Intro To Microbiology And Bacterial Structures (w19)

Question 1

What is a microorganism ?

Answer 1

Microorganisms (or microbes) are organisms that are too small to be seen with the unaided eye, require a microscope (except for some moulds)

Question 2

What are the 5 major groups of microbes ?

Answer 2

1) Bacteria —> Bacteriology
2) Fungi (yeasts and moulds) —> Mycology
3) Parasites (protozoa, helminths, and ectoparasites) - Parasitology
4) Microalgae —> Phycology
5) Viruses and prions —> Virology

Question 3

What id the general size order for microorganism diversity ?
- largest —> smallest

Answer 3

Moulds > Protozoa > Yeasts > Bacteria > Viruses > Prions

Question 4

What does it mean when an microorganism is acellular ?

Answer 4

Acellular - without a cellular structure (e.g. viruses and prions)

Question 5

What are the two types of classification of microorganisms ?

Answer 5

• cellular
• acellular

Question 6

What are the three different types of domain ?

Answer 6

• bacteria
• archaea
• eakarya

Question 7

When was the system for classifying biological organisms introduced ?

Answer 7

In 1990

Question 8

What is classification mainly based on ?

Answer 8

Classification mainly based on differences in the sequences of nucleotides of ribosomal RNAs (rRNA)

Question 9

What are the main features of bacteria/ archea ?

Answer 9

• the study is bacteriology
• are prokaryotes
• mostly unicellular/ monocellular

Question 10

What are the main features of fungi ?

Answer 10

• study of fungi is called mycology
• are eukaryotes
• yeasts are unicellular
• mounds are pluricellular

Question 11

What are main features of parasites ?

Answer 11

• study of parasites is parasitology
• are eukaryotes
• Protozoa are unicellular
• helminths are pluricellular

Question 12

What are features of microalgae ?

Answer 12

• study of microalgae is phycology
• mostly eukaryotic
• both unicellular and pluricellular

Question 13

What are the features of a virus ?

Answer 13

• study of virus is virology
• are acellular (no cellular structure)
• small infectious particles which consist of nucleic acid surrounded b a protective coat of proteins.
  -coat may be enclosed in lipid envelope
• don’t divide
• need to infect cell to replicate particles.

Question 14

What are features of prions ?

Answer 14

• study of prions is virology
• Simpler infectious particles made up of only proteins - no nucleic acids

Question 15

How are microorganisms essential for life on earth ?

Answer 15

• organic waste decomposition
• nitrogen fixation
• oxygen generation (photosynthesis)
• digestion and molecule generation
• production of food
• drugs/enzymes synthesis

Question 16

How can bacteria be helpful ?

Answer 16

prevent growth of pathogens
produce growth factors (e.g. vitamins B and K)
breaking down toxic molecules, boosting the immune system and antimicrobial chemicals

Question 17

What are the 4 types of arrangement of bacteria ?

Answer 17

• pairs (diplococci, diplobacilli)
• clusters (random planes - staphylococci)
• chains (one plane - streptococci, streptobacilli)
• groups of four (tetrads)

Question 18

What is binomial nomenclature ?

Answer 18

Scientific names that’s are given to species of living things

Question 19

What are bacteria and archea ?

Answer 19

• prokaryotes
• no nucleus
• without membrane-bio uni organelles and have simple organisation.

Question 20

List function of plasma membrane ?

Answer 20

• serves as a selectively permeable barrier
• controls movements of molecules across the cells
• has infoldings called mesosomes, they are the site for DNA replication and cellular respiration.

Question 21

What is the name given to the sterol-like molecules found in the plasma membrane ?

Answer 21

Hopanoids

Question 22

List functions of cell wall …

Answer 22

• Maintain bacterial cell integrity and shape
• Prevents the cell from bursting when water flows into the cell by osmosis
• Can contribute to pathogenicity (ability to cause disease)

Question 23

What is the evidence for the importance of the cell wall …

Answer 23

• Only a few bacteria do not posses cell walls (e.g. mycoplasma)
• Target of many antibiotics (anti-bacterial drugs)

Question 24

What is a peptidoglycan ?

Answer 24

An essential component of the bacterial cell wall

Question 25

What is the composition of the peptidoglycan (Murein) ?

Answer 25

• A rigid multi-layered network made up of linear chains
• Each chain is a polymer of a repeating identical disaccharide unit (made up of the following 2 monosaccharides) in long rows:
  -N-acetylglucosamine (NAG)
  -N-acetylmuramic acid (NAM)
• A tetrapeptide chain of 4/5 amino acids is linked to NAM
• Chains are linked by peptide cross bridges between tetrapeptide side chains of NAMs

Question 26

What do repetitions of peptidoglycan subunits form ?

Answer 26

Individual strands or chains

Question 27

What are bacterial transpeptidase responsible for ?

Answer 27

(Penicillin-binding proteins) are responsible for these links (peptide cross link bridges) and are the target of beta-lactams e.g. pencillins

Question 28

What do Beta-lactam antibiotics (including penicillins and other classes) to do peptidoglycan synthesis ?

Answer 28

Inhibits the peptidoglycan synthesis of the bacterial cell wall

Question 29

What is the structure or Gram +ve ?

Answer 29

• Consists of a thick structure (several layers) of peptidoglycan, separated from the plasma membrane by a thin periplasmic space
• Also contains teichoic acids, made up of an alcohol and a phosphate group (negative charge)
  -Bind to and regulate movement of cations into cell
  -Regulate cell growth and prevent cell lysis
  -Linked also to the cell membrane

Question 30

What is the structure of Gram -ve ?

Answer 30

• Cell wall is thinner, more complex and more susceptible to mechanical breakage
  Consists of:
  -a thin peptidoglycan layer
  -periplasmic space, containing degradative enzymes and lipoproteins
  -outer membrane (the most external)

Question 31

What is the functions of the outer membrane in Gram-bacteria ?

Answer 31

• Evade phagocytosis and immune system
• Permeability barrier to antibiotics (penicillin), digestive enzymes, etc

Question 32

What is the main difference between gram-positive and gram-negative cell walls ?

Answer 32

Gram positive :
- thick peptidoglycan
- teichoic acids

Gram negative:
- Thin petidoglycan
- Has an outer membrane (containing LPS,Lipoproteins and porins)
- have periplasmic space

Question 33

What is gram-staining used for ?

Answer 33

• To distinguish groups between bacteria according to their cell wall structure.
• also for better visual observation to highlight difference Rickey components in bacteria.

Question 34

List the process of gram staining ;

Answer 34

1) fixation
2) primary staining
3) mordant application
4) decolourisation
5) counterstaining

Question 35

What are the functions of the glycocalix ?

Answer 35

• Confer pathogenicity (only capsule)
• Prevent phagocytosis by host phagocytes
• Avoid desiccation by preventing water loss
• Aid in attachment to solid surfaces
• consists of the capsule and slime layer

Question 36

What are the three main components that make up the flagella ?

Answer 36

Three parts, made of protein flagellin:
- Filament: outermost region
- Hook: attaches to the filament
- Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane

Question 37

What is a sensory organelle ?

Answer 37

One which detects chemical changes and temperature changes

Question 38

What are fimbriae ?

Answer 38

Fimbriae (1-500 per bacteria)
Thin hairlike appendages that allow for attachment
Some types are involved in a twitching motility

Question 39

What are the sex pili ?

Answer 39

Sex Pili
Hair-like tubular structure
Conjugation pili involved in DNA transfer from one cell to another