Properties of Bacteria

Question 1

What cannot be resolved using a microscope?

Answer 1

Atoms (0.1 nm large)

Question 2

List some common organisms or structures in order of smallest to largest

Answer 2

Atom -> C60 (fullerene molecule) -> lipids -> lipids -> proteins -> polio virus -> flue virus -> smallpox virus -> mitochondria and bacteria -> red blood cell -> animal and plant cells -> pollen and human egg

Question 3

What are the six common bacterial shapes?

Answer 3

Coccus / cocci (round)
Bacillus / bacilli (cylindrical / rods)
Vibrio (cylindrical and curved, like a comma)
Coccobacillus (oval)
Spirillum (squiggle and rigid)
Spirochete (helical and flexible)

Question 4

Explain the process of binary fission

Answer 4

During each cell division cycle, the cell must replicate its chromosome, duplicate all of its mass, and grow in size. Through binary fission, the large cell forms a division septum with half of the cytoplasm and its components as well as one copy of the genetic information (nucleoid) on either side of the septum. Septum is completed and the cell divides into two identical daughter cells through cell separation. The process of cell division leads to the amplification of the bacterial population (one cell makes two, two makes four, four makes eight, etc. - therefore, the number of cells produced increases in a logarithmic manner.

Question 5

Name the four phases of bacterial growth

Answer 5

1. Lag phase
2. Log or exponential growth phase
3. Stationary phase
4. Death or decline phase

Question 6

Explain the lag phase

Answer 6

No increase in the number of living cells, as currently starved cells recognize food and grow in size

Question 7

Explain the log phase

Answer 7

Exponential increase in the number of living bacterial cells - when most sensitive to antibiotics and when symptoms begin

Question 8

Explain the stationary phase

Answer 8

There is a plateau in number of living bacterial cells as the rate of cell division and death are roughly equal; bacterial cells have depleted the medium and used up all the food. There is some cell turnover.

Question 9

Explain the death phase

Answer 9

Exponential decrease in the number of living bacterial cells as starved cells die

Question 10

What is generation time? What is the generation time of E. Coli?

Answer 10

Generation time is the amount of time it takes for the population to double. For E. Coli cells - at 37degC in a nutrient-rich medium - this takes 20 to 30 minutes. This means that, after 12 hours, 1 bacteria will result in 4.3 million progeny cells.

Question 11

What do prokaryotic cells have?

Answer 11

Cytoplasm (gel-like), ribosomes, nucleoids, inclusions, plasmids, flagellum (some), pili (some), capsule (some), fimbriae (some), cell walls for shape and strength, and a plasma membrane that surrounds the cytoplasm

Question 12

Why can mRNA be translated immediately after it is transcribed in bacterial cells?

Answer 12

Because bacterial cells do not have a nucleus

Question 13

How many ribosomes can a typical bacterium have?

Answer 13

Up to 15000 ribosomes

Question 14

Using E. Coli as an example, why must DNA be highly organized?

Answer 14

E. Coli cells are 1-2 microns in size, but their DNA reaches up to 1300 microns; the 1300 microns of nucleic acid is conecentrated within the nucleoid of the cell. If it is not highly organized, it will become very tangled. The DNA is present as one long, circular molecule.

Question 15

How is bacterial DNA replicated and how long does it take?

Answer 15

The DNA is replicated in a bidirectional manner - replication of the entire circle takes about 30 minutes.

Question 16

What are plasmids?

Answer 16

Plasmids are small pieces of usually circular DNA, and are between 3 000 and 21 000 base pairs in length