Microbial Structure Flashcards by Morgan Eriksson

What do eukaryotic and prokaryotic cells have in common?

Plasma membrane

Cytoplasm

DNA

Ribosomes

How well did you know this?

Not at all

Perfectly

What characteristics are specific in eukaryotes?

True nucleus

Linear DNA

DNA organised into chromosomes

Large complex ribosomes with many types of rRNA and proteins

Cytoplasm filled with large complex collection of organelles

Mitochondria

Transcription requires formation of mRNA and movement of mRNA from nucleus to cytoplasm for translation

How well did you know this?

Not at all

Perfectly

What characteristics are specific in prokaryotes?

No nucleus

Circular DNA

DNA naked

70S ribosome

No membrane bound organelles independent of plasma membrane

Mesosomes are used in respiration

Transcription and translation occur simultaneously

How well did you know this?

Not at all

Perfectly

What are the structural features of bacteria?

Capsule

Pili

Flagellae

Spores

Slime

Cell wall

How well did you know this?

Not at all

Perfectly

What is the bacterial capsule made from?

Loose polysaccharide

How well did you know this?

Not at all

Perfectly

What is the function of the bacterial capsule?

Protects from phagocytosis

Protects cell from desiccation

How well did you know this?

Not at all

Perfectly

What is pili made from?

Oligomeric pilin proteins

How well did you know this?

Not at all

Perfectly

What is the function of pili?

Appendage used for bacterial conjugation

Forms tube/bridge to enable transfer of plasmids between bacteria

How well did you know this?

Not at all

Perfectly

Characteristic of pili

Highly antigenic

How well did you know this?

Not at all

Perfectly

What is flagellae?

Organs of locomotion

How well did you know this?

Not at all

Perfectly

What is flagellae made out of?

Composed of flagellin protein

How well did you know this?

Not at all

Perfectly

What are spores?

Hard, multi-layered coats making spore difficult to kill

How well did you know this?

Not at all

Perfectly

What happens when a bacteria becomes a spore?

Metabolically inert form triggered by adverse environmental conditions

Adapted for long-term survival allowing for regrowth when conditions are desirable

How well did you know this?

Not at all

Perfectly

Example of common diseases caused by spores?

Botulism- Clostridium botulinum

Gas gangrene-Clostridium perfringes

Tetanus- Clostridium tetani

Food poisoning- Clostridium perfringes

Anthrax- Bacillus anthracis

How well did you know this?

Not at all

Perfectly

What is slime?

Polysaccharide material

How well did you know this?

Not at all

Perfectly

What is the function of slime?

Protects against immune attack

Protects against eradication by antibiotics

How well did you know this?

Not at all

Perfectly

How do you differentiate bacteria into two groups based on their cell wall?

Gram positive

Gram negative

How well did you know this?

Not at all

Perfectly

What is the structure of a gram positive cell wall?

Thich peptidoglycan wall

Followed by a phospholipid cytoplasmic membrane

How well did you know this?

Not at all

Perfectly

What is the structure of a gram negative cell wall?

An outer phospholipid membrane

Thin layer of peptidoglycan attached via lipoprotein

An inner phospholipid membrane

How well did you know this?

Not at all

Perfectly

What are the four steps in gram staining?

Primary stain

Trapping agent

Decolourisation

Counterstain

How well did you know this?

Not at all

Perfectly

What dye is used in the primary staining?

Crystal violet dye

How well did you know this?

Not at all

Perfectly

What is used as the trapping agent?

Gram’s iodine

How well did you know this?

Not at all

Perfectly

What is the outcome of the decolourisation step in gram staining?

Gram negative bacteria lose their lipopolysaccharