Hydrocarbon Degradation Processes Research Articles

Phenotypic and genetic characterization of a lipolytic Ralstonia mannitolilytica isolate from petroleum-contaminated soil in Iraq.

Lipases play a crucial role in various industrial applications, and microbial lipases, particularly those from bacteria, possess significant properties. With increasing concerns about the environmental and health impacts of hydrocarbons from pipelines and refineries, there is a growing need to mitigate the risks associated with these compounds. In this study, 40 bacterial isolates were recovered from contaminated soil samples collected from multiple refineries across Iraq. Using the Vitek system, bacterial isolates were identified up to the species level, revealing that only 12 isolates exhibited lipase-producing capabilities. Among the lipase-producing isolates, Ralstonia mannitolilytica demonstrated the highest extracellular lipase activity, as determined by an olive oil plate assay supplemented with rhodamine B. Confirmation of the species identity was achieved through 16S rRNA gene sequencing, with the obtained sequence deposited under accession number LC772176.1. Further sequence analysis revealed single nucleotide polymorphisms (SNPs) in the genome of Ralstonia mannitolilytica strain H230303-10_N19_7x_R2 (CP011257.1, positions 1,311,102 and 1,311,457). Additionally, the presence of the lipase gene was confirmed through amplification and sequencing using a thermocycler PCR. Sequence analysis of the gene, aligned using Geneious Prime software, identified SNPs (CP010799, CP049132, AY364601, CP011257, and CP023537), and a phylogenetic tree was constructed based on genetic characterization. Our findings highlight the potential of Ralstonia mannitolilytica as a promising candidate for lipase production and contribute to our understanding of its genetic diversity and biotechnological applications in hydrocarbon degradation and industrial processes.

Genome features of a novel hydrocarbonoclastic Chryseobacterium oranimense strain and its comparison to bacterial oil-degraders and to other C. oranimense strains

Abstract For the first time, we report the whole genome sequence of a hydrocarbonoclastic Chryseobacterium oranimense strain isolated from Trinidad and Tobago (COTT) and its genes involved in the biotransformation of hydrocarbons and xenobiotics through functional annotation. The assembly consisted of 11 contigs with 2,794 predicted protein-coding genes which included a diverse group of gene families involved in aliphatic and polycyclic hydrocarbon degradation. Comparative genomic analyses with 18 crude-oil degrading bacteria in addition to two C. oranimense strains not associated with oil were carried out. The data revealed important differences in terms of annotated genes involved in the hydrocarbon degradation process that may explain the molecular mechanisms of hydrocarbon and xenobiotic biotransformation. Notably, many gene families were expanded to explain COTT’s competitive ability to manage habitat-specific stressors. Gene-based evidence of the metabolic potential of COTT supports the application of indigenous microbes for the remediation of polluted terrestrial environments and provides a genomic resource for improving our understanding of how to optimize these characteristics for more effective bioremediation.

Microbiologically influenced corrosion of steel in coastal surface seawater contaminated by crude oil

Petroleum-hydrocarbons spilt in surface seawater may pose potential threats to the corrosion of steel infrastructures. We show that crude oil accelerated steel corrosion mainly by accelerating microbiologically influenced corrosion (MIC). Crude oil led to the dominance of marine oil-degraders including Alcanivorax and Marinobacter in both seawater and steel rust, rather than sulfate-reducing bacteria (SRB) which dominated the rust microbial community in the no-oil group. Crude oil not only enhanced microbial oxygen respiration and aerobic hydrocarbon degradation but also nitrate reduction and anaerobic hydrocarbon degradation process in steel rust, indicating more heterogeneous microenvironments formed on steel surfaces. Furthermore, the low abundance of SRB and dissimilatory sulfate reduction gene (dsr), and the existence of iron-carbonate and iron-sulfate minerals implied that microbial sulfide, previously regarded as the main cause of MIC, was not the major contributor to steel corrosion in early petroleum-polluted seawater. Marine specialized oil-degraders seem to play more significant roles under such conditions.

