4/6/2015. Bacterial Growth and Nutrition. Nutrients + Oxygen. Temperature. Temperature

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1 Bacterial Growth and Nutrition ph Nutrients + Oxygen Temperature Temperature 1

2 Environmental Oxygen Requirements -- can support or hinder growth 1. Aerobic need high oxygen concentration to grow 2. Anaerobic need very low or no oxygen to grow 3. Facultative can grow with or without oxygen 4. Capnophilic require high concentration of CO2 to grow ph -- a measure of the H+ ion concentration Most bacteria prefer neutral ph (re: human pathogens 7.35) Neutrophiles live best between ph 5.5. and 8.5 Acidophiles grow best below ph 5.5, Basophiles prefer above ph affects the protein structure of cells 2

3 Nutrients -- needed to produce energy -- needed for biosynthesis of cellular components Main nutrients: C / O / N / H / P / S Others needed: K / Na / Mg / Cl / Fe -- also trace metals needed Bacteria: Reproduction by Binary fission 3

4 A Bacterial Growth Curve Metabolism = the sum total of all biochemical reactions taking place in a cell A. Catabolism: breaking down of chemical compounds from larger to smaller; break bonds, release energy ( exergonic reactions) B. Anabolism: synthesis of chemical compounds; requires energy to create new bonds ( endergonic reactions) 4

5 Role of Enzymes in Metabolism -- catalyze reactions (speed them up) -- decrease activation energy required to start a reaction -Act via enzyme-substrate complexes: bind to substrates, either break bonds or create new bonds, then release products Sometimes require cofactors = small metals (zinc/iron) Sometimes require coenzymes = small organic molecules (Vitamins) Usually proteins but can also be RNA (aka ribozymes ) Enzymes lower the Activation Energy of Reactions 5

6 Enzymes often act in Metabolic Pathways The product of one enzymatic reaction becomes the substrate for the next reaction i.e. enzymes often work together to put together a final product ATP = Energy Currency -- cannot be stored, must be made and used constantly (short-term) -- utilized in anabolic reactions, often created during catabolic reactions ATP ADP + Phosphate + ENERGY 6

7 ATP/ADP Cycle Metabolic Pathways are coupled to the ATP/ADP Cycle 7

8 High-energy phosphate compounds and Reactions in which they play a role Long-term Energy storage: Polysaccharides, Fats, and Proteins Polysaccs: broken down via glycolysis, krebs cycle, electron transport chains, or fermentation Fats: broken down via Beta-oxidation of fatty acids (products are put into Krebs cycle) Proteins can be broken down via Deamination, products enter the Krebs cycle Focus on.. Sugars 8

9 Two types of glucose transport Glycolysis 9 reactions Initial substrate: glucose (6 carbons) End products: ATP 2 Pyruvates (3 carbon molecule) NADH+ 9

10 The Krebs cycle Sometimes, pyruvate can be processed via the Krebs cycle ~8 reactions Endproducts: ATP NADH+ / FADH 2 Carbon Dioxide Electron Transport Chain: RESPIRATION Requires electrons and protons (carried in by reduced NAD/FAD) Occurs at cell membrane in bacteria, and at mitochondria in eukaryotic cells Can be aerobic if final electron acceptor is Oxygen (Aerobic Oxidative Phosphorylation is shown) Can be anaerobic if final electron acceptor is something other than Oxygen 10

11 Making ATP Structures of molecules involved in oxidation-reduction reactions 11

12 Structures of molecules involved in oxidation-reduction reactions Respiration Aerobic Anaerobic 12

13 Anaerobic respiration examples E. coli : NO 3 - NO 2 - Desulfovibrio:. SO 4-2 H 2 S Methanogens: CO 2 CH 4 {Note that final electron acceptor is reduced} Fermentation Can be used when respiration is not possible Produces some ATP and allows glycolysis to continue Other end products include many acids, gases, and alcohols Example acid: lactic acid Example alcohol: ethanol Example gas: CO2 13

14 Anabolic Process: Photosynthesis -- two stages of reactions -- end product: glucose 1. Energy-fixing reactions: sunlight excites electrons in chlorophyll pigment, energy is captured as ATP and NADPH 2. Carbon-fixing reactions: products of first stage are used to convert carbon dioxide to sugars (glucose) Nutritional Classification of Microorganisms 14

15 The Cycles of Elements in the Environment There s a limited amount of carbon, sulfur, phosphorus, nitrogen, etc. in the biosphere. Therefore, these elements must constantly be recycled to be used by living organisms Who are the recyclers??? Bacteria and Fungi The Carbon cycle 15

16 The Sulfur cycle The Nitrogen cycle N 2 gas in the air Nitrogen needed as part of proteins, DNA, RNA, ATP, etc. When organisms die, bacteria and fungi rerelease N 2 gas back to the atmosphere, completing the cycle Bacteria take it from the air and convert it to ammonia, nitrites, and nitrates that can be used by plants; animals eat the plants 16

