Marine Microbiota Responses to Shipping Scrubber Effluent Assessed at Community Structure and Function Endpoints

The use of novel high-throughput sequencing (HTS) technologies to examine the responses of natural multidomain microbial communities to scrubber effluent discharges to the marine environment is still limited. Thus, we applied metabarcoding sequencing targeting the planktonic unicellular eukaryotic and prokaryotic fraction (phytoplankton, bacterioplankton, and protozooplankton) in mesocosm experiments with natural microbial communities from a polluted and an unpolluted site. Furthermore, metagenomic analysis revealed changes in the taxonomic and functional dominance of multidomain marine microbial communities after scrubber effluent additions. The results indicated a clear shift in the microbial communities after such additions, which favored bacterial taxa with known oil and polycyclic aromatic hydrocarbons (PAHs) biodegradation capacities. These bacteria exhibited high connectedness with planktonic unicellular eukaryotes employing variable trophic strategies, suggesting that environmentally relevant bacteria can influence eukaryotic community structure. Furthermore, Clusters of Orthologous Genes associated with pathways of PAHs and monocyclic hydrocarbon degradation increased in numbers at treatments with high scrubber effluent additions acutely. These genes are known to express enzymes acting at various substrates including PAHs. These indications, in combination with the abrupt decrease in the most abundant PAHs in the scrubber effluent below the limit of detection-much faster than their known half-lives-could point toward a bacterioplankton-initiated rapid ultimate biodegradation of the most abundant toxic contaminants of the scrubber effluent. The implementation of HTS could be a valuable tool to develop multilevel biodiversity indicators of the scrubber effluent impacts on the marine environment, which could lead to improved impact assessment. Environ Toxicol Chem 2024;00:1-18. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Biofilm formation in xenobiotic-degrading microorganisms

The increased presence of xenobiotics affects living organisms and the environment at large on a global scale. Microbial degradation is effective for the removal of xenobiotics from the ecosystem. In natural habitats, biofilms are formed by single or multiple populations attached to biotic/abiotic surfaces and interfaces. The attachment of microbial cells to these surfaces is possible via the matrix of extracellular polymeric substances (EPSs). However, the molecular machinery underlying the development of biofilms differs depending on the microbial species. Biofilms act as biocatalysts and degrade xenobiotic compounds, thereby removing them from the environment. Quorum sensing (QS) helps with biofilm formation and is linked to the development of biofilms in natural contaminated sites. To date, scant information is available about the biofilm-mediated degradation of toxic chemicals from the environment. Therefore, we review novel insights into the impact of microbial biofilms in xenobiotic contamination remediation, the regulation of biofilms in contaminated sites, and the implications for large-scale xenobiotic compound treatment.

Biotechnological applications of biofilms formed by osmotolerant and halotolerant yeasts

Many microorganisms are capable of developing biofilms under adverse conditions usually related to nutrient limitation. They are complex structures in which cells (in many cases of different species) are embedded in the material that they secrete, the extracellular matrix (ECM), which is composed of proteins, carbohydrates, lipids, and nucleic acids. The ECM has several functions including adhesion, cellular communication, nutrient distribution, and increased community resistance, this being the main drawback when these microorganisms are pathogenic. However, these structures have also proven useful in many biotechnological applications. Until now, the most interest shown in these regards has focused on bacterial biofilms, and the literature describing yeast biofilms is scarce, except for pathological strains. Oceans and other saline reservoirs are full of microorganisms adapted to extreme conditions, and the discovery and knowledge of their properties can be very interesting to explore new uses. Halotolerant and osmotolerant biofilm-forming yeasts have been employed for many years in the food and wine industry, with very few applications in other areas. The experience gained in bioremediation, food production and biocatalysis with bacterial biofilms can be inspiring to find new uses for halotolerant yeast biofilms. In this review, we focus on the biofilms formed by halotolerant and osmotolerant yeasts such as those belonging to Candida, Saccharomyces flor yeasts, Schwannyomyces or Debaryomyces, and their actual or potential biotechnological applications. KEY POINTS: • Biofilm formation by halotolerant and osmotolerant yeasts is reviewed. • Yeasts biofilms have been widely used in food and wine production. • The use of bacterial biofilms in bioremediation can be expanded to halotolerant yeast counterparts.

Response of selected microbial strains and their consortia to the presence of automobile paints: Biofilm growth, matrix protein content and hydrolytic enzyme activity

The goal of the current study was to examine the effects of pollutants (White color – CP; Metallic red color – FM; Thinner – CN; Thinner for rinsing paint – MF; Basic color (primer) – FH) originating from the automotive industry on the biofilm growth, matrix protein content, and activity of the hydrolytic enzymes of selected microbial strains in laboratory conditions that mimic the bioreactor conditions. The chosen microorganisms (bacteria, yeasts, and fungi) were isolated from automotive industry wastewater. Pure microbe cultures and their consortia were injected into AMB Media carriers and developed into biofilms. The use of AMB media carriers has been linked to an increase in the active surface area colonized by microorganisms. Afterwards, the carriers were transferred to Erlenmeyer flasks with nutrient media and pollutants at a concentration of 200 μL/mL. The current study found that, depending on the microbial strain, development phase, and chemical structure, the assessed pollutants had an inhibitory or stimulatory influence on the growth of single cultures and their consortia. Statistical analysis found positive correlations between the protein content in the matrix and the biofilm biomass of Rhodotorula mucilaginosa and consortia in CP and FH media, respectively. The proteolytic activity of Candida utilis was very pronounced in media with MF and CN. The best alkaline phosphatase activity (ALP) was achieved in the CN medium of R. mucilaginosa. Acid invertase activity was the highest in the FM and CP media of Escherichia coli and consortia, respectively, whereas the highest alkaline invertase activity was measured in the MF medium of E. coli. A positive correlation was confirmed between ALP and the biofilm biomass of R. mucilaginosa in CP and CN media, as well as between ALP and the biofilm biomass of Penicillium expansum in FM medium. The findings provide novel insights into the extracellular hydrolytic activity of the investigated microbial strains in the presence of auto paints, as well as a good platform for subsequent research into comprehensive biofilm profiling using modern methodologies.

Microbial biofilms: Recent advances and progress in environmental bioremediation

Microbial biofilms are formed by adherence of the bacteria through their secreted polymer matrices. The major constituents of the polymer matrices are extracellular DNAs, proteins, polysaccharides. Biofilms have exhibited a promising role in the area of bioremediation. These activities can be further improved by tuning the parameters like quorum sensing, characteristics of the adhesion surface, and other environmental factors. Organic pollutants have created a global concern because of their long-term toxicity on human, marine, and animal life. These contaminants are not easily degradable and continue to prevail in the environment for an extended period. Biofilms are being used for the remediation of different pollutants, among which organic pollutants have been of significance. The bioremediation of organic contaminants using biofilms is an eco-friendly, cheap, and green process. However, the development of this technology demands knowledge on the mechanism of action of the microbes to form the biofilm, types of specific bacteria or fungi responsible for the degradation of a particular organic compound, and the mechanistic role of the biofilm in the degradation of the pollutants. This review puts forth a comprehensive summary of the role of microbial biofilms in the bioremediation of different environment-threatening organic pollutants.

Use of bacterial isolates in the treatment of textile dye wastewater: A review

The textile industry uses large amounts of dyes like reactive, azo, anthraquinone, and triphenylmethane to colour textiles. Dyes that are not used up during the colouration process usually end up in water bodies as waste leading to the pollution of the water bodies. This makes the industry to be one of the major contributors to water pollution in the world. Bacterial agents isolated from various sources like dye contaminated soil and textile wastewater have shown to have the ability to effectively decolourise and degrade these dye pollutants leading to improved water quality. This review discusses bacterial isolates that have been used successfully to degrade and decolourise textile dyes, their mode of dye removal as well as the factors that affect their dye degradation ability. It further looks at the latest wastewater treatment technologies that incorporate bacterial microorganisms to treat dye wastewater.

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Bacterial isolates offer environmentally friendly solution to dye degradation.

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Pure and mixed bacterial cultures can remove textile dyes in optimised conditions.

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Dyes are removed through biosorption or biodegradation mechanisms.

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Latest technologies provide more effective dye removal options.

Biofilm-mediated bioremediation is a powerful tool for the removal of environmental pollutants

Biofilm-mediated bioremediation is an attractive approach for the elimination of environmental pollutants, because of its wide adaptability, biomass, and excellent capacity to absorb, immobilize, or degrade contaminants. Biofilms are assemblages of individual or mixed microbial cells adhering to a living or non-living surface in an aqueous environment. Biofilm-forming microorganisms have excellent survival under exposure to harsh environmental stressors, can compete for nutrients, exhibit greater tolerance to pollutants compared to free-floating planktonic cells, and provide a protective environment for cells. Biofilm communities are thus capable of sorption and metabolization of organic pollutants and heavy metals through a well-controlled expression pattern of genes governed by quorum sensing. The involvement of quorum sensing and chemotaxis in biofilms can enhance the bioremediation kinetics with the help of signaling molecules, the transfer of genetic material, and metabolites. This review provides in-depth knowledge of the process of biofilm formation in microorganisms, their regulatory mechanisms of interaction, and their importance and application as powerful bioremediation agents in the biodegradation of environmental pollutants, including hydrocarbons, pesticides, and heavy metals.

Biofilm-overproducing Bacillus amyloliquefaciens P29ΔsinR decreases Pb availability and uptake in lettuce in Pb-polluted soil

In this study, one mutant strain P29ΔsinR with increased biofilm production was constructed from a biofilm-producing Bacillus amyloliquefaciens strain P29. Then, the effect of strain P29 and its biofilm-overproducing mutant strain P29ΔsinR on Pb availability and accumulation in lettuce and the associated mechanisms were characterized in the Pb-contaminated soil. The live strains P29 and P29ΔsinR increased the dry masses of roots and edible tissues by 31-74% compared to the controls. The live strains P29 and P29ΔsinR reduced the Pb uptake in the roots by 36-52% and edible tissues by 24-43%, Pb bioconcentration factor by 36-52%, and rhizosphere soil available Pb content by 12-25%, respectively, compared to the controls. The live strains P29 and P29ΔsinR increased the pH, proportion of biofilm-producing bacteria by 46-154%, contents of polysaccharides by 99-139% and proteins by 32-57%, and gene relative abundances of epsC by 7.1-10.2-fold, tasA by 10.3-10.8-fold, and sipW by 6.5-26.1-fold, which were associated with biofilm formation and Pb adsorption in the rhizosphere soils, respectively, compared to the controls. Furthermore, the mutant strain P29ΔsinR showed higher ability to reduce Pb availability and uptake in lettuce and increase the pH, proportion of biofilm-producing bacteria, polysaccharide and protein contents, and relative abundances of these genes. These results showed that the biofilm-overproducing strain P29ΔsinR induced lower Pb availability and accumulation in the vegetable and more biofilm-producing bacteria, polysaccharide and protein production, and Pb-immobilizing related gene abundances in the Pb-contaminated soil.

Persistent organic pollutants: The trade-off between potential risks and sustainable remediation methods

Persistent Organic Pollutants (POPs) have become a very serious issue for the environment because of their toxicity, resistance to conventional degradation mechanisms, and capacity to bioconcentrate, bioaccumulate and biomagnify. In this review article, the safety, regulatory, and remediation aspects of POPs including aromatic, chlorinated, pesticides, brominated, and fluorinated compounds, are discussed. Industrial and agricultural activities are identified as the main sources of these harmful chemicals, which are released to air, soil and water, impacting on social and economic development of society at a global scale. The main types of POPs are presented, illustrating their effects on wildlife and human beings, as well as the ways in which they contaminate the food chain. Some of the most promising and innovative technologies developed for the removal of POPs from water are discussed, contrasting their advantages and disadvantages with those of more conventional treatment processes. The promising methods presented in this work include bioremediation, advanced oxidation, ionizing radiation, and nanotechnology. Finally, some alternatives to define more efficient approaches to overcome the impacts that POPs cause in the hydric sources are pointed out. These alternatives include the formulation of policies, regulations and custom-made legislation for controlling the use of these pollutants.

