Long-term sloping cultivation reduced core microbiota related to nitrogen fixation and soil hydrocarbon degradation.

Sloping farmland increases soil erosion, but little is known about how soil erosion impacts microbial structures and functions in sloping farmland. Using high-throughput sequencing, we conducted a six-year in-situ experiment with gradients of 0° (CK), 5° (S1), 10° (S2), and 15° (S3) to investigate the effects of sloping farmland on soil microbial diversities, compositions, and functions related to nitrogen and carbon resource acquisition. The results showed that the S1, S2, and S3 treatments significantly decreased SOM and NO3- levels by 33.0%∼47.3% and 37.0%∼49.6%, respectively, in comparison to the CK treatment. The S1, S2, and S3 treatments had similar impacts on diversities and compositions of bacterial and fungal communities. Moreover, the S1, S2, and S3 treatments had same enriched and depleted core microbiota. Long-term sloping cultivation filtered these core microbiota mainly by reducing SOM and NO3- and increasing AK and AP. Compared with the CK treatment, the S1, S2, and S3 treatments significantly reduced the relative abundances of potential functions of nitrogen fixation, hydrocarbon degradation, and fermentation by 46.9%∼54.5%, 74.7%∼83.5%, and 28.1%∼54.1%, respectively. Sloping treatments reduced functions related to nitrogen fixation and soil hydrocarbon degradation mainly because the loss of SOM reduced the relative abundances of core microbiota. Generally, long-term sloping cultivation reduced core microbiota related to nitrogen fixation and soil hydrocarbon degradation mainly due to the loss of SOM. Our findings provided implications for the management and reclamation of sloping farmland.

Composition and metabolic flexibility of hydrocarbon-degrading consortia in oil reservoirs.

Hydrocarbon-degrading consortia (HDC) play an important role in petroleum exploitation. However, the real composition and metabolic mechanism of HDC in the microbial enhanced oil recovery (MEOR) process remain unclear. By combining 13C-DNA stable isotope probing microcosms with metagenomics, some newly reported phyla, including Chloroflexi, Synergistetes, Thermotogae, and Planctomycetes, dominated the HDC in the oil reservoirs. In the field trials, the HDC in the aerobic-facultative-anaerobic stage of oilfields jointly promoted the MEOR process, with monthly oil increments of up to 189 tons. Pseudomonas can improve oil recovery by producing rhamnolipid in the facultative condition. Roseovarius was the novel taxa potentially oxidizing alkane and producing acetate to improve oil porosity and permeability in the aerobic condition. Ca. Bacteroidia were the new members potentially degrading hydrocarbons by fumarate addition in the anaerobic environment. Comprehensive identification of the active HDC in oil reservoirs provides a novel theoretical basis for oilfield regulatory scheme.

Cascading sulfur cycling in simulated oil sands pit lake water cap mesocosms transitioning from oxic to euxinic conditions.

Base Mine Lake (BML), the first full-scale demonstration of oil sands tailings pit lake reclamation technology, is experiencing expansive, episodic hypolimnetic euxinia resulting in greater sulfur biogeochemical cycling within the water cap. Here, Fluid Fine Tailings (FFT)-water mesocosm experiments simulating the in situ BML summer hypolimnetic oxic-euxinic transition determined sulfur biogeochemical processes and their controlling factors. While mesocosm water caps without FFT amendments experienced limited geochemical and microbial changes during the experimental period, FFT-amended mesocosm water caps evidenced three successive stages of S speciation in ∼30 days: (S1) rising expansion of water cap euxinia from FFT to water surface; enabling (S2) rapid sulfate (SO42-) reduction and sulfide production directly within the water column; fostering (S3) generation and subsequent consumption of sulfur oxidation intermediate compounds (SOI). Identified key SOI, elemental S and thiosulfate, support subsequent SOI oxidation, reduction, and/or disproportionation processes in the system. Dominant water cap microbes shifted from methanotrophs and denitrifying/iron-reducing bacteria to functionally versatile sulfur-reducing bacteria (SRB) comprising sulfate-reducing bacteria (Desulfovibrionales) and SOI-reducing/disproportionating bacteria (Campylobacterales and Desulfobulbales). The observed microbial shift is driven by decreasing [SO42-] and organic aromaticity, with putative hydrocarbon-degrading bacteria providing electron donors for SRB. Comparison between unsterile and sterile water treatments further underscores the biogeochemical readiness of the in situ water cap to enhance oxidant depletion, euxinia expansion and establishment of water cap SRB communities aided by FFT migration of anaerobes. Results here identify the collective influence of FFT and water cap microbial communities on water cap euxinia expansion associated with sequential S reactions that are controlled by concentrations of oxidants, labile organic substrates and S species. This emphasizes the necessity of understanding this complex S cycling in assessing BML water cap O2 persistence.

