CH 6 Flashcards
Cell Division
- when unicellular organisms (bacteria) divide they are reproducing
- when multicellular cells divide they are replacing dead or damaged cells or growing.
Prokariotic Reproduction
Asexual Reproduction
-99% of time in unicellular organisms
- produces offspring
-genetically identical to parent cell
-no partner involved
- no exchange of genetic material between
cells
Common forms of Asexual reproduction
- In unicellular organisms, Budding and
Binary fussion
Budding
(Typically seen in yeast)
- New smaller offspring (clone) “buds” from
the original cell (parent)
- breaks away from parent cell, then grows
to the mature size
Binary Fission
-Original parent cell grows in size, including
replication of cellular content.
- cell splits into TWO identical cells, typically
seen in bacteria
Conjugation
.1% chance
- sexual reproduction in microbes
- rare, 2 bacteria reproduce sexually
- one cell makes copy of its chromosome or plasmid and transfers the copied DNA
- exchange of genes
- Resulting in offspring or genetically different cell from its parent
Life Cycle of Prokaryote
4 Microbial Growth Phases
- bacteria introduced to new mediums ideal for growth, they go through 4 phase
- Lag, Log, stationary, death or decline
Lag Phase
-Bacteria adapting to new conditions, no reproduction, little metabolic activity
Log Phase
- Peak reproductivity and metabolic
activities
Stationary Phase
- # of new cells are produced offset by # ofcells dying, nutients begin to decline and
waste begins to accumulate
Death Phase
- Conditions inhospitable,nutrients deplete,
waste inhibits growth/reproduction. Cells
die, population declines
Physical Influences on Growth
Most bacteria grow best under moderate condition like
- Ph near 7
- low to no salt
- temperature near 37C
Growth preferences
PH
- Acidophile
- Alkaliniphile/Alkalophile
Growth Preferences
Salt
- Halophile
- Most fermented food
Growth Preference
Temp.
- Psychrophile
- Mesophile
- Thermophile
- Extreme thermophile
Oxygen and Growth
- Obligate Aerobes
- Microaerophiles
- Obligate Anaerobes
- Facultative Anearobes
Obligate Aerobes
Requires oxygen for growth
Microaerophiles
Grows best when O2 is less than normal
atmospheric concentration of 21%
Obligate Anaerobes
Does not grow if Oxygen is present. Grows in abscense of oxygen
Facultative Anaerobes
Grows in presence of oxygen or without
Testing for Oxygen
“Gas Pak”
Chemically remove oxygen in sealed chamber from petri plate
Testing for Oxygen
“FTM”
- Fluid Thioglyate medium
- top layer oxygen, no oxygen on bottom layer
- innoculate by stabbing media
- incubate 24 hr.
Reduce leves of oxygen to less than 21% by burning a candle in sealed jar. Combistion removes some oxygen, but not most.
Testing for Microaerophiles
“Candle Jar”
Some bacteria produce slime which they use to attach to substrate/surface. Forming a community called. Plaque is a type of ________, that has harderdened onto teeth enamel.
Biofilms (bacterial interactions)
A phenomenon whereby microbes communicate w/one another to “sense” their population # and other key info.
Quorum Sensing
The process whereby vegetative cells turn into spores. usually triggered by lack of key nutrients.
Sporulation (spore formation)
A medium, agent or tool used to cultivate/grow microorganisms.
Media
A media whereby you know exactly everything about the media. Non-biological ingredients (ex. Salt, sugar)
Defined Media
Exact ingredients and their amounts is UNKNOWN. Ingredients are biological in origin. (Milk, blood)
Complex Media
Promotes the growth of only a certain type of bacteria while inhibits others.
Selective Media
Allows for differentiation of one species of bacteria from another based on growth/appearence. (EMB. E Coli, metallic green sheen like beetles shell)
Differential Media