Probiotics as Therapeutic Tools against Pathogenic Biofilms: Have We Found the Perfect Weapon?

Bacterial populations inhabiting a variety of natural and human-associated niches have the ability to grow in the form of biofilms. A large part of pathological chronic conditions, and essentially all the bacterial infections associated with implanted medical devices or prosthetics, are caused by microorganisms embedded in a matrix made of polysaccharides, proteins, and nucleic acids. Biofilm infections are generally characterized by a slow onset, mild symptoms, tendency to chronicity, and refractory response to antibiotic therapy. Even though the molecular mechanisms responsible for resistance to antimicrobial agents and host defenses have been deeply clarified, effective means to fight biofilms are still required. Lactic acid bacteria (LAB), used as probiotics, are emerging as powerful weapons to prevent adhesion, biofilm formation, and control overgrowth of pathogens. Hence, using probiotics or their metabolites to quench and interrupt bacterial communication and aggregation, and to interfere with biofilm formation and stability, might represent a new frontier in clinical microbiology and a valid alternative to antibiotic therapies. This review summarizes the current knowledge on the experimental and therapeutic applications of LAB to interfere with biofilm formation or disrupt the stability of pathogenic biofilms.

The Usages and Potential Uses of Alginate for Healthcare Applications

Due to their unique properties, alginate-based biomaterials have been extensively used to treat different diseases, and in the regeneration of diverse organs. A lot of research has been done by the different scientific community to develop biofilms for fulfilling the need for sustainable human health. The aim of this review is to hit upon a hydrogel enhancing the scope of utilization in biomedical applications. The presence of active sites in alginate hydrogels can be manipulated for managing various non-communicable diseases by encapsulating, with the bioactive component as a potential site for chemicals in developing drugs, or for delivering macromolecule nutrients. Gels are accepted for cell implantation in tissue regeneration, as they can transfer cells to the intended site. Thus, this review will accelerate advanced research avenues in tissue engineering and the potential of alginate biofilms in the healthcare sector.

Potential of Variovorax paradoxus isolate BFB1_13 for bioremediation of BTEX contaminated sites

Here, we report and discuss the applicability of Variovorax paradoxus strain BFB1_13 in the bioremediation of BTEX contaminated sites. Strain BFB1_13 was capable of degrading all the six BTEX-compounds under both aerobic (O₂ conc. 8 mg l⁻¹) and micro-aerobic/oxygen-limited (O₂ conc. 0.5 mg l⁻¹) conditions using either individual (8 mg‧l⁻¹) or a mixture of compounds (~ 1.3 mg‧l⁻¹ of each BTEX compound). The BTEX biodegradation capability of SBP-encapsulated cultures (SBP—Small Bioreactor Platform) was also assessed. The fastest degradation rate was observed in the case of aerobic benzene biodegradation (8 mg l⁻¹ per 90 h). Complete biodegradation of other BTEX occurred after at least 168 h of incubation, irrespective of the oxygenation and encapsulation. No statistically significant difference was observed between aerobic and microaerobic BTEX biodegradation. Genes involved in BTEX biodegradation were annotated and degradation pathways were predicted based on whole-genome shotgun sequencing and metabolic analysis. We conclude that V. paradoxus strain BFB1_13 could be used for the development of reactive biobarriers for the containment and in situ decontamination of BTEX contaminated groundwater plumes. Our results suggest that V. paradoxus strain BFB1_13—alone or in co-culture with other BTEX degrading bacterial isolates—can be a new and efficient commercial bioremediation agent for BTEX contaminated sites.

