Microbio Lecture 12 Growth Study

Biofilms harbor

microbial communities, form slime/hydrogels that stick to surfaces

bacteria communicate via

quorum sensing (cell to cell), secretes inducer (signal chem.) to attract other bacterial cells

biolfilms share nutrients, and shelter

bacteria from harmful environmental factors

biofilm formation- migrating

clump of bacteria adheres to surface

planktonic:

freely existing bacteria- as single cell rather than attached to a biofilm

biofilms can be found in digestive system and sewage treatment systems- can

clog pipes, 1000x resistant to microbiocides, involved in 70% of infections- catheters, heart valves, contact lenses, dental caries

Explain how biofilm formation is beneficial to a pathogen.

provides pathogens with a strong protective shield and survival advantages that make infections difficult to treat

Explain how microorganisms are preserved by deep-freezing and lyophilization (freeze-drying).

drastically slowing or completely stopping their metabolic activities

Preserve Bacterial cultures- deep freezing

-50 to -95C

Preserve Bacterial Cultures- Lyophilization

freeze drying, frozen -54C to -72C and dehydrated in a vacuum

If the Space Station in Earth orbit suddenly ruptured, the humans on board would die instantly from cold and the vacuum of space. Would all the bacteria in the capsule also be killed?

No not all- sudden vacuum and extreme cold mimic laboratory methods of preservation like deep-freezing and lyophilization (freeze-drying) that actually keep microorganisms alive

Bacterial growth is represented by an

increase in number of cells, not cell size

bac. divis- binary fission

cell division process used by most bacteria

bac. divis.- Budding

used by few bacterial specieis

bac. divis. conidiospores

actinomycetes

bac. divis.- fragmentation of

filaments

Generation time

time required for a bacterial cell to divide- 20 min to 24 hours

binary fission doubles

the number of cells each generation

Total number of cells =

2 ^ number of generations

growth cruves are rep.

logarithmically

Your test tube contains 64 growing bacterial cells. How many generations must pass to get 1000 cells?

3.97

Nt= Ni x 2^n

1000= 64 × 2^n

1000/64

15.65= 2^n

log2(15.65)

n= 3.97

Or, an infectious bacteria has a doubling time of 20 minutes. You start with a culture of 100 cells/ml. What will be the culture density (cells/ml) after 2h?

6400

Nt= Ni x 2^n

= 100 × 2^6

=6400

Can a complex organism, such as a beetle, reproduce by binary fission?

No- only single celled

Bacterial growth curve

few bacteria are inoculated into liquid growth medium

population of bac. counted at invervals

plot: Time (x), log10 of # of bac (y)

As bacterial culture grows,

the medium becomes turbid (can be measured at different time points)

Phases of growth

Lag, Log, Stationary (bac approach carrying capacity), death phase

Lag Phase

–No or little increase in number

–Intense metabolic activity, “tooling up” for rapid growth

Log Phase (exponential growth phase)

–Rapid reproduction, minimum constant generation time

Stationary Phase

–Growth slows as carrying capacity is approached

–Cell deaths balances number of new cells

–Diminished nutrients, accumulating wastes

Death Phase

–Deaths exceed production of new cells

–Population is decreasing logarithmically

If two mice started a family within a fixed enclosure, with a fixed food supply, would the population curve be the same as a bacterial growth curve?

idk