ch 6 Flashcards
know why we study a population
microbial growth equals an increase in cell number (not just the size of a single cell)
what is the cell cycle
- young cell
- chromosome is replicated and new and old chromosomes move to diff sides of cell
- protein band forms in the middle of cell
- septum formation begins
- when septum is complete cells are considered divided.
why are the growth curves plotted log
helps graph better
know the 4 phases of growth and characteristics of each phase
Lag phase: no increase in cell #s
Exponential (Log) phase: max rate of division and population growth
Stationary phase: population growth ceases-death rate= division
Death (Decline) phase: population # decreases
know the reasons cell enter the stationary phase and how do they respond (what do they do) in the stationary phase
cells are changing to become more resistant to harsh conditions
endospore formation
decrease in size
condense the nucleiod
describe the 3 general temp assessed for microbes
minimum temp: is the smallest number the species can grow in
optimal temp: is the best range the species grows in
max: highest number the species can grow in before dying
know the optimal ranges of cardinal groups and characteristics of those in these ranges
cold/cooler temps:
psychrophiles: 10-15 degrees C
psychrotrophs: 25-30 degrees C
middle temp:
mesophiles: 35-40 degrees C
higher temp:
thermophiles: 60-65 degrees C
hyperthermophiles (extreme thermophiles): 75-80 degrees C
know the 3 groups of microbes relating to pH
acidophiles: 1-5.5
neutrophiles: 5.5-7
alkalophiles: 8.5-11.5
why do microbes need
carbon
nitrogen
sulfur
phosphorus
Nitrogen:
Nitrogen is used in amino acids, proteins and nucleotides.
Most bacteria decomposed proteins to have a nitrogen source. A few bacteria are capable of converting N2 to NH4+ in a process called nitrogen fixation.
Sulfur:
Sulfur is used in some amino acids, thiamine (B1) and biotin (B7).
Most bacteria decompose proteins to have sulfur.
Phosphorus:
Phosphorus is used in DNA, RNA, ATP and membranes found in the form of phospholipids. Some microbes store extra inorganic phosphorus.
Carbon:
used in structural organic molecules, enzymes, and also as energy sources for catabolism and ATP synthesis.
Carbon is found in heterotrophs and autotrophs.
know all 5 categories of microbes in relation to oxygen
obligate aerobes: require oxygen to obtain energy from nutrients; has to have oxygen 20% in the atmosphere if it doesn’t have it will die; aerobic respiration
obligate anaerobes: unable to use oxygen for energy producing processes, many are harmed by the presence of oxygen; do not need oxygen, oxygen is toxic to them, cannot make above enzymes unless in an oxygen environment; anaerobic respiration; growth at bottom b/c there is little to no oxygen
facultative anaerobes: uses oxygen when present, but can survive by using fermentation when oxygen is not available; prefer oxygen if not present can do fermentation; aerobic respiration
microaerophiles: require oxygen but can only grow in low concentration, lower than air concentrations; aerobic respiration; middle of tube grows in its sweet spot and may see it at other areas (range); bacteria grows in that area if there motile it will probably die before it gets there;
aerotolerant anaerobes: can tolerate oxygen but do not use it for growth; do not care about oxygen do not use it; anaerobic respiration
why are some organisms poisoned by oxygen
Toxic forms of oxygen are made when oxygen combines with certain atoms. These toxic forms of oxygen kill obligate anaerobes because they lack protective enzymes. Protective enzymes help some bacteria survive around the toxic forms of oxygen.
what does
SOD
catalase
peroxidase
SOD
Allows toxic forms of oxygen to be neutralized
decomposes toxic oxygen to hydrogen peroxide and oxygen
Catalase
Decomposes hydrogen peroxide into water and oxygen.
Peroxidase
Breaks down hydrogen peroxide into water .
describe a biofilm
mixed microbial communities not pure cultures of a single organism
hydrogel keeps cells together
why are biofilms so dangerous
since the biofilm cells are in hydrogel they are sheltered from harmful factors which makes it harder to get rid of
chemically defined media
exact chemical composition is known
ex. minimal salts media
