Lecture 24

Microbial life on surfaces

• Planktonic- dispersed in the liquid
• Sessile- attached to surfaces covered by liquid

• 1. Organic and inorganic compounds adsorb to and accumulate on surfaces, so surfaces often contain more nutrients for microbial growth than planktonic surfaces.
• 2. Microbial cells can attach to surfaces; by attaching, microbes can remain in a habitat favorable for reproduction
• 3. In biofilms, bacteria are protected from some toxic chemicals

• Periodontal disease and dental caries
• Otitis media (acute ear infection)
• Bacterial endocarditis (infection of inner surface of the heart and its valves)
• Cystic fibrosis (chronic disorder resulting in increased susceptibility to serious lung infections)
• Legionnaire's disease (an acute respiratory infection resulting from the aspiration of clumps of Legionnella biofilms detached from air and water heating/cooling and distribution systems)
• Nosocomial (hospital-acquired) infections- catheters, medical implants, wound dressings, tracheal inserts

• 1. Formation of organic film by adsorption of organic materials like proteins, carbohydrates
• 2. Attachment of bacteria from planktonic state, trasitioning from planktonic to sessile life style
• 3. Growth and division of bacteria
• 4. Exopolymer production and biofilm formation
• 5. Detachment and dispersal- release of motile cells, detachment of clumps, or migration under shear

Forms a matrix, usually composed of polysaccharide, but can also contain protein and nucleic acids

• Two stages of illness
• 1. Intermittent respiratory infections, like bronchitis, involving Staphylococcus aureuss, Haemophilus infulenzae, P. aeruginosa
• 2. Development of a permanent chronic infection with P. aeruginosa