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blue Which of these are considered emergent properties of biofilms? none true Cell-cell signaling A. Yes , The coordinated response of bacteria when their numbers reach some minimal concentration resulting in the regulation of significant portions of their genome through Quorum sensing molecules was not anticipated from a study of strictly planktonic cells. false Cell division (binary fission) No, Individual bacterial cells are perfectly capable of binary fission. true Complex architecture (e.g. Towers, mushrooms etc). Yes, Although some organisms like Myxococcus produce fruiting bodies normally this was thought to be unique until investigation of biofilms suggested that many, perhaps most, bacteria attached to surfaces are capable of producing complex structures when their populations reach a sufficient level. true Altruism Yes, The observation that certain bacteria with in genetically homogeneous populations may give up the ability to reproduce by forming structures (stalks) or enzymes which benefit the population as a whole may qualify to some as an altruistic act. Which of these phenomena are known to be under the control of Cell-cell signaling? none true Bioluminescence or the production of light by Vibrio fisheri in the light organs of certain marine fish. Yes, Vibrio fisheri, found in the light producing organs of certain fish and cuttlefish only produced light when a large population of bacterial cells has formed and the level of acyl homoserine lactones is high. true The formation of complex architecture in biofilms. Yes, Various laboratories have shown that mutations in the quorum sensing genes of biofilm producing organisms frequently results in major changes in biofilm structure and frequently the inability to make biofilms at all. true The synthesis of virulence factors, such as toxins, in certain pathogens. Yes, in many perhaps most pathogens that form biofilms, virulence factors are under the control of cell cell sighaling molecules such as the aHSLs. It may be that by delaying the production of virulence factors until a sufficient population of the pathogen is present the pathogen circumvents host cell defences that coule easily handle a planktonic or small biofilm population. true Multicellularity in bacteria. Yes In organisms like Myxococcus, the aggregstion of cells and the formation of fruiting bodies is under the control of quorum sensing molecules although not Acyl homoserine lactones. In gram positive organisms, the Cell Cell signals are usually short peptides. The American microbiologist Theobald Smith devised the expression P=NV/R to explain the factors which lead to pathogenicity in planktonic infection. In this expression, P = the probability of acquiring an infection, N is the number of pathogenic organisms encountered (dose), V is the virulence of the pathogen and R is the resistance of the host organisms to infection. Which of these factors are affected by the formation of biofilms by pathogenic organisms? none true Number Yes, in biofilms the number of pathogens can reach enormous numbers and though they do not invariably cause disease symptoms, in many instances they do so. In fact by growing in a biofilm the numbers can become very high without causing an immune reaction in the host. true Virulence Yes, Many virulence factors, such as extracellular matrix materials, invasive enzymes like elastase, adherance factors like pili and toxins (toxic shock syndrome toxin) are only produced when the pathogen population reaches high population density in a biofilm. true Resistance Yes, Biofilms are very difficult for host defenses to deal with. Biofilms encased in an EPS matrix are not easily detected by the host’s immune system and white blood cells have difficulty in destroying biofilms. In fact, the inflammatory response caused by the hosts immune system may cause more damage than the biofilm itself. true Probability of acquiring a disease Yes, All three of the factors mentioned, N, V and R are changed by biofilm formation is a direction which tends to increase the probability of disease. Virulence factors are genetically controlled characteristics, which increase the ability of a pathogen to cause disease. Which of the following would be considered virulence enhancing factors? none true Pili that permit the attachment of a bacterium to specific host tissue. Yes, Mechanisms of attachment are a prerequisite for the formation of biofilms. true The production of a slimy mucus which covers the biofilm. Yes, A thick EPS layer makes it difficult for host antibodies and phagocytic cells to come in contact with biofilm cells. true The production of an toxin like Endotoxin A, which may cause fever, changes in white blood cell counts, disseminated intravascular coagulation, hypotension, shock and death. Yes, Endotoxin A, a normal component of the cell walls of gram negative bacteria is a potent virulence factor. true The synthesis of an enzyme like elastase which permits the spread of the organism through host tissue. Yes, Enzymes like elastase degrade host tissue (e.g. elastin a protein found in the lung) permitting the spread of the pathogen in this tissue. Biofilms have been shown to be very resistant to antimicrobial materials like disinfectants and antibiotics. Which among the following are believed to be significant factors responsible for this resistance? none true The cells are relatively metabolically inactive (metabolically quiescent) due to nutrient limitation. These inactive cells provide few points of attack for antimicrobials. Yes, Nutrient limitation may cause cells to be quiescent and therefore relatively resistant to antimicrobials. false The biofilm matrix serves as a barrier to the diffusion of antimicrobials and thus prevents killing of biofilm cells.In biofilms genes for defensive mechanisms such as enzymes that pump antimicrobials out of the cell (efflux pumps) are up-regulated and this may protect the cells. No, The matrix of the biofilm is mostly water and is not much more of a barrier to diffusion than pure water. Except in the case of high molecular weight antibiotics, this common sense idea has been shown to be incorrect. true In biofilms genes for defensive mechanisms such as enzymes that pump antimicrobials out of the cell (efflux pumps) are up-regulated and this may protect the cells. Yes, Efflux pumps are known to be effective defensive mechanisms in many bacteria. true Some believe that some biofilm cells (Persister cells) produce proteins that inactivate critical cellular functions such as translation, transcription and DNA replication. These "toxins" force this small population of cells into a dormant state with resists killing by antimicrobials. Later, after an antimicrobial challenge, other proteins (antitoxins) may inactivate the toxins permitting growth to resume. Yes, Kim Lewis’ concept of Persister cells is gaining support in the research literature. It is important that researchers interested in biofilm formation use microbial strains of organisms that have gone through as few laboratory passages (subculturings) as possible. Why could frequent culture in the laboratory be a problem? none true In laboratory culture, cells are not subject to being washed away by the sort of flow they might encounter in a natural habitat. Yes, laboratory cultures typically are batch cultures as in a culture tube and elimination by being washed down stream in not a problem for the bacterial cell. Therefore adherence mechanisms are no longer under selective pressure and may be lost by mutation. true Bacterial cells in culture are not subject to predation. Yes, The lack of protozoa, and micro-invertebrates in laboratory culture relaxes selection pressure on bacterial cells so that genes for the production of an EPS matrix, for example, are no longer under selective pressure. true Laboratory culture with essentially unlimited nutrient availability encourages planktonic growth, not biofilm growth. Yes, Natural habitats are frequently oligotrophic, that is low in nutrients (think of streams or the water from a water treatment plant). The matrix of a biofilm has been shown to concentrate nutrients under oligotrophic conditions. In a laboratory culture with a medium containing sugars, amino acids and other rich nutrients, the formation of a matrix confers no advantage on the bacterium and may be lost due to mutation. true In laboratory culture, mutations may occur which can eliminate biofilm related functions, which are no longer being selected for (i.e. natural selection). Yes, In nature, biofilms are important to the bacterium because they confer a selective advantage (nutrition, protection, metabolic diversity, attachment). In laboratory culture these properties are not selected for and may be lost my mutation. Pseudomonas aeruginosa is an important opportunistic pathogen in burn patients, individuals with wounds and those with the hereditary disease cystic fibrosis. In forming biofilms, P. aeruginosa is known to up-regulate a number of virulence factors which increase is tendency to cause disease. Which of the following are included among these virulence factors? none true Pili and other adhesins that enable the bacterium to adhere to host tissue surfaces. Yes, The ability to attach to surface is an important early step in biofilm formation. true Slimy materials like alginate that are part of the biofilm matrix. Yes, Alginate and other components of the slimy matrix cause clogging of alveoli and bronchioles in Cystic fibrosis patients, severely limiting their lung function. true Invasins, or enzymes such as elastase that can destroy host lung tissue thus facilitating the spread of the organism. Yes, Invasins such as elastase do destroy the elastin protein component of the lung, severely compromising lung function. true Toxins or materials that interfere with normal host cell function. Yes, Toxins, like cytotoxin and hemolysins that kill host cells can contribute to the pathogenic effects of this organism. Pseudomonas aeruginosa is an opportunistic pathogen, which means that its preferred growth site is not the internal tissue of the human body. What is/are the normal habitats for this organism? none true Soil Yes, P. aeruginosa is a commonly isolated from soil. true Surfaces of plants Yes, P. aeruginosa can be a plant pathogen as well as a symbiont on plant surfaces. true As planktonic cells in fresh water Yes, P. aeruginosa can be found as free swimming cells in fresh water. true As biofilms in aquatic environments Yes, P. aeruginosa can be found in biofilms attached to surfaces in fresh water habitats. An opportunistic pathogen is one that will cause disease only in a host organism, which is compromised. Which of the following can result in a compromised host? none true Injury, either accidental or surgical. Yes, Injury, either accidental or surgical provides an opportunity for infection by Pseudomonas, Staphylococcus and other opportunistic pathogens. false A well balanced diet. No, A well balanced diet is a good way to avoid many opportunistic pathogens. Those who are malnourished are at increased risk. true Preexisting genetic disease or deformity. Yes, Some genetic diseases like Cystic fibrosis and congenital deformities like heart valve defects put people at increased risk of opportunistic infection. true Age extremes (being very young or very old) Yes, Children less than one year of age and older individuals are at increased risk of a variety of opportunistic infections such as pneumonia. The terms r-selection and K-selection describe reproductive strategies in various organisms. Which of these statements about r and K-selection are true? none false In K-selection, the emphasis is to produce as many progeny as possible as rapidly as possible. No, rapid reproduction with little parental care is a characteristic of r-selected organisms. The r here stands for the exponential rate (r) of growth in the mathematical formulas used to describe growth. true Extensive parental care is a feature of K-selection. Yes, organisms that are considered K-selected have a relatively high degree of parental care. true Organisms with an r-selected reproductive strategy are generally small, short lived and exhibit little care of their offspring. Yes, r-selected organisms are typically small, have short life spans and exhibit little parental care. true Organisms such as Humans, elephants and perhaps biofilms can be categorized as K-selected. Yes, humans, elephants and some would suggest biofilms are examples of K-selected organisms. Salmon, maple trees and perhaps bacteria growing in the planktonic mode are examples of r-selected organisms.