Bacterial Growth, Reproduction & Habitats

What type of reproduction is binary fission?

Asexual reproduction.

What happens to chromosomes during binary fission?

They duplicate.

What happens to the chromosomes as the bacterial cell elongates?

The daughter chromosomes are pulled to separate poles of the cell.

What happens to the cell membrane and cell wall during binary fission?

They grow and divide the cell into two identical daughter cells.

What is conjugation?

Horizontal gene transfer (sexual).

What structure is involved in conjugation?

The F pilus.

What happens during conjugation?

The F pilus extends to another cell and disassembles, pulling the cells together so genetic material can be transferred.

What genetic material can be transferred during conjugation?

Plasmid and, in some cases, chromosomal DNA.

What happens to the recipient cell after conjugation?

It contains some genetic information from the donor cell as well as its original genetic information.

What are the four phases of the bacterial growth curve?

Lag, log, stationary and death.

What happens during the lag phase?

There is no growth; cells are adapting to the new environment.

What happens during the log phase?

There is exponential cell growth, with cells doubling at regular intervals.

What happens during the stationary phase?

Cell growth is equal to cell death.

What happens during the death phase?

The number of cells dying is higher than the number of new cells produced, usually due to limited resources.

What are psychrophiles?

Bacteria that thrive in cold temperatures (0°C to 20°C).

What are mesophiles?

Bacteria that prefer moderate temperatures (20°C to 45°C), including many human-associated bacteria.

What are thermophiles?

Bacteria that thrive in high temperatures (45°C to 80°C).

What are hyperthermophiles?

Bacteria that require extremely high temperatures.

What are obligate aerobes?

Bacteria that require oxygen for growth.

What are obligate anaerobes?

Bacteria that cannot tolerate oxygen and only grow in its absence.

What are facultative anaerobes?

Bacteria that thrive in oxygen but can grow without it.

What are aerotolerant anaerobes?

Bacteria that are indifferent to oxygen levels.

What are microaerophiles?

Bacteria that require low levels of oxygen for growth.

How does reduced oxygen affect bacterial growth?

It can lengthen the lag phase, slow the log phase, reduce the total number of cells in the stationary phase and cause the death phase to begin earlier.

How does reduced nutrients affect bacterial growth?

It can lengthen the lag phase, slow the log phase, reduce the total number of cells in the stationary phase and cause the death phase to begin earlier.

How do increased toxins affect bacterial growth?

They can lengthen the lag phase, slow the log phase, reduce the total number of cells in the stationary phase and cause the death phase to begin earlier.

What may bacteria produce during the death phase if they are able to?

Endospores.

Why can pH limit bacterial growth?

Bacterial enzymes rely on a particular pH, and changes in pH can disrupt bonding and reduce enzyme-substrate interactions.

What are acidophiles, neutrophiles and alkaliphiles?

Acidophiles thrive below pH 5.5; neutrophiles prefer around pH 7; alkaliphiles thrive above pH 8.

What are the key pH ranges to remember?

Acidophiles: