio-contact oxidation reactor during the treatment of low-COD and high-salinity oilfield produced water

The multistage bio-contact oxidation reactor (BCOR) is a widely used biological strategy to treat wastewater, however, little is known about the performance and microbial community information of BCOR during the treatment of low-COD and high-salinity oilfield produced water. In this study, the performance of a multistage BCOR in treating produced water was investigated. The result suggested the BCOR could efficiently remove COD, BOD₅, NH₄⁺-N, and oil pollutants. Besides, high-throughput sequencing analysis revealed that oil content was the main variable in shaping the community structure. The highest total relative abundance of potential pollutants degraders in first BCOR stage suggested significant role of this stage in pollutants removal. In addition, the correlation analysis disclosed the key functional genera during the degradation process, including Rhodobacter, Citreibacter, and Roseovarius. Moreover, network analysis revealed that the microbial taxa within same module had strong ecological linkages and specific functions.

Combined microbial degradation of crude oil under alkaline conditions by Acinetobacter baumannii and Talaromyces sp

The purpose of this work was to study the biodegradation of crude oil under alkaline condition by defined co-culture of Acinetobacter baumannii and Talaromyces sp. The n-alkanes in crude oil could be completely degraded by bacteria and fungi with the ratio of 1:1 at pH 9 in 14 d water simulation experiment. Meanwhile, the total degradation rate of crude oil could reach 80%. Fungi had stronger ability to degrade n-alkanes, while bacteria could better degrade other components such as aromatics and branched alkanes. The two strains were both capable of producing a small amount of biosurfactant. High cell viability was the main factor for strains to exert high degradation ability in alkaline environment. It was preliminarily verified that bacteria and fungi rely on the differences of enzyme systems to achieve synergy in the degradation process. These results indicated that the defined co-culture had great potential for bioremediation in alkaline soils.

Structure characterization, antioxidant and emulsifying capacities of exopolysaccharide derived from Pantoea alhagi NX-11

Pantoea alhagi exopolysaccharides (PAPS) have been shown to enhance crop resistance to abiotic stress. However, physicochemical properties and structure of PAPS have not yet been analyzed. In this study, two PAPSs, named PAPS1 and PAPS2, were isolated and purified from the P. alhagi NX-11. The results showed PAPS1 and PAPS2 were composed of glucose, galactose, glucuronic acid, glucosamine and mannose with average molecular weight of 1.326 × 10⁶ Da and 1.959 × 10⁶ Da, respectively. Moreover, the structure of PAPS1 and PAPS2 was investigated by FT-IR and NMR analysis. PAPS1 was identified to have the backbone structure of →4)-β-D-GlcpA-(1→2)-α-D-Galp-(1→3)-β-D-Galp-(1→3)-β-D-GlcpN- (1→3)-α-D-Galp-(1→3)-β-D-Galp-(1→. PAPS2 had the backbone structure of →4)-β-D-GlcpA-(1→2)-α-D-Galp-(1→3)-β-D-Glcp-(1→3)-β-D-GlcpN-(1→3)-α-D-Galp-(1→3)-α-D-GlcpN-(1→. In addition, PAPS1 and PAPS2 had moderate antioxidant and emulsifying capacities. Overall, the structure analysis of PAPS may point out the direction for the subsequent study of PAPS-mediated microbial and plant interactions, and further exploration of the application of PAPS.

Characterization of a biosurfactant producing electroactive Bacillus sp. for enhanced Microbial Fuel Cell dye decolourisation

A biosurfactant producing Gram positive bacterium isolated from anodic biofilm of textile wastewater fed MFC was identified as Bacillus sp. MFC (Accession number: MT322244). Scanning Electron Microscopy of the bacterium showed appendages, the bacterium forms biofilm on Congo red agar medium. The obtained results showed that the addition of 5 mg/l endogenous biosurfactant to the bacterial cells resulted in 19-fold increase in bacterial surface-bound exopolysaccharides (EPS) and 1.94-fold increase in biofilm. However, when the biosurfactant concentration increased to 20 and 40 mg/l, EPS and biofilm decreased and the cells lost their colony forming ability. The dielectric properties of the bacterial cells showed increase in conductivity and relative permittivity with increasing biosurfactant concentrations. The shape of the voltammogram currents peak, their location and Electrochemical impedance spectroscopy (EIS) suggest the involvement of biofilm as direct electron transfer pathway. The average voltage obtained was 0.65 V as compared to 0.45 V for the control MFC. Decolourization was tested for Congo red in a double chamber Microbial Fuel Cell (MFC), the results showed 2-fold increase in decolourization when biosurfactant is added post biofilm formation. The results confirm that Bacillus sp. MFC possess electrogenic properties and that adding low concentrations of endogenous biosurfactant to 24 h biofilm accelerates electron transfer by inducing perforations in the cell wall and increasing EPS as an electron transfer transient medium. Therefore, MFC performance can be enhanced.

