INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2010
Stéphanie Boulêtreau
Abstract A 15-week experiment was performed in a riverside laboratory flume (with diverted river water) to check variations of river biofilm structure (biomass, algal and bacterial compositions) and function (community gross primary production GPP and respiration) under constant flow while water quality went through natural temporal variations. One major suspended matter pulse coinciding with one river flood was recorded after 10 weeks of experiment. Epilithic biofilm first exhibited a 10-week typical pattern of biomass accrual reaching 33 g ash-free dry matter (AFDM) m,2 and 487 mg chlorophyll- a m,2 and then, experienced a shift to dominance of loss processes (loss of 60% AFDM and 80% chlorophyll- a) coinciding with the main suspended matter pulse. Algal diversity remained low and constant during the experiment: Fragilaria capucina and Encyonema minutum always contribute over 80% of cell counts. DGGE banding patterns discriminated between two groups that corresponded to samples before and after biomass loss, indicating major changes in the bacterial community composition. GPP/R remained high during the experiment, suggesting that photoautotrophic metabolism prevailed and detachment was not autogenic (i.e., due to algal senescence or driven by heterotrophic processes within the biofilm). Observational results suggested that silt deposition into the biofilm matrix could have triggered biomass loss. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Three-dimensional simulations of biofilm growth in porous media

AICHE JOURNAL, Issue 2 2009
D. A. Graf von der Schulenburg
Abstract Biofilm growth occurs in a variety of random porous media in a range of industrial processes; prediction of its growth and subsequent influence on hydrodynamics is hence desirable. In this study, we present the first numerical 3D pore-scale model of biofilm growth in porous media, based on a lattice Boltzmann simulation platform complemented with an individual-based biofilm model (IbM). We use it to explore the coupled interaction between nutrient mass transport, biofilm growth, and hydrodynamics. Biofilm is shown to be very effective at reducing the permeability of porous media, particularly under nutrient limited conditions. We conclude with a direct comparison of 3D and 2D biofilm growth simulations in porous media and show the necessity of performing the simulations in 3D. © 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]

Berberine inhibits Staphylococcus Epidermidis adhesion and biofilm formation on the surface of titanium alloy

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 11 2009
Xiaoqing Wang
Abstract Biofilm formed by Staphylococcus epidermidis (S. epidermidis) is a common cause of periprosthetic infection. Recently, we have discovered that berberine is bacteriostatic for S. epidermidis. The purpose of the present study was to examine the effect of berberine on S. epidermidis adhesion and biofilm formation on the surface of titanium alloy, which is a popular material for orthopedic joint prostheses. Three strains of S. epidermidis (ATCC 35984, ATCC 12228, and SE 243) were used for in vitro experiment. Direct colony counting showed that berberine significantly inhibited S. epidermidis adhesion on the titanium alloy disk in 2 h at the concentration of 45 µg/mL. When examined with crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy, we found that higher concentrations (>30 µg/mL) of berberine effectively prevented the formation of S. epidermidis biofilm on the surface of the titanium disk in 24 h. These findings suggest that berberine is a potential agent for the treatment of periprosthetic infection. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1487,1492, 2009 [source]

Influences of milk components on biofilm formation of Cronobacter spp. (Enterobacter sakazakii)

LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2009
G.I. Dancer
Abstract Aim:, To determine the critical component(s) of skim milk for biofilm formation of Cronobacter species. Methods and Results:, Biofilm forming ability of 72 Cronobacter strains in skim milk preparation was assayed by crystal violet staining. The results revealed that whey protein and casein are more important determinants of skim milk for biofilm formation than lactose, although there was a wide variation in biofilm forming ability. Biofilm structure and capsular material of six strains exhibiting different biofilm forming ability was investigated via electron microscopes. Scanning electron microscopy showed visually that while the strong biofilm formers (E27B, FSM 30 and 2·82) resulted in almost complete coagulation of skim milk, the weak biofilm formers (55, FSM 290 and 2·84) caused less coagulation. No capsule was clearly delineated in transmission electron micrographs of either strong or weak biofilm formers. Conclusion:, These results indicate that, for biofilm formation of Cronobacter species in skim milk, nitrogen source is probably a more important determinant than carbohydrate, and that strong biofilm formers are responsible for substantial coagulation of skim milk. Significance and Impact of the Study:, This study provides information for better understanding of the underlying mechanisms by which Cronobacter species form biofilm in infant formula milk. [source]

Analysis of Streptococcus mutans biofilm proteins recognized by salivary immunoglobulin A

MOLECULAR ORAL MICROBIOLOGY, Issue 5 2009
T. Sanui
Introduction:, The purpose of this study was to examine the Streptococcus mutans biofilm cellular proteins recognized by immunoglobulin A (IgA) in saliva from various caries-defined populations. Methods:, Biofilm and planktonic S. mutans UA159 cells were prepared. The proteins were extracted, separated by two-dimensional gel electrophoresis, transferred to blotting membranes, and probed for IgA using individual saliva samples from three groups of subjects; those who developed 0 caries (no active caries), 5,9 caries (medium), or more than 10 caries (severe) over a 12-month interval. Results:, Several proteins were recognized by salivary IgA in all groups of saliva but spot distribution and intensity varied greatly between the groups, and some proteins were recognized more strongly in biofilm cells than in planktonic culture, and vice versa. Furthermore, 15 proteins were only recognized by saliva from the ,no active caries' group, and four proteins were recognized by saliva samples from subjects in all three groups. Specifically, antigen I/II was recognized less in biofilm cells by caries-free saliva compared with planktonic cells. However, salivary IgA antibody to antigen I/II was absent in blots using saliva from the ,medium caries' and ,severe caries' groups. Conclusion:, The bacterial molecules recognized by caries-free saliva are significant factors for S. mutans caries formation, and their inhibition could be a therapeutic target. In addition, saliva of caries-free subjects includes significant IgA antibody against antigen I/II of S. mutans, indicating a protective mechanism. However, microorganisms may protect themselves from host immune attack by forming biofilms and decreasing expression of antigen I/II. [source]

Characterization of Vernix Caseosa as a Natural Biofilm: Comparison to Standard Oil-Based Ointments

PEDIATRIC DERMATOLOGY, Issue 4 2000
Maria Imelda B. Bautista M.D.
Such infants have a structurally immature stratum corneum and lack a surface coating of vernix caseosa. In this study we examined the short-term effects of topical application of vernix caseosa to human skin and contrasted these effects with commonly used ointments and water-in-oil emulsions. Specifically, vernix, Eucerin®, Aquaphor®, and petrolatum were applied to the volar skin surface of adult volunteers. Surface electrical capacitance (SEC) and transepidermal water loss (TEWL) were measured as indices of surface hydration. Sorption-desorption profiles were performed to determine skin surface hydrophobicity. Particular attention was given to monitoring the acute (0,120 minutes) changes following vernix treatment in order to compare these effects with earlier reports on the rate of skin surface drying in newborn infants following birth. Immediately after vernix application there was an increase in the rate of water loss from the skin surface. Relative to control skin and skin treated with the ointments and water-in-oil emulsions, the application of vernix to freshly bathed human skin resulted in a unique profile of temporal change in baseline surface hydration, moisture accumulation, and water-holding capacity. These results demonstrate major differences between human vernix and standard oil-based topical ointments. The results provide a framework for discussing the various properties of topical barriers applied to the very low birthweight infant. [source]

Formation of Biofilm on Different Particulate Media Using Modified Kitchen Waste Extract as Initial Growth Substrate for Use in PCB Degradation

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5-6 2005
J. Auresenia
Abstract This study describes the formation of biofilm on two different particulate media using modified kitchen waste extract as initial growth medium, and the subsequent testing of the this biofilm to biodegrade polychlorinated biphenyls (PCBs). Two parallel completely mixed fluidized bed reactors, one using cement balls and the other using sand as particulate media, were operated in order to produce the biofilm. Modified kitchen waste extract was used as a growth substrate instead of the more expensive complex substrate. The medium was inoculated with microorganisms from tannery wastes. Performance of the biofilms formed in the two reactors were compared based on BOD and COD degradation rates, biomass growth rate, biofilm thickness and ease offluidization. The results demonstrate that a stable biofilm can be formed on readily available particulate materials using cheap substrate from kitchen wastes extracts. Furthermore, cement balls proved to be more suitable as particulate media compared to sand, possessing superior biofilm-forming characteristics. The biofilm formed on cement balls was tested for the degradation of PCBs. Initial PCB batch degradation tests showed that about 70% of PCBs degraded within six hours. Kinetics of PCB degradation followed the Monod model with Km = 561.98 mg/l and m,max=0.07 1/h. [source]

Simulation von Wachstum und Abtrag von Biomasse , Eine exemplarische Betrachtung für eine 2D-Modellierung

CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 4 2005
H. Horn
Abstract Das Beispiel eines Biofilters mit Konzentrationsgradienten entlang der Reaktorachse und in der aggregierten Biomasse auf dem Trägermaterial dokumentiert die Leistungsfähigkeit von 2D-Simulation sehr eindrucksvoll. Mit Hilfe der zweidimensionalen Darstellung kann sehr gut die Verteilung der aktiven heterotrophen Biomasse im Biofilm, aber auch im Biofilter abgebildet werden. [source]

Computer programs for estimating substrate flux into steady-state biofilms from pseudoanalytical solutions

COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2002
Chetan T. Goudar
Abstract Fixed-film processes employing microorganisms attached to an inert surface (biofilms) are widely used for biological treatment of municipal and industrial wastewater. For optimal design and analysis of these processes, mathematical models are necessary that describe the dynamics of contaminant transport within these biofilms and the associated contaminant utilization by the microorganisms. However, these governing equations that typically involve Fickian diffusion for contaminant transport and Monod kinetics for contaminant utilization are inherently nonlinear and have no closed form solutions except under special conditions. This can restrict their use in the classroom as cumbersome numerical techniques must be used for their solution. This problem is well documented in the literature and several authors have presented pseudoanalytical solutions that replace numerical solutions with algebraic equations. In the present study, we present pseudoanalytical solution-based computer programs for estimating substrate flux and biofilm thickness for a steady-state biofilm. Depending upon the intended end use, these programs can either partially or totally automate the solution process. In the partial automation mode, they can serve to enhance student understanding of important concepts related to steady-state biofilms, while complete automation can help bring more challenging and realistic problems associated with steady-state biofilms into the classroom. The programs have been tested on MATLAB version 5.0 and are available as freeware for educational purposes. © 2002 Wiley Periodicals, Inc. Comput Appl Eng Educ 10: 26,32, 2002; Published online in Wiley InterScience (www.interscience.wiley.com.); DOI 10.1002/cae.10017 [source]

Biofilm Growth and Bed Fluidization in a Fluidized Bed Reactor Packed with Support Materials of Low Density,

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2004
R.A. Saucedo-Terán
Abstract Support materials of low-density for fluidized bed reactors provide several operational advantages, including lower energy requirements and proper biofilm growth balance. The aim of this investigation was to study the extent of biofilm growth and bed fluidization in an experimental reactor, using polyester resin (,pr,=,1220,kg/m3) and vitrified expanded perlite (,vep,=,1710,kg/m3) as alternative support materials to conventional silica sand. A noteworthy amount of biofilm was observed to be attached to both support materials from the very beginning of the bioreactor operation. Nevertheless, there were significant variations in biofilm growth and activity over the course of the experimental trials. For both perlite and polyester beds, the highest biofilm mass and the highest total number of mesophilic bacteria were observed between the 7th and the 10th day, showing a steady state trend at the end of the experimental runs. The chemical oxygen demand (COD) removal levels were concomitant with biofilm mass and total mesophilic bacteria changes, although the polyester bed efficiency was slightly higher than that for the perlite bed. As expected, the polyester bed was fluidized at a lower re-circulation flow compared to the perlite bed. Reactor back-washing was not required for these support materials since biomass excess was adequately separated by means of a special internal device. The efficiencies of removal of organic matter achieved were acceptable (up to 78,%) despite the low volume of the support material (25,%) and the low hydraulic retention time (30,min). [source]

Enterococcus faecalis with the gelatinase phenotype regulated by the fsr operon and with biofilm-forming capacity are common in the agricultural environment

ENVIRONMENTAL MICROBIOLOGY, Issue 6 2009
Lilia Macovei
Summary The prevalence of gelatinase activity and biofilm formation among environmental enterococci was assessed. In total, 396 enterococcal isolates from swine and cattle faeces and house flies from a cattle farm were screened for gelatinase activity. The most prevalent phenotype on Todd,Hewitt agar with 1.5% skim milk was the weak protease (WP) (72.2% of isolates), followed by the strong protease (SP) 18.7%, and no protease (NP) (9.1%). The majority of WP isolates was represented by Enterococcus hirae (56.9%), followed by Enterococcus faecium (25.9%), Enterococcus casseliflavus (10.4%), Enterococcus gallinarum (5.2%) and Enterococcus saccharolyticus (1.7%). All WP isolates were negative for gelE (gelatinase) and sprE (serine protease) as well as the fsrABDC operon that regulates the two proteases, and only four isolates (7.0%) formed biofilms in vitro. All SP isolates were Enterococcus faecalis positive for the fsrABDC, gelE, sprE genes and the majority (91.2%) formed a biofilm. Diversity of NP isolates was relatively evenly distributed among E. hirae, E. faecium, E. casseliflavus, E. gallinarum, Enterococcus durans, E. saccharolyticus and Enterococcus mundtii. All NP isolates were negative for the fsr operon and only four E. hirae (11.1%) formed a biofilm. Of further interest was the loss of the gelatinase phenotype (18.9% of isolates) from SP isolates after 4 month storage at 4,8°C and several passages of subculture. Results of reverse transcription PCR analysis indicated that mRNA was produced for all the genes in the frs operon and sequencing of the gelE gene did not reveal any significant mutations. However, gelatinase was not detectable by Western blot analysis. Our study shows that E. faecalis with the complete fsr operon and the potential to form a biofilm are relatively common in the agricultural environment and may represent a source/reservoir of clinically relevant strains. In addition, many environmental enterococci, especially E. hirae, produce an unknown WP that can hydrolyse casein but does not contribute to biofilm formation. The stability of the gelatinase phenotype in E. faecalis and its regulation will require additional studies. [source]

Metagenomic and stable isotopic analyses of modern freshwater microbialites in Cuatro Ciénegas, Mexico

