Binary Fission

steps of binary fission

1. dna replication

2. cell elongation

3. septum formation

4. cytokinesis

5. cell division

The bacterial chromosome (a single circular DNA molecule) is replicated to ensure each daughter cell will have a complete copy of the genetic material

DNA replication

The cell elongates as the two copies of the chromosome move toward opposite ends of the cell.

cell elongation

The cell membrane begins to pinch in at the center, forming a septum (partition) that will divide the cell into two.

septum formation

The septum completely forms, dividing the cell into two daughter cells. Each daughter cell receives one copy of the chromosome.

cytokinesis

The two daughter cells separate, each now a new, independent cell.

cell division

2 ways genetic variation occurs in bacteria

1. mutation

2. horizontal gene transfer

transformation

Uptake of free DNA from the environment

transduction

Transfer of DNA from one bacterium to another via a bacteriophage (virus).

conjugation

Transfer of DNA through direct cell-to-cell contact, typically involving plasmids.

generation time

time it takes one cell to become two by binary fission

• varies depending on the type of bacteria

how is generation time expressed?

exponentially, and logarithmically

the bacterial growth phases is a _____ system

closed

steps of the bacteria growth phase

1. lag

2. exponential (log)

3. stationary

4. decline

lag phase

bacteria are adjusting to the environment, no division yet

log (exponential) phase

bacteria are rapidly dividing, population doubles quickly.

stationary phase

growth slows, as nutrients run low and waste builds up

death (decline) phase

bacteria die off faster than they reproduce

during decline phase, cells may _____ but remain ____

persist ; nonculturable