Design of Bio-Absorbent Systems for the Removal of Hydrocarbons from Industrial Wastewater: Pilot-Plant Scale

The objective of this study was the development and design of a treatment system at a pilot-plant scale for the remediation of hydrocarbons in industrial wastewater. The treatment consists of a combined approach of absorption and biodegradation to obtain treated water with sufficient quality to be reused in fire defense systems (FDSs). The plant consists of four vertical flow columns (bioreactors) made of stainless steel (ATEX Standard) with dimensions of 1.65 × 0.5 m and water volumes of 192.4 L. Each bioreactor includes a holder to contain the absorbent material (Pad Sentec polypropylene). The effectiveness of the treatment system has been studied in wastewater with high and low pollutant loads (concentrations higher than 60,000 mg L⁻¹ of total petroleum hydrocarbons (TPH) and lower than 500 mg L⁻¹ of TPHs, respectively). The pilot-plant design can function at two different flow rates, Q1 (180 L h⁻¹) and Q2 (780 L h⁻¹), with or without additional aeration. The results obtained for strongly polluted wastewaters showed that, at low flow rates, additional aeration enhanced hydrocarbon removal, while aeration was unnecessary at high flow rates. For wastewater with a low pollutant load, we selected a flow rate of 780 L h⁻¹ without aeration. Different recirculation times were also tested along with the application of a post-treatment lasting 7 days inside the bioreactor without recirculation. The microbial diversity studies showed similar populations of bacteria and fungi in the inlet and outlet wastewater. Likewise, high similarity indices were observed between the adhered and suspended biomass within the bioreactors. The results showed that the setup and optimization of the reactor represent a step forward in the application of bioremediation processes at an industrial/large scale.

Fungi and biochar applications in bioremediation of organic micropollutants from aquatic media

The conventional wastewater treatment system such as bacteria, is not able to remove recalcitrant micropollutants effectively. While, fungi have shown high capacity in degradation of recalcitrant compounds. Biochar, on the other hand, has gained attention in water and wastewater treatment as a low cost and sustainable adsorbent. This paper aims to review the recent applications of three major fungal divisions including Basidiomycota, Ascomycota, and Mucoromycotina, in organic micropollutants removal from wastewater. Moreover, it presents an insight into fungal bioreactors, fungal biofilm and immobilization system. Biochar adsorption capacities for organic micropollutants removal under different operating conditions are summarized. Finally, few recommendations for further research are established in the context of the combination of fungal biofilm with the technologies relying on the adsorption by porous carbonaceous materials.

Characterization of Bacillus nealsonii strain KBH10 capable of reducing aqueous mercury in laboratory-scale reactor

The environmental release of mercury is continuously increasing with high degree of mobility, transformation and amplified toxicity. Improving remediation strategies is becoming increasingly important to achieve more stringent environmental safety standards. This study develops a laboratory-scale reactor for bioremediation of aqueous mercury using a biofilm-producing bacterial strain, KBH10, isolated from mercury-polluted soil. The strain was found resistant to 80 mg/L of HgCl₂ and identified as Bacillus nealsonii via 16S rRNA gene sequence analysis. The strain KBH10 was characterized for optimum growth parameters and its mercury biotransformation potential was validated through mercuric reductase assay. A packed-bed column bioreactor was designed for biofilm-mediated mercury removal from artificially contaminated water and residual mercury was estimated. Strain KBH10 could grow at a range of temperature (20-50 °C) and pH (6.0-9.0) with optimum temperature established at 30 °C and pH 7.0. The optimum mercuric reductase activity (77.8 ± 1.7 U/mg) was reported at 30 °C and was stable at a temperature range of 20-50 °C. The residual mercury analysis of artificially contaminated water indicated 60.6 ± 1.5% reduction in mercury content within 5 h of exposure. This regenerative process of biofilm-mediated mercury removal in a packed-bed column bioreactor can provide new insight into its potential use in mercury bioremediation.

Microbial biofilm ecology, in silico study of quorum sensing receptor-ligand interactions and biofilm mediated bioremediation

