Estimations of uronic acids as quantitative measures of extracellular and cell wall polysaccharide polymers from environmental samples

Reevaluation and novel insights into amino sugar and neutral sugar necromass biomarkers in archaea, bacteria, fungi, and plants

Soil microbial necromass is an important contributor to soil organic matter (>50%) and it is largely composed of microbial residues. In soils, fragmented cell wall residues are mostly found in their polysaccharide forms of fungal chitin and bacterial peptidoglycan. Microbial necromass biomarkers, particularly amino sugars (AS) such as glucosamine (GlcN) and muramic acid (MurA) have been used to trace fungal and bacterial residues in soils, and to distinguish carbon (C) found in microbial residues from non-microbial organic C. Neutral sugars (NS), particularly the hexose/pentose ratio, have also been proposed as tracers of plant polysaccharides in soils. In our study, we extended the range of biomarkers to include AS and NS compounds in the biomass of 120 species belonging to archaea, bacteria, fungi, or plants. GlcN was the most common AS found in all taxa, contributing 42-91% to total AS content, while glucose was the most common NS found, contributing 56-79% to total NS. We identified talosaminuronic acid, found in archaeal pseudopeptidoglycan, as a new potential biomarker specific for Euryarchaeota. We compared the variability of these compounds between the different taxonomic groups using multivariate approaches, such as non-metric multidimensional scaling (NMDS) and partial least squares discriminant analysis (PLS-DA) and statistically evaluated their biomarker potential via indicator species analysis. Both NMDS and PLS-DA showcased the variability in the AS and NS contents between the different taxonomic groups, highlighting their potential as necromass residue biomarkers and allowing their extension from separating bacterial and fungal necromass to separating microbes from plants. Finally, we estimated new conversion factors where fungal GlcN is converted to fungal C by multiplying by 10 and MurA is converted to bacterial C by multiplying by 54. Conversion factors for talosaminuronic acid and galactosamine are also proposed to allow estimation of archaeal or all-microbial necromass residue C, respectively.

Production of pectic-oligosaccharides from pomelo peel pectin by oxidative degradation with hydrogen peroxide

Oxidative depolymerization of alkali- and acid-extracted pomelo pectins was performed using 1% hydrogen peroxide (H₂O₂) with a microwave power of 550 W for 10 min. Pectic-oligosaccharides (POS) produced from the acid-extracted methyl-esterified pectin contained higher amounts of DP1 and DP2 than that from the nearly ester-free alkali-extracted pectin, and the loss of these small-size products during recovery resulted in a lower POS yield (25.0%) compared to the alkali-extracted pectin (57.7%). Degradation of the alkali-extracted pectin with 3 and 5% H₂O₂ led to a decrease in precipitable POS yield. The relative amount of large-sized POS decreased as the H₂O₂ concentration increased. An increase in the microwave power to 1100 W had no significant effect on overall yield, but the average size shifted to be lower. The results of sugar composition and identification of the degraded products with ESI-MS confirmed the existence of several POS species with different sizes and structures.

Characterization of exopolymeric substances from selected Rhodopseudomonas palustris strains and their ability to adsorb sodium ions

Removal of Na(+) by binding with exopolymeric substances (EPS) from Rhodopseudomonas palustris TN114 and PP803 was investigated. The moderate negative correlation pairs (rp) between remaining Alcian blue and amount of Na(+) adsorbed on EPS from strains TN114 and PP803 were -0.652 and -0.609. Both strains showed positive relationships between the amounts of EPS produced and bacterial growth. EPS from strain PP803 had a higher efficiency in removing Na(+) than the EPS from strain TN114 based on their EC50 values (1.79 and 1.49 mg/mL for TN114 and PP803, respectively). The principal component from EPS of strain PP803 which was responsible for salt removal was purified and it was identified as a polysaccharide (≈18 kDa) mainly composed of galacturonic acid. Overall results suggested that EPS is a key factor that our strains used to bind Na(+) allowing their survival in high NaCl concentrations.

By-passing acidification limitations during the biofiltration of high formaldehyde loads via the application of ozone pulses

A formaldehyde airstream was treated in a biofilter for an extended period of time. During the first 133 days, the reactor was operated without ozone, whereas over the following 82 days ozone was intermittently implemented. The maximum stable elimination capacity obtained without ozone was around 57 g m(-3) h(-1). A greater load could not be treated under these conditions, and no significant formaldehyde removal was maintained for inlet loads greater than 65 g m(-3) h(-1); the activity of microorganisms was then inhibited by the presence of acidic byproducts, and the media acidified (pH<4). The implementation of ozone pulses allowed a stable elimination capacity to be obtained, even at greater loads (74 g m(-3) h(-1)). The effect of ozone on the extra cellular polymeric substances detachment from the biofilm could not be confirmed due to the too low biofilter biomass content. Thus, the results suggest that ozone acted as an in situ pH regulator, preventing acidic byproducts accumulation, and allowing the treatment of high loads of formaldehyde.

