Final Exam Ch9

Question 1

growth curve phases

Answer 1

lag phase
log phase
stationary phase
death/decline phase

Question 2

lag phase

Answer 2

the initial phase
* small number of cells, a.k.a. the inoculum, are added to a fresh culture medium
* in this phase there is no increase in number of living bacterial cells, although they do grow larger in size and are metabolically active

Question 3

log phase

Answer 3

2nd phase
- * also known as the exponential growth phase
* in this phase, the cells are actively dividing by binary vision, and their number increases exponentially
* cells are sensitive to adverse conditions
* antibiotics can be introduced and are effective
* Persister cells are formed

Question 4

stationary phase

Answer 4

Third Phase
* the number of new cells created by cell division becomes equivalent to the number of dying cells
* cells switch to survival mode of metabolism
* synthesis of peptidoglycan, proteins, and nucleic acids slow down
* cells become less susceptible to antibiotics
* in bacteria which produce endospores, cells may undergo sporulation
* Persister cells increase

Question 5

death or decline phase

Answer 5

last phase
-* Exponential decrease in number of living cells due to accumulation of toxic waste and nutrient exhaustion
-* the number of dying cells exceeds the number of dividing cells
*surviving cells maintain viability and form endospores
*persister cells

Question 6

persisted cells

Answer 6

cells with slow metabolic rate. These cells are important because they are associated with certain chronic infections, like tuberculosis, that do not respond to antibiotic treatment

Question 7

obligate (strict) aerobes

Answer 7

• all the bacteria growth is seen at the top of the tube
• cannot grow without an abundant supply of oxygen (they NEED oxygen)
• use aerobic respiration

Question 8

examples of obligate aerobes

Answer 8

• Mycobacterium tuberculosis: causes tuberculosis
• Micrococcus luteus: a gram-positive bacterium that colonizes the skin
• Neisseria meningitidis: agent of severe bacterial meningitis
• Neisseria gonorrhoeae: agent of sexually transmitted gonorrhea

Question 9

obligate anaerobes

Answer 9

• bacteria growth is seen at the bottom of the tube
• killed by oxygen
• use anaerobic fermentation

Question 10

examples of obligate anaerobes

Answer 10

• • Bacteroidetes: represent a large fraction of the microbes in the human gut
• • Clostridium difficile: major cause of health acquired infections and inflammation of colon
• • C. tetani and C. perfringens: causes gas gangrene (black dead skin)

Question 11

facultative anaerobes

Answer 11

• heavy growth at the top of the tube and growth throughout the tube
• organisms thrive in the presence of oxygen, but also grow in its absence by relying on fermentation or anaerobic respiration
• use both anaerobic and aerobic respiration

Question 12

examples of facultative anaerobes

Answer 12

• Staphylococci: found in the skin and upper respiratory tract
• Enterobacteriaceae: found in the gut and upper respiratory tract but can spread to the urinary tract

Question 13

aerotolerant anaerobes

Answer 13

• indifferent to the presence of oxygen grow evenly distributed across the tube
• do not use oxygen, but they usually have a fermentative metabolism, but they are not harmed by the presence of oxygen as obligate

Question 14

examples of aerotolerant anaerobes

Answer 14

• Lactobacilli: found in oral microbiota
• Streptococci: found in oral microbiota

Question 15

microaerophiles

Answer 15

• known as the “Goldilocks” culture
• oxygen level has to be just right for growth, not too much and not too little
• bacteria that requires a minimum level of oxygen for growth, about 1% to 10%

Question 16

optimum, minimum, and maximum oxygen concentration

Answer 16

*Optimum oxygen concentration: the ideal concentration of oxygen for a particular organism
*Minimum permissive oxygen concentration: lowest concentration of oxygen that allows growth
*Maximum permissive oxygen concentration: highest tolerated concentration of oxygen

Question 17

optimum, minimum, and maximum growth pH

Answer 17

*Optimum growth pH: the most favorable pH for the growth of an organism
*Minimum growth pH: the lowest pH value that an organism can tolerate
*Maximum growth pH: the highest pH value that an organism can tolerate

Question 18

neutrophils

Answer 18

grow optimally at a pH within one or two pH units of the neutral pH of 7 (pH around 5.5-8.5)
* examples: Escherichia coli, staphylococci, and Salmonella spp.

