chapter 4 microbial growth

Question 1

bacterial growth refers to increase in bacterial cell numbers or does it refer to the increase of size of individual cells?

Answer 1

it refers to the increase in bacterial cell numbers

Question 2

how do most bacteria reproduced ?

Answer 2

most of them reproduce by binary fission

Question 3

define the characteristics of bacteria cell

Answer 3

elongates and makes a copy of its DNA, divides into two identical cells which we call the daughter cells.

Question 4

exponential growth:
As we re-call bacteria divide by binary fission, what does this indicate for the population of cells ?

Answer 4

it will double every generation

Question 5

what is the term called for the time required for population to double?

Answer 5

it is called generation time

Question 6

what are the two terms that we use in a bacterial growth in a lab and define what they mean

Answer 6

culture and inoculation

culture= microbes growing in a medium
inoculation: introducing microbes into a medium to start a culture

Question 7

define what batch culture mean

Answer 7

it is a closed system, once it is started there are no other nutrients that could be added, when nutrients are used up-bacteria stop growing

Question 8

define what continuous culture mean

Answer 8

it is an open system, nutrients are continuously added, wastes are continuously removed, this supports indefinite growth

Question 9

name the growth curve in batch culture

Answer 9

lag phase
exponential phase
stationary phase
death phase
phase of prolonged decline

Question 10

define what exponential phase and the other term for it.

Answer 10

another term is log phase, and it is a the period of maximal production-cells numbers increase exponentially, this is used to calculate generation time.

Question 11

define what lag phase is.

Answer 11

this is how bacteria will grow in batch culture, slow and steady. A period of adaptation (may take some time so they can start binary efficient).

Cells adjust to new media and get ready to grow

Question 12

define what the term death phase is.

Answer 12

toxic waste products have accumulated(gathered), in visuals (decreased rapidly .)
the cells die at a uniform rate

Question 13

define what the phase of prolonged decline is.

Answer 13

sometimes a small fraction of population survives the death phase, they may consume nutrients released from dying cells
- selects for the strongest cells in the population

Question 14

define what stationary phase is

Answer 14

cells have reached maximal population density
nutrients have bee used up, waste have accumulated and no increase in cell number.

Question 15

environmental factors that influence bacterial growth:
temperature requirements:
Define if it true or false.
Each species of microbe has its own specific temperature range, and this range usually spans abut 30 degrees.

Answer 15

true

Question 16

define the following terms: What do they mean?

minimum
optimum
maximum

Answer 16

minimum - lowest temp supporting growth
optimum-temperature that supports best growth
maximum-highest temp supporting growth

Question 17

what’s the temperature that supports the best growth?

Answer 17

optimum

Question 18

bacteria can be grouped based on temperature range name the following terms

Answer 18

psychrophiles
psychrotrophs
mesophiles
thermophiles
hyperthermophiles

Question 19

define what mesophiles are. also include its
min
max
optimum

Answer 19

moderate temperature loving, they are the ones that causes disease , and our body temp is 37, most bacteria are mesophiles, and most pathogens have temp optimum of 37 degrees

min= about 10 degrees
max: about 45 degrees
optimum = 25-45

Question 20

define what psychrophiles are.

Answer 20

cold loving and grow between -5 and about 15c , they are killed at 20 degrees.

Question 21

what are psychrotrophs?

Answer 21

have a very broad temp range
min is about -5
max is about 30-45
optimum is 15-30
these are the microbes that cause food to spoil in your fridge

Question 22

define what thermophiles are

Answer 22

heating loving, and the min is about 40 degrees, and the max is 80 and the optimum is about 65.

Question 23

what are hyperthermophiles , include the min, max, and optimum.

Answer 23

restricted to very few places on earth where water reaches these temperatures , an example would be deep ocean vents, min is 75 and the max is up to 121.

Question 24

this involves the use of both hot and cold temperatures

Answer 24

food safety both involve the hot and cot temperature

Question 25

heat is used to kill ____ and ____ microbes such as cooking.

Answer 25

mesophilic, and pyschrotophic

Question 26

what temperature is used to slow growth?

Answer 26

cold temperature, and only psychroprophs will grow in refrigerator and slowly.

Question 27

oxygen can be toxic to other and only requirement by some organisms.

Answer 27

true

Question 28

define what obligate aerobes

Answer 28

require 02 for respiration (energy genration)

Question 29

define what facultative anaerobes

Answer 29

can use for 02 for respiration but can also grow in its absence.

Question 30

define what obligate anaerobes mean

Answer 30

cannot use 02 and are killed by it

Question 31

define what microaerophiles mean.

Answer 31

require 02 in low amounts, but killed by high concetrations.

Question 32

define what aerotolerant anaerobes

Answer 32

cannot use 02, but are not killed by it.