Isolation of halotolerant, thermotolerant, facultative polymer-producing bacteria and characterization of the exopolymer

Over 200 bacterial strains were selected for anaerobic growth at 50 degrees C and extracellular polysaccharide production in a sucrose-mineral salts medium with NaNO(3) and up to 10% NaCl. The predominant cell type was an encapsulated gram-positive, motile, facultative sporeforming rod similar to Bacillus species. Strain SP018 grew and produced the polysaccharide on a variety of substrates at salinities up to 12% NaCl. Good polymer production only occurred anaerobically and was optimal between 4 and 10% NaCl. The ethanol-precipitated SP018 polymer was a charged heteropolysaccharide that contained glucose, mannose, arabinose, ribose, and low levels of allose and glucosamine. The SP018 polymer showed pseudoplastic behavior, was resistant to shearing, and had a higher viscosity at dilute concentrations and at elevated temperatures than xanthan gum. High-ionic-strength solutions reversibly decreased the viscosity of SP018 polymer solutions. The bacterium and the associated polymer have many properties that make them potentially useful for in situ microbially enhanced oil recovery processes.

Identification of biofoulant of membrane bioreactors in soluble microbial products

To reveal primary biofoulant in soluble microbial products (SMP) and/or soluble extracellular polymeric substances (EPS), after removal of sludge particles, activated sludge samples were subjected to microfiltration tests in a submerged MBR. Filtration resistance directly correlates with the saccharide concentration. Saccharides in wastewater from several sources contained uronic acids, which increased the filtration resistance. When the microfiltration test liquids contained saccharides over 80mg l(-1), a gelatinous mass remained on the membrane surface after filtration and contained concentrations of saccharides and uronic acids 50 times higher than the original test liquid while only trace amounts of these substances were contained in the filtrate. The gelatinous mass contained high molecular weight substances of 10(6)-10(8)Da, suggesting the presence of polysaccharides. However, molecules of this size were calculated to be much smaller than the pore size of the membrane. Ethylenediaminetetraacetic acid decreased filtration resistance, suggesting that polysaccharides containing uronic acid units could undergo intermolecular or intramolecular ionic cross-linking by polyvalent cations and form the gel, thus clogging the membrane pores as an actual biofoulant.

Microbial signature lipid profiling and exopolysaccharides: Experiences initiated with Professor David C White and transported to Tasmania, Australia

Developments and applications with signature lipid and exopolysaccharide (EPS) methodologies covering a thirty year period in the DC White laboratories at Florida State University and the University of Tennessee at Knoxville are illustrated. These powerful techniques were used to gain new insight into microbial communities, not obtainable by classical approaches. Selected case examples are highlighted and include: use of a specific dimethyl disulphide (DMDS) derivitization procedure with monounsaturated fatty acids (MUFA) to precisely determine double bond position and geometry; application of the DMDS procedure in taxonomic and environmental studies including the degradation of pollutant halogenated hydrocarbons in groundwater and subsurface aquifers; exploiting the ubiquitous nature of uronic acids in microbial EPS to quantify these exopolymers in complex environmental samples; development of rapid and non-destructive approaches including FT-IR to follow biofilm formation in a unique manner not possible with other approaches. The foundations laid in the DC White laboratories have seen a wide suite of applications in modern microbial ecology and associated fields. The training of young scientists by DC White will also ensure that his unique approach and quest for new and or novel methodologies for use in environmental microbiology will continue.

Microbial biofilm formation in DUWS and their control using disinfectants

OBJECTIVES

Due to the presence of extended narrow bore tubing and long periods of stagnation, dental unit water systems (DUWs) can be prone to relatively high levels of microbial contamination, including the formation of biofilm and the presence of opportunistic pathogens, irrespective of the source and quality of the inflowing water. Whilst the European Union (EU) has yet to set a definitive microbiological guideline, the American Dental Association (ADA) has set a maximum of <200 colony forming units (cfu)/ml for DUWs water in the USA. The objective of this review is to discuss why microbial contamination and biofilms are so prevalent in DUWs, as well as the role of disinfectants and their potential for achieving microbial water quality levels recommended by the ADA.

