Microbiology 3 Flashcards by Zahra Tariq 12D

on a large scale what do bacteria form?

colonies

aggregates of individual bacteria

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what can bacteria take on?

different shapes, colours, sizes

depends on species

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what is the physical appearance of bacteria known as?

morphology

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what does the size range of bacteria?

1-10 micrometres

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give the 3 main shapes of bacteria?

cocci (spheres)
bacilli (rod shaped)
spiral bacteria

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what are monococcus bacteria?

single cells

e.g. micrococcus flavus

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what are diplococcus bacteria?

paired cells

e.g. nisseria gonorrhoeae

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what are staphylococci?

grouped cells

e.g. staphylococcus aureus

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what are streptococci?

chained cells

e.g. streptococcus pyogenes

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what are tetrads?

groups of 4 cocci in the same plane

e.g. micrococcus luteus

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what are sarcina?

cuboidal arrangements of 8 cocci

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what is a bacillus?

single rod

e.g. bacillus cereus

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what are diplobacilli?

two bacilli side by side

e.g. coxiella burnetii

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what are streptobacilli?

chains of bacilli

e.g. streptobacillus monoliformis (rat bite fever)

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what is a spirellum?

a rigid spiral gram negative bacterium

e.g. campylobacter jejuni / h.pylori

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what is a spirochete?

thin, long, more flexible bacterium

e.g. treponema palladium

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bacterial cells can adapt … … to environmental changed than eukaryotic cells

more readily

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what are the structural components of bacterial cells?

cell wall

- plasma membrane

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what are the genetic components of bacterial cells?

nucleoid

- plasmid

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what is the protein production component of bacterial cells?

ribosomes

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what are the motility components of bacterial cells?

flagella

- pilli

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what are the specialist structures of bacterial cells?

endopores

- capsules and slime

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what is the purpose of a cell wall for bacterial cells?

provides shape

- protects against osmotic lysis

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bacteria can be divided into 2 major groups depending on structure.

what are they?

gram positive - cells have single plasma membrane

- gram negative - have 2 plasma membranes

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what is peptidoglycan?

polymer of sugar and amino acids - alternating residues of beta-(1,4) linked N- acetylglucosamine (NAG) and N- acetylmuramic acid - attached to NAM = chain of 3-5 AA

the peptidoglycan layer lets particles …. through in both gram positive and gram negative

< or equal to 2nm

how much of the cell weight is gram positive?

90%

how much of the cell weight is gram negative?

10%

what does the plasma membrane comprise of?

- lipid bilayer - proteins - lipopolysaccharide (gram neg) - retains cytoplasm and separates internal and external enviro

what are the properties of the plasma membrane?

- provides support for proteins | - selectively permeable

what does the lipid bilayer comprise of?

- amphipathic phospholipids - hydrophilic head points out - hydrophobic tail points in - NO sterols (cholesterol) - pentacyclic hepanoids

what are the 2 main types of membrane proteins?

- integral | - peripheral

integral proteins?

- 75% membrane proteins - tightly attached/stretched across lipid bilayer - ion transport

peripheral proteins?

- 25% membrane proteins - aqueous solubility - cholesterol oxidases (depletes eukaryotic cells of cholesterol)

what does the lipopolysaccharide (LPS) contribute to?

structural integrity of bacterial cells

what are the 3 domains that the LPS consists of?

- O antigen - core antigen - lipid A

what can the LPS stimulate?

pro-inflammatory immune response - small amounts can cause illness

what can endotoxemia lead to?

septic shock

what is LPS highly controlled in?

sterile manufacturing - limulus amebocyte lysate (LAL)

what is the flagella involved in?

bacterial motility

where the different types of flagella?

- monotrichous (v.cholerae) - lophotrichous - amphitrichous - peritrichous (e.coli)

what is the size of flagella?

approximately 10 micrometers - long compared to bacterial cell

what are flagella powered by?

H+ / Na+ flow

what are flagella involved in?

pathogenesis - crucial for virulence of v.cholerae - flagella propel h.pylori through mucus lining in stomach

what are pilli also known as? and where are they mainly found?

- fimbriae | - gram negative bacteria

what are the 2 main types of pilli?

- conjugative pilli (allows transfer of DNA between 2 bacteria) - type IV pilli (can generate twitching motility)

what are capsules and slime layers comprised of?

- polysaccharides | - exact composition varies by species (e.g. D-glutamic acid capsule in B. anthracis)

if organised and permanent it is a...

capsule

if loosely formed it is a...

slime layer

what are capsules and slime layers not needed for?

- in vitro growth | - have to be induced

what are capsules and slime layers useful for?

- attachment to surfaces | - protection from adverse conditions

what is the main component of bacterial genetic material?

nucleoid

properties of nucleoids?

- not membrane bound - single chromosome of double stranded DNA - DNA highly coiled and wrapped around nucleiod proteins (not same as histones)

what is the size of the bacterial genome in comparison to the human genome?

0.6-10 Mbp human genome - 3000Mbp

what are plasmids and give their properties?

extra chromosomal pieces of DNA - can replicate autonomously in host - vary in size 1->200Kbp - sometimes present in eukaryotic cells - can = transferred between cells

what are plasmids responsible for?

- antibiotic resistance | - virulence characteristics (pXO1 in B. anthracis)

what are the 2 subunits of ribosomes in bacterial cells?

- small 30s | - large 50s

what does the size, sequence and structure of bacterial cells make them a target for?

antibiotics

the ability to form spores exists in some bacterial species. most notably ...

- bacillus spp. | - clostridial spp.

what is sporulation triggered by?

adverse conditions (lack of nutrients) - acts as survival mechanism inc resistance to temp, pH, chemical biocides - metabolically inert

what human diseases is sporulation important in?

- clostridium difficile in diarrhoea (CDAD) | - anthrax caused by b.anthracis

how can bacterial endospores be viewed?

using phase contrast microscopy/stained

trichomes

chains of cells forming long filaments - cells remain attached after division - cells separate by cross walls (septa) e.g. cyanobacteria

hyphae

tube-like filaments which may/may not have septa - may form dense mycelial material - filamentous fungi e.g. streptomycetes

close spatial and physiological relationships allow what?

specialisation

what do viral structures comprise of?

- genetic material - protein coat - receptors - lipid envelope (optional)

viruses can also infect prokaryotes such as..

bacteriophages

most bacteriophages (95%) belong to the caudovirales such as...

- myoviridae - siphoviridae - podoviridae