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2.1 Fundamentals Of Microbiology > Bacterial Structure > Flashcards

Bacterial Structure Flashcards

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1
Q

Explain the tree of life?

A

Carl Woese - organisms in 3 domains based on cell wall composition, cell membrane composition, & RNA sequence - bacteria, archaea, eucarya - close on tree=closely related

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2
Q

Explain prokaryotic cells?

A

1-10μm & simple - no membrane bound organelles, no microtubules, divide via binary fission, metabolically active, tolerant of extreme conditions, 70s ribosome, & single chromosome (no nuclear membrane)

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3
Q

Explain eukaryotic cells?

A

10-100μm, complex compartmentalised interior, mitotic cell division, aerobic respiration, photosynthesis, & fermentation only, 80s ribosome, linear chromosome enclosed in a nuclear membrane

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4
Q

Mention the morphologies and which ones are usually pathogenic?

A

Pathogenic - coccus, bacillus, spirillum, spirochete
Non-pathogenic - filamentous & appendaged bacteria (hyphae & stalks)

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5
Q

Explain different type of cocci bacteria & examples?

A

Cocci - round
Diplococci - duplicates once - Streptococcus pneumoniae
Streptococci - long chain in 1 direction - Streptococcus pyogenes
Tetrad - 4 cells - duplicate in x & y direction - Aerococcus
Sarcinae - 8 cells - duplicate in x, y, & z - Sarcina ventriculi
Staphylococci - duplicate in all directions - Staphylococcus aureus

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6
Q

Explain different types of bacilli and examples?

A

Single - bacillus subtilis
Diplobacilli - 2 bacilli duplicated & joined at end - Moraxella bovis
Streptobacilli - long chain - Streptobacillus moniliformis
Coccobacillus - short stubby rod - Haemophilus influenzae

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7
Q

Explain different types of Spirilla and examples?

A

Vibrio - arched rod - Vibrio cholerae
Spirillum - short spiraled - Helicobacter pylori
Spirochete - long spiraled - Treponema pallidum

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8
Q

Explain other shapes of bacteria and examples?

A

Filamentous - Candidatus
Star-shaped - Stella
Rectangular bacteria - Holoarcula
Pleomorphic (no cell wall & any shape) - Mycoplasma

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9
Q

Give an example of the size ranges of bacteria?

A

Smallest = Mycoplasma gallicepticum (200-300nm)
Average = E. coli (1-6μm)
Largest = Thiomargarita namibiensis - Namibia - (0.1-0.3mm but have reached 0.75mm)

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10
Q

What is the Glycocalyx?

A

Polysaccharide material outside of cell, capsule if attached - slime layer if not attached to cell

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11
Q

What is the lipopolysaccharide?

A

Gram - outer membrane - lipid A (endotoxin - embedded in membrane), core oligosaccharide, & O-antigen (highly variable & recognised by immune cells)

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12
Q

How do spirochetes move?

A

Axial filaments encased in Gram - outer membrane - rotates to give corkscrew-motility - penetration of viscous substrates & tissues

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13
Q

What are flagella?

A

Long thin structure made up of protein subunits (flagellin) - motile swimming(1 bacterium in fluid) & swarming(group over flat surface) - one end attached to cytoplasmic membrane - H+ ions cause the segment to spin & flagellum moves

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14
Q

Explain the different types of flagella?

A

Peritrichous - flagella arranged all over cell - move by bundling at one end - flagella pushed apart causing it to tumble
Polar monotrichous - 1 flagellum at end
Polar lophtrichous - multiple flagella at one end

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15
Q

How do polar reversible flagella work?

A

Changes rotation direction to change direction

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16
Q

How do unidirectional flagella work?

A

1 direction - cell stops & reorients to change direction

17
Q

What are the bristle like fibres on cells called?

A

Fimnriae & Pili

18
Q

What are Fimbriae?

A

Shorter than flagella & more numerous, made of proteins, not all bacteria, adhere to surfaces e.g. tissue

19
Q

What are Pili?

A

Longer than fimbriae & less numerous, attachment to tissue, motility, & conjugation
Twitching Motility - propulsion of type IV pili - pilus extends & grab surface, retraction-motor for extension/retraction
Conjugation - conjugation pilus joins 2 cells & plasmid or piece of chromosomal DNA donated

20
Q

What is the nucleoid?

A

DNA aggregated in dense area - no nuclear membrane - singular, circular double stranded DNA - (5 Mbp) - E. coli = circumference of 1.6mm must fit into 5μm cell - organised to enable transcription - supercoiling by gyrase & topoisomerase (50 supercoiled domains) - stabilised by structural proteins

21
Q

Human genome size vs. E. coli genome size?

A

3.2 Gbp & 5 Mbp

22
Q

What is a plasmid?

A

Circular double stranded DNA - not essential but beneficial - 1)resistance to antibiotics (Rbk of E. coli) 2)fertility - conjugation & DNA transfer (F of E. coli) 3)Killer - synthesis of toxins that kill other bacteria (Col of E. Coli for calicin production) 4) Degradation enzymes for metabolism of unusual molecules (TOL of P. putida for toluene metabolism)

23
Q

What are bacterial ribosomes?

A

Translate mRNA into proteins - 10,000/cell - 70s ribosome = 30s subunit (16s rRNA & 21 proteins) & 50s subunit (23s rRNA, 5s rRNA, & 30 proteins) - used to identify bacteria

24
Q

What does the s stand for in ribosomes?

A

Svedberg Unit - measure how quickly particles sediment in an ultracentrifuge

25
Q

What are storage granules?

A

Vary in size, number, & content - energy storage & structural building blocks - poly-b-hydroxybutyrate (PHB) - contains glycogen, polyphosphate, iron oxide, or elemental sulfur

26
Q

What are magnetosomes?

A

Aquatic prokaryote - intracellular inclusions of iron mineral magnetite (Fe3O4) - permanent magnetic dipole - orient themselves & migrate towards along geomagnetic field lines

27
Q

What are gas vesicles?

A

Gas-filled structure made of protein - buoyancy - motility (position themselves in water for optimum light) - cyanobacteria

28
Q

What are cyanobacteria most similar to?

A

Gram positive bacteria

29
Q

What are crystalline inclusions

A

BT toxin - protein from Bacillus thuringiensis - transferred into corn - corn borer ingests protein - penetrates & collapse cell lining gut & insect dies

30
Q

What is sporulation?

A

Production of endospore - cellular differentiation - >200 genes - terminal, subterminal, central

31
Q

What is germination?

A

Endospores convert back to vegetative cells very quickly

32
Q

What state are bacterial cells in favourable conditions?

A

Vegetative

33
Q

What are endospores?

A

Form in inert forms - found in soil bacillus & clostridium genera - triggered by environmental distress e.g. nutrient starvation - resistant to heat, drying, freezing, radiation, & chemicals - survive for millions of years

34
Q

Name some bacteria that form endospores?

A

Bacillus anthracis (anthrax)
Clostridium tetani (tetanus)
Clostridium botulinum (botulism)

2.1 Fundamentals Of Microbiology (8 decks)

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