STUDY SELECTION

The review outlines the principal factors responsible for biofilm formation in DUWs and a number of mechanisms used for microbial control.

SOURCES

The source material contained in this review is taken from the peer-reviewed literature.

DATA

A variety of disinfectants are available for use, but controlled laboratory and clinical studies have shown that they can vary markedly in their efficacy and suitability for use. Some products have been shown to successfully remove biofilm and consistently reduce the microbial load of out-flowing water to <200 cfu/ml.

CONCLUSIONS

The effective delivery of approved disinfectants can control the level of microorganisms in DUWs at acceptable levels.

Quantitative analysis of biofilm EPS uronic acid content

The uronic acids assay was evaluated for its ability to measure the amount of uronic acids contained within a biofilm exopolysaccharide matrix. Cytophaga lytica, a marine bacterium isolated from a naturally occurring biofilm, was used to form single-species biofilms for the method assessment. The assay was found to be simple, reproducible, and sensitive to 1 microg levels, suggesting its potential for application as a screening technique for compounds that inhibit the production of microbial biofilm exopolysaccharide containing uronic acids.

Isolation and characterization of exopolysaccharide produced byVibrio harveyistrain VB23

AIMS

The aim of the study was to isolate and characterize exopolysaccharide (EPS) produced by Vibrio harveyi strain VB23.

METHODS AND RESULTS

Growth and EPS production by V. harveyi strain VB23, was studied in mineral salts medium supplemented with NaCl (1.5%) and glucose (0.2%). The rate of EPS production in batch cultures was highest during the late log phase of growth when compared with stationary growth phase. The exopolymer was recovered from the culture supernatant by using a cold ethanol precipitation-dialysis procedure. Chemical analyses of EPS revealed that it is primarily composed of neutral sugars, uronic acids, proteins and sulfates. The purified EPS revealed prominent functional reactive groups, such as hydroxyl, carboxylic and amides, which correspond to a typical heteropolymeric polysaccharide and the EPS, also possessed good emulsification activity. The gas chromatographic analysis of an alditol acetate-derivatized sample of EPS revealed that it is composed primarily of galactose and glucose. Minor components found were rhamnose, fucose, ribose, arabinose, xylose and mannose.

CONCLUSIONS

The EPS produced by V. harveyi strain VB23 is a heteropolysaccharide possessing good emulsification activity. EPS was readily isolated from culture supernatants, which suggests that the EPS was a slime-like EPS.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report of EPS characterization in luminous V. harveyi bacteria, which describes the isolation and characterization of an EPS expressed by V. harveyi. The results of the study contributes significantly towards an understanding of the chemical composition and applications of the EPS in environmental biotechnology and bioremediation.

The characterization of algal and microbial mucilages and their aggregates in aquatic ecosystems

The mucilage 'phenomenon' of marine waters, a sporadic but massive accumulation of gelatinous material at and below the water surface, can create serious environmental and economic problems. To address these problems, we must understand better the causes of the phenomenon, its modulation by environmental factors and its adverse effects on ecosystems. In the context of an improved understanding, this brief review describes the means to characterize mucilage types and mucilage aggregates in their native condition, or as close to native as state-of-the-art technology will permit. Biological, chemical and physical factors interact to determine mucilage 'speciation' and thus the specific properties of mucilaginous materials. These factors and their interactions are described briefly in relation to the molecular biology of mucilage synthesis, the formation of submicroscopic 'particles' of mucilage and the morphology of mucilage aggregates. To facilitate current attempts to relate mucilage fine structure to the macroscale morphology of large aggregates (e.g., as found in the Adriatic Sea), attention will be focused on the 'fibril', a ribbon-like colloid rich in polysaccharide molecules. Such colloids (submicrometre particles) present many morphotypes which are identifiable by transmission electron microscopy; several fibril types appear as basic structural units in many kinds of mucilage aggregates in aquatic ecosystems. Attention will also be focused on (1) the problems of coping with analyzing mixtures of highly-hydrated, physically-unstable materials and (2) the detection, assessment and minimization of colloid instability artifacts which have confounded morphological analyses of mucilage aggregates in the past.

Comparison of the adhesion properties of Deleya marina and the exopolysaccharide-defective mutant strain DMR

Deleya marina 219 (ATCC 25374) produces large quantities of an acidic exopolysaccharide and characteristically forms mucoid colonies and large aggregates of cells. The exopolysaccharide of wild-type D. marina cells appears to occur as both film and fibrils in electron micrographs. The organization of exopolymeric material was indicative of structural heterogeneity. A spontaneous rough-colony mutant defective in exopolysaccharide, D. marina DMR, has been isolated. The absence of exopolymer corresponds to a nonmucoid, nonaggregating, adhesion-altered phenotype. In microplate adhesion assays, wild-type cells grown at 19 or 25 degrees C attached to hydrophilic surfaces but not to a hydrophobic surface. In contrast, mutant cells exhibited a significantly reduced level of attachment to hydrophilic surfaces and increased adhesion to a hydrophobic surface.

