Isolation and characterization of marine diesel oil-degrading Acinetobacter sp. strain Y2

Machine learning-guided determination of Acinetobacter density in waterbodies receiving municipal and hospital wastewater effluents

A smart artificial intelligent system (SAIS) for Acinetobacter density (AD) enumeration in waterbodies represents an invaluable strategy for avoidance of repetitive, laborious, and time-consuming routines associated with its determination. This study aimed to predict AD in waterbodies using machine learning (ML). AD and physicochemical variables (PVs) data from three rivers monitored via standard protocols in a year-long study were fitted to 18 ML algorithms. The models' performance was assayed using regression metrics. The average pH, EC, TDS, salinity, temperature, TSS, TBS, DO, BOD, and AD was 7.76 ± 0.02, 218.66 ± 4.76 µS/cm, 110.53 ± 2.36 mg/L, 0.10 ± 0.00 PSU, 17.29 ± 0.21 °C, 80.17 ± 5.09 mg/L, 87.51 ± 5.41 NTU, 8.82 ± 0.04 mg/L, 4.00 ± 0.10 mg/L, and 3.19 ± 0.03 log CFU/100 mL respectively. While the contributions of PVs differed in values, AD predicted value by XGB [3.1792 (1.1040-4.5828)] and Cubist [3.1736 (1.1012-4.5300)] outshined other algorithms. Also, XGB (MSE = 0.0059, RMSE = 0.0770; R² = 0.9912; MAD = 0.0440) and Cubist (MSE = 0.0117, RMSE = 0.1081, R² = 0.9827; MAD = 0.0437) ranked first and second respectively, in predicting AD. Temperature was the most important feature in predicting AD and ranked first by 10/18 ML-algorithms accounting for 43.00-83.30% mean dropout RMSE loss after 1000 permutations. The two models' partial dependence and residual diagnostics sensitivity revealed their efficient AD prognosticating accuracies in waterbodies. In conclusion, a fully developed XGB/Cubist/XGB-Cubist ensemble/web SAIS app for AD monitoring in waterbodies could be deployed to shorten turnaround time in deciding microbiological quality of waterbodies for irrigation and other purposes.

Study on the Bacterial Communities of the Biofilms on Titanium, Aluminum, and Copper Alloys at 5,772 m Undersea in Yap Trench

Biofilms formed on metal surfaces strongly affect metallic instruments serving in marine environments. However, due to sampling difficulty, less has been known about the bacterial communities of the biofilm on metallic surfaces in hadal environments, so the failure process of these deep-sea metallic instruments influenced by microbial communities could be hardly predicted. In this research, seven alloys, including titanium, aluminum, and copper alloys, were exposed in Yap Trench hadal environment for 1 year. Thus, the communities of the biofilms formed on metallic surfaces at 5,772 m undersea in Yap Trench were initially reported in previous studies. Then, 16S rRNA gene sequencing was performed to visualize the in situ bacterial communities of the biofilms formed on titanium, aluminum, and copper alloys at 5,772 m undersea in Yap Trench. It was found that Proteobacteria was the dominant phylum in all samples, but distinct genera were discovered on various alloys. The titanium alloy provided a suitable substrate for a mutualistic symbiotic biofilm with abundant bacterial richness. Aluminum alloys without copper components showed the least bacterial richness and formed a cold-adapted and oligotrophic-adapted biofilm containing the genera Sulfurimonas and PS1 Clade, while copper-present alloys showed relatively high bacterial richness with copper-resistant or even copper-utilizing biofilms constituting the genera Stenotrophomonas, Burkholderia-Caballeronia-Paraburkholderia, and Achromobacter on the surfaces. Furthermore, among all the element components contained in alloys investigated in this research, copper element showed the strongest influences on the composition and function of microbial communities in the biofilms formed on various metallic surfaces.