High Arctic seawater and coastal soil microbiome co-occurrence and composition structure and their potential hydrocarbon biodegradation.

The accelerated decline in Arctic sea-ice cover and duration is enabling the opening of Arctic marine passages and improving access to natural resources. The increasing accessibility to navigation and resource exploration and production brings risks of accidental hydrocarbon releases into Arctic waters, posing a major threat to Arctic marine ecosystems where oil may persist for many years, especially in beach sediment. The composition and response of the microbial community to oil contamination on Arctic beaches remain poorly understood. To address this, we analyzed microbial community structure and identified hydrocarbon degradation genes among the Northwest Passage intertidal beach sediments and shoreline seawater from five high Arctic beaches. Our results from 16S/18S rRNA genes, long-read metagenomes, and metagenome-assembled genomes reveal the composition and metabolic capabilities of the hydrocarbon microbial degrader community, as well as tight cross-habitat and cross-kingdom interactions dominated by lineages that are common and often dominant in the polar coastal habitat, but distinct from petroleum hydrocarbon-contaminated sites. In the polar beach sediment habitats, Granulosicoccus sp. and Cyclocasticus sp. were major potential hydrocarbon-degraders, and our metagenomes revealed a small proportion of microalgae and algal viruses possessing key hydrocarbon biodegradative genes. This research demonstrates that Arctic beach sediment and marine microbial communities possess the ability for hydrocarbon natural attenuation. The findings provide new insights into the viral and microalgal communities possessing hydrocarbon degradation genes and might represent an important contribution to the removal of hydrocarbons under harsh environmental conditions in a pristine, cold, and oil-free environment that is threatened by oil spills.

Novel, active, and uncultured hydrocarbon-degrading microbes in the ocean.

Given the vast quantity of oil and gas input to the marine environment annually, hydrocarbon degradation by marine microorganisms is an essential ecosystem service. Linkages between taxonomy and hydrocarbon degradation capabilities are largely based on cultivation studies, leaving a knowledge gap regarding the intrinsic ability of uncultured marine microbes to degrade hydrocarbons. To address this knowledge gap, metagenomic sequence data from the Deepwater Horizon (DWH) oil spill deep-sea plume was assembled to which metagenomic and metatranscriptomic reads were mapped. Assembly and binning produced new DWH metagenome-assembled genomes that were evaluated along with their close relatives, all of which are from the marine environment (38 total). These analyses revealed globally distributed hydrocarbon-degrading microbes with clade-specific substrate degradation potentials that have not been reported previously. For example, methane oxidation capabilities were identified in all Cycloclasticus. Furthermore, all Bermanella encoded and expressed genes for non-gaseous n-alkane degradation; however, DWH Bermanella encoded alkane hydroxylase, not alkane 1-monooxygenase. All but one previously unrecognized DWH plume member in the SAR324 and UBA11654 have the capacity for aromatic hydrocarbon degradation. In contrast, Colwellia were diverse in the hydrocarbon substrates they could degrade. All clades encoded nutrient acquisition strategies and response to cold temperatures, while sensory and acquisition capabilities were clade specific. These novel insights regarding hydrocarbon degradation by uncultured planktonic microbes provides missing data, allowing for better prediction of the fate of oil and gas when hydrocarbons are input to the ocean, leading to a greater understanding of the ecological consequences to the marine environment.IMPORTANCEMicrobial degradation of hydrocarbons is a critically important process promoting ecosystem health, yet much of what is known about this process is based on physiological experiments with a few hydrocarbon substrates and cultured microbes. Thus, the ability to degrade the diversity of hydrocarbons that comprise oil and gas by microbes in the environment, particularly in the ocean, is not well characterized. Therefore, this study aimed to utilize non-cultivation-based 'omics data to explore novel genomes of uncultured marine microbes involved in degradation of oil and gas. Analyses of newly assembled metagenomic data and previously existing genomes from other marine data sets, with metagenomic and metatranscriptomic read recruitment, revealed globally distributed hydrocarbon-degrading marine microbes with clade-specific substrate degradation potentials that have not been previously reported. This new understanding of oil and gas degradation by uncultured marine microbes suggested that the global ocean harbors a diversity of hydrocarbon-degrading bacteria, which can act as primary agents regulating ecosystem health.