Biofilms are structured microbial communities of single or multiple populations in which microbial cells adhere to a surface and get embedded in extracellular polymeric substances (EPS). This review attempts to explain biofilm architecture, development phases, and forces that drive bacteria to promote biofilm mode of growth. Bacterial chemical communication, also known as Quorum sensing (QS), which involves the production, detection, and response to small molecules called autoinducers, is highlighted. The review also provides a brief outline of interspecies and intraspecies cell-cell communication. Additionally, we have performed docking studies using Discovery Studio 4.0, which has enabled our understanding of the prominent interactions between autoinducers and their receptors in different bacterial species while also scoring their interaction energies. Receptors, such as LuxN (Phosphoreceiver domain and RecA domain), LuxP, and LuxR, interacted with their ligands (AI-1, AI-2, and AHL) with a CDocker interaction energy of - 31.6083 kcal/mole; - 34.5821 kcal/mole, - 48.2226 kcal/mole and - 41.5885 kcal/mole, respectively. Since biofilms are ideal for the remediation of contaminants due to their high microbial biomass and their potential to immobilize pollutants, this article also provides an overview of biofilm-mediated bioremediation.

Co-biodegradation studies of naphthalene and phenanthrene using bacterial consortium

Degradation studies of phenanthrene and naphthalene as a mixture was carried out using a developed bacterial consortium. The isolates used in consortium were identified as Chryseobacterium sp., Sphingobacterium sp., Stenotrophomonas sp., Agromyces sp. and Pseudomonas sp. Limited work is done on genus Agromyces in degradation studies of PAHs. Catechol production was detected using Arnow's assay suggested that the pathway used for degradation is the meta-cleavage pathway. Results showed that Tween 80, as a surfactant, had maximum effect on the growth of isolates during PAH degradation. This suggests that use of Tween 80 as a surfactant enhanced the uptake of PAH by bacterial isolates during degradation. The study further revealed that, bacterial consortium was successfully utilized in the treatment of water contaminated with PAH in a laboratory-scale biofilm bioreactor. The bacterial consortium was able to degrade 99.9% of naphthalene and 92.9% of phenanthrene as a mixture at a high concentration of 2000 mg/L within 6 days. Further scaling up of the biofilm bioreactor can prove beneficial in large scale treatment of PAH contaminated water. This study showed promising results and these bacterial strains can be used as potential tools for bioremediation of PAH in contaminated sites.

Biofilm research within irrigation water distribution systems: Trends, knowledge gaps, and future perspectives

Biofilms in irrigation water distribution systems (IWDSs) play an essential role in spreading pathogens, chemical pollutants, and environmental pollutants into downstream irrigated crops and thus should be considered a potential threat to food safety. Although the role of biofilms in drinking water distribution systems has been extensively studied in the last decade, the research on IWDS biofilms in this period has been limited. This review identifies research gaps in the field of IWDS biofilms, provides perspectives on experimental designs for investigating IWDS biofilms, and suggests potential strategies worth pursuing in IWDS management. The current state of the art of IWDS biofilms is discussed, and an analysis of the challenges in IWDS biofilm research is presented. Furthermore, this review proposes useful advanced technologies that allow a practical, in-depth fundamental understanding of IWDS biofilms. In a nutshell, this article provides future directions and insights into detailed experimental designs on a relatively under-reported research topic: "IWDS biofilms."

From molecules to multispecies ecosystems: the roles of structure in bacterial biofilms

Biofilms are communities of sessile microbes that are bound to each other by a matrix made of biopolymers and proteins. Spatial structure is present in biofilms on many lengthscales. These range from the nanometer scale of molecular motifs to the hundred-micron scale of multicellular aggregates. Spatial structure is a physical property that impacts the biology of biofilms in many ways. The molecular structure of matrix components controls their interaction with each other (thereby impacting biofilm mechanics) and with diffusing molecules such as antibiotics and immune factors (thereby impacting antibiotic tolerance and evasion of the immune system). The size and structure of multicellular aggregates, combined with microbial consumption of growth substrate, give rise to differentiated microenvironments with different patterns of metabolism and gene expression. Spatial association of more than one species can benefit one or both species, while distances between species can both determine and result from the transport of diffusible factors between species. Thus, a widespread theme in the biological importance of spatial structure in biofilms is the effect of structure on transport. We survey what is known about this and other effects of spatial structure in biofilms, from molecules up to multispecies ecosystems. We conclude with an overview of what experimental approaches have been developed to control spatial structure in biofilms and how these and other experiments can be complemented with computational work.

