Microbiology Exam 2

Fermentation

process utilizing glycolysis to produce ATP

Ethanol Fermentation

Process: pyruvate to acetaldehyde + CO2 to ethanol to NADH to NAD

Example: utilized by yeast in the absence of oxygen.

• CO2 allows bread to rise

• ethanol for the production of beer and wine

Lactate Fermentation

Process: pyruvate to lactate to NADH to NAD

Example: utilized in food production such as sour cream, yogurt, sauerkraut, pickles, and kimchi.

• Lactobacillus sp. and Streptococcus sp.

Mixed Acid

Process: pyruvate to formate to H2 + CO2 to NADH to NDA

Example: Escherichia Coli, “E. Coli”

Butanediol

Process: pyruvate to acetoin to 2,3 butanediol to NADH to NDA

Example: Enterobacter Aerogenes

Krebs Cycle

Definition: repetitive cycle involving 9 carbon compounds

Process: Acetyl group ( 2 carbons) + oxaloacetic acid ( 4 carbons) to citric acid ( 6 carbons) to 7 steps to oxaloacetic acid, NADH + 1 FADH2 formed per acetyl group, 1 GTP formed per acetyl group, releases CO2.

Glyoxylate Cycle

Definition: catabolism of C2-C3 organic acids typically involves production of oxaloacetate (precursor of amino acids and glucose) through the glyoxylate cycle. 

Process: Sum- Isocitrate + Acetate to Succinate(precursor of biosynthesis) + Malate

• Acetyl-CoA: necessary for fatty acid biosynthesis

Electron Transport

Process: utilizes NADH and FADH2 formed in previous steps. Electrons are released to electron transport system and provide energy for active transport  of H+ ions from matrix to outside of membrane to form a membrane potential. Movement of H+ ions down concentration gradient provides energy to make ATP from ADP and Pi.

Aerobic Respiration

Process:

   1. Glycolysis + 2NAD+ to 2 pyruvate + 2 ATP + 2 NADH

2. CAC: pyruvate + 4 NAD+ GDP + FAD to 3 CO2 + 4 NADH + FADH2 + GTP (ATP)

3. Sum: Glycolysis + CAC to 38 ATP per glucose.

Anaerobic Respiration

Definition: the use of electron acceptors other than oxygen. Dependent on electron transport, proton motive force, and ATPase Activity.

Processes: Nitrate to nitrogen gas - NO3- to N2O to N2 

Sulfate to Hydrogen Sulfide - SO42- to S to H2S

Fumarate to Succinate (TCA Cycle)

Carbon Dioxide to Methane - CO2 to CH4

Fe+3 to Fe+2

Anaerobic Respiration Examples

Nitrate to Nitrogen gas; Facultative anaerobes; Bacillus sp.

Sulfate to Hydrogen Sulfide; Strict anaerobe; Desulfovibrio sp.

Fumarate to Succinate; E.Coli, Proteus sp.

Carbon Dioxide to Methane; Methanobacter sp., Methanococcus sp. ( found in GI tract)

Fe+3 to Fe+2; Acidophillic; Thiobacillus feroxidans

Chemolithotrophy

uses inorganic chemicals as electron donors

aerobic

begins with oxidation of inorganic electron donor

uses electron transport chain and proton motive force 

Autotrophic; uses CO2 as a carbon source

Phototrophy

Definition: uses light as energy source

• photophosphorylation: light-mediated ATP synthesis

• Photoautotrophs: use ATP for assimilation of CO2 for biosynthesis

• Photoheterotrophs: use ATP for assimilation of organic carbon for biosynthesis

Carbohydrate Catabolism

Cellulose to glucose

• Enzyme: cellulase

• Organisms: Clostridium sp. and Actinomyces sp.

Starch to glucose

• Enzyme: amylase

• Organism: Bacillus subtilis

Lactose to glucose + galactose

• Enzyme: galactosidase

• Organism: E. Coli

Lipid Catabolism

Triglycerides to glycerol + fatty acids

• Enzymes: lipase

• Organisms: Bacillus subtilis and Staphylococcus aureus

• Media: spirit blue agar

Phospholipids to Phosphorylcholine + fatty acids

• Enzyme: Phospholipase

• Organism: Clostridium perfringens

• Hemolytic ( gas Gangrene)

• Media: Egg yolk agar

Fatty Acids 

• Beta Oxidation

• Co A, FAD, NAD converted to Acetyl Co A, FADH and NADH

Protein Catabolism

Protein to amino acids

• Enzyme: protease

• Organism: Serratia marcescens

• Media: Skim milk agar

Amino acid metabolism

• Dehydrogenase: removes or adds ammonia

• Synthetase: adds ammonia

• Transaminase: transfers ammonia

• Synthase: transfers ammonia

Gluconegenesis

Definition: Synthesis of glucose from phosphoenolpyruvate

Process: Citric acid cycle to Oxalacetate to Phosphoenolpyruvate + CO2 to Glucose-6-P

Pentose Phosphate Pathway

Definition: Pentoses for nucleic acids formed from decarboxylating glucose.

Biosynthesis of Sugars

Definitions: Adenosine diphosphoglucose (ADPG)- precursor for glycogen biosynthesis

• Uridine diphosphoglucose (UDPG)- precursor of some glucose derivatives needed for biosynthesis of important polysaccharides 

• Examples: N-acetylmuramic acid , N-acetylglucosamine

Biosynthesis of Amino Acids

Definition: Carbon skeleton comes from Krebs cycle or glycolysis

Ammonia comes from dehydrogenase(removes or adds ammonia), synthetase(adds ammonia), transaminase, and synthase( transfers ammonia)

Biosynthesis of Fatty Acids

Definintion: fatty acids made 2 carbon atoms at a time, requires Acyl carrier protien (ACP), requires NADPH

Nucleotide Anabolism

Synthesis of pentose sugar: phosphogluconate, pentose phosphate pathways and hexose monophosphate

Pyrimidine Biosynthesis: Ortic acid precursor, activated ribose added, UMP Intermediate, products are CTP and TMP

Purine Biosynthesis: amino acids, CO2, and formyl groups (added with help of folic acid), Inosinic acid (IMP) intermediate, AMP and GMP are formed from IMP

Inhibitors of Nucleotide Synthesis

Definition: Methotrexate, aminopterin- inhibits tetrahydrofolate to TMP

6-mercaptopurine- inhibits conversion of IMP to AMP

5-fluoropyrimidine- blacks conversion on UMP to TMP

Sulfonamides- block folic acid synthesis

Microbial Nutrition

Nutrients: supply of monomers required by cells for growth

Macronutrients: carbon, nitrogen, phosphorus, sulfur, potassium, magnesium, calcium, and sodium

Micronutrients: Iron; growth factors: organic compounds required in small amounts by certain organisms ex) vitamins, amino acids, purines, pyrimidines

Enriched Media

contains complex media plus additional nutrients

Differential Media

allows multiple types of bacteria to grow but displays visible differences in how they grow

Selective Media

inhibits the growth of bacteria

Turbidity

Definition: a clear nutrient solution becomes turbid or cloudy as microbes grow in it

Process: greater the turbidity, the larger the population

Direct cell count

Measured microscopically

coulter counter and flow cytometer

Coulter counter

electronically scans a fluid as it passes through a tiny pipette

Flow Cytometer

Coulter counter but can measure cell size and differentiate between live and dead cells

Probable Number Method

Statistical method for measuring bacteria in liquid

used when bacteria can nit grow on agar

Growth Curve

the tendency for populations to exhibit phases of rapid growth, slow growth, and death has implications in microbial control, food microbiology, and culture technology

Temperature: growth effects

Freezing may not kill a cell

dry cells are more heat resistant than most cells

Membrane fatty acid composition and protein composition differ with temperature requirements

Stenothermal

grows in a narrow temeperature range

Eurythermal

grows in a wide temperature range

Water: growth effects

organsims have to extract water from enviorment

Osmotolerant: xeromyces sp.

Osmophillic: saccharomyces sp.

Halotolerant: staphylococcus aureus

Halophillic: vibrio sp. , halobacterium sp.

pH: growth effects

each organism has a pH optium

Acidophiles like low pH: Thiobacillus sp., fungi, yeast

Alkaliphiles like high pH: Natonomonas sp., fungi, yeast

Oxygen: growth effects

Aerobic: requires oxygen

Obligate Anaerobic oxygen toxic

Facultative anaerobe: uses osygen

Microaerophillic: requires oxygen but at lower than atmospheric levels

Aerotolerant anaerobes: do not use oxygen

Carbon dioxid : growth effects

Canophiles: organisms that grow best at a higher CO2 tension than is normally present in the atmosphere

Imporatance for; neisseria, brucella, streptococcus

Pressure: growth effects

Barophiles: exist under pressures that range from a few times to over 1,000 times the pressure of the atmosphere ( will rupture when exposed to normal atmospheric pressure

Heat: physical control

Heat sterilization:

• Incineration

• Dry heat oven

• Autoclave

Measuring: thermal death time, thermal death point, decimal reduction time

Pasteurization: physical control

Kills pathogenic bacteria (mesophiles) 

63 degrees celsius for 30 min

Flash pasteurization: 72 degrees celcius for 15 sec

Ultrapasteurization: 82 degrees celsius for 3 sec

Filtration: physical control

Inorganic filter: Seitz

Organic filter: Berkefield filter

Membrane filter: millipore or Nalgene filter