BIOL121 bacterial nutrition and growth

what are the 2 types of nutrients needed for bacterial growth

-macroelements (macronutrients): required in large amounts, present in all cells

-microelements (micronutrients): required in small amounts, not required by all organisms

what are the macroelements required by bacteria?

-carbon, oxygen, hydrogen, nitrogen, phosphorus, sulphur - components of proteins, nucleic acids, carbs, lipids

-potassium - some enzyme activity

-calcium - stabilises cell wall

-magnesium - stabilises ribosomes, membranes, DNA

-iron - part of enzymes and electron transport proteins

what are the microelements that are components of various enzymes?

-copper

-zinc

-nickel

-vanadium

-selenium

what are the 3 types of bacterial media?

1. culture media (singular, medium): nutrient solutions/solid media that provide all the elements required for growth

2. chemically defined media: exact chemical composition is known

3. complex media: exact chemical composition unknown, made of digests of complex material like milk protein, beef, soybeans, yeast

how do we grow bacteria in the lab?

solid culture media: nutrient agar plates

what is the process of binary fission?

1. DNA replication

2. cell elongation

3. septum formation

4. cell separation

what is generation time?

time needed for a population to double

doubling time = generation time

what is exponential growth?

growth with a constant doubling time

what is a batch culture?

culture is grown in a closed system, no additional nutrients are added and no bacterial product is removed during the culture period

what are the 4 phases of batch culture?

1. lag phase: time interval between inoculation and maximal division rate, cells adjust to new environment

2. log (exponential phase): bacteria grow exponentially, constant doubling time, growth rate is maximal

3. stationary phase: bacteria can no longer reproduce but are still alive, no nutrients left, growth inhibited by bacterial products

4. death (decline) phase: bacteria die

culturable media?

can be grown on media

viable cells?

some can be cultured

some are viable but nonculturable: in a state of very low metabolic activity, do not divide, are alive and have the ability to become culturable once resuscitated

what are the 3 types of cell count?

1. total/direct count: non-specific dye that stains all bacteria

2. viable count: uses fluorescent activity dyes, counts all cells with activityy

3. culturable count: counts cells that can form colonies on solid media, or increase turbidity in liquid media

how do you measure bacterial growth and what are the adv/disadv?

-direct: microscopic count

-easy and fast

x uses special microscope counting slide

x does not differentiate between live and dead bacteria

-1:10 serial dilution obtains appropriate colony numbers

how do you measure bacterial growth turbidity?

-indirect measure

-cell suspension looks cloudy (turbid), cells scatter light passing through the suspension

-use a spectrophotometer to measure turbidity of bacterial growth (absorbance/transmittance)

what are the metabolic classifications of bacteria?

CARBON SOURCES:

-heterotrophs: require organic molecules made by other organisms

-autotrophs: CO₂ is principal carbon source

ENERGY SOURCES:
-phototrophs: use light as an energy source to produce ATP

-chemotrophs: oxidise organic or inorganic compounds

what are the 4 environmental effects on bacterial growth?

-oxygen

obligate aerobes need

obligate anaerobes cannot grow

facultative anaerobes with/without

-temp

psychrophiles best below 15

mesophiles 20-40

thermophiles 45-80

hyperthermophiles above 80

-pH

acidophiles best in acidic habitats like volcanic soils and waters, gastric juices

alkaliphiles best in alkaline habitats like extremely alkaline soda lakes, carbonate soils

-osmolarity

halophiles grow in habitats with high soil concentration (sodium chloride)

mild halophiles 1-6% NaCl

moderate halophiles 7-15% NaCl

extreme halophiles 15-30% NaCl