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Date Created: 09/19/15
Summary for rst examination March 7 2013 The rst and most basic principle is that students are responsible for all material presented in lecture The second principle is that students are responsible for material in the assigned portions of the textbook subject to modi cations described below Assigned Reading for this examination Chapter 1 Chapter 2 Chapter 3 Section 66 Box 41 Section 71 to 74 Note The material on bacterial nutrition in chapter 6 sections 61 to 63 will be covered on the second exam Within the above reading assignments there are speci c comments about some sections to be emphasized and other sections to be deleted Speci cs A Topics not covered in detail or at all in lecture but which are in the textbook and for which students are responsible 1 Sample preparation for the electron microscope including shadowing and freezeetching 2 Scanning electron microscope 3 Cytoplasmic matrix 4 Molecular chaperones 5 Types oftransport Section 66 6 Endospore formation and structure but not the detailed cycle B Topics in textbook for which students are not responsible 1 Dark eld microscope 2 Phase contrast microscope 3 Fluorescence microscope 4 Eucaryotic structures chapter 4 but note that the origins of mitochondria and chloroplasts are assigned Note So that all students have the same fair chance students will not be permitted to ask questions during the exam Enclosed below is the first exam from the spring of2012 plus a portion ofthe second exam After the exam is a listing of the correct answers Please use this old examination wisely By that I mean that you should understand each of the questions presented but do not study them to such an extent that you lose sight of the principles involved This year39s exam will have 75 multiple choice questions some of which will be the same as on the previous exam However there will also be a number of questions that are similar to the old ones but which are different enough that you will be at a disadvantage if you memorized old answers without understanding One useful study approach is to look carefully at the WRONG answers to each questions on last year s exam and to figure out why that answer was incorrect Each multiple choice question will be worth 1 point There will also be five short answer questions Each short answer question can be answered with 2 to 3 sentences and will be worth 5 points BISC300 Introduction to Microbiology First Midterm Examination March 8 2012 Instructions 1 Grid in your name on the answer sheet DO NOT grid in your id number 2 Write your name on page 11 3 Turn in your completed answer sheet and short answers Multiple Choice 75 points all questions are of equal value Short answer 25 points all questions are of equal value 1 Microorganisms are used as model molecular systems This statement means a Microorganisms are more complicated than higher organisms and provided the evolutionary pattern for the molecular activities of higher organisms b The basic molecular genetic activities are very similar in all organisms although it is easier to study microorganisms c The molecular activities in microorganisms are not well understood and must be therefore be modeled d Microorganisms are quite different from higher organisms in their molecular reactions so that extrapolations cannot be made to higher organisms 2 Which of the following describes an activity of microorganisms related to water quality a They produce organic compounds and increase the organic content of sewage b They must be continually added to sewage treatment plants because they die very easily c Within a sewage treatment plant they consume organic compounds decreasing water pollution d In sewage treatment plants they produce large amounts of oxygen as they degrade the organic waste 3 Petroleum products such as gasoline and jet fuel a can be degraded by microorganisms if stored improperly b are very poisonous to all microorganisms c remain stable in storage if oxygen is absent d a and c 4 Antibiotics a were invented by chemical synthesis in the organic chemistry laboratory b are formed by bacteria and are harmful to humans c harm microorganisms because they have specific metabolic targets d are chemicals that humans synthesize to kill bacteria 5 Microorganisms are important in food preparation a by modifying the starting material in some cases so that some foods are made more difficult for humans to digest b because they must all be killed so that the food humans eat has no organisms in it c because their acid production often makes it harder for spoilage organisms to grow d all of the above 6 Antoni van Leeuwenhoek a built the first microscope b used simple microscopes c used microscopes with interchangeable lenses d All of the above 7 The term quotprocaryotequot means the same as a quotfungiquot b quotbacteriaquot c d 8 a b c quotvirusquot quotmicroorganismquot The development of good compound microscopes was difficult because each single lens in the microscope only magni es by a factor of about 10 good staining procedures were needed first it was first necessary to invent light sources with shorter wavelengths to illuminate the samples d a b c d e a b c d a b d a b c d None of the above Vitalism was supported by Koch and his workers studying contagious disease is the name given to the belief that organisms do not arise from nonliving material is the same as spontaneous generation is a term that was not applied to microorganisms but only to large organisms such as worms and ies c and d Pasteur s experiments with swannecked asks were only successful with microorganisms that do not need oxygen would not have worked well with bacteria that produced endospores provided strong support for vitalism are the same thing as Pasteurization When Pasteur boiled a ask containing fruit juice and then pulled the neck to make a swannecked ask no spoilage occurred Which of the following is an accurate explanation of what happened Boiling the ask killed the organisms that were initially present and the pulled out neck prevented them from reentering Bacteria that can grow in the absence of oxygen were excluded Pulling the neck sealed the glass so nothing could enter the ask The boiling activated previously dormant organisms but the absence of oxygen prevented them from growing Tyndall had difficulty in repeating Pasteur s experiments because Tyndall did not pull out the necks of his asks into a swan shape some of his infusions contained bacteria which form endospores his long heating times destroyed the chemicals in the infusion he prevented oxygen from entering his asks a b c d a b c d 15 a c d a b c d a b c d a b C d Tyndall s procedure called fractional sterilization kills microorganisms by raising the temperature of the infusion to 121 C sterilizes a solution by killing a portion of the microorganisms at different times cannot be used when the solution contains temperaturesensitive vitamins all of the above The spontaneous generation experiments of Pasteur Tyndall and others showed which of the following Diseases are caused by spontaneous generation Spontaneous generation was not detected under the conditions tested Infusions always showed spontaneous generation even in Pasteur s swannecked ask experiments Tyndall showed that Pasteur was incorrect in his assumptions about the presence of organisms in air A contagious disease is caused by the transfer of a microorganism between people is one which causes only mild illness cannot be passed from sick individuals to healthy ones is the same thing as an inborn genetic defect such as diabetes Koch39s Postulates were used to find the cure for many diseases were developed for the study of spontaneous generation do not require the growth of microorganisms in pure culture none of the above Which of the following was essential for the development of Koch s postulates the use of solid growth medium the construction of an autoclave to sterilize growth media the discovery that some bacteria form endospores understanding that some diseases are cause by eukaryotes such as fungi Why is it an advantage to use agar as a solidifying agent the agar provides extra nutrition for the bacteria agar is a poison for most bacteria that do not cause disease making it easier to create pure cultures bacteria usually grow faster in liquid medium agar melts at 100 C so the medium will be solid at the temperatures where most bacteria grow a b c d 20 a b c d 21 a b c d 22 a c d Pure cultures may be created for yeast as well as for bacteria may be maintained in liquid as well as on solid medium are almost never found in nature such as in soil all of the above In the bright eld microscope the condenser lens shortens the wavelength of the light before it reaches the specimen is between the light source and the specimen is only needed when high power objectives are used controls the amount of light that shines on the specimen The resolution of a microscope improves the clarity of an image after magni cation is not affected by light intensity is another way of describing focus or clarity of an image is better with longer wavelengths of illumination The resolution of a bright field microscope can be improved that is has a smaller value by using shorter wavelengths of light by using air instead of immersion oil between the objective and the specimen by decreasing light intensity none of the above 23 a b c d 24 a b c d 25 a b c d 26 a b c d 27 a b C d 28 a b c d Immersion oil is used with the lOOX objective in lab because it has a higher index of refraction than air to prevent damage to the objective from scratching against the microscope slide because it increases the magni cation that is done by the objective even though it does not improve the resolution of the microscope Which of the following is not a factor in determining the resolution of a microscope the numerical aperture of the objective the index of refraction of the material between the specimen and the objective the wavelength of illuminating radiation the magni cation power of the condenser The quotworking distancequot ofa microscope is the same for each objective larger for high magni cation objectives not affected by adding immersion oil all of the above Magni cation requires the use of immersion oil for maximum effect improves resolution is not affected by the use of immersion oil improves with shorter wavelengths of light The transmission electron microscope TEM differs from the scanning electron microscope in that it produces secondary electrons works best with intact cells that have not been sectioned is similar to the bright eld microscope because the electron beam passes through the specimen in the TEM none of the above The scanning electron microscope works best if metal ions have been incorporated inside the cells being examined is designed to reveal the external appearance of cells can only be used to observe bacteria if the cells have been cut into very thin sections all of the above 29 a b c d 30 a b c d 31 a c d 32 a b c d 33 a b c d 34 a b c d 35 The freezeetch procedure minimizes the formation of artifacts since the cells are frozen quickly does not require the cells to be chemically fixed is used with the transmission electron microscope all of the above The shadowing of specimens for electron microscope observation requires careful control of the direction of the light so a shadow is created gets its name from the way that metal coats one side of the specimen more than the other making it appear to be a shadow is frequently done for scanning electron microscope examination since the external structure shows the shadow so clearly requires appropriate staining with a dye that has proper contrast with the metal that creates the shadow In most cases if samples are not fixed before they are stained dyes will not stick to the specimen different pa1ts of a cell cannot be distinguished the staining procedure is likely to alter the shape of the cell ultraviolet irradiation must be used to preserve external shape A mordant is another name for a dye a chemical which increases the effect of a dye the same thing as a counterstain usually iodine Positive stains can be used with either Gram positive or Gram negative bacteria may not be used with the electron microscope cause yeast cells to appear purple in the light microscope are not effective with animal cells due to the absence of a cell wall Negative stains were first developed to examine external structures on cells may be used with the light microscope make bacteria appear red in the light microscope a and b The capsule stain procedure described in class for the light microscope is a b c d 36 a b c d 37 a b c d a positive differential stain a negative differential stain both positive and negative differential stain a simple differential stain The Gram stain procedure leaves some cells red at the end of the procedure These red cells have been positively stained have been negatively stained were unable to incorporate the crystal violet stain are not decolorized by the addition of ethanol alcohol The agella and endospore staining procedures are both positive stains differential stains simple stains a and b Note that in the following several questions the terms quotplasma membranequot and quotcell a b c d membranequot are used interchangeably The cell membrane is outside ofthe cell wall allows the free entry and exit of solutes through porins of procaryotes is primarily composed of phospholipids is very rigid in procaryotes due to the presence of cholesterol 39 a b c d 40 a b c d 41 a b c d 42 a b c d 43 a b c d 44 a b c d The assembly of phospholipids into a membrane requires covalent connections of adjacent fatty acid side chains to each other allows the polar portions of the phospholipids to associate with each other requires the nonpolar portions of the phospholipids to avoid each other b and c Cell membranes are permeability barriers to polar solutes because the hydrophobic glycerol backbones of the phospholipids interact with the solutes unless the membranes have selective transport proteins to allow the solutes to cross because the fatty acid side chains of the membrane interact hydrophilically with the polar solutes since water is not associated with these polar solutes making them hydrophobic Plasma membranes in bacteria are stronger than the membranes of animal cells because of the presence of the cell wall are called quot uidquot because they have a great deal of water in their middle section are probably stabilized by hopanoids are separate structures from the nuclear membrane Diffusion is a chemical pressure for solute concentrations to become equal is another term for transport of solutes across a membrane forces solutes through a membrane if the concentration imbalance is great enough helps get solutes into a cell it does not work to get solutes out Facilitated diffusion requires a supply of energy such as ATP results in the transfer of solutes from regions of high concentration to regions of low concentration changes the molecules that are transported a and c Active transport may be done by using the energy in a companion gradient of protons may bring solutes into a cell or export them can move solutes from areas of low concentration to high concentration requires the involvement of specific membrane proteins e 45 a b c d 46 a b c d all of the above Group translocation only transports molecules from areas of high concentration to low concentration does not change the molecule being transported alters the transported molecules for example by phosphorylating them produces energy in the form of a companion gradient of protons Cell walls would be stronger if all their amino acids were in the Lform are strong even though they are exible protect cells from damage when placed in dilute solutions protect cells from damage under acidic conditions 47 The polysaccharide portion of peptidoglycan is correctly referred to as a heteropolymer which means a some of the sugars are in the Dform and some in the Lform b that peptidoglycan has a peptide portion as well c some bacteria use DAP and some use Lysine in their peptide chain d the polysaccharide portion contains more than one kind of sugar 48 The cells of multicellular animals such as humans don t need cell walls because a the membranes allow solutes to penetrate thereby avoiding the generation of osmotic pressure b the membranes have steroids and are therefore very strong c the cells