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Chapter 7
Microbial Attachments
and Biofilm Formation
introduction
The normal tendency of a microbial cell (bacteria, yeast, molds) when it comes in contact with a
solid surface is to attach itself to the surface in an effort to compete efficiently with other microbial
cells for space and the nutrient supply and to resist any unfavorable environmental conditions.
The solid surface may be comprised of a biotic, that is, biological, such as meat, fruits, etc., or
abiotic surface (nonbiological), such as floors, walls, pipes, drains, equipment, or food contact
surfaces (conveyor belts, pasteurizers, gaskets). Under suitable conditions, almost all microbial
cells can attach to a solid surface, which is achieved through their ability to produce extracellular
polysaccharides. As the cells multiply, they form a three-dimensional scaffold, forming a biofilm
on the surface containing a community of microbial cells, a polyanionic extracellular polymeric
substance (EPS), and entrapped debris. The EPS may contain polysaccharide-glycocalyx, proteins,
phospholipids, teichoic and nucleic acids, and other polymeric substances. 1 In some situations,
instead of forming a biofilm, the cells may attach to contact surfaces and other cells by thin,
threadlike exopolysaccharide materials, also called fimbriae. Biofilms are comprised of a single
species or a mixed species culture with one being dominant.
The attachment of microorganisms to solid surfaces has several implications for the overall
microbiological quality of food. Advantages of microbial attachment to and biofilm formation
on solid surfaces are to provide some protection to the cells against desiccation and a resistance
to antibiotics or biocides, ultraviolet radiation, metallic cations, and physical removal of the cells
by washing and cleaning. These cells seem to have greater resistance to sanitizers and heat. Thus,
spoilage and pathogenic microorganisms attached to food surfaces, such as carcasses, fish, meat,
and cut fruits and vegetables, cannot be easily removed by washing, and later they can multiply
and reduce the safety and quality of the foods. Similarly, microbial cells attached to equipment
surfaces, especially those that come in contact with food, may not be easily killed by chemical
sanitizers or heat designed to be effective against unattached microbial cells (like in a suspension), and thus they can contaminate food. This problem increases if cleaning and sanitation are
Chapter 7
Microbial Attachments
and Biofilm Formation
introduction
The normal tendency of a microbial cell (bacteria, yeast, molds) when it comes in contact with a
solid surface is to attach itself to the surface in an effort to compete efficiently with other microbial
cells for space and the nutrient supply and to resist any unfavorable environmental conditions.
The solid surface may be comprised of a biotic, that is, biological, such as meat, fruits, etc., or
abiotic surface (nonbiological), such as floors, walls, pipes, drains, equipment, or food contact
surfaces (conveyor belts, pasteurizers, gaskets). Under suitable conditions, almost all microbial
cells can attach to a solid surface, which is achieved through their ability to produce extracellular
polysaccharides. As the cells multiply, they form a three-dimensional scaffold, forming a biofilm
on the surface containing a community of microbial cells, a polyanionic extracellular polymeric
substance (EPS), and entrapped debris. The EPS may contain polysaccharide-glycocalyx, proteins,
phospholipids, teichoic and nucleic acids, and other polymeric substances. 1 In some situations,
instead of forming a biofilm, the cells may attach to contact surfaces and other cells by thin,
threadlike exopolysaccharide materials, also called fimbriae. Biofilms are comprised of a single
species or a mixed species culture with one being dominant.
The attachment of microorganisms to solid surfaces has several implications for the overall
microbiological quality of food. Advantages of microbial attachment to and biofilm formation
on solid surfaces are to provide some protection to the cells against desiccation and a resistance
to antibiotics or biocides, ultraviolet radiation, metallic cations, and physical removal of the cells
by washing and cleaning. These cells seem to have greater resistance to sanitizers and heat. Thus,
spoilage and pathogenic microorganisms attached to food surfaces, such as carcasses, fish, meat,
and cut fruits and vegetables, cannot be easily removed by washing, and later they can multiply
and reduce the safety and quality of the foods. Similarly, microbial cells attached to equipment
surfaces, especially those that come in contact with food, may not be easily killed by chemical
sanitizers or heat designed to be effective against unattached microbial cells (like in a suspension), and thus they can contaminate food. This problem increases if cleaning and sanitation are