Chapter 6 Homework 1 The primary difference between organotrophs and lithotrophs is a Organotrophs assimilate electrons from organic sources while lithotrophs assimilate electrons from inorganic sources 2 An organotrophs is an organism that a Uses organic molecules as a source of electrons 3 Although phototrophic organisms can grow in nutrient poor habitats growth is normally slow a Synthesis of materials in necessary for metabolism takes time under nutrient poor 4 If the goal is to estimate the number of bacteria in a broth sample the most appropriate separation technique would be the because conditions a Pour plate 5 On a streak plate preparation of a pure culture colonies were found along the streak line as well as below the surface of the agar What is a reasonable conclusion for this observation a The agar plate was contaminated before inoculation by the streaker 10 In a typical bacterial growth curve both the growth phase and the death phase are exponential 6 An advantage of using rRNA to identify bacteria is a Cells don t have to be cultured first 7 Ultraviolet radiation controls the growth of microbes by a Damaging DNA 8 Autotrophs assimilate carbon from inorganic sources like CO2 9 Organotrophs acquire electrons from organic molecules a True a True a True a False 11 Pasteurized milk is sterile such as human skin a True 12 An antiseptic is a chemical that kills infectious microbes and is safe enough to be used on tissues 13 Why does growing in a salty environment pose a challenge a Salty environments pose a challenge to cellular life both because of the osmotic stress I places on the cell in a salty environment we would expect much of the water in the cell to escape to the outside 14 Select the incorrect statement a Complex media are derived in part from components where the specific concentrations of each nutrient are unknown b Examples of complex media include media formulated from crude yeast or animal beef or brain extracts In defined media the chemical identity and concentration of all components are known c d In defined media yeast animal and plant tissue is present 15 Unculturable microorganisms can be characterized by determining the types of bacteria present in a sample by a Isolating DNA from all cells and amplifying and sequencing the 16S ribosomal DNA 16 The basic nutritional need s for microbes is are a Sources for carbon electrons and energy 17 The large intestine is likely inhabited by a Facultative anaerobes 18 Colonies visible on an agar plate are a Clones the result of repeated cell division starting with a single cell 19 Nutrient broth is composed of beer extract and peptone As a result nutrient broth is considered a not precisely known a Enriched medium a Complex medium because the chemical compositions of beef extract and peptone are 20 Culturing a fastidious organism in the laboratory would most likely require a 21 A broth culture was diluted 10 fold 0 1 ml was spread onto an agar plate and 47 colonies were counted What is the estimated cell concentration in the original broth culture a 4 700 cells ml 22 Alcohol works as a disinfectant by a Dissolving and disrupting cell membranes 23 The most effective way to sterilize most bacterial media is by 24 The generation time is the average time interval from one cell division to the next a Autoclaving a True 25