The Effect of the Growth Medium on the Composition and Metal Binding Behaviour of the Extracellular Polymeric Material of a Metal-Accumulating<i>Citrobacter</i>sp.

Bonthrone, Karen M.; Quarmby, J.; Hewitt, Christopher J.; Allan, Victoria J. M.; Paterson-Beedle, Marion; Kennedy, J. F.; Macaskie, L. E.

doi:10.1080/09593330.2000.9618893

Cited by 36 publications

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“…This is not surprising, since previous reports showed that calcium plays a role in the cohesiveness of microbial aggregates and biofilms (12,20). It is known that microbial cells in biofilms produce EPS mostly composed of polysaccharides, proteins, and nucleic acids, which forms a protective gel-like matrix around cells (9,26,44). The EPS interactions with surrounding material and the substrata involve salt bridges between cations within the matrix and the anionic functional groups of the exopolymers (e.g., the carboxyl, phosphate, sulfate, glycerate, pyruvate, and succinate groups).…”

Section: Discussionmentioning

confidence: 80%

Biofilm Cohesiveness Measurement Using a Novel Atomic Force Microscopy Methodology

Ahimou¹,

Semmens²,

Novak³

et al. 2007

Appl Environ Microbiol

113

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Biofilms can be undesirable, as in those covering medical implants, and beneficial, such as when they are used for waste treatment. Because cohesive strength is a primary factor affecting the balance between growth and detachment, its quantification is essential in understanding, predicting, and modeling biofilm development. In this study, we developed a novel atomic force microscopy (AFM) method for reproducibly measuring, in situ, the cohesive energy levels of moist 1-day biofilms. The biofilm was grown from an undefined mixed culture taken from activated sludge. The volume of biofilm displaced and the corresponding frictional energy dissipated were determined as a function of biofilm depth, resulting in the calculation of the cohesive energy. Our results showed that cohesive energy increased with biofilm depth, from 0.10 ؎ 0.07 nJ/m 3 to 2.05 ؎ 0.62 nJ/m 3 . This observation was reproducible, with four different biofilms showing the same behavior. Cohesive energy also increased from 0.10 ؎ 0.07 nJ/m 3 to 1.98 ؎ 0.34 nJ/m 3 when calcium (10 mM) was added to the reactor during biofilm cultivation. These results agree with previous reports on calcium increasing the cohesiveness of biofilms. This AFM-based technique can be performed with available off-the-shelf instrumentation. It could therefore be widely used to examine biofilm cohesion under a variety of conditions.It is essential to understand biofilm stability to both encourage biofilm maintenance in some applications, such as waste treatment, and effectively remove undesired biofilm in others, as in biofilms covering medical implants. Biofilm detachment is one of the critical factors that balance growth and plays a role in the development of biofilm spatial heterogeneity. While factors responsible for biofilm growth are well studied (16,29,39,42,43), those controlling the detachment process are not clearly understood (28,36,38). As a consequence, a good understanding of the relationships between operating conditions and biofilm cohesion is lacking. The cohesive strength of the biofilm is influenced by extracellular polymeric substances (EPS) and specific compounds, such as calcium, which fill the space between microbial cells and bind cells together (23,30). Understanding the cohesive interactions in the biofilm matrix under a variety of conditions could lead to the design of new strategies for controlling biofilm development based on disrupting or protecting the matrix holding the biofilm together.Because cohesive strength is a primary factor affecting biofilm sloughing, its quantification is essential in understanding detachment. A few methods based on the use of custom devices have been proposed to investigate biofilm cohesive strength. Poppele and Hozalski (31) measured the tensile strength levels of biofilms from activated sludge by using a micromechanical device based on the deflection of a glass micropipette separating a microbial aggregate held by suction. Körstgens et al. (22) used a uniaxial compression measurement device to determine the yield st...

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Section: Discussionmentioning

confidence: 80%

Biofilm Cohesiveness Measurement Using a Novel Atomic Force Microscopy Methodology

Ahimou¹,

Semmens²,

Novak³

et al. 2007

Appl Environ Microbiol

113

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“…Tait et al (1986) observed that high C : N and C : P ratios in the medium were associated with high levels of polymer production. However, no difference was found between the amount of polymer extracted from planktonic cells in the culture outflow in the three media (extraction and quantitation methods were as described by Bonthrone et al, 2000). Hence, there is probably no association between the level of EPS production and the extent of biofilm formation by this strain (but note that there was insufficient biofilm for comparison of EPS of attached cells).…”

Section: Time (H) Mean Depth (µM) Maximum Depth (µM) Minimum Depth (µM)mentioning

confidence: 99%

“…Phosphatase specific activity was measured by the release of p-nitrophenol (PNP) from pnitrophenyl phosphate as described previously (Macaskie et al, 1995Jeong et al, 1997 ;Finlay et al, 1999 ;Bonthrone et al, 2000). One unit is defined as 1 nmol PNP released min − " (mg bacterial protein) − " with the protein concentration measured using the CuSO % \bicinchoninic acid method (Sigma protein test kit TPR0562) and bovine serum albumin as the standard.…”

Section: Methodsmentioning

confidence: 99%

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Effect of nutrient limitation on biofilm formation and phosphatase activity of a Citrobacter sp.

et al. 2002

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A phosphatase-overproducing Citrobacter sp. (NCIMB 40259) was grown in an air-lift reactor in steady-state continuous culture under limitation of carbon, phosphorus or nitrogen. Substantial biofilm formation, and the highest phosphatase activity, were observed under lactose limitation. However, the total amount of biofilm wet biomass and the phosphatase specific activity were reduced in phosphorus-or nitrogen-limited cultures or when glucose was substituted for lactose as the limiting carbon source. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM) showed differences in cell and biofilm morphology in relation to medium composition. Electron microscopy suggested that the differences in biofilm formation may relate to differential expression of fimbriae on the cell surface.

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“…Under these conditions, it has been demonstrated that the surface hydrophobicity and thus the morphology of the two systems can change markedly (Sanin et al, 2003). Considering the importance of aggregate quality on process performance, and those reports that an increase in mean energy dissipation rate (agitation intensity, Hewitt et al, 1998) and nutrient availability (Bonthrone et al, 2000) can effect the quantity and quality of ECP production, such parameters require further study. Indeed detailed knowledge about which factors enhance cell immobilization and effect cell physiological state within the aggregate (i.e., aggregate quality) is needed.…”

Section: Introductionmentioning

confidence: 96%

The use of multi‐parameter flow cytometry to study the impact of limiting substrate, agitation intensity, and dilution rate on cell aggregation during Bacillus licheniformis CCMI 1034 aerobic continuous culture fermentations

Silva

Reis

Kent

et al. 2005

Biotech & Bioengineering

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The main objective of this work was to establish those factors either physical (power input) or chemical (limiting substrate or dilution rate) that enhance cell aggregation (biofilm or floc formation) and cell physiological state during aerobic continuous cultures of Bacillus licheniformis. Glucose-limited steady-state continuous cultures growing at a dilution rate between 0.64 and 0.87/h and 1,000 rpm (mean specific energy dissipation rate (epsilonT) = 6.5 W/kg), led to the formation of a thin biofilm on the vessel wall characterized by the presence of a high proportion of healthy cells in the broth (after aggregate disruption by sonication) defined as having intact polarized cytoplasmic membranes. An increased epsilonT (from 6.5 W/kg to 38 W/kg) was found to hinder cell aggregation under carbon limitation. The carbon recovery calculated from glucose indicated that additional extracellular polymer was being produced at dilution rates >0.87/h. B. licheniformis growth under nitrogen limitation led to floc formation which increased in size with dilution rate. Counter-intuitively the flocs became more substantial with an increase in epsilonT from 6.5 W/kg to 38 W/kg under nitrogen limitation. Indeed the best culture conditions for enhanced metabolically active cell aggregate formation was under nitrogen limitation at epsilonT = 6.5 W/kg (leading to floc formation), and under carbon limitation at a dilution rate of between 0.64 and 0.87/h, at epsilonT = 6.5 W/kg (leading to vessel wall biofilm formation). This information could be used to optimize culture conditions for improved cell aggregation and hence biomass separation, during thermophilic aerobic bioremediation processes.

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The Effect of the Growth Medium on the Composition and Metal Binding Behaviour of the Extracellular Polymeric Material of a Metal-AccumulatingCitrobactersp.

Cited by 36 publications

References 0 publications

Biofilm Cohesiveness Measurement Using a Novel Atomic Force Microscopy Methodology

Biofilm Cohesiveness Measurement Using a Novel Atomic Force Microscopy Methodology

Effect of nutrient limitation on biofilm formation and phosphatase activity of a Citrobacter sp.

The use of multi‐parameter flow cytometry to study the impact of limiting substrate, agitation intensity, and dilution rate on cell aggregation during Bacillus licheniformis CCMI 1034 aerobic continuous culture fermentations

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