Bacterial Growth and Metabolism - Lecture Notes, PDF

Lecture 8 Bacterial growth and metabolism BIO153 Diversity of Organisms Instructor: Ichiro Inamoto University of Toronto Mississauga 1 Bacterial growth One cell Bacter...

Lecture 8 Bacterial growth and metabolism BIO153 Diversity of Organisms Instructor: Ichiro Inamoto University of Toronto Mississauga 1 Bacterial growth One cell Bacteria replicates by binary fission Parent cell divides into two new cells Growth Bacterial population grows exponentially One becomes two, two becomes four... Reaches enormous number in short time Cells divide in the middle For example, Escherichia coli divides once every 20 minutes under optimum condition One cell becomes 8 cells after 1 hour One cell becomes 262,144 cells (0.26 million) Separation after 6 hours One cell becomes 68,719,476,736 cells (69 billion) Two cells after 12 hours 2 Bacterial growth Some members of population mutated Number is power into antibiotic resistance strains by chance (red cells) More cell division means more DNA replication Antibiotic treatment Antibiotic resistant More DNA replication means more chance strains survive for DNA to mutate antibiotics (natural selection) Reproducing to huge population increases the chance that some members of Regrowth population, by chance, have the mutation to react to new challenges in environment Survivors grow back into a population of antibiotic resistant This is how antibiotic resistance spreads bacteria 3 Growth needs energy and carbon source Requirements of life / growth: 1. Needs energy 2. Needs carbon source 3. (among many other elements like nitrogen) Photoautotrophs make organic molecules (such as glucose) from sunlight, water and CO2 Chemoheterotrophs these organic molecules to extract energy and as a carbon source Escherichia coli Gram negative chemoheterotroph How is glucose used to produce energy? 4 Glycolysis: extract energy from glucose Glucose How to extract energy from glucose? 2 ATP Glucose is a 6-carbon sugar Glycolysis Glycolysis (glucose-lysis) Pay 2 ATP at beginning to begin reaction Splits glucose into half while extracting 4 e- energy 4 H+ Glycolysis generates: 4 ATP 2 pyruvate (3-carbon sugar) 4 ATP 2 Pyruvate 4 electrons (e-) + 4 protons (H+) Net 2 ATP gain per glucose Of 4 ATP produced after splitting 1 glucose: 2 gets used to split another glucose 2 gets used for other jobs in the cell The 4 electrons need to go somewhere 5 Glycolysis: extract energy from glucose Glucose 2 ATP NAD+ is an organic molecule which can bind to electrons NAD+ accepts 2 electrons and turns into NADH Glycolysis 2 NAD+ 4 e- NAD+ used to capture electron, becomes NAD+ + H- + 2 e- = NADH 4 H+ NADH 2 NADH Every time glucose gets split, NAD+ is used 2 H+ 4 ATP to accept electrons The extra two protons 2 Pyruvate gets released into cytoplasm (these PROBLEM: Limited number of NAD+ in cell protons will be abbreviated from next slide) Can not do glycolysis once NAD+ gets depleted Need to regenerate NAD+ 6 Fermentation Glucose alcohols, acids, etc. 2 ATP Use pyruvate to regenerate NAD+ Pyruvate is the other product produced by glycolysis Glycolysis 2 NAD+ Fermentation Pass electrons from NADH to pyruvate to 4 e- regenerate NAD+ 4 e- 2 NADH Pyruvate + NADH = 4 ATP NAD+ + fermented products 2 Pyruvate Pyruvate gets turned into fermentation products in the process Fermentation is not efficient alcohols, acids, etc. Pyruvate is a 3-carbon molecule which has more energy stored Fermentation does not use this extra Fermentation happens anaerobically energy since it uses pyruvate to regenerate NAD+ 7 Aerobic Respiration Glucose 34 ATP (theoretical maximum) H2O 2 ATP TCA cycle extracts energy