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Microbiology & Infectious Disease > Gram Positive Bacteria > Flashcards

Gram Positive Bacteria Flashcards

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Biology 101 flashcards
1
Q

Describe the gram positive bacteria cell wall.

A
  • it has a thick peptidoglycan cell wall

- no outer membrane

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2
Q

What are the three groups of gram positive bacteria?

A
  • Firmicutes : endospore forming (Bacillus), Nonsporulating (Staphlyococcus)
  • Mollicutes : no peptidoglycan cell wall (Mycoplasma)
  • Actinobacteria : Mycobacterium, filamentous (Streptomyces)
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3
Q

Explain the situation with spore forming bacilli (Firmicutes)
L> shape of them?
L> what is the f(x) of the spores?

A
  • gram positive RODS (their shape) hence why they are called BACILLI
  • they produce endospores: highly differentiated cells which arise by asymmetric division
  • These spores aid in survival bc they are highly resistant to heat, chemicals, radiation and dehydration. It is a dormant stage that can last for years.
  • Dispersal: wind, water and animal gut
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4
Q

What is the difference between spore formation in bacteria and fungi?

A
  • fungi form spores via sexual reproduction and therefore separate these from endospores…they are NEVER formed this way
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5
Q 
Describe Bacillus anthracis.
L> what does it cause
L> stats?
L> grows where?
L> What can it potentially be used as?
A
  • causes anthrax
  • 80% mortality when untreated
  • grows in lymph nodes and lymphatic tissue of lungs
  • death from septicaemia. haemorrhagic meningitis
  • potential bioagent in biowarfare
    L> it is very treatable via common antibodies.
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6
Q

The universal evolutionary tree is based on what?

A
  • rRNA sequence

- three domains: Eubacteria, Archaea and Eukaryotes

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7
Q

Anthrax poisoning is very common with whom?

A
  • people that work with animal hides via cuts. The toxins taken in via respiratory are very different symptoms and are more toxic this way= untreatable. The spores are what make Bacillus anthracis a potential bioweapon
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8
Q

Lifecycle of an endospore forming bacterium?

A
  • Vegetative cell –> Sporulating cell (veg cell has a developing spore inside it) –> mature spore breaks off from the cell –> germination occurs and you have a new vegetative cell.
  • poor conditions are when spore formation occurs and favourable conditions will bring the spore into germination….the spore protects DNA
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9
Q

Describe the endospore structure.
L> simple or complex?
L>contains what acid complexed with what ion?
L> core?

A
  • it is complex with many layers
  • contains dipicolinic acid complexed with Ca 2+
    L> dehydrates endospore and stabilizes DNA (resistant to UV)
  • core contains small acid soluble proteins (SASP)
    L>Bind DNA- protection from damage..less sensitive to UV damage and important as a nutrient source once germ occurs.
    L>Carbon and energy source for germination
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10
Q

Describe the two scenarios division in endospore forming bacterium depending on good or bad conditions.

A
  1. Binary fission (Good conditions) - Replication of genome occurs and the cell is split in half.
  2. Sporulation (Bad Conditions) - chromosomes are distributed along the entire cell for division–(asymmetric division)–>Full copy of genome will be in the forespore (tip of mother cell). The forespore gets engulfed in the mother cell. Spore forms (other cell dies) and it goes into a dormant stage…good conditions will bring it into germination.
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11
Q

Describe the layers of a bacterial endospore.

A
  • exosporium
  • spore coat
  • core wall
  • cortex
  • DNA
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12
Q

Differences between the vegetative cells and endospores?

A
  • calcium content is high in endospore not in veg cell
  • dipicolinic acid is absent in veg cell but present in endospore
  • enzyme activity is high in veg cell but low in endospore
  • metabolism is high in veg cell but is low or absent in endospore
  • mRNA is present in veg cell but low or absent in endospore
  • radiation resistant present in endospore but not veg
  • high water content in veg cell (80-90%) and low in endospore core (10-25%)
  • SASP is absent in veg but present in endo
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13
Q

Discuss the parasporal body in Bacillus thuringiensis.

A
  • it is toxic to insect larvae not humans.
  • it is converted to something toxic in the gut of the insect…secondary metabolite
  • insect resistant GM crops?
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14
Q

Give an example of nonsporulating Gram Positive Bacteria.