Question 33

most bacteria grow at or near neutral pH

Answer 33

6.5-7.5

Question 34

bacteria that grow at very low pH:

Answer 34

acidophiles

Question 35

bacteria that grow at high pH:

Answer 35

alkaliphiles

Question 36

define osmosis

Answer 36

osmosis is the movement of solvent molecules across a semi-permeable barrier

Question 37

water will move from area of high concentration to area low concentration

Answer 37

osmotic pressure

Question 38

what is a hypertonic solution (name the characteristics)

Answer 38

high solute concentration , example: salt or sugar and water flows out of the cell and cell dries up we call that plasmolysis

Question 39

what is a hypotonic solution? name the characteristics

Answer 39

low solute concentration, water flows into the cell and cell bursts-osmotic lysis

Question 40

condition where solute concentration on outside of cell is equal to that inside the cell.

Answer 40

isotonic solution

Question 41

true or false. Osmotic pressure is important in food preservation. Name some examples

Answer 41

true, an example would be fish, honey, salted

Question 42

some bacteria have adapted to life salt concentrations -requiring up to 30% NaCl. These bacteria are termed :

Answer 42

extreme halophiles for example : bacteria that live in dead sea

Question 43

blood has a concentration of about 0.9%, and does not inhibit the growth of most microorganisms. True or false?

Answer 43

true

Question 44

what are the nutritional that influence growth

Answer 44

1. carbon 2.nitrogen, sulfur, and phosphorus 3.trace elements 4.energy

Question 45

this is required for all organic molecules-backbone living matter

Answer 45

carbon

Question 46

what is heterotrophs?

Answer 46

take carbon for organic matter (ex would be sugars)

Question 47

what is autotrophs?

Answer 47

use inorganic carbon (i.e C02)

Question 48

this is required in smaller amounts for synthesis of cellular material

Answer 48

nitrogen, phosphurus, sulfur example: protein, nucleic acids, phospholipids, ATP

Question 49

organisms need energy to build cell material and drive cellular processes

Answer 49

energy

Question 50

required in very small amounts and this is essential to the function of certian enzymes

Answer 50

trace elements such as iron, zinc, and molybdenum

Question 51

chemotrophs define it

Answer 51

acquire energy from chemical compounds, it may be organic or inorganic and example would be sugars

Question 52

are organisms classified based on how they obtain their carbon and energy

Answer 52

yes

Question 53

define what photoautotrophs are, what is their source? and what do they include?

Answer 53

uses sunlight for energy C02 as carbon source process called photosynthesis includes-- some bacteria like algae and plants

Question 54

what is photoheterotrophs?

Answer 54

use sunlight for energy, obtain organic carbon from food and some bacteria

Question 55

chemoautotrophs define it.

Answer 55

obtain energy from inorganic chemicals example for h2, h2s and uses co2 as carbon source and only done by some bacteria

Question 56

define what chemoheterotrophs

Answer 56

obtain energy from organic chemicals, use the same organic chemicals as their source of carbon. All animals,fungi, protoza and most bacteria, all medically reolevant bacteria are chemoheterotrophs because they cause disease in us

Question 57

Culture media: Solid media (Agar petri plates), how are they made?

Answer 57

made by adding agar (solidifying agent) to liquid bacteria , cannot be degraded by most bacteria

Question 58

does solid media allow growth of colonies ?

Answer 58

yes

Question 59

solid media allows growth of colonies: - a genetically identical population of cells, and allow the isolation of pure cultures

Answer 59

all true

Question 60

what can culture media be?

Answer 60

1) chemically defined 2) chemically undefined

Question 61

define what chemical defined mean.

Answer 61

the exact chemical composition of the medium is known example : media made from known quantities of salts and sugars this is also known as minimal media

Question 62

define what chemical undefined mean.

Answer 62

contains rich organic ingredients (so the chemical composition is not known) - also known as complex media example : media containing yeast extract

Question 63

define selective media

Answer 63

prevent the growth of unwanted organisms ,allowing only the desired microbes to grow

Question 64

what inhibits the growth of all gram positive and most gram negative bacteria

Answer 64

selective media

Question 65

define differential media

Answer 65

used to distinguish different bacteria

Question 66

this can grow-- but colonies of certain bacteria look different on the plate give an example

Answer 66

differential media ex: blood agar plates

Question 67

used to distinguish bacteria that can lyse(and eat) red blood cells name the example.

Answer 67

streptococcus pyogenes

Question 68

Counting bacteria : Direct count cells are counted by using what ?

Answer 68

by using a light microscope

Question 69

this usually employs a special counting chamber and inaccurate because it counts both live and dead cells

Answer 69

counting bacteria (direct count)

Question 70

Viable counts

Answer 70

only live cells are counted

Question 71

a liquid culture is diluted and plated onto agar plates to grow colonies

Answer 71

viable count

Question 72

each colony on a plate represents a single cell from the original culture

Answer 72

viable counts

Question 73

are colonies are counted, and used to calculate the # of bacteria in the original culture

Answer 73

viable counts

Question 74

what are counts aways expressed as ? and what are they called ?

Answer 74

expressed as cfu per mL and they are forming units

Question 75

assumption is that 1cfu=

Answer 75

1 live bacterial cell

Question 76

what does phototrophs mean?

Answer 76

harvest energy from the sunlight