Microorganisms attach to surfaces and develop biofilms. Biofilm-associated cells can be differentiated from their suspended counterparts by generation of an extracellular polymeric substance (EPS) matrix, reduced growth rates, and the up- and down- regulation of specific genes. Attachment is a complex process regulated by diverse characteristics of the growth medium, substratum, and cell surface. An established biofilm structure comprises microbial cells and EPS, has a defined architecture, and provides an optimal environment for the exchange of genetic material between cells. Cells may also communicate via quorum sensing, which may in turn affect biofilm processes such as detachment. Biofilms have great importance for public health because of their role in certain infectious diseases and importance in a variety of device-related infections. A greater understanding of biofilm processes should lead to novel, effective control strategies for biofilm control and a resulting improvement in patient management.

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Biofilms: microbial life on surfaces.

Microbes play key geoactive roles in the biosphere, particularly in the areas of element biotransformations and biogeochemical cycling, metal and mineral transformations, decomposition, bioweathering, and soil and sediment formation. All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and 'higher organisms', can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Microbes have a variety of properties that can effect changes in metal speciation, toxicity and mobility, as well as mineral formation or mineral dissolution or deterioration. Such mechanisms are important components of natural biogeochemical cycles for metals as well as associated elements in biomass, soil, rocks and minerals, e.g. sulfur and phosphorus, and metalloids, actinides and metal radionuclides. Apart from being important in natural biosphere processes, metal and mineral transformations can have beneficial or detrimental consequences in a human context. Bioremediation is the application of biological systems to the clean-up of organic and inorganic pollution, with bacteria and fungi being the most important organisms for reclamation, immobilization or detoxification of metallic and radionuclide pollutants. Some biominerals or metallic elements deposited by microbes have catalytic and other properties in nanoparticle, crystalline or colloidal forms, and these are relevant to the development of novel biomaterials for technological and antimicrobial purposes. On the negative side, metal and mineral transformations by microbes may result in spoilage and destruction of natural and synthetic materials, rock and mineral-based building materials (e.g. concrete), acid mine drainage and associated metal pollution, biocorrosion of metals, alloys and related substances, and adverse effects on radionuclide speciation, mobility and containment, all with immense social and economic consequences. The ubiquity and importance of microbes in biosphere processes make geomicrobiology one of the most important concepts within microbiology, and one requiring an interdisciplinary approach to define environmental and applied significance and underpin exploitation in biotechnology.

http://dzumenvis.nic.in/Physiology/pdf/Metals,%20minerals%20and%20microbes.pdf

Metals, minerals and microbes: geomicrobiology and bioremediation

Biofilms are a protected niche for microorganisms, where they are safe from antibiotic treatment and can create a source of persistent infection. Using two clinically relevant Candida albicans biofilm models formed on bioprosthetic materials, we demonstrated that biofilm formation proceeds through three distinct developmental phases. These growth phases transform adherent blastospores to well-defined cellular communities encased in a polysaccharide matrix. Fluorescence and confocal scanning laser microscopy revealed that C. albicans biofilms have a highly heterogeneous architecture composed of cellular and noncellular elements. In both models, antifungal resistance of biofilm-grown cells increased in conjunction with biofilm formation. The expression of agglutinin-like (ALS) genes, which encode a family of proteins implicated in adhesion to host surfaces, was differentially regulated between planktonic and biofilm-grown cells. The ability of C. albicans to form biofilms contrasts sharply with that of Saccharomyces cerevisiae, which adhered to bioprosthetic surfaces but failed to form a mature biofilm. The studies described here form the basis for investigations into the molecular mechanisms of Candida biofilm biology and antifungal resistance and provide the means to design novel therapies for biofilm-based infections.

Biofilm formation by the fungal pathogen Candida albicans: development, architecture, and drug resistance.

Environmental and health hazard ranking and assessment of plastic polymers based on chemical composition.

