fundamentals of microbial growth

Question 1

cell division that produces new (daughter) cells and increases the total cell population.

Answer 1

microbial growth

Question 2

examples of bacteria where biofilm formation complicates treatments.

Answer 2

Methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus species, Clostridium difficile, and Pseudomonas aeruginosa

Question 3

before dividing by binary fission

Answer 3

a prokaryotic cell replicates its chromosome so that each new daughter cell receives a complete copy of the cell’s genetic information. Then the parent cell begins to pinch off at the middle, with ribosomes and other cell components migrating to each end. Finally, the partition (septum) in the center becomes complete, creating two genetically identical daughter cells.

Question 4

For most prokaryotes, this involves dividing a single cell into two cells via the asexual process called

Answer 4

binary fission

Question 5

(strep arrangements) form if binary fission occurs

Answer 5

in one linear plane,

Question 6

clusters (staph arrangements) develop from fission occurring in

Answer 6

multiple planes

Question 7

Certain fungi and some bacteria such as Hyphomicrobium reproduce this way.? in bacteria involves the original cell elongating and developing a small outgrowth on one side.

Answer 7

Budding

Question 8

Both binary fission and budding

Answer 8

asexual, leading to genetically identical cells

Question 9

Some fungi and even bacteria useor reproduction. In fungi, spore formation can be sexual or asexual, while in bacteria it is asexual

Answer 9

spore formation

Question 10

These common soil bacteria form spores called ? that hang off of long hyphae extensions. Eventually the ?, which are the bacterial daughter cells, break off (Fig.

Answer 10

conidia

Question 11

The time it takes for a particular species of cell to divide is its

Answer 11

generation time

Question 12

Bacterial generation times are diverse and can range from about

Answer 12

15 minutes to 24 hours or more,

Question 13

as bacteria divide boy Binary fission Describes a type of growth in which one cell begets two, the two yield four, those four become eight, and so on

Answer 13

exponential

Question 14

the generation time for many common bacteria is

Answer 14

less than an hour

Question 15

Under ideal conditions what’s e.coli generation time

Answer 15

20 minutes

Question 16

This means that every 20 minutes the population would

Answer 16

double

Question 17

Mycobacterium tuberculosis cultured under optimum lab conditions has a ? generation time, mainly because it is hard for nutrients to cross the waxy mycolic acid layer in these bacteria

Answer 17

15 to 20 hour

Question 18

first phase of a standard bacterial growth curve: occurs while bacterial cells adjust to their new environment. During this phase, cells alter their gene expression in response to their new setting. Population growth is not usually seen in this phase .

Answer 18

lag phase

Question 19

second growth phase of bacteria, characterized by an upward-sloped line that results when the number of viable cells is plotted on a logarithmic scale as a function of time.lasts as long as sufficient nutrients are available and metabolic wastes are not appreciably accumulating

Answer 19

logarithmic phase

Question 20

Cells with a rapid generation time will exhibit a sharper slope on a growth graph for this phase than cells with a slower generation time.

Answer 20

logarithmic phase

Question 21

the population growth rate slows and eventually levels off as the number of cells dying matches the number of cells dividing

Answer 21

stationary phase

Question 22

The is also the stage in which bacteria that can form endospores, such as Bacillus and Clostridium species, will gear up to do so.

Answer 22

stationary phase

Question 23

At a critical point of waste buildup and decreasing nutrients, the cells begin to die. During the ? the rate of cell death is exponential and varies based on the starting factors and species being grown.

Answer 23

death phase

Question 24

fresh growth medium is added at one end of the culturing device, while waste, nutrient-depleted medium, and excess cells are removed at another end of the system to maintain a constant culture volume

Answer 24

chemostat system

Question 25

Increased temperature can speed up enzymatic reactions and thereby increase growth rate, but once temperature rises too high, cell proteins ?, killing the cell.

Answer 25

denature

Question 26

reduce enzyme activity and slow growth.

Answer 26

when temp are too low

Question 27

represent the upper and lower temperatures that support a given microbe’s growth.

Answer 27

maximum and minimum temperatures

Question 28

Within the minimum and maximum range there is an ?; this is the temperature where cellular growth rate is highest.

Answer 28

optimal temperature

Question 29

can thrive between about −20°C and 10°C. These organisms tend to live in environments that are consistently cold, like the Arctic.

Answer 29

Psychrophiles

Question 30

grow at about 0–30°C, and are associated with foodborne illness because they grow at room temperature as well as in refrigerated and frozen foods.

Answer 30

psychrotrophs

Question 31

is an example of a psychrotroph; this pathogen readily grows in refrigerated foods and can contaminate meat and fruit to cause food infections.

Answer 31

Listeria monocytogenes

Question 32

prefer moderate temperatures and tend to grow best around 10°–50°C, a range that includes body temperature

Answer 32

mesophiles

Question 33

most pathogens are

Answer 33

mesophiles

Question 34

prefer warm temperatures of roughly 40–75°C. They dwell in compost piles and hot springs

Answer 34

thermophile

Question 35

They prefer growth temperatures from 65–120°C. These organisms can live in boiling water and volcanic vents. S

Answer 35

extreme thermophile

Question 36

some strains of ? can even survive temperatures of up to 122°C (about 251°F).

Answer 36

Methanopyrus kandleri

Question 37

bacteria that can withstand high barometric pressure environments such as occurs in deep seas.

Answer 37

barophile

Question 38

being the favored pH level for growth.

Answer 38

optimum ph

Question 39

can grow at pH 1 (or less) to pH 5, and live in areas such as sulfur hot springs and volcanic vents.

Answer 39

acidphiles

Question 40

lack double bonds in their hydrocarbon tail structures. Saturated lipids stack and pack together, which means membranes enriched with them are solid at cooler temperatures and fluid at warmer temperatures.

Answer 40

saturated lipids

Question 41

grow best in a pH range of 5–8. They make up the majority of microorganisms, especially pathogens, known today. These include Escherichia coli, Salmonella bacteria, and Staphylococcus aureus.

Answer 41

Neutralophiles

Question 42

are microbes that grow in the basic pH range of 9–11. They live in areas of the world that have extremely basic pH conditions, such as soda lakes that contain high concentrations of sodium carbonate.

Answer 42

Alkaliphiles

Question 43

is a measure of acidity or alkalinity. It is based on the concentration of H+ (hydrogen proton concentration). The lower the pH value, the higher the H+ concentration. A pH below 7 is acidic; a pH above 7 is basic; and a pH of exactly 7 is neutral. Acids lower pH and bases raise pH. When cells are described as “pumping protons” to manage pH, they are actually moving H+ ions.

Answer 43

ph

Question 44

Some organisms thrive in high-salt environments and are called

Answer 44

halophiles

Question 45

a situation in which water is drawn out of their cytoplasm into the solute-rich environment

Answer 45

plasmolysis

Question 46

Organisms such as Staphylococcus aureus that tolerate higher solute concentrations but may not grow especially well in them are called

Answer 46

facultative halophiles

Question 47

organisms that live in extremes of pH, temperature, and/or salt, are exposed to a combination of stresses

Answer 47

extremophiles

Question 48

For example, some psychrophiles live in saltwater veins found in arctic ice because the high salt prevents the water from freezing. Consequently, these microbes would be halophiles as well as psychrophiles, so they are called

Answer 48

halo-psychrophiles

Question 49

Pathogens are not usually found in extreme environments and instead prefer body temperature and neutral tissue and blood pH. Thus, pathogens are typically considered

Answer 49

mesophilic neutralophiles

Question 50

These reactive intermediates include superoxide ions (O−2) and hydrogen peroxide (H2O2), both of which can rapidly damage cellular proteins and DNA.

Answer 50

reactive oxygen species (ROS)

Question 51

Many microbes have evolved ways to detoxify ROS so that they can safely use oxygen in their metabolism; such organisms are said to be

Answer 51

aerobes

Question 52

they have an absolute dependence on oxygen for cellular processes, and will die unless it is abundant

Answer 52

obligate aerobes

Question 53

what type of aerobe are we

Answer 53

obligate aerobes

Question 54

use only small amounts of atmospheric oxygen and live in low-oxygen settings where they can limit their exposure to ROS while still meeting their oxygen needs.

Answer 54

microaerophiles

Question 55

is the net movement of water from an area of low solute (salt, sugar, or other dissolved substance) concentration to an area of higher solute concentration across a selectively permeable membrane. It does not require energy to occur. Cells experience osmotic stress when they are placed in environments where their water balance is disrupted.

Answer 55

osmosis

Question 56

Organisms that do not use oxygen in their metabolic processes are

Answer 56

anaerobes

Question 57

they tolerate atmospheric oxygen, even though they do not use it in their metabolic processes

Answer 57

aerotolerant anaerobes

Question 58

do not use oxygen in their metabolism and they tend to die in aerobic environments because they can’t eliminate ROS

Answer 58

obligate anaerobes

Question 59

group of microbes that spans both aerobic and anaerobic environments; can use oxygen for their metabolism but if needed they can perform anaerobic metabolism when oxygen is absent

Answer 59

facultative anaerobes

Question 60

are required to build new cells and can be found in the organic and inorganic compounds of a microbe’s environment.

Answer 60

essential nutrients

Question 61

A Maryland woman was hospitalized with dehydration; Vibrio cholerae and Plesiomonas shigelloides were isolated from the patient. She had neither traveled outside the United States nor eaten raw shellfish during the preceding month. She had attended a party 2 days before her hospitalization. Two other people at the party had acute diarrheal illness and elevated levels of serum antibodies against Vibrio. Everyone at the party ate crabs and rice pudding. Crabs left over from this party were served at a second party. None of the 20 people at the second party had became ill. This is an example of: ? transmissionWhat is the etiologic agent of the disease? What is the etiologic agent of the disease? What was the source of the disease?

Answer 61

vehicle, Vibrio cholerae, rice pudding