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2009
Mya Breitbart
Summary Ancient biologically mediated sedimentary carbonate deposits, including stromatolites and other microbialites, provide insight into environmental conditions on early Earth. The primary limitation to interpreting these records is our lack of understanding regarding microbial processes and the preservation of geochemical signatures in contemporary microbialite systems. Using a combination of metagenomic sequencing and isotopic analyses, this study describes the identity, metabolic potential and chemical processes of microbial communities from living microbialites from Cuatro Ciénegas, Mexico. Metagenomic sequencing revealed a diverse, redox-dependent microbial community associated with the microbialites. The microbialite community is distinct from other marine and freshwater microbial communities, and demonstrates extensive environmental adaptation. The microbialite metagenomes contain a large number of genes involved in the production of exopolymeric substances and the formation of biofilms, creating a complex, spatially structured environment. In addition to the spatial complexity of the biofilm, microbial activity is tightly controlled by sensory and regulatory systems, which allow for coordination of autotrophic and heterotrophic processes. Isotopic measurements of the intracrystalline organic matter demonstrate the importance of heterotrophic respiration of photoautotrophic biomass in the precipitation of calcium carbonate. The genomic and stable isotopic data presented here significantly enhance our evolving knowledge of contemporary biomineralization processes, and are directly applicable to studies of ancient microbialites. [source]

The characterization of functions involved in the establishment and maturation of Klebsiella pneumoniae in vitro biofilm reveals dual roles for surface exopolysaccharides

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2008
Damien Balestrino
Summary The ability to form biofilm is seen as an increasingly important colonization strategy among both pathogenic and environmental Klebsiella pneumoniae strains. The aim of the present study was to identify abiotic surface colonization factors of K. pneumoniae using different models at different phases of biofilm development. A 2200 K. pneumoniae mutant library previously obtained by signature-tagged mutagenesis was screened in static and dynamic culture models to detect clones impaired at early and/or mature stages of biofilm formation. A total of 28 mutants were affected during late phases of biofilm formation, whereas 16 mutants displayed early adhesion defect. These mutants corresponded to genes involved in potential cellular and DNA metabolism pathways and to membrane transport functions. Eight mutants were deficient in capsule or LPS production. Gene disruption and microscopic analyses showed that LPS is involved in initial adhesion on both glass and polyvinyl-chloride and the capsule required for the appropriate initial coverage of substratum and the construction of mature biofilm architecture. These results give new insight into the bacterial factors sequentially associated with the ability to colonize an abiotic surface and reveal the dual roles played by surface exopolysaccharides during K. pneumoniae biofilm formation. [source]

Pseudomonas fluorescens' view of the periodic table

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2008
Matthew L. Workentine
Summary Growth in a biofilm modulates microbial metal susceptibility, sometimes increasing the ability of microorganisms to withstand toxic metal species by several orders of magnitude. In this study, a high-throughput metal toxicity screen was initiated with the aim of correlating biological toxicity data in planktonic and biofilm cells to the physiochemical properties of metal ions. To this end, Pseudomonas fluorescens ATCC 13525 was grown in the Calgary Biofilm Device (CBD) and biofilms and planktonic cells of this microorganism were exposed to gradient arrays of different metal ions. These arrays included 44 different metals with representative compounds that spanned every group of the periodic table (except for the halogens and noble gases). The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and minimum biofilm eradication concentration (MBEC) values were obtained after exposing the biofilms to metal ions for 4 h. Using these values, metal ion toxicity was correlated to the following ion-specific physicochemical parameters: standard reduction-oxidation potential, electronegativity, the solubility product of the corresponding metal,sulfide complex, the Pearson softness index, electron density and the covalent index. When the ions were grouped according to outer shell electron structure, we found that heavy metal ions gave the strongest correlations to these parameters and were more toxic on average than the other classes of the ions. Correlations were different for biofilms than for planktonic cells, indicating that chemical mechanisms of metal ion toxicity differ between the two modes of growth. We suggest that biofilms can specifically counter the toxic effects of certain physicochemical parameters, which may contribute to the increased ability of biofilms to withstand metal toxicity. [source]

Heterotrophic symbionts of phototrophic consortia: members of a novel diverse cluster of Betaproteobacteria characterized by a tandem rrn operon structure

ENVIRONMENTAL MICROBIOLOGY, Issue 11 2007
Kristina R. Pfannes
Summary Phototrophic consortia represent the most highly developed type of interspecific association of bacteria and consist of green sulfur bacterial epibionts attached around a central colourless rod-shaped bacterium. Based on 16S rRNA gene sequencing, the central bacterium of the consortium ,Chlorochromatium aggregatum' was recently shown to represent a novel and phylogenetically isolated lineage of the Comamonadaceae within the ,-subgroup of the Proteobacteria. To date, 19 types of phototrophic consortia are distinguished based on the different 16S rRNA gene sequences of their epibionts, but the diversity and phylogenetic relationships of the heterotrophic partner bacteria are still unknown. We developed an approach based on the specific rrn (ribosomal RNA) operon structure of the central bacterium of ,C. aggregatum' to recover 16S rRNA gene sequences of other central bacteria and their close relatives from natural consortia populations. Genomic DNA of the central bacterium of ,C. aggregatum' was first enriched several hundred-fold by employing a selective method for growth of consortia in a monolayer biofilm followed by a purification of the genome of the central bacterium by cesium chloride-bisbenzimidazole equilibrium density gradient centrifugation. A combination of inverse PCR, cloning and sequencing revealed that two rrn operons of the central bacterium are arranged in a tandem fashion and are separated by an unusually short intergenic region of 195 base pairs. This rare gene order was exploited to screen various natural microbial communities by PCR. We discovered a diverse and previously unknown subgroup of Betaproteobacteria in the chemoclines of freshwater lakes. This group was absent in other freshwater and soil samples. All the 16S rRNA gene sequences recovered are related to that of the central bacterium of ,C. aggregatum'. Fluorescence in situ hybridization indicated that two of these sequences originated from central bacteria of different phototrophic consortia, which, however, were only distantly related to the central bacterium of ,C. aggregatum'. Based on a detailed phylogenetic analysis, these central bacterial symbionts of phototrophic consortia have a polyphyletic origin. [source]

