Bacterial community analysis of biofilm on API 5LX carbon steel in an oil reservoir environment

Type VI secretion system drives bacterial diversity and functions in multispecies biofilms

Type VI secretion system (T6SS) plays an essential role in interspecies interactions and provides an advantage for a strain with T6SS in multispecies biofilms. However, how T6SS drives the bacterial community structure and functions in multispecies biofilms still needs to be determined. Using gene deletion and Illumina sequencing technique, we estimated bacterial community responses in multispecies biofilms to T6SS by introducing T6SS-containing Pseudomonas putida KT2440. Results showed that the niche structure shifts of multispecies biofilms were remarkably higher in the presence of T6SS than in the absence of T6SS. The presence of T6SS significantly drove the variation in microbial composition, reduced the alpha-diversity of bacterial communities in multispecies biofilms, and separately decreased and increased the relative abundance of Proteobacteria and Bacteroidota. Co-occurrence network analysis with inferred putative bacterial interactions indicated that P. putida KT2440 mainly displayed strong negative associations with the genera of Psychrobacter, Cellvibrio, Stenotrophomonas, and Brevundimonas. Moreover, the function redundancy index of the bacterial community was strikingly higher in the presence of T6SS than in the absence of T6SS, regardless of whether relative abundances of bacterial taxa were inhibited or promoted. Remarkably, the increased metabolic network similarity with T6SS-containing P. putida KT2440 could enhance the antibacterial activity of P. putida KT2440 on other bacterial taxa. Our findings extend knowledge of microbial adaptation strategies to potential bacterial weapons and could contribute to predicting biodiversity loss and change in ecological functions caused by T6SS.

Shumkonia mesophila gen. nov., sp. nov., a novel representative of Shumkoniaceae fam. nov. and its potentials for extracellular polymeric substances formation and sulfur metabolism revealed by genomic analysis

A microaerophilic, mesophilic, chemoorganoheterotrophic bacterium, designated Y-P2T, was isolated from oil sludge enrichment in China. Cells of the strain were Gram-stain-negative, non-motile, non-spore-forming, rod-shaped or slightly curved with 0.8-3.0 µm in length and 0.4-0.6 µm in diameter. The strain Y-P2T grew optimally at 25 °C (range from 15 to 30 °C) and pH 7.0 (range from pH 6.0 to 7.5) without NaCl. The major cellular fatty acids were C16:0, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). The main polar liquids of strain Y-P2T comprised phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). The respiratory quinone was Q-10. Acetate and H2 were the fermentation products of glucose. The DNA G + C content was 66.0%. Strain Y-P2T shared the highest 16S rRNA gene sequence similarity (90.3-90.6%) with species within Oceanibaculum of family Thalassobaculaceae in Rhodospirillales. Phylogenetic analyses based on 16S rRNA gene sequences and genomes showed that strain Y-P2T formed a distinct evolutionary lineage within the order Rhodospirillales. On the basis of phenotypic, phylogenetic and phylogenomic data, we propose that strain Y-P2T represents a novel species in a novel genus, for which Shumkonia mesophila gen. nov., sp. nov., within a new family Shumkoniaceae fam. nov. The type strain is Y-P2T (= CCAM 826 T = JCM 34766 T).

A new paradigm in the bioremoval of lead, nickel, and cadmium using a cocktail of biosystems: a metagenomic approach

Lead (Pb), nickel (Ni), and cadmium (Cd) are known for its harmful effects on the environment. Microbial community related to soil plays a pivotal role in configuring several properties of the ecosystem. Thus, remediation of such heavy metals using multiple biosystems had shown excellent bioremoval potential. The current study demonstrates the integrated approach of Chrysopogon zizanioides in combination with earthworm Eisenia fetida augmented with VITMSJ3 potent strain for the uptake of metals like Pb, Ni, and Cd from the contaminated soil. For the uptake of heavy metals, Pb, Ni, and Cd with the concentrations of 50, 100, and 150 mg kg^-1 were supplemented in pots with plants and earthworms. C. zizanioides was used for bioremoval due to their massive fibrous root system which can absorb heavy metals. A substantial increase of 70-80% Pb, Ni, and Cd was found for VITMSJ3 augmented setup. A total of 12 earthworms were introduced in each setup and were tested for the toxicity and damages in the various internal structures. Reduction in malondialdehyde (MDA) content was observed in the earthworms with VITMSJ3 strain proving less toxicity and damages. Metagenomic analysis of the soil associated bacterial diversity was assessed by amplifying the V3V4 region of the 16S rRNA gene and the annotations were studied. Firmicutes were found to be the predominant genus with 56.65% abundance in the bioaugmented soil R (60) proving the detoxification of metals in the bioaugmented soil. Our study proved that a synergistic effect of plant and earthworm in association with potent bacterial strain had higher uptake of Pb, Ni, and Cd. Metagenomic analysis revealed the changes in microbial abundance in the soil before and after treatment.

