Lecture 17 : Bacteria Classification And Morphology

Question 1

What is the definition of Microbiology?

Answer 1

Study of microscopic living organisms

Question 2

What are microorganisms?

Answer 2

Organisms which are ubiquitous (present everywhere) and include

• Prokaryote
• Eukaryote ( fungi and protists )

Question 3

Definition of Taxonomy?

Answer 3

Identification and naming of organisms

Question 4

How do we name organisms?

Answer 4

Binomial (two part) scientific name in Latin

• genus
• species

Question 5

How do we classify?

Answer 5

• Linnaean hierarchy ( species is the smallest unit)

- species, Genus, Family, order, class, phylum, kingdom, domain

Question 6

Describe Bacteria

Answer 6

• domain and kingdom
• can’t be seen w/naked eye
• no nuclear envelope or membrane- Enclosed organelles.
• circular chromosome present.
• peptidoglycan present
• 1 type of polymerase
• F- methionine initiator
• inhibited by antibiotics
• no histone

Question 7

Describe Archaea:

Answer 7

• domain and kingdom
• can’t be seen with naked eye
• no nuclear envelope or membrane enclosed organelles.
• circular chromosome present.
• no peptidoglycan
• more than one rna polymerase
• methionine initiator
• not inhibited by anti-biotics
• histone present

Question 8

Describe eukarya:

Answer 8

• nuclear envelope present + membrane enclosed organelles
• linear chromosomes
• no peptidoglycan
• more than one kind rna polymerase
• methionine initiator
• not inhibited by bacteria
• histones present

Question 9

How are prokaryotes and eukaryotes classified?

Answer 9

• on cell structure and organization

- NOT BASED on domain or kingdom or hierarchy

Question 10

Describe Bacterial Classification?

Answer 10

• Practical use of classification is identification
• conventional classification of bacteria is based on phenotypic (visible) similarities and differences
• molecular classification is based on evolutionary relatedness

Question 11

What are the phenotypic characteristics used in conventional classification?

Answer 11

• cell wall, shape, size
• presence of flagella, pili, capsule
• ability to form spores

Question 12

What are the 3 basic shapes of bacteria?

Answer 12

Cocci - round shape
Bacilli - rod shaped
Spiral

Question 13

How are bacteria divided using conventional bacterial classification? And what are the 3 types?

Answer 13

• cell wall characteristics and staining with a gram stain
• gram positive
• acid-fast bacteria
• gram negative

Question 14

Describe and give examples of Gram-positive bacteria:

Answer 14

• thigh peptidoglycan layer
• only one cytoplasmic lipid bilayer membrane
• lower lipid content
• most contain cell wall ( streptococci, staphylococci, clostridia )
• some don’t have a cell wall ( mycoplasma )
• appear as pairs/chains/clusters for cocci
• appear as regular/irregular and sporing/non-sporting for rods

Question 15

Describe acid fast bacteria with unique cell walls:

Answer 15

• acid-fast cell wall
• do not stain well with gram stain
• included with gram positive bacteria based on molecular classification
• to main genera
• mycobacterium
• nocardia

Question 16

Describe gram negative bacteria:

Answer 16

• thinner peptidoglycan
• 2 (cytoplasmic and outer) lipid bilayer membranes
• higher lipid content
• ( escherichia, salmonellae, vibrio, neisseria, spirochete)
• some without cell wall
• chlamydia
• rods (bacilli)
• cocci
• spirochete (spiral)
• obligate intracellular bacteria ,( rickettsia cell wall present) + chlamydia (no cell wall)

Question 17

What is molecular classification based on?

Answer 17

• evolutionary relatedness ( common ancestry )