VL2: Infectious organisms: Bacteria

Question 1

Why are infectious diseases important? Who is affected?

Answer 1

• After cardio most important cause of death
• 19% of total deaths (WHO)
• < 45 years
• poor, developed countries

Question 2

Which type of infectious diseases are most important? most infected, highest mortality(examples?)

Answer 2

Most infected people: H. pylori 50% (risk of gastric cancer), M. tuberculosis 30%

Mortality:

• Respiratory diseases (M.tuberculosis)
• Diarrheal diseases (E.coi, Vibrio cholerae, Shigella)

Question 3

Definitions of symbiotic, commensal and parasite

Answer 3

Symbiotic: benefit host and B
Commensal: one partner benefits, the other is unaffected
Parasite: one benefits, the other is harmed

Question 4

Why is Symbiotic Commensal Parasite classification sometimes flawed?

Answer 4

mutual benefit can be difficult to observe

Many significant pathogens are commensal!
It depends on location, number and host immune status

Question 5

When did microbes and animals appear?

Answer 5

Microbes: 3.5 billion years ago
Animals: <1 billion years ago

Question 6

4 important evolutionary innovations through symbiosis

Answer 6

• Eukaryotic cell (mitochondria)
• Photosynthesis (plastids)
• Colonization of land by plants (mycorrhizae fungus)
• Nitrogen fixation by plants (rhizobia in roots)

Question 7

How many B cells are in the human body compared to own cells?

Answer 7

10 times more

Question 8

How many species live in the intestine? What features have they in common?

Answer 8

• 500-1000 different species (1.5kg per person)

- mostly anaerobic

Question 9

3 steps in the development of intestinal microflora

Answer 9

1. at birth: sterile
2. colonization of newborns (oral-anal direction)
3. microflora is well established after 1 month and changes little afterwars

Question 10

How/why does the microbiome change over time?

Answer 10

Birth-Adulthood: aerobes ->anaerobes (at weaning)
can change after antibiotic treatment
otherwise stays mostly the same

Question 11

How are commensals tolerated by the immunse system? Is this always the case?

Answer 11

Carbohydrate surface structures are presented to immature immune system
anti-inflammatory mechanisms that result in tolerance to commensals
some diseases (e.g. inflammatory bowel disease) may be immune response to a normal commensal B

Question 12

1 Example skin flora, what is it for?

Answer 12

Gram positive cocci: Staphylococcus aureus
Gram positive rods: Corynebacterium
Gram-negative rods: Propionobacterium (acne)
skin flora protects skin against colonization
relatively low numbers of B

Question 13

1 Example oral cavity/ nasopharyngeal flora

Answer 13

Streptococci, 
Staphylococci, 
Propionibacterium
Haemophilus
Neisseria
Corynebacterium
Mycoplasma

Question 14

Urogenital flora (1 example)

Answer 14

Sterile except for vagina and distal 1 cm of urethra
Lactobacilli
Staphylococci

Question 15

4 examples of how B are essential for health (brief explanations)

Answer 15

1. Development
   induction of blood capillaries in intestine
2. Nutrition
   Absorption and processing of food
3. Defense
   Protection against other infecious and dangerous microbes

4 Immunity
Protection against allergies and cancers?

Question 16

which 4 criteria can be used to classify B?

Answer 16

• morphology, biochemistry, staining
• lifestyle
• molecular phylogeny (rRNA, other molecules)
• relevance to human disease

Question 17

3 Identification methods?

Answer 17

morphological characteristics
differential staining (gram, acid-fast stainign)
Biochemical tests (determines presence of B enzymes)
Morphological methods do not reflect phylogeny!!!

Question 18

6 eubacterial lifestyles?

Answer 18

• Extracellular*
• Facultatively intracellular*
• Extremophillic (mostly archea)
• Epicellular bacteria*
• Obligate intrracellular and symbiotic
• Obligate intracellular and parasitic*
• human pathogens

Question 19

3 Examples of groups (based on morphology)

Answer 19

Spirochetes (Genus Borrelia, Leptospira)
Gram positive Cocci (Streptococcus, Staphylococcus)
Endospore forming Gram-positive rods and cocci (Genus bacillus, clostridium)

Question 20

How is phylogeny determined?

Answer 20

some obtained from fossil record

for microbes mostly ased on rRNA and protein sequences

Question 21

What is a cladogram?

Answer 21

shows phylogenetic reltionships among organisms

nodes represent % simlarity between species

Question 22

3 branches of (new) tree of life

Answer 22

bacteria
archaea
eucarya

Question 23

Name 3 differences between the 3 domains of life

Answer 23

ABE
cell type: prokaryotic, prokaryotic, eukaryotic
membrane lipids: branched carbon chains, straight C, straight C
ab sensitivity: no yes no
rRNA loop: -+-
common arm of tRNA -++

Question 24

Where are most B pathogens phylogenetically?

Answer 24

mostly
Firmicutes (Gram positive)
Proteobacteria
(Spirochetes)

Question 25

Examples for classification based on type of human disease

Answer 25

• respirator tract+ ear nose throat infections (s.pneumoniae, h. influenzae, s-aureus, m.tuberculosis)
• Urinary tract infections (e.g. E.coli, enterococcus, s. epidermidis, s-aureus, p. aeruginose)
• Gastrointestinal (Salmonella, shigella, vibrio)
• wound infections
• cardiovascular infections