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Biofilms are assemblages of bacteria embedded within a matrix of extracellular polymeric substances (EPS) attached to a substratum. The process of biofilm formation is a complex phenomenon regulated by the intracellular and intercellular signaling systems. Various secondary messenger molecules such as cyclic dimeric guanosine 3′,5′-monophosphate (c-di-GMP), cyclic adenosine 3′,5′-monophosphate (cAMP), and cyclic dimeric adenosine 3′,5′-monophosphate (c-di-AMP) are involved in complex signaling networks to regulate biofilm development in several bacteria. Moreover, the cell to cell communication system known as Quorum Sensing (QS) also regulates biofilm formation via diverse mechanisms in various bacterial species. Bacteria often switch to the biofilm lifestyle in the presence of toxic pollutants to improve their survivability. Bacteria within a biofilm possess several advantages with regard to the degradation of harmful pollutants, such as increased protection within the biofilm to resist the toxic pollutants, synthesis of extracellular polymeric substances (EPS) that helps in the sequestration of pollutants, elevated catabolic gene expression within the biofilm microenvironment, higher cell density possessing a large pool of genetic resources, adhesion ability to a wide range of substrata, and metabolic heterogeneity. Therefore, a comprehensive account of the various factors regulating biofilm development would provide valuable insights to modulate biofilm formation for improved bioremediation practices. This review summarizes the complex regulatory networks that influence biofilm development in bacteria, with a major focus on the applications of bacterial biofilms for environmental restoration. [ABSTRACT FROM AUTHOR]

Rubber wastewater contains variable low pH with a high load of nutrients such as nitrogen, phosphorous, suspended solids, high biological oxygen demand (BOD), and chemical oxygen demand (COD). Ureolytic and biofilm-forming bacterial strains Bacillus sp. OS26, Bacillus cereus OS36, Lysinibacillus macroides ST13, and Burkholderia multivorans DF12 were isolated from rubber processing centres showed high urease activity. Microscopic analyses evaluated the structural organization of biofilm. Extracellular polymeric substances (EPS) matrix of the biofilm of the strains showed the higher abundance of polysaccharides and lipids which help in the attachment and absorption of nutrients. The functional groups of polysaccharides, proteins, and lipids present in EPS were revealed by ATR-FTIR and 1H NMR. A consortium composed of B. cereus OS36, L. macroides ST13, and B. multivorans DF12 showed the highest biofilm formation, and efficiently reduced 62% NH 3 , 72% total nitrogen, and 66% PO 4 3−. This consortium also reduced 76% BOD, 61% COD, and 68% TDS. After bioremediation, the pH of the remediated wastewater increased to 11.19. To reduce the alkalinity of discharged wastewater, CaCl 2 and urea were added for calcite reaction. The highest CaCO 3 precipitate was obtained at 24.6 mM of CaCl 2 , 2% urea, and 0.0852 mM of nickel (Ni2+) as a co-factor which reduced the pH to 7.4. The elemental composition of CaCO 3 precipitate was analyzed by SEM-EDX. XRD analysis of the bacterially-induced precipitate revealed a crystallinity index of 0.66. The resulting CaCO 3 precipitate was used as soil stabilizer. The precipitate filled the void spaces of the treated soil, reduced the permeability by 80 times, and increased the compression by 8.56 times than untreated soil. Thus, CaCO 3 precipitated by ureolytic and biofilm-forming bacterial consortium through ureolysis can be considered a promising approach for neutralization of rubber wastewater and soil stabilization. [Display omitted] • Biofilm-forming ureolytic bacterial consortia efficiently remediate rubber wastewater. • The pH of the wastewater was increased after bioremediation. • CaCl 2 and Ni2+ induced a high rate of calcium carbonate precipitation. • Calcium carbonate precipitate reduced the pH of the wastewater to a neutral level. • CaCO 3 precipitate treatment reduced permeability and increased compression of soil. [ABSTRACT FROM AUTHOR]