Microbial adhesion to surfaces and the consequent biofilm formation has been documented in many different environments. Biofilms constitute a protected mode of growth that allows microorganisms to survival in hostile environments, being their physiology and behavior significantly different from their planktonic counterparts. In dairy industry, biofilms may be a source of recalcitrant contaminations, causing food spoilage and are possible sources of public health problems such as outbreaks of foodborne pathogens. Biofilms are difficult to eradicate due to their resistant phenotype. However, conventional cleaning and disinfection regimens may also contribute to inefficient biofilm control and to the dissemination of resistance. Consequently, new control strategies are constantly emerging with main incidence in the use of biosolutions (enzymes, phages, interspecies interactions and antimicrobial molecules from microbial origin). The present review will focus on describing the mechanisms involved in biofilm formation and behavior, deleterious effects associated with their presence, and some of the current and emergent control strategies, providing new insight of concern for food industry.

/pdf/a-review-of-current-and-emergent-biofilm-control-strategies-ivnrpyqr4q.pdf

A review of current and emergent biofilm control strategies

Biocorrosion processes at metal surfaces are associated with microorganisms, or the products of their metabolic activities including enzymes, exopolymers, organic and inorganic acids, as well as volatile compounds such as ammonia or hydrogen sulfide. These can affect cathodic and/or anodic reactions, thus altering electrochemistry at the biofilm/metal interface. Various mechanisms of biocorrosion, reflecting the variety of physiological activities carried out by different types of microorganisms, are identified and recent insights into these mechanisms reviewed. Many modern investigations have centered on the microbially-influenced corrosion of ferrous and copper alloys and particular microorganisms of interest have been the sulfate-reducing bacteria and metal (especially manganese)-depositing bacteria. The importance of microbial consortia and the role of extracellular polymeric substances in biocorrosion are emphasized. The contribution to the study of biocorrosion of modern analytical techniques, such as atomic force microscopy, Auger electron, X-ray photoelectron and Mossbauer spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and microsensors, is discussed.

/pdf/recent-advances-in-the-study-of-biocorrosion-an-overview-3igfcziq4w.pdf

Recent advances in the study of biocorrosion: an overview

A comparative study of the major microbial biomass of biofilms on exteriors of buildings in Europe and Latin America

1. Introduction 2. Natural materials 3. Biodeterioration of refined and processed materials 4. Built environment, structures, systems and transportation 5. Investigative biodeterioration 6. The control of biodeterioration.

Introduction to biodeterioration

Concrete, stone, brick, plaster, wood, plastic, painted surfaces and metal are all colonised by bacteria, algae and fungi which accelerate theirdeterioration The mechanisms of deterioration, the main microbial genera involved and factors which may affect the degree of colonisation and attack are discussed The chief factor determining microbial growth on constructional materials is moisture Thus it is important for architects and engineers to consider critical points in the humidity profile of a building at the design stage Damp surfaces are readily colonised by microbial cells settling from the air This leads to the formation of a biofilm, which can trap dust and other particulate materials, increasing its disfiguring effect In addition, the biofilm can act as a reservoir for potentially dangerous microorganisms such as the bacteria responsible for legionnaires’ disease and allergenic fungal and actinomycete spores Materials may be protected against microbial growth by the use of biocides The use 

Deteriogenic biofilms on buildings and their control: A review

Microbial activity can have an important impact on the durability of building materials. It is important to understand this activity in order to select appropriate treatment strategies for the repair and restoration of buildings and monuments. This paper describes the microorganisms which can modify the properties of building materials such as concrete, mortars, composites, timber, gypsum, etc., as well as the mechanisms responsible for deterioration of these materials. The information provided by the members of TC 183-MIB via a questionnaire is discussed. Techniques currently utilised and areas requiring further study are identified. In addition to the references, a list of publications for further reading completes this article.

https://link.springer.com/content/pdf/10.1007/BF02480875.pdf

Christine C. Gaylarde

Papers

Recent advances in the study of biocorrosion: an overview

A comparative study of the major microbial biomass of biofilms on exteriors of buildings in Europe and Latin America

Introduction to biodeterioration

Deteriogenic biofilms on buildings and their control: A review

Microbial impact on building materials: an overview