which is left inside pyruvate Electron aka Krebs cycle, Citric acid cycle Transport Chain One pyruvate eventually becomes 3 CO2 Glycolysis 2 NAD+ 4 e- O2 TCA cycle makes more NADH (and other 4 e- Aerobic electron carriers) + ATP Respiration 2 NADH 4 ATP NADH gives electrons to Electron Transport Chain 2 Pyruvate Regenerates NAD+ more TCA Cycle NAD+ Energy is produced as electrons pass through ETC, which is used to make ATP e- At the end of ETC, electrons are put onto O2, 4 e- the terminal electron acceptor 2 ATP more 6 CO2 NADH 8 Aerobic Respiration is very efficient Glucose 34 ATP (theoretical maximum) H2O 2 ATP Aerobic respiration extracts the maximum amount of energy from glucose, Electron producing up to 38 ATP per glucose Transport Chain Glycolysis 2 NAD+ Fermentation produces 2 ATP 4 e- O2 O2 is a very powerful electron acceptor 4 e- Aerobic Respiration 2 NADH 4 ATP Using O2 as the terminal electron acceptor allows electrons to pass through 2 Pyruvate ETC at maximum efficiency, extracting maximum energy more TCA Cycle NAD+ Aerobic organisms (like human) are e- dependent on O2 to produce energy 4 e- 2 ATP more 6 CO2 NADH 9 Anaerobic Respiration Glucose less than 38 ATP reduced e- 2 ATP acceptors Respiration can be done using molecules other than O2 as terminal Electron Transport Chain electron acceptors Glycolysis 2 NAD+ NO3- (nitrate) non-O2 e- 4 e- SO42- (sulphate) acceptors 4 e- Anaerobic Respiration 2 NADH Non-O2 electron acceptors are not as 4 ATP effective as O2 to drive electrons through ETC 2 Pyruvate more Anaerobic respiration does not produce TCA Cycle NAD+ as much energy as aerobic respiration e- Still produces much more than fermentation 2 ATP 4 e- more 6 CO2 NADH 10  Image credits at end of slides Microorganisms and respiration Various adaptations to environments Obligate aerobes Oxygen required for survival Mycobacterium tuberculosis Obligate aerobe Respiratory pathogen Facultative anaerobes Can use oxygen when available Can survive by anaerobic respiration and/or fermentation if necessary Obligate anaerobes Can not survive when oxygen is present E. coli Oxygen is extremely reactive and is Facultative aerobe poisonous for organisms who does not Gut microbe/pathogen have protective measures 11  Image credits at end of slides Humans can also do fermentation Humans are obligate aerobes Glucose is consumed using O2 during aerobic exercise High Intensity Interval Training, During intense anaerobic exercise, oxygen an anaerobic gets depleted in our body exercise glucose We ferment pyruvate into lactic acid to produce more energy anaerobically pyruvate Accumulation of Lactic acid Lactic is said to be correlated with muscle fatigue, although this no oxygen oxygen theory is sill being debated Lactic acid Aerobic fermentation respiration 12  Image credits at end of slides Food microbiology: Yogurt fermentation Must be done anaerobically Lactobacillus bulgaricus and Streptococcus thermophilus are put into milk Both Gram positive lactose-fermenting bacteria Lactose fermented to lactic acid lactose (in milk) Acidifies the product, thickening the solution In addition, L. bulgaricus and S. thermophilus performs other other metabolic activities glucose All of this contributes to the taste and texture of yogurt pyruvate Acidification of yogurt (+ high incubation no oxygen oxygen temperature) suppresses growth of other bacteria such as E. coli Lactic acid Aerobic fermentation respiration 13  Image credits at end of slides Food microbiology: Alcohol fermentation Yeast (Saccharomyces cerevisiae), a unicellular eukaryote (Fungi) agave sugarcane Used for many food processes, including production of alcohol from various sources