A 
- Staphylococcus 
L> aerobic, cocci
L> resistant to reduced water potential 
L> tolerate high salt 
L> many species are pigmented 
L> staphylococcus aureus (yellow) 
L> methicillin resistant staphylococcus aureus (MRSA)
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15
Q

What group of gram positive bacteria have no cell walls?

L> compensation?

A
  • Mycoplasma
    L> no cell wall visible by EM
    L> key components of peptidoglycan are absent (hence odd shape of bacterium)
    L> membranes contain sterols and lipoglycans which stabilize the membrane
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16
Q

Mycoplasma cells are considered what?

A
  • pleomorphic
    L> cells may be cocci or filaments of various lengths
  • some of the smallest organisms capable of autonomous growth
17
Q

Mycoplasmas:

  • describe them
  • example?
A
  • some of the smallest organisms capable of autonomous growth - smallest genome
  • parasites that inhabit animal and plant hosts
  • often defective in several biosynthetic pathways bc they are parasites obv
  • Mycoplasma genitalium: Host associated, genome 580kbp and 470 ORFs
18
Q

Actinobacteria: Mycobacterium
L> describe them
L> example?

A
  • rod shaped organisms, can be somewhat pleomorphic
  • obligate aerobe
  • facultative intracellular parasite (can live within macrophages)
  • complex cell wall
  • Mycobacterium tuberculosis : cause of TB..discovered by Robert Koch
  • some grow very slowly…TB has a gen time of 15-20 hours (ecoli = 20min) but this allows them to go un noticed by the host immune system
19
Q

Describe the structure of the Mycobacterial cell wall.

A
  • gram positive even though it doesn’t stain as one
  • Plasma Membrane
  • Peptidoglycan
  • Arabinogalactin
  • Mycolic Acids
20
Q

Filamentous Actinomycetes: Streptomyces.

L> Brief description of it’s biology; what is it very similar to growth wise?

A
  • filamentous, gram positive bacteria
  • branching filaments: produce mycelium analogous to mycelium of filamentous fungi
  • Produce spores called conidia (asexually)
  • important secondary metabolites
  • strict aerobes that produce many extracellular enzymes (important in breaking down plant cell walls)
  • genomes are typically large
21
Q

Streptomyces:

-Ecology?

A
  • primary soil microorganism
  • over 500 species
  • abundant and important in soil
    L> major role in the cycling of carbon trapped in insoluble organic debris
    L> produce many and diverse hydrolytic exoenzymes
    L> 7 cellulases and 5 chitinases
22
Q

Explain Streptomyces coelicolor life cycle.

A

-vegetative hyphae emerge from germinating spore
- mycelial growth: tip extension gives filaments, few cell walls, many copies of the genome in each cell, elongate and branch on the surface and penetrate the medium
- Nutrient depletion results in a switch to growth of aerial hyphae
L> complex signalling cascade, production of a surfactant that coats some emerging filaments this allows them to grow away from the substrate, substrate mycelia used as nutrient source
- Once aerial hyphal growth stops synchronous, multiple septation to give rise to prespore compartments (one copy of genome)
- Mature and develop characteristic grey pigment

23
Q

Describe spore formation in Streptomyces.

A
  • spores produced when colony ages
  • aerial filaments (sporophores)
    L> Multinucleated, cross walls form, individual cells develop into spores
  • spores are for survival and dispersal
24
Q

Describe streptomyces wtr antibiotic production

A
  • secondary metabolites
  • 50% of all isolated streptomyces produce antibodies
  • over 500 antibodies produced by them
  • approx 50 with human, veterinary or industrial applications
  • Ex: Aminoglycosides, Tetracyclines
  • production is linked to sporulation
  • potential survival strategy?? Decrease competition by producing secondary metabolites to continue to grow aerial hyphae via clearing area around it.
25
Q

Describe some characteristics of conidia?

A
  • formed at end of aerial hyphae
  • resistant to dehydration
  • dormant but more active than endospores wtr metabolism
  • formed by the septation of terminal aerial filaments
  • role in dispersal and survival in adverse conditions

Microbiology & Infectious Disease (27 decks)

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