chap 6 Flashcards
microbial growth needs both chemical: ______ ,and physical: ______ requirements
chemical: carbon, nitrogen, sulfer, phosphorous, trace elements (NADH, FADH), oxygen (in organic), organic growth factor
physical:
temperature, pH
most common nutrients:
carbon, oxygen, nitrogen, hydrogen
microbial growth is increase in _____ of cells, not cell ___.
number, (not) size
Temperature: optimal growth temp =
temp at which mo grows most rapidly
temperature changes affect:
- proteins; enzyme function (affects 3-D structure of molecule and H-bonding)
- lipids in cell membranes: too low=rigid, fragile cell membranes (not able to osmosis and diffusion). Cholesterol prevent function in low temp.
too high=too fluid and can’t hold in contents.
temperature groups based on optimal temp:
psychrophile:
opt. temp. between 15C and 15C, die at temps above 20C. Live in snow field, ice. not involved in human disease but in food spoilage
temperature groups based on optimal temp:
mesophile:
opt temp. btw 20C and 40C: as human pathogens
temperature groups based on optimal temp:
Thermophile:
opt temp. btw 45C and 70C: in compost piles and hot springs; no human disease, body temp is too cold
temperature groups based on optimal temp:
hyperthermophile:
(Archaea) opt temp. btw 70C and 110C
pH: organisms sensitive to changes in acidity; H and OH interface with H bonding in proteins and nucleic acids
- most bacteria and protozoa grow best pH 6.5-7.5 (neutral=blood):
- Neureophiles = pathogens
pH: organisms sensitive to changes in acidity; H and OH interface with H bonding in proteins and nucleic acids
- other bacteria and fungi grow best in acidic habitats:
- Acidophiles (yogurt)
pH: organisms sensitive to changes in acidity; H and OH interface with H bonding in proteins and nucleic acids
- ______ live in alkaline soils and water up to pH 11.5
- Alkalinophiles
physical effects of water:
microbes require water to dissolve enzymes and nutrients required in metabolism
most cell die in absence of ______.
water
water is important reactant in many metabolic reactions
some have _______ that retain water
cell wall
_____ and ____ cease (stop) most activity in a dry environment for years
endospores and cysts
hypertonic environment (increase in salt or sugar 10%) cause_______.
plasmolysis = crenation of cell (shrink)
obligate halophiles (salt 20~30%) require high osmotic ______.
pressure
facultative halophiles (_______) tolerate high osmotic pressure
osmotlerant
chemical requirements:
carbon
- organic molecules, energy source
- chemoheterotrophs use organic carbon sources
- autotrophs use CO2
chemical requirements:
nitrogen
- in amino acids and proteins
- most bacteria decompose proteins
- some bacteria use NH4 or NO3
- a few bacteria use N2 in nitrogen fixation
chemical requirements:
sulfur
- in amino acids, thiamine, biotin (vitamin)
- most bacteria decompose proteins
- some bacteria use SO4 2 or H2S
chemical requirements:
phosphorus
- in DNA, RNA, ATP, and membranes
- PO4 3 is a source of phosphorus
chemical requirements:
trace elements
- inorganic elements required in small amounts
- usually as enzyme cofactors
categories mo’s based on their O2 requirements:
obligate aerobes
- undergo aerobic respiration. don’t ferment.
categories mo’s based on their O2 requirements:
obligate anaerobes
- do not use aerobic metabolism
categories mo’s based on their O2 requirements:
facultative anaerobes
- can maintain life via fermentation or anaerobic respiration or by aerobic respiration
- E.coli: when O2 is not avail and nitrate (NO3) is, E.coli will use the nitrite (NO2) and ultimately ammonia (NH3) = ferment
categories mo’s based on their O2 requirements:
microaerophiles
- require small amount of O2 (2-10% oxygen) and are inhibited by normal (~21%) atmospheric amounts )eg. H.Pylori) due to limited amounts of enzymes
categories mo’s based on their O2 requirements:
aerotolerant anaerobes / obligate fermentors
- these mo’s are indifferent to oxygen because they do not use aerobic, and have some limited amounts of oxygen by-product enzymes (Streptococcus does not produce Catalase)
toxic oxygen (Reactive Oxygen Species - ROS):
- singlet oxygen:
- superoxide free radicals:
- peroxide anion:
- hydroxyl radical
- singlet oxygen = O2 boosted to a higher-energy state
- superoxide free radicals= superoxide dismutase (enzyme)
- peroxide anion= catalase + peroxidase = hydrogen peroxide
- hydroxyl radical = OH
biofilms = microbial communities
form _____ or ______
- bacteria attracted by chemicals via quorum sensing
- organism live in association with different species:
slime or hydrogels
- antagonistic relationships
- synergistic relationships
- symbolic relationships
culture media = depending on what you want to do.
- culture medium = nutrients prepared for microbial growth
- sterile = no living microbes
- inoculum = (inoculated) introduction of microbes into medium
- culture = microbes growing in/on culture medium
Agar (red seaweed)
- complex polysaccharide
- used as solidifying agent for culture media in Petri plates, slants (sloping surface of agar in a test tube), and deeps
- generally not metabolized by microbes
- liquefies at 100C
- solidifies at
culture media
- chemically defined media = exact chemical composition is known
- complex media = extracts and digests of yeasts, meat, or plants
- selective media
- differential media
- anaerobic media
heterotrophic bacteria =
bacteria that rely on organic compounds to grow and reproduce.
selective media
- saboraud’s gaar (media) - lower pH (5.6); encourages the growth of fungi and not bacteria
- thioglycolate media - contains a reducing compound which select for oxygen use
- endo agar (not gram-) - contains the dye, basic fuschin, which selects for Gr-mo’s that is selective for Staphylococcus (osomotolerant)
differential media
- blood agar = hemolysis patterns (alpha/green, bata/clear, gamma/none/don’t secrete)
- SIM media - sulfate and production of H2S (hydrogen sulfide) blackens media; differentiate enterics (intestine): Salmonella, Shigella, E.coli
- endo agar = contains lactose: appears red when colonies fermented
- mannitol/salt agar = contains phenol pH indicator : when mo’s fermented the mantel sugar and the pH becomes acidic, the agar turns from pink to yellow
- dark colonies =
- white/clear colonies =
- white + dark colonies =
E.coli
coliform bacteria
total coliform bacteria
anaerobic culture method
- reducing media = contains chemicals: thioglycolate or oxyrase to combine O2. Heated to drive off O2
capnophiles
microbes require high CO2 condition
candle jar = 5-7% oxygen
biosafety levels
BSL1 = no special precautions BSL2 = lab coat, gloves, eye protection BSL3 = biosafety cabinets to prevent airborne transmission BSL4 = sealed, negative pressure (moon suit) exhaust filter twice
colony is a population os cells arising from a single cell or spore or from a group of attached cells
colony is ofter called ____________.
________ method is used to isolate pure cultures
colony-forming unit (CFU)
streak plate method
deep-freezing =
-50 to -95C
lyophilization (freeze-drying) = for many years
frozen (-54 to -72) and dehydrated in a vacuum
reproduction in prokaryotes =
- binary fission
- budding
- fragmentation of filaments
binary fission:
20min (average time)
19-20 hours:Tuberculosis
- cell elongates and DNA is replicated. (chromosome attache to cell membrane)
- cell wall and plasma membrane begin to constrict
- it pinch together and cross-wall forms; completely separating the 2 DNA copies
- cells separate.
bacterial growth curve
in culture, gram neg- are all dead phase.
- lag phase
- log phase
- stationary phase=increase waste
- death phase
after incubation, count _____ on plates 25-250 (CFUs)
= viable count (not count dead one)
colonies
SIM =
Sulfate = H2S (black +) Tryptophan = Indole (red ring +) Motility = stab line (needle), E.coli, Salmonella, Shigella
counting bacteria by filtration = viable count
filter retains cells
most probable number = viable count
- multiple tube MPN method
- count positive tubes (count how many tubes are positive)
- viable count
direct microscopic count of bacteria = non viable count
all cells in several large squares are counted, then numbers are averaged.
measuring microbial growth:
indirect method
- turbidity = how many bacteria are in it
- metabolic activity
- dry weight (dry, and weigh) = Cyanobacteria: which lake has more or less
Generation time =
bacteria grow in different rate under optimal condition of growth.
