General Microbiology MCB 3020C
University of Central Florida
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Date Created: 10/22/15
Chapter 5 Growth orderly increase of all major chemical constituents of an organism If total mall is increased doesn t mean its growth weight might be due to reserve material Grown results in cellular multiplication except in case of coenocytic multinucleatd organism Cell Growth depends on large number of chemical reactions Metabolism C5 Cell mass is continuous whereas cell division is discontinuous Fueling transform energy Biosynthesis synthesizing small molecules building blocks coenzymes vitamins Polymerization reactions make up macromolecules Synthesized products are assembled into cell structures and cell grows and then divides Binary Fission most common way of unicellular reproduction Cell divides into 2 new cells Grows twice in length and forms a Septum partition that separates the cell into 2 daughter cells forms due to inward growth of cytoplasmic membrane and cell wall from opposite directions Divisome Fts filamentous temperature sensitive proteins are essential for cell division If a mutation in genes occurs that encode Fts it causes cells to not divide normallylong filamentous cells that fail to divide o FtsZ ring forms around center of cell 0 FtsZ Ring shows where the cell dividion will occur 0 ZipA is an anchor that connects FtsZ ring to cytoplasmic membrane FtsA is a protein relacted to actin and it helps in connecting the ring also 0 FtsI proteins needed for peptidoglycan synthesis penicillin binding proteins blocked by penicillin DNA replicated before FtsZ ring forms Min CD proteins make sure the divisome forms only at cell center and not poles MinE directs formation of ring and divisome FtsK pulls 2 daughter cells apart and the ring depolymerizes septum forms FtsZ hydrolyzes GTPguanosine triphosphate hydrolysis provides energy to fuel polymerization Caulobacter crescentus produces a shape determining protein called crescentin in addition to MreB a Cytoskeleton protein which is a major shape determining factor in prokaryotes coils through long axis of cell touching cell membrane at sites of cell wall synthesis Default shape for bacteria is cocci Peptidoglycan Synthesis 0 Autolysins make opening in wall so peptidoglycan is cut and new peptidoglycan muramic acidglucosaminetetrapeptide units precursors are brought in at the same time o The cell wall is outside cell membrane so the precursors are brought through the cell membrane by Bactoprenol C55 by making them hydrophobic to get them through the membrane Glycolase forms glycosidic bonds after interacting with bactoprenol C55 0 Transpeptidation forms peptide crosslinks between muramic acid Inhibited by penicillin when its inhibited the autolysins will keep making openings in cell wall until its very weak and osmotic lysis will occur FtsI is key protein in transpeptidation for E coli Yeast reproduce by budding type of division which results in unequal distribution of cellular material Also divide by binary fission equal distribution of cellular material Bacterial Growth Curve 0 Exponential growth is characteristic of microbial populations but doesn t continue for long periods of time o Lag Phase doesn t always occur in growth of a bacterial population Metabolically very active even if its at Will happen if microbial population from old broth is put into new broth cells must have enzymes to synthesize metabolites not present in the medium Put cells from another phase into a fresh medium with different chemical composition Wont occur if cells in the exponential phase are put into a medium with same chemical composition Biphasic Growth remember glucose and lactose example with graph k 0 o Exponential or Log Phase cant continue indefinitely limited k max o Stationary Phase no increase in cell number or cell mass Will occur because 1 Essential nutrient for growth is used up 2 Waste product inhibits growth oforganism k 0 0 Death Phase death exponential but slower than the growth exponential rate When cells don t have nutrients needed they begin to die k o Lag Phase Exponential Phase Stationary Phase and Death Phase do not apply to individual cells but apply to populations of cells Growth Rate change in cell number or cell mass per unit of time Every time a cell divides and makes 2 cells its called generation or doublings Turbitidy Spectrophotometer measures light passing through a solution Nepholometer measures scattered light Beer Lambert