in a cluture tube indicates the presence of organisms
turbidity using spectrophotomer
Amount of turbidity is determined by a samples absorbance of light.
Cannot distinguish between live and dead cells
Acid loving organisms.
grows best @ a pH of .1-5.4.
Exist from pH 5.4-8.0.
causes most diseases in humans
Alkali loving organisms (base loving).
exist form 7.0-11.5.
example; vibrio cholerae
cold loving organisms.
best grown at 15 to 20'c
most bacteria grow best at 25'c & 40'c.
Human pathogens are included in this category.
Best grown @ temp of 50*-60*c.
Found in compost heaps
Must have specific environment.
Can grow above normal range of mesophite or thermophile.
One that contains known specific kinds & amount of chemical substances.
Chemically nondefined medium.
Contains reasonably familiar material.
varies slightly in chemical composition from batch to batch.
Free O2 (for aerobic respiration).
Common in cause in hosp.
Killed by free O2
appear to grow best in the presentce of a small amount of free O2.
Ordinary carry on aerobic metabolism when oxygen is present but shift to anarobic metabolism.
Salt loving organisms
Describe the process of binary fission.
septum begins to form (Partition between daught cells).
Cell division occurs.
2 identical daughter cells produced (clone)
List the four phases of bacterial growth.
Describe the 4 phases of bacterial growth.
Lag; organism do not increase significantly in number, but they are metabolically active growing in size. synthesizing enzymes incorparating various molec. from a medium.
Log; growth occurs at an exponential (log) rate; organisms are dividing at their fastest rate. 2,4,8,16,32 etc. Generation time=time required for each doubling (unique to each species & environment).
Stationary; cell division slows as the environment changes (less nutrients, pH, &O2 levels), some cell dying or dividing:total # of cells remains about contant.
Decline/death; conditions in medium decline. Cells are unable to divide. Live cells decrease at a (log) rate (indicated by downward sloping diagonal). Cells may undergo involution variety of unusual shapes.
How does a bacteria grow in a colony?
All cells descendents of original cell (clones).
Method used to obtain a "pure culture".
Growth phase display differently in colonies growing on a solid medium.
Divide exponentlially; form small colonies of orginal cell.
Identify areas of rapidly-growing cells and dying cells in bacteria grown colony.
Older cells in death phase in center: less nutrients.
Rapid growth occurring at edges.
Describe two techniques of isolating bacteria to obtain pure cultures.
Streak Plate; isolated colonies. Use agar plates; bacteria picked up w/wire loop (sterile), moved to agar. Always sterilizaiton the loop wire each time. Then the sample is obtained from the 1st agar swipe and process repeated in a new location. then to 2nd to a 3th and tranfered to any appropriate sterile medium for further studies. Use aseptic techniquies.
Pour plate; used mostly for aeropriles that cannot tolerate O2. Makes use of serial dilu. when serial dil. reaches 1000 microorganizms, 1ml of diute w/ 9ml of melted agar and quickly poured into sterile plate.
What factors may affect bacterial growth?
Nutritional:availability of C, N, S, Phosphorus, trace telements, some vitamins
What is optimum pH?
The pH at which a microorganism grows best.
How are bacteria classified according to their growth temp range?
pyschrophiles is cold loving.
mesophiles is human body temp 25*-40*.
thermophiles is warm loving 50-60*
Where do you find pychrophiles, mesophiles, and thermophiles?
Pyscgriogukes=cold water & soil.
Mesophiles= pathogenic mostly.
Thermophiles= hot springs
Which types are mostly pathogenic?
How are bacteria classified according to their O2 needs?
Aerobes= require O2 to grow.
Anaerobes= do not require O2.
What are the fundamental differences between anaerobes and aerobes?
aerobes= require O2 to grow. rapidly dividing cells require more O2 than slower dividing cells.
anaerobes; do not require O2 to grow. die/killed by O2
Which enzymes are present in the aerobes?
What are the pattern of O2 use that each will exhibit?
Obligate aerobe:must have free O2 for aerobic resp.
Obligate anaerobe: killed by free O2.
Microaerophile: grow best in lower levels of O2, but not anaerobic conditions.
Facultative anaerobe: can survive in the presence of O2 but ferment (metabolize w/o O2 at all times)
What techniques are used to culture anaerobes in the lab?
What nutrients are needed for bacterial growth?
certain trace elements and vitamins
Compare/contrast selective media and diffenterial media & give examples of each.
selective media; encourages the growth of some organisms but suppresses the growth of other.
example; sulfadiazine and polymyxin sulfate (SPS) added to anaerobic coultures of clostridium.
differential media; has a constituent that causes an observable change (a color change or a pH change) when a biochemical rxn. allows distinguish a certain type colony from other colonies.
example of SPS agar and MacConkey agar contains crystal violet & bile salts that inhibits growth of G+ bacteria while growing G-