Cultivation of novel Atribacterota from oil well provides new insight into their diversity, ecology, and evolution in anoxic, carbon-rich environments.

BACKGROUND: The Atribacterota are widely distributed in the subsurface biosphere. Recently, the first Atribacterota isolate was described and the number of Atribacterota genome sequences retrieved from environmental samples has increased significantly; however, their diversity, physiology, ecology, and evolution remain poorly understood. RESULTS: We report the isolation of the second member of Atribacterota, Thermatribacter velox gen. nov., sp. nov., within a new family Thermatribacteraceae fam. nov., and the short-term laboratory cultivation of a member of the JS1 lineage, Phoenicimicrobium oleiphilum HX-OS.bin.34TS, both from a terrestrial oil reservoir. Physiological and metatranscriptomics analyses showed that Thermatribacter velox B11T and Phoenicimicrobium oleiphilum HX-OS.bin.34TS ferment sugars and n-alkanes, respectively, producing H2, CO2, and acetate as common products. Comparative genomics showed that all members of the Atribacterota lack a complete Wood-Ljungdahl Pathway (WLP), but that the Reductive Glycine Pathway (RGP) is widespread, indicating that the RGP, rather than WLP, is a central hub in Atribacterota metabolism. Ancestral character state reconstructions and phylogenetic analyses showed that key genes encoding the RGP (fdhA, fhs, folD, glyA, gcvT, gcvPAB, pdhD) and other central functions were gained independently in the two classes, Atribacteria (OP9) and Phoenicimicrobiia (JS1), after which they were inherited vertically; these genes included fumarate-adding enzymes (faeA; Phoenicimicrobiia only), the CODH/ACS complex (acsABCDE), and diverse hydrogenases (NiFe group 3b, 4b and FeFe group A3, C). Finally, we present genome-resolved community metabolic models showing the central roles of Atribacteria (OP9) and Phoenicimicrobiia (JS1) in acetate- and hydrocarbon-rich environments. CONCLUSION: Our findings expand the knowledge of the diversity, physiology, ecology, and evolution of the phylum Atribacterota. This study is a starting point for promoting more incisive studies of their syntrophic biology and may guide the rational design of strategies to cultivate them in the laboratory. Video Abstract.

Genomic sequence of three hydrocarbonoclastic pseudomonadaceae strains isolated from marine sediments of the port of Rosarito, Baja California, Mexico.

We report the draft genome sequence of three marine bacteria belonging to Pseudomonas and Stutzerimonas genera, with hydrocarbonoclastic metabolism for oil and monoaromatic hydrocarbon degradation. The genomic information of these organisms contributes to the knowledge of natural and polluted marine environments with ubiquitous presence of hydrocarbons as a selective pressure.

Driving mechanisms for the adaptation and degradation of petroleum hydrocarbons by native microbiota from seas prone to oil spills.

Offshore waters have a high incidence of oil pollution, which poses an elevated risk of ecological damage. The microbial community composition and metabolic mechanisms influenced by petroleum hydrocarbons vary across different marine regions. However, research on metabolic strategies for in-situ petroleum degradation and pollution adaptation remains in its nascent stages. This study combines metagenomic techniques with gas chromatography-mass spectrometry (GC-MS) analysis. The data show that the genera Pseudoalteromonas, Hellea, Lentisphaera, and Polaribacter exhibit significant oil-degradation capacity, and that the exertion of their degradation capacity is correlated with nutrient and oil pollution stimuli. Furthermore, tmoA, badA, phdF, nahAc, and fadA were found to be the key genes involved in the degradation of benzene, polycyclic aromatic hydrocarbons, and their intermediates. Key genes (INSR, SLC2A1, and ORC1) regulate microbial adaptation to oil-contaminated seawater, activating oil degradation processes. This process enhances the biological activity of microbial communities and accounts for the geographical variation in their compositional structure. Our results enrich the gene pool for oil pollution adaptation and degradation and provide an application basis for optimizing bioremediation intervention strategies.

Laccase is a multitasking protein for synthetic gene circuits in the yeast Saccharomycescerevisiae.

Laccase is a multicopper oxidase enzyme that oxidizes a variety of substrates, including polyphenols and polycyclic aromatic hydrocarbons (PAHs). It catalyzes the four-electron reduction of molecular oxygen that results in the production of water as a by-product. Thus, laccase can play an important role in environmental care. Previously, we have successfully expressed Trametes trogii laccase (TtLcc1) in the yeast Saccharomyces cerevisiae. In this work, we have expressed in yeast another laccase, LacA from Trametes sp. AH28-2, and tested its function on PAHs. Yeast cells engineered to produce the two laccases performed efficient PAH degradation. Both TtLcc1 and LacA led to the construction of spatiotemporal fluorescence-pulse generators when combined with a benzoate/salicylate yeast biosensor in a two-population system. Moreover, laccases returned a visual output signal in yeast synthetic circuits-upon reacting with ABTS (2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid)). Thus, in S. cerevisiae, laccases are a powerful alternative to fluorescent reporter proteins.

Characterization and identification of long-chain hydrocarbon-degrading bacterial communities in long-term chronically polluted soil in Ogoniland: an integrated approach using culture-dependent and independent methods.

Escalating oil consumption has resulted in an increase in accidental spills of petroleum hydrocarbons, causing severe environmental degradation, notably in vulnerable regions like the Niger Delta. Complex mixture of these hydrocarbons particularly long-chain alkanes presents unique challenges in restoration of polluted environment due to their chemical properties. This study aimed to investigate the long-chain hydrocarbon-degrading bacterial communities within long-term chronically polluted soil in Ogoniland, by utilizing both traditional cultivation methods and modern culture-independent techniques. Results revealed that surface-polluted soil (SPS) and subsurface soil (SPSS) exhibit significantly higher total organic carbon (TOC) ranging from 5.64 to 5.06% and total petroleum hydrocarbons (TPH) levels ranging from 36,775 ppm to 14,087 ppm, compared to unpolluted soil (UPS) with 1.97% TOC and 479 ppm TPH, respectively. Analysis of carbon chain lengths reveals the prevalence of longer-chain alkanes (C20-28) in the surface soil. Culture-dependent methods, utilizing crude oil enrichment (COE) and paraffin wax enrichment (PWE), yield 47 bacterial isolates subjected to a long-chain alkane degradation assay. Twelve bacterial strains demonstrate significant degradation abilities across all enriched media. Three bacterial members, namely Pseudomonas sp. (almA), Marinomonas sp. (almA), and Alteromonas (ladA), exhibit genes responsible for long-chain alkane degradation, demonstrating efficiency between 50 and 80%. Culture-independent analysis reveals that surface SPS samples exhibit greater species richness and diversity compared to subsurface SPSS samples. Proteobacteria dominates as the phylum in both soil sample types, ranging from 22.23 to 82.61%, with Firmicutes (0.2-2.22%), Actinobacteria (0.4-3.02%), and Acidobacteria (0.1-3.53%) also prevalent. Bacterial profiles at genus level revealed that distinct variations among bacterial populations between SPS and SPSS samples comprising number of hydrocarbon degraders and the functional predictions also highlight the presence of potential catabolic genes (nahAa, adh2, and cpnA) in the polluted soil. However, culture-dependent analysis only captured a few of the dominant members found in culture-independent analysis, implying that more specialized media or environments are needed to isolate more bacterial members. The findings from this study contribute valuable information to ecological and biotechnological aspects, aiding in the development of more effective bioremediation applications for restoring oil-contaminated environments.

Diversity links to functionality: Unraveling the impact of pressure disruption and culture medium on crude oil-enriched microbial communities from the deep Eastern Mediterranean Sea.