Metal-Adapted Bacteria Isolated From Wastewaters Produce Biofilms by Expressing Proteinaceous Curli Fimbriae and Cellulose Nanofibers

Bacterial biofilm plays a pivotal role in bioremediation of heavy metals from wastewaters. In this study, we isolated and identified different biofilm producing bacteria from wastewaters. We also characterized the biofilm matrix [i.e., extracellular polymeric substances (EPS)] produced by different bacteria. Out of 40 isolates from different wastewaters, only 11 (27.5%) isolates (static condition at 28°C) and 9 (22.5%) isolates (agitate and static conditions at 28 and 37°C) produced air–liquid (AL) and solid–air–liquid (SAL) biofilms, respectively, only on salt-optimized broth plus 2% glycerol (SOBG) but not in other media tested. Biomass biofilms and bacteria coupled with AL biofilms were significantly (P ≤ 0.001) varied in these isolates. Escherichia coli (isolate ENSD101 and ENST501), Enterobacter asburiae (ENSD102), Enterobacter ludwigii (ENSH201), Pseudomonas fluorescens (ENSH202 and ENSG304), uncultured Vitreoscilla sp. (ENSG301 and ENSG305), Acinetobacter lwoffii (ENSG302), Klebsiella pneumoniae (ENSG303), and Bacillus thuringiensis (ENSW401) were identified based on 16S rRNA gene sequencing. Scanning electron microscope (SEM) images revealed that biofilm matrix produced by E. asburiae ENSD102, uncultured Vitreoscilla sp. ENSG301, A. lwoffii ENSG302, and K. pneumoniae ENSG303 are highly fibrous, compact, and nicely interlinked as compared to the biofilm developed by E. ludwigii ENSH201 and B. thuringiensis ENSW401. X-ray diffraction (XRD) results indicated that biofilm matrix produced by E. asburiae ENSD102, uncultured Vitreoscilla sp. ENSG301, and A. lwoffii ENSG302 are non-crystalline amorphous nature. Fourier transform infrared (FTIR) spectroscopy showed that proteins and polysaccharides are the main components of the biofilms. Congo red binding results suggested that all these bacteria produced proteinaceous curli fimbriae and cellulose-rich polysaccharide. Production of cellulose was also confirmed by Calcofluor binding- and spectrophotometric assays. E. asburiae ENSD102, Vitreoscilla sp. ENSG301, and A. lwoffii ENSG302 were tested for their abilities to form the biofilms exposure to 0 to 2000 mg/L of copper sulfate (for Cu), zinc sulfate (for Zn), lead nitrate (for Pb), nickel chloride (for Ni), and potassium dichromate (for Cr), several concentrations of these metals activated the biofilm formation. The polysaccharides is known to sequester the heavy metals thus, these bacteria might be applied to remove the heavy metals from wastewater.

Properties of Antibiotic-Resistant Bacteria Isolated from Onsite Wastewater Treatment Plant in Relation to Biofilm Formation

The aim of the present study was to determine some properties of antibiotic-resistant bacterial strains isolated from onsite wastewater technology in relation to biofilm formation, e.g., autoaggregation and motility. Additionally, biosurfactant production by the isolates was also evaluated. The ability of selected strains to develop a biofilm was assessed by using the crystal violet method, which allows to indirectly quantify the attached bacterial biomass (live, dead cells, and polysaccharides as well). Obtained results showed that 19 of the analyzed strains were able to produce biofilm after 72 h of incubation. The low values of surface tension in the range between 28 and 36 mN/m were observed in the bacteria, which are not able to produce biofilm or be classified as weak biofilm producers. Among biofilm-forming strains the highest autoaggregation index was observed for Mycobacterium brumae and Bacillus alcalophilus. Noteworthy, that some strains capable of biofilm formation showed no aggregation abilities or were characterized by low autoaggregative properties. The results of visual autoaggregation assay showed no visible flocs after given time of incubation. The results from motility test demonstrated that most of the analyzed strains were motile. Noteworthy, that up to now literature data about physiology, biofilm formation, and autoaggregative capabilities of bacteria isolated from onsite wastewater technology are very limited and this paper gives the information on the antibiotic-resistant bacteria with ability to form biofilm. Thus, the present study points to develop novel bioinocula in antibiotic degradation and to reach novel biofilm-dispersing agents produced by various bacteria that can be used as disinfectants or surface-coating agents to prevent microbial surface colonization and biofilm development.

