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Microbiology > Important microbes > Flashcards

Important microbes Flashcards

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1
Q

5 iconic bacterial genera

A 
Mycobacterium
Bacillus
Streptomyces
Escherichia
Staphylococcus
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2
Q

Mycobacterium tuberculosis

A

Causative agent of Tuberculosis
> Consumption, pthisis, wasting disease

Ancient human disease

Evidence in stone age mummies, Egypt and Peru

Discovered by Robert Koch in 1882

When discovered, TB accounted for 14% of deaths in Europe ( 33% in young adults)

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3
Q

Phylogeny of M. tuberculosis

A

high G+C Gram +ve group

Family Mycobacteriaceae
Single genus Mycobacterium

Characteristic cell walls 60-90% mycolic acids

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4
Q

Tuberculosis today

A

Estimated to affect 20% of the World’s population.

Incidence increased by poverty, malnutrition, poor sanitation, and overcrowding.

Alarming re-emergence in Europe and N. America (AIDS / multidrug resistant strains).

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5
Q

Tuberculosis, the disease

A

The infection and the disease: clear cut distinction, only 5% of infections lead to disease.

Untreated it can last a life time.

Periods of health can be interspersed with morbidity.

85% of cases found in the lung but other organs can be affected :
lymph nodes, kidneys, long bones, genital tracts,
brain and meninges

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6
Q

Detection of Tuberculosis

A

Mantoux Test
0.1 ml of PPD injected into the forearm to produce a small bleb.

X-Ray test
Tubercles seen as radio-opaque patches in lower parts of lungs

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7
Q

Cell Morphology of M. tuberculosis

A
  • Cells slightly curved or straight rods.
  • Often filamentous but fragment easily unlike Actinomycetes.
  • Samples from patients can appear as rope-like structures.
  • Grown on selective egg-potato base media
  • Colonies take ~ 6 weeks to grow and have a granular waxy morphology.
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8
Q

Other important members of the genus Mycobacterium:

A 
M. bovis (Cattle)
M. scrufulaceum (Scrofula)
M. leprae (Leprosy) 
M phlei  (Sputum and soil)
M. smegmatis (Smegma and soil)
M. marinum (sea)
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9
Q

Importance of Bacillus subtilis

A

Discovered in 1872 by Ferdinand Cohn, “subtilis” means slender (L.)

Model Experimental System:
Bacterial physiology and genetics
Cell division
Sporulation in prokaryotes

Microbial factory:
Industrial scale enzymes
Fine biochemicals
Antibiotics

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10
Q

Phylogenetic of Bacillus subtilis

and general

A

Member of the Low G+C Gram-Positive bacteria (Phylum Firmicutes).

Gram +ve rods: 2 to 3 uM long, 0.7 to 0.8 uM wide.

Heterotroph: primarily aerobic but weakly fermentative

Mesophile
G+C content 42-43 % (low)

Motile with lateral flagellae

Forms heat- and dessication-resistant endospores situated centrally- Endospores promote survival

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11
Q

Phylum Firmicutes - thr group includes the genera

A
  • Clostridium (Obligately anaerobic spore forming rods)
  • Lactobacillus
  • Steptococcus
  • Listeria
  • Mycoplasmas (Obligate endoparasites of plant and animal cells, Lack cell walls
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12
Q

Bacillus subtilis as a Bio-Factory

A

Enzymes: amylases, proteases, lipases

Amino acids and vitamins

Bio-active peptides:
antibiotic – subtilisin
surfactant/anti-bacterial/viral antibiotic - surfactin

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13
Q

Bacillus subtilis sporulation can be triggered by

A

Carbon, nitrogen or phosphorus starvation

7 hours to complete
Can survive hours of boiling or baking, most cleaning agents including ethanol

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14
Q

veg cells vs spores

A

spores has
refractile microscopic appearance when none in veg cell
higher heat resistant
higher Dessication resistant
higher Radiation resistant
lower water content
higher calcium content
higher dipicolinic acid content while absence in veg cell
lower metabolic rate
has absent of marcomolecular synthesis while high in veg cell

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15
Q

Other important Bacillus species

A

Bacillus anthracis - cause of Anthrax

Bacillus cereus - food poisoning (enterotoxins) reheated rice

Bacillus larvae, popilliae - insect pathogens

Bacillus thuringiensis - insecticidal parasporal crystals (‘BT toxin’)

Bacillus licheniformis - antibiotic producer: Bacitracin and Polymyxin B

Bacillus stearothermophilus - thermophile: source of spores for autoclave testing

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16
Q

Streptomyces

A

Bacteria that look like fungi

Mainly live in soil

Produces geosmin to give soil its characteristic smell

Produce a wide range of antibiotics including streptomycin

David Hopwood, pioneering geneticist

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17
Q

Taxonomy of Streptomyces

History

which family

Gram / G+C / oxygen requirement

A

Initially thought to be intermediate between fungi and bacteria
Discovered it has no nuclear membrane

Phylum Actinobacteria
Family Streptomycetaceae

Gram positive bacterium
High G+C content DNA (70%+)
Strict aerobes

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18
Q

Unusual structure of Streptomyces

A

Apical spores

Spores produce germ tube that grow by apical growth

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19
Q

which bacterial genera used as Antibiotic producers

How many species used
for ?