Mesopelagic water from the deep Eastern Mediterranean Sea (EMS) was collected under disrupted (REPRESS) or undisturbed (HP) pressure conditions and was acclimated to oil (OIL) or dispersed-oil (DISPOIL) under in situ pressure and temperature (10 MPa, 14 °C). Decompression resulted in oil-acclimatised microbial communities of lower diversity despite the restoration of in situ pressure conditions during the 1-week incubation. Further biodiversity loss was observed when oil-acclimatised communities were transferred to ONR7 medium to facilitate the isolation of oil-degrading bacteria. Microbial diversity loss impacted the degradation of recalcitrant oil compounds, especially PAHs, as low-abundance taxa, linked with PAH degradation, were outcompeted in the enrichment process. Thalassomonas, Pseudoalteromonas, Halomonas and Alcanivorax were enriched in ONR7 under all experimental conditions. No effect of dispersant application on the microbial community structure was identified. A. venustensis was isolated under all tested conditions suggesting a potential key role of this species in hydrocarbons removal in the deep EMS.

Urea amendment decouples nitrification in hydrocarbon contaminated Antarctic soil.

Hydrocarbon contaminated soils resulting from human activities pose a risk to the natural environment, including in the Arctic and Antarctic. Engineered biopiles constructed at Casey Station, Antarctica, have proven to be an effective strategy for remediating hydrocarbon contaminated soils, with active ex-situ remediation resulting in significant reductions in hydrocarbons, even in the extreme Antarctic climate. However, the use of urea-based fertilisers, whilst providing a nitrogen source for bioremediation, has also altered the natural soil chemistry leading to increases in pH, ammonium and nitrite. Monitoring of the urea amended biopiles identified rising levels of nitrite to be of particular interest, which misaligns with the long term goal of reducing contaminant levels and returning soil communities to a 'healthy' state. Here, we combine amplicon sequencing, microfluidic qPCR on field samples and laboratory soil microcosms to assess the impact of persistent nitrite accumulation (up to 60 months) on nitrifier abundances observed within the Antarctic biopiles. Differential inhibition of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) Nitrobacter and Nitrospira in the cold, urea treated, alkaline soils (pH 8.1) was associated with extensive nitrite accumulation (76 ± 57 mg N/kg at 60 months). When the ratio of Nitrospira:AOB dropped below ∼1:1, Nitrobacter was completely inhibited or absent from the biopiles, and nitrite accumulated. Laboratory soil microcosms (incubated at 7 °C and 15 °C for 9 weeks) reproduced the pattern of nitrite accumulation in urea fertilized soil at the lower temperature, consistent with our longer-term observations from the Antarctic biopiles, and with other temperature-controlled microcosm studies. Diammonium phosphate amended soil did not exhibit nitrite accumulation, and could be a suitable alternative biostimulant to avoid excessive nitrite build-up.

Broad-spectrum hydrocarbon-degrading microbes in the global ocean metagenomes.

Understanding the diversity and functions of hydrocarbon-degrading microorganisms in marine environments is crucial for both advancing knowledge of biogeochemical processes and improving bioremediation methods. In this study, we leveraged nearly 20,000 metagenome-assembled genomes (MAGs), recovered from a wide array of marine samples across the global oceans, to map the diversity of aerobic hydrocarbon-degrading microorganisms. A broad bacterial diversity was uncovered, with a notable preference for degrading aliphatic hydrocarbons over aromatic ones, primarily within Proteobacteria and Actinobacteriota. Three types of broad-spectrum hydrocarbon-degrading bacteria were identified for their ability to degrade various hydrocarbons and possession of multiple copies of hydrocarbon biodegradation genes. These bacteria demonstrate extensive metabolic versatility, aiding their survival and adaptability in diverse environmental conditions. Evidence of gene duplication and horizontal gene transfer in these microbes suggested a potential enhancement in the diversity of hydrocarbon-degrading bacteria. Positive correlations were observed between the abundances of hydrocarbon-degrading genes and environmental parameters such as temperature (-5 to 35 °C) and salinity (20 to 42 PSU). Overall, our findings offer valuable insights into marine hydrocarbon-degrading microorganisms and suggest considerations for selecting microbial strains for oil pollution remediation.

