Dr Heaphy Flashcards by Sophie Oyibo

Growth kinetics of microbial culture…

1) lag phase - preparation for active growth
2) exponential phase - maximal growth
3) stationary phase - growth = death
4) death phase - nutrient depletion, accumulation of toxic compounds

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Ways to measure growth…

Serial dilution, plate count CFUs, microscopic count

Indirect methods - turbidity and measuring metabolic activity

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Differences between eukaryotic and prokaryotic ribosomes -

-Prokaryotic 70s
Large subunit 50s, small subunit 30s

-Eukaryotic 80s
Large subunit 60s, small subunit 40s

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Biggest bacteria -

Thiomargarita namibiensis

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Phylogeny

Evolutionary relationships

Based on RNA sequencing

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Smallest bacteria -

Mycoplasma

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Transformation =

Uptake of DNA released into environment by death of bacteria

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Transduction -

Phage-dependent carry over of bacterial DNA from one infected cell to the next

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Conjugation -

Plasmid-dependent DNA transfer between bacteria

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Virus =

Obligate intracellular parasite

Rod shaped or spherical

20-400nM = submicroscopic

Lack genetic info and the can’t do protein synthesis

The outer surface responsible for recognition of the host cell.

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Prions =

Associated with infectious and inherited disease

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Determine virus structure using…

X Ray crystallography

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Capsid function…

Outer shell of a virus,

to protect the fragile nucleus acid from shearing, uv irradiation

Recognition of the host cell

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Phases of virus replication:

phase 1) eclipse phases:

1) Eclipse phase - low amounts of parental infectious material present
Genome replication has been initiated
Duration = min/hours

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Phases of virus replication:

Phase 2) maturation phase:

2) maturation phase - viral material accumulates in cell or surrounding medium
Cells infected with lytic viruses die, viral production stops = Numbers slowly decrease
Cells infected with non lytic viruses can continue to produce particles

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Bacteria :

Prokaryotic 
No nucleus
Genome is present in cytoplasm
Small
Simple cellular organisation 
Sting petidoglycen cell wall 
Binary fission replication

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Gram positive bacteria -

Cell wall is thicker and contains more petidoglycen

= stains purple with crystal violet stain

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Gram negative bacteria -

Thin layer of peptidoglycan in the cell wall = doesn’t stain purple with crystal violet
When a counterstain is used stains pink

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viral replication:

1) Attachment and penetration
2) Uncoating = the virus expresses its genome
3) nucleic acid and protein synthesis
4) Assembly and exit via cell lysis or budding through cell membranes

eukaryotic cells only translates monocistronic messages. Virus must therefore …

make a polyprotein which can be cleaved,
or have a different message for each protein
or make sure that polycistronic messages can be read e.g. internal initiation sites can be used.

pathogens =

micro-organisms that cause disease

viruses, bacteria, fungi including yeasts and amoebae

parasites =

larger pathogens e.g. Plasmodium.

Opportunistic pathogens -

do not normally cause disease
live in host as commensals
may cause disease when body is compromised

Salmonella -

typhoid fever, invades gut wall, enters blood and lymph systems, systemic spread

Mycobacterium tuberculosis -

induces tubercles that result in necrosis of lung tissue and possible systemic spread via blood-stream

HIV -

causes AIDs = reduces immunological defence.

Horizontal transmission =

``` aerosols coughing or sneezing water droplets fragments of mucus expelled ingestion of contaminated food/water by vector bodily contact sexually transmitted diseases ```

Vertical transmission =

from mother to offspring

Transmission not sufficient to cause infection...

...also need breach host defence mechanisms.

example of course of infectious disease:

1) Contact 2) Incubation period - no symptoms, pathogen reaches site of infection, reproduces to critical population size. 3) Prodromal period - general symptoms of distress. 4) Acute phase - specific symptoms appear. 5) Crisis - body temp reaches dangerous level, death possible. 6) Decline period - immune system prevents virus replication, profuse sweating releases excessive heat. 7) Convalescence - restoration of normal health, can have life-long immunity.

Innate immunity =

immediate response Non-specific general barriers to infection e.g. skin, fever, Body secretions, mucous membranes, inflammation

Adaptive immunity =

A more specific response with memory characteristics

neutrophils =

Engulf bacteria - phagocytosis and | Kill them

mast cells =

release histamine, increase lymph flow, recruit immune cells

genome =

all the cellular DNA in an organism

Genome assembly relies on...

...identifying overlapping sequences

B lymphocytes -

plasma cells = Make antibodies B memory cells = immunological memory

T lymphocytes -

T helper cells = release cytokines that stimulate B cells and stimulate phagocytosis T killer cells = kill host body cells that display a foreign antigen T memory cells = long term immunity

antigen =

molecules on the surface of a pathogen that will trigger the specific immune response

cytokines =

cell signalling molecule that are produced by phagocytes to inform body it is under attack

opsonise =

proteins that bind to the antigen and allow phagocytes to bind

phagocytes (neutrophils) =

engulfs pathogen by endocytosis traps it in an phagosome which fuses with a lysosome and releases lytic enzymes

opsonisation =

antibody binds and sets off a chain reaction with blood proteins = pathogen bursts

agglutination =

antibodies join together many pathogens which are easier to engulf

anti-toxins / neutralisation =

antibodies neutralise toxins produce by pathogens

batch culture fermentation =

microorganisms + nutrients are added once and products are removed at the end

continuous culture fermentation =

nutrients are added and products are removed at regular intervals