Integrated approach of photo-assisted electrochemical oxidation and sequential biodegradation of textile effluent

Synthetic azo dyes are extensively used in the textile industries, which are being released as textile effluent into the environment presence of azo dyes in the environment is great environmental concern therefore treatment of textile effluent is crucial for proper release of the effluent into the environment. Electrochemical oxidation (EO) is extensively used in the degradation of pollutants because of its high efficiency. In this study, photo-assisted electrooxidation (PEO) followed by biodegradation of the textile effluent was evaluated. The pretreatment of textile effluent was conducted by EO and PEO in a tubular flow cell with TiO₂-Ti/IrO₂-RuO₂ anode and titanium cathode under different current densities (10, 15, and 20 mA cm^-2). The chemical oxygen demand level reduced from 3150 mg L^-1 to 1300 and 600 mg L^-1under EO and PEO, respectively. Furthermore, biodegradation of EO and PEO pretreated textile effluent shows reduction in chemical oxygen demand (COD) from 1300 mg L^-1 to 900 mg L^-1and 600 mg L^-1to 110 mg L^-1, respectively. The most abundant genera were identified as Acetobacter, Achromobacter, Acidaminococcus, Actinomyces, and Acetomicrobium from the textile effluent. This study suggests that an integrated approach of PEO and subsequent biodegradation might be an effective and eco-friendly method for the degradation of textile effluent.

Characterization of two novel strains of Pseudomonas aeruginosa on biodegradation of crude oil and its enzyme activities

Crude oil contaminant is one of the major problem to environment and its removal process considered as most challenging tool currently across the world. In this degradation study, crude oil hydrocarbons are degraded on various pH optimization conditions (pH 2, 4,6,7,8 and 10) by using two biosurfactant producing bacterial strains Pseudomonas aeruginosa PP3 and Pseudomonas aeruginosa PP4. During crude oil biodegradation, degradative enzymes alkane hydroxylase and alcohol dehydrogenase were examined and found to be higher in PP4 than PP3. Biodegradation efficiency (BE) of crude oil by both PP3 and PP4 were analysed by gas chromatography mass spectroscopy (GCMS). Based on strain PP3, the highest BE was observed in pH 2 and pH 4 were found to be 62% and 69% than pH 6, 7, 8 and 10 (47%, 47%, 49% and 45%). It reveals that PP3 was survived effectively in acidic condition and utilized the crude oil hydrocarbons. In contrast, the highest BE of PP4 was observed in pH 7 (78%) than pH4 (68%) and pH's 2, 6, 8 and 10 (52%, 52%, 43% and 53%) respectively. FTIR spectra results revealed that the presence of different functional group of hydrocarbons (OH, -CH₃, CO, C-H) in crude oil. GCMS results confirmed that both strains PP3 and PP4 were survived in acidic condition and utilized the crude oil hydrocarbons as sole carbon sources. This is the first observation on biodegradation of crude oil by the novel strains of Pseudomonas aeruginosa in acidic condition with higher BE. Overall, the extracellular enzymes and surface active compounds (biosurfactant) produced by bacterial strains were played a key role in crude oil biodegradation process.

Macrolepiota-mediated synthesized silver nanoparticles as a green corrosive inhibitor for mild steel in re-circulating cooling water system

A simple, cost effective and eco-friendly silver nanoparticle (AgNPs) was synthesized by wild edible Macrolepiota mushroom. Nanoparticles were characterized by UV-visible, FTIR, XRD analysis and TEM analysis. The characterized studies confirmed the spherical shape of AgNPs with 20-50 nm size. Biocorrosion efficacy of myco-synthesized AgNPs and the mushroom extract were tested against mild steel by corrosive bacteria Bacillus thuringiensis EN2, Terribacillus aidingensis EN3 and Bacillus oleronius EN9. Weight loss analysis, EIS, and surface analysis were used to evaluate the corrosion inhibition efficiency of mild steel in various experimental systems. Reduced corrosion rate (0.07 mm/y, 0.14 mm/y), reduced weight loss (0.006 ± 2, 0.011 ± 2) and increased corrosion inhibition efficiency (59%, 18%) were identified in both system II and system IV. Peak intensity was reduced in both surface analysis studies (FTIR and XRD) in the presence of mushroom extract and AgNPs. EIS studies reveal that the mushroom extract and AgNPs act as a corrosive green inhibitor and adsorbs on the mild steel surfaces in cooling water tower system, which are responsible for corrosion protection.

