Chapter 6: Microbial Growth

The increase in the number of cells is known as

microbial growth

Groups of cells large enough to be seen with the naked eye

colonies

What are the physical requirements for microbial growth?

temperature, pH, osmotic pressure

What are the chemical requirements for bacterial growth?

macro/micronutrients, oxygen

Cold-loving microbes

psychrotrophs

Moderate temperature-loving microbes

mesophiles

Heat-loving microbes

thermophiles

The lowest temperature at which a species will grow

minimum growth temperature

The temperature at which a microbe grows best

optimum growth temperature

The highest temperature at which
binary fission is possible

maximum growth temperature

Most bacteria prefer a pH range of:

6.5-7.5

Bacteria that prefer acidic conditions

acidophiles

In what type of solution will cells not swell or shrink?

isotonic

Half the dry weight of a typical bacterial cell is:

carbon

Chemicals or elements required by the microbe in small quantities

trace elements

Bacteria that are unable to use oxygen for ATP
synthesis, harmed by O2

obligate anaerobe

Organisms that require oxygen to live and to
synthesize ATP, cannot grow without O2

obligate aerobe

Can use oxygen if present but can continue to live and grow when oxygen is NOT present

facultative anaerobe

Do not require oxygen to grow but can tolerate it well, oxygen gas is NOT toxic to these organisms

aerotolerant anaerobe

Only grow in oxygen concentrations lower than those in air

microaerophiles

A nutrient material prepared for the growth of
microorganisms

culture medium

Microbes that are introduced into a culture media to initiate growth

inoculum

Microbes that grow and multiply in or on a culture medium

culture

Contain only one species seen on a solid
agar plate

pure culture

A visible population of viruses that have destroyed host cells form a:

viral plaque

A unit of measurement used in virology to quantify the number of infectious virus particles in a sample

plaque forming unit

A unit of measurement that estimates the number of bacteria cells in a sample that can multiply to form a visible colony on a culture plate

colony forming unit

Culture media where the exact chemical composition is known

chemically defined media

“Picky eaters” that require many growth factors

fastidious bacteria

Culture media where the exact chemical composition varies from batch to batch

complex media

Culture media that removes All available O2 for the growth of anerobic bacteria

reducing media

Culture media that suppress unwanted microbes and encourages growth of desired microbes

selective media

Culture media that allow differentiation between bacteria within a group

differential media

A non-selective culture medium that encourages the growth of a desired microbe by increasing very small numbers of a
desired organism to detectable levels

enrichment media

The time required for a cell to divide, typically through binary fission

generation time

The period of little to no cell division

lag phase

The period when cells begin to divide, cellular reproduction is at its highest

log phase

The period of equilibrium, the number of cell death is equal to the number of
new cells being produced

stationary phase

The max number of organisms an environment can support

carrying capacity

The period where the number of deaths occurring exceed the number of microbes being formed

death phase

The death phase in the bacterial growth curve is also known as the

logarithmic decline phase

The log phase in the bacterial growth curve is also known as the

exponential growth phase

A measurement of cloudiness within a
spectrophotometer

turbidity

Responsible for many human diseases, peak at 37°C

mesophiles

Will grow best near the top of a test tube, but growth will occur throughout

facultative anaerobe

Will grow evenly throughout a test tube

aerotolerant anaerobe

Will grow near surface of test tube

obligate aerobe

Phase where lack of nutrients limits growth

stationary phase

Phase with intense metabolic activity and DNA replication

lag phase

This process occurs when a cell is placed in a hypertonic solution

shrinkage

This process occurs when a cell is placed in a hypotonic solution

lysis

Metallic ions and vitamins are examples of

inorganic enzyme cofactors

Media used to grow obligate anaerobes

reducing media

Media used for fastidious, “picky eaters”

chemically defined media

Media used in research and experimental work

chemically defined media

Media used for growth of the most chemoheterotrophic organisms, used in labs

complex media

Media used for the suppression of unwanted microbes, used in clinical and public health microbiology

selective media

Media used to distinguish colonies of the desired organism

differential media

Media used to increase numbers of desired microbes to detectable levels

enrichment media

May contain blood, serum, or egg yolk

enrichment media

Mannitol salt agar or Blood agar

differential media

Bismuth sulfite agar

selective media

Anaerobic jar, may contain ascorbic acid

reducing media

Contains extracts from yeast, meats, plants
or protein products

complex media

Most common method of measuring by performing serial dilution of samples

plate counts

Solution is passed through a filter
that collects bacteria

filtration method

A volume of bacteria is suspended onto a slide, average number of bacteria per viewing field is calculated

microscopic count

assumes the amount of a metabolic product is directly proportional to the number of bacteria present

metabolic activity

When bacteria are filtered, dried and weighed

weight method