Chapter 9 Study Guide Flashcards
They do not use oxygen because they usually have a fermentative metabolism
Does not use oxygen but tolerates it’s presence; grows anaerobically regardless of oxygen levels.
Aerotolerant anaerobes
Grow via fermentation or anaerobic respiration when oxygen is not available
Also, thrive in the presence of oxygen
Can grow with or without oxygen; prefers oxygen but can switch to anaerobic metabolism is oxygen is absent
Facultative anaerobes
Require oxygen concentration lower than air
Microaerophiles
Microorganisms that grow optimally at pH less than 5.55
Examples: sulfur oxidizing sulfolobus spp, ferroplasma, lacobacillis
Have optimal growth at ph of 3
Acidophile
Lactobacillus bacteria which are an important part of the normal microbiota of the vagina are
Acidophile
Most bacteria are _____, meaning they grow optimally at a ph within one or two ph units of the neutral ph of 7
Neutrophile
Prokaryotes reproduce asexually using
All daughter cells are genetically identical
Genetic variability is achieved by horizontal gene transfer
Binary fission
Are microbial communities attached to surfaces
Living
Non living
They may contain different species
An extracellular matrix of polysaccharides holds them together
Benefits include shared nutrients
Resistance to mechanical stress
Protection from immune system
Protection from drugs
Biofilms
Another curious example of cell division in prokaryotes, reminiscent of the live birth in animals, is exhibited by the giant bacterium epulopiscium. Several daughter cells grow fully in the parent cell, which eventually disintegrates, releasing the new cells to the enviorment
Budding
In some Cyanobacteria, many nucleoids may accumulate in an enlarged round cell or along a filament, leading to the generation of many new cells at once. The new cells often split from the parent filament and float away in a process called
Fragmentation
Organisms that cannot make certain nutrients and require them to be added to the medium
Fastidious organisms
The _____ is the time between the same points of the life cycle in two successive generations
Only in eukaryotes
Also called the doubling time
Generation time
Generation time for tuberculosis
15 to 20 hours
Bacterial growth curve
Lag phrase
Log phase
Stationary phase
Death or decline phase
No increase in number of living cells
Lag phase
Exponential increase in number of living bacterial cells
Log phase
Plateau in number of living bacterial cells rate of cell division and death roughly equal
Stationary phase
Exponential decrease in number of living bacterial cells
Death phase
Are microorganisms, typically archea, that thrive in extremely hot environments, with optimal growth temperatures above 80 degrees
Hyperthermophiles
Are adapted to moderate temperatures, with optimal growth temperatures ranging from room temperature (20 degrees Celsius) to about 45 degrees Celsius.
Examples : humans, E. coli, salmonella, lactobacillus
Mesophiles
Prefer cooler temperatures, from a high temp of 25 degrees Celsius to refrigeration temps of about 4 degrees Celsius. Responsible for food spoilage in refrigerated foods
Psychrotrophs
Require oxygen
Obligate aerobes
Do not require oxygen and are killed by oxygen
Only grows in oxygen free environments
Obligate anaerobes
A bio film forms when _____ bacteria of one or more species adhere to the surface, produce slime, and form a colony
Planktonic
In biofilm formation _____ cells are present in the first and last step of biofilm formation
Planktonic
Are organisms that can grow at 0 degrees and below and have an optimal growth temperatures close to 15 degrees Celsius
Psychrophiles
Involve a stepwise dilution of a substance, to reduce its concentration gradually.
Serial dilution
Refers to counting the cells in a liquid culture or colonies on a plate. It is a direct way of estimating how organisms are present in a sample.
Direct cell count
Can be used to differentiate between viable and dead bacterial cells in a sample
Fluorescence staining
Why must serial dilutions be made before doing a direct plate count ?
To reduce the concentration of bacteria, if the concentration is to high, the colonies on the plate will be to numerous to count (TNTC) leading to inaccurate results.
What range of colonies is ideal for direct plate count ?
30-300 colonies
The _____ involves mixing the diluted sample with molten agar, allowing colonies to grow both inside and on the surface of the agar. It’s suitable for aerobic and anaerobic organisms.
Pour plate method
The ______ involves spreading the diluted sample on the surface of solidified agar, allowing colonies to grow on its surface. It only supports aerobic growth
Spread plate
A statistical procedure for estimating of the number of viable microorganisms in a sample
Estimation of the number of coliforms in a sample of pond water
MPN most probable number
Reflects bacterial growth because as bacteria multiply in a liquid culture, they scatter light, making the solution cloudy.
Turbidity
The higher the ______, the more bacterial cells are present, indicating increased growth.
Turbidity
The most common form of bacterial reproduction, where a single cell divides into two identical daughter cells of equal size
The parent cell splits into several smaller pieces, each of which can grow into a new organism
A small growth, forms on the parent cell, grows, and eventually detaches to become a new organism
Binary fission
Fragmentation
Budding
A _____ is a complex community of microorganisms that adhere to surfaces and are embedded in a protective extracellular matrix
Biofilm
Where do biofilms form ?
Any surface, including medical devices, teeth, natural environments, plaque, rocks, water, and tissues in the body
Do biofilms only contain a single species
No, they contain multiple species of organisms including bacteria, fungi, and Protozoa
What advantages do microbes in biofilm enjoy ?
Protection from environmental stresses, antibiotics, and the immune system, as well as enhanced nutrient availability
Can contribute to chronic infections as the protective matrix makes microbes more resistant to antibiotics and immune responses.
Biofilms
Obligate anaerobic bacteria must be grown under conditions devoid of oxygen. The most common approach is culture in an
They include chemical packs that remove oxygen and release carbon dioxide.
Anaerobic jar
Each species has a range of temperatures in which it will grow.
The range is expressed as
Minimum - no growth below temperature
Optimal - most rapid growth
Maximum - no growth above this temp
Human pathogens you typically belong to the _______ group. They thrive in moderate temps, typically between 20c and 45c which includes the human body.
Mesophiles
Contains extracts or digests of plants, animals, or yeast.
Ex. Nutrient broth, tyrptic soy broth, brain heart infusion
Complex media
Is prepared by measuring out each individual chemical components
Defined media
_____Contains growth factors, vitamins, and other essential nutrients to promote the growth of______
Enriched media
Fastidious organisms
Media that inhibit the growth of unwanted microorganisms and support the growth of the organism of interest by supplying nutrients and reducing competition are called
Selective media
The _____ make it easy to distinguish colonies of different bacteria by a change in the color of the colonies or the color of the medium
Differential media