Fulvic acid more facilitated the soil electron transfer than humic acid.

Humus substances (HSs) participate in extracellular electron transfer (EET), which is unclear in heterogeneous soil. Here, a microbial electrochemical system (MES) was constructed to determine the effect of HSs, including humic acid, humin and fulvic acid, on soil electron transfer. The results showed that fulvic acid led to the optimal electron transfer efficiency in soil, as evidenced by the highest accumulated charges and removal of total petroleum hydrocarbons after 140 days, with increases of 161% and 30%, respectively, compared with those of the control. However, the performance of MES with the addition of humic acid and humin was comparable to that of the control. Fulvic acid amendment enhanced the carboxyl content and oxidative state of dissolved organic matter, endowing a better electron transfer capacity. Additionally, the presence of fulvic acid induced an increase in the abundance of electroactive bacteria and organic degraders, extracellular polymeric substances and functional enzymes such as cytochrome c and NADH synthesis, and the expression of m tr C gene, which is responsible for EET enhancement in soil. Overall, this study reveals the mechanism by which HSs stimulate soil electron transfer at the physicochemical and biological levels and provides basic support for the application of bioelectrochemical technology in soil.

Diverse hydrocarbon degradation genes, heavy metal resistome, and microbiome of a fluorene-enriched animal-charcoal polluted soil.

Environmental compartments polluted with animal charcoal from the skin and hide cottage industries are rich in toxic heavy metals and diverse hydrocarbon classes, some of which are carcinogenic, mutagenic, and genotoxic, and thus require a bio-based eco-benign decommission strategies. A shotgun metagenomic approach was used to decipher the microbiome, hydrocarbon degradation genes, and heavy metal resistome of a microbial consortium (FN8) from an animal-charcoal polluted site enriched with fluorene. Structurally, the FN8 microbial consortium consists of 26 phyla, 53 classes, 119 orders, 245 families, 620 genera, and 1021 species. The dominant phylum, class, order, family, genus, and species in the consortium are Proteobacteria (51.37%), Gammaproteobacteria (39.01%), Bacillales (18.09%), Microbulbiferaceae (11.65%), Microbulbifer (12.21%), and Microbulbifer sp. A4B17 (19.65%), respectively. The microbial consortium degraded 57.56% (28.78 mg/L) and 87.14% (43.57 mg/L) of the initial fluorene concentration in 14 and 21 days. Functional annotation of the protein sequences (ORFs) of the FN8 metagenome using the KEGG GhostKOALA, KofamKOALA, NCBI's conserved domain database, and BacMet revealed the detection of hydrocarbon degradation genes for benzoate, aminobenzoate, polycyclic aromatic hydrocarbons (PAHs), chlorocyclohexane/chlorobenzene, chloroalkane/chloroalkene, toluene, xylene, styrene, naphthalene, nitrotoluene, and several others. The annotation also revealed putative genes for the transport, uptake, efflux, and regulation of heavy metals such as arsenic, cadmium, chromium, mercury, nickel, copper, zinc, and several others. Findings from this study have established that members of the FN8 consortium are well-adapted and imbued with requisite gene sets and could be a potential bioresource for on-site depuration of animal charcoal polluted sites.

Bioremediation of hydrocarbon by co-culturing of biosurfactant-producing bacteria in microbial fuel cell with Fe2O3-modified anode.

The most common type of environmental contamination is petroleum hydrocarbons. Sustainable and environmentally friendly treatment strategies must be explored in light of the increasing challenges of toxic and critical wastewater contamination. This paper deals with the bacteria-producing biosurfactant and their employment in the bioremediation of hydrocarbon-containing waste through a microbial fuel cell (MFC) with Pseudomonas aeruginosa (exoelectrogen) as co-culture for simultaneous power generation. Staphylococcus aureus is isolated from hydrocarbon-contaminated soil and is effective in hydrocarbon degradation by utilizing hydrocarbon (engine oil) as the only carbon source. The biosurfactant was purified using silica-gel column chromatography and characterised through FTIR and GCMS, which showed its glycolipid nature. The isolated strains are later employed in the MFCs for the degradation of the hydrocarbon and power production simultaneously which has shown a power density of 6.4 W/m3 with a 93% engine oil degradation rate. A biogenic Fe2O3 nanoparticle (NP) was synthesized using Bambusa arundinacea shoot extract for anode modification. It increased the power output by 37% and gave the power density of 10.2 W/m3. Thus, simultaneous hydrocarbon bioremediation from oil-contamination and energy recovery can be achieved effectively in MFC with modified anode.

