prokaryotic growth requirements

Question 1

requirements for growth

Answer 1

• nutrients available
• oxygen
• water
• temperature
• acidity and pH
• osmolality
• light and chemicals

Question 2

what nutrients do bacteria require for growth?

Answer 2

bacteria require nutrients for growth: carbohydrates, fats, proteins, vitamins, minerals, and water.

Question 3

how do bacteria use nutrients available?

Answer 3

microbes breakdown and utilise a range of nutrients by producing enzymes - bacterias genetic code dictates what enzymes they are able to produce.
bacteria vary in ability to use nitrogen sources to produce amino acids, therefore they have a varying ability to produce proteins as the amino acids build proteins.
organisms can be differentiated by their difference in the utilisation of nutrients and the wast products they produce.

Question 4

what are fastidious organisms?

Answer 4

fastidious organisms need particular materials from their environment for growth.
fastidious organisms grow slowly.

Question 5

what does obligate mean?

Answer 5

obligate requirements are compulsory for growth.

Question 6

what are facultative requirements for growth?

Answer 6

facultative requirements are optional for growth.

Question 7

what are the characteristics of aerobic organisms?

Answer 7

aerobic organisms must grow in the presence of free oxygen.
mycobacterium tuberculosis is an obligate aerobe.

Question 8

what are the characteristics of anaerobic organisms?

Answer 8

anaerobic organisms must grow in the absence of free oxygen.
clostridium is an obligate anaerobe.

Question 9

what are the characteristics of facultative aerobes/anaerobes?

Answer 9

facultative organisms can grow with or without oxygen.
E.coli is a facultative anaerobe.

Question 10

what are the characteristics of microaerophilic organisms?

Answer 10

microaerophilic organisms grow in the presence of small quantities of oxygen.
campylobacter.

Question 11

aerobic organisms

Answer 11

aerobic organisms need oxygen for respiration.
in the absence of oxygen these bacteria will be unable to respire and make ATP, cell numbers will then decrease as cells die from lack of energy for cellular processes.
aerobes have enzymes to detoxify superoxide and hydrogen peroxide.

Question 12

anaerobic organisms

Answer 12

anaerobic organisms generate energy by fermentation.
In obligate anaerobes, oxygen is toxic so they reduce in cell numbers as cells die due to damage in the presence of oxygen.
Anaerobic organisms do not have enzymes to detoxify superoxide and hydrogen peroxide.

Question 13

how are oxygen conditions tested for aerobes?

Answer 13

in aerobes, the catalase enzymes that detoxify hydrogen peroxide, and superoxide dismutase & super oxide reductase (SDR) enzymes that detoxify superoxide - are measured.
growth is measured using indirect or direct counting.

Question 14

how are oxygen conditions tested for anaerobes?

Answer 14

growth is measured using indirect or direct counting.

Question 15

water for bacterial growth

Answer 15

water is necessary for microbes to grow, but microbes cannot grow in pure water, as there are not enough nutrients for the bacteria.
some water is not available.

Question 16

water activity (Aw)

Answer 16

to measure the availability of water the water activity is used.
Aw = partial vapour pressure.
the Aw of pure water is 1.0 while that of a saturated salt solution is 0.75
most spoilage bacteria require a minimum Aw of 0.90.
an Aw of 0.85 or less suppresses the growth of organisms of public health significance.

Question 17

osmolality

Answer 17

some microorganisms have adapted to grow in conditions with low water activity, i.e, high salt concentration - they are called halophiles.
high salt concentrations are also used to retard bacterial growth in the food industry, this is because most spoilage bacteria require a minimum Aw of 0.90.

Question 18

halophiles

Answer 18

halophiles will keep a high concentration of solutes in the cytoplasm of their cells to counteract water loss to the environment.

Question 19

temperature

Answer 19

microorganisms can grow in a wide range of temperatures.
since microorganisms growth depend on water as a solvent for nutrients, frozen or boiling water inhibits their growth.

Question 20

what are the characteristics of a psychrophile?

Answer 20

psychrophiles grow best at low temperature.
psychrophiles have a minimum temperature of below 0ºc
psychrophiles have an optimum temperature of 10-15ºc.
psychrophiles have a maximum temperature of below 20ºc.

Question 21

what are the characteristics of a psychrotroph?

Answer 21

psychrotrophs grow below 25ºc
psychrotrophs are able to grow at low temperatures but prefer moderate temperatures.
psychrotrophs have a minimum temperature of 0ºc
psychrotrophs have an optimum temperature of 15-30ºc
psychrotrophs have a maximum temperature of above 25ºc

Question 22

what are the characteristics of a mesophile?

Answer 22

mesophiles grow best at or near room and body temperature.
most bateria are mesophiles, especially those living in assciation with warm-blooded animals.
mesophiles have a minimum temperature of 10-15ºc
mesophiles have an optimum temperature of 30-40ºc
mesophiles have a maximum temperature of below 45ºc

Question 23

what are the characteristics of a thermophile?

Answer 23

thermophiles grow above 40ºc
thermophiles show a wide variation in optimum and maximum temperatures.
thermophiles have a minimum temperature of 45ºc
thermophiles have an optimum temperature of 50-85ºc
thermophiles have a maximum temperature of above 100ºc.

Question 24

how do adaptations in temperature impact bacterial growth?

Answer 24

at different temperatures, the rigidity of the cell membrane will change: as the temperature decreases, rigidity increases, and, as temperature increases the membrane becomes more fluid.
psychrophilic organisms will have a greater proportion of unsaturated fatty acids to increase fluidity at low temperatures.
thermophilic organisms contain membranes that have long chain saturated fatty acids that will be thermostable. the long chain fatty acids allow them to not be affected by temperature.
enzymes will also be adapted to operate at each organisms optimum temperature, e.g. taq polymerase.

Question 25

adaptations for growth: acidity

Answer 25

most bacteria require near neutral conditions for optimal growth with minimum and maximum pH between 4 and 9.
some microorganisms change the pH of their environment by producing by-products during growth, they can change conditions such that the environemnt can no longer tolerate their growth.

Question 26

acidophiles

Answer 26

acidophiles require low pH for growth, e.g. thiobacillus.
acidophiles membranes dissolve at neutral pH
to be able to survive at low pH, cells must pump out protons (H+) to maintain a neutral cytoplasm.

Question 27

light and chemicals

Answer 27

ultraviolet (UV) light and the presence of chemical inhibitors may also affect the growth of organisms.
many treatments such as hydrogen peroxide and chlorine can kill or injure microbes - disinfectant methods.
under certain conditions those given a sub-lethal treatment are injured but can recover.

Question 28

cidal agents

Answer 28

cidal agents kill the sub-viral particle or virus/microbe.

Question 29

static agents

Answer 29

static agents inhibit growth of the sub-viral particle or virus/microbe.