Citrate Addition Increased Phosphorus Bioavailability and Enhanced Gasoline Bioremediation

Phosphorus (P) bioavailability often limits gasoline biodegradation in calcareous cold-region soils. One possible method to increase P bioavailability in such soils is the addition of citrate. Citrate addition at the field scale may increase hydrocarbon degradation by: (i) enhancing inorganic and organic P dissolution and desorption, (ii) increasing hydrocarbon bioavailability, and/or (iii) stimulating microbial activity. Alternatively, citrate addition may inhibit activity due to competitive effects on carbon metabolism. Using a field-scale in situ biostimulation study, we evaluated if citrate could stimulate gasoline degradation and what the dominant mechanism of this stimulation will be. Two large bore injectors were constructed at a site contaminated with gasoline, and a biostimulation solution of 11 mM MgSO, 1 mM HPO, and 0.08 mM HNO at pH 6.5 in municipal potable water was injected at ∼5000 L d for about 4 mo. Following this, 10 mM citric acid was incorporated into the existing biostimulation solution and the site continued to be stimulated for 8 mo. After citrate addition, the bioavailable P fraction in groundwater and soil increased. Iron(II) groundwater concentrations increased and corresponded to decreases in benzene, toluene, ethylbenzene, xylenes (BTEX) in groundwater, as well as a decrease in F1 in the soil saturated zone. Overall, citrate addition increased P bioavailability and may stimulate anaerobic microbial activity, resulting in accelerated anaerobic gasoline bioremediation in cold-region calcareous soils.

Biotreatment of industrial olive washing water by synergetic association of microalgal-bacterial consortia in a photobioreactor

This study presents an effective technology for the olive processing industry to remediate olive washing water. A 14.5-L enclosed tubular photobioreactor was inoculated with a stable microalgal-bacterial consortium obtained by screening strains well adapted to olive washing water. The capacity of an enclosed tubular photobioreactor to remove toxic compounds was evaluated under photosynthesis conditions and without any external supply of oxygen. The results showed that the dominant green microalgae Scenedesmus obliquus, Chlorella vulgaris and the cyanobacteria Anabaena sp. and bacteria present in olive washing water (i.e. Pantoea agglomerans and Raoultella terrigena) formed a synergistic association that was resistant to toxic pollutants present in the effluent and during the initial biodegradation process, which resulted in the breakdown of the pollutant. Total phenolic compounds, COD, BOD₅, turbidity and colour removals of 90.3 ± 11.4, 80.7 ± 9.7, 97.8 ± 12.7, 82.9 ± 8.4 and 83.3 ± 10.4 %, respectively, were recorded in the photobioreactor at 3 days of hydraulic retention time. Graphical abstract Biotreatment of industrial olive washing water by synergetic association of microalgal-bacterial consortia in a photobioreactor.

Metabolic Responses of Bacterial Cells to Immobilization

In recent years immobilized cells have commonly been used for various biotechnological applications, e.g., antibiotic production, soil bioremediation, biodegradation and biotransformation of xenobiotics in wastewater treatment plants. Although the literature data on the physiological changes and behaviour of cells in the immobilized state remain fragmentary, it is well documented that in natural settings microorganisms are mainly found in association with surfaces, which results in biofilm formation. Biofilms are characterized by genetic and physiological heterogeneity and the occurrence of altered microenvironments within the matrix. Microbial cells in communities display a variety of metabolic differences as compared to their free-living counterparts. Immobilization of bacteria can occur either as a natural phenomenon or as an artificial process. The majority of changes observed in immobilized cells result from protection provided by the supports. Knowledge about the main physiological responses occurring in immobilized cells may contribute to improving the efficiency of immobilization techniques. This paper reviews the main metabolic changes exhibited by immobilized bacterial cells, including growth rate, biodegradation capabilities, biocatalytic efficiency and plasmid stability.