Law 0 Absorbance equals 2logT Absorbance is directly proportional to concentration Absorbance is equal to the molar extinction coefficient x the concentration is moles per 1cm light path 0 Absorbance equals log T o A T of 1 equals an absorbance of1 Growth is effected by physical environment chemical environment change in environment that alters morphological or physiological characteristics of the organism conditions that govern growth 0 Physical environment factors Temperature Hydrostatic Pressure Osmotic Pressure Surface Tension Visible Radiation UV Radiation Gravity Absorption phenomena Viscosity 0 Chemical environment factors Water activity aw water structure pH inorganic nutrients quantity and quality gasses quality and quantity organic nutrients quantity and quality Sterliziation treatment which frees objects of ALL living organisms including endospores OO Death is the irreversible loss of ability to reproduce Temperature Higher temp makes chemical and enzymatic reactions increase and growth becomes faster But if temp is too high proteins will be damaged irreversibly 0 Minimum Temperature below which no growth occurs Membrane gelling transport processes are so slow that growth doesn t occur 0 Optimum Temperature which growth is most rapid always nearer to max temp than minimum Enzymatic reactions occur at maximal possible rate and increasingly rapid rates 0 Maximum Temperature above which grown is not possible Proteins denature collapse of cell membrane thermal lysis 0 These 3 temperatures are called Cardinal Temperatures Psychrophile optimum of 15 C Mesophiles optimum above 15 to 40 C Thermophiles optimum exceeds 45 C o Hyperthermophiles above 80 C for optimum Halophiles require salt for growth 0 Extreme Halophile very salty environment Osmophiles live in enviroment with high sugar Xerophile live in very dry environments Osmotic Pressure aw is always less than or equal to 1 Compatible Solutions solute used inside cell for admjustment of cytoplasmic water activity must be noninhibitory as concentration of solute in solution increases plasmolysis occurs As concentration of salt increases aW gets smaller Oxygen Classes 0 Aerobes species capable of growth at full oxygen tension air is 21 Oz and many can tolerate elevated concentrations of oxygen hyperbaric oxygen Obligate Aerobes require oxygen for growth Microaerophiles can use oxygen at low levels from that in air might have oxygen sensitive molecule or capacity to respire Facultative Aerobes aerobes that under appropriate nutrient and culture conditions can grow under either aerobic or anaerobic conditions Oxygen not required but grows better with it Anaerobes Organisms that cannot respire oxygen Aerotolerant Anaerobes can tolerate oxygen and grow in its presence even though they cannot use it Don t need oxygen and don t grow better when its present 0 Obligate strict Anaerobes inhibited or even killed by oxygen 0 Toxic Oxygens Superoxide Hydrogen Peroxide Hydroxyl Radical Enzymes o Obligate and Facultative erobes typicall have both catalase and Superoxidase Dismutase SOD Aerotolerant anaerobes typically lack catalse but have SOD Obligate Anaerobes lack both like Clostridia methanobacteria ruminococci OO O OO 00 MCB 3020 LAB Test Fall 2001 Name 50 questions wonh 2 points each assume pink and red are synonymous for quiz 1 What adjusts the diameter of the cone of light so that it just lls the objective lens C a condenser b Abbe condencer c iris diaphragm d ne adjustment e course adjustment N O 3 write both correct answers BD a has the same refractive index as air b has approximately the same refractive index as glass c is used with the high dry lens d lessens the bending of light rays away from objective lens e has same numerical aperture as air 9 When transferring a loopful from a culture tube to the slide after aming the loop the cap of tube is removed C and placed open side down on lab bench and placed open side up on lab bench and held using the small finger of the hand holding the inoculating loop and held in the hand holding the culture tube either a or b rue99 s 5 Mycobacterium tuberculosis in an acid fast staining procedure C a stains as bright blue rods b is rapidly decolorized with acid alcohol c has a high wax content wall that resists decolorization amp retains the carbol fuschin dye d is stained by the counterstain e stains with crystal violet V39 A rod shaped acid fast negative bacterium B a stains as bright pinkviolet rods b is rapidly decolorized with acid alcohol c has a high wax content wall d resists decolorization and stains with methylene blue e ac 6 The contrast improves when B a you use a higher power lens for the objective b the iris diaphragm is closed down some but not completely the condencer is dropped down cells are observed in a wet mount ad 9amp0 7 Heat xation B is not necessary for the spore stain causes proteins and nucleic acids to denature causes the polysaccharides to precipitate and makes cells stick to slide occurs before air drying makes cells wash off easier after staining rap96x 8 The function of iodine in gram stain Write two correct answers BD a decolorizer b forms complex with crystal violet c counterstain d mordant e removes crystal violet 9 If the wavelength of light is decreased what effect does this have on resolution E makes resolution worse b gives a better resolution c does not change resolution d makes the diameter of the smallest resolvable object smaller e bd E 10 Which of the following anaerobic structures or cells would stain green with heated Malachite green and retain that dye D a spore ofBacz39llus sporangium of Bacillus endospores of Staphylococcus endospores of Clostridium sporangium of Clostridium 0905 11 Negative staining E stains the background uses anionic or insoluble dyes requires the preparation of an air dried heat fixed smear ac ab rap96x 13 What color would the free spore or mature endospore be in a gram s stain D a blue b pink or red c green d colorless e black 14 In what type of microscopy does the condenser direct light at oblique angles away from lens so that object in the field must scatter the light into the lens to appear white B a negative stain in bright field microscopy b dark field microscopy c bright field microscopy d a c 15 What color would a gram negative be if the gram stain procedure was stopped after the addition of iodine A a purple b green c colorless d pink e brown 16 An anionic dye D a has a positive charge on the colored portion b is attracted to the negatively charged anode c is attracted to the positively charged cathode d has a negative charge on the colored portion e ab cd cd 17 The nosepiece lens is called D a lamp b iris c ocular d objective e condensor 18 Cocci growing in clusters are called E a sarcinate b tetracocci c diplococci d streptococci e staphylococci 19 Ifthe total magni cation of an object on the microscopic slide using a 45X high dry objective lens is 270K what is the power or magni cation of the eyepiece lens B a 10X b 6X c 45 X 240 d 5X e 100K 20 A microscope with the same light source but with an objective lens of numerical aperature has the best resolution A a 18 b 16 c 14 d 125 e 075 21As the magni cation property of a lens increases A a the working distance decreases b the light scattering effects become less important c the numerical aperature decreases d the working distance increases e bd 22 In dark eld microscopy C a the object appears dark on a white eld b the light from the condenser goes directly toward the objective lens c the light that is scattered by the object enters the objective lens d a negative stain is used to give a dark background e bd 23 A green color and partial clearing of blood agar is called D a alpha oxidation b beta hemolysis c gamma hemolysis d alpha hemolysis e beta oxidation 24 Which of the following are true about Escherichia on EMBW139ite all c01TectAB a green metallic sheen in re ected light b lactose fermentor c pale pink to lavender with dark center d non lactose fermentor e dark red colonies 25 A white colony on Desoxycholate is most likely D a a gram b a lac gram c a gram lac d a gram lac e a gram negative 26 In which medium do fermentors produce acid to precipitate the bile salts and absorb the red dye C a EMBeosin methylene blue agar b PEAphenyl ethanol agar c DESdesoxycholate agar d Blood Agar e Motility Medium 27 Which of the following gives the best resolution B a wavelength 200nm Numerical aperture 08 b wavelength 200nm Numerical aperture 10 c wavelength 400nm Numerical aperture 10 d wavelength 400nm Numerical aperture 08 e wavelength 300 Numerical aperture l0 28 Nitrate I and Nitrate II are added to an inoculated and incubated nitrate broth tube and no color occurs Zn is added and the tube turns red B for N0339 nitrate reduction to NOz39 nitrite test for nitrate reduction test for nitrate oxidation to gaseous end products test for nitrate oxidation to N20 test for nitrate reduction to N2 or NH3 gases rap96x 29 Which product produced by urease breakdown