Diversity of Metal-Resistant and Tensoactive-Producing Culturable Heterotrophic Bacteria Isolated from a Copper Mine in Brazilian Amazonia

Bacterial extracellular polymeric substances (EPSs) present diverse properties of biotechnological interest, such as surface modification, metal adsorption and hydrophobic substances solubilization through surface tension reduction. Thus, there is a growing demand for new producing strains and structurally variable biomolecules with different properties. One approach for scanning this biodiversity consists of exploring environments under selective pressures. The aim of this study was to evaluate the composition of culturable heterotrophic bacterial communities from five different sites from a copper mine in the Amazon biome by an enrichment technique to obtain metal resistant bacteria (lead, arsenic, cadmium, copper and zinc) capable of producing EPSs. The bacterial densities at the sites varied from 2.42 × 103 to 1.34 × 108 NMP mL-1 and the 77 bacterial isolates obtained were classified in four divisions, β-Proteobacteria (16.88%), γ-Proteobacteria (7.29%), Firmicutes (61%) and Actinobacteria (12.98%). Bacillus, Alcaligenes, and Lysinibacillus were the most dominant among the 16 observed genera, but the relative frequency of each varied according to the sample and the metal used in the enrichment culture. 58% of the bacterial strains (45) could produce EPSs. From these, 33 strains showed emulsifying activity (E24), and 9 of them reached values higher than 49%. Only Actinomyces viscosus E3.Pb5 and Bacillus subtilis group E3.As2 reduced the medium surface tension to values lower than 35 mN m-1. It was possible to confirm the high presence of bacteria capable of producing EPSs with tensoactive properties in Amazon copper mines and the evolutionary pressure exerted by the heavy metals during enrichment. These molecules can be tested as an alternative for use in processes that involve the removal of metals, such as the bioremediation of contaminated environments.

Assessing interactions, predicting function, and increasing degradation potential of a PAH-degrading bacterial consortium by effect of an inoculant strain

A natural phenanthrene-degrading consortium CON was inoculated with an exogenous strain Sphingobium sp. (ex Sp. paucimobilis) 20006FA yielding the consortium called I-CON, in order to study ecological interactions into the bacterial community. DGGE and proteomic profiles and analyses by HTS (High-Throughput Sequencing) technologies demonstrated inoculant establishment and changes on CON composition. Inoculation increased degradation efficiency in I-CON and prevented intermediate HNA accumulation. This could be explained not only by the inoculation, but also by enrichment in Achromobacter genus at expense of a decrease in Klebsiella genus. After inoculation, cooperation between Sphingobium and Achromobacter genera were improved, thereby, some competition could have been generated, and as a consequence, species in minor proportion (cheaters), as Inquilinus sp. and Luteibacter sp., were not detected. Sequences of Sphingobium (corresponding to the inoculated strain) did not vary. PICRUSt predicted a network with bacterial phylotypes connected with enzymes, showing functional redundancy in the phenanthrene pathway, with exception of the first enzymes biphenyl-2,3-diol 1,2-dioxygenase and protocatechuate 4,5-dioxygenase that were only encoded in Sphingobium sp. This is the first report where a natural consortium that has been characterized by HTS technologies is inoculated with an exogenous strain in order to study competitiveness and interactions.

Mechanism and Parameter Optimization of Fenton's Reagent Integrated with Surfactant Pretreatment to Improve Sludge Dewaterability

Sludge dewatering can effectively reduce the volume and mass of sludge for subsequent treatment and disposal. The work validated the potential of Fenton's reagent combined with dodecyl dimethyl benzyl ammonium chloride (DDBAC) in improving sludge dewaterability and proposed the mechanism of joint conditioning. The composite conditioner dosage was optimized using response surface methodology. Results indicated the good conditioning capability of the composite conditioners. The optimum dosages for H2O2, Fe2+, and DDBAC were 44.6, 39.6, and 71.0 mg/g, respectively, at which a sludge cake water content of 59.67% could be achieved. Moreover, a second-order polynomial equation was developed to describe the behavior of joint conditioning. Analysis of the reaction mechanism showed that Fenton oxidation effectively decomposed extracellular polymeric substance (EPS), including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), into dissolved organics, such as proteins and polysaccharides. The process facilitated the conversion of the bound water into free water. Furthermore, DDBAC further released the bound water through solubilization of TB-EPS and LB-EPS after the Fenton reaction. The bound water content of the sludge conditioned with Fenton's reagent decreased from 3.15 to 1.36 g/g and further decreased to 1.08 g/g with the addition of DDBAC. High-performance liquid chromatography analysis verified that the composite conditioning could oxidize and hydrolyze EPS into low-molecular-mass organics (e.g., formic and acetic acid), thereby facilitating the release of bound water.