Depletion of hydrocarbons and concomitant shift in bacterial community structure of a diesel-spiked tropical agricultural soil.

Bacterial community of a diesel-spiked agricultural soil was monitored over a 42-day period using the metagenomic approach in order to gain insight into key phylotypes impacted by diesel contamination and be able to predict end point of bioattenuation. Soil physico-chemical parameters showed significant differences (P < 0.05) between the Polluted Soil (PS) and the Unpolluted control (US)across time points. After 21 days, the diesel content decreased by 27.39%, and at the end of 42 days, by 57.11%. Aromatics such as benzene, anthanthrene, propylbenzene, phenanthrenequinone, anthraquinone, and phenanthridine were degraded to non-detected levels within 42 days, while some medium range alkanes and polyaromatics such as acenaphthylene, naphthalene, and anthracene showed significant levels of degradation. After 21 days (LASTD21), there was a massive enrichment of the phylum Proteobacteria (72.94%), a slight decrease in the abundance of phylum Actinobacteriota (12.74%), and > 500% decrease in the abundance of the phylum Acidobacteriodota (5.26%). Day 42 (LASTD42) saw establishment of the dominance of the Proteobacteria (34.95%), Actinobacteriota, (21.71%), and Firmicutes (32.14%), and decimation of phyla such as Gemmatimonadota, Planctomycetota, and Verrucromicrobiota which play important roles in the cycling of elements and soil health. Principal component analysis showed that in PS moisture contents, phosphorus, nitrogen, organic carbon, had greater impacts on the community structure in LASTD21, while acidity, potassium, sodium, calcium and magnesium impacted the control sample. Recovery time of the soil based on the residual hydrocarbons at Day 42 was estimated to be 229.112 d. Thus, additional biostimulation may be required to achieve cleanup within one growing season.

Genomic analysis of a marine alphaproteobacterium Sagittula sp. strain MA-2 that carried eight plasmids.

Bacteria that belong to the family Roseobacteraceae in the Alphaproteobacteria class are widely distributed in marine environments with remarkable physiological diversity, which is considered to be attributed to their genomic plasticity. In this study, a novel isolate of the genus Sagittula within Roseobacteraceae, strain MA-2, was obtained from a coastal marine bacterial consortium enriched with aromatic hydrocarbons, and its complete genome was sequenced. The genome with a total size of 5.69 Mbp was revealed to consist of a 4.67-Mbp circular chromosome and eight circular plasmids ranging in size from 19.5 to 361.5 kbp. Further analyses of functional genes in the strain MA-2 genome identified homologous genes responsible for the biotransformation of gentisic acid, which were located on one of its plasmids and were not found in genomes of other Sagittula strains available from databases. This suggested that strain MA-2 had acquired these genes via horizontal gene transfers that enabled them to degrade and utilize gentisic acid as a growth substrate. This study provided the second complete genome sequence of the genus Sagittula and supports the hypothesis that acquisition of ecologically relevant genes in extrachromosomal replicons allows Roseobacteraceae to be highly adaptable to diverse lifestyles.

HADEG: A curated hydrocarbon aerobic degradation enzymes and genes database.

Databases of genes and enzymes involved in hydrocarbon degradation have been previously reported. However, these databases specialize on only a specific group of hydrocarbons and/or are constructed partly based on enzyme sequences with putative functions indicated by in silico research, with no experimental evidence. Here, we present a curated database of Hydrocarbon Aerobic Degradation Enzymes and Genes (HADEG) containing proteins and genes involved in alkane, alkene, aromatic, and plastic aerobic degradation and biosurfactant production based solely on experimental evidence, which are present in bacteria, and fungi. HADEG includes 259 proteins for petroleum hydrocarbon degradation, 160 for plastic degradation, and 32 for biosurfactant production. This database will help identify and predict hydrocarbon degradation genes/pathways and biosurfactant production in genomes.