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by: Ezequiel Orn


Ezequiel Orn
GPA 3.89


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Class Notes
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This 34 page Class Notes was uploaded by Ezequiel Orn on Sunday September 6, 2015. The Class Notes belongs to BIO 226N at University of Texas at Austin taught by Staff in Fall. Since its upload, it has received 74 views. For similar materials see /class/181732/bio-226n-university-of-texas-at-austin in Biology at University of Texas at Austin.




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Date Created: 09/06/15
Copyright 0 McGraw Hill Companies Inc Pomion required for Woduchon or display Chapter 6 Microbial Growth 0th c Meanme Wm Inc Pomaim aquircd kn W or display Growth increase in cellular constituents that may result in increase in cell number eg when microorganisms reproduce by budding or binary ssion increase in cell size 39 eg coenocytic microorganisms have nuclear divisions that are not accompanied by cell divisions microbiologists usually study population growth rather than growth of individual cells Copyright 0 McGrawHill Compmu Inc Pomsnim mquirsd for roptoducbnn 01 display The Growth Curve observed when microorganisms are cultivated in batch culture culture incubated in a closed vessel with a single batch of medium usually plotted as logarithm of cell number versus time usually has four distinct phases HEUmmmEE lmPin mmuwedmir pmuumnnw Lag phase no increase 2 E o 2 I E gt o s a n E I c o population growth ceases Stationary phase Exponential log phase maximal rate of division and population growth line in Iulation u Figure 61 4 Copyright 0 MchHill Carpnu Inc Pomuhquot required for reproduction cw dlsplny Lag Phase cell synthesizing new components eg to replenish spent materials eg to adapt to new medium or other conditions varies in length in some cases can be very short or even absent Copyright 0 McGravaill Campinas Inc Formation acquired for roproducbon or display Exponen alPhase 39 also called log phase rate of growth is constant population is most uniform in terms of chemical and physical properties during this phase nsirquot1Li1Iiv1rmr Ii mm 4 w mum 411 11 mm m 1640 Table 61 An Example of Exponential Growth Division Population Time Number 2quot No X2quot logmNr 0 0 2 2 1 1 0000 20 1 2 2 2 0301 40 2 22 4 4 0602 60 3 23 8 8 0903 80 4 2quot 16 16 1204 100 5 25 32 32 1505 120 6 26 64 64 1806 The hypolheiicai culture begins wiih an cell having a 20minute generation lime mvzajisg 1 H110 div 0 7j and d0 Mnmibmr 51 1055311 mmmmwmmmm mmwmmmw mam mm 9mmme WW m2 Mmm V W693 Numr m eels D o S Lug numrofoalb o a mum at Incubation Copyright 0 McGrawLHill Companies Inc Pomion required for reptoduchon or display Balanced growth 39 during log phase cells exhibit balanced growth cellular constituents manufactured at constant rates relative to each other Copyright 0 MchwHill Carmamu Inc Pomim ruquirsd lot reproduction 01 display Unbalanced growth rates of synthesis of cell components vary relative to each other occurs under a variety of conditions change in nutrient levels shiftup poor medium to rich medium shiftdown rich medium to poor medium change in environmental conditions mammvmmmm mmm m WW WQWW i1 113W Effect of nutrient concentra on on growth Total growth cells or mgml Gmwth rate hf39 Wm Copyright 0 MchwHill Comomu Inc Pomsnim ruquirsd for reproducan 01 display Stationary Phase total number of viable cells remains constant may occur because metabolically active cells stop reproducing may occur because reproductive rate is balanced by death rate Copyright O McGraw Hill Companies Inc Porrnsslon required for repfoduchon or display Possible reasons for entry into stationary phase nutrient limitation limited oxygen availability toxic waste accumulation critical population density reached Copyright 0 MchwHill Compmu Inc Pomsnim ruquirsd for reproduction 01 display Starvation responses morphological changes eg endospore formation 0 decrease in size protoplast shrinkage and nucleoid condensation production of starvation proteins 0 longterm survival increased virulence Copyright 0 MchwHill Compnu Inc Pomubn required kn mpmducuon 01 display Death Phase cells dying usually at exponential rate 39 death irreversible loss of ability to reproduce in some cases death rate slows due to accumulation of resistant cells Copyright 9 McGraw Hill Companies Inc