Comparison of bacterial community characteristics between complete and shortcut denitrification systems for quinoline degradation

For quinoline-denitrifying degradation, very few researches focused on shortcut denitrification process and its bacterial community characteristics. In this study, complete and shortcut denitrification systems were constructed simultaneously for quinoline degradation. By calculation, specific quinoline removal rates were 0.905 and 1.123 g/(gVSS d), respectively, in the complete and shortcut systems, and the latter was 1.24 times of the former. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), high-throughput sequencing, and quantitative PCR (qPCR) techniques based on 16S rRNA were jointly applied to compare microbial community structures of two systems. Many denitrifying bacteria phyla, classes, and genera were detected in the two systems. Phylum Proteobacteria, Class Gammaproteobacteria, and Genus Alicycliphilus denitrificans were the dominant contributors for quinoline-denitrifying degradation. In the shortcut denitrification system, main and specific strains playing crucial roles were more; the species richness and the total abundance of functional genes (narG, nirS, nirK, and nosZ) were higher compared with the complete denitrification system. It could be supposed that inorganic-nitrogen reductase activity of bacterial community was stronger in the shortcut denitrification system, which was the intrinsic reason to result in higher denitrification rate.

The dissemination of multidrug-resistant Enterobacter cloacae throughout the UK and Ireland

Enterobacter cloacae is a clinically important Gram-negative member of the Enterobacteriaceae, which has increasingly been recognized as a major pathogen in nosocomial infections. Despite this, knowledge about the population structure and the distribution of virulence factors and antibiotic-resistance determinants of this species is scarce. In this study, we analysed a systematic collection of multidrug-resistant E. cloacae isolated between 2001 and 2011 from bloodstream infections across hospitals in the UK and Ireland. We found that the population is characterized by the presence of multiple clones formed at widely different time periods in the past. The clones exhibit a high degree of geographical heterogeneity, which indicates extensive dissemination of these E. cloacae clones across the UK and Ireland. These findings suggest that a diverse, community-based, commensal population underlies multidrug-resistant E. cloacae infections within hospitals.

Draft Genome Sequence of Hydrocarbon-Degrading Enterobacter cloacae Strain S1:CND1, Isolated from Crude Oil-Contaminated Soil from the Noonmati Oil Refinery, Guwahati, Assam, India

We report here the 4.57-Mb draft genome sequence of hydrocarbon-degrading Enterobacter cloacae strain S1:CND1 isolated from oil-contaminated soil in Guwahati, India. S1:CND1 contains 4,205 coding sequences and has a G+C content of 57.45%. This is the first report of the genome sequence of an E. cloacae adapted to an oil-contaminated environment.

Tributyltin chloride (TBTCl)-enhanced exopolysaccharide and siderophore production in an estuarine Alcaligenes faecalis strain

Tributyltin chloride (TBTCl) has been used extensively as an antifouling agent in ship paints, which results in the contamination of aquatic sites. These contaminated sites serve as enrichment areas for TBTCl-resistant bacterial strains. One TBTCl-resistant bacterial strain was isolated from the sediments of Zuari estuary, Goa, India, which is a major hub of various ship-building activities. Based on biochemical characteristics and 16S rDNA sequence analysis, this bacterial strain was identified as Alcaligenes faecalis and designated as strain SD5. It could degrade ≥3 mM TBTCl by using it as a sole carbon source and transform it into the less toxic dibutyltin chloride, which was confirmed by nuclear magnetic resonance and mass spectroscopy. Interestingly, this bacterial strain also showed enhanced exopolysaccharide and siderophore production when cells were exposed to toxic levels of TBTCl, suggesting their involvement in conferring resistance to this antifouling biocide as well as degradative capability respectively.