Bacteria thrive in biofilms embedding in the three-dimensional extracellular polymeric substances (EPS). Functional Amyloid in Pseudomonas (Fap), a protein in EPS, efficiently sequesters polycyclic aromatic hydrocarbons (PAHs). Present study reports the characterization of Fap fibrils from Pseudomonas aeruginosa PFL-P1 and describes the interaction with pyrene to assess the impact on pyrene degradation. Overexpression of fap in E. coli BL21(DE3) cells significantly enhances biofilm formation (p < 0.0001) and amyloid production (p = 0.0002), particularly with pyrene. Defibrillated Fap analysis reveals FapC monomers and increased fibrillation with pyrene. Circular Dichroism (CD), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) unveil characteristic amyloid peaks and structural changes in Fap fibrils upon pyrene exposure. 3D-EEM analysis identifies a protein-like fluorophore in Fap fibrils, exhibiting pyrene-induced fluorescence quenching. Binding constants range from 5.23 to 7.78 M−1, with ΔG of −5.10 kJ mol−1 at 298 K, indicating spontaneous and exothermic interaction driven by hydrophobic forces. Exogenous Fap fibrils substantially increased the biofilm growth and pyrene degradation by P. aeruginosa PFL-P1 from 46 % to 64 % within 7 days (p = 0.0236). GC–MS identifies diverse metabolites, implying phthalic acid pathway in pyrene degradation. This study deepens insights into structural dynamics of Fap fibrils when exposed to pyrene, offering potential application in environmental bioremediation. [Display omitted] • Functional amyloid from P. aeruginosa PFL-P1 showed increased fibrillation with pyrene. • CD, FTIR, and XRD revealed amyloid peaks and pyrene-induced structural changes. • Fap fibrils spontaneously interact with pyrene through hydrophobic forces. • Pyrene binds to Fap fibrils at multiple sites with binding constants of 5.23–7.78 M−1. • Exogenous Fap fibrils enhanced biofilm-mediated pyrene degradation from 46 % to 64 %. [ABSTRACT FROM AUTHOR]

Marine environment is a dynamic habitat for survival of many microbes with unique metabolic potential. Biofilm formation benefits the marine bacteria to thrive and persist even in hostile environments. Besides, biofilm formation ability of bacteria enhances the efficiency of bioremediation of organic pollutants. In the present study, biofilm forming and polycyclic aromatic hydrocarbon (phenanthrene and pyrene) degrading bacteria were isolated and taxonomic identification was carried out by 16S rRNA gene sequencing. The isolates were able to grow on multiple aromatic hydrocarbons such as toluene, biphenyl, anthracene and naphthalene. The potential isolates were characterized by 16S rRNA gene sequencing. The isolates were identified and belong to the genera Pseudomonas, Stenotrophomonas, Paenibacillus, Alcaligenes, Sporosarcina and Lysinibacillus. Proteobacteria were found to be leading bacterial group at the pollutant sites. 75% of the isolates screened were able to establish biofilm and grow on either of aromatic hydrocarbon. This study shows the dominance of biofilm forming bacteria with ability to grow on multiple organic compounds in the marine environment. [ABSTRACT FROM AUTHOR]

