Chapter 4- Microbial Growth Flashcards
Nobel Prize for disease causing microbes; developed methods of cultivating bacteria
R. Koch
Fannie Hesse suggested AGAR medium to Koch because
there were limitations with solidifying liquid media w/ gel media such ass melting @ certain temps AND digestible by bacterias
Microbes can grow in EXTREME conditions such as
oceanic, volcanic, polar regions
Why is it important to grow microbes in culture?
Each species grow under specific conditions, medical significance, nutritional/ industrial uses
Binary fission
replication of parent cell that creates two identical daughter cells that often stick together & form chains, pairs, etc
exponential growth
population doubles each division
generational time
time it takes for population to double
How do bacteria/prokaryotic cells divide?
Binary Fission
Consequences of exponential growth
can cause bacteria to spread very rapidly in such short amount of time
Growth can be calculated by
Nt= No x 2^N ; N= time incubated/ generation time
Microbes attach to surfaces and live in polymer encased communities called
biofilms
examples of biofilm include
dental plaque, sink gunk, toilet scum
Most bacterial infections involve
Biofilms
Treatment of infections with biofilm are troublesome bc
they are often resistant to immune system and antibiotics
How are biofilms helpful?
Bioremediation efforts use microbes to degrade harmful chemicals are enhanced by biofilms
population of cells derived from a single cell
pure culture
pure cultures can only be obtained via
ASEPTIC TECHNIQUE
procedures that help prevent accidental introduction of unwanted microbes
aseptic technique
to obtain pure culture, you need
culture medium, aseptic technique and method to separate individual cells
If correct conditions are in place while obtaining pure culture then
single cell will multiply to form visible colony
*What is used to solidify growth medium and helps prevent bacteria to be destroyed at high temps and digestible?
***** Agar **
Method that allows air to enter but excludes contaminants
Petri Dish
Method that isolates microbes
**Streak method ***
Microorganisms grown on agar plates / in test tube are
closed systems/ batch cultures
Nutrients are not renewed/ wastes are not removed
in batch cultures/ closes systems
When cells grow in closed system/ batch cultures
population increases in stages and declines
growth pattern observed when cells are grown in closed systems
growth curve
5 stages of growth curve
Lag Phase, Log Phase, Stationary, Death Phase, Phase of Prolonged decline
method used to maintain constant cell growth by continuously adding nutrients and removing waste
Open System/ Continuous Culture
of cells don’t increase, cells begin synthesizing enzymes required for growth, delay dependent on conditions
Lag Phase
Cells divide at constant rate, primary metabolites (amino acids) & secondary metabolites (antibiotics) produced and wastes accumulate
Log (Exponential) Phase
Nutrients levels too low to sustain growth
Stationary Phase
Total number of viable cells decrease
Death Phase
Cells that survive death phase adapt to tolerate worsened conditions (cells can still multiply for a short period of time)
Phase of Prolonged Decline
Conditions that contribute to microbial growth
Temperature, Atmosphere, pH, water availability
temperature range in which growth occurs
Cardinal temperatures
Cardinal temperature ranges
Minimal (lowest growth can occur) Maximal (highest growth can occur) Optimal (growth is most rapid at this temp)
Pathogens are mesophiles
Temp requirements are 35-40 celsius
Temperature and Food Preservation
Refridgerators stay at 4 C to slow spoiliage by limiting fast growing microbes
freezing preserves food but DOES NOT
kill microbes
Microorganisms can grow in _________ environments
aerobic or anaerobic
Microbes that use molecular oxygen; produces more energy than microbes that dont
Aerobic
Microbes that can grow in absence of oxygen
Anaerobic
require oxygen for growth/ respiration; bacterial growth @ top of test tube
Obligate aerobes
facultative aerobe
do not REQUIRE oxygen for growth, BUT grows better when oxygen present; used oxygen if available for respiration, bacterial growth dispersed within test tube
cannot grow w/ oxygen present (lacks enzymes that neutralize harmful toxins of O2); does NOT use oxygen for respiration; bacterial growth
Obligate Anaerobic
grows equally well with or w/o oxygen, does not use oxygen for respiration, bacterial growth throughout test tube
Aerotolerant Anaerobe
grows only if small amounts of O2 are available; requires o2 for respiration; bacterial growth towards top of test tube
Microaerophile
Reactive Oxygen Species (ROS)
harmful by products of O2 respiration (superoxide, hydrogen peroxide) that are toxic to cells
bacterias can survives a range of pH; most microbes are ____ & optimum near _____
neutrophiles pH 5-8 ; acidophiles (pH5.5 and below) alkaliphiles (pH 8.5 and higher)
HALO
salt
ALL micro organisms require _____ for growth
WATER
If solute concentration is higher outside of cell than inside, water moves out of cell resulting in
cytoplasm dehydrating and shrink from cell wall (plasmolysis)
Process where Water flowing out the cell causing cytoplasm to dehydrate and shrink from the cell wall
Plasmolysis
Why is carbon one of the most important requirements for microbial growth?
STructural backbone of all living matter
______ use organic carbon; _______ use inorganic carbon
Heterotrophs; Autotrophs
What converts inorganic carbon to organic carbon?
Carbon fixation
Major Elements that influence Microbial Growth
C, N, P, S, K, Mg, Ca, I
Trace Elements that influence Microbial Growth
Co, Zn, Cu, Mo, Mn
Many bacteria use nitrogen from the atmosphere via
nitrogen fixation; nitrogen used for synthesizing amino acids
This is essential for nucleic acids, phospholipid synthesis, and ATP production
phosphorus
compounds that some microbes in growth medium require because it cannot synthesize them
growth factors
Microbes growth factor requirements
reflects its biosynthetic capabilities
organisms that require growth factors
Fastidious (Ex: Neisseria species)
Nutritional factors that effect microbial growth
Sunlight/ Chemical compounds
_____- extract energy from sunlight; _______ extract energy from chemicals
Phototrophs; CHemotrophs
** these medias can be used to detect or isolate a species from a mixed population **
differential & selective
determines total number of microorganisms in a sample (both living and dead)
direct cell counts
Determine number of cells capable of multiplying
Viable Cell counts
Microorganisms often live in a
biofilm
Microorganisms grow close in associations containing multiple different species
Activities of one organism often affect growth of another
