Metabolism

Question 1

Phototrophs

Answer 1

Light for energy

Question 2

Heterotrophs

Answer 2

Organic Carbon for energy

Question 3

Lithotrophs

Answer 3

Inorganic compounds for energy

Question 4

Autotrophs

Answer 4

CO2 for energy

Question 5

Growth factors

Answer 5

small amounts of certain organic compounds for growth because they are essential substances that the organism is unable to synthesize from available nutrients Amino acids, vitamins, and purines/pyrimidines

Question 6

Auxotroph

Answer 6

Mutant strains of bacteria that require some growth factor not needed by the wild type (parent) strain

Question 7

Agar

Answer 7

solidified media are used widely for the isolation of pure cultures, for estimating viable bacterial populations, and a variety of other purposes

Question 8

Liquid Media

Answer 8

Used for pure batch culture growth

Question 9

Defined Media

Answer 9

composed of pure biochemicals off the shelf

Question 10

Complex Media

Answer 10

Chemical composition is unknown, blood, serum, or milk

Question 11

Minimial Media

Answer 11

rovides only the exact nutrients (including any growth factors) needed by the organism for growth. The use of defined minimal media requires the investigator to know the exact nutritional requirements of the organisms in question

Question 12

Selective Media

Answer 12

one which has a component(s) added to it which will inhibit or prevent the growth of certain types or species of bacteria and/or promote the growth of desired species

Question 13

Differential Media

Answer 13

allows the investigator to distinguish between different types of bacteria based on some observable trait in their pattern of growth on the medium

Question 14

Obligate Aerobe

Answer 14

Obligate aerobes require O2 for growth; they use O2 as a final electron acceptor in aerobic respiration.

Question 15

Obligate Anerobe

Answer 15

Obligate anaerobes (occasionally called aerophobes) do not need or use O2 as a nutrient. In fact, O2 is a toxic substance, which either kills or inhibits their growth.

Question 16

Facultative Anerobe

Answer 16

Facultative anaerobes (or facultative aerobes) are organisms that can switch between aerobic and anaerobic types of metabolism

Question 17

Aerotolerant Anerobe

Answer 17

Aerotolerant anaerobes are bacteria with an exclusively anaerobic (fermentative) type of metabolism but they are insensitive to the presence of O2.

Question 18

Effect of pH on growth

Answer 18

Acidophiles, neutrophiles, and alkaliphiles

Question 19

Effect of temperature on growth

Answer 19

psychrophile, mesophile, thrmophile

Question 20

Generation Time

Answer 20

G=t/n n=3.3log(bacteria at end/bacteria at beginning)

Question 21

Prototroph

Answer 21

Can grow on minimal media, produces everything it needs

Question 22

Phases of the bacterial growth curve

Answer 22

Lag Steady State Stationary Death

Question 23

Lag Phase

Answer 23

Immediately after inoculation of the cells into fresh medium, the population remains temporarily unchanged. Although there is no apparent cell division occurring, the cells may be growing in volume or mass, synthesizing enzymes, proteins, RNA, etc., and increasing in metabolic activity

Question 24

Steady State Phase

Answer 24

The exponential phase of growth is a pattern of balanced growth wherein all the cells are dividing regularly by binary fission, and are growing by geometric progression. The cells divide at a constant rate depending upon the composition of the growth medium and the conditions of incubation. The rate of exponential growth of a bacterial culture is expressed as generation time, also the doubling time of the bacterial population. Generation time (G) is defined as the time (t) per generation (n = number of generations). Hence, G=t/n is the equation from which calculations of generation time (below) derive.

Question 25

Stationary Phase

Answer 25

Exponential growth cannot be continued forever in a batch culture (e.g. a closed system such as a test tube or flask). Population growth is limited by one of three factors: 1. exhaustion of available nutrients; 2. accumulation of inhibitory metabolites or end products; 3. exhaustion of space, in this case called a lack of “biological space”.

Question 26

Death Phase

Answer 26

If incubation continues after the population reaches stationary phase, a death phase follows, in which the viable cell population declines. (Note, if counting by turbidimetric measurements or microscopic counts, the death phase cannot be observed.). During the death phase, the number of viable cells decreases geometrically (exponentially), essentially the reverse of growth during the log phase.

Question 27

GASP Phenotype

Answer 27

Growth advantage in stationary phase. Progeny cells will out compete parent cells.

Question 28

Anaerobic respiration

Answer 28

Anaerobic respiration: respiration that uses substances other than O2 as a final electron acceptor

Question 29

Lithotrophy

Answer 29

Lithotrophy: use of inorganic substances as sources of energy

Question 30

Photoheterotrophy

Answer 30

Photoheterotrophy: use of organic compounds as a carbon source during bacterial photosynthesis

Question 31

Anoxygenic photosynthesis

Answer 31

Anoxygenic photosynthesis: photophosphorylation in the absence of O2

Question 32

Methanogenisis

Answer 32

Methanogenesis: an ancient type of archaean metabolism that uses H2 as an energy source and produces methane

Question 33

Light-driven nonphotosynthetic photophosphorylation

Answer 33

Light-driven nonphotosynthetic photophosphorylation: unique archaean metabolism that converts light energy into chemical energy

Question 34

ATP synthesis in prokaryotes (archaea and Bacteria)

Answer 34

Substrate level phosphorylation Electron Transport Phosphorylation

Question 35

ETP

Answer 35

Electron Transport Phosphorylation (ETP) is a much more complicated affair that evolved long after SLP. Electron Transport Phosphorylation takes place during respiration, photosynthesis, lithotrophy and possibly other types of bacterial metabolism. ETP requires that electrons removed from substrates be dumped into an electron transport system (ETS) contained within a membrane. The electrons are transferred through the ETS to some final electron acceptor in the membrane (like O2 in aerobic respiration) , while their traverse through the ETS results in the extrusion of protons and the establishment of a proton motive force (pmf) across the membrane.

Question 36

SLP

Answer 36

Substrate level phosphorylation (SLP) is The simplest, oldest and least-evolved way to make ATP. In a substrate level phosphorylation, ATP is made during the conversion of an organic molecule from one form to another. Energy released during the conversion is partially conserved during the synthesis of the high energy bond of ATP. SLP occurs during fermentations and respiration (the TCA cycle), and even during some lithotrophic transformations of inorganic substrates.

Question 37

Fermentation

Answer 37

Fermentation is an ancient mode of metabolism, and it must have evolved with the appearance of organic material on the planet. Fermentation is metabolism in which energy is derived from the partial oxidation of an organic compound using organic intermediates as electron donors and electron acceptors. No outside electron acceptors are involved; no membrane or electron transport system is required; all ATP is produced by substrate level phosphorylation.

Question 38

The Embden-Meyerhof Pathway

Answer 38

The first three steps of the pathway prime (phosphorylate) and rearrange the hexose for cleavage into 2 trioses (glyceraldehyde-phosphate). Fructose 1,6-diphosphate aldolase is the key (cleavage) enzyme in the E-M pathway. Each triose molecule is oxidized and phosphorylated followed by two substrate level phosphorylations that yield 4 ATP during the pathway to pyruvate. Lactic acid bacteria reduce the pyruvate to lactic acid (lactate); yeast reduce the pyruvate to alcohol (ethanol) and CO2

Question 39

The Heterolactic (Phosphoketolase) Pathway

Answer 39

The phosphoketolase pathway (Figure 11) is distinguished by the key cleavage enzyme, phosphoketolase, which cleaves pentose phosphate into glyceraldehyde-3-phosphate and acetyl phosphate. In this pathway, glucose-phosphate is oxidized to 6-phosphogluconic acid, which becomes oxidized and decarboxylated to form pentose phosphate. Unlike the Embden-Meyerhof pathway, NAD-mediated oxidations take place before the cleavage of the substrate being utilized. Pentose phosphate is subsequently cleaved to glyceraldehyde-3-phosphate (GAP) and acetyl phosphate. GAP is converted to lactic acid by the same enzymes as the E-M pathway. This branch of the pathway contains an oxidation coupled to a reduction while 2 ATP are produced by substrate level phosphorylation. Acetyl phosphate is reduced in two steps to ethanol, which balances the two oxidations before the cleavage but does not yield ATP. The overall reaction is Glucose ———->1 lactic acid + 1 ethanol +1 CO2 with a net gain of 1 ATP. The efficiency is about half that of the E-M pathway.

Question 40

The Entner-Doudoroff Pathway

Answer 40

The E-D pathway yields 2 pyruvic acid from glucose (same as the E-M pathway) but like the phosphoketolase pathway, oxidation occurs before the cleavage, and the net energy yield is one mole of ATP per mole of glucose utilized.

Question 41

TCA

Answer 41

The tricarboxylic acid (TCA) cycle (also known as the citric acid cycle or the Kreb’s cycle): when an organic compound is utilized as a substrate, the TCA cycle is used for the complete oxidation of the substrate. The end product that always results from the complete oxidation of an organic compound is CO2.

Question 42

Electron transport Chain

Answer 42

A membrane and an associated electron transport system (ETS). The ETS is a sequence of electron carriers in the plasma membrane that transports electrons taken from the substrate through the chain of carriers to a final electron acceptor. The electrons enter the ETS at a very low redox potential (E’o) and exit at a relatively high redox potential. This drop in potential releases energy that can be harvested by the cells in the process of ATP synthesis by the mechanisms of electron transport phosphorylation. The operation of the ETS establishes a proton motive force (pmf) due to the formation of a proton gradient across the membrane.

Question 43

Methanogenisis

Answer 43

the primary source of methane (natural gas) on the planet. Methane is preserved as a fossil fuel (until we use it all up) because it is produced and stored under anaerobic conditions, and oxygen is needed to oxidize the CH4 molecule. Methanogenesis is not really a form of anaerobic respiration, but it is a type of energy-generating metabolism that requires an outside electron acceptor in the form of CO2. CO2 is the electron acceptor CH4 is the reduced product

Question 44

Dentrification

Answer 44

The use of nitrate as a respiratory electron acceptor is usually an alternative to the use of oxygen NO3 is the electron acceptor NO2, N2O2, or N2 is the reduced product

Question 45

Sulfate Reduction

Answer 45

an obligatory process that occurs only under anaerobic conditions. Methanogens and sulfate reducers may share habitat, especially in the anaerobic sediments of eutrophic lakes such as Lake Mendota, where they crank out methane and hydrogen sulfide at a surprising rate. SO4 is the electron acceptor S or H2S is the reduced product

Question 46

Homolactic Fermentation

Answer 46

Lactic acid is the sole end product. Pathway of the homolactic acid bacteria (Lactobacillus, Lactococcus and most streptococci). The bacteria are used to ferment milk and milk products in the manufacture of yogurt, buttermilk, sour cream, cottage cheese, cheddar cheese, and most fermented dairy products.

Question 47

Mixed Acid Fermentations

Answer 47

Mixed Acid Fermentations. Mainly the pathway of the Enterobacteriaceae. End products are a mixture of lactic acid, acetic acid, formic acid, succinate and ethanol, with the possibility of gas formation (CO2 and H2) if the bacterium possesses the enzyme formate dehydrogenase, which cleaves formate to the gases.

Question 48

Butanediol Fermentation.

Answer 48

Butanediol Fermentation. Forms mixed acids and gases as above, but, in addition, 2,3 butanediol from the condensation of 2 pyruvate. The use of the pathway decreases acid formation (butanediol is neutral) and causes the formation of a distinctive intermediate, acetoin. Water microbiologists have specific tests to detect low acid and acetoin in order to distinguish non fecal enteric bacteria (butanediol formers, such as Klebsiella and Enterobacter) from fecal enterics (mixed acid fermenters, such as E. coli, Salmonella and Shigella).

Question 49

Propionic acid fermentation

Answer 49

Propionic acid fermentation. This is an unusual fermentation carried out by the propionic acid bacteria which include corynebacteria, Propionibacterium and Bifidobacterium. Although sugars can be fermented straight through to propionate, propionic acid bacteria will ferment lactate (the end product of lactic acid fermentation) to acetic acid, CO2 and propionic acid. The formation of propionate is a complex and indirect process involving 5 or 6 reactions. Overall, 3 moles of lactate are converted to 2 moles of propionate + 1 mole of acetate + 1 mole of CO2, and 1 mole of ATP is squeezed out in the process. The propionic acid bacteria are used in the manufacture of Swiss cheese, which is distinguished by the distinct flavor of propionate and acetate, and holes caused by entrapment of CO2.