Biofilm formation in bacteria is strongly affected by the nature of substrata. Different substrata such as glass, polystyrene, steel, ceramic, and rubber were used to assess the biofilm forming ability of a marine bacterium Pseudomonas aeruginosa PFL‐P1 using a scanning electron microscope (SEM), atomic force microscope (AFM), and confocal laser scanning microscope (CLSM). The bacterium formed dense biofilms with varied aggregation on different substrata. SEM study revealed small rod‐shaped cells with diverse arrangements within the biofilms on all the substrata under study. The AFM study revealed the highest roughness of 545 nm on the ceramic substratum. The biofilms formed on ceramic substratum were characterized with maximum roughness (742 nm), maximum peak height (1,480 nm), and maximum arithmetic mean height (611 nm), significantly higher than all the other substrata (p <.05). AFM studies confirmed that P. aeruginosa PFL‐P1 exhibited biofilm heterogeneity on all the substrata. The CLSM study indicated a higher fraction of nucleic acids to α‐polysaccharides ratio in the biofilms. COMSTAT analysis revealed the highest biofilm biomass of ~18 μm3/μm2 on the ceramic substratum. The maximum biofilm thickness of ~50 μm in the native state on the ceramic substratum was significantly higher than glass (p =.0015), polystyrene (p =.0001), steel (p =.0035), and rubber substrata (p =.0001). The higher surface roughness of ceramic substratum is accountable for more area for colonization, as evident from higher biomass and thickness of the biofilm. This study provides insight into the substratum properties, which modulate the biofilm forming ability in bacteria. [ABSTRACT FROM AUTHOR]

Biofilm forming and heavy metal resistant marine bacterial strain Pseudomonas chengduensis PPSS-4 was isolated from the contaminated marine sediment of Paradip Port, Odisha, India. The strain showed biofilm formation up to 100 mg/L of multi-metal [Pb(II), Cr(VI), and Cd(II)] supplementation in the culture medium. Scanning electron microscopy (SEM) showed aggregation of rod-shaped cells in the extracellular polymeric substance (EPS) matrix of biofilm. Confocal laser scanning microscopy (CLSM) exhibited a higher nucleic acid to the α-polysaccharide ratio in the biofilm, and the observed thickness was ~21 µm. The metal uptake potential of biofilm culture was higher than planktonic culture both in single and multi-metal solutions. FESEM-EDS analysis revealed the sequestration of multi-metals by bacterial cells and biofilm-EPS. FTIR analysis of bacterial EPS further ensured the interaction of functional groups such as –OH, –NH, and P=O with the metal ions. The maximum removal of Pb, Cr, and Cd by the bacterial biomass was observed at 37°C within 4 h of contact time at pH 6, and 4% salinity for Pb and Cr, and 6% salinity for Cd. The present study revealed that the marine bacterium P. chengduensis PPSS-4 can remove multi-metals, and this bacterium could be efficiently utilized for the remediation of heavy metals in the contaminated environment. [ABSTRACT FROM AUTHOR]

Rubber latex wastewater contains high level of inorganic anions such as nitrate and phosphate which are more prevalent as groundwater contaminant. The applicability of biofilm forming bacterial isolates to treat rubber latex wastewater was investigated. Microscopic analyses (CLSM and SEM) evaluated that the major component of biofilm other than bacterial cell is EPS matrix. EPS was found to contain higher proportion of lipids and polysaccharide which are required for attachment and absorption of nutrients. ATR‐FTIR and 1H NMR revealed the functional groups present in EPS. Rhodococcus rhodochrous CTI‐14 showed robust biofilm followed by Cellulosimicrobium sp. CTB‐10. Out of six bacterial consortia tested, consortium‐D efficiently removed 95% NO3-–N and 75% PO43-. Taguchi method revealed the optimum parameters to remove the nutrients. The consortium‐D optimally reduced nitrate and phosphate at pH 7 at 37°C. Consortium‐D composed of Cellulosimicrobium sp. CTB‐10, Aeromonas veronii OS‐01, Lysinibacillus sphaericus RTA‐01 and Rhodococcus rhodochrous CTI‐14 was found to be the most efficient bacterial consortium to treat rubber latex wastewater. [ABSTRACT FROM AUTHOR]