Bioremediation of oily seawater by Bacteria immobilization on a novel carrier material containing nutrients

A novel carrier material was obtained by coating puffed rhubarb rice (PRR) with calcium alginate (CA) membrane. The carrier material was prepared to contain oil-degrading bacterial strains and inorganic nutrients through entrapping them in different locations. This formulation possessed floatability, biodegradability and nutrient slow-release properties. Therefore, it could be applied for oil biodegradation on seawater surfaces. For controlling the release rate of nutrients, the optimal preparation technique was established. The number of viable cells immobilized on the carrier material reached 2 × 10⁹ CFU/g. This formulation could be stored at -20 °C for three months without a significant decrease in the number of viable immobilized cells (4 × 10⁸ CFU/g). Scanning electron microscope (SEM) results showed that the cells were immobilized on the outer CA membrane, and the inorganic nutrients were entrapped in the inner PRR and CA membrane. The immobilized cells were able to remove 86% of the diesel oil at an initial diesel oil concentration of 1% (v/v), an incubation temperature of 37 °C, during three days of incubation. Gas chromatography-mass spectrometry (GC-MS) analysis results showed that most components of diesel oil were degraded by the formulations.

Bioremediation of marine oil spills by immobilized oil-degrading bacteria and nutrition emulsion

The combination of bioaugmentation and biostimulation was used to speed up the bioremediation of marine oil spills. A novel carrier material that consisted of puffed panicum miliaceum (PPM), calcium alginate and chitosan was prepared. The porous structure and low density of PPM ensured this carrier material not only had appropriate physical and biological properties for the aggregation of microorganisms but also was biodegradable and floating on the seawater surface for bioremediation of oil pollution. An oil-degrading bacterial consortium was immobilized via adsorption on the carrier material. The immobilized bacteria were observed with scanning electron microscopy. The number of viable cells immobilized on the material was approximately 1.12 × 10⁸ CFU/g. To solve the problem of nutrients supplementation in seawater, an emulsion formed with urea solution, soybean lecithin, alcohol and oleic acid was prepared as oleophilic fertilizer. The results from laboratory and field mesocosm experiments showed that the combination of immobilized bacteria and the emulsion achieved a higher oil removal efficiency compared with the use of them separately. The results of field mesocosm experiments conducted in the coastal seawater showed that most of the petroleum pollutant (> 98%) was removed from the surface of seawater in 24 h. GC-MS analysis showed that most components of petroleum pollutants had been removed. This formula with immobilized bacteria and emulsion can be exploited further for the bioremediation of marine oil spills.

Characterization and genomic analysis of a diesel-degrading bacterium, Acinetobacter calcoaceticus CA16, isolated from Canadian soil

Background

With the high demand for diesel across the world, environmental decontamination from its improper usage, storage and accidental spills becomes necessary. One highly environmentally friendly and cost-effective decontamination method is to utilize diesel-degrading microbes as a means for bioremediation. Here, we present a newly isolated and identified strain of Acinetobacter calcoaceticus (‘CA16’) as a candidate for the bioremediation of diesel-contaminated areas.

Results

Acinetobacter calcoaceticus CA16 was able to survive and grow in minimal medium with diesel as the only source of carbon. We determined through metabolomics that A. calcoaceticus CA16 appears to be efficient at diesel degradation. Specifically, CA16 is able to degrade 82 to 92% of aliphatic alkane hydrocarbons (C_nH_n + 2; where n = 12–18) in 28 days. Several diesel-degrading genes (such as alkM and xcpR) that are present in other microbes were also found to be activated in CA16.

Conclusions

The results presented here suggest that Acinetobacter strain CA16 has good potential in the bioremediation of diesel-polluted environments.