Enhanced biodegradation of hydrophobic organic pollutants by the bacterial consortium: Impact of enzymes and biosurfactants

Hydrocarbons and their derivative compounds are recalcitrant in nature and causing adverse impacts to the environment and are classified as important pollutants. Removal of these pollutants from the atmosphere is a challenging process. Hydrophobic organic pollutants (HOPs) including crude oil, diesel, dotriacontane (C₃₂), and tetracontane (C₄₀) are subjected to the biodegradation study by using a bacterial consortium consist of Bacillus subtilis, Pseudomonas stutzeri, and Acinetobacter baumannii. The impact of pH and temperature on the biodegradation process was monitored. During the HOPs biodegradation, the impact of hydrocarbon-degrading extracellular enzymes such as alcohol dehydrogenase, alkane hydroxylase, and lipase was examined, and found average activity about 47.2, 44.3, and 51.8 μmol/mg^-1, respectively. Additionally, other enzymes such as catechol 1,2 dioxygenase and catechol 2,3 dioxygenase were found as 118 and 112 μmol/mg^-1 Enzyme as an average range in all the HOPs degradation, respectively. Also, the impact of the extracellular polymeric substance and proteins were elucidated during the biodegradation of HOPs with the average range of 116.90, 54.98 mg/L^-1 respectively. The impact of biosurfactants on the degradation of different types of HOPs is elucidated. Very slight changes in the pH were also noticed during the biodegradation study. Biodegradation efficiency was calculated as 90, 84, 76, and 72% for crude oil, diesel, C_32, and C₄₀, respectively. Changes in the major functional groups (CH, C-O-C, CO, =CH₂, CH₂, CH₃) were confirmed by FTIR analysis and intermediated metabolites were identified by GCMS analysis. The surface-active molecules along with the enzymes played a crucial role in the biodegradation process.

Characterization of crude oil degrading bacterial communities and their impact on biofilm formation

In the present study, produced water sample collected from the Indian crude oil reservoir is used to enrich the bacterial communities. The impact of these enriched bacterial communities on the biodegradation of crude oil, biofilm formation, and biocorrosion process are elucidated. A crude oil degradation study is carried out with the minimal salt medium and 94% of crude oil was utilized by enriched bacterial communities. During the crude oil degradation many enzymes including alkane hydroxylase, alcohol dehydrogenase, and lipase are playing a key role in the biodegradation processes. The role of enriched bacterial biofilm on biocorrosion reactions are monitored by weight loss studies and electrochemical analysis. Weight loss study revealed that the biotic system has vigorous corrosion attacks compared to the abiotic system. Both AC-Impedance and Tafel analysis confirmed that the nature of the corrosion reaction take place in the biotic system. Very less charge transfer resistance and higher corrosion current are observed in the biotic system than in the abiotic system. Scanning electron microscope confirms that the dense biofilm formation favoured the pitting type of corrosion. X-ray diffraction analysis confirms that the metal oxides formed in the corrosion systems (biotic). From the metagenomic analysis of the V3-V4 region revealed that presence of diverse bacterial communities in the biofilm, and most of them are uncultured/unknown. Among the known genus, Bacillus, Halomonas, etc are dominant in the enriched bacterial biofilm sample. From this study, we conclude that the uncultured bacterial strains are found to be playing a key role in the pitting type of corrosion and they can utilize crude oil hydrocarbons, which make them succeeded in extreme oil reservoir environments.

Evaluation of Syzygium aromaticum aqueous extract as an eco-friendly inhibitor for microbiologically influenced corrosion of carbon steel in oil reservoir environment

In the present investigation, biocorrosion inhibition efficiency of Syzygium aromaticum (clove) aqueous extract on carbon steel in presence of four corrosion causing bacterial strains (Bacillus subtilis, Streptomyces parvus, Pseudomonas stutzeri, and Acinetobacter baumannii) was explored. Weight loss, potentiodynamic polarization, and AC impedance studies were carried out with and without bacterial strains and clove extract. The results obtained from weight loss and AC impedance studies indicate that these corrosion causing bacterial strains accelerated the biocorrosion reaction and biofilm playing a key role in this process. However, the addition of clove extract into the corrosive medium decreased the corrosion current and increased the solution and charge transfer resistance. The significant inhibition efficiency of about 87% was archived in the mixed consortia system with clove extract. The bioactive compounds were playing an important role in the antibacterial activity of the clove extract. It was revealed that clove extract has both biocidal and corrosion inhibition properties.

Formation of electroactive biofilms derived by nanostructured anodes surfaces

Microbial fuel cells (MFCs) have significant interest in the research community due to their ability to generate electricity from biodegradable organic matters. Anode materials and their morphological structures play a crucial role in the formation of electroactive biofilms that enable the direct electron transfer. In this work, modified electrodes with nanomaterials, such as multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), Al₂O₃/rGO or MnO₂/MWCNTs nanocomposites were synthesized, characterized and utilized to support the growth of electrochemically active biofilms. The MFC's performance is optimized using anode-respiring strains isolated from biofilm-anode surface, while the adjusted operation is conducted with the consortium of (Enterobacter sp.). Besides the formation of matured biofilm on its surface, MnO₂/MWCNTs nanocomposite produced the highest electrical potential outputs (710 mV) combined with the highest power density (372 mW/m²). Thus, a correlation between the anode nanostructured materials and the progression of the electrochemically active biofilms formation is presented, allowing new thoughts for enhancing the MFC's performance for potential applications ranging from wastewater treatment to power sources.