growth and nutrition Flashcards
main elements necessary for bacterial growth and nutirition
C, O2 H2 and N2
how are bacteria classified depending on their nutritional requirements
autotrophs- non parasitic –get C from CO2 and if using sunlight are called photoautotrophs and if use inorganic compounds called chemoautotrophs.
heterotrophs- parasitic - main source is carbohydrates from oxidation and fermentation
main source of N
ammonia- avalibale in the nevironment or deamination of amino acids
what is catabolism
breakdown of organic substrates and conversion into usable energy
what is anabolism
synthesis of complex molecules from simpler ones–> synthesis of complex, cellular componenets
organic growth factors
these cannot be synthesized, but require an exogenous source
- amino acids for proteins
- pureines and pyramidines for nucleic acids and co enzymes
-vitamins for co enzymes.
bacteria known to cause biofilms
staphylococcus aureus and epidermidis on catheters, prosthetic heart valves. others are streptococcus viridans and psuedomonas aeruginosa
what is a biofilm
thinly spread growth over an inert surface. bacterial community surrounds itself with glycoclayx for environmental protecteion and attachment. it also promotes genetic diversity. their nutrients are obtained from bathing fluid.
classifications of bacteria by temperature growth ranges
psychrophiles -5 -20
mesophiles 18-55
thermophiles 40-75
best pH for growth of bacteria and what is added to culture media to maintain constant pH
Best pH is 6.5-7.5. culture media contains buffer to neutralize acidic waste or acids in surrounding medium –> Peptones, amino acids, phosphate salts
osmotic pressure- bacteria in hypertonic and yhpotonic soln
hypertonis- cell cytoplasm shrinks (plyasmolysis) and inhibts cell growth.
hypertonic- lysis of cell
bacteria requiring high salt conc and others requiring high osmotic pressure called?
high salt- halophilic
extreme halophiles live in very high salt conc (obligate halophiles)
facultative halophiles - grow at 2% salt conc- some can tolerate up to 15%
meaning of facultative aerobe
better in oxygen but not necessary
aerotolerant anaerobes- meaning and example
only anaerobic growth, but continues in oxygen (does not require oxygen for growth but tolerates it).
Clostridium perfringens
microaerophile
aerobic growth - less O2 necessary. eg. Helicobacter pylori
How can you observe the diff requirements of molecular oxygen for diff types of bacteria
growing bacteria in thioglycolate tube cultures, with autoclaved thioglycolate medium. sould have a low % of agar for bacteria to be motile. autoclaving flushes out most O2. Tubes are inoculated with culture and over time O2 will slowly diffuse throughout the tube from the top.
what is generation time
average amount of time required for the population or biomass to double in size.
LAG and LOG phase
LAG phase- acclimatization/adaptation to new environment, intense metabolic activity
LOG phase- exponential constant growth, sensitive to adverse conditions like radiation and antibiotics, and generation time reaches a contsant minimum
Stationary phase and death phase
ST phase: death balances new cells, accumulation of waste products, nutrients become exhausted, slow metabolic acitivity, stable population size, dangerous shifts in pH
Death phase: death exceeds new cell formation, involution in cellular morphology
direct method for measuring microbial growth
Total Viable Count (type of plate counting method)
using miles and misra technique:
1.serial dilution
2. three plates needed for each dillution series
3. surface of agar is completely dry for better and quicker absorption
4. plate divided into 8 sectors and a drop of solution into each sector
5. drops are left to spread naturally and dry completely
6. covered and incubated upright at 37 degrees for 18-24 hours.
7. count colonies in sector with most discrete growth (2-20 colonies)
8. calcultae colony forming unit CFU
colony count x volume x dilution