A novel exoelectrogen from microbial fuel cell: Bioremediation of marine petroleum hydrocarbon pollutants

In the past decades, the microbial fuel cell (MFC) technology has caught the attention of the scientific community for its potential in transforming petroleum hydrocarbon (PHC) pollutants directly into electricity through microbial catalyzed anodic. The microbe was one of the most important factors that both influence MFCs and PHC degradation. Here we aimed to identify new microbes to expand the list of microbial species which are both electrogenic and diesel hydrocarbon degrading. In this text, we depicted a strain of microbe named E2, isolated from on the anode surface of MFC, and using diesel as sole carbon source. E2 exhibited electrochemical activity in cyclic voltammetry curve, implicating that it had electrogenic ability. E2 degraded about 50% diesel (3.26 g/L) in maximum during 8 days. Pyrosequencing of 16S rRNA gene of E2 revealed E2 was a sub-strain of Vibrio. Corresponding to salt and alkali tolerant properties of vibrio, the optimal condition for E2 in degrading diesel was 3%-4% in salinity, and pH 8-9 in mineral medium. Collectively, as a member of Gammaproteobacteria class, E2 was novel marine microbe both electricity generation and diesel degradation, which may attract its future application toward artificial microbial community construction in MFC in promoting the PHC pollution removal.

Investigating the performance of an anaerobic baffled bioreactor for the biodegradation of alkaline-surfactant-polymer in oilfield water

The anaerobic baffled reactor (ABR) was used to treat alkaline-surfactant-polymer (ASP) flooding wastewater in the Daqing oilfield. With the ABR, hydraulic retention time (HRT)was reduced from 72  to 24 h, the bioreactor purification capability gradually improved. After the ABR running for 100 days, the removal rate of raw oil, suspended solid and surfactant reached 99.8%, 94.4% and 50%, respectively; alkali, polymer and viscosity were removed at a rate of about 16%, 7% and 20%, respectively. There were 39 kinds of organic materials detected by GCMS in the original water sample, while only 12 kinds of organics were left in the ABR outfall. The above results showed that the anaerobic, facultative anaerobic and aerobic compartment of ABR have strong capability of biodegrading petroleum pollution matter. Pyrosequencing analysis of the 16S rRNA indicated that Acinetobacter, Arcobacter, Pseudomonas and Paracoccus were the dominant bacteria genera present in the ABR reactor, among them Acinetobacter was the dominant species in the bacterial community.

Draft Genome Sequence of n-Alkane-Utilizing Acinetobacter sp. Strain BS1, Isolated from Ethane Oxidation Culture

Here, we report the draft whole-genome sequence of a bacterial strain, Acinetobacter sp. strain BS1, isolated from black soil during ethane oxidation culture. Medium- or long-chain alkane oxidation-related genes were identified; however, the short-chain alkane monooxygenase was not detected.

In situ microbial remediation of crude oil-soaked marine sediments using zeolite carrier with a polymer coating

Marine oil spill pollution is an important environmental problem in the world, especially crude oil-soaked marine sediments, because they are difficult to be remediated. In this study, in situ bioremediation of oil-soaked sediment was performed in the middle of the Bohai Sea. Oil-degrading bacteria were adsorbed on powdery zeolite (PZ)/granular zeolites (GZ) surfaces and then wrapped with poly-γ glutamic acid (γ-PGA). Settling column and wave flume experiments were conducted to model marine conditions and to select appropriate biological reagents. The optimal conditions were as follows: the average diameter of GZ 3 mm, mass ratio of GZ/PZ 2:1, and concentration of γ-PGA 7%. After bioremediation, over 50% of most oil-spilled pollutants n-alkanes (C₁₂ to C₂₇) and polycyclic aromatic hydrocarbons were degraded in 70 days. This work resulted in a successful trial of in situ bioremediation of oil-soaked marine sediments.