Decontamination of Oil-Polluted Soils: Power of Electronic Bioinformatic Databases

The main idea was to solve the problem related to oil contamination of soil using bioremediation with bioaugmentation with modeled microorganism strains. The paper aimed to develop a bacterial consortium for petroleum hydrocarbon degradation during the biological treatment of oil-contaminated soils using electronic databases. The research methodology included an analysis of the mechanisms and metabolic pathways of petroleum hydrocarbon degradation and an assessment of the possible reaction modulus and enzymatic systems for the degradation of aromatic compounds. The taxonomic classification and review of oil compound transformation metabolic pathways were carried out using electronic KEGG, MetaCyc, and EzTaxon databases. The KEGG database was used to create a microbiological consortium of certain strains of bacteria that improved hydrocarbon degradation process performance. Identification of bacteria’s complete genome using Island Viewer 4 allowed to create of a consortium of oil-destructive bacteria consisting of such strains: Pseudoxanthomonas spadix BD-a59, Rhodococcus jostii RHA1, Rhodococcus aetherivorans IcdP1, Pseudomonas putida ND6, Pseudomonas stutzeri 19SMN4, Pseudomonas fluorescens UK4, Acinetobacter lactucae OTEC-02, Bacillus cereus F837/76.7.9. The ratio between the mentioned strains of microorganisms in the consortium was set at 20 % : 20 % : 15 % : 10 % : 10 % : 5 % : 5 % : 15 %. This bacterial consortium for aromatic hydrocarbons was created according to the metabolic information of basic enzymatic systems and the predominant transformation of particular oil compounds using the BacDive database.

Bacterial assemblages of urban microbiomes mobilized by runoff waters match land use typologies and harbor core species involved in pollutant degradation and opportunistic human infections

Cities are patchworks of urban catchments divided into functional units according to their commercial, residential and industrial activities, and socio-urbanistic patterns. The hypothesis of city surface microbiomes being structured by socio-urbanistic variables leading to an emergence of synurbic taxa was tested. According to the r/K microbial ecology theory, a gradient of well-adapted synurbic K-strategists and of opportunistic –r-strategists should occur over city surfaces. K-strategists would be core components while r-ones would be transiently detected. To resolve these patterns, sub-catchments (n = 21) of an area of high commercial and industrial activities were investigated over three time periods covering one year. The sub-catchments' land use patterns and associated human behaviors were converted into socio-urbanistic variables and groupings. Bacterial cells mobilized by runoffs per sub-catchment were recovered, and analyzed by classical approaches, microbial source tracking DNA assays and DNA meta-barcoding approaches. Relationships between these datasets, the runoff physico-chemical properties, and descriptors of the socio-urbanistic groupings were investigated. 16S rRNA meta-barcoding analyses showed evidence of the occurrence of K- and r-like strategists. Twenty-eight core genera were identified, and correlation networks revealed large bacterial modules organized around actinobacterial taxa involved in hydrocarbon degradation processes. Other bacterial networks were related to the occurrences of hygienic wastes, and involved bacteria originating from fecal contaminations. Several r-strategists like Sulfurospirillum were recorded and found associated to point source pollutions. The tpm-metabarcoding approach deciphered these r / K strategists at the species level among more than ten genera. Nine core K-like Pseudomomas species were identified. The P. aeruginosa human opportunistic pathogen and P. syringae phytopathogens were part of these K-strategists. Other tpm-harboring bacterial pathogens showed r-like opportunistic distribution patterns. Correlation network analyses indicated a strong incidence of hygienic wastes and hydrocarbon-pollutions on tpm-harboring bacteria. These analyses demonstrated the occurrence of core synurbic bacterial K-strategists over city surfaces.

Effects of 3,6-dichlorocarbazole on microbial ecology and its degradation in soil

The emerging contaminants polyhalogenated carbazoles (PHCZs) have been verified to be present in soils and sediments globally, and they show dioxin-like toxicity. However, there is a lack of soil ecological risk assessments on PHCZs despite their high detection rate and concentration in soils. The present study investigated the degradation and soil microbial influence of 3,6-dichlorocarbazole (3,6-DCCZ, a frequently detected PHCZ) in soil. The results showed that the half-lives of 3,6-DCCZ at concentrations of 0.100 mg/kg and 1.00 mg/kg were 7.75 d and 16.73 d, respectively. We found that 3,6-DCCZ was transformed into 3-chlorocarbazole (3-CCZ) by dehalogenation in soil. Additionally, intermediate products with higher molecular weights were detected, presumably because the -H on the carbazole ring was replaced by -CH3, -CH2-O-CH3, or -CH2-O-CH2CH3. 3,6-DCCZ exposure slightly increased the soil bacterial abundance and diversity and clearly changed the soil bacterial community structure. Through a comprehensive analysis of FAPROTAX, functional gene qPCR and soil enzyme tests, we concluded that 3,6-DCCZ exposure inhibited nitrification and nitrogen fixation but promoted denitrification, carbon dioxide fixation and hydrocarbon degradation processes in soil. This study provides valuable data for clarifying the PHCZ ecological risk in soil.

Metagenome-assembled genome (MAG) of Oceancaulis alexandrii NP7 isolated from Mediterranean Sea polluted marine sediments and its bioremediation potential.

Oceanicaulis alexandrii strain NP7 is a marine bacterium which belongs to the Hyphomonadaceae family and was isolated from sediments highly contaminated with metals and polycyclic aromatic hydrocarbons released for decades by industrial activities in the Gulf of Naples (Mediterranean Sea). Here, we report the partial genome sequence and annotation of O. alexandrii strain NP7 that contains a chromosome of 2,954,327 bp and encodes for 2914 predicted coding sequences (CDSs) and 44 RNA-encoding genes. Although the presence of some CDSs for genes involved in hydrocarbon degradation processes (e.g., alkB) have already been described in the literature associated with the Oceanicaulis, this is the first time that more than 100 genes involved in metal detoxification processes and hydrocarbon degradation are reported belonging to this genus. The presence of a heterogeneous set of genes involved in stress response, hydrocarbon degradation, heavy metal resistance, and detoxification suggests a possible role for O. alexandrii NP7 in the bioremediation of these highly contaminated marine sediments.

Removal of crude oil by Thiobacillus sp. and Clostridium sp. at various temperatures and concentration of pollutant in liquid media

The activities of the petroleum mining industry in Indonesia have caused many problems by producing hazardous waste pollution that would produce dangers for plants, animals or human lives. One technique to recover environmental situation is through land farming technique. The purpose of this study is to overcome crude oil pollution in the environment by using biotechnology method through the process of enzymatic bioremediation. The parameters discussed to determine the optimal environmental conditions that provide the highest efficiency for Total Petroleum Hydrocarbon (TPH) degradation processes such as temperature with a variation of 25 – 45°C then the concentration of pollutants with a variation of 5% – 20%, and the contact time carried out in solid media with variations amounting to 3 – 21 days. After conducting research, research that produces the bacterium Thiobacillus sp. and Clostridium sp. under optimal conditions at 35°C with a pollutant concentration of 10% and a contact time of 14 days. Thus, it can be concluded that the bacterium Thiobacillus sp. and Clostridium sp. can set aside hydrocarbon compounds with a removal efficiency of 65%. So, this research needs to be done to study other physical parameters.

Syntrophic Hydrocarbon Degradation in a Decommissioned Off-Shore Subsea Oil Storage Structure.