Increasing usage of plastic has led to the deposition of plastic in the environment which later become microplastic, a pollutant of global concern. These polymeric particles affect the ecosystem by increasing ecotoxicity and impeding the biogeochemical cycles. Besides, microplastic particles have been known for their role in aggravating the effect of various other environmental pollutants including organic pollutants and heavy metals. These microplastic surfaces are often colonized by the microbial communities also known as "plastisphere microbes" forming biofilms. These microbes include cyanobacteria like Nostoc , Scytonema , etc., and diatoms like Navicula , Cyclotella , etc. which become the primary colonizer. In addition to the autotrophic microbes, Gammaproteobacteria and Alphaproteobacteria dominate the plastisphere microbial community. These biofilm-forming microbes can efficiently degrade the microplastic in the environment by secreting various catabolic enzymes such as lipase, esterase, hydroxylase, etc. Besides, these microbes have shown great potential for the bioconversion of microplastic to polyhydroxyalkanoates (PHA), an energy efficient and sustainable alternative to the petroleum based plastics. Thus, these microbes can be used for the creation of a circular economy using waste to wealth strategy. This review provides a deeper insight into the distribution, transportation, transformation, and biodegradation of microplastic in the ecosystem. The formation of plastisphere by the biofilm-forming microbes has been described in the article. In addition, the microbial metabolic pathways and genetic regulations involved in the biodegradation have been discussed in detail. The article suggests the microbial bioremediation and upcycling of microplastic along with various other strategies to effectively mitigate the microplastic pollution. [Display omitted] • Microplastics are ubiquitous environmental pollutants. • Microplastic surfaces are colonized by biofilm-forming plastisphere microbes. • Plastisphere microbes can efficiently degrade the microplastic in the environment. • The genetic regulation and metabolism help the microbes in biodegradation. • Various microbes have the potential for the bioconversion of microplastic to PHA. [ABSTRACT FROM AUTHOR]

The quorum sensing (QS) phenomenon regulates a myriad of pathogenic traits in the biofilm forming fish pathogen,Aeromonas hydrophila. Blocking the QS mechanism ofA. hydrophilais a novel strategy to prevent disease in fish. This study evaluated the effect of tannic acid, a QS inhibitor, onA. hydrophila-associated QS regulated phenomena. A streaking assay withChromobacterium violaceum(CVO26) reported the presence of N-acyl homoserine lactone (AHL) inA. hydrophila, which was confirmed by HPLC and GC-MS analysis. Tannic acid-treatedA. hydrophilashowed a considerable reduction in violacein production, blood haemolysis activity and the pattern of swarming motility. Biofilm formation was significantly reduced (p< 0.001) (up to 95%), after tannic acid treatment for 48 h. Analysis by qRT-PCR revealed significant downregulation (p< 0.001) of AhyI and AhyR transcripts inA. hydrophilaafter tannic acid treatment. Co-stimulation ofCatla catlawithA. hydrophilaand tannic acid attenuated pathogen-induced skin haemorrhages and increased the relative survival rate up to 86.6%. The study provides a mechanistic basis of tannic acid as a QS blocker and indicates its therapeutic potential againstA. hydrophila-induced pathogenesis. [ABSTRACT FROM AUTHOR]

Increased contamination of the environment with toxic pollutants has paved the way for efficient strategies which can be implemented for environmental restoration. The major problem with conventional methods used for cleaning of pollutants is inefficiency and high economic costs. Bioremediation is a growing technology having advanced potential of cleaning pollutants. Biofilm formed by various micro-organisms potentially provide a suitable microenvironment for efficient bioremediation processes. High cell density and stress resistance properties of the biofilm environment provide opportunities for efficient metabolism of number of hydrophobic and toxic compounds. Bacterial biofilm formation is often regulated by quorum sensing (QS) which is a population density-based cell–cell communication process via signaling molecules. Numerous signaling molecules such as acyl homoserine lactones, peptides, autoinducer-2, diffusion signaling factors, and α-hydroxyketones have been studied in bacteria. Genetic alteration of QS machinery can be useful to modulate vital characters valuable for environmental applications such as biofilm formation, biosurfactant production, exopolysaccharide synthesis, horizontal gene transfer, catabolic gene expression, motility, and chemotaxis. These qualities are imperative for bacteria during degradation or detoxification of any pollutant. QS signals can be used for the fabrication of engineered biofilms with enhanced degradation kinetics. This review discusses the connection between QS and biofilm formation by bacteria in relation to bioremediation technology. [ABSTRACT FROM AUTHOR]