d -Alanyl ester depletion of teichoic acids in Lactobacillus reuteri 100-23 results in impaired colonization of the mouse gastrointestinal tract

ENVIRONMENTAL MICROBIOLOGY, Issue 7 2007
Jens Walter
Summary The dlt operon of Gram-positive bacteria encodes proteins required for the incorporation of d -alanine esters into cell wall-associated teichoic acids (TA). d -Alanylation of TA has been shown to be important for acid tolerance, resistance to antimicrobial peptides, adhesion, biofilm formation, and virulence of a variety of pathogenic organisms. The aim of this study was to determine the importance of d -alanylation for colonization of the gastrointestinal tract by Lactobacillus reuteri 100-23. Insertional inactivation of the dltA gene resulted in complete depletion of d -alanine substitution of lipoteichoic acids. The dlt mutant had similar growth characteristics as the wild type under standard in vitro conditions, but formed lower population sizes in the gastrointestinal tract of ex- Lactobacillus -free mice, and was almost eliminated from the habitat in competition experiments with the parental strain. In contrast to the wild type, the dlt mutant was unable to form a biofilm on the forestomach epithelium during gut colonization. Transmission electron microscope observations showed evidence of cell wall damage of mutant bacteria present in the forestomach. The dlt mutant had impaired growth under acidic culture conditions and increased susceptibility to the cationic peptide nisin relative to the wild type. Ex vivo adherence of the dlt mutant to the forestomach epithelium was not impaired. This study showed that d -alanylation is an important cell function of L. reuteri that seems to protect this commensal organism against the hostile conditions prevailing in the murine forestomach. [source]

Biofilm formation and cellulose expression among diverse environmental Pseudomonas isolates

ENVIRONMENTAL MICROBIOLOGY, Issue 11 2006
Susanne Ude
Summary The ability to form biofilms is seen as an increasingly important colonization strategy among both pathogenic and environmental bacteria. A survey of 185 plant-associated, phytopathogenic, soil and river Pseudomonas isolates resulted in 76% producing biofilms at the air,liquid (A,L) interface after selection in static microcosms. Considerable variation in biofilm phenotype was observed, including waxy aggregations, viscous and floccular masses, and physically cohesive biofilms with continuously varying strengths over 1500-fold. Calcofluor epifluorescent microscopy identified cellulose as the matrix component in biofilms produced by Pseudomonas asplenii, Pseudomonas corrugata, Pseudomonas fluorescens, Pseudomonas marginalis, Pseudomonas putida, Pseudomonas savastanoi and Pseudomonas syringae isolates. Cellulose expression and biofilm formation could be induced by the constitutively active WspR19 mutant of the cyclic-di-GMP-associated, GGDEF domain-containing response regulator involved in the P. fluorescens SBW25 wrinkly spreader phenotype and cellular aggregation in Pseudomonas aeruginosa PA01. WspR19 could also induce P. putida KT2440, which otherwise did not produce a biofilm or express cellulose, as well as Escherichia coli K12 and Salmonella typhimurium LT2, both of which express cellulose yet lack WspR homologues. Statistical analysis of biofilm parameters suggest that biofilm development is a more complex process than that simply described by the production of attachment and matrix components and bacterial growth. This complexity was also seen in multivariate analysis as a species-ecological habitat effect, underscoring the fact that in vitro biofilms are abstractions of those surface and volume colonization processes used by bacteria in their natural environments. [source]

In situ substrate conversion and assimilation by nitrifying bacteria in a model biofilm

ENVIRONMENTAL MICROBIOLOGY, Issue 9 2005
Armin Gieseke
Summary Local nitrification and carbon assimilation activities were studied in situ in a model biofilm to investigate carbon yields and contribution of distinct populations to these activities. Immobilized microcolonies (related to Nitrosomonas europaea/eutropha, Nitrosomonas oligotropha, Nitrospira sp., and to other Bacteria) were incubated with [14C]-bicarbonate under different experimental conditions. Nitrifying activity was measured concomitantly with microsensors (oxygen, ammonium, nitrite, nitrate). Biofilm thin sections were subjected to fluorescence in situ hybridization (FISH), microautoradiography (MAR), and local quantification of [14C]-bicarbonate uptake (beta microimaging). Nitrifying activity and tracer assimilation were restricted to a surface layer of different thickness in the various experiments (substrate or oxygen limitation). Excess oxygen uptake under all conditions revealed heterotrophic activity fuelled by decay or excretion products during active nitrification. Depth limits and intensity of tracer incorporation profiles were in agreement with ammonia-oxidation activity (measured with microsensors), and distribution of incorporated tracer (detected with MAR). Microautoradiography revealed a sharp individual response of distinct populations in terms of in-/activity depending on the (local) environmental conditions within the biofilm. Net in situ carbon yields on N, expressed as e, equivalent ratios, varied between 0.005 and 0.018, and, thus, were in the lower range of data reported for pure cultures of nitrifiers. [source]