Pomssion required for reproduction or display The Mathematics of Growth generation doubling time time required for the population to double in size 0 mean growth rate constant number of generations per unit time usually expressed as generations per hour 100 3 2 3 s 5 g ESE Mn D gure 64 Tlml mm 3 um mm n quot39leim T vnwwm a 7 m wrung14 Table 62 Generation Times for Selected Microorganisms Temperature Generaliun Tune Microorganism 5 Hours mm in Baum kw quotmm m 17 EuImvn hm m7 An I i mm mm 40 mm m m u Hmwn 77 Pwulmmmm WWW 17 Clmlmlum Iwmluwm 17 Rmvlmpu39rinm r39nln39um s M mm rHHuHm s 3 Drrm39mmmlmrumrx 37 Twpowmt Imllidum 37 Algae Smumvrmm qmmmmm 25 59 Mumlln Holmnlom 2s 775 l in Q6 2 709 Lurmum mum 2r 31x Pmmmn nwlmmm mm 24 224 2 I Ahmmm Immwrm 26 H z Pnrumurimn i39umlulum 2n ma Aumllmtmmhl Ierm 3K H IZ mumquot himIlia 37 i x Fu 5 Shrtmmmyrm m m mrm m 1 Munilmmjwm 1 m Copyright 9 McGraw Hill Cowman Inc Pomsslon required for raptoducuon 0 display Measurement of Microbial Growth can measure changes in number of cells in a population can measure changes in mass of population Copyright 0 McGrawLHill Compnnes Inc Pomlon required for reproduction or display Measurement of Cell Numbers Direct cell counts counting chambers electronic counters on membrane lters Viable cell counts plating methods membrane ltration methods mwum m vuan lH v lV k m a mmn ngIa w xmmnlmmw u magw Caunt ng cham hers O O O rmameem 5mm Jm d wm m FM wmimg Ema am WWWEM emmm g mgw gm Liming mm wdl ng Eigma Copyright 0 MchwHill Carmamu Inc Pomim ruquirsd kn reproducnnn 01 dlsplny Electronic counters microbial suspension forced through small ori ce movement of microbe through orifice impacts electric current that flows through ori ce instances of disruption of current are counted Copyright 0 McGravaill Compmos Inc Permslion required for reproducth 01 display Electronic counters 39 cannot distinguish living from dead cells quick and easy to use useful for large microorganisms and blood cells but not procaryotes Copyright 0 McGravaill Companies Inc Formation required for roptoductmn or display Direct counts on membrane filters 39 cells ltered through special membrane that provides dark background for observing cells cells are stained with uorescent dyes 39 useful for counting bacteria 39 with certain dyes can distinguish living from dead cells Copyright 9 McGraw Hill Cowman Inc Pomssion required for repfoduchon or display Plating methods measure plate dilutions of number of population on suitable viable cells SOlid medium population iv size is count number of expressed as colonies colony forming units calculate number of CFU cells in population Copyright 0 McGrawHill Compmu Inc Permission required for reproducth 01 display Plating methods 39 simple and sensitive 39 Widely used for viable counts of microorganisms in food water and soil inaccurate results obtained if cells clump together 1 r m u Mem baf ing fi tra am mgtlmds rm u mpgmm 7 xmu m mm m mm ww 4 mmanun m 24 mm gamma mar 1 on a mm mm EJ11ng H Copyright 0 McGravaill Camsmu Inc Formation required for reproducnon 01 display Measurement of Cell Mass dry weight time consuming and not very sensitive quantity of a particular cell constituent eg protein DNA ATP or chlorophyll useful if amount of substance in each cell is constant turbidometric measures light scattering quick easy and sensitive awnmmmwwm x mm m mm 191 mm mammww u my Spectraphoiometer meier mm milks g igh 4L Lamp Tube a1 thocell terial or detector ban Flgure 68 suspensinn O McGraw Hill Companies Inc Permission required for reproduction or display The Eventinuous Culture of Microorganisms growth in an open system continual provision of nutrients continual removal of wastes maintains cells in log phase at a constant biomass concentration for extended periods achieved using a continuous culture system awumw mmwmqummmm m iwmb nueyymmm mmnmm u mm The Chemastat O 0 mm M fum mfumg mmin E pf 31me medl m i mum vwa 2mm gcamxtiad min m gs Em UM in mgg lwminiibm Figure 69 Receptacle mm nmmmmmmm Imx mmmw wwmmm i1 ew Dilution rate and microbial my a gm Figure 610 nuuuon rate Copyright 0 MchwHill Compnu Inc Pomubn required kn mpmducnon 01 display The Turbidostat regulates the flow rate of media through vessel to maintain a predetermined turbidity or cell density dilution rate varies no limiting nutrient turbidostat operates best at high dilution rates 33


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