Increasing level of polycyclic aromatic hydrocarbons (PAHs) in the environment results in environmental pollution. Microbial biofilm-mediated bioremediation has been widely used as an attractive approach to mitigate PAHs contamination in the ecosystem. Amyloid, a proteinaceous component of biofilm-associated extracellular polymeric substances (EPS), forms an integral strengthening part of the biofilm. This study aims to determine the interaction of functional amyloid in Pseudomonas (Fap) with two different PAHs (phenanthrene and pyrene). The production of amyloid by the marine bacterium Pseudomonas aeruginosa PFL-P1 was confirmed by Congo red (CR) assay, thioflavin T (ThT) staining method and amplification of fapC gene. The expression of fapC was up-regulated six folds (p < 0.0001) when phenanthrene and pyrene were used as the sole carbon source. The molecular docking of modelled FapC revealed a strong binding energy of − 7.0 and − 6.75 kcal/mol with phenanthrene and pyrene, respectively. Confocal laser scanning microscopic (CLSM) analysis indicated a significant increase in amyloid percentage during biofilm formation by P. aeruginosa PFL-P1 in the presence of phenanthrene and pyrene (p < 0.0001). The increased expression of the fapC gene and the potent hydrophobic interaction between the FapC protein and the PAH molecules suggest the essential role of this protein in PAH binding. [Display omitted] • Marine bacterium Pseudomonas aeruginosa PFL-P1 showed amyloid-producing ability. • Amyloid production increased under polycyclic aromatic hydrocarbon stress. • fapC encodes the major amyloid protein in Pseudomonas. • In silico study revealed β-sheet-rich region in the tertiary structure of FapC. • FapC was found to interact hydrophobically with polycyclic aromatic hydrocarbon. [ABSTRACT FROM AUTHOR]

[Display omitted] • Moving biofilm in MBBR is advantageous over fixed biofilm of other bioreactors. • Hydraulic shear force influences biofilm structure and stability. • Anammox-n-DAMO coupled processes can improve nitrogen removal efficiencies. • Nature of carrier surface affects biofilm growth in MBBR. • Hybrid MBBR systems can be beneficial for improved wastewater treatment. Among the several biofilm-based bioreactors, moving bed biofilm reactors (MBBR) have been extensively used for wastewater treatment due to low operational costs, technical feasibility, and stability. Biofilm forming strains, e.g., Stenotrophomonas maltophila DQ01, achieved 94.21% simultaneous nitrification and denitrification (SND) and 94.43% removal of total nitrogen (TN) at a cycle time of 7 h, and a biofilm consortium consisting of Chryseobacterium sp. and Rhodobacter sp. achieved 86.8% removal of total organic carbon (TOC) at hydraulic retention time (HRT) of 24 h using lab-scale MBBR. Modifications in the surface properties of the biocarrier materials achieved 99.5 ± 1.1% chemical oxygen demand (COD) and 93.6 ± 2.3% NH 4 +-N removal, significantly higher than the conventional commercial carrier. This review article summarizes the application of MBBR technology for wastewater treatment. The importance of bacterial biofilm and extracellular polymeric substances (EPS), anammox-n-DAMO coupled processes, and carrier surface modifications in MBBR technology have also been discussed. [ABSTRACT FROM AUTHOR]

