Ch.6 Flashcards
Microbial Growth
increase of number of cells, not size
Physical requirements for microbe growth
temp, ph, osmotic pressure
Chemical requirements
carbon, nitrogen, sulfur, phosphorus , trace elements, oxygen organic growth factor
Psychrophiles
cold loving microbes 20-30 C
Mesophiles
moderate temperature microbes (grow at human temp)
Thermophiles
heat loving microbes
Osmotic pressure
Hypertonic environments or increase in salt and sugar cause plasmolysis
(water flows out)
Extreme/obligate halophiles
require high osmotic pressure
Chemical requirements
carbon- energy+ structure Nitrogen- amino acids + proteins Sulfur- amino acids + proteins, Phosphorus- DNA+RNA+ATP+Membrane
Toxic oxygens
Singlet oxygen, molecular oxygen boosted to a higher-energy state. Superoxide free radicals , Peroxide anion, Hydroxyl radical
Organic Growth Factors
Organic compounds obtained from the environment like Vitamins, amino acids, purines, and pyrimidines
Vitamins, amino acids, purines, and pyrimidines
Microbial Communities, form slime or hydrogels. Bacteria are attracted via quorum sensing.
Share nutrients and are sheltered from harmful factors
Culture medium
something prepared for the purpose of growing microbes.
Sterile
No living microbes
Inoculum
introduction of microbes into medium
Culture
microbes growing in/on culture medium
Agar
A culture media with complex polysaccharide, used for petri plates, slants and deeps. Not metabolized by microbes
Chemically defined media
exact chemical composition is known
Complex media
extracts and digests of yeasts, meat or plants, May be a nutrient broth or nutrient agar and must have a source for C,N, S,P and cofactors
anaerobic bacteria cultures
could be killed by oxygen, so they use a special reducing media athat has chemicals that combine with dissolved oxygen and depleted the oxygen in the culture media
Capnophile
microbes that require high COv2 conditions
COv2 packet or candle jar
Differential Media
make it easy to distinguish colonies of different microbes
Salt concentration of 2% or more generally preserve, by making the cell unable to reproduce
Selective Media
suppress unwanted microbes and encourage certain microbes
Enrichment Culture
encourages growth of a certain microbe, does not necessarily suppress another
colony
encourages growth of a certain microbe, does not necessarily suppress another
BSL 1-4
1- no special precautions. 2 lab coat, gloves, eye protection. 3 biosafety cabinets to prevent airborne transmission. 4- sealed, negative pressure, exhaust air is filtered twice
Binary Fission
main method of prokaryote reproduction where they split apart
Budding
bacteria form a bud that enlarges to the size of a parent cell, then separates (think a stem away from tree)
Conidiospores
small usually single-celled asexual reproductive body , made by pLANTS fungi and some bacteria.
Phases of growth
Lag phase intense acidity preparing for population growth. Log phase- logarithmic or exponential increase in population. Stationary phase- period, of equilibrium, microbial death, balance production of new cells . Death phase- population is decreasing at a log rate.
Plate count
most common method of measuring bacteria population, measures viable cells, but takes 24+ hours for visible colonies to form
Plates assumes that the bacteria grows and forms a single colony and known as colony forming units (CFU) They are counted by colonies that have 25-250 colonies
Pour plate method
a plate count of where bacterial dilution is put onto a empty plate and then melted nutrient agar is the poured and swirled into it. The colonies grow on top and in the solidified agar. But the melts agar maybe too hot for some bacteria.
Spread plate method
plate count where solid medium is already on a dish and bacterial dilution is spread on the medium, then colonies grow only on the surface
Filtration method
where 100 ml of water is passed through a then membrane where bacteria is too small to pass so it stays on there and is then put on a dish
MPN Most probable number
based on the fact that the greater the number of bacteria in a sample, the more dilution is needed to reduce the density to the point at which no bacteria are left to grow in the tubes in a dilution series. They get a series of tubes and put certain dilutions in them, the less diluted the less amount of tubes are postivee
They then use a statistical table to guestimate with 95% confidence
Generation rate
The rate of exponential growth of a bacterial culture is expressed as generation time, also the doubling time of the bacterial population
Direct microscopic count
a measured volume of bacteria suspension is placed within a defined area on a microscope slide. Needs high number, bacteria may be dead or alive, and problems if motile. Uses a petroff-hausser cell counter that uses a grid with squares etched into it. Number of bacteria
Turbidity
a sample is taken from a broth and measure the absorbance of light in a spectrophotometer . Indirect method
Metabolic activity
a product is produce and that is proportional to how ever many bacteria is present
Dry weight
when it is weighed after being dry