Question 19

acidophiles

Answer 19

microorganism that grow at pH less than 5.55 (optimal growth is at about 3 pH)
* examples: ferroplasma, lactobacillus (bacteria in vagina),
* Helicobacter : causes stomach cancer

Question 20

alkaliphiles

Answer 20

microorganisms that grow best at pH between 8.0 and 10.5
* Examples: Vibrio Cholerae (pathogenic agent of cholera)

Question 21

optimum, minimum, and maximum growth temperature

Answer 21

*Optimum growth temperature: temperature at which the growth rates of the organism are highest
*Minimum growth temperature: lowest temperature at which organisms can survive and replicate
*Maximum growth temperature: the highest temperature at which growth can occur

Question 22

mesophiles

Answer 22

or “middle loving”, are adapted to moderate temperatures, with optimal growth temperature ranging from room temperature (20* C) to about 45C
* since the human body lies at 37C, normal human microbiota and pathogens, like E.coli, Salmonella spp., and Lactobacillus) are mesophiles

Question 23

psychotrophs

Answer 23

aka psychrotolerant, prefer cooler environments, from a high temperature of 25C to refrigeration temperature about 4C
* found in many natural environments in temperature climates
* responsible for the spoilage of refrigerated food
* important decomposers in cold climates

Question 24

psychrophiles

Answer 24

aka “cold loving”, microorganisms that can grow at 0C and below
* optimum growth is 15C
* can not survive at temperatures above 20*C
* found in deep waters of ocean
* important decomposers in cold climates

Question 25

thermophiles

Answer 25

aka “heat loving”, have growth in optimum temperatures of 50*C to a maximum of 80*C * do not multiply at room temp * widely distributed in hot springs, geothermal soils, and manmade environments such as garden compost piles where the microbes break down kitchen scraps and vegetal material

Question 26

hyperthermophiles

Answer 26

characterized by growth ranges from 80*C to a maximum of 110*C * some can survive even higher temperatures

Question 27

halophiles

Answer 27

“salt loving”, require high salt concentration for growth * found in marine environments where salt concentrations hover at 3.5%

Question 28

halotolerant

Answer 28

do not need high concentrations of salt for growth but will survive and divide in the presence of high salt * Halotolerant pathogens are an important cause of food-borne illnesses because they survive and multiply in salty food. * For example, the halotolerant bacteria S. aureus, Bacillus cereus, and V. cholerae produce dangerous enterotoxins and are major causes of food poisoning

Question 29

barophiles

Answer 29

Microorganisms that require high atmospheric pressure for growth * not much is known about these organism because it’s difficult to get ahold of them * bacteria that live at the bottom of the ocean are great examples

Question 30

If a culture starts with 50 cells, how many cells will be present after five generations with no cell death?

Answer 30

* 1600 cells * 50*2*2*2*2*2 =1600

Question 31

In which phase would you expect to observe the most endospores in a Bacillus cell culture?

Answer 31

death phase

Question 32

In which phase of the bacterial growth curve would you be able to introduce antibiotics

Answer 32

log phase

Question 33

In which phase of the bacterial growth curve would the number of dead cells be equal to the number of live cells?

Answer 33

stationary phase

Question 34

How much will a culture be diluted if 1 ml of the cell suspension is added to 999 ml of diluent?

Answer 34

1:1000

Question 35

How much will a culture be diluted if 10 ml of the cell suspension is added to 90 ml of diluent

Answer 35

10^-1

Question 36

A soup container was forgotten in the refrigerator and shows contamination. The contaminants are probably which of the following?

Answer 36

psychrophiles

Question 37

A thioglycollate medium culture tube is clear throughout the tube except for the dense growth at the bottom of the tube. What is your conclusion?

Answer 37

organisms are obligate anaerobes

Question 38

Which of the following best describes how a microaerophile would grow in a thioglycollate tube culture?

Answer 38

* a short distance below the top of the medium, but not at the top

Question 39

An experiment began with 4 cells and ended with 128 cells. How many generations did the cells go through?

Answer 39

* 5 * 4*2*2*2*2*2=128

Question 40

How much will a culture be diluted if 10 ml of the cell suspension is added to 990 ml of diluent?

Answer 40

10^-2

Question 41

What is the function of the Z ring in binary fission

Answer 41

forms contractile ring at the septum