17 Interaction of Rhizobium meliloti and alfalfa Interaction of Rhizobium meliloti and alfalfa SUMMARY: In roots of leguminous (pod-bearing) plants, bacteria live in symbiosis with the plant. Plant gets fixed nitrogen from bacs, and in return feeds them sugar and gives them a house 17

18 Root Nodules Leguminous Plant Bacteria: Genetics, Genomics, and Genetic Engineering -- genetics: study of hereditary information -- gene: a section of DNA that encodes an RNA molecule, some of which are used to make proteins 18

19 Bacterial DNA DNA is located in two places in bacteria: 1. chromosome has the genes needed for growth, reproduction, everyday life 2. PLASMIDS, small rings of DNA with genes that confer antibiotic resistance, toxin production, etc Humans have 21,000 genes, E. coli has about 4400, it is wound like a rubber-band (super-coiled) to fit into cells Plasmids 19

20 The Central Dogma of Molecular Biology transcription translation DNA RNA Protein replication DNA replication Start with one chromosome or plasmid, end with two Each of the two parental DNA strands is used as a template to make a new daughter DNA strand Bidirectional: goes both ways around the loop; major enzyme involved is called DNA polymerase (reads template DNA and writes new daughter DNA) Semi-conservative: half of each new chromosome or plasmid is parental, and half is new daughter material 20

21 Transcription -- DNA processed into RNA molecules A. mrna: carries the genetic message to the ribosomes, codons = triplet mrna sequences that code for amino acids B. trna: adaptor molecule that carries amino acids on one side and has anti-codons on the other side that bind to codons C. rrna: forms part of the ribosome, catalyzes reactions there Translation Processes RNA into protein All three RNA types involved Begins at start codon on mrna (AUG) Ends at Stop Codons (UAA/UAG/UGA) Anti-codon of each trna binds to codon on mrna, bringing in the appropriate amino acid to build protein chains 21

22 The Genetic Code Polyribosomes 22

23 Operons and Control of Protein Synthesis Mutations Permanent change in the DNA of an organism; can be beneficial, harmful, or neutral. Does it affect fitness = ability to survive and reproduce??? A. Spontaneous: occurs as a results of errors during replication (1 in a billion base pairs is incorrect) B. Induced: occur due to a physical or chemical agent in the environment. 23

24 Induced mutations UV light binds adjacent Thymine (T) molecules together Re: skin cancer due to too much sunlight exposure T-T dimers can be repaired, but not always, can cause DNA to be unreadable in that location. Result of Mutations 24

25 Types of Point mutations Affect a single base pair in DNA Silent: don t change the amino acid, even if DNA changes; usually neutral Mis-sense: one amino acid changes; can be beneficial, harmful, or neutral Non-sense: inserts early stop codon shorter protein Insertion or Deletion: remove or add one nucleotide; frameshift as all codons after it are changed The Ames test can identify potential mutagens -- used to test household chemicals; -- if bacteria show a mutation, don t use the product!! 25

26 DNA Repair: An Example Genetic Transfer in Bacteria -- vertical: parent to daughter cells; horizontal: between non-related cells V E R T I C A L HORIZONTAL 26

27 Three Types of Horizontal Gene Transfer 1. Transformation: uptake of free DNA from the environment 2. Transduction: viruses transfer DNA between bacteria 3. Conjugation: two bacteria get together and DNA is pushed from one to the other Natural Transformation 27

28 Artificial Transformation Griffith s Discovery of Transformation 28

29 Transduction Conjugation = Bacterial Dating 29

30 Two Types of Conjugation A. B. Horizontal gene transfers make some bacteria more dangerous to humans 30

31 Transposable genetic elements INVERTED REPEATS Discoverer of Transposons Barbara McClintock 31

32 Movement of an antibiotic resistance gene Genetic engineering Manipulation of DNA to make a product Aka Biotechnology Example: use yeast to make Cow Growth Hormone in mass quantity Result: cow s milk contained elevated levels of hormones, may be cancerous 32

33 Restriction Enzymes and Recombinant DNA Restriction enzymes can cut DNA at particular locations DNA ligase pastes together separate DNAs (creates hybrid) Construction of a Recombinant DNA Molecule 33

34 Human genes can be cloned in bacteria Applications of Genetic engineering 34

35 Insert Human gene for insulin production into E. coli bacteria E. coli produces insulin chemically identical to human version Transgenics why does it work? 35

36 PCR: The Polymerase Chain Reaction = a DNA copy machine Microbial Genomics Genomics: study of entire DNA sequences of organisms (e.g. DOG/ CHIMP / HUMAN) -- lets us compare organisms + species to see how closely related they are to each other -- lets us examine sick vs. healthy populations of humans to screen for disorders 36

37 DNA Probes : Useful in diagnosis 37