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Biofilm Matrix (biofilm + matrix)
Selected Abstractsica and beyond: biofilm mechanisms and regulation in Staphylococcus epidermidis and Staphylococcus aureusFEMS MICROBIOLOGY LETTERS, Issue 2 2007James P. O'Gara Abstract Recent progress in elucidating the role of the icaADBC -encoded polysaccharide intercellular adhesin (PIA) or polymeric N -acetyl-glucosamine (PNAG) in staphylococcal biofilm development has in turn contributed significantly to our understanding of the pathogenesis of device-related infections. Nevertheless, our understanding of how the ica locus and PIA/PNAG biosynthesis are regulated is far from complete and many questions remain. Moreover, beyond ica, evidence is now emerging for the existence of ica -independent biofilm mechanisms in both Staphylococcus aureus and Staphylococcus epidermidis. Teichoic acids, which are a major carbohydrate component of the S. epidermidis biofilm matrix and the major cell wall autolysin, play an important role in the primary attachment phase of biofilm development, whereas the cell surface biofilm-associated protein and accumulation-associated protein are capable of mediating intercellular accumulation. These findings raise the exciting prospect that other surface proteins, which typically function as antigenic determinants or in binding to extracellular matrix proteins, may also act as biofilm adhesins. Given the impressive array of surface proteins expressed by S. aureus and S. epidermidis, future research into their potential role in biofilm development either independent of PIA/PNAG or in cooperation with PIA/PNAG will be of particular interest. [source] A kinetic perspective on extracellular electron transfer by anode-respiring bacteriaFEMS MICROBIOLOGY REVIEWS, Issue 1 2010César I. Torres Abstract In microbial fuel cells and electrolysis cells (MXCs), anode-respiring bacteria (ARB) oxidize organic substrates to produce electrical current. In order to develop an electrical current, ARB must transfer electrons to a solid anode through extracellular electron transfer (EET). ARB use various EET mechanisms to transfer electrons to the anode, including direct contact through outer-membrane proteins, diffusion of soluble electron shuttles, and electron transport through solid components of the extracellular biofilm matrix. In this review, we perform a novel kinetic analysis of each EET mechanism by analyzing the results available in the literature. Our goal is to evaluate how well each EET mechanism can produce a high current density (>10 A m,2) without a large anode potential loss (less than a few hundred millivolts), which are feasibility goals of MXCs. Direct contact of ARB to the anode cannot achieve high current densities due to the limited number of cells that can come in direct contact with the anode. Slow diffusive flux of electron shuttles at commonly observed concentrations limits current generation and results in high potential losses, as has been observed experimentally. Only electron transport through a solid conductive matrix can explain observations of high current densities and low anode potential losses. Thus, a study of the biological components that create a solid conductive matrix is of critical importance for understanding the function of ARB. [source] Herbivory in an acid streamFRESHWATER BIOLOGY, Issue 4 2000Mark E. Ledger Summary 1Spatial and temporal variation in the distribution and feeding of non-predatory macroinvertebrates was investigated in a first-order, acid stream in the Ashdown Forest, southern England. 2Stonefly (Nemouridae) and chironomid (Orthocladiinae) larvae were abundant on the upper surfaces of mineral substrata of three sizes (small stones, large stones, bedrock). The density of larvae in each taxonomic group did not vary among substrata of different sizes, although strong seasonal variation existed. 3Nemourids and chironomids (H. marcidus) collected from the upper surfaces of substrata exhibited generalist feeding habits, consuming algae (diatoms, coccoid and filamentous green algae), detritus (biofilm matrix material and fine particulate organic matter (FPOM)) and inorganic debris. 4There was spatial variation in the gut contents of nemourids. The proportion of algae in the guts of larvae often increased with the size of the substratum from which they were collected. Strong temporal variation in the composition of the diet also existed. Nemourids ingested a large quantity of attached algae and biofilm matrix from the biofilm in spring and winter, but consumed loose FPOM and associated microflora in summer and autumn. 5We conclude that, in this acid stream, the trophic linkage between algae and grazers is maintained by ,detritivorous' stonefly and chironomid species. The relationship between the feeding habits of these larvae and other life-history attributes, such as mouthpart morphology and mobility, is discussed. [source] Temporal Dynamics of River Biofilm in Constant Flows: A Case Study in a Riverside Laboratory FlumeINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2010Stéphanie 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] | ||||||||||