are rarely exposed to hypotonic conditions d if they lyse the cell contents are retained in the organism 49 Peptidoglycan a restricts the transport of small solutes MW less than 400 across the cell membrane b expands in different patterns in rodshaped and spherical bacteria c becomes weak when it expands during synthesis d a and c 50 Peptidoglycan a is unique in that it contains Lamino acids b contains long chains of amino acids which may be crosslinked by short chains of sugars c obtains its great strength by completing all possible crosslinks between backbone chains d is composed of subunits that are synthesized inside of the cell membrane 51 Muramic acid a is present in most cell walls both in bacteria and eucaryotes b is present at the same concentration as glucosamine in the peptidoglycan of Gram positive bacteria c is attached to a chain of four amino acids before insertion into a growing peptidoglycan molecule d helps form part of the peptide crosslinks in the outer membrane of Gram negative bacteria e b and c 52 Direct crosslinking a b c d a b c d a b c d makes Gram negative bacteria have weaker cell walls results in peptidoglycan that has more open spaces requires the presence of a pentaglycine bridge only occurs in Gram negative bacteria Transpeptidation is another term for crosslinking Which of the following is true about transpeptidation It only occurs outside the cell membrane as peptidoglycan subunits are inserted into the cell wall It occurs more rapidly in the presence of the antibiotic penicillin It occurs inside the cell during the synthesis of peptidoglycan subunits It occurs more rapidly in Gram negative bacteria due to the protection of the outer membrane The crosslinking of peptidoglycan results in a less open structure in Gram negative cells with smaller spaces between backbone chains is stronger with a pentaglycine bridge as a spacer only occurs in Gram positive bacteria that are not actively growing gets most of its strength because Damino acids are involved 55 a b c d 56 a The third amino acid in the chain of four connected to muramic acid in peptidoglycan must be DAP has to be in the Lcon guration must have two amino groups is the same in all bacteria The lipopolysaccharide quotouter membranequot is an osmotic barrier that requires active transport for the incorporation of small solutes b c d 57 a b c d 58 a b c d 59 a b c d 60 a b makes Gram positive bacteria generally resistant to penicillin is connected to the peptidoglycan in Gram negative bacteria lies just underneath the peptidoglycan in Gram negative bacteria Antibiotics such as penicillin are effective more often against Gram positive bacteria because Gram negative bacteria have their peptidoglycan protected by the outer membrane because the structure targeted by penicillin is uniquely procaryotic only when the bacterial cells are growing and expanding their cell walls all of the above Lysozyme is produced by many bacteria as a normal defense against animals attacks actively growing bacteria as well as inactive bacteria is a natural compound produced by some microorganisms to attack other microorganisms cleaves protein crosslinks in peptidoglycan The different appearances of Gram positive and Gram negative cells inthe Gram stain procedure results primarily from chemical differences between the two types of cell walls arises from the multiple layers in the cell wall of Gram negative bacteria occurs because Gram positive cells keep crystal violet from washing out when alcohol is added show that Gram positive walls are much stronger Old cultures of Gram positive bacteria sometimes appear red or pink at the end of the Gram staining procedure Why These cultures do not incorporate crystal violet Their cell wall changes so that they become Gram negative c d 61 a b c d 62 a b c d 63 a b c d 64 a b c d 65 a b C d 66 a The alcohol dehydrates the thick wall causing it to collapse and trap the crystal violetiodine complex The wall has been weakened due to the failure to insert new peptidoglycan subunits so that dehydration does not cause collapse Ribosomes are of two sizes in procaryotes composed of a single subunit in procaryotes the same size in procaryotes and eucaryote organelles not present in mitochondria and chloroplasts Chloroplasts and mitochondria can be grown in pure culture in the laboratory possess 80s ribosomes contain DNA molecules contain cell walls made of simple polymers of glucose The endosymbiotic or endosymbiont theory is supported by the observation that mitochondria and chloroplasts contain DNA is an explanation for the origin of bacteria proposes that procaryotes are A none of the above ul 1 J J from la and 39 39 Some antibiotics have 70s ribosomes as their target Which of the following is true when this drug is taken to ght an infection Cytoplasmic ribosomes in human cells may be damaged Prolonged exposure to such drugs may damage humans by attacking actively metabolizing tissues Only the ribosomes on the endoplasmic reticulum are harmed the free ribosomes are unaffected Only human cells are harmed bacteria do not have 70s ribosomes Pili are only found on spherical bacteria are the same size as agella may be used to help bacteria swim none of the above Endospores are formed by the addition of a layer to the outside of a complete bacterial cell b d 67 a b c d 68 a b c d 69 a b c d 70 a b c d contain an internal structure called the sporangium which protects the DNA are formed during a process called germination have multiple