Sugar composition and FT-IR analysis of exopolysaccharides produced by microbial isolates from paper mill slime deposits

Brevundimonas vesicularis Peritonitis in a Chronic Peritoneal Dialysis Patient

Gram-negative peritonitis in chronic peritoneal dialysis patients is difficult to treat and may result in catheter loss. Brevundimonas vesicularis is a Gram-negative rod bacterium which rarely causes infections in humans. A 41-year-old male receiving continuous cycling peritoneal dialysis for 5 months developed culture-negative peritonitis. He failed initial empiric treatment with intraperitoneal vancomycin and levofloxacin and thereafter intravenous gentamicin. B. vesicularis resistant to levofloxacin was isolated from the peritoneal fluid 21 days after his initial symptoms. Despite treatment with intravenous ceftriaxone and oral amoxicillin-clavulanate, the infection persisted, which required removal of the peritoneal catheter in order to cure this infection. We describe the features of B. vesicularis infection in our patient and the rarely reported additional cases.

Protective Effect of an Exopolysaccharide Produced by Lactiplantibacillus plantarum BGAN8 Against Cadmium-Induced Toxicity in Caco-2 Cells

Cadmium (Cd) ranks seventh on the list of most significant potential threats to human health based on its suspected toxicity and the possibility of exposure to it. It has been reported that some bacterial exopolysaccharides (EPSs) have the ability to bind heavy metal ions. We therefore investigated the capacity of eight EPS-producing lactobacilli to adsorb Cd in the present study, and Lactiplantibacillus plantarum BGAN8 was chosen as the best candidate. In addition, we demonstrate that an EPS derived from BGAN8 (EPS-AN8) exhibits a high Cd-binding capacity and prevents Cd-mediated toxicity in intestinal epithelial Caco-2 cells. Simultaneous use of EPS-AN8 with Cd treatment prevents inflammation, disruption of tight-junction proteins, and oxidative stress. Our results indicate that the EPS in question has a strong potential to be used as a postbiotic in combatting the adverse effects of Cd. Moreover, we show that higher concentrations of EPS-AN8 can alleviate Cd-induced cell damage.

Slime control in paper mill using biological agents as biocides

The environmental conditions of paper mills are suitable for the growth of slime-forming microorganisms due to the supply of nutrients, favorable temperature, and moisture. The slime formation causes the spoilage of raw materials & additives, breaks in the paper during papermaking, loss of production, reduces the hygienic quality of the end products, produces off-spec and rejected products, creates microbiological corrosion, and produces harmful gases. The main microorganisms are Bacteria (mainly Bacillus spp., Achromobacter spp., Enterobacter spp., Pseudomonas spp., Clostridium, etc.), Fungi (Aspergillus, Penicillium, Saccharomyces, etc.), and Algae. Besides the use of conventional toxic chemical biocides or slimicides, slime formation can also be controlled in an eco-friendly way using enzymes, bacteriophages, biodispersants, and biocontrol agents alone or along with biocides to remove the slime. Enzymes have shown their effectiveness over conventional chemicals due to nontoxic and biodegradable nature to provide clean and sustainable technology. Globally enzymes are being used at some of the paper mills and many enzymatic products are presently being prepared and under the trail at laboratory scale. The specificity of enzymes to degrade a specific substrate is the main drawback of controlling the mixed population of microorganisms present in slime. The enzyme has the potential to provide the chemical biocide-free solution as a useful alternative in the future with the development of new technologies. Microorganisms control in the paper mill may appear as a costly offer but the cost of uncontrolled microbial growth can be much higher leading to slime production and large economic drain.

Isolation, Optimization of Fermentation Conditions, and Characterization of an Exopolysaccharide from Pseudoalteromonas agarivorans Hao 2018

In recent years, the wide application of exopolysaccharides (EPSs) in food, cosmetics, medicine, and other fields has drawn tremendous attention. In this study, an EPS produced by Pseudoalteromonas agarivorans Hao 2018 was isolated and purified, and its fermentation conditions were optimized. Its structure and biological functions were also studied. The purity and molecular weight of EPS were determined by high performance liquid chromatography (HPLC), and the EPS exhibited a number average of 2.26 × 10⁵ and a weight average of 2.84 × 10⁵. EPS has good adsorption for Cu²⁺ and Pb²⁺. The adsorption rates can reach up to 69.79% and 82.46%, respectively. The hygroscopic property of EPS was higher than that of chitosan, but slightly lower than that of sodium hyaluronate. However, the water-retaining activity of EPS was similar to that of chitosan and sodium hyaluronate. EPS has strong ability to scavenge free radicals, including OH radical and O²⁻ radical. Further, its activity on O²⁻ radicals has similarities with that of vitamin C. EPS has broad application prospects in many fields, such as cosmetics, environmental protection.

Classification of Clinical Isolates of Klebsiella pneumoniae Based on Their in vitro Biofilm Forming Capabilities and Elucidation of the Biofilm Matrix Chemistry With Special Reference to the Protein Content

Klebsiella pneumoniae is a human pathogen, capable of forming biofilms on abiotic and biotic surfaces. The limitations of the therapeutic options against Klebsiella pneumoniae is actually due to its innate capabilities to form biofilm and harboring determinants of multidrug resistance. We utilized a newer approach for classification of biofilm producing Klebsiella pneumoniae isolates and subsequently we evaluated the chemistry of its slime, more accurately its biofilm. We extracted and determined the amount of polysaccharides and proteins from representative bacterial biofilms. The spatial distribution of sugars and proteins were then investigated in the biofilm matrix using confocal laser scanning microscopy (CLSM). Thereafter, the extracted matrix components were subjected to sophisticated analysis incorporating Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, one-dimensional gel-based electrophoresis (SDS-PAGE), high performance liquid chromatography (HPLC), and MALDI MS/MS analysis. Besides, the quantification of its total proteins, total sugars, uronates, total acetyl content was also done. Results suggest sugars are not the only/major constituent of its biofilms. The proteins were harvested and subjected to SDS-PAGE which revealed various common and unique protein bands. The common band was excised and analyzed by HPLC. MALDI MS/MS results of this common protein band indicated the presence of different proteins within the biofilm. The 55 different proteins were identified including both cytosolic and membrane proteins. About 22 proteins were related to protein synthesis and processing while 15 proteins were identified related to virulence. Similarly, proteins related to energy and metabolism were 8 and those related to capsule and cell wall synthesis were 4. These results will improve our understanding of Klebsiella biofilm composition and will further help us design better strategies for controlling its biofilm such as techniques focused on weakening/targeting certain portions of the slime which is the most common building block of the biofilm matrix.

Review - Bacteria and their extracellular polymeric substances causing biofouling on seawater reverse osmosis desalination membranes

Biofouling in seawater reverse osmosis (SWRO) membranes is a critical issue faced by the desalination industry worldwide. The major cause of biofouling is the irreversible attachment of recalcitrant biofilms formed by bacteria and their extracellular polymeric substances (EPS) on membrane surfaces. Transparent exopolymer particles (TEP) and protobiofilms are recently identified as important precursors of membrane fouling. Despite considerable amount of research on SWRO biofouling, the control of biofouling still remains a challenge. While adoption of better pretreatment methods may help in preventing membrane biofouling in new desalination setups, it is also crucial to effectively disperse old, recalcitrant biofilms and prolong membrane life in operational plants. Most current practices employ the use of broad spectrum biocides and chemicals that target bacterial cells to disperse mature biofilms, which are evidently inefficient. EPS, being known as the strongest structural framework of biofilms, it is essential to breakdown and disintegrate the EPS components for effective biofilm removal. To achieve this, it is necessary to understand the chemical composition and key elements that constitute the EPS of major biofouling bacterial groups in multi-species, mature biofilms. However, significant gaps in understanding the complexity of EPS are evident by the failure to achieve effective prevention and mitigation of fouling in most cases. Some of the reasons may be difficulty in sampling membranes from fully operational full-scale plants, poor understanding of microbial communities and their ecological shifts under dynamic operational conditions within the desalination process, selection of inappropriate model species for laboratory-scale biofouling studies, and the laborious process of extraction and purification of EPS. This article reviews the novel findings on key aspects of SWRO membrane fouling and control measures with particular emphasis on the key sugars in EPS. As a novel strategy to alleviate biofouling, future control methods may be aimed towards specifically disintegrating and breaking down these key sugars rather than using broad spectrum chemicals such as biocides that are currently used in the industry.

Isolation, Characterization, and Pharmaceutical Applications of an Exopolysaccharide from Aerococcus Uriaeequi

Many marine bacteria secrete exopolysaccharides (EPSs), which are made up of a substantial component of the macro-molecules surrounding cells. Recently, the wide demand for EPSs for food, cosmetics, pharmaceutical and other applications has led to great interest in them. In this study, an EPS produced by marine bacteria Aerococcus uriaeequi HZ strains (EPS-A) was isolated and purified to examine its structure and biological function. The molecular weight of EPS-A analyzed by high-performance liquid gel filtration chromatography (HPGFC) is found to have a number average of 2.22 × 10⁵ and weight average of 2.84 × 10⁵, respectively. High-performance liquid chromatography (HPLC) and Fourier-transform–infrared (FT–IR) analysis indicate that EPS-A was a polysaccharide composed of glucose and a little mannose. In addition, the flocculating rate of sewage of EPS-A was 79.90%. The hygroscopicity studies showed that hygroscopicity of EPS-A was higher than chitosan but lower than that of sodium hyaluronate. The moisture retention of EPS-A showed similar retention activity to both chitosan and sodium hyaluronate. EPS-A also can scavenge free radicals including both OH• free radical and O₂•⁻ free radical and the activity to O₂•⁻ free radical is similar to vitamin C. Safety assessment on mice indicated that the EPS-A is safe for external use and oral administration. EPS-A has great potential for applications in medicine due to its characteristics mentioned above.

Self-Assembled Exopolysaccharide Nanoparticles for Bioremediation and Green Synthesis of Noble Metal Nanoparticles

Continuing efforts have been made to explore novel exopolysaccharides (EPSs) for valuable applications. In this research, we report for the first time that a novel non-glucan EPS named EPS-605 can self-assemble to form spherical nanosize particles of ∼88 nm in diameter, expanding both the range of EPS type and structural type that EPSs self-assemble into. Characterization of EPS-605 shows that it is composed of mannose, glucose, and galactose with several modifications including acylation, phosphorylation, sulfation, and carboxylation, and a highly negative charge. EPS-605 showed a record biosorption capability for Pb²⁺, Cu²⁺, Cd²⁺, and methylene blue as compared to that of other reported EPSs, biosorbents, and nanosorbents. The adsorption ability of EPS-605 is affected by pH, temperature, the initial adsorbate concentration, the contact time, and the presence of background electrolytes. The mechanism of EPS-605 adsorbing heavy metals seems to be different to that for dyes. Moreover, EPS-605 can serve as the reductant in the synthesis of Au nanoparticles (AuNPs) and AgNPs enabling good monodispersity within the shortest time (of 30 min) compared to that from other EPSs and without any extra pretreatment. Our research advances the development of novel EPSs and provides a new, eco-friendly, and renewable platform for both the bioremediation and green synthesis of nanomaterials.

Biosorption of lead, copper and cadmium using the extracellular polysaccharides (EPS) of Bacillus sp., from solar salterns

Extracellular Polysaccharides (EPS) from both prokaryotes and eukaryotes have a great deal of research interest as they protect the producer from different stresses including antibiotics, ionic stress, desiccation and assist in bio-film formation, pathogenesis, adhesion, etc. In this study haloalkaliphilic Bacillus sp., known to cope with osmophilic stress, was selected and screened for EPS production. The EPS were isolated, partially purified and chemical characteristics were documented using liquid FT-IR followed by assessment of heavy metal biosorption (lead, copper and cadmium) using Atomic Absorption Spectroscopy (AAS). The EPS extracted from three isolates B. licheniformis NSPA5, B. cereus NSPA8 and B. subtilis NSPA13 showed maximum biosorption of Lead followed by Copper and Cadmium. Of the tested isolates, the EPS from isolate B. cereus NSPA8 showed maximum (90 %) biosorption of the lead.

Effects of Lipopolysaccharide Core Sugar Deficiency on Colanic Acid Biosynthesis in Escherichia coli

When 10 Escherichia coli mutant strains with defects in lipopolysaccharide (LPS) core biosynthesis were grown on agar medium at 30°C, four of them, the ΔwaaF, ΔwaaG, ΔwaaP, and ΔwaaB strains, formed mucoid colonies, while the other six, the ΔwaaU, ΔwaaR, ΔwaaO, ΔwaaC, ΔwaaQ, and ΔwaaY strains, did not. Using light microscopy with tannin mordant staining, the presence of exopolysaccharide around the cells of the mutants that formed mucoid colonies could be discerned. The ΔwaaF mutant produced the largest amounts of exopolysaccharide, regardless of whether it was grown on agar or in liquid medium. The exopolysaccharide was isolated from the liquid growth medium of ΔwaaF cells, hydrolyzed, and analyzed by high-performance liquid chromatography with an ion-exchange column, and the results indicated that the exopolysaccharide was consistent with colanic acid. When the key genes related to the biosynthesis of colanic acid, i.e., wza, wzb, wzc, and wcaA, were deleted in the ΔwaaF background, the exopolysaccharide could not be produced any more, further confirming that it was colanic acid. Colanic acid could not be produced in strains in which rcsA, rcsB, rcsD, or rcsF was deleted in the ΔwaaF background, but a reduced level of colanic acid production was detected when the rcsC gene was deleted, suggesting that a change of lipopolysaccharide structure in ΔwaaF cells might be sensed by the RcsCDB phosphorelay system, leading to the production of colanic acid. The results demonstrate that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural deficiency of lipopolysaccharide.

IMPORTANCE

Lipopolysaccharide and colanic acid are important forms of exopolysaccharide for Escherichia coli cells. Their metabolism and biological significance have been investigated, but their interrelation with the cell stress response process is not understood. This study demonstrates, for the first time, that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural change of lipopolysaccharide, suggesting that bacterial cells can monitor the outer membrane integrity, which is essential for cell survival and damage repair.

Emerging tools to study proteoglycan function during skeletal development

In the past 20years, appreciation for the varied roles of proteoglycans (PGs), which are specific types of sugar-coated proteins, has increased dramatically. PGs in the extracellular matrix were long known to impart structural functions to many tissues, especially articular cartilage, which cushions bones and allows mobility at skeletal joints. Indeed, osteoarthritis is a debilitating disease associated with loss of PGs in articular cartilage. Today, however, PGs have a demonstrated role in cell biological processes, such as growth factor signalling, prompting new perspectives on the etiology of PG-associated diseases. Here, we review diseases associated with defects in PG synthesis and sulfation, also highlighting current understanding of the underlying genetics, biochemistry, and cell biology. Since most research has analyzed a class of PGs called heparan sulfate PGs, more attention is paid here to studies of chondroitin sulfate PGs (CSPGs), which are abundant in cartilage. Interestingly, CSPG synthesis is tightly linked to the cell biological processes of secretion and lysosomal degradation, suggesting that these systems may be linked genetically. Animal models of loss of CSPG function have revealed CSPGs to impact skeletal development. Specifically, our work from a mutagenesis screen in zebrafish led to the hypothesis that cartilage PGs normally delay the timing of endochondral ossification. Finally, we outline emerging approaches in zebrafish that may revolutionize the study of cartilage PG function, including transgenic methods and novel imaging techniques. Our recent work with X-ray fluorescent imaging, for example, enables direct correlation of PG function with PG-dependent biological processes.

Metal-Induced Production of a Novel Bioadsorbent Exopolysaccharide in a Native Rhodotorula mucilaginosa from the Mexican Northeastern Region

There is a current need to develop low-cost strategies to degrade and eliminate industrially used colorants discharged into the environment. Colorants discharged into natural water streams pose various threats, including: toxicity, degradation of aesthetics and inhibiting sunlight penetration into aquatic ecosystems. Dyes and colorants usually have complex aromatic molecular structures, which make them very stable and difficult to degrade and eliminate by conventional water treatment systems. The results in this work demonstrated that heavy metal-resistant Rhodotorula mucilaginosa strain UANL-001L isolated from the northeast region of Mexico produce an exopolysaccharide (EPS), during growth, which has colorant adsorption potential. The EPS produced was purified by precipitation and dialysis and was then physically and chemically characterized by Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, and chemical elemental analysis. Here, the ability of the purified EPS produced to adsorb methylene blue (MB), which served as a model colorant, is studied. MB adsorption by the EPS is found to follow Langmuir Adsorption Isotherm kinetics at 25°C. Further, by calculating the Langmuir constant the adsorption capabilities of the EPS produced by the Rhodotorula mucilaginosa strain UANL-001L is compared to that of other adsorbents, both, microbially produced and from agroindustrial waste. The total adsorption capacity of the EPS, from the Rhodotorula mucilaginosa strain UANL-001L, was found to be two-fold greater than the best bioadsorbents reported in the literature. Finally, apart from determining which heavy metals stimulated EPS production in the strain, the optimal conditions of pH, heavy metal concentration, and rate of agitation of the growing culture for EPS production, was determined. The EPS reported here has the potential of aiding in the efficient removal of colorants both in water treatment plants and in situ in natural water streams.

The Control of Microbiological Problems∗∗Some excerpts taken from Bajpai P (2012). Biotechnology for Pulp and Paper Processing with kind permission from Springer Science1Business Media

Methods used to control microbiological problems are discussed. Good housekeeping and regular inspection of all areas, effective boilouts, and regularly scheduled washups reduce slime development. Conventional slime control methods generally employ combinations of biocides. Alternative control measures use enzymes, biodispersants, bacteriophages, competing organisms, and biological complex formers. Using enzymes for slime control is expected to bring important benefits to the pulp and paper industry. Enzymes represent a clean and sustainable technology: they are nontoxic, readily biodegradable, and are produced using renewable raw materials. Use of enzymes in combination with biodispersants appears to be a promising method for slime control.

Plant-derived compounds as natural antimicrobials to control paper mill biofilms

Biofilms can cause severe problems in industrial paper mills, particularly of economic and technological types (clogging of filters, sheet breaks or holes in the paper, machine breakdowns, etc.). We present here some promising results on the use of essential oil compounds to control these biofilms. Biofilms were grown on stainless-steel coupons with a microbial white water consortium sampled from an industrial paper mill. Five essential oil compounds were screened initially in the laboratory in terms of their antimicrobial activity against planktonic cells and biofilms. The three most active compounds were selected and then tested in different combinations. The combination finally selected was tested at the pilot scale to confirm its efficiency under realistic conditions. All the compounds tested were as active against biofilms as they were against planktonic cells. The most active compounds were thymol, carvacrol, and eugenol, and the most efficient combination was thymol–carvacrol. At a pilot scale, with six injections a day, 10 mM carvacrol alone prevented biocontamination for at least 10 days, and a 1 mM thymol–carvacrol combination enabled a 67 % reduction in biofilm dry matter after 11 days. The use of green antimicrobials could constitute a very promising alternative or supplement to the treatments currently applied to limit biofilm formation in the environment of paper mill machines.

Mini-review: microbial problems in paper production

Paper mills are open systems, which provide favorable conditions for microbial growth. Microbial contamination can cause substantial economic losses, including the deterioration of raw materials, interference with production processes by breakdowns and lowering product quality, and eventually, problems in wastewater treatment. Damage is caused by acidification, attack on raw materials, the formation of odorous products, discoloration of pigments, and the formation of methane and hydrogen, thereby producing potentially explosive conditions. Population analyses have revealed that a wide variety of microorganisms are involved, but there appear to be no typical strains associated with paper mills. Current trends in process engineering, such as chlorine-free bleaching, processing at neutral pH, closed cycles, and the use of recycled paper also favor microbial growth and biofilm (slime) formation. A fundamental problem associated with slimes is the extensive matrix of extracellular polymeric substances, which is composed of a large variety of highly hydrated polysaccharides, proteins, nucleic acids, and lipids. No 'silver bullet' against biofouling can be expected, and effective countermeasures have to be based on holistic approaches.

Development and validation of a colorimetric assay for simultaneous quantification of neutral and uronic sugars

A colorimetric assay based on the conventional anthrone reaction was investigated for specific quantification of uronic acids (UA) in the presence of neutral sugars and/or proteins. Scanning of glucose (Glu) and glucuronic acid (GlA) was performed after the reaction with anthrone and a double absorbance reading was made, at 560 nm and at 620 nm, in order to quantify the UA and neutral sugars separately. The assay was implemented on binary or ternary solutions containing Glu, GlA and bovine serum albumin (BSA) in order to validate its specificity towards sugars and check possible interference with other biochemical components such as proteins. Statistical analysis indicated that this assay provided correct quantification of uronic sugars from 50 to 400 mg/l and of neutral sugars from 20 to 80 mg/l, in the presence of proteins with concentrations reaching 600 mg/l. The proposed protocol can be of great interest for simultaneous determination of uronic and neutral sugars in complex biological samples. In particular, it can be used to correctly quantify the Extracellular Polymeric Substances (EPS) isolated from the biological matrix of many bacterial aggregates, even in the presence of EPS extractant such as EDTA.

Removal of microbial multi-species biofilms from the paper industry by enzymatic treatments

This study aimed to characterize biofilms from the paper industry and evaluate the effectiveness of enzymatic treatments in reducing them. The extracellular polymeric substances (EPS) extracted from six industrial biofilms were studied. EPS were mainly proteins, the protein to polysaccharide ratio ranging from 1.3 to 8.6 depending on where the sampling point was situated in the paper making process. Eight hydrolytic enzymes were screened on a 24-h multi-species biofilm. The enzymes were tested at various concentrations and contact durations. Glycosidases and lipases were inefficient or only slightly efficient for biofilm reduction, while proteases were more efficient: after treatment for 24 h with pepsin, Alcalase® or Savinase®, the removal exceeded 80%. Savinase® appeared to be the most adequate for industrial conditions and was tested on an industrial biofilm sample. This enzyme led to a significant release of proteins from the EPS matrix, indicating its potential efficiency on an industrial scale.

Bacteria attachment to surfaces--AFM force spectroscopy and physicochemical analyses

Understanding bacterial adhesion to surfaces requires knowledge of the forces that govern bacterial-surface interactions. Biofilm formation on stainless steel 316 (SS316) by three bacterial species was investigated by examining surface force interaction between the cells and metal surface using atomic force microscopy (AFM). Bacterial-metal adhesion force was quantified at different surface delay time from 0 to 60s using AFM tip coated with three different bacterial species: Gram-negative Massilia timonae and Pseudomonas aeruginosa, and Gram-positive Bacillus subtilis. The results revealed that bacterial adhesion forces on SS316 surface by Gram-negative bacteria is higher (8.53±1.40 nN and 7.88±0.94 nN) when compared to Gram-positive bacteria (1.44±0.21 nN). Physicochemical analysis on bacterial surface properties also revealed that M. timonae and P. aeruginosa showed higher hydrophobicity and surface charges than B. subtilis along with the capability of producing extracellular polymeric substances (EPS). The higher hydrophobicity, surface charges, and greater propensity to form EPS by M. timonae and P. aeruginosa led to high adhesive force on the metal surface.

Biofilm formation by Paenibacillus polymyxa strains differing in the production and rheological properties of their exopolysaccharides

We evaluated the ability of several strains of the rhizobacterium Paenibacillus polymyxa, differing in the yield and rheological properties of their exopolysaccharides, to form biofilms on abiotic surfaces. Of these strains, P. polymyxa 1465, giving the highest yield of extracellular polysaccharides and the highest kinematic viscosity of the culture liquid and of aqueous polysaccharide solutions, proved to be the most active in forming biofilms on hydrophobic and hydrophilic surfaces. Enzyme-linked immunosorbent assay with rabbit polyclonal antibodies developed to isolated exopolysaccharides of P. polymyxa 1465 and 92 was used to detect P. polymyxa's polysaccharidic determinants in the composition of the biofilm materials.

Electrochemical and microbiological characterization of paper mill biofilms

Biofilm samples collected from inside and outside the press and former sections of paper machines in a Northwestern Ontario paper mill for a period of 2 years were characterized microbiologically and electrochemically. Bacterial community profiling was done using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and selected bacterial isolates were identified using 16S rDNA analysis. The bacterial community showed the presence of Proteobacteria, Firmicutes, and Actinobacteria. Sphingomonas sp. was found to be the most common bacterial species, which showed the highest production of extracellular polymeric substances. Bacteria isolated from biofilms showed better adhesion properties than those from water samples. Cyclic voltammetry and electrochemical impedance spectroscopy studies showed that bacteria isolated from biofilms and feed water collected from inside the machine were more easily oxidized than those from outside, suggesting the need for a more rigorous biofilm abatement strategy for inside paper machines.

Characterization of extracellular polymeric substances from acidophilic microbial biofilms

We examined the chemical composition of extracellular polymeric substances (EPS) extracted from two natural microbial pellicle biofilms growing on acid mine drainage (AMD) solutions. The EPS obtained from a mid-developmental-stage biofilm (DS1) and a mature biofilm (DS2) were qualitatively and quantitatively compared. More than twice as much EPS was derived from DS2 as from DS1 (approximately 340 and 150 mg of EPS per g [dry weight] for DS2 and DS1, respectively). Composition analyses indicated the presence of carbohydrates, metals, proteins, and minor quantities of DNA and lipids, although the relative concentrations of these components were different for the two EPS samples. EPS from DS2 contained higher concentrations of metals and carbohydrates than EPS from DS1. Fe was the most abundant metal in both samples, accounting for about 73% of the total metal content, followed by Al, Mg, and Zn. The relative concentration profile for these metals resembled that for the AMD solution in which the biofilms grew, except for Si, Mn, and Co. Glycosyl composition analysis indicated that both EPS samples were composed primarily of galactose, glucose, heptose, rhamnose, and mannose, while the relative amounts of individual sugars were substantially different in DS1 and DS2. Additionally, carbohydrate linkage analysis revealed multiply linked heptose, galactose, glucose, mannose, and rhamnose, with some of the glucose in a 4-linked form. These results indicate that the biochemical composition of the EPS from these acidic biofilms is dependent on maturity and is controlled by the microbial communities, as well as the local geochemical environment.

Early succession of bacterial biofilms in paper machines

Formation of biofilms causes severe problems in paper machines, and hence financial costs. It would be preferable to prevent attachment of the primary-colonizing bacteria than to control the growth of secondary communities, which are sheltered by exopolysaccharide slime layers. We have therefore investigated the early succession of paper-machine biofilms by incubating stainless-steel test coupons in the process water-flow lines in two paper machines operating in slightly alkaline conditions in temperatures (45 and 49 degrees C) supporting thermophilic microbes. Microbial succession was profiled using length heterogeneity analysis of PCR-amplified 16S rRNA genes (LH-PCR) and linking the sequence data of the created 16S rRNA gene libraries to the dominant LH-PCR peaks. Although the bacterial fingerprints obtained from the attached surface communities varied slightly in different samples, the biomarker signals of the dominating primary-colonizing bacterial groups remained high over time in each paper machine. Most of the 16S rRNA gene copies in the early biofilms were assigned to the genera Rhodobacter, Tepidimonas, and Cloacibacterium. The dominance of these sequence types decreased in the developing biofilms. Finally, as phylogenetically identical primary-colonizers were detected in the two different paper mills, the machines evidently had similar environmental conditions for bacterial growth and potentially a common source of contamination.

Bismuth dimercaptopropanol (BisBAL) inhibits the expression of extracellular polysaccharides and proteins by Brevundimonas diminuta: implications for membrane microfiltration

A 2:1 molar ratio preparation of bismuth with a lipophilic dithiol (3-dimercapto-1-propanol, BAL) significantly reduced extracellular polymeric substances (EPS) expression by Brevundimonas diminuta in suspended cultures at levels just below the minimum inhibitory concentration (MIC). Total polysaccharides and proteins secreted by B. diminuta decreased by approximately 95% over a 5-day period when exposed to the bismuth-BAL chelate (BisBAL) at near MIC (12 microM). Fourier-transform infrared spectroscopy (FTIR) suggested that a possible mechanism of biofilm disruption by BisBAL is the inhibition of carbohydrate O-acetylation. FTIR also revealed extensive homology between EPS samples with and without BisBAL treatment, with proteins, polysaccharides, and peptides varying predominantly only in the amount expressed. EPS secretion decreased following BisBAL treatment as verified by atomic force microscopy and scanning electron microscopy. Without BisBAL treatment, a slime-like EPS matrix secreted by B. diminuta resulted in biofouling and inefficient hydrodynamic backwashing of microfiltration membranes.

An alternative infrared spectroscopy assay for the quantification of polysaccharides in bacterial samples

The ability of bacteria to produce extracellular polysaccharides has been regarded as an indication of biofilm-forming capacity. Therefore, the determination of the sugar content in bacterial samples becomes a significant parameter. The colorimetric methods currently used are rather sensitive to the nature of the sugars and therefore require knowledge of the sugar types present in the samples. Unfortunately, the types of sugars present in bacteria are generally unknown and often composed of a complex mixture. In this article, we propose an alternative method based on Fourier transform infrared (FTIR) spectroscopy for the estimation of the total sugar content in bacterial samples. The method is based on a systematic treatment of FTIR spectra obtained from dried bacteria samples. It is assumed that the total sugar amount can be estimated from the area of characteristic bands between 970 and 1182 cm(-1). In parallel, the amide II band (1560-1530 cm(-1)) associated with proteins, or the C-H stretching region (2820-3020 cm(-1)) associated with the biomass, can be used for normalization purposes. Therefore, the ratio of the band area in the sugar window over that of the amide II or C-H stretching can be used to report the sugar content in bacterial samples. This method has been validated on model bacterial mixtures containing sugars, proteins, and DNA. Results with real bacterial samples are also provided and show conclusively that increased sugar contents in biofilms can be identified. The proposed FTIR approach requires minimal sample preparation and a single acquisition, is rapid, and may be applied to any kind of bacterial growth.

Characterisation of a 1,4-beta-fucoside hydrolase degrading colanic acid

A novel colanic acid-degrading enzyme was isolated from a mixed culture filtrate obtained by enrichment culturing of a compost sample using colanic acid as carbon source. The enzyme was partially purified resulting in a 17-fold increase in specific activity. Further purification by Native PAGE revealed that the enzyme is part of a high-molecular weight multi protein complex of at least six individual proteins. The enzyme showed a temperature optimum at 50 degrees C while after 5h at 50 degrees C and pH7 still 70% of the total activity was left. The pH optimum was found to be pH7. Analysis of the degradation products showed that the enzyme is a novel 1,4-beta-fucoside hydrolase that liberates repeating units of colanic acid with varying degrees of acetylation. Km and Vmax of the enzyme were determined against the native substrate as well as its de-O-acetylated and depyruvated forms. Compared to the native substrate the affinity of the enzyme for the modified substrates was much lower. However, for the de-O-acetylated sample a dramatic increase in catalytic efficiency was observed. The native form of the substrate showed substrate inhibition at high concentrations, probably due to the formation of nonproductive substrate complexes. Removal of the acetyl groups probably prevents this effect resulting in a higher catalytic efficiency.