Baterial Growth, Variation And Metabolism Flashcards
All bacteria have three major nutritional needs for growth.
What are these needs❓
- Carbon (50% dry weight)
- Nitrogen (14% dry weight)
- Source of energy
- Bacteria that are able to growth using CO2 as their sole source of carbon are known as❓
- How do they obtain energy❓
- Lithotrophs/Autotrophs
- Photosynthetically (phototrophs)
By oxidation of inorganic compounds (chemolithotrophs)
All bacteria found in humans are❓
Heterotrophs
E. coli and pseudomonas aeruginosa grow on the most simple laboratory media
True or false❓
Why❓
True
Growth requirements include a wide variety of organic compounds
Haemophilus influenzae and other anaerobes can only be cultured in the lab using❓
Why❓
- Vitamins, purins, pyramidine and hemoglobin supplied in growth medium
- They need additional growth requirements
Chlamydia sp. cannot be cultured on laboratory medium at all
True or false❓
How are they grown❓
True
Must be grown in tissue culture
What is a “minimal” medium❓
- A lab culture media whose contents are simple and completely defined
- Not usually used in diagnostic micro labs
What is a “nutrient” medium❓
Give examples
- made of extracts of meat or soybeans
- more complex
•eg nutrient broth, trypticase soy broth
What is a “enriched” medium❓
Give examples
•contains added growth factors such as blood, vitamins and yeast extract
•eg blood agar
Chocolate agar
What is a “selective” medium❓
Give examples
•contain additives that inhibit the growth of some bacteria but allow others to grow
•MCA:
MacConkey agar
Selective for gram-negative bacteria
•Colistin-nalidixic acid:
Selective for gram-positive bacteria
What do differential mediums do❓
Give an example
- For visualization of metabolic differences between groups or species of bacteria
- MacConkey agar differentiates between lactose fermenters(pink) and non-lactose fermenters(clear)
- Blood agar differentiates between hemolytic and non-hemolytic organisms
What is a transport medium used for❓
Give examples
•Holding medium designed to preserve the viability of microorganisms in a specimen w/o allowing multiplication
•
Stuart broth
Amies
Cary-Blair
What three factors should be considered for bacterial culture in the lab❓
pH
Temperature
Gaseous composition of atmosphere
Diagnostic laboratory media are usually adjusted to a final pH between 7.0 and 7.5
True or false❓
Why❓
True
Most pathogenic bacteria grow best at a neutral pH
Psychrophilies are bacteria that❓
•grow optimally at 10-20C (cold temp)
Mesophilies are bacteria that❓
- grow optimally at 20-40C (moderate temp)
* most bacteria that have adapted to the human body belong in this category
Thermophilies are bacteria that❓
•grow optimally at 50-60C (cold temp)
Diagnostic laboratories routinely incubate cultures for bacterial growth at ❓
35C
Fungal cultures are incubated at what temperature❓
30C
Classify bacteria based on their atmospheric requirements for growth
•Obligate aerobes:
require oxygen for growth
•Aerotolerant anaerobes/facultative aerobes:
can survive in the presence of oxygen but do not require it for metabolism eg clostridium spp.
- Obligate anaerobes: can’t survive in the presence of oxygen
- Facultative anaerobes: can grow either with or without oxygen
There are organisms that grow best when the atmosphere is enriched with extra carbondioxide (5-10%).
What are they called❓
Give an example
Capnophilic organisms
Haemophilus influenza
Microaerophilic bacteria require a reduced level of oxygen to grow.
Give an example
Campylobacter spp.
5-6%
Bacteria divide by binary fission. What does “generation time” mean❓
The time required for one cell to divide into two cells
What is generation time for:
A) E. coli
B) Mycobacterium tuberculosis
A) 20minutes
B) 24hrs
List the phases of a bacterial growth curve and the corresponding events in those phases
- Lag phase:
•preparation to divide - Log phase:
•logarithmic increase - Stationary phase:
•limited nutrients/no growth - Death phase:
•non-viable bacteria>viable bacteria
Fermentation is a process of energy production carried out by what group of bacteria❓
The final electron acceptor is❓
Obligate and facultative anaerobes
An organic compound
The major end product of alcoholic fermentation is❓
Ethanol
- The major end product of homolactic fermentation is❓
2. Give some examples of bacteria that use this pathway
- Lactic acid
2. Streptococcus genus (all members) Lactobacillus genus (some members)
- The major end product of heterolactic fermentation is❓
2. Give some examples of bacteria that use this pathway
1. Lactic acid CO2 Alcohol Formate Acetate
- Lactobacillus (some members)
- The major end product of propionic acid fermentation is❓
2. Give some examples of bacteria that use this pathway
- Propionic acid
- Propionibacterium acnes
Some anaerobic non-spore forming, gram-positive bacilli
- The major end product of mixed acid fermentation is❓
2. Give some examples of bacteria that use this pathway
1. Lactic Acetic Succinic Formic Acids
- Shigella
Salmonella
Escherichia
- The major end product of butanediol fermentation is❓
2. Give some examples of bacteria that use this pathway
- Acetoin
2,3-butanediol - Klebsiella
Enterobacter
Serratia
The EMP/Glycolytic pathway
1) Generates energy in the form of❓
2) Reducing power in the form of❓
3) Anerobic/Anaerobic❓
4) Used by which bacteria❓
- ATP
- NADPH
- Anaerobic
- Entrobaceriaceae
The pentose phosphate/phosphogluconate pathway is used by which bacteria❓
Heterolactic fermenting bacteria such a lactobacilli
Brucella abortus
The entner-doudoroff pathway
- uses enterococcusfaecalis
- is an aerobic pathway
1) True or false❓
2) Mention bacteria that use this mechanism
True
Pseudomonas
Alcaligenes
An important step in classifying members of the enterobacteriaceae family is the ability of the microorganism to ferment lactose
True or false
True
In the utilization of lactose by bacteria…
- Transport of lactose across cell wall into bacterial cytoplasm by beta-galactoside permease
- Breakage of galactoside bond to release glucose for fermentation by beta-galactosidase
All organisms that can ferment glucose can ferment lactose
True or false
False
Quite the contrary
