Microbiology Chapter 6

__________ _____________ is a type of media that microbiologists use to identify bacterial species that destroy red blood cells

Blood agar

a few species of bacteria reproduce by ____________; they form a small initial outgrowth (a bud) that enlarges until its size approaches that of the parent cell and then it separates.

Budding

What is the advantage of studying microbial growth?

By understanding the conditions necessary for microbial growth, we can determine how to control the growth of microbes that cause diseases and food spoilage.

What is used to grow bacteria that requires and increased CO2 concentration?

CO2 incubators or candle jars

This statistical estimating technique is based on the fact that the greater the # of bacteria are left to grow in a sample, the more dilution is needed to reduce the density to the point at which no bacteria are left to grow in a dilution series

Most probable number (MPN) method -- is useful when microbes being observed will not grow on a solid media

Is Oxygen a chemical requirement for all bacteria?

NO- some will die in the presence of oxygen

This chemical is important for protien synthesis--- the synthesis of DNA, RNA, and ATP--- makes up about 14% of the dry weight of a bacterial cell--- this chemical is used to for amino acids of proteins---

Nitrogen

This element is essential for the synthesis of nucleic acids and phospholipids of cell membranes

Phosphorus

Where do most thermophiles live? what element is important for their survival?

Places like volcanos and hotsprings--- sulfur is ususally important in their metabolic activity

A method of inoculating a solid nutrient medium by mixing bacteria in the melted medium and pouring the medium into a Petri dish to solidify

Pour plate method

Is it true that some bacteria can grow well on just about any culture medium; others require special media, and still others cannot grow on any nonliving media yet developed

TRUE- all of these are true--- she mentioned something about a cow's eye

True of False: Most organisms grow well at the temperatures that human favors

TRUE- but certain bacteria grow at extreme temperatures that would certainly hinder the survival of eukaryotic organisms

If osmotic pressure become unusually low (the environment is hypotonic) what could happen?

The water form the environment will enter the cell.. some microbes that have a relatively weak cell wall may be lysed (explode)

These microorganisms are capable of growth at high temperature... what groups of microbes is this?

Thermophiles

What are these? singlet oxygen, superoxide radicals, superoxide anions, superoxide dismutase (SOD), peroxide anion, catalase, peroxide, and ozone?

These are all toxic forms of oxygen

True or False: most bacteria grow only within a limited range of temperatures, and their maximum and minimum growth temperatures are only about 30 degree celsius apart.

True

Is it true that endospores formed by thermophilic bacteria are usually heat resistant to treatment given canned goods?

True- elevated storage temperatures may cause surviving endospores to germinate and grow (not a major public health concern)

is it true that bacteria benefit form being a part of a biofilm

Yes

Do microbes typically survive in extremely cold environments?

Yes- the usually survive, some go dormant... the number of bacteria in cold temps may go down over time, but the usually survive

What does on have to do when transferring obligate halophiles/extreme halophiles in lab?

You must dip you inoculating loop into a saturated salt solution before attempting to loop the extreme halophilic organism

The microbes that grow and multiply in or on a culture medium are referred to as __________

a culture

_____________ ____________ _____________ have the effect of moving of removing necessary water from a cell.

High osmotic pressure

What happens when the environment of a cell is hypertonic?

It's when a microbial cell is in a solution whose concentration of solutes is higher than in the cell... the cellular water passes out through the plasma membrane to the high solute concentration

This group of microorganisms include most of the common spoilage and disease organisms.

Mesophiles

The most common types of microbes belong to what group of microorganisms?

Mesophiles- because the optimum range of growth temperature is 25-45 degrees Celsius

An indirect way of estimating bacterial numbers is measuring the __________ __________ of the population... give examples

metabolic activity ex: acid production or oxygen consumption

These bacteria are aerobic... However, they grow only in oxygen concentrations lower than those in air

microaerophiles

Which grow over a wider range of pH levels, molds or bacteria?

molds

Some important bacteria use gaseous nitrogen directly form the atmosphere

nitrogen fixation

when agar is added to complex media, it is called _________ _________

nutrient agar

f a complex media is in liquid for it is often called ________ ___________

nutrient broth

These organisms require oxygen to grow

obligate aerobes

these bacteria are unable to use molecular oxygen for energy-yeolding reactions

obligate anaerobes

Essential organic compounds an organism is unable to synthesize are known as _____________

organic growth factors

Optimal growth for molds and yeast are usually about pH _________to ________

pH 5 to 6

Peptones and amino acids in some media act as buffers, and many media also contain ___________ ____________

phosphate salts

What can be used in medium to produce a buffering effect in pH growth range of most bacteria?

phosphate salts

__________________ are non toxic; in fact, they provide phosphorus, an essential nutrient.

phosphate salts

What are the two main categories of requirements for cell growth?

physical and chemical

The osmotic loss of water causes __________________, or shrinkage of the cell's cytoplasm

plasmolysis

What is the mechanism behind salt or sugar curing meats?

plasmolysis- it sucks all the water out of bad microbial cells

These microbes are cold loving... what are they?

psychrophiles

This type of media is used for growing anaerobes--- this media contain ingredients, such as sodium thioglycolate, that chemically combine with dissolved oxygen and deplete the oxygen in the culture medium.

reducing media

This media is designed to suppress the growth of unwanted bacteria and encourage the growth of the desired microbes

selective media

the process of diluting several times, to get an appropriate # of CFU's on a plate for a plate count

serial dilution

A plate count method in which inoculum is spread over the surface of a solid culture medium

spread plate method

What phase is it when the growth rate slows, the number of microbial deaths balance out the number of new cells, and the population stabilizes

stationary phase

having NO LIVING MICROORGANISM

sterile

What are the physical aspects of microbial growth?

temperature, pH, and osmotic pressure

Preserving household food supplies via refrigeration is based on what principle

the principle that the microbial reproductive rates decrease at low temperatures

These microbes are heat loving... what are they?

thermophiles

Microbes require very small amounts of other mineral elements, such as iron, copper, molybdenum, and zinc; these are referred to as:

trace elements

estimating ________ is a practical way of monitoring bacterial growth

turbidity- by using a spectrophotometer

What are the three groups that microorganisms are classified into based on their preferred range of temperature

1) psychrophiles 2) mesophiles and 3) thermophiles

Aerobes, facultative anaerobes, and aerotolerant anaerobes must have the enzymes ________ __________ and either _______________ or _________________

1) superoxide dismutase 2) catalase 3) peroxidase

List the 4 steps of binary fission

1) Cell elongates and DNS is replicated 2) Cell wall and plasma membrane begin to constrict 3) cross-wall forms, completely separating the 2 DNA copies 4) Cell separates

what are the 3 a typical means in which bacteria can reproduce?

1) budding 2) aerial spore formation 3) fragmentation

What kind of bacteria is a chemoautotrophic bacteria, and where is it typically found?

1) it's an acidophile and 2) is typically found in drainage water from coal mines and oxidizes sulfur to form sulfuric acid

When we talk about microbes that are growing, we are talking about them increasing in ________________, accumulating into _______________.

1) number 2) colonies

When you talk about microbial growth, we are referring to the _____________ of cells, not the ____________ of the cell

1) number of cells 2) size of the cells

When counting a plate count the US Food and Administration convention says to only count plates with 25-250 colonies... but many microbiologist prefer plates with ______-_______ colonies

30- 300

What is the average optimum temperature for many pathogenic bacteria is about ___________ Celsius

37 degrees Celsius--- which is 98.6 degrees fahrenheit.

What is the optimum growth of thermophiles?

50-60 degrees Celsius

Most bacteria grow best in a narrow pH rangenear neutrality, between pH ___________ and ____________

6.5 and 7.5

Hyperthermophiles/ extreme thermophiles have an optimum growth rate a what temp?

80 degree C or higher

What are some things used when trying to grow anaerobes in laboratories?

A sealed jar with chemicals that remove oxygen from the jar--- the poor man's way of doing it The rich man could go out and buy an "anaerobic chamber"

The cells begin to divide and enter a period of growth, or logarithmic increase, called the ________ phase, or _______________ _____________ phase

log exponential growth

This chemical, besides water, is one of the most important requirements for microbial growth--- it is the structural backbone of living matter---makes up about half the dry weight of a typical bacterial cell

Carbon

To reflect the reality that bacterial colonies may not have risen from a single bacterium cell, but from short segments of a chain or from bacterial clumps, plate counts are often reported in _________ ________ ___________ ( )

Colony-forming units (CFU)--- plate counts

This type of media is made up of nutrients including extracts from yeasts, meat, or plants, or digests of proteins from these and other sources

Complex media

freezing a substance and sublimating the ice in a vacuum; also called dry freezing

lyophilization

These more common organisms do not require high salt concentrations but are able to grow at salt concentrations up to 2%--- this concentration typically inhibits the growth of most microorganisms

Facultative halophiles

True or false: Is it true that microbe grow more vigorously at the high and extremes within their range

False- microbes grow poorly at the high and low temperature extremes within their range--- this means that they grow optimally at the midpoint of their temperature range.

What temperatures do psychrotrophs favor, and what are these groups of organisms known as

Favor cold temperatures- -10 to 30 degrees Celsius

This element is used to synthesize sulfur-containing ammino acids and vitamins such as thiamine and biotin

Sulfur

Microbes that use molecular oxygen (____________) extract more energy from nutrients than microbes that do not use oxygen (______________)

aerobes anaerobes

these organisms canon use oxygen for growth, but tolerate oxygen fairly well

aerotolerant anaerobes

acidophiles

are bacteria that are remarkably tolerant of acidity--- most bacteria will not grow below about pH 4

Why do microbiologists add chemical buffers to growth mediums?

because when bacteria are cultured in lab, they often produce acids that eventually interfere with their own growth.

bacteria normally reproduce by _________ ________

binary fission

Communities of bacteria are called?

biofilms

In nutrient poor environments, how do many bacteria survive and grow?

by forming biofilms

How are pure cultures typically obtained?

by the streak plate method

Microbes that grow better at big CO2 concentrations are called

capnophiles

What are the chemical requirements of microbial growth?

carbon, nitrogen, sulfur, phosphorus, oxygen, trace elements, and organic growth factors

A _________ ______________ medium is one whose exact chemical composition is known

chemically defined

A visible ____________ theoretically arises from a single sore or vegetative cell or from a group of the same microorganisms attached to one another in clumps or chains

colony

A nutrient material prepared for the growth of microorganisms in a laboratory is called _______________

culture medium

When the number of deaths eventually exceeds the number of new formed cells, the population enters the ______________ phase, or ___________ _________ phase

death phase logarithmic decline phase

preservation of bacterial culutres at -50 degrees C- 95 degrees C

deep-freezing

This media makes it easier to distinguish colonies of the desired organism from other colonies growing on the same plate

differential media

a measured volume of a bacterial suspension in placed within a defined area on a microscope slide

direct microscopic count

A culture medium used primarily for isolation that favors the growth of a particular microorganism

enrichment culture

What is a convenient method of growth measurement for filamentous organisms such as fungi?

measuring dry weight

these microorganisms have adapted so well to high salt concentrations that the actually require the for growth

extreme halophiles/ obligate halophiles

These microorganisms can use oxygen when it is present but are able to continue to grow by using fermentation of anaerobic respiration when oxygen is not available.

facultative anaerobes

.... this is a method where bacteria are retained on the surface of a membrane filter and the transferred to a culture medium to grow and subsequently counted

filtration method

The time required for a cell to divide

generation time

The time required for a cell to divide or a population to double is known as the __________ ___________

generation time

colines are __________________

groups of cells that can be seen without a microscope

Where do microorganisms obtain almost all of their nutrients?

in solution from the surrounding water

Microbes that are introduced into a culture medium to initiate growth is called an

inoculum

What is a psychrophile?

it is a type of psychotrophs

OxyPlate is what?

it's another form of environment control when trying to grow anaerobes in the lab--- just like an anaerobic jar or anaerobic chamber

define "maximum growth temperature"

it's the highest temperature at which growth is possible for a certain species of bacteria will grow

define "minimum growth temperature"

it's the lowest temperature at which a certain bacterial species will grow

define "optimum growth temperature"

it's the temperature at which a certain bacterial species will grow the best

The period of little or nor cell division if called the _______ phase

lag--- can last for 1 hours or several days

These microbes are moderate-temperature loving... what are they?

mesophiles