BACTERIAL GROWTH REQUIREMENTS - MICROPARA

22問 • 1年前

JHAYS

通報

問題一覧

two groups based on their carbon source

AUTOTROPHS/LITHOTROPHS, HETEROTROPHS/ORGANOTROPHS

2 GROUPS • utilize inorganic compounds for their carbon source

AUTOTROPHS

2 GROUPS organic compounds such as glucose serve as the carbon source

HETEROTROPHS

BACTERIA DERIVE ENERGY BY 2 MEANS:

SUNLIGHT, INORGANIC SUBSTANCE

Bacterial cell is made up mostly of _____

WATER

Organisms that require oxygen for optimal growth are called _____

AEROBES

those that cannot survive in the presence of oxygen are called _______.

ANAEROBES

are those which can grow in the presence or absence of oxygen

FACULTATIVE ORGANISMS

Bacteria may be grouped into three based on their temperature requirements: - those that require high temperature

THERMOPHILES

Bacteria may be grouped into three based on their temperature requirements: - those that require temperature of 20°C – 40 °C

MESOPHILES

Bacteria may be grouped into three based on their temperature requirements: - those that require temperature of 10 °C–20 °C

PSYCHROPHILES

are organisms that grow best in pH < 6.0

ACIDOPHILES

grow best at pH of 7.0–7.2

NEUTROPHILES

are those that grow best at pH of 8.4 – 9.0.

ALKALOPHILES

Organisms that require salt for growth are called

HALOPHILES

are those that need high osmotic pressure for maximal growth.

OSMOPHILES

Based on their nutritional and physical requirements, most medically important bacteria are

CHEMOORGANOTROPHS, FACULTATIVE, MESOPHILES, NEUTROPHILES

BACTERIAL GROWTH CURVE

LAG PHASE, LOG PHASE, STATIONARY PHASE, DEATH PHASE, SURVIVAL PHASE

BACTERIAL GROWTH CURVE • period of adjustment for the bacteria in the new environment • no appreciable increase in the number of microorganisms. • increased metabolic activity • to synthesize DNA • secrete enzymes which might not be present in their new environment but which are needed by the organism. • Bacteria attain their maximum size toward the end of the lag phase • may last for 1 to 4 hours.

LAG PHASE

BACTERIAL GROWTH CURVE • characterized by rapid cell division, resulting in an increase in the number of bacteria • exhibits high metabolic activity • This is the period when the generation time or doubling time of the organism is determined • the time required for the bacterial cells to double in number • A generation time of 10 minutes means that the bacteria will double in number every 10 minutes showing exponential growth. • The average duration of this phase is about 8 hours.

LOG PHASE

BACTERIAL GROWTH CURVE • considered as the period of equilibrium • the rate of growth slows down • nutrients start to deplete • toxic wastes begin to accumulate • As a consequence, some bacterial cells may die • However, since there are still bacterial cells undergoing cell division, the number of living cells equals the number of dead cells. • Sporulation occurs towards the end of this phase • in the case of spore forming organisms • during the beginning of this phase

STATIONARY PHASE

BACTERIAL GROWTH CURVE • period of rapid cell death where the number of dead cells is greater than the number of living cells. • due to the continuous depletion of nutrients and accumulation of waste materials. • Sporulation continues to occur during this stage. • duration of this phase varies from a few hours to a few days