Assessment #3 Flashcards
Bacterial Nutrition
culture medium
a nutrient material prepared for the growth of microorganisms in a laboratory
inoculum
microbes that are introduced into a culture medium
culture
the microbes that grow and multiply in or on a culture medium
examples of criteria that a culture medium must meet
- right nutrients
- sufficient moisture
- proper pH
- suitable level of oxygen
- sterile
- proper temperature
agar
- a complex polysaccharide derived from a marine alga (agarophytes)
- a polymer of galactose and galacturonic acid
- isolated from seaweed agarocytes in the seaweed
- a solidifying agent added to the medium to create a solid medium
- it is NOT a nutrient itself
agar concentrations
- normal agar: 1.5% (weight per volume)
- eg - 15g per liter of water
- soft agar: 0.5% (weight per volume)
- often used for overlays
why can most bacteria not digest agar?
- most bacteria lack agarase, an enzyme that can digest agar
chemically-defined medium
- a medium whose exact chemical composition is known
- also known as a synthetic medium
fastidious organisms
organisms that require many growth factors
complex medium
- a medium whose exact chemical composition is basically unknown
- often made up of yeast, meat, protein, and plant extracts at various amounts
semi-defined medium
- a medium whose chemical composition is partially known
- between chemically-defined medium and complex medium
liquid medium
a complex medium in liquid form
reducing medium
- medium that contains ingredients that chemically combine with dissolved oxygen and deplete the oxygen in the culture medium
- used to grow obligate anaerobes
uses of bacterial media
- enrichment
- selective
- differential
- (selective and differential)
- maintenance
bacterial media for enrichment
- allows organisms to grow on the basis of what they prefer
- designed to increase numbers of desired microbes to detectable levels
- Winogradsky column
bacterial media for selection
- adds an inhibitory agent that will prevent some bacteria from growing while allowing others to grow
- suppresses unwanted microbes and encourages desired microbes
- eg - antibiotics, basic dyes, bismuth sulfite agar
bacterial media for differentiating
- addition of something that will differentiate (not inhibit) between microbes
- eg - milk agar, pH indicator, blood agar
bacterial media for maintaining
- used to maintain and preserve microorganisms for long-term
bacterial media for selecting and differentiating
- supresses unwanted microbes and differentiates colonies of desired microbes from each other
- eg - MSA (mannitol salt agar), EMB (eosin-methylene blue agar)
bacterial nutrition patterns
- energy source
- carbon source
- electron donor source (reducing power)
chemotrophs
- obtain energy from chemicals
phototrophs
- energy source is electromagnetic radiation - sunlight
heterotrophs
- organic carbon source
- C w/H = organic
autotrophs
- inorganic carbon source
- C w/o H = inorganic
- eg - carbon dioxide
- C w/o H = inorganic
organotroph
- an organic compound is the electron donor source
lithotroph
- inorganic electron donor source
which nutritional classification are humans?
chemoheteroorganotrophs
which nutrition classifications are bacteria?
bacteria can be combinations of any of these three sources, resulting in high diversity
who invented the petri dish?
Julius Richard Petri
who developed bacteriological media?
Robert Koch
who discovered agar?
- Walther and Fannie Heese
- Both worked in Koch’s lab
- Koch took credit for their discovery
what was the first type of bacteria cultured with agar?
- Mycobacterium tuberculosis
- It was the first time that it had ever been cultured
- Cultured by Koch
What was the principal reason for developing methods to culture and isolate microorganisms?
The principal reason was to identify bacterial agents of disease
Vibrio cholerae
- Causes cholera
Bacillus anthracis
- Causes anthrax
Mycobacterium tuberculosis
- Causes tuberculosis
Corynebacterium diphtheriae
- Causes diphtheria
Biogeochemical cycles
- The ways in which an element or compound moves between various living and nonliving forms and locations in the biosphere
- There are six elements that are principally involved in these cycles.
Essential elements of life
- CHNOPS
- carbon
- hydrogen
- nitrogen
- oxygen
- phosphorus
- sulfur
- Involved in the biogeochemical cycles
- Most exist in both organic and inorganic forms
Examples of inorganic and organic nitrogen sources
- Inorganic
- ammonia
- Organic
- amino acids
Examples of inorganic and organic sulfur sources
- Inorganic
- hydrogen sulfate, sulfite, sulfate
- Organic
- sulfur-containing amino acids
- enable junction between N and S cycles
- sulfur-containing amino acids
Examples of inorganic and organic sources of phosphorus
- Inorganic
- phosphate
- Organic
- biomolecules
What are the major trace elements? What are their functions?
- Magnesium (Mg)
- stabilizes the negative charge of the cell membrane/cell wall
- Calcium (Ca)
- balances ionic strength
- maintains the equilibrium of potassium between external and internal
- Iron (Fe)
- found within the proton chain
What are the minor trace elements? What are their functions?
- Boron (B)
- Nickel (Ni)
- Zinc (Zn)
- Molybdenum (Mo)
- Serve as cofactors for specific enzymes
- eg - nitrogenase and nitrate reductase require Mo to be synthesized and to function
The 3 cardinal temperatures of growth
- minimal temperature - the lowest temperature that is required for growth
- optimum temperature - the ideal temperature
- skewed towards the maximum
- maximum temperature - the highest temperature that allows growth
Psychrophiles
- Range = -5 to 20 C
- Optimum = 5-10 C
Psychrotrophs
- Optimum = 15 to 20 C
- Can grow at temperatures below 0 C (like psychrophiles), but have a higher optimal temperature
- Therefore also known as facultative psychrophiles
Mesophiles
- Range = 15-45 C
- Optimum = 30-37 C
- The majority of organisms
- High diversity
Thermophiles
- Higher temperature range of 45-80 C
Extremophiles
- Highest temperature range
- Optimal = >80 C
