micro 101 (MJC)

• 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).

• 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

• TEMP.
• 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.

• Pseudomonas.
• 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

• Cell duplicates;.
• Chromosome duplicate.
• septum begins to form (Partition between daught cells).
• Cell division occurs.
• 2 identical daughter cells produced (clone)

• Lag phase.
• logarithimic phase.
• stationary phase.
• death phase

• 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.

• 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.

• Older cells in death phase in center: less nutrients.
• Rapid growth occurring at edges.

• 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.

• Physical factors.
• temp.
• pH.
• O2 concentration.
• moisture.
• hydrostatic pressure.
• osmotic pressure.
• radiation.
• Nutritional:availability of C, N, S, Phosphorus, trace telements, some vitamins

The pH at which a microorganism grows best.

• pyschrophiles is cold loving.
• mesophiles is human body temp 25*-40*.
• thermophiles is warm loving 50-60*

• Pyscgriogukes=cold water & soil.
• Mesophiles= pathogenic mostly.
• Thermophiles= hot springs

Mesophiles

• Aerobes= require O2 to grow.
• Anaerobes= do not require O2.

• 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

• peroxidase.
• catalase.
• superoxide dimutase

• 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)

• Carbon.
• nitrogen.
• sulfur.
• phosphorus.
• certain trace elements and vitamins

• 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-