of urea makes the medium turn alkaline a carbon dioxide C02 urea ammonia NH3 amino acids lactate 0 b c d e 30 Which genus gives a positive urease test C a Escherichia b Enterobacter c Proteus d Alcaligenes e Pseudomonas 3 l The methyl red test is positive B a if the indicator turns from red to yellow b if the acids produced from fermentation of glucose drops pH below 51 c if the acids produced drop the pH in 24 hours to 60 d for 23 butanediol fermentors e a d 32 The addition of iodine to an inculated medium turns the medium a blueblack color throughout The microorganism is D a positive for milk hydrolysis b negative for casein hydrolysis c positive for starch hydrolysis d negative for amylase e positive for lipase 33 The reagents sulfanilic acid and dimethyl alphanapthylamine test for the presence of what product C a NH3 b NO39 c N02quot d N0339 e N20 34 A positive Simmon s citrate test E a is indicated by no growth b is a green color c means the bacterium biosynthesizes citrate d means that the bacterium makes no citric acid in its Krebb s cycle e means that the bacterium uses citrate as its only carbon source 35 A yellow color in a Phenol Red Glucose tube with the inverted vial containing no liquid B a Acid b Acid amp Gas c alkaline b a mannitol fermentor e negative for glucose fermentation 36 A milk agar plate has growth with a zone of clearing around the growth Which statement is correct B the microorganism has an amylase the microorganism has an extracellular caseinase an intracellular enzyme breaks down the milk protein the test is negative for starch hydrolysis the microorganism has a lactase that breaks down the lactose in the milk snow 37 A pink color after the addition of pdimethylamino benzaldehyde in amylalcohol to tryptone medium indicates A a the microorganism breaks down the amino acid tryptophane b the microorganism has produced Indoacetic acid c is the result expected for Enterobacter d the microorganism lacks atryptophanse e bc 38A Phenol Red Glucose medium turns pink The control Phenol Red Glucose tube is red Which component is being metabolized to produce the reaction C a glucose b acid c peptone d phenol red e carbohydrate 39 Proteolysis in Litmus Milk is indicated by C A a pink color B a white color C clearing ofmedium D white liquid medium E white hard curd with red ring at top 40 Use previous questions answers Microorganisms that produce excessive amounts of acid and reduce the medium would show which of the above results 41 What are the products of lipase on Victoria Blue medium A a b c d e fatty acids and glycerol lipid amino acids sugars cd 42 A SIM tube is turbidcloudy only along the inoculum line A pinkred color is produced upon the addition of Kovac s reagent No black color is present The result is indicated as C a 999 HZS positive motility positive motility positive Indole negative motility negative Indole positive motility positive Indole positive motility negative Indole negative 43 Which ingredient in Kovac s reagent extracts the nonpolar product E rap99 pdimethylaminobenzaldehyde sulfanilic acid potassium hydroxide ethanol amyl alcohol 44 The addition of Ferric chloride to a medium produces no color change This indicates that the microorganism E 0quot 0510 decarboxylates tryptophane deaminates phenylalanine is positive for Indole production is negative for Indole production none of the above 45 What are the IMViC results for Enterobactor B a b c d e 46 Enterobacter Vogues Proskauer test E rug99 s produces lots of acid and the phenol red indicator turns yellow produces a brick red color in the presence of pdimethylaminobenzaldhyde gives a negative test because acetoin is not produced produces 23 butanediol Which is oxidized by alpha napthol has acetyl methyl carbinol converted to diacetal by alkaline conditions 47 Phenyl ethanol agar A rap96x selects for gram positive selects for lactose negative produces a red color if lactose differentiates glucose from glucose selects for gram negative 48 Nutrient Agar Plates B a 0305 should be incubated in the upright position should be incubated in the inverted position should not have temperature raised above 400 C should only be used for streak plates contain a very selective medium 49 Complete clearing around a colony on blood agar D rug99 s is alpha hydrolysis is due to reduction of hemoglobin to a green color is beta lysis is beta hemolysis is alpha hemolysis 50Key in SS A and key in a for answer 50
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