A

Streptomyces

Around 500 species of Streptomyces
Form 1-20% of the culturable population of soil
Antibiotics used against competitors
Whopping 8700 antibiotics made – more than all other bacteria and fungi combined

20
Q

Different species of Streptomyces

A 
S. coelicolor – model organism
S. griseus – antibiotic producer
S. avermitilis – antibiotic producer 
S. scabies – potato scab
S. somaliensis – human actinomycetoma
S. albus – associated with human disease
21
Q

Escherichia History

A

Discovered 1885 by German biologist Theodor Escherich

Gut (lower intestine) dweller = 100 billion-10 trillion in stools

22
Q

Taxonomy of Escherichia

A

Phylum Proteobacteria
Class Gammaproteobacteria
Family Enterobacteriaceae

Gram negative rod
48-52% G+C
Optimum growth temperature is 37oC
Facultative anaerobes

23
Q

E. coli used as a lab tool for
reason
which strain

A 
Used in virtually every biology lab
Propagating plasmids and phage
Making proteins
Model organism for many systems
K12, classic strain
24
Q

Pathogen types of E. coli

A

ET- Enterotoxin

EH- Enterohaemorrhagic

EA- Enteroaggregative

DA- Diffusely adhering

EP- Enteropathogenic

EI- Enteroinvasive

25
Q

Enteroinvasive

A
  • invasion > phagosomal rupture > intracellular movement > lateral spread to adjacent cell
26
Q

EP- Enteropathogenic

A
  • intimate attachment > actin condensation and microvillous efacement
27
Q

DA- Diffusely adhering

A
  • attach on elongated micovilli
28
Q

EA- Enteroaggregative

A
  • aggregative adherence via mucus biofilm > Delivery of cytotxin
29
Q

EH- Enterohaemorrhagic

A
  • intimate attachment of bacteria > actin condensation and microvillous effacement > delivery of shiga toxin
30
Q

ET- Enterotoxin

A
  • delivery of enterotoxin
31
Q

Different Escherichia species

A

E. coli – model organism, gut commensal, pathogen
E. blattae – cockroach gut commensal
E. albertii – diarrhea
E. fergusonii – wound pathogen

Related to Shigella, Salmonella,
Yersinia

32
Q

Staphylococcus History

A

Staphylococcus aureus discovered in Aberdeen in 1844 by Sir Alexander Ogston

Named staphyle, Greek for “bunch of grapes”

33
Q

Taxonomy of Staphylococcus

Family

G+C

A

Phylum Firmicutes
Class Bacilli
Family Staphylococcaceae

Gram positive, spherical cells, usually grow at 30-37oC, G+C 30-39%

34
Q

S. aureus and MRSA

A

Methicillin-resistant S. aureus
mecA gene, makes penicillin-binding protein

Protein binds penicillin-type antibiotics at lower affinity - highly resistant
2% S. aureus sensitive to b-lactams
Toxic shock syndrome

35
Q

Different species

A

Many different species – most are commensals, but can cause infections

S. caprae - infections
S. hyicus – exudative epidermitis in pigs
S. capitis and S. caseolyticus – commonly found in Komodo Dragon saliva

36
Q

Methanococcus jannaschii

A

Archaeon
Hyperthermophile – extreme temperatures
Obligate anaerobe – lives in absence of O2
Chemolithotroph – uses inorganic compunds for energy
Methanogen – produce methane to create energy

37
Q

The Archaea - Three general types

A

Sulphur metabolising thermophiles
Methanogens
Extreme halophiles (high salt)

38
Q

The Archaea - Two phylogenetic groups

A

Crenarchaeota, most sulphur metabolising thermophiles

Euryarchaeota, methanogens, thermophiles, S-dependant thermophiles

39
Q

Major Features of the Archaea

A

Various cell wall types, but no peptidoglycan - can get Gram-negative or -positive

Resistant to b-lactam antibiotics
Lipids - ether linked not ester linked. Can be used as a chemical signature
Very abundant and diverse

40
Q

Methanococcus Physiology

A
  • Obligate anaerobe
  • Autotropic - H2 + CO2 only substrates for growth and methane production
  • Td at 85°C pH 6.0 is 26 min
  • 0.2-1 M NaCl required for growth, optimum 0.5 M
  • Growth at pH 5.2 – pH 7.0, (optimum at pH 6.0)
  • DNA contains 31% G+C
41
Q

Evolution of Fungi

A

Zygote fungi > Zygomycota
Sac fungi > Ascomycota
Club fungi > Basidiomycota
[ loss of flagella]

Chytrids > Chytridiomycota

42
Q

Saccharomyces cerevisiae - special cell structure characteristics

A

polar bud scar

43
Q

S. cerevisiae: life cycle

A

> Diploid - (Mitosis)- 16 of chromosome pairs<
\/
Starvation - Meiosis produces - 4 ascospores within ascus: germination
\/
Haploid - (Mitosis) - 16 chromosomes
2 mating types: a and alpha (gene switching)<

[ if Nutrient rich a and alpha types fuse to give diploid]

44
Q

Yeast : vaccine biofactory

A

Hepatitis B vaccine, genetically engineered and expressed in yeast

45
Q

Other important members of the Yeast family

A

Saccharomyces pombii:
Fission yeast: model organism

Candida albicans:
~ Normal inhabitant of female reproductive tract
~ Opportunistic pathogen: cause of candidiasis,
~can infect almost all tissues of body
~ Immune compromised patients highly susceptible

46
Q

Other famous bacteria

A

Listeria and Campylobacter (food poisoning)
Clostridium (botulism)
Rhizobium (nitrogen fixation)
Neisseria (gonorrhoea), Treponema (syphilis) and Chlamydia - STDs
Legionella (Legionnaires disease)
Vibrio (cholera)
Pseudomonas (plant/animal diseases)
Lactobacillus (Food production eg yoghurt)

Microbiology (6 decks)

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