Over the last decade, metagenomic studies have revealed the impact of oil production on the microbial ecology of petroleum reservoirs. However, despite their fundamental roles in bioremediation of hydrocarbons, biocorrosion, biofouling and hydrogen sulfide production, oil field and oil production infrastructure microbiomes are poorly explored. Understanding of microbial activities within oil production facilities is therefore crucial for environmental risk mitigation, most notably during decommissioning. The analysis of the planktonic microbial community from the aqueous phase of a subsea oil-storage structure was conducted. This concrete structure was part of the production platform of the Brent oil field (North Sea), which is currently undergoing decommissioning. Quantification and sequencing of microbial 16S rRNA genes, metagenomic analysis and reconstruction of metagenome assembled genomes (MAGs) revealed a unique microbiome, strongly dominated by organisms related to Dethiosulfatibacter and Cloacimonadetes. Consistent with the hydrocarbon content in the aqueous phase of the structure, a strong potential for degradation of low molecular weight aromatic hydrocarbons was apparent in the microbial community. These degradation pathways were associated with taxonomically diverse microorganisms, including the predominant Dethiosulfatibacter and Cloacimonadetes lineages, expanding the list of potential hydrocarbon degraders. Genes associated with direct and indirect interspecies exchanges (multiheme type-C cytochromes, hydrogenases and formate/acetate metabolism) were widespread in the community, suggesting potential syntrophic hydrocarbon degradation processes in the system. Our results illustrate the importance of genomic data for informing decommissioning strategies in marine environments and reveal that hydrocarbon-degrading community composition and metabolisms in man-made marine structures might differ markedly from natural hydrocarbon-rich marine environments.

Bioremediasi Tanah Terkontaminasi Hidrokarbon Menggunakan Teknik Bioaugmentasi

Among various bioremediation methods, bioaugmentation is the one which frequently used. In this study, bioaugmentation was conducted by utilising Pseudomonas aeruginosa, Bacillus cereus, and Brevibacterium flavum. Many studies on and implementations of this method have been conducted. However, this method still needed to be studied especially with reference to its implementations to small automotive workshops, which their number was increasing, as the sources of the soil contamination. The objective of this study was to identify the most effective bacteria in removing total hydrocarbon content (TPH) from contaminated soils and to understanding several characteristics of the method. Laboratory research was set up and the experimental design was complete randomised design (CRD) with three replications. Statistical test of Anova with α 5% was carried out to evaluate the results of the study. The treatments of this study were three species of bacteria which were inoculated separately into the contaminated soils. The parameters were TPH, pH and the density of bacteria consortiums. The highest effective removal of TPH was showed by P. aeruginosa, 64,1% (δ+2,61%), followed by B. flavum and B cereus. This treatment had pH dropped two points and the density of bacteria consortium increased 6-10 times. The main limitation of this study was the number of parameters which was a few resulting difficulties in understanding the hydrocarbon degradation processes. The results of this study may give significant contributions to managers of small automotive workshops in cities which currently are not managed their spills properly.

Metagenomic Profiling and Microbial Metabolic Potential of Perdido Fold Belt (NW) and Campeche Knolls (SE) in the Gulf of Mexico

The Gulf of Mexico (GoM) is a particular environment that is continuously exposed to hydrocarbon compounds that may influence the microbial community composition. We carried out a metagenomic assessment of the bacterial community to get an overall view of this geographical zone. We analyzed both taxonomic and metabolic markers profiles to explain how the indigenous GoM microorganims participate in the biogeochemical cycling. Two geographically distant regions in the GoM, one in the north-west (NW) and one in the south-east (SE) of the GoM were analyzed and showed differences in their microbial composition and metabolic potential. These differences provide evidence the delicate equilibrium that sustains microbial communities and biogeochemical cycles. Based on the taxonomy and gene groups, the NW are more oxic sediments than SE ones, which have anaerobic conditions. Both water and sediments show the expected sulfur, nitrogen, and hydrocarbon metabolism genes, with particularly high diversity of the hydrocarbon-degrading ones. Accordingly, many of the assigned genera were associated with hydrocarbon degradation processes, Nitrospira and Sva0081 were the most abundant in sediments, while Vibrio, Alteromonas, and Alcanivorax were mostly detected in water samples. This basal-state analysis presents the GoM as a potential source of aerobic and anaerobic hydrocarbon degradation genes important for the ecological dynamics of hydrocarbons and the potential use for water and sediment bioremediation processes.

Keystone Species and Modularity in Microbial Hydrocarbon Degradation Uncovered by Network Analysis and Association Rule Mining.

Natural microbial communities in soils are highly diverse, allowing for rich networks of microbial interactions to unfold. Identifying key players in these networks is difficult as the distribution of microbial diversity at the local scale is typically non-uniform, and is the outcome of both abiotic environmental factors and microbial interactions. Here, using spatially resolved microbial presence-absence data along an aquifer transect contaminated with hydrocarbons, we combined co-occurrence analysis with association rule mining to identify potential keystone species along the hydrocarbon degradation process. Derived co-occurrence networks were found to be of a modular structure, with modules being associated with specific spatial locations and metabolic activity along the contamination plume. Association rules identify species that never occur without another, hence identifying potential one-sided cross-feeding relationships. We find that hub nodes in the rule network appearing in many rules as targets qualify as potential keystone species that catalyze critical transformation steps and are able to interact with varying partners. By contrasting analysis based on data derived from bulk samples and individual soil particles, we highlight the importance of spatial sample resolution. While individual inferred interactions are hypothetical in nature, requiring experimental verification, the observed global network patterns provide a unique first glimpse at the complex interaction networks at work in the microbial world.

Bacterial diversity in surface sediments from the continental shelf and slope of the North West gulf of Mexico and the presence of hydrocarbon degrading bacteria.

Bacteria play an important role in ecological processes in oil contaminated marine sediments. In this work, bacterial diversity studies with surface sediment samples from the NW Gulf of Mexico were performed, two from continental shelf and two from upper slope. The bacterial communities seem significantly influenced by depth, distance from the shoreline, temperature, dissolved oxygen and aluminum. The most abundant Phylum was Proteobacteria, Class Gammaproteobacteria. However, Class Deltaproteobacteria, Order Desulfuromonadales predominated in continental shelf and Order Alteromonadales (Gammaproteobacteria) prevailed in the upper slope sediments. Many potential hydrocarbon degrading bacterial genera were identified, 71 of the assigned genera were associated to hydrocarbon degradation processes. The genera Desulfobulbus and Haliea were confined to continental inner-shelf, while Shewanella and Fusibacter were mostly detected in deeper sediments. The occurrence and abundance of putative hydrocarbon degrading bacteria in this area, could be indicative of an impacted zone caused by the presence hydrocarbons in the environment.

Metagenomic Analysis of Subtidal Sediments from Polar and Subpolar Coastal Environments Highlights the Relevance of Anaerobic Hydrocarbon Degradation Processes.

In this work, we analyzed the community structure and metabolic potential of sediment microbial communities in high-latitude coastal environments subjected to low to moderate levels of chronic pollution. Subtidal sediments from four low-energy inlets located in polar and subpolar regions from both Hemispheres were analyzed using large-scale 16S rRNA gene and metagenomic sequencing. Communities showed high diversity (Shannon's index 6.8 to 10.2), with distinct phylogenetic structures (<40% shared taxa at the Phylum level among regions) but similar metabolic potential in terms of sequences assigned to KOs. Environmental factors (mainly salinity, temperature, and in less extent organic pollution) were drivers of both phylogenetic and functional traits. Bacterial taxa correlating with hydrocarbon pollution included families of anaerobic or facultative anaerobic lifestyle, such as Desulfuromonadaceae, Geobacteraceae, and Rhodocyclaceae. In accordance, biomarker genes for anaerobic hydrocarbon degradation (bamA, ebdA, bcrA, and bssA) were prevalent, only outnumbered by alkB, and their sequences were taxonomically binned to the same bacterial groups. BssA-assigned metagenomic sequences showed an extremely wide diversity distributed all along the phylogeny known for this gene, including bssA sensu stricto, nmsA, assA, and other clusters from poorly or not yet described variants. This work increases our understanding of microbial community patterns in cold coastal sediments, and highlights the relevance of anaerobic hydrocarbon degradation processes in subtidal environments.

[Bacterial Community Composition of Activated Sludge from Coking Wastewater].

Coking wastewater is a kind of highly toxic and refractory organic wastewater, and aerobic activated sludge, which is dominated by bacteria, determines the efficiency of coking wastewater treatment. However, the bacterial community structure of activated sludge from coking wastewater has rarely been reported. 454 sequencing technology was applied to investigate the structure and biodiversity of the bacterial community. The results of thermal cluster analysis and principal component analysis demonstrated the differences in biodiversities of different activated sludge bacterial communities. The bacterial communities were mainly composed of Proteobacteria, Planctomycetes, Acidobacteria, Candidatus Saccharibacteria, Bacteroidetes, Cyanobacteria, Actinobacteria, Chloroflexi, Firmicutes, Thaumarchaeota, Ignavibacteriae, Verrucomicrobia and Unclassified bacteria. Proteobacteria was the dominant phylum and its abundance was 36.00%-76.98%. The primary genera were Thiobacillus, Thauera, Comamonas, Caldimonas, Steroidobacter, Nitrosomonas, Phycisphaera and Gp4. Most of these genera were related with aromatic hydrocarbon degradation, nitrification and denitrification processes. These results provide a theoretical basis for removal mechanism of pollutants in coking wastewater.

Metagenome and Metatranscriptome Revealed a Highly Active and Intensive Sulfur Cycle in an Oil-Immersed Hydrothermal Chimney in Guaymas Basin.

The hydrothermal vent system is a typical chemosynthetic ecosystem in which microorganisms play essential roles in the geobiochemical cycling. Although it has been well-recognized that the inorganic sulfur compounds are abundant and actively converted through chemosynthetic pathways, the sulfur budget in a hydrothermal vent is poorly characterized due to the complexity of microbial sulfur cycling resulting from the numerous parties involved in the processes. In this study, we performed an integrated metagenomic and metatranscriptomic analysis on a chimney sample from Guaymas Basin to achieve a comprehensive study of each sulfur metabolic pathway and its hosting microorganisms and constructed the microbial sulfur cycle that occurs in the site. Our results clearly illustrated the stratified sulfur oxidation and sulfate reduction at the chimney wall. Besides, sulfur metabolizing is closely interacting with carbon cycles, especially the hydrocarbon degradation process in Guaymas Basin. This work supports that the internal sulfur cycling is intensive and the net sulfur budget is low in the hydrothermal ecosystem.

Pathways of α-methylstyrene Oxidation by P. aeruginosa DS-26

Today in world practice the biotechnological methods of cleaning of environment from oil and oil products are widely used. They based on the use of microorganisms-destructors that are able to utilize&lt;br /&gt;hydrocarbons. The microbial object of the research was bacterial strain &lt;em&gt;P. aeruginosa&lt;/em&gt; DS-26. This bacterial culture was isolated from sewage water of rubber industry. This strain was able to grow in a medium, which contained &lt;em&gt;α&lt;/em&gt;-methylstyrene. This compound, which is widely used as an active component in many industries, has a&lt;br /&gt;strong toxic effect on living organisms including humans. Different types of microbial metabolism play an important role in the hydrocarbon degradation process in the environment Metabolism of &lt;em&gt;α&lt;/em&gt;-methylstyrene by &lt;em&gt;P. aeruginosa&lt;/em&gt; DS-26 characterized by variety and in depth of carried out transformations. The analysis of the obtained data allowed offering two ways of oxidation of α-methylstyrene. The first way, primary, was accompanied by formation of products of the direct hydroxylation of aromatic ring - cis-2.3-dihydroxy-1-isopropenyl-6-cyclohexene and 3-isopropyl-catehol which are later metabolized by meta-pathway with formation of keto-acids. The next, secondary pathway came true through oxidation of α-phenylpropionic acid and 4-methylbenzene alcohol with formation of acetophenone as a final product.&lt;br /&gt;There are many researches that are devoted to study biochemical conversion of oil hydrocarbons. In order to utilize specific compounds as the only one source of carbon, microorganisms have to actively maintain a specific system of enzymes. Investigation of &lt;em&gt;α&lt;/em&gt;-methylstyrene degradation by &lt;em&gt;P. aeruginosa&lt;/em&gt; DS-&lt;br /&gt;26 enzymes has revealed specific enzymes that oxidize aromatic hydrocarbons. Investigation results of the studying strain enzymes can be confirmation of the proposed above scheme of primary α-methylstyrene metabolic pathway oxidized by &lt;em&gt;P. aeruginosa&lt;/em&gt; DS-26.

