ISSN:0892-7014    

DOI:10.1080/08927019609386266

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Microbial biofilms were formed on coupons with defined coatings in once‐through laminar flow fields of controlled bulk‐phase composition and shear. Dilute media were utilized to select for biofilm growth. The formation, succession, and stability of the biofilms were monitored with non‐destructive on‐line methods (fluorescence, bioluminescence, attenuated total reflectance Fourier transform infrared spectrometry [ATR‐FTIR] and electrochemical impedance spectroscopy) and by high resolution destructive analysts (viable and direct counts and phospholipid fatty acid signature methods) at the termination of the experiments. Biofilms of reproducible composition can be formed and the order of inoculation of multi‐component biofilms affects their composition at harvest. The corrosion rates of mild steel depended on the biofilm composition but not the attached biomass. Examination of biofilms with the scanning vibrating electrode in a microscope field showed effects of heterogeneity in biofilm structure which promoted localized anodic activity.Pseudomonasstains were engineered to contain theluxgene cassette as a “reporter”; and the formation of the exopolymer alginate was shown not to promote attachment of the strain or secondary colonization byVibrio. Examination of mutants forming different alginate structures showed differential attachment and biofilm structure. Studies of mutants of lipopolysaccharide structure showed differential attachment to substrata. Specific antifouling and fouling‐release coatings showed a wide range of attachment and release properties as well as sublethal toxicity.

ISSN:0892-7014    

DOI:10.1080/08927019609386267

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A putative polysaccharide adhesin which mediates non‐specific attachment ofHyphomonasMHS‐3 (MHS‐3) to hydrophilic substrata has been isolated and partially characterized. A polysaccharide‐enriched portion of the extracellular polymeric substance (EPSP) from MHS‐3 was separated into four fractions using high performance size exclusion chromatography (HPSEC). Comparison of chromatograms of EPSPfrom MHS‐3 and a reduced adhesion strain (MHS‐3 rad) suggested that one EPSPfraction, which consisted of carbohydrate, served as an adhesin. Adsorption of this fraction to germanium (Ge) was investigated using attenuated total reflection Fourier transform infrared (ATR/FT‐IR) spectrometry. Binding curves indicated that the isolated fraction had a relatively high affinity for Ge when ranked against an adhesive protein fromMytilis edulis, mussel adhesive protein (MAP) and an acidic polysaccharide (alginate fromMacrocystis pyrifera). Spectral features were used to identify the fraction as a polysaccharide previously reported to adsorb preferentially out of the EPSPmixture. Conditioning the Ge substratum with either bovine serum albumin (BSA) or MAP decreased the adsorption of the adhesive polysaccharide significantly. Conditioning Ge with these proteins also decreased adhesion of whole cells.

ISSN:0892-7014    

DOI:10.1080/08927019609386268

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A mixed‐culture biofilm (MCB) model is available which describes the progression of biofilm thickness and the spatial distribution and development in time of dissolved and paniculate components in the biofilm. The MCB model is able to predict the physico‐chemical conditions at the interface between the biofilm and the solid surface, on which the biofilm grows, as a function of the conditions in the bulk fluid, the microbial composition of the biofilm, and the transport and transformation processes which take place in the biofilm. The mass balance equations of the MCB model are generally valid and can be applied to almost any microbial system if its kinetics and stoichiometry can be provided. AQUASIM is a new computer program for the identification and simulation of aquatic systems. The program solves the equations of the MCB model. It has a window‐type user interface and includes routines for simulation, sensitivity analysis, automatic parameter estimation and data fitting. The MCB model has been developed and is primarily used in the field of waste water treatment. However, under certain conditions and with some additional simplifications this model can also be used for the investigation of biofouling and biocorrosion problems. The possibilities and limitations of the application of the MCB model and of AQUASIM to this type of problem are briefly discussed.

ISSN:0892-7014    

DOI:10.1080/08927019609386269

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Biofilm formation is discussed in terms of the ecological processes involved in their formation. It is emphasised that any cell responds to its environment i.e. to the composition of a liquid layer a few microns thick adjacent to the cell surface. The concept of multidimensional habitat domains defining the growth limits to every species is introduced, and put into the context of competition between different organisms. Activity domains of organisms are discussed and a definition for the niche of an organism introduced. The development of a biofilm on a clean surface is described. The constant depth film fermenter is introduced as an appropriate tool for investigating spatial and temporal sequence in biofilm formation. Finally, nutrient concentration is considered and the effects of diffusion limitation on film structure explored with the aid of a cellular automaton model.

