Hilary M. Lappin-Scott

Bacterial biofilms and surface fouling

Bacteria are attracted to surfaces. Their surface adhesion, with subsequent binary fission and exopolymer production, leads to the formation of biofilms. Such biofilms consist of bacterial cells in a matrix of their own exopolysaccharide glycocalyces. In addition to the bulk fluid and the surface, biofilms constitute a third physical phase. The close proximity of the bacterial cells in the biofilm matrices assists the formation of metabolically dependent consortia. The chemical and physical activities of these microbial communities produces a heterogeneous system at the colonised surface. Metabolites, produced at specific points on the surface, can lead to the development of effective anodes and cathodes at adjoining locations on the surface. In this way the fouling of a surface by bacterial biofilm development facilitates focal attack on that surface. This pit formation is characteristic of bacterial surface activities as diverse as dental decay and metal corrosion. In this review, we examine bacterial a...

Enhanced oil recovery - three-dimensional sandpack simulation of ultramicrobacteria resuscitation in reservoir formation

Summary: Changes in cell size and shape associated with bacterial starvation and resuscitation were used as a technique to enhance oil recovery. Injection of starved bacteria followed by nutrients into rock cores produced deep bacterial plugs. This work reports on an investigation of the dispersion and resuscitation of ultramicrobacteria (UMB) produced by starvation of Pseudomonas sp. FC3. Initially, the UMB were injected into one-dimensional sandcores; in other words, flow was from the inlet to the outlet in one direction. To provide closer simulation of oil well conditions, the UMB were injected into a three-dimensional reservoir simulator, 45 cm in diameter by 38 cm in length. Sample probes strategically positioned within the sandpack detected the UMB as they dispersed throughout the pack. After 24 d of nutrient stimulation, the sandpack was dismantled and analysed. Scanning electron microscopy and carbohydrate assays of the sandpack sections showed glycocalyx (polymer) production in every section. The three-dimensional model confirmed the findings of the unidirectional core models in that the UMB penetrated the sandpack, resuscitated and grew in situ to form a confluent bacterial plug when nutrient-stimulated.

Advances in microbiology to enhance oil recovery

Microbial experiments to study enhanced oil recovery have generally been conducted using vegetative microorganisms and one-dimensional laboratory models. With the financial support of the Alberta Oil Sands Technology and Research Authority (AOSTRA), we have developed a procedure utilizing microorganisms called ultramicrobacteria (UMB) to assist in oil recovery by virtue of their growth properties. UMB or starved bacteria (.2–.3 /μm) have the ability to penetrate deep into model rock cores and respond to nutrient stimulation by effectively plugging these matrices by cell growth and polymer production. Vegetative cells or full-size cells tend to form “skin plugs” at or near the well bore. Initial UMB core studies in 5-cm and 10-cm sandstone cores were one-dimensional with unidirectional flow. To simulate reservoir conditions, UMB experiments were conducted in a pressure vessel, 45 cm in diameter x28 cm in height. In the first experiment a homogeneous sandpack was used, in the second a heterogeneous sandpack was used. Our experiments to date have shown (1) penetration of UMB, resuscitation upon nutrient stimulation, and reduction in permeability in homogeneous sand packs and (2) that resuscitated UMB preferentially plug the high-permeability zone by virtue of their growth properties and extracellular polysaccharide (polymer) production.

Effects of biocide treatment and backflow pressure on the permeability of microbially fouled model cores

SummarySintered glass bead cores were plugged until the permeability was reduced to 1% or less of the original permeability by the injection of a slime-producing bacterium isolated from produced water. Scanning electron microscopy of fractured core sections showed that the bacteria were predominantly located in the uppermost sections, around the core inlet. Killing the bacterial cells in the plugging biofilm, using a biocide, had little effect on core permeability. The dead cells were only removed when backflow pressure, simulated by inversion of the test core followed by fluid injection, was applied and maintained at 55–69 kPa. Backflow of plugged cores containing live bacteria produced transient pressure-dependent increases in permeability that were proportional to the backflow pressure applied. We conclude that only sustained backflow procedures reduced permeability: such operations are not effective for oil recovery in field conditions.

Microbial Biofilms: List of Contributors

Biofilm formation constitutes an alternative lifestyle in which microorganisms adopt a multicellular behavior that facilitates and/or prolongs survival in diverse environmental niches. Biofilms form on biotic and abiotic surfaces both in the environment and in the healthcare setting. In hospital wards, the formation of biofilms on vents and medical equipment enables pathogens to persist as reservoirs that can readily spread to patients. Inside the host, biofilms allow pathogens to subvert innate immune defenses and are thus associated with long-term persistence. This review describes the process of biofilm formation its composition and

Microbial Biofilms: Biofilms and Inert Surfaces

Biofilm formation constitutes an alternative lifestyle in which microorganisms adopt a multicellular behavior that facilitates and/or prolongs survival in diverse environmental niches. Biofilms form on biotic and abiotic surfaces both in the environment and in the healthcare setting. In hospital wards, the formation of biofilms on vents and medical equipment enables pathogens to persist as reservoirs that can readily spread to patients. Inside the host, biofilms allow pathogens to subvert innate immune defenses and are thus associated with long-term persistence. This review describes the process of biofilm formation its composition and

Microbial Biofilms: Structure, Physiology and Ecology of Biofilms

Biofilm formation constitutes an alternative lifestyle in which microorganisms adopt a multicellular behavior that facilitates and/or prolongs survival in diverse environmental niches. Biofilms form on biotic and abiotic surfaces both in the environment and in the healthcare setting. In hospital wards, the formation of biofilms on vents and medical equipment enables pathogens to persist as reservoirs that can readily spread to patients. Inside the host, biofilms allow pathogens to subvert innate immune defenses and are thus associated with long-term persistence. This review describes the process of biofilm formation its composition and

Microbial Biofilms: Frontmatter

Biofilm formation constitutes an alternative lifestyle in which microorganisms adopt a multicellular behavior that facilitates and/or prolongs survival in diverse environmental niches. Biofilms form on biotic and abiotic surfaces both in the environment and in the healthcare setting. In hospital wards, the formation of biofilms on vents and medical equipment enables pathogens to persist as reservoirs that can readily spread to patients. Inside the host, biofilms allow pathogens to subvert innate immune defenses and are thus associated with long-term persistence. This review describes the process of biofilm formation its composition and