Determination of saccharides in biological materials by high-performance anion-exchange chromatography with pulsed amperometric detection

High-performance anion-exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD) under alkaline conditions (pH 9-13) separates aminosaccharides, neutral saccharides and glycuronic acids based upon their molecular size, saccharide composition and glycosidic linkages. Carbohydrates were extracted by utilizing 0.5 M H2SO4 (neutral monosaccharides), 0.25 M H2SO4 coupled with enzyme catalysis (glycuronic acids) and 3 M H2SO4 (aminosaccharides). Solid-phase extraction with strong cation and strong anion resins was used to partition the cationic aminosaccharides and anionic glycuronic acids and to deionize acid extracts for neutral saccharides. Separation was conducted on a medium-capacity anion-exchange column (36 mequiv.) utilizing sodium hydroxide (5-200 mM and sodium acetate (0-250 mM) as the mobile phase. The saccharides were detected by oxidation at a gold working electrode with triple-pulsed amperometry. HPAEC-PAD was found superior to high-performance liquid chromatography with refractive index (RI) detection for neutral monosaccharides and aminosaccharides and to low-wavelength UV detection for glycuronic acids in terms of resolution and sensitivity. HPAEC-PAD was not subject to interferences as was the case for low UV detection (210 nm) or RI analyses and was highly selective for mono- and aminosaccharides and glycuronic acids. The use of HPAEC-PAD was applied for the determination of the saccharide composition of organic materials (plant residues, animal wastes and sewage sludge), microbial polymers and soil.

Characterization of exopolymers of aquatic bacteria by pyrolysis-mass spectrometry

Exopolymers from a diverse collection of marine and freshwater bacteria were characterized by pyrolysis-mass spectrometry (Py-MS). Py-MS provides spectra of pyrolysis fragments that are characteristic of the original material. Analysis of the spectra by multivariate statistical techniques (principal component and canonical variate analysis) separated these exopolymers into distinct groups. Py-MS clearly distinguished characteristic fragments, which may be derived from components responsible for functional differences between polymers. The importance of these distinctions and the relevance of pyrolysis information to exopolysaccharide function in aquatic bacteria is discussed.

Fine-structural and chemical analyses on inner and outer sheath of the cyanobacterium Gloeothece sp. PCC 6909

Cells of the unicellular cyanobacterium Gloeothece sp. PCC 6909 are surrounded by an inner (enclosing 1-2 cells) and an outer (enclosing cell groups) sheath. Using conventional Epon-embedding in combination with ruthenium-red staining, the inner and outer sheaths appeared similar and displayed multiple bands of electron-dense subunits. However, embedding in Nanoplast resin to avoid shrinkage led to the detection of two distinct zones (inner and outer zone) each with several distinct layers. The zone delimited by the electron-dense thick inner sheath layer, and the zone enclosed by the thin electron-dense outer sheath layer, are composed of a homogeneous material of little electron-contrast. Whereas the outer zone appears to be of even contrast, the inner zone is characterized by a distinct electron-transparent layer. Element distribution analysis revealed that the electron-transparent layer contained relatively large amounts of sulfur, carbon, and oxygen but only little nitrogen. Inner and outer sheath fractions were isolated by differential mechanical cell breakage and centrifugation. The outer sheath fraction was less hydrated than the inner one. The two fractions differed little in their contents of uronic acids, carbohydrate and protein, although the outer sheath fraction contained less sulfate. A soluble polysaccharide with a chemical composition similar to that of inner and outer sheath fractions was also obtained from the culture supernatant.