Adaptive responses to antimicrobial agents in biofilms

ENVIRONMENTAL MICROBIOLOGY, Issue 8 2005
Barbara Szomolay
Summary Bacterial biofilms demonstrate adaptive resistance in response to antimicrobial stress more effectively than corresponding planktonic populations. We propose here that, in biofilms, reaction-diffusion limited penetration may result in only low levels of antimicrobial exposure to deeper regions of the biofilm. Sheltered cells are then able to enter an adapted resistant state if the local time scale for adaptation is faster than that for disinfection. This mechanism is not available to a planktonic population. A mathematical model is presented to illustrate. Results indicate that, for a sufficiently thick biofilm, cells in the biofilm implement adaptive responses more effectively than do freely suspended cells. Effective disinfection requires applied biocide concentration that increases quadratically or exponentially with biofilm thickness. [source]

Novel microbial diversity adherent to plant biomass in the herbivore gastrointestinal tract, as revealed by ribosomal intergenic spacer analysis and rrs gene sequencing

ENVIRONMENTAL MICROBIOLOGY, Issue 4 2005
Ross Larue
Summary It is well recognized that a dynamic biofilm develops upon plant biomass in the herbivore gastrointestinal tract, but this component of the microbiome has not previously been specifically sampled, or directly compared with the biodiversity present in the planktonic fraction of digesta. In this study, the digesta collected from four sheep fed two different diets was separated into three fractions: the planktonic phase, and the microbial populations either weakly or tightly adherent to plant biomass. The community DNA prepared from each fraction was then subjected to both ribosomal intergenic spacer analysis (RISA) and denaturing gradient gel electrophoresis (DGGE). Both types of analysis showed that dietary factors influence community structure, and that the adherent fractions produced more complex profiles. The RIS-clone libraries prepared from the planktonic and adherent populations were then subjected to restriction fragment length polymorphism (RFLP) and DNA sequence analyses, which resulted in a far greater degree of discrimination among the fractions. Although many of the sequenced clones from the adherent populations were assigned to various clusters within the low G+C Gram-positive bacteria, the clone libraries from animals consuming an all-grass diet were largely comprised of novel lineages of Clostridium, while in animals consuming the starch-containing diet, Selenomonas and Ruminococcus spp. were the dominant low G+C Gram-positive bacteria. Additionally, the libraries from hay-fed animals also contained clones most similar to asaccharolytic Clostridia, and other Gram-positive bacteria that specialize in the transformation of plant phenolic compounds and the formation of cinnamic, phenylacetic and phenylpropionic acids. These results reveal, for the first time, the phylogeny of adherent subpopulations that specialize in the transformation of plant lignins and other secondary compounds, which potentiate polysaccharide hydrolysis by other members of the biofilm. [source]

The effect of cleaning and disinfecting the sampling well on the microbial communities of deep subsurface water samples

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2005
Odile Basso
Summary Our knowledge of the microbial characteristics of deep subsurface waters is currently very limited, mainly because of the methods used to collect representative microbial samples from such environments. In order to improve this procedure, a protocol designed to remove the unspecific, contaminant biofilm present on the walls of an approximately 800 m deep well is proposed. This procedure included extensive purges of the well, a mechanical cleaning of its wall, and three successive chlorine injections to disinfect the whole line before sampling. Total bacterial counts in water samples decreased from 2.5 × 105 to 1.0 × 104 per millilitre during the cleaning procedure. Culture experiments showed that the first samples were dominated by sulfate-reducers and heterotrophs, whereas the final sample was dominated by oligotrophic and hydrogenotrophic bacteria. Community structures established on the diversity of the 16S rRNA genes and data analysis revealed that the water sample collected, after a purge without removal of the biofilm, was characterized by numerous phyla which are not representative of the deep subsurface water. On the other hand, several bacterial phyla were only detected after the full cleaning of the well, and were considered as important components of the subsurface ecosystem which would have been missed in the absence of well cleaning. [source]

Specificity in the settlement , modifying response of bacterial biofilms towards zoospores of the marine alga Enteromorpha

