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blue What conditions must be met in order for a conditioning film to develop? none true a Surface Yes. A surface is necessary true Water Yes. Water is necessary false Microorganisms No. Microorganisms are necessary for the formation of a biofilm, but a conditioning film will form even in a sterile environment. true Dissolved organic materials Yes. Dissolved polysaccharides, proteins, lipoproteins etc are the materials which form the conditioning film. In which of these growth curve stages are the planktonic cells most similar to cells in a biofilm? growth_curve.jpg false Lag phase No. In lag phase cells are inducing genes and producing proteins at a great rate even though they are not actively dividing. Therefore they are quite susceptible to antibiotics. false Log or exponential phase No. In log phase, cells a re growing rapidly and are quite susceptible to antibiotics and disinfectants. true Stationary phase Yes. Investigators have shown that the metabolically inactive cells of both stationary phase and biofilms are quite resistant to antibiotics and disinfectants. false Death Phase No. Most cells in biofilms are living but metabolically inactive. They are not typically dying at a great rate as they are in the planktonic culture death phase. Which of these surfaces has been shown to be resistant to colonization by biofilms? none false Silicone materials such as in urinary catheters. No. Urinary and Venous catheters are very prone to colonization by bacteria often coming from the surrounding tissues (skin or urethra). true Normal healthy human mucus membranes such as in the lungs. Yes. Normal human mucus membranes such as the bowel, are associated with compounds such as Immunoglobin A, lysozyme, and a thick mucus layer that keep bacteria away from the membrane itself. false Chromium, titanium and cobalt metal alloys such as are found in artificial hips. No. The resistance of metal alloys and various coatings used in making prosthetic joints is improving with a better understanding of biofilm development, but several percent of replacement surgeries still result in biofilm infection and require replacement. false Silver coated thread as is found in the sewing cuffs of some prosthetic heart valve replacements. No. Silver is an element with known inhibitory effects on many bacteria, but the use of this material in the threads of the sewing cuff of one artificial heart valve resulted in an increase in infection rate and death of patients. Which of the following aid bacteria in attaching to a surface? none true A preexisting conditioning film. Yes. Bacteria attach to the polysaccharides, proteins and other materials deposited on surfaces as a conditioning film. true Pili with adhesive proteins. Yes. Pili with their associated adhesin proteins may aid attachment. true Flagellae, which may aid the bacterium in crossing the hydrodynamic boundary layer. Yes. The movement caused by flagellae may help bacteria come in contact with a surface. true The weak Van der Walls forces, which may aid in bringing the bacterium close to the wall. Yes. The attractive Van der Walls forces though weak may help in bringing bacteria close to the wall. Reversible and irreversible attachment both play significant rolls in the early development of a biofilm. Indicate which of these statements about attachment are true and which are false. none true In reversible attachment many bacteria with Type IV are still capable of movement on the surface through twitching motility. Yes. Extension, attachment and retraction of Type IV pili can move bacteria across the surface of a substratum. true Irreversable attachment is associated with the increased production of a matrix composed of extra-polymeric materials (EPS). Yes. EPS production is one of the events that mark the transition from reversible to irreversible attachment. true In many bacteria like Pseudomonas aeruginosa, the twitching movement is responsible for the formation of micro-colonies and the first trace of channels. Yes. P. aeruginosa cells reversibly attached to a surface move to form aggregations or micro-colonies with spaces between which may eventually become water channels. true During irreversible attachment it has been observed that many bacterial genes are switched on or off leading to the adoption of the biofilm mode of life. Yes. Some investigators have suggested that during irreversible attachment as much or more than 30% of the bacterial genome may be up or down regulated. Biofilms grow in size and complexity by which of these? none true Bacterial cell division. Yes. Bacterial cell division varies in rate in different parts of the biofilm but does contribute to growth. true Adherence of sand and silt particles. Yes. Sand, silt and clay particles may come in contact with the growing biofilm and stick to it increasing biofilm bulk. true Attachment of additional bacteria from the passing water. Yes. Bacteria of a variety of types may become attached, adding to the mass and metabolic diversity of the biofilm. true Adherence of dead organic matter including leaf litter, chitin and other particulates that add to the bulk of the biofilm. Yes. Organic particles from the bulk fluid may adhere, adding mass and nutrients to the growing biofilm. Coaggregation is none true A process by which bacteria of different types can attach to one another increasing the diversity and metabolic complexity of a biofilm. Yes. Coaggregation can occur between members of the same genus or of widely different genera resulting in the formation of very diverse biofilms. true Is found only among the streptococci and other bacteria of the oral cavity. No. Although originally found in the mouth, coaggregation has now been documented in streams, in water treatment plants, in the human gut and the urogenital tract and in fact may be common in nature. true Often found to involve protein (lectin) carbohydrate binding and can often be prevented by adding sugars such as lactose or galactose to the bacterial mixture. Yes. Although, not true of all coaggregation interactions, many are known to involve binding between a protein on one bacterium and a carbohydrate on another, and these interactions are often preventable or reversible by the addition of certain sugars. true Is responsible for the succession of organisms that form as plaque on the teeth. Yes. There is a regular special and temporal (space and time) association in the formation of dental biofilms in which consistently certain organisms adhere first followed by other organisms in a predictable sequence. In the early 1990s, 100 people died of lung infection following the use of generic Albuterol inhalers. Which of the following are true about this tragic incident. K none true The victims of this disease outbreak were all asthmatics or individuals with other diseases affecting the lungs and/or bronchioles. Yes. Asthma is one of the primary conditions for which albuterol inhalers are prescribed. true Pseudomonas aeruginosa is a very hardy bacterium, resistant to cleaning agents and disinfectants and was not killed by the normal cleaning procedures used by the firm manufacturing the albuterol inhalers. Yes. P. aeruginosa is indeed a tough customer and is quite difficult to kill with cleaning agents and disinfectants. true Occasionally large masses of biofilm will slough off a substratum and become suspended in the bulk fluid. Yes. P. aeruginosa biofilms, like most others, has a tendency to sloughing events in which large masses of biofilm may come off the surface of the container and become suspended in the bulk fluid. In this case those fragments were packaged in the albuterol cylinders. true In order to be effective albuterol must be inhaled as deeply as possible so that it can reach the smooth muscle tissue and relieve the constriction, which is limiting airflow to the lungs. Yes. Asthmatics’ are taught to inhale the albuterol as deeply as possible so that all the constricted smooth muscle tissue can be reached. Which of these are considered to be part of the growth cycle of a typical biofilm? none true Reversible attachment Yes. In the formation of a biofilm cells from the bulk fluid first attach loosely to the substratum and they may in fact move about while attached to the surface. true Irreversible attachment Yes. At some point attached cells begin to produce a slimy matrix made of extracellular polymeric substances. At this point the cells become irreversibly attached to their substratum. true Accretion and Growth Yes. Additional cells of the same or different types may attach (accrete) to the biofilm increasing its diversity and metabolic complexity. Cells already in the biofilm may divide by binary fission and add to the growing biofilm. true Dispersal Yes. In a number of ways, cells of the biofilm may detach and be distributed through the bulk fluid. These may attach to other biofilm or attach to conditioning films elsewhere starting new biofilm micro-colonies. Which of the following are methods by which biofilms can disperse? none true Sloughing Yes. Under certain conditions, nutrient limitation for example, large pieces of the biofilm may detach from the substratum surface and be dispersed further down stream. true Erosion Yes. The shear forces applied by the moving bulk fluid may remove cells from the surface of the biofilm, which may then establish new micro-colonies down stream. true Rolling Yes. Occasionally one can observe roughly spherical masses of biofilm material rolling in the direction of stream flow. These masses maintain contact with the substratum, forming new viscoelastic connections with the surface while others up stream stretch and break. true Seeding dispersal Yes. Many investigators have observed that cells in the interior of mature biofilm micro-colonies may grow flagellae, and begin to move rapidly. Eventually the outer most layer of the micro colony is disrupted and these motile planktonic cells are released into the bulk fluid. Which of the following represents the typical sequence in the development of a biofilm? none false Conditioning film => Matrix formation and growth => irreversible attachment => reversible attachment => Dispersal No. Attachment precedes matrix formation and growth. false Conditioning film => irreversible attachment => Dispersal => reversible attachment => Matrix formation and growth No. Reversible attachment precedes irreversible attachment. false Matrix formation and growth => Conditioning film => irreversible attachment => reversible attachment => Dispersal No. The formation of the conditioning film is prerequisite for subsequent events. true Conditioning film => reversible attachment => irreversible attachment => Matrix formation and growth => Dispersal Yes. These are in the right order for a typical biofilm. Indicate whether you agree or disagree with the following comments about the addition of bacterial species to an existing biofilm. none true The addition of bacterial species to an existing biofilm may be a random event. Yes. Some new bacterial cells may contact the biofilm randomly and establish a population. true The addition of bacterial species to an existing biofilm may be highly specific. Yes. Some cells may attach by coaggregation, a process that can be highly specific. true Addition of bacterial species may increase the metabolic diversity of the biofilm Yes. Each new species carrier a unique genome and a unique set of metabolic properties. true Addition of bacterial species to an existing biofilm may increase the mass of the biofilm. Yes. The attachment of a few cells to the biofilm will not do much to increase mass, but if the cells successfully establish themselves, they may grow and contribute to the overall mass of the biofilm.