layers The process of endospore formation occurs within the bacterial cell results in the addition of a substantial amount of water to the developing endospore creates a new structure which is very similar to the cell in which it was made only smaller is a response by the cell to favorable environmental conditions The germination of an endospore results in the formation of an actively growing vegetative cell causes all the water in the spore to be lost begins with the engulfment of the majority of the original cell s cytoplasm none of the above Capsules and slime layers may protect bacteria which cause disease such as pneumonia against the phagocytic cells of the human defense system are generally composed of proteins are thought to assist bacteria by increasing their ability to swim all of the above Procaryotic agella always occur in tufts or clumps at one end of the cell are approximately the same size as pili propel cells by rotation like a propeller function as organelles of attachment as well as propulsion 71 a b c d 72 a b c d e 73 a b c d 74 a b c d 75 a b C d F lagella in bacteria grow from the tip not the base are formed from pili which continued to grow are assembled in complete form inside the cell and then exported may rotate in either direction thereby allowing the cells to reverse direction easily Which of the following statements is true for procaryotic agella They may occur singly or in tufts They are formed from subunits called agellin in a process called selfassembly They cause motion by the sliding of musclelike bers against each other They cause motion by a whiplike action a and b In chemotaxis bacteria run continuously when in the presence of a uniformly high concentration of an attractant bacteria sense attractants when these molecules are bound by the cell s agella twiddles occur whenever a bacterium encounters a repellent attractants or repellents are sensed when they bind to specific chemoreceptors During the chemotactic response of bacteria to an attractant the bacteria will swim more rapidly in the presence of uniformly high concentrations of attractant bacteria will run continuously no twiddles when the concentration of attractant is uniformly high the concentration of the attractant is sensed during twiddles the concentration of the attractant is sensed during runs Bacterial chemotaxis away from a repellent has less frequent twiddles when moving quotupquot the gradient toward higher concentration has shorter runs when moving quotupquot the gradient toward higher concentration has shorter runs when moving quotdownquot the gradient toward lower concentration none of the above there is no direction to chemotaxis in the presence of a repellent Questions 1 to 7 from Exam 2 1 Growth curve experiments indicate the activity of individual bacteria in the culture cannot be done with direct count measurements only reveal an exponential phase if samples are also taken during lag phase may be used to determine the manner of action of an antibiotic The lag phase in a bacterial growth curve is always the same length is shorter when cells are transferred from similar growth conditions ends sooner when measured by viable count procedures is essential for determining the mechanism of a bacteriostatic antibiotic The direct count procedure gives the number of both live and dead cells is used to determine the number of cells in a bacterial colony cannot be used with aerobic bacteria because the process removes oxygen is performed with a spectrophotometer Which one of the following is a limitation in using the pour plate technique to measure bacterial growth bacteria which are embedded in the agar will not be able to grow some colonies may arise from more than one cell leading to an overestimate of the calculated concentration if plates have too few colonies then the results are not statistically reliable only bacteria that do not require oxygen will grow on pour plates Mass measurements of a growing bacterial culture cannot be used in the calculation of doubling time usually show a longer lag phase than viable counts do not distinguish between living and dead cells give results identical to viable count measurements Pour plates and spread plates do not distinguish between live and dead cells can be used to determine doubling time only if calibrated with a spectrophotometer first c d are not accurate if the sample is diluted before plating are both viable count procedures Spectrophotometers give total counts and cell mass very rapidly usually require dilution of the sample are a rapid way to obtain an estimate of bacterial concentration are used to measure the viable count of bacterial cultures Multiple Choice answers for questions 1 to 75 from Exam 1 D Ib I eopW QP39 eP Nt ommoamc oc ac oooammc c aamamc c c mc oa U U OOQOCquot U CLCLONONNNCLCLU NOOCLOU CLOONNQQCLU OCLOOQU NOU U Multiple Choice answers for questions 1 to 7 from Exam 2 899 Nf oaocrmcra Short answer questions on Exam 1 76 Why did Tyndall call his sterilization procedure fractional sterilization Why was it necessary for him to deVise this procedure DO NOT SIMPLY LIST THE STEPS OF THE PROCEDURE Name of procedure The population of microorganisms in the sample are not all killed at once A portion or fraction is killed in each heating cycle Purpose of procedure This multistage procedure was necessary to kill the bacteria in the sample which formed endospores A single boiling was not e ective Common incorrect answers He did not use different temperatures