Bioaugmentation strategy employing a microbial consortium immobilized in chitosan beads for oil degradation in mesocosm scale

A bacterial consortium composed by four metagenomic clones and Bacillus subtilis strain CBMAI 707, all derived from petroleum reservoirs, was entrapped in chitosan beads and evaluated regarding hydrocarbon degradation capability. Experiments were carried out in mesocosm scale (3000L) with seawater artificially polluted with crude oil. At different time intervals, mesocosms were sampled and subjected to GC-FID and microbiological analyses, as total and heterotrophic culturable bacterial abundance (DAPI and CFU count), biological oxygen demand (BOD) and taxonomic diversity (massive sequencing of 16S rRNA genes). The results obtained showed that degradation of n-alkane hydrocarbons was similar between both treatments. However, aromatic compound degradation was more efficient in bioaugmentation treatment, with biodegradation percentages reaching up to 99% in 30days. Community dynamics was different between treatments and the consortium used in the bioaugmentation treatment contributed to a significant increase in aromatic hydrocarbon degradation.

Isolation, identification and diesel-oil biodegradation capacities of indigenous hydrocarbon-degrading strains of Cellulosimicrobium cellulans and Acinetobacter baumannii from tarball at Terengganu beach, Malaysia

In this study, we isolated two indigenous hydrocarbon-degrading bacteria from tarball found in Rhu Sepuluh beach, Terengganu, Malaysia. These bacteria were identified based on their physiological characteristic and 16S rRNA gene sequence analysis, and they showed 99% similarity with Cellulosimicrobium cellulans DSM 43879 and Acinetobacter baumannii ATCC 19606 respectively. Their hydrocarbon-degrading capabilities were tested using diesel-oil as sole carbon source. Results analysed using GC-MS, showed diesel-oil alkanes were degraded an average 64.4% by C. cellulans and 58.1% by A. baumannii with medium optical density reaching 0.967 (C. cellulans) and 1.515 (A. baumannii) in minimal salt media at 32°C for 10days. Individual diesel-oil alkanes were degraded between 10%-95.4% by C. cellulans and 0.2%-95.9% by A. baumannii. Both strains utilized diesel-oil for growth. The study suggests both strains are part of indigenous hydrocarbon-degrading bacteria in tarball with potential for bioremediation of oil-polluted marine environment.

Dimethylamine biodegradation by mixed culture enriched from drinking water biofilter

Dimethylamine (DMA) is one of the important precursors of drinking water disinfection by-product N-nitrosodimethylamine (NDMA). Reduction of DMA to minimize the formation of carcinogenic NDMA in drinking water is of practical importance. Biodegradation plays a major role in elimination of DMA pollution in the environment, yet information on DMA removal by drinking water biofilter is still lacking. In this study, microcosms with different treatments were constructed to investigate the potential of DMA removal by a mixed culture enriched from a drinking water biofilter and the effects of carbon and nitrogen sources. DMA could be quickly mineralized by the enrichment culture. Amendment of a carbon source, instead of a nitrogen source, had a profound impact on DMA removal. A shift in bacterial community structure was observed with DMA biodegradation, affected by carbon and nitrogen sources. Proteobacteria was the predominant phylum group in DMA-degrading microcosms. Microorganisms from a variety of bacterial genera might be responsible for the rapid DMA mineralization.

Optimization of nutrient component for diesel oil degradation by Acinetobacter beijerinckii ZRS

A new bacterial strain that is capable of using diesel as the sole carbon source was isolated from the petroleum-contaminated soil of Xinjiang oil field, Northwest China. This bacterium was identified on the basis of its morphological and physiological characteristics and 16S rRNA gene sequence analysis, and it showed the greatest similarity with Acinetobacter beijerinckii 302-PWB-OH1 (99.86%). In order to enhance degradation efficiency, single-factor experiments and response surface methodology (RSM) were employed to optimize the nutrients used in artificial seawater. The results of this study revealed that 2.05 g L(-1) (NH4)2SO4, 1.46 g L(-1) Na2HPO4, and 14 mg L(-1) yeast extract in artificial seawater resulted in increasing the diesel degradation rate of the bacterial strain from 20.87% to 80.40% within 7 days. The actual experimental results were in agreement with the prediction.