Molecular Ecology of Biofilms Chapter Abstracts
Chapter 1
An Overview of Biofilm Molecular Ecology
Robert J.C. McLean
Abstract
Biofilms, polysaccharide-encased, surface-adherent microbial communities, are widespread in nature. The physiology of planktonic and biofilm organisms differs significantly, most notably with respect to the low susceptibility of biofilm organisms to antibiotics and disinfectants. Current estimates of differential gene expression in single species biofilms and planktonic bacteria by subtractive hybridization, in vivo expression technology, phage mutagenesis, transcriptional profiling (genomics), and proteomics, range from a few genes to several hundred genes. The close association of organisms within biofilms facilitates metabolic interactions, signaling, and genetic exchange. Quorum signaling, a function of microbial population density, has been shown to be important in microbial interactions in single species and mixed population biofilms as well as in biofilm interactions with higher organisms. Undoubtedly future work will show additional signals and genes to be important in mixed culture biofilms.
Chapter 2
Role of Exopolysaccharide in Biofilm Matrix Formation: The Alginate Paradigm
Kalai Mathee, Arsalan Kharazmi and Niels Høiby
Abstract
Pseudomonas aeruginosa is ubiquitous in nature and it is also an important opportunistic pathogen that threatens the lives of compromised humans. In a certain ecological niche it produces a surface slime polysaccharide called alginate that is presumed to contribute to its biofilm mode of growth. The natural mode of microbial growth is as organized biofilm communities on surfaces. The individual cells and communities are held together by a matrix that is made up of exopolysaccharide (EPS) which provides a unique environmental niche. The polysaccharides may occur as thin microsapsular coats or thick capsular polysaccharide as seen in Pseudomonas species. P. aeruginosa has emerged as a model organism to study the role of EPS, in particular alginate, in biofilm formation. This is due to the fact that the complex genetics of alginate production in planktonic form has been worked out in great details. We will provide a comprehensive overview of alginate genetics and regulation and address the possible role alginate in biofilm matrix formation.
Chapter 3
Regulatory Events in Biofilm Development
David G. Davies
Abstract
Basic questions regarding the biology behind biofilm development are addressed. The development of bacterial biofilm communities as a physiologically regulated process is examined and key molecular events in several laboratory-grown biofilms are considered. The stages in biofilm development that are addressed include: transport to a surface, reversible attachment, irreversible attachment, maturation, cell-to-cell communication and detachment. Each stage of development is examined at the molecular scale with particular attention to regulatory processes.
Chapter 4
Biofilm Interactions with Marine Invertebrates
Alan W. Decho
Abstract
Associations of bacteria with marine invertebrates occur using a variety of different interactions. These range from innocuous commensal attachments, to closely-regulated symbioses, to harmful pathogenic invasions, and influence both the ecology and physiology of the invertebrates. Bacteria also affect invertebrates indirectly, through mediation of larval settlement processes and by influencing trophic (feeding) interactions. Owing to the attached nature of bacteria, biofilms are closely involved in many of these associations. While other aspects of microbial-invertebrate associations have been closely studied, biofilm processes involved in these associations are poorly understood in most cases. This review addresses the nature of biofilm processes in microbial-invertebrate associations.
Chapter 5
Endolithic Microbial Communities as Bacterial Biofilms, the Role of EPS
Harry D. Kurtz, Jr.
Abstract
Endolithic microbial communities are found worldwide and are intimately involved with the global geochemical cycles. In order to enhance our understanding of these microbial communities, it is necessary to apply our knowledge of bacterial biofilms to these ecosystems. Endolithic microbes grow as cells attached to a surface that is at least intermittently in contact with water. These communities also produce extracellular polymeric substances (EPS) that are involved in stabilizing sandstone surfaces of a wind-abraded groove. Endolithic microbial habitats have several features in common with aeolian and aquatic sedimentary systemsnamely the potential for movement of the substratum. Thus, comparisons of these systems to endolithic habitats will allow us to deduce that the major function for EPS is to stabilize the local environment. From an evolutionary standpoint, this role would allow communities to remain in an environment conducive to the growth and reproduction of the members in the consortium. Additional functions attributed to EPS are likely secondary to the stabilization provided by the material.
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