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- Unicellular (parent cell).
- double in size.
- divides into daughter cells
division of a mother cell
- cell duplicates its components.
- divide each min
growing & dividing at different time
- in a cluture tube indicates the presence of organisms
- (cloudy appearance).
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.
- example: Lactobacillus
- 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.
- Thermoduric organism.
- Human pathogens are included in this category.
- Heat-loving organism.
- 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.
- Clostridium botulinum.
- 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.
- Cell duplicates;.
- Chromosome duplicate.
- septum begins to form (Partition between daught cells).
- Cell division occurs.
- 2 identical daughter cells produced (clone)
List the four phases of bacterial growth.
- Lag phase.
- logarithimic phase.
- stationary phase.
- death phase
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?
- Physical factors.
- O2 concentration.
- hydrostatic pressure.
- osmotic pressure.
- 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?
- superoxide dimutase
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-