Ch 6 Microbial Growth

Question 1

what are psychrophiles

Answer 1

cold-loving microbes, grow at coldest temps, can grow below freezing (below 0C)optimum=12-15 C

Question 2

what are mesophiles

Answer 2

moderate-temperature loving, optimum=37C

Question 3

what are psychrotrophs

Answer 3

cant grow below 0C unlike psychrophiles, optimum=

22C

Question 4

these 2 bacterial groups cannot cause infection bc they only survive at temperatures below body temp

Answer 4

psychophiles and psychrotrophs

Question 5

all bacteria that cause infections are in this temp based group

Answer 5

mesophiles

Question 6

this group of microbes is common in low temp food spoilage bc grows well in refrigerator temp

Answer 6

psychrotrophs

Question 7

what are thermophiles

Answer 7

capable of growth at high temps, (opt 62C), seen in hot springs

Question 8

what are hyperthermophiles

Answer 8

archaea opt- 80+C, seen in deep sea events that are under pressure or hot springs

Question 9

importance of heating and cooling in food preservation

Answer 9

heat to a certain point to kill most microbes, cool to prevent more growth, in between is “danger zone”(15-52C)

Question 10

why small containers of food are better than large for refridgeration

Answer 10

temp drops faster, goes thro danger zone quicker

Question 11

optimum pH range for most bacteria

Answer 11

6.5-7.5

Question 12

difference between autotrophs and heterotrophs in terms of C

Answer 12

autotrophs get CO2 from atmosphere

heterotrophs from other organisms

Question 13

why bacteria need Carbon

Answer 13

C is structural backbone of living matter, needed for organic compounds that make up cell

Question 14

why microbes need Nitrogen

Answer 14

synthesis of protein (form the amino group of amino acids in proteins), DNA/RNA, ATP

Question 15

why microbes need sulfur

Answer 15

synthesize amino acids (therefore important in protein synthesis), makes vitamins such as thiamine and biotin

Question 16

why microbes need phosphorus

Answer 16

essentilal for phospholipids of cell membranes, ATP, and synthesis of nucleotides (sugar-phosphate backbone of DNA)

Question 17

these 2 trace elements are needed as cofactors for enzyme functioning

Answer 17

zinc, molybdenum , copper, and iron

Question 18

why O2 is toxic for many organisms

Answer 18

in first 2 billion years on earth v little molecular oxygen, O2 is a powerful oxidizer (strips e- from others) causing metabolic problems

Question 19

what bacteria have evolved to produce to reduce toxic effects of O2

Answer 19

enzymes Catalase and superoxide dismutase

Question 20

catalase v. superoxide dismutase

Answer 20

Catalase neutralizes H2O2 (2H2O2–> O2 +2H2O)
superoxide dismutase=
2O2- (superradical) + 2H+–>O2 + H2O2
converts superradical into molecular O2

Question 21

what are obligate aerobes

Answer 21

require O2

Question 22

what are facultative anaerobes

Answer 22

prefer O2 but can grow without it (switch to anaerobic resp) but efficiency decreases

Question 23

what are obligate anaerobes

Answer 23

only use anaerobic respiration

Question 24

how catalase and superoxide dismutase work in conjunction

Answer 24

SOD converts superradical O2- into O2 producing H2O2 as a byproduct
catalase neutralizes this H2O2

Question 25

what are aerotolerant anaerobes

Answer 25

only anaerobic but continue even in presence of O2 (tolerate it, but don't use it)

Question 26

difference between culturing obligate anaerobes and aerotoleant anaerobes

Answer 26

obligate need special techniques so no O2 is present , aerotolerant dont bc they can tolerate the presence of O2

Question 27

many aerotolerant bacteria produce

Answer 27

lactic acid via fermentation

Question 28

what are micoaerophiles

Answer 28

aerobic, cant tolerate too much or too little O2 (grow in O2 concentrations lower than that of air

Question 29

what makes up the slime portion (matrix in which bacteria reside) of biofilms

Answer 29

primarily polysaccharides and some DNA and proteins

Question 30

why quorum sensing important

Answer 30

allows bacteria to coordinate their activity and group together into communities they also share nutrients, and are sheltered from environment, may also transfer genetic info between each other (conjugation)

Question 31

biofilms are not just slime layers they are

Answer 31

biological systems

Question 32

how a biofilm begins

Answer 32

a planktonic, free-swimming bacteria attaches to a surface

Question 33

how biofilms avoid lack of nutrients at lower depths and buildup of toxic waste

Answer 33

form pillar-like structures with channels thro which water can carry incoming nutrients and outgoing wastes. (like a circulatory system)

Question 34

how a biofilm extends

Answer 34

individual planktonic bacteria leave and move to new location

Question 35

situations in which biofilms are importants

Answer 35

in rumen of ruminants to breakdown cellulose, also essential in sewage treatment systems

Question 36

__% of human bacterial infections involve biofilms, they are (more or less) resistant to antibiotics

Answer 36

70%, more resistant

Question 37

most nosocomial infections are caused by

Answer 37

biofilms on catheters

Question 38

our latest approach to preventing biofilm formation is

Answer 38

incorporating antibiotics into surfaces in which biofilms might form. or finding a way to block quorum sensing.

Question 39

difference between selective and differential media (medium= subs used to grow bacteria)

Answer 39

selective- supress growth of unwanted bacteria, encourage growth of desired differential- allow distinguishing of types of bacteria

Question 40

a pH sensitive indicator is an example of what kind of medium

Answer 40

differential

Question 41

what are the 4 phases of the bacterial growth curve

Answer 41

Lag, Log, stationary, and death phase

Question 42

bcterial growth curve: period of little- no cell division, intense activity preparing for pop growth (like replicating DNA)

Answer 42

1)Lag phase

Question 43

bacterila growth curve: period of growth (logarithmic or exponential), generation time consistent

Answer 43

2) Log phase

Question 44

bacterial growth curve: growth rate slows, number of deaths= number of new cells (equilibrium)

Answer 44

3) stationary phase

Question 45

bacterial growth curve: number of deaths exceed the number of new cells, population decreases at logarithmic rate

Answer 45

4) death phase

Question 46

how to use a serial dillution to count bacteria

Answer 46

take an innoculation dilute into inceasing dilutions (1:10, 1:100, 1:1000, etc.) until # of CFUs is reasonable to count

Question 47

how to calculate # of cells after counting one of its serial dilutions

Answer 47

of cells x dillution factor

Question 48

optimal pH range for molds and yeasts

Answer 48

5-6

Question 49

complex media v. chemically defined media

Answer 49

chem defined: exact contents are known, good for growing bacteria w specific requirements complex: unknown contents, made of nutrients from extracts from yeasts, meat etc. (ex: peptone (partially digested proteins, beef extract, etc.)

Question 50

a basic microbiology lab would be what biosafety level

Answer 50

1

Question 51

our lab (one that involves sterile technique) is which biosafety level

Answer 51

2