growth and nutrition

Question 1

main elements necessary for bacterial growth and nutirition

Answer 1

C, O2 H2 and N2

Question 2

how are bacteria classified depending on their nutritional requirements

Answer 2

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

Question 3

main source of N

Answer 3

ammonia- avalibale in the nevironment or deamination of amino acids

Question 4

what is catabolism

Answer 4

breakdown of organic substrates and conversion into usable energy

Question 5

what is anabolism

Answer 5

synthesis of complex molecules from simpler ones–> synthesis of complex, cellular componenets

Question 6

organic growth factors

Answer 6

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.

Question 7

bacteria known to cause biofilms

Answer 7

staphylococcus aureus and epidermidis on catheters, prosthetic heart valves. others are streptococcus viridans and psuedomonas aeruginosa

Question 8

what is a biofilm

Answer 8

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.

Question 9

classifications of bacteria by temperature growth ranges

Answer 9

psychrophiles -5 -20
mesophiles 18-55
thermophiles 40-75

Question 10

best pH for growth of bacteria and what is added to culture media to maintain constant pH

Answer 10

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

Question 11

osmotic pressure- bacteria in hypertonic and yhpotonic soln

Answer 11

hypertonis- cell cytoplasm shrinks (plyasmolysis) and inhibts cell growth.
hypertonic- lysis of cell

Question 12

bacteria requiring high salt conc and others requiring high osmotic pressure called?

Answer 12

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%

Question 13

meaning of facultative aerobe

Answer 13

better in oxygen but not necessary

Question 14

aerotolerant anaerobes- meaning and example

Answer 14

only anaerobic growth, but continues in oxygen (does not require oxygen for growth but tolerates it).
Clostridium perfringens

Question 15

microaerophile

Answer 15

aerobic growth - less O2 necessary. eg. Helicobacter pylori

Question 16

How can you observe the diff requirements of molecular oxygen for diff types of bacteria

Answer 16

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.

Question 17

what is generation time

Answer 17

average amount of time required for the population or biomass to double in size.

Question 18

LAG and LOG phase

Answer 18

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

Question 19

Stationary phase and death phase

Answer 19

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

Question 20

direct method for measuring microbial growth

Answer 20

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