Diversity and Biology of Bacteria 1

Question 1

Which of the following is FALSE regarding plasmids?

1. They are essential for bacterial replication, growth and survival
2. They are extra-chromosomal DNA
3. They can confer protective traits
4. They are important genetic tools in molecular biology labs
5. They can replicate autonomous

quiz

Answer 1

5. They can replicate autonomous

Plasmids are extrachromosomal DNA genetic elements (pieces of DNA) that exist in the cytosol of many bacteria and replicate independently of the chromosomal DNA. They usually carry genes for specialized functions that provide a selective advantage.

Question 2

Gram staining for bacteria is widely use in microbiology allowing the classification of bacteria into two major groups: Gram positive and Gram-negative bacteria. The differential staining of both groups is due to differences in the…

• Cytosolic components
• Structure of the lipid layer of the cell membrane
• Cell wall layer components
• Enzymatic content of the cells
• Mode of nutrition

quiz

Answer 2

Cell wall layer components

The Gram stain allows both to observe the bacterial cell morphology and to classify the bacteria in two main groups based on the structural and compositional characteristics of their cell wall. There are other bacteriological staining techniques that can be applied to reveal different characteristics, for example the acid-fast (Ziehl-Nielsen) stain for mycobacteria and related mycolic acid-containing Actinobacteria.

Question 3

What techniques/techology is used to observe bacteria?

Answer 3

1. can see them on agar plates with optical microscope
2. see structure using electron microscope

Question 4

What are some examples of bacterial diseases? What threat do they pose to human health?

Answer 4

Cholera, Black death, Tuberculosis, Bacterial meningitis,

Question 5

What is the difference between bacterial and eukaryotic cell memebranes?

Answer 5

Bacterial cell memebranes do not contain any steroids (ie cholesterol)

Question 6

What is the benefit of bacteria not having a nucleus?

Answer 6

There is no membrane separating the DNA and ribosomes so transcription happens faster

Question 7

What is the major component of bacterial cell walls?

Answer 7

Peptidoglycan

Question 8

Whats the difference between gram positive and gram negative?

Answer 8

+ = many layers of peptidoglycan, teichoic acid
- = one layer of peptidoglycan and LPS

Think Positive-Purple-Peptidoglycan

Question 9

Which stains pink, gram pos or negative?

Answer 9

Gram negative. Gram pos stains purple

Question 10

What is the problem with gram staining acid-fast cell wall/ Mycobacterium?

Answer 10

They have a large amount of waxes (mycolic acid) which prevents die from entering. Have to first heat the bacteria to remove mycolic acid and then use a special dye