Microbial metabolism and community structure in response to bioelectrochemically enhanced remediation of petroleum hydrocarbon-contaminated soil

This study demonstrates that electrodes in a bioelectrochemical system (BES) can potentially serve as a nonexhaustible electron acceptor for in situ bioremediation of hydrocarbon contaminated soil. The deployment of BES not only eliminates aeration or supplement of electron acceptors as in contemporary bioremediation but also significantly shortens the remediation period and produces sustainable electricity. More interestingly, the study reveals that microbial metabolism and community structure distinctively respond to the bioelectrochemically enhanced remediation. Tubular BESs with carbon cloth anode (CCA) or biochar anode (BCA) were inserted into raw water saturated soils containing petroleum hydrocarbons for enhancing in situ remediation. Results show that total petroleum hydrocarbon (TPH) removal rate almost doubled in soils close to the anode (63.5-78.7%) than that in the open circuit positive controls (37.6-43.4%) during a period of 64 days. The maximum current density from the BESs ranged from 73 to 86 mA/m(2). Comprehensive microbial and chemical characterizations and statistical analyses show that the residual TPH has a strongly positive correlation with hydrocarbon-degrading microorganisms (HDM) numbers, dehydrogenase activity, and lipase activity and a negative correlation with soil pH, conductivity, and catalase activity. Distinctive microbial communities were identified at the anode, in soil with electrodes, and soil without electrodes. Uncommon electrochemically active bacteria capable of hydrocarbon degradation such as Comamonas testosteroni, Pseudomonas putida, and Ochrobactrum anthropi were selectively enriched on the anode, while hydrocarbon oxidizing bacteria were dominant in soil samples. Results from genus or phylum level characterizations well agree with the data from cluster analysis. Data from this study suggests that a unique constitution of microbial communities may play a key role in BES enhancement of petroleum hydrocarbons biodegradation in soils.

Isolation and characterization of a novel 2-methyl-4-chlorophenoxyacetic acid-degrading Enterobacter sp. strain SE08

A bacterial strain (SE08) capable of utilizing 2-methyl-4-chlorophenoxy acetic acid (MCPA) as the sole carbon and energy source for growth was isolated by continuous enrichment culturing in minimal salt medium (MSM) from a long term MCPA exposed soil. This bacterial strain was identified as Enterobacter sp. based on morphological, physiological and biochemical tests, as well as 16S rRNA sequence analysis. Its ability to degrade MCPA was determined using high performance liquid chromatography. The strain SE08 can tolerate unusually high MCPA concentrations (125-2000mg/L). The influences of culturing factors (initial concentration, pH, and temperature) on the bacterial growth and substrate degradation were studied. The results showed that the optimal MCPA degradation occurred at an MCPA concentration of 500mg/L, 30°C and pH 6.0. Under these conditions, 68.5 percent of MCPA in MSM was degraded by SE08, and the OD600nm reached 0.64 after culturing for 72h. The degradation of MCPA could be enhanced by addition of both carbon and nitrogen sources. At an initial MCPA concentration of 500mg/L, when 5g/L glucose and 2.5g/L yeast extract were added into the MSM media, the MCPA degradation was significantly increased to 83.8 percent, and OD600nm was increased to 1.09 after incubation at 30°C and pH 6.0 for 72h. This is the first study showing that an Enterobacter sp. strain is capable of degrading MCPA, which might provide a new approach for the remediation of MCPA contaminated soil and contribute to the limited knowledge about the function of Enterobacter species.

n-Alkane chain length alters Dietzia sp. strain DQ12-45-1b biosurfactant production and cell surface activity

Upon growth on n-hexadecane (C(16)), n-tetracosane (C(24)), and n-hexatriacontane (C(36)), Dietzia sp. strain DQ12-45-1b could produce different glycolipids, phospholipids, and lipopeptides. Interestingly, cultivation with C(36) increased cell surface hydrophobic activity, which attenuated the negative effect of the decline of the emulsification activity. These results suggest that the mechanisms of biosurfactant production and cell surface hydrophobicity are dependent upon the chain lengths of the n-alkanes used as carbon sources.

Environmental applications of biosurfactants: recent advances

Increasing public awareness of environmental pollution influences the search and development of technologies that help in clean up of organic and inorganic contaminants such as hydrocarbons and metals. An alternative and eco-friendly method of remediation technology of environments contaminated with these pollutants is the use of biosurfactants and biosurfactant-producing microorganisms. The diversity of biosurfactants makes them an attractive group of compounds for potential use in a wide variety of industrial and biotechnological applications. The purpose of this review is to provide a comprehensive overview of advances in the applications of biosurfactants and biosurfactant-producing microorganisms in hydrocarbon and metal remediation technologies.