ISSN:0892-7014    

DOI:10.1080/08927019609386270

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) were compared as tools for the observation of bacterial biofilms developed on carbon steel and AISI 316 stainless steel surfaces under stagnant conditions. Biofilms were generated in batch cultures of two different isolates of marine sulphate reducing bacteria (SRB) and in cultures consisting of mixed populations of acidophilic bacteria, known as “acid streamers”;. Imaging of single SRB cells on mica was also carried out to reveal the surface topography of individual bacterial cells at nanometre resolution. Following the removal of biofilms, the stainless steel surfaces were profiled using AFM to determine the degree of steel deterioration. ESEM and AFM studies of bacterial biofilmsin‐situ, gave both qualitative and quantitative information on biofilm structure at high resolution. The use of AFM image analysis software allowed estimation of the width and height of bacterial cells, the thickness and width of exopolymeric (EPS) capsule and bacterial flagella, as well as characterisation of the surface roughness of the steel, including measurements of depth and diameter of individual pits. Exposure of stainless steel specimens to acid streamers resulted in a significant increase in the surface roughness of the steel, compared to specimens placed in sterile medium.

ISSN:0892-7014    

DOI:10.1080/08927019609386271

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Manganese‐ and iron‐oxidizing bacteria (MFOB) are widely implicated in microbially influenced corrosion, often in association with sulfate‐reducing bacteria (SRB). Traditionally MFOB have been assigned a passive role in the corrosion process, promoting differential aeration cells, and providing oxygen depleted conditions conducive to the growth and corrosive attack of SRB. Recent work, summarized in this article, demonstrates that manganese biofouling alters the electrochemical behavior of stainless steel (SS), and suggests that MFOB are more active in localized corrosion than traditionally held. The paper discusses the chemistry and potentially corrosive impact of manganese and iron oxides on SS, explores the possible relationship between MFOB and SRB, and proposes a model to describe the synergistic influence these organisms may exert in the corrosion process.

ISSN:0892-7014    

DOI:10.1080/08927019609386272

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Sulphidogenic bacteria in oil reservoirs are of great economic importance in terms of souring, fouling and corrosion. Mixed cultures containing these bacteria were isolated from chalk formations in North Sea oil reservoirs. These were thermophilic cultures, growing optimally at 60°C. Oil formations are porous matrices, providing a very large surface area and ideal conditions for bacterial attachment, survival and growth. This study included assessments of sulphide production rates of thermophilic (t‐)sulphidogen consortia with and without additional surfaces. The availability of a surface contributed significantly to the rate and extent of sulphide generation. Surfaces were offered in varying amounts to growing planktonic cultures: significantly more sulphide was produced from cultures in contact with a surface than from identical cultures in the absence of a surface. In another series of experiments, t‐sulphidogens were added to chalk rock chips in the presence of nutrients and incubated for several months. This resulted in rapid sulphide generation, the final concentration being related to the initial nutrient concentration. Subsequent nutrient addition resulted in renewed sulphide generation. It is suggested that bacteria in reservoirs can withstand long periods of nutrient deprivation while attached within the porous rock matrix and opportunistically utilise nutrients when they become available.

ISSN:0892-7014    

DOI:10.1080/08927019609386273

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Protein/ligand interactions involved in mediating adhesion between microorganisms and biological surfaces have been well‐characterized in some cases (e.g.pathogen/host interactions). The strategies microorganisms employ for attachment to inert surfaces have not been so clearly elucidated. An experimental approach is presented which addresses the issues from the point of view of molecular interactions occurring at the interface.

ISSN:0892-7014    

DOI:10.1080/08927019609386274

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Stages in conidiun attachment to surfaces ofLemmoniera aquaticaandMycocentrospora filiformis(freshwater Hyphomycetes) were studied at the light microscope and scanning and transmission electron microscope levels. Sigmoid conidia ofM. filiformisattach by pre‐existing conidial mucilage at the spore pole and at a point along the conidial body. Tetraradiate conidia of L.aquaticaattach by the thigmotropic release of mucilage at the tips of the three “arms”;. Germination in both species is followed by the production of germ tubes, germ hyphae and appressoria. The chemical composition of the mucilage involved in attachment was determined by enzymatic studies and lectin‐gold cytochemical studies. The major component was found to be acidic poly‐saccharide, comprising mainly ß‐1, 3‐glucan, N‐acetyl‐D‐glucosamine and N‐acetyl‐neuraminic acid. Variation in mucilage composition exists between the two species, among different structures of the same species, and on different regions of the same structure. This indicates that mucilage producton in the two species is a dynamic process.The ability to secure rapid spore attachment, often in turbulent condition, would be a competitive advantage to these saprobic fungi in the colonization of substrata.

ISSN:0892-7014    

DOI:10.1080/08927019609386275

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor