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blue Which of the following factors are known to affect biofilm structure. none true Hydrodynamics Yes, the flow of water past a biofilm causes shear forces that may alter the density and thickness of a biofilm and may also result in the production of streamers. true Nutrition Yes, Nutrition can have a profound effect on biofilm formation. Well fed (eutrophic) biofilms are thicker and denser than poorly fed (oligotrophic) ones. true Genotype Yes, Many mutations affecting the formation and structure of biofilms have been isolated and characterized. true Cell-Cell Signaling Yes, The formation of towers, and mushroom-shaped biofilms is under Quorum Sensing control as is the development and maintenance of the water channels permeating the biofilm. Which of the following are examples of lotic (flowing) environments? none true The surface of your teeth. Yes, the salivary glands produce from 0.71 to 1.5 liters of saliva per day, not to mention the output of gingival crevicular fluid from the tissue surrounding the roots of the teeth, making the mouth and the surface of teeth a lotic environment. true The surface of a heart valve Yes, the heart pumps approximately the entire blood volume of 5-6 liters each minute, making the heart valves a lotic environment. true The surface of a shower curtain Yes, although the curtain is exposed to water only intermittently, the water does indeed flow across the surface causing shear forces. The flow of water over a biofilm may cause: none true the production of streamers in the down stream direction. Yes, Viscoelestic streamers are a common feather of biofilms in rapidly flowing environments. true rippling of the biofilm in a down stream direction. Yes, Rippling, in which waves of biofilm are seen to move down stream have been observed. true sloughing of significant portions of a biofilm. Yes, Shear forces can cause large portions of a biofilm to detach from the substratum. true the production of a thinner, denser biofilm. Yes, High shear forces tend to make biofilms thinner, denser and more firmly attached to their substratum. Surface deficient mutants (sad) have been isolated in a number of laboratories and they have been found to affect: none true Reversible attachment Yes, sad mutants lacking flagellea were found to be less capable of attaching to the substratum. true Irreversible attachment Yes, mutants in P. aeruginosa and E. coli were unable to form the EPS matrix characteristic of wild type biofilms. true Growth and maturation Yes, Davies et al. isolated mutants unable to make QS signaling molecules that formed a flat biofilm without the complex architecture characteristic of normal Pseudomonas biofilms. treu Twitching motility Yes, O’toole and Kolter have isolated mutants lacking type IV pili that formed flat rather featureless biofilms lacking micro-colonial development and water channels.