ENVIRONMENTAL MICROBIOLOGY, Issue 5 2003
Pratixa Patel
Summary Previous studies have shown that the rate of settlement of zoospores of the green alga Enteromorpha is stimulated by mixed microbial biofilms and that the number of zoospores settling is positively correlated with the number of bacteria in the biofilm. In the present study the specificity of this relationship has been investigated. Ninety-nine strains of marine bacteria were isolated from natural biofilms on rocks and the surface of Enteromorpha plants. Isolates were screened by denaturing gradient gel electrophoresis (DGGE) to eliminate replicates and 16S rDNA sequencing identified a total of 37 unique strains. Phylogenetic analysis revealed that the isolated bacterial strains belonged to three groups ,- Proteobacteria (28 strains), Cytophaga-Flavobacteria-Bacteroid (CFB) group (six strains) and ,- Proteobacteria (one strain). Two strains were unassigned, showing < 93% sequence similarity with the CFB group. The main genera of ,- Proteobacteria were Pseudoalteromonas (14 strains), Vibrio (five strains), Shewanella (five strains), Halomonas (three strains) and Pseudomonas (one strain). Spore settlement experiments were conducted on single-species biofilms, developed for different times on glass slides. The effect of correcting spore settlement values for biofilm density was evaluated. Results showed that the effect of bacterial strains on spore settlement was strain- but not taxon-specific and activity varied with the age of the biofilm. However, most of the strains belonging to genera Vibrio and Shewanella showed stimulation. Pseudoalteromonas strains showed a range of effects including settlement-inhibiting, paralysing and lysing activities. Spatial analysis of bacterial density in the presence and absence of spores revealed a range of different types of association between spores and bacteria. Overall, the spatial association between spores and bacteria appears to be independent of the overall quantitative influence of bacterial cells on spore settlement. [source]

Development and experimental validation of a conceptual model for biotrickling filtration of H2S

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2003
Seongyup Kim
A dynamic model that describes the behavior of high-performance hydrogen sulfide (H2S)-degrading biotrickling filters for odor control was developed. The model attempts to accurately describe pollutant mass transfer in the biotrickling filter, i.e., external mass transfer resistances, and both direct gas-biofilm and gas-liquid-biofilm mass transfer were considered. In order to calibrate the model, an innovative differential biotrickling filter was constructed in which the effect of air velocity on the removal of H2S could be studied. Model outputs were compared with experimental data to determine the sensitivity of the system to selected parameters. At low H2S concentration, diffusion of H2S within the biofilm, and biofilm thickness were the major governing factors among nine considered model parameters. At higher H2S concentrations and lower air flow rates, external mass transfer played a very important role. This new finding, confirmed experimentally, has important implications, as it proves that the performance limit of H2S degrading biotrickling filters has not yet been reached. [source]

Trout density and health in a stream with variable water temperatures and trace element concentrations: Does a cold-water source attract trout to increased metal exposure?

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2009
David D. Harper
Abstract A history of hard-rock mining has resulted in elevated concentrations of heavy metals in Prickly Pear Creek (MT, USA). Remediation has improved water quality; however, dissolved zinc and cadmium concentrations still exceed U.S. Environmental Protection Agency water-quality criteria. Physical habitat, salmonid density, fish health, and water quality were assessed, and metal concentrations in fish tissues, biofilm, and macroinvertebrates were determined to evaluate the existing condition in the watershed. Cadmium, zinc, and lead concentrations in fish tissues, biofilm, and invertebrates were significantly greater than those at the upstream reference site and an experimental site farther downstream of the confluence. Fish densities were greatest, and habitat quality for trout was better, downstream of the confluence, where water temperatures were relatively cool (16°C). Measures of fish health (tissue metal residues, histology, metallothionein concentrations, and necropsies), however, indicate that the health of trout at this site was negatively affected. Trout were in colder but more contaminated water and were subjected to increased trace element exposures and associated health effects. Maximum water temperatures in Prickly Pear Creek were significantly lower directly below Spring Creek (16°C) compared to those at an experimental site 10 km downstream (26°C). Trout will avoid dissolved metals at concentrations below those measured in Prickly Pear Creek; however, our results suggest that the preference of trout to use cool water temperatures may supersede behaviors to avoid heavy metals. [source]

Development of photosynthetic biofilms affected by dissolved and sorbed copper in a eutrophic river

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002
Christiane Barranguet
Abstract Photosynthetic biofilms are capable of immobilizing important concentrations of metals, therefore reducing bioavailability to organisms. But also metal pollution is believed to produce changes in the microalgal species composition of biofilms. We investigated the changes undergone by natural photosynthetic biofilms from the River Meuse, The Netherlands, under chronic copper (Cu) exposure. The suspended particles in the river water had only a minor effect on reduction of sorption and toxicity of Cu to algae. Biofilms accumulated Cu proportionally to the added concentration, also at the highest concentration used (9 ,M Cu). The physiognomy of the biofilms was affected through the growth of the chain-forming diatom Melosira varians, changing from long filaments to short tufts, although species composition was not affected by the Cu exposure. The Cu decreased phosphate uptake and algal biomass measured as chl a, which degraded exponentially in time. Photosynthetic activity was always less sensitive than algal biomass; the photon yield decreased linearly in time. The protective and insulating role of the biofilm, supported by ongoing autotrophic activity, was indicated as essential in resisting metal toxicity. We discuss the hypothesis that the toxic effects of Cu progress almost independently of the species composition, counteracting ongoing growth, and conclude that autotrophic biofilms act as vertical heterogeneous units. Effective feedback mechanisms and density dependence explain several discrepancies observed earlier. [source]

Enzymes in the acquired enamel pellicle

EUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2005
Christian Hannig
The acquired pellicle is a biofilm, free of bacteria, covering oral hard and soft tissues. It is composed of mucins, glycoproteins and proteins, among which are several enzymes. This review summarizes the present state of research on enzymes and their functions in the dental pellicle. Theoretically, all enzymes present in the oral cavity could be incorporated into the pellicle, but apparently enzymes are adsorbed selectively onto dental surfaces. There is clear evidence that enzymes are structural elements of the pellicle. Thereby they exhibit antibacterial properties but also facilitate bacterial colonization of dental hard tissues. Moreover, the immobilized enzymes are involved in modification and in homeostasis of the salivary pellicle. It has been demonstrated that amylase, lysozyme, carbonic anhydrases, glucosyltransferases and fructosyltransferase are immobilized in an active conformation in the pellicle layer formed in vivo. Other enzymes, such as peroxidase or transglutaminase, have been investigated in experimental pellicles. Despite the depicted impact of enzymes on the formation and function of pellicle, broader knowledge on their properties in the in vivo -formed pellicle is required. This might be beneficial in the development of new preventive and diagnostic strategies. [source]

Prevention and control of biofilm-based medical-device-related infections

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2010
Iolanda Francolini
Abstract Biofilms play a pivotal role in healthcare-associated infections, especially those related to the implant of medical devices, such as intravascular catheters, urinary catheters and orthopaedic implants. This paper reviews the most successful approaches for the control and prevention of these infections as well as promising perspectives for the development of novel devices refractory to microbial adhesion, colonization and biofilm formation. [source]

Microbial biofilms associated with biliary stent clogging

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2010
Emilio Guaglianone
Abstract Endoscopic stenting is a palliative approach for the treatment of diseases involving biliary obstruction. Its major limitation is represented by stent occlusion, followed by life-threatening cholangitis, often requiring stent removal and replacement. Although it has been suggested that microbial colonization of biliary stents could play a role in the clogging process, the so far available data, particularly on the role of anaerobic bacteria, are not enough for a comprehensive description of this phenomenon. Our study was focused on the analysis of 28 explanted biliary stents by culturing, denaturing gradient gel electrophoresis and scanning electron microscopy to identify all the aerobic/anaerobic bacteria and fungi involved in the colonization of devices and to verify the ability of isolated anaerobic bacterial strains to form a biofilm in order to better understand the mechanisms of stent clogging. [source]

Helicobacter pylori, coccoid forms and biofilm formation

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2009
Leif Percival Andersen
Abstract Electron microscopic studies have shown that Helicobacter pylori occurs in three stages: spiral forms, coccoid forms and degenerative forms. The spiral forms are viable, culturable, virulent and can colonize experimental animals and induce inflammation. The coccoid forms may also be viable but are nonculturable, less virulent and are less likely to colonize and induce inflammation in experimental animals than the spiral forms. The degenerative forms are pyknotic, nonculturable, coccoid forms of dead H. pylori. These forms cannot be cultured and the cell membrane has disintegrated but gene material can be detected by PCR in water supplies. There is no substantial evidence for viable H. pylori persisting in water supplies. Epidemiological studies suggest that environmental water is a risk factor for H. pylori infection when compared with tap water, and formation of H. pylori biofilm cannot be excluded. Helicobacter pylori does not seem to take part in biofilm formation in the oral cavity even though the bacterium may be detected. [source]

agr -Genotyping and transcriptional analysis of biofilm-producing Staphylococcus aureus

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2007
Viviana Cafiso
Abstract We investigated the correlation between biofilm production and the accessory-gene-regulator (agr) in 29 strains isolated from catheter-associated infections compared to a control group (30 isolates). All strains were tested for their ability to produce biofilm in a static system, and their agr genotype was determined. ScaI-restriction fragment length polymorphism for agr -typing showed that strong biofilm-producing strains belong to agr - type II. We found two new agr -variants, and sequence analysis of the three PCR products revealed the insertion of IS256 within the agr- locus. Biofilm production was assessed and correlated with agr functionality, with the expression of the ica -operon and of two transcriptional regulators, sarA and rsbU. Our data show that agr -II strains produce large amounts of biofilm, possess a defective agr -system show early transcription of icaA and are defective in haemolysin activity, icaR transcription, and in the expression of the ,B activator rsbU. Strains with agrIII are medium biofilm producers, have an inactive agr -system, but express icaAR and rsbU in the late- and postexponential growth phases. In agrI,IV- and -IA-variants, medium or weak biofilm production was found. In these strains, the agr -locus was fully functional, rsbU- icaR and icaA were found in the late- and/or postexponential phases. Biofilm production was not affected by sarA. [source]