Microbial methane formation in deep aquifers of a coal-bearing sedimentary basin, Germany.

Coal-bearing sediments are major reservoirs of organic matter potentially available for methanogenic subsurface microbial communities. In this study the specific microbial community inside lignite-bearing sedimentary basin in Germany and its contribution to methanogenic hydrocarbon degradation processes was investigated. The stable isotope signature of methane measured in groundwater and coal-rich sediment samples indicated methanogenic activity. Analysis of 16S rRNA gene sequences showed the presence of methanogenic Archaea, predominantly belonging to the orders Methanosarcinales and Methanomicrobiales, capable of acetoclastic or hydrogenotrophic methanogenesis. Furthermore, we identified fermenting, sulfate-, nitrate-, and metal-reducing, or acetogenic Bacteria clustering within the phyla Proteobacteria, complemented by members of the classes Actinobacteria, and Clostridia. The indigenous microbial communities found in the groundwater as well as in the coal-rich sediments are able to degrade coal-derived organic components and to produce methane as the final product. Lignite-bearing sediments may be an important nutrient and energy source influencing larger compartments via groundwater transport.

Identification of the microbial community composition and structure of coal-mine wastewater treatment plants

The wastewater from coal-mine industry varies greatly and is resistant to biodegradation for containing large quantities of inorganic and organic pollutants. Microorganisms in activated sludge are responsible for the pollutants’ removal, whereas the microbial community composition and structure are far from understood. In the present study, the sludges from five coal-mine wastewater treatment plants were collected and the microbial communities were analyzed by Illumina high-throughput sequencing. The diversities of these sludges were lower than that of the municipal wastewater treatment systems. The most abundant phylum was Proteobacteria ranging from 63.64% to 96.10%, followed by Bacteroidetes (7.26%), Firmicutes (5.12%), Nitrospira (2.02%), Acidobacteria (1.31%), Actinobacteria (1.30%) and Planctomycetes (0.95%). At genus level, Thiobacillus and Comamonas were the two primary genera in all sludges, other major genera included Azoarcus, Thauera, Pseudomonas, Ohtaekwangia, Nitrosomonas and Nitrospira. Most of these core genera were closely related with aromatic hydrocarbon degradation and denitrification processes. Identification of the microbial communities in coal-mine wastewater treatment plants will be helpful for wastewater management and control.

Assessment of the Deepwater Horizon oil spill impact on Gulf coast microbial communities

One of the major environmental concerns of the Deepwater Horizon oil spill in the Gulf of Mexico was the ecological impact of the oil that reached shorelines of the Gulf Coast. Here we investigated the impact of the oil on the microbial composition in beach samples collected in June 2010 along a heavily impacted shoreline near Grand Isle, Louisiana. Successional changes in the microbial community structure due to the oil contamination were determined by deep sequencing of 16S rRNA genes. Metatranscriptomics was used to determine expression of functional genes involved in hydrocarbon degradation processes. In addition, potential hydrocarbon-degrading Bacteria were obtained in culture. The 16S data revealed that highly contaminated samples had higher abundances of Alpha- and Gammaproteobacteria sequences. Successional changes in these classes were observed over time, during which the oil was partially degraded. The metatranscriptome data revealed that PAH, n-alkane, and toluene degradation genes were expressed in the contaminated samples, with high homology to genes from Alteromonadales, Rhodobacterales, and Pseudomonales. Notably, Marinobacter (Gammaproteobacteria) had the highest representation of expressed genes in the samples. A Marinobacter isolated from this beach was shown to have potential for transformation of hydrocarbons in incubation experiments with oil obtained from the Mississippi Canyon Block 252 (MC252) well; collected during the Deepwater Horizon spill. The combined data revealed a response of the beach microbial community to oil contaminants, including prevalence of Bacteria endowed with the functional capacity to degrade oil.