microbiology 4- microbial growth and evolution

What are the top 10 elements making up a bacterium?

• carbon

• oxygen

• nitrogen

• hydrogen

• phosphorus

• sulfur

• potassium

• magnesium

• calcium

• iron.

What are possible sources of carbon?

autotrophs, heterotrophs, CO2 sole, other organisms

What are possible energy sources?

phototrophs, chemotrophs, light and compound oxidation

What are possible electron sources?

lithotrophs, organotrophs, light, compound oxidation

What are the 2 ways to culture microorganisms?

liquid media/broth or solid media/agar plates

How do bacteria grow in liquid media and what do they produce?

grow as individual cells until the available nutrients run out.

produce a suspension of cells for testing

How do bacteria grow on solid media and what do they produce?

form colonies which have distinctive appearances on an agar plate.

What is undefined media?

contains chemically undefined yeast/ vegetable/meat extracts, they have batch- batch variation

What are defined media?

chemically defined and highly reproducible

What is an obligate aerobe?

cannot survive without oxygen (mycobacterium tuberculosis)

What is an obligate anaerobe?

cannot survive in presence of oxygen (clostridium difficile)

What is a facultative aerobe?

can use grow in the presence of oxygen or produce energy by fermentation ( E.coli and staphloycoccus aureus)

What is a microaerophile?

requires reduced oxygen content (higher CO2) to survive ( campylobacter jejuni)

What is an aerotolerant aerobe?

Can tolerate oxygen, but produces energy by fermentation (streptococcus mutans)

How can we work with anaerobic cultures?

anaerobic cabinets- nitrogen and hydrogen

gaspak sachets- produce co2

candle extinction- uses o2 from the air

How do bacteria most commonly reproduce?

binary fission

What do we call the time taken to produce?

generation time

What is the lag phase in bacterial growth?

no immediate increase in cell number as old cells are depleted and time is needed

What is the exponential phase?

growth and division at maximum rate and regular doubling times.

What is the stationary phase?

in a closed system, nutrients depleted and waste builds up, growth stops

What is the death phase?

severe nutrient deprivation, toxic waste built up and viable cell numbers decline.

What is primary metabolism?

includes major metabolic pathways such as energy production and release, cell synthesis and enzyme production

What is secondary metabolism?

non essential pathways such as production of natural products, secondary metabolites and increased pathogenicity.

What are the disadvantages if a flask culture closed system?

limited nutrients, atmosphere limited, limited product production

What are the advantages of a chemostat?

highly controlled growth and nutrients supplied at a constant rate.

What are the 3 growth modes of bulk culturing?

• batch- full at start

• fed batch- fill until full

• continuous- fill and overflow

What are the important criteria for bulk culturing?

maintain adequate mixing and oxygen levels, control pH, temperature and foam. initial starting concentration.

What is evolution?

changes in population overtime

What is mutation?

permanent change in a single cell, does not always cause visible change

What does a harmful or deleterious mutation cause?

decreased organism fitness

What does a beneficial or advantageous mutation cause?

increased organism fitness

What are the 3 main mechanisms by which bacteria can evolve?

• transformation- direct uptake of DNA through cell membranes

• transduction- introducing genetic material via vector

• conjugation- transfer of genetic material between two directly connected bacteria.

How can bacterial strains improve naturally?

spontaneous mutation

exposure to mutagens- random mutagenesis

genetic modifications- targeted mutagenesis

Why would bacterial strains need to improve?

they may be produced at low concentrations and need to increase efficiency, or industrially this is more cost effecient