The contribution of immobilized biofilm associated extracellular polymeric substances (EPS) of a marine bacterium Pseudomonas aeruginosa N6P6 in sequestering Pb(II) was investigated. The interaction between extracellular polymeric substances (EPS) and Pb(II) during the sorption process of Pb(II) was investigated using three-dimensional excitation-emission matrix (3D-EEM) and atomic absorption spectroscopy. 3D-EEM showed that the intensities of protein (PN) like fluorophores decreased during the Pb(II) sorption process. The interaction of Pb(II) and EPS fluorophore occurs spontaneously (ΔG = −13.79 kJ/K/mol) at 25 °C with a binding constant value of 5.67 l mol −1 . Through comparison of Pb(II) sequestration on immobilized live biomass and pristine alginate beads, we found that immobilized biofilm derived EPS contribute significantly to Pb(II) sequestration. The biosorption was studied by varying pH from 3 to 8 and initial Pb(II) concentration from 100 to 600 mg l −1 to find out the optimized conditions for maximum Pb(II) removal by various biosorbents. The Pb(II) biosorption capacity of the EPS alginate beads was significantly higher (416.67 mg g −1 ) than that of alginate biomass beads (232.55 mg g −1 ) and pristine alginate beads (120.48 mg g −1 ) (P < 0.05; One way ANOVA and Tukey’s HSD test). The maximum adsorption of Pb(II) on all the prepared biosorbents were observed at pH 6. Two equilibrium models, Langmuir and Freundlich, were used for computing the efficiency of Pb(II) binding by the developed biosorbents. The adsorption isotherms, Langmuir and the Freundlich type models were found to exhibit good fit (R 2 = 0.99) to the experimental data. The reusability of the EPS alginate biosorbent was studied by Pb adsorption (68.33%) and desorption (66.8%) from contaminated water after three adsorption/desorption cycle. [ABSTRACT FROM AUTHOR]

Three-dimensional excitation-emission matrix (3D EEM) fluorescence spectroscopy and attenuated total reflectance fourier-transformed infrared spectroscopy (ATR-FTIR) was used to evaluate the interaction of biofilm associated extracellular polymeric substances (EPS) of a marine bacterium Pseudomonas pseudoalcaligenes NP103 with lead [Pb(II)]. EEM fluorescence spectroscopic analysis revealed the presence of one protein-like fluorophore in the EPS of P . pseudoalcaligenes NP103. Stern-Volmer equation indicated the existence of only one binding site (n = 0.789) in the EPS of P . pseudoalcaligenes NP103. The interaction of Pb(II) with EPS was spontaneous at room temperature (∆ G = − 2.78 kJ/K/mol) having binding constant (K b ) of 2.59 M − 1 . ATR-FTIR analysis asserted the involvement of various functional groups such as sulphydryl, phosphate and hydroxyl and amide groups of protein in Pb(II) binding. Scanning electron microscopy (SEM) and fluorescence microscopy analysis displayed reduced growth of biofilm with altered surface topology in Pb(II) supplemented medium. Energy dispersive X-ray spectroscopy (EDX) analysis revealed the entrapment of Pb in the EPS. Uronic acid, a characteristic functional group of biofilm, was observed in 1 H NMR spectroscopy. The findings suggest that biofilm associated EPS are perfect organic ligands for Pb(II) complexation and may significantly augment the bioavailability of Pb(II) in the metal contaminated environment for subsequent sequestration. [ABSTRACT FROM AUTHOR]

Effect of exogenous N-acyl homoserine lactones (AHLs) on biofilm growth, cell surface hydrophobicity, auto-aggregation and polycyclic aromatic hydrocarbons (PAHs) degradation potential of two marine Pseudomonas isolates ( Pseudomonas pseudoalcaligenes NP103 and Pseudomonas aeruginosa N6P6) were evaluated in the present study. Increased biofilm growth, auto-aggregation and swarming motility was observed in the presence of exogenous AHLs (3OC8-HSL and 3OC12-HSL) resulting in enhanced phenanthrene and pyrene degradation. P. pseudoalcaligenes NP103 biofilm was able to degrade up to 79% of phenanthrene and 49% pyrene in 7 d whereas 85.6% phenanthrene and 47.56% pyrene degradation was achieved using P. aeruginosa N6P6 biofilm. 3OC8-HSL significantly ( P < 0.05; Tukey’s HSD test) potentiated the phenanthrene and pyrene degradation by P. pseudoalcaligenes NP103 biofilm (89% and 65.5%), whereas the phenanthrene and pyrene degradation potential of P. aeruginosa N6P6 biofilm increased significantly ( P < 0.05; Tukey’s HSD test) in presence of 3OC12-HSL (97.4% and 54.39%). Furthermore, the degradation achieved by both the isolates in presence of tannic acid, a quorum sensing inhibitor (QSI), was highest in presence of 3OC12-HSL suggesting the most pronounced effect of long chain AHL in degradation of phenanthrene and pyrene. Both the isolates followed catechol pathway for PAHs degradation. The findings suggest that AHL can significantly affect the biodegradation performance specifically when bacteria are present in abundant numbers in biofilms. [ABSTRACT FROM AUTHOR]

