Chapter 6- Microbial Nutrition and Growth Flashcards
Microbial growth refers to an ___________________________, NOT in the ____ of the cell
Increase in the numbers of microbial cells, not the size
3 basic requirements that all cells need for metabolism:
a carbon source, an energy source, and an electron source
Carbon sources and where they get their energy from
Autotrophs- CO2
Heterotrophs- organic
Energy sources and where they get their energy from
Chemotrophs- organic
Phototrophs- light
Electron (H) sources and where they get their energy from
Organotrophs- organic
Lithotrophs- inorganic
Plants and algae are considered
photoautotrophic (CO2 and light)
Humans, bacteria, animals, fungi, etc. are considered
chemoheterotrophs (both organic)
Obligate aerobes
Requires oxygen to live and grow
Oxygen is used as the final electron acceptor when making energy
Obligate anaerobes
Unable to use oxygen for growth because it lacks enzymes (like catalyse)
Oxygen can actually be toxic for them
Facultative anaerobes
Prefers oxygen, but can survive without it
Aerotolerant anaerobes
Has small levels of enzymes but doesn’t use oxygen
Prefers no oxygen but will tolerate it
Microaerophiles
able to survive with low levels of oxygen
Nitrogen Fixation- what is it and why is it important?
When microbes are able to convert the nitrogen in the air (N2) into NH3
This is essential since it’s providing a usable form of nitrogen for other organisms to use
Other elements necessary for growth are Sulfur, Calcium, and Phosphorus. _____, ____, and ____ are used to help produce cofactors
Zinc, copper, and iron
3 groups based on the preferred temperature of a microbe
Which is most likely to be pathogenic and why?
Psychrophiles- likes cold
Mesophiles- in between
Thermophiles- likes heat
Mesophiles because they like human temperatures the best
Most bacteria grow best between a pH of __-__, and are considered _______. Few bacteria grow at an acidic pH, but those that do are called ______.
What type of bacteria grows best in a basic environment?
6.5-7.5, neutrophiles
acidophiles
Alkalinophiles
A medium is the
material prepared or supplied for the growth of microorganisms in a laboratory
Define culture
Microorganisms that grow and multiply in a medium
Three requirements for the medium:
1. A medium must provide an ____ source and vitamins
- The medium itself must be ____, in other words, it must initially contain no living microorganisms. The medium can be sterilized by an instrument called an _______, which provides steam under pressure in order to kill all microorganisms.
- When microorganisms are introduced or transferred into a fresh, sterile medium to initiate growth, this technique is known as _____. After you inoculate the medium with microorganisms, the culture now must be incubated at an optimal temperature.
- A medium must provide an ENERGY source and vitamins
- The medium itself must be STERILE, in other words, it must initially contain no living microorganisms. The medium can be sterilized by an instrument called AUTOCLAVE, which provides steam under pressure in order to kill all microorganisms.
- When microorganisms are introduced or transferred into a fresh, sterile medium to initiate growth, this technique is known as INOCULATION. After you inoculate the medium with microorganisms, the culture now must be incubated at an optimal temperature.
Inoculation
When microorganisms are introduced or transferred into a fresh, sterile medium to initiate growth
Media comes in either liquid or solid form.
- The liquid form of any type of medium is referred to as a ____.
- The solid form of medium is prepared when a solidifying agent such as ___ is added to the liquid medium. Agar is a polysaccharide derived from ___
Media comes in either liquid or solid form.
- The liquid form of any type of medium is referred to as a BROTH
- The solid form of medium is prepared when a solidifying agent such as AGAR is added to the liquid medium. Agar is a polysaccharide derived from ALGAE
The liquid medium always comes in a test tube, but the solid medium can come in three forms:
Slant tubes
Deep tubes
Petri plates (agar plate)
Advantages of using solid medium (i.e. agar medium)
(1) Microorganism does not break down the structure of agar, and they grow nicely on the surface of agar.
(2) It is much easier to observe microbial growth on the solid surface of agar medium instead of a liquid medium. We usually refer this microbial growth on agar medium as colonies.
3) Agar can provide increased surface area for microbial growth.
A colony is a
visible mass or population of microbial cells arising from a specific single microbial species
Usually the microbiologists observe the size, shape, color, margins, elevation, etc. of colonies grown on an agar plate in order to determine the characteristics of a specific microbial species. These characteristics of the colony are known as its _____ _____
colony morphology
Care must be taken when culturing a microorganism otherwise contamination may occur. The goal is to culture an Axenic culture. What does axenic mean?
Pure
A plate that is being used as the control: is it axenic?
No
A plate that has a colony of microbial growth: axenic?
Yes
How do you know if broth is contaminated?
If it turns turbulent
Cloudiness in broth is called
turbidity
There is a group of bacteria called “____” bacteria, which are ____ to grow in the laboratory because they require special media, longer incubation time, anaerobic condition, etc. For example, bacteria ______ __________ (causes TB) is a fastidious bacteria.
There is a group of bacteria called “fastidious” bacteria, which are difficult to grow in the laboratory because they require special media, longer incubation time, anaerobic condition, etc. For example, bacteria Mycobacterium tuberculosis(causes TB) is a fastidious bacteria.
4 major types of media
complex, enriched, selective, differential
Complex media
Most common, generalized (so most bacteria grow well in complex media)
Ex: Nutrient agar and tryptic soy agar (TSA)
Complex media are made up of nutrients such as ____ from yeasts, beef, or plants and _____.
extracts and peptones
Extracts are ______________________, while peptones are ___________________
Extracts are concentrated dry powder containing all the nutritional ingredients.
Peptones are partially digested protein molecules.
(Protein molecules are huge and very few bacteria can utilize protein molecules directly. Once the huge protein molecules are broken down to peptones, then they can be utilized directly by bacteria for growth.)
Enriched media is also generalized, but with an added ingredient: _____. Enriched media is used to ______ the growth of a _____ bacteria species of interest. It’s typically used to cultivate bacteria from samples such as:
Enriched media is also generalized, but with an added ingredient: blood. Enriched media is used to encourage the growth of a particular bacteria species of interest. It’s typically used to cultivate bacteria from samples such as: blood, urine, and sputum
Example of enriched media
blood agar
Selective Media
will select for the growth of a particular microorganism OR select for the growth of a particular type of bacteria while suppressing (inhibiting) the growth of others.
Types of selective media
Sabouraud dextrose agar
MacConkey agar
EMB agar (Eosin-methylene blue agar)
HE agar (Hektoen enteric agar)
Sabouraud dextrose agar
selects ONLY for the growth of fungi while inhibiting bacterial growth
supplemented with antibiotics (added ingredient)
acidic pH
MacConkey agar
selects ONLY for gram-negative bacteria while inhibiting the growth of gram-positive bacteria
What inhibits the growth of gram-positive bacteria for MacConkey agar?
Both bile salts and crystal violet
EMB agar
selects ONLY for the growth of gram-negative bacteria while inhibiting the growth of gram-positive bacteria
What inhibits the growth of gram-positive bacteria for EMB agar?
Eosin and methylene blue
MacConkey agar chemical ingredients
bile salts, neutral red, crystal violet (a dye), and lactose.
HE agar
selects for the growth of gram-negative bacteria ONLY while inhibiting the growth of gram-positive bacteria due to its chemical ingredients
EMB agar chemical ingredients
peptone, eosin, methylene blue, lactose, and sucrose
HE agar chemical ingredients
bile salts, bromthymol blue and acid fuchsin (2 different dye molecules), lactose, sucrose, sulfur, and iron
What ingredient inhibits gram-positive bacteria for HE agar ?
only bile salt
Differential media are used to ______ one bacterial species from another. Either a _____ occurs in the media or the ____ _____ changes.
Differential media are used to DISTINGUISH one bacterial species from another. Either a CHANGE occurs in the media or the COLONY APPEARANCE changes.
Examples of differential media:
MacConkey agar
HE agar
Blood agar
MacConkey agar will select for gram-negative bacteria first and then it can differentiate among them based on whether the bacteria can ferment the ____ ____ or not. In other words, MacConkey agar can differentiate among the gram-negative bacteria it selects based on ____ ______.
MacConkey agar will select for gram-negative bacteria first and then it can differentiate among them based on whether the bacteria can ferment the SUGAR LACTOSE or not. In other words, MacConkey agar can differentiate among the gram-negative bacteria it selects based on LACTOSE FERMENTATION.
MacConkey agar differential:
Neutral red remains ______at neutral pH, but turns to bright ___at acidic pH. So gram-negative bacteria that ferment sugar lactose appear pink on MacConkey agar and they are known as ______-_____ _____-_____ bacteria. On the other hand, gram-negative bacteria that DO NOT ferment sugar lactose will NOT turn bright pink on MacConkey agar (will remain whitish or creamy color ) are known as ___-____-_____ gram-negative bacteria.
Neutral red remains COLORLESS at neutral pH, but turns to bright PINK at acidic pH. So gram-negative bacteria that ferment sugar lactose appear pink on MacConkey agar and they are known as LACTOSE-FERMENTING GRAM-NEGATIVE bacteria. On the other hand, gram-negative bacteria that DO NOT ferment sugar lactose will NOT turn bright pink on MacConkey agar (will remain whitish or creamy color ) are known as NON-LACTOSE-FERMENTING gram-negative bacteria.
HE agar is also a selective AND a differential media just like MacConkey agar. HE agar also selects for gram-negative bacteria first and then differentiates among them based on ______ _____
lactose fermentation
What color does lactose-fermenting gram-negative bacteria turn on HE agar?
What about non-lactose fermenting gram-negative bacteria?
salmon-orange
retains blue-green color
HE agar can differentiate bacteria based on their ability to utilize ____. When hydrogen sulfide reacts with iron, it forms ____ ____ on the HE agar.
sulfur
black precipitates
Blood agar differentiates bacteria based on red blood cell _____, in other words, whether or not a bacteria can _____ (break down) red blood cells.
hemolysis
hemolyze
For Blood Agars, the ____ changes, not the ____
media
colony
Three types of hemolysis:
alpha
beta
gamma
Alpha-hemolysis
partially hemolyze (green/gray media)
Beta-hemolysis
completely hemolyze
(clear)
Gamma-hemolysis
unable to hemolyze (no change)
A final type of media that can be used is specific for obligate anaerobes. Anaerobic media contains ____ ____ which ____ ____, allowing for the growth of anaerobic bacteria.
Anaerobic media contains SODIUM THIOGLYCOLATE which REMOVES OXYGEN, allowing for the growth of anaerobic bacteria.
Eosin-Methylene blue is both a selective and _____ media. It assesses for lactose fermentation: positive will look ____/____/metallic while negative will have ___ ____/media
differential
purple/black/metallic
no color/media
A mixed culture is a culture that contains a _____ _____ of microbial species, while a pure culture contains only a ____ ____ ____ (also called ____)
A mixed culture is a culture that contains a MIXED POPULATION of microbial species, while a pure culture contains only a SINGLE MICROBIAL SPECIES (also called AXENIC)
Microbiologists prefer to work with pure cultures, but bacteria often forms in a community composed of different bacteria.
This community is known as a ______. The ____ (70%) of bacterial ___ is due to biofilms.
This community is known as a BIOFILM. The MAJORITY (70%) of bacterial DISEASE is due to biofilms.
What is a biofilm?
A complex relationship among numerous microbes
Biofilms form on surfaces of ____ devices and ____ membranes
Biofilms form on surfaces of medical devices and mucous membranes
Many microbes are more ____ when part of a biofilm
harmful
How does a Biofilm form?
- Begin with ___ ____microbes
- Microbes land on a ____and ____
- Microbes produce an ______ _____ (shield)
- _____ ______ molecules released
Communication between microbes
Able to determine population and species of microbes
Helps to control certain genes within each microbe
Microbes assume specific ______ to _____community - New microbes arrive, ____ ______ form
- Microbes ____ to form new biofilms
- Begin with free living microbes
- Microbes land on a surface and attach
- Microbes produce an extracellular matrix (shield)
-
Quorum sensing molecules released
Communication between microbes
Able to determine population and species of microbes
Helps to control certain genes within each microbe
Microbes assume specific functions to benefit community - New microbes arrive, water channels form
- Microbes leave to form new biofilms
Quorum sensing triggers cells to change their _____ and ____
biochemistry and shape
Most microorganisms reproduce by ____ ___. It’s a form of ____ reproduction where one microbe divides in half to produce ___ daughter cells
binary fission
asexual
two
Binary fission steps:
- Chromosome _____ (attaches to cell membrane)
- Cell ______, ______chromosome
- ____ cell wall/cell membrane form ____
- ____ is completed, separating into___ _____ microbes.
- Chromosome REPLICATES (attaches to cell membrane)
- Cell ELONGATES, SEPARATING chromosome
- NEW cell wall/cell membrane form SEPTUM
- SEPTUM is completed, separating into 2 IDENTICAL microbes.
Basically, with each division of binary fission, the population ____. This is represented as __ (indicates _____ growth)
n = generation
doubles
2^n (exponential growth)
Generation Time
The time required for a bacterial cell to double (divide)
Most have a doubling time of 1-3 hours
____ is an extremely ___ growing bacteria, and the doubling time is about __ ____ Mycobacterium on the other hand has a generation time of __ ___ and are considered “fastidious”
E. coli
20 minutes
10 days
4 phases of growth
lag phase
log phase
stationary phase
death phase
Lag Phase
- Little change in # of microbes
- Adapting to environment
- Lasts hours to days
Log Phase
- Exponential growth (2^n)
- Cells most active
- Best time to gram stain
- Best time to assess effectiveness of antibiotics
Stationary Phase
- Growth slows
- Deaths = divisions- equilibrium
Death Phase
- Deaths > divisions
- Accumulation of wastes, depletion of nutrients, change in pH
Quantifying the number of bacteria present is an important part of microbiology. It can be useful when determining the severity of an ______, effectiveness of an _____ or _____, etc.
There are both direct and indirect measurements of microbial growth.
Quantifying the number of bacteria present is an important part of microbiology. It can be useful when determining the severity of an infection, effectiveness of an antibiotic or disinfectant, etc.
There are both direct and indirect measurements of microbial growth.
Direct measurements of growth
Plate counts
Coulter counter
Plate counts-
Basically, a given bacterial culture is inoculated onto an agar plate. The plate is then measured for ____ _____ on the plate after incubation. The advantage of this method is that it measures only the number of ____ (___) bacterial cells, no dead cells.
colony growth
viable (living)
Recall that a colony is a visible mass of bacterial cells coming from a particular bacterial species, NOT a single bacterial cell. Usually a colony comes from a ____ of _____ ______
Recall that a colony is a visible mass of bacterial cells coming from a particular bacterial species, NOT a single bacterial cell. Usually a colony comes from a clump of bacterial cells
When plate counts is used to measure a bacterial population, the result is often recorded as _____-____ ____
When plate counts is used to measure a bacterial population, the result is often recorded as colony-forming units
What can happen when too many bacterial cells are inoculated onto an agar plate (Plate count)
cells become overcrowded and do not develop into separated colonies, which causes inaccuracy in the count
Plate count is completed by either the ____ _____ ____ or the ____ ____ ____
Plate count is completed by either the pour plate method or the spread plate method.
Where do colonies form in the pour plate method? Spread plate method?
Pour plate- in and on the agar
Spread plate- only found on the surface
Besides the plate counts, there is another way to directly measure microbial growth. ____ ____ ____ (both viable and dead cells) can be done electronically, with an instrument called a _____ _____, which counts the number of bacterial cells in a given bacterial culture.
Besides the plate counts, there is another way to directly measure microbial growth. Total cell counts (both viable and dead cells) can be done electronically, with an instrument called a Coulter counter, which counts the number of bacterial cells in a given bacterial culture.
Plate counts only measure ____ ___, while coulter counters measure ____ ____ ____ _____ _____
Plate counts only measure living cells, while coulter counters measure both living and dead cells
What are indirect measurements of microbial growth?
-Turbidity
-Dry weight
-Metabolic activity
-Molecular methods (evaluate DNA/RNA)
Turbidity-
As bacteria grow in a liquid medium, the medium becomes turbid or ____ with bacterial cells. The instrument that is used to measure the turbidity is called a ______________
As bacteria grow in a liquid medium, the medium becomes turbid or cloudy with bacterial cells. The instrument that is used to measure the turbidity is called a spectrophotometer
Turbidity measures both
alive and dead microbes
The more turbid a culture (cloudy), the ____ the _____ _____
the greater the bacterial population
Spectrophotometer:
A light is shown through the tube. The light that is transmitted can get to the light-sensitive detector, allowing it read how much light coming from the light source has been transmitted.
With turbidity, the light coming from the light source cannot be transmitted directly through a culture of bacterial cells due to the ________. So not much light can get to the detector which gives a ___ reading of the percentage of light transmitted.
With turbidity, the light coming from the light source cannot be transmitted directly through a culture of bacterial cells due to the interference. So not much light can get to the detector which gives a poor reading of the percentage of light transmitted.