all heating was boiling The purpose was not to test spontaneous generation but to achieve a sterile infusion The fact that this procedure is still used today for vitamin solutions etc is not relevant to this question The most frequent mistake was to describe the procedure without any explanation 77 Explain how immersion oil improves resolution in the bright eld light microscope Immersion oil has a higher index ofrefraction 13 than air 1 0 There are two ways to explain the relation of the increased index of refraction to improved resolution The first is to write the equation for resolution and show that index of refraction is in the denominator Therefore when this value increases the resultant resolution minimum distance or diameter decreases and that is the reason to do it The second explanation would be to note that oil causes the light beams to bend so that more light enters the objective and less is scattered and lost It is M correct to say that the wavelength of the light is shortened 78 Peptidoglycan is a rigid molecule When cells enlarge they must increase the size of the peptidoglycan How do they make the peptidoglycan larger while keeping it rigid The basic point is that peptidoglycan is assembled by the insertion of subunits into an existing molecule The subunits are two sugars muramic acid and glucosamine although that detail is not needed attached to a string of four amino acids The existing molecule is cut by autolysins and then the subunits are inserted This process does not weaken the wall because the cutting and insertion pasting are carefully balanced so that they happen at nearly the same time and not all at the same place If these activities were not carefully regulated then the wall would weaken A common incorrect answer was to say that transpeptidation or crosslinking is responsible for the strength The strength comes from the fact that there are both polysaccharide and peptide bonds and both are needed for strength not just one of them 79 Tetracycline is an antibiotic for which the metabolic target is the 70s ribosome Why are Gram positive cells usually killed more easily by this antibiotic than Gram negative cells are The fundamental issue is w of the antibiotic to its target The ribosomes which are the target are of course inside the cell The Gram negative bacteria have an outer lipopolysaccharide membrane which has porins that exclude molecules the size of antibiotics Gram positive bacteria do not have the outer membrane and therefore the tetracycline easily penetrates the wall Common mistakes were to mention the action of penicillin or to say that the peptidoglycan is more exposed in Gram positive bacteria The Gram stain reaction and the thickness of the cell wall are not part of this question All runs by bacteria eventually end in twiddles even when they are moving the cell into a quotbetterquot position Explain being sure to consider both positive motion toward an attractant and negative motion away from a repellent chemotaxis It is most important to keep in mind that bacteria cannot choose the direction in which they swim The purpose of a twiddle is to give the cells a chance to go in another random direction The specific answer to the question is that cells going in a favorable direction will be benefitted by periodically twiddling so that new directions can be explored These twiddles will happen infrequently under these conditions but it is important that long runs be interrupted this way Positive chemotaxis has long runs up a concentration gradient and negative chemotaxis has long runs down the gradient The logic is the same in both cases even though conditions are improving they may be better in some other direction The most common mistake was to say that the bacteria move toward a high concentration of nutrient or away from a high concentration of repellent This is incorrect since they respond only to concentration changes namely gradients not to any particular concentration What cells do when nutrients or repellents are in uniform concentration was not part of this question Short answer question from exam 2 76 Consider the following You are testing the method of action of an antibiotic on a pure culture of bacteria You perform a growth curve experiment in which you are measuring both viable count and turbidity The antibiotic being tested is added in the middle of the exponential phase Draw two graphs with two lines on each and with correct labels on each axis The first graph has the results you predict for a bacteriostatic antibiotic The second has the results you predict for a bacteriolytic antibiotic Explain the differences between the two graphs Two graphs must be shown to get full credit Axis labels must be correct The y axis must be log of cell concentration not just cell number The x axis must be time Each graph must have two lines one for the viable count measurement the other for the turbidity measurement The Baceriostatic graph must show both lines staying together and leveling off after the antibiotic is added Both graphs must show the time of addition of the antibiotic The bacteriolytic graph must also have both lines staying together and must clearly show a decline after the addition of the antibiotic The di erences are explained by the fact that the bacteriostatic antibiotic stops growth without killing cells so everything stays constant whereas the bacteriolytic antibiotic lyses the cells which kills them immediately
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