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.