Biofilm-forming bacteria adhere to the substrates and engage in the nutrient cycling process. However, environmental conditions may interrupt the biofilm formation ability, which ultimately may affect various biogeochemical cycles. The present study reports the effect of varying pH and subsequent change in pCO 2 on the survivability, biofilm formation, and synthesis of extracellular polymeric substances (EPS) of a biofilm-forming marine bacterium Bacillus stercoris GST-03 isolated from the Bhitarkanika mangrove ecosystem, Odisha, India. Understanding the pH-dependent alteration in EPS constituents, and associated functional groups of a marine bacterium will provide better insight into the adaptability of the bacteria in future ocean acidification scenarios. The strain was found to tolerate and form biofilm up to pH 4, with the maximum biofilm formation at pH 6. EPS yield and the synthesis of the key components of the EPS, including carbohydrate, protein, and lipid, were found maximum at pH 6. Changes in biofilm formation patterns and various topological parameters at varying pH/pCO 2 conditions were observed. A cellular chaining pattern was observed at pH 4, and maximum biofilm formation was obtained at pH 6 with biomass of 5.28582 ± 0.5372 μm3/μm2 and thickness of 9.982 ± 1.5288 μm. Structural characterization of EPS showed changes in various functional groups of constituent macromolecules with varying pH. The amorphous nature of the EPS and the changes in linkages and associated functional groups (-R 2 CHOR, –CH 3 , and –CH 2) with pH variation was confirmed. EPS showed a two-step degradation with a maximum weight loss of 59.147% and thermal stability up to 480 °C at pH 6. The present work efficiently demonstrates the role of EPS in providing structural and functional stability to the biofilm in varying pH conditions. The findings will provide a better understanding of the adaptability of marine bacteria in the future effect of ocean acidification. [ABSTRACT FROM AUTHOR]

Biofilm-forming marine bacterial isolates Paenibacillus lautus NE3B01, Pseudomonas mendocina NR802, Stenotrophomonas acidaminiphila NCW702 and Pseudomonas pseudoalcaligenes NP103 in microbial fuel cell (MFC) were investigated for low-voltage power generation. Biofilm formation by the isolates was evaluated by glass tube assay, microtitre plate assay and fluorescence microscopy. A dual chamber MFC of 2 litre capacity was constructed for low-voltage power generation and current output. Two chambers were internally connected by salt bridge and externally the circuit was connected with copper wires which were joined to the electrodes at the two ends and to the multimeter. Maximum current was generated when the salt bridge was constructed using 1 M KCl for all the four bacterial isolates. With Paenibacillus lautus NE3B01, a maximum voltage of 727.5 ± 13.4 mV in 6 h with 7 g/l of glucose as the sole source of carbon was recorded. However, Pseudomonas mendocina NR802 MFC was the most stable in terms of potential generation among all the isolates used for MFC studies. The experimental data for current and voltage showed that the biofilm-forming marine bacterial isolates are useful in MFC technology. [ABSTRACT FROM AUTHOR]

Salmonella spp. are facultative anaerobic, Gram-negative, rod-shaped bacteria and belongs to the Enterobacteriaceae family. Although much has been known about Salmonella pathogenesis, the functional characterizations of certain genes are yet to be explored. The rspA (STM14_1818) is one such gene with putative dehydratase function, and its role in pathogenesis is unknown. The background information showed that rspA gene is upregulated in Salmonella when it resides inside macrophages, which led us to investigate its role in Salmonella pathogenesis. We generated the rspA knockout strain and complement strain in S. Typhimurium 14028. Ex-vivo and in-vivo infectivity was looked at macrophage and epithelial cell lines and Caenorhabditis elegans (C. elegans). The mutant strain differentially formed the biofilm at different temperatures by altering the expression of genes involved in the synthesis of cellulose and curli. Besides, the mutant strain is hyperproliferative intracellularly and showed increased bacterial burden in C. elegans. The mutant strain became more infectious and lethal, causing faster death of the worms than the wild type, and also modulates the worm's innate immunity. Thus, we found that the rspA deletion mutant was more pathogenic. In this study, we concluded that the rspA gene differentially regulates the biofilm formation in a temperature dependent manner by modulating the genes involved in the synthesis of cellulose and curli and negatively regulates the Salmonella virulence for longer persistence inside the host. • The rspA gene regulates the biofilm formation in a temperature-dependent manner. • The rspA mutant strain is less invasive but more proliferative intracellularly. • The rspA mutant strain is hyper-infectious and more lethal to C. elegans. • The rspA gene negatively regulates the virulence of S. Typhimurium. [ABSTRACT FROM AUTHOR]

Increased tolerance to toxic pollutants and enhanced degradation capabilities of the bacterial biofilm is often attributed to the matrix of extracellular polymeric substances (EPS). This biopolymeric matrix provides structure, stability, and shelter to the cells within a biofilm and the major constituent of this matrix is exopolysaccharides. However, the role of EPS extends beyond offering protection to the bacterial cells under stress. Bacterial EPS exhibits a double-layered structure consisting of the loosely bound EPS (LB-EPS) and the tightly bound EPS (TB-EPS). Both these EPS layers interact with noxious environmental pollutants through emulsification, solubilization, binding, precipitation, complexation, and ion exchange. Different functional groups of EPS, such as carboxyl, amide, phosphoryl, and hydroxyl, are involved in the removal of toxic pollutants from contaminated environments. Biofilm-EPS participate in several remedial functions such as sequestration of heavy metals, emulsification of petroleum hydrocarbons, binding and solubilization of polycyclic aromatic hydrocarbons (PAHs), and sorption and degradation of dyes and pesticides. Thus, bacterial biofilm and EPS present an attractive solution for decontaminating heavily polluted environments. This review discusses a comprehensive account of biofilm physiology, EPS components, and synthesis mechanisms of exopolysaccharides. The interaction mechanisms of bacterial biofilm and EPS with pollutants have been discussed in detail, and the application of biofilm-forming bacteria and associated EPS in the bioremediation of the environment has been summarized. A deeper understanding of the bacterial biofilm and EPS-mediated pollutant removal will help develop technologies for field-scale applications. [Display omitted] • Bacterial biofilm exhibits increased tolerance to toxic environments. • EPS imparts functional and mechanical stability to the biofilm. • EPS-metal interaction occurs via complexation, precipitation and ion exchange. • Biofilm-EPS enhances the bioavailability of hydrophobic pollutants to cells. • Commercialization of the technology is needed for large-scale applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] The present study illustrates the involvement of divalent ions (Ca2+ and Mg2+) in biofilm mediated phenanthrene degradation. [•] Biofilm forming potential of marine bacterium Pseudomonas mendocina NR802 was evaluated at various concentrations of Ca2+ and Mg2+. [•] Increased exopolysaccharide production was observed when biofilm was grown in presence of 20mM Ca2+. [•] There was 15% increase in degradation of phenanthrene by biofilm grown in the presence of Ca2+. [•] The finding propose essential role of Ca2+, biofilm and associated extracellular polymeric substances in biodegradation of organic pollutants in marine environment. [Copyright &y& Elsevier]