chapter 4 microbial growth Flashcards
bacterial growth refers to increase in bacterial cell numbers or does it refer to the increase of size of individual cells?
it refers to the increase in bacterial cell numbers
how do most bacteria reproduced ?
most of them reproduce by binary fission
define the characteristics of bacteria cell
elongates and makes a copy of its DNA, divides into two identical cells which we call the daughter cells.
exponential growth:
As we re-call bacteria divide by binary fission, what does this indicate for the population of cells ?
it will double every generation
what is the term called for the time required for population to double?
it is called generation time
what are the two terms that we use in a bacterial growth in a lab and define what they mean
culture and inoculation
culture= microbes growing in a medium
inoculation: introducing microbes into a medium to start a culture
define what batch culture mean
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
define what continuous culture mean
it is an open system, nutrients are continuously added, wastes are continuously removed, this supports indefinite growth
name the growth curve in batch culture
lag phase
exponential phase
stationary phase
death phase
phase of prolonged decline
define what exponential phase and the other term for it.
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.
define what lag phase is.
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
define what the term death phase is.
toxic waste products have accumulated(gathered), in visuals (decreased rapidly .)
the cells die at a uniform rate
define what the phase of prolonged decline is.
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
define what stationary phase is
cells have reached maximal population density
nutrients have bee used up, waste have accumulated and no increase in cell number.
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.
true
define the following terms: What do they mean?
minimum
optimum
maximum
minimum - lowest temp supporting growth
optimum-temperature that supports best growth
maximum-highest temp supporting growth
what’s the temperature that supports the best growth?
optimum
bacteria can be grouped based on temperature range name the following terms
psychrophiles
psychrotrophs
mesophiles
thermophiles
hyperthermophiles
define what mesophiles are. also include its
min
max
optimum
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
define what psychrophiles are.
cold loving and grow between -5 and about 15c , they are killed at 20 degrees.
what are psychrotrophs?
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
define what thermophiles are
heating loving, and the min is about 40 degrees, and the max is 80 and the optimum is about 65.
what are hyperthermophiles , include the min, max, and optimum.
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.
this involves the use of both hot and cold temperatures
food safety both involve the hot and cot temperature
heat is used to kill ____ and ____ microbes such as cooking.
mesophilic, and pyschrotophic
what temperature is used to slow growth?
cold temperature, and only psychroprophs will grow in refrigerator and slowly.
oxygen can be toxic to other and only requirement by some organisms.
true
define what obligate aerobes
require 02 for respiration (energy genration)
define what facultative anaerobes
can use for 02 for respiration but can also grow in its absence.
define what obligate anaerobes mean
cannot use 02 and are killed by it
define what microaerophiles mean.
require 02 in low amounts, but killed by high concetrations.
define what aerotolerant anaerobes
cannot use 02, but are not killed by it.
most bacteria grow at or near neutral pH
6.5-7.5
bacteria that grow at very low pH:
acidophiles
bacteria that grow at high pH:
alkaliphiles
define osmosis
osmosis is the movement of solvent molecules across a semi-permeable barrier
water will move from area of high concentration to area low concentration
osmotic pressure
what is a hypertonic solution (name the characteristics)
high solute concentration , example: salt or sugar and water flows out of the cell and cell dries up we call that plasmolysis
what is a hypotonic solution? name the characteristics
low solute concentration, water flows into the cell and cell bursts-osmotic lysis
condition where solute concentration on outside of cell is equal to that inside the cell.
isotonic solution
true or false.
Osmotic pressure is important in food preservation. Name some examples
true, an example would be fish, honey, salted
some bacteria have adapted to life salt concentrations -requiring up to 30% NaCl. These bacteria are termed :
extreme halophiles for example : bacteria that live in dead sea
blood has a concentration of about 0.9%, and does not inhibit the growth of most microorganisms. True or false?
true
what are the nutritional that influence growth
- carbon
2.nitrogen, sulfur, and phosphorus
3.trace elements
4.energy
this is required for all organic molecules-backbone living matter
carbon
what is heterotrophs?
take carbon for organic matter (ex would be sugars)
what is autotrophs?
use inorganic carbon (i.e C02)
this is required in smaller amounts for synthesis of cellular material
nitrogen, phosphurus, sulfur
example: protein, nucleic acids, phospholipids, ATP
organisms need energy to build cell material and drive cellular processes
energy
required in very small amounts and this is essential to the function of certian enzymes
trace elements such as iron, zinc, and molybdenum
chemotrophs define it
acquire energy from chemical compounds, it may be organic or inorganic and example would be sugars
are organisms classified based on how they obtain their carbon and energy
yes
define what photoautotrophs are, what is their source?
and what do they include?
uses sunlight for energy
C02 as carbon source process called photosynthesis
includes– some bacteria like algae and plants
what is photoheterotrophs?
use sunlight for energy, obtain organic carbon from food and some bacteria
chemoautotrophs define it.
obtain energy from inorganic chemicals example for h2, h2s and uses co2 as carbon source and only done by some bacteria
define what chemoheterotrophs
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
Culture media:
Solid media (Agar petri plates), how are they made?
made by adding agar (solidifying agent) to liquid bacteria , cannot be degraded by most bacteria
does solid media allow growth of colonies ?
yes
solid media allows growth of colonies:
- a genetically identical population of cells, and allow the isolation of pure cultures
all true
what can culture media be?
1) chemically defined
2) chemically undefined
define what chemical defined mean.
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
define what chemical undefined mean.
contains rich organic ingredients (so the chemical composition is not known)
- also known as complex media
example : media containing yeast extract
define selective media
prevent the growth of unwanted organisms ,allowing only the desired microbes to grow
what inhibits the growth of all gram positive and most gram negative bacteria
selective media
define differential media
used to distinguish different bacteria
this can grow– but colonies of certain bacteria look different on the plate
give an example
differential media
ex: blood agar plates
used to distinguish bacteria that can lyse(and eat) red blood cells name the example.
streptococcus pyogenes
Counting bacteria :
Direct count
cells are counted by using what ?
by using a light microscope
this usually employs a special counting chamber and inaccurate because it counts both live and dead cells
counting bacteria (direct count)
Viable counts
only live cells are counted
a liquid culture is diluted and plated onto agar plates to grow colonies
viable count
each colony on a plate represents a single cell from the original culture
viable counts
are colonies are counted, and used to calculate the # of bacteria in the original culture
viable counts
what are counts aways expressed as ? and what are they called ?
expressed as cfu per mL and they are forming units
assumption is that 1cfu=
1 live bacterial cell
what does phototrophs mean?
harvest energy from the sunlight