of starch malted barley grape rice sources of fermentable starch Type of starch contributes to the type of alcoholic beverage produced glucose Alcohol production begins to inhibit yeast growth after a while pyruvate Distillation is necessary to produce alcoholic no oxygen oxygen beverage with a higher alcohol % distillation for some Ethanol Aerobic fermentation respiration alcohols 14 Cyanobacteria: producing glucose Eukaryote Gram negative photoautotrophic bacteria Archaea Only clade of bacteria capable of photoautotrophy Proteobacteria Use sunlight to produce organic molecules like glucose from CO2 Chlamydia Carbon fixation Chemical energy generated by sunlight gets stored Spirochete in glucose CO2 + H2O + sunlight = glucose + O2 Cyanobacteria Gram-positive bacteria Figure 27.16 redrawn 15 Cyanobacteria and nitrogen fixation Some cyanobacteria are also capable of nitrogen fixation: convert atmospheric N2 to ammonia (NH3) Nitrogen is essential for making DNA, proteins, etc. Most organisms can not use N2 as their nitrogen source and depend on ammonia produced by nitrogen fixers Figure 27.14 Problem: Cyanobacteria, Gram negative photoautotroph 1. Nitrogen fixation cannot happen when there are O2 near-by 2. Cyanobacteria produces O2 via oxygenic photosynthesis during carbon fixation How to resolve this...? 16 Cyanobacteria and multi-cellularity Filamentous bacteria show true-multicellularity Cells in multicellular body specialize their function and depend on one another for survival Some cells in cyanobacteria filament terminally differentiate to heterocysts: cells specialized for nitrogen fixation Heterocysts can not survive on its own N2 Can not photosynthesize and depends on neighboring vegetative cells to provide glucose etc. CO2 N2 CO2 glucose Heterocysts form barrier to block O2 entry, + allowing nitrogen fixation inside their cell O2 NH3 Vegetative cells performs Heterocysts provide fixed nitrogen to carbon fixation Heterocyst performs nitrogen fixation neighboring cells (photosynthesis) 17 Image Credits. Images may be cropped. No other modifications were made to the original image. Janice Carr, CDC Public Domain https://no.m.wikipedia.org/wiki/Fil:Mycobacterium_tuberculosis_8438_lores.jpg USDA (Pina Fratamico Microbiologist/Lead Scientist) Public Domain https://en.wikipedia.org/wiki/Escherichia_coli_O157:H7#/media/File:EColiCRIS051-Fig2.jpg 18 Image Credits. Images may be cropped. No other modifications were made to the original image. Kiet Le CC BY 2.0 https://en.wikipedia.org/wiki/High-intensity_interval_training#/media/File:HIIT_Workout.jpg 19 Image Credits. Images may be cropped. No other modifications were made to the original image. Takeaway CC BY-SA 4.0 https://en.wikipedia.org/wiki/Yogurt#/media/File:Turk ish_strained_yogurt.jpg Keith Weller/USDA Public Domain https://en.wikipedia.org/wiki/Cattle#/media/File:Cow_female_black_white.jpg NIAID CC BY 2.0 https://en.wikipedia.org/wiki/Milk#/media/File:Glas s_of_Milk_(33657535532).jpg 20 Image Credits. Images may be cropped. No other modifications were made to the original image. blue Weber agave grapes © Vyacheslav Argenberg / Stan Shebs http://www.vascoplanet.com/ CC BY-SA 3.0 CC BY 4.0 https://en.wikipedia.org/wiki/Blue_agave https://en.wikipedia.org/wiki/Grape#/media/File #/media/File:Agave_tequilana_1.jpg :Grapes,_Rostov-on-Don,_Russia.jpg sugarcane rice ruurmo CC BY-SA 2.0 https://en.wikipedia.org/wiki/Sugarcan 中国新闻网 e#/media/File:Cut_sugarcane.jpg CC BY 3.0 https://en.wikipedia.org/wiki/Rice#/media/File:2 0201102.Hengnan.Hybrid_rice_Sanyou-1.6.jpg malted barley Pierre-alain dorange CC BY-SA 3.0 https://en.wikipedia.org/wiki/Malt #/media/File:Malt_en_grain.JPG 21