Characterization of the Adhesive Holdfast of Marine and Freshwater Caulobacters

Caulobacters are prosthecate (stalked) bacteria that elaborate an attachment organelle called a holdfast at the tip of the cellular stalk. We examined the binding of lectins to the holdfasts of 16 marine Caulobacter strains and 10 freshwater species or strains by using a panel of fluorescein-conjugated lectins and fluorescence microscopy. The holdfasts of all the marine isolates bound to only wheat germ agglutinin (WGA) and other lectins that bind N -acetylglucosamine (GlcNac) residues. The freshwater caulobacters showed more variability in holdfast composition. Some bound only to WGA and comparable lectins as the marine strains did. Others bound additional or other lectins, and some did not bind to the lectins tested. The binding of WGA appeared to involve the regions of the holdfast involved with adhesion; a holdfast bound to WGA was significantly less adhesive to glass. Competition experiments with WGA-binding holdfasts and oligomers of GlcNac demonstrated that trimers of GlcNac (the preferred substrate for WGA binding) were more effective than dimers or monomers in preventing WGA binding to holdfasts, suggesting that stretches of contiguous GlcNac residues occur in the WGA-binding holdfasts. In addition, differences between freshwater and marine holdfasts in the strength of WGA binding were noted. The effect of a number of proteolytic and glycolytic enzymes on holdfast integrity was examined; the proteases had no effect for all caulobacters. None of the glycolytic enzymes had an effect on marine caulobacter holdfasts, but chitinase and lysozyme (both attack oligomers of GlcNac) disrupted the holdfasts of those freshwater caulobacters that bound WGA. Despite some similarity to chitin, holdfasts did not bind Calcofluor and no measurable effects on holdfast production were detectable after cell growth in the presence of diflubenzuron or polyoxin D, inhibitors of chitin synthesis in other systems. Finally, the holdfasts of all caulobacters bound to colloidal gold particles, without regard to the coating used to stabilize the gold particles. This binding was stronger or more specific than WGA binding; treatment with colloidal gold particles prevented WGA binding, but the reverse was not the case.

Structural Analysis of Secreted Root Slime from Maize (Zea mays L.)

Secreted slime isolated from the incubation medium of Zea mays roots maintained axenically contains fucose, arabinose, xylose, galactose, and glucose as the major monosaccharides. The slime preparation contains low levels (3% weight/weight [w/w]) of uronic acids. Methylation analysis reveals an extraordinarily diverse range of glycosyl residues. The fucosyl residues are primarily terminal (60%) and 3-linked (33%) with a relatively small proportion being 2-linked (6%). The methylation data are consistent with, but not proof of, the presence of a range of polymers including arabinogalactan-proteins (AGPs), xyloglucans, arabinoxylans, and glucans in the slime. The specific binding of the beta-glucosyl Yariv reagent, a dye which binds and precipitates AGPs, to the slime preparation and to the outer periclinal epidermal cell wall surface in root sections, is further evidence for the presence of AGPs. Low levels of phenolic acids (approximately 0.17% w/w), in particular trans-ferulic acid, and protein (approximately 6% w/w) were also detected.

Relationship Between Physiological Status and Formation of Extracellular Polysaccharide Glycocalyx in Pseudomonas atlantica

Marine pseudomonads, such as Pseudomonas atlantica , are readily isolated from sediments. These organisms form extracellular polysaccharide polymers (glycocalyx). The factors affecting the composition and amount of glycocalyx in batch culture of these organisms were examined. The formation of glycocalyx was stimulated by the inclusion of galactose as the carbon source and by increased surface area resulting from addition of sand to the medium. The composition of the glycocalyx changed during the growth cycle, with a marked increase in the proportions and absolute amounts of uronic acids as the rate of synthesis increased. In estuarine sediments, the glycocalyx contained a carbon content at least as great as in the microbes themselves. The greatest accumulation of these polymers occurred late in the stationary phase when the physiological status of the cells, as measured by the adenylate energy charge, showed maximal stress. Maximal formation of glycocalyx possibly could be used as an estimate of the nutritional status of these microbes.

Sensitive assay, based on hydroxy fatty acids from lipopolysaccharide lipid A, for Gram-negative bacteria in sediments

Biochemical measures have provided insight into the biomass and community structure of sedimentary microbiota without the requirement of selection by growth or quantitative removal from the sediment grains. This study used the assay of the hydroxy fatty acids released from the lipid A of the lipopolysaccharide in sediments to provide an estimate of the gram-negative bacteria. The method was sensitive to picomolar amounts of hydroxy fatty acids. The recovery of lipopolysaccharide hydroxy fatty acids from organisms added to sediments was quantitative. The lipids were extracted from the sediments with single-phase chloroform-methanol extraction. The lipid-extraction residue was hydrolyzed in 1 N HCl, and the hydroxy fatty acids of the lipopolysaccharide were recovered in chloroform for analysis by gas-liquid chromatography. This method proved to be about fivefold more sensitive than the classical phenol-water or trichloroacetic acid methods when applied to marine sediments. By examination of the patterns of hydroxy fatty acids, it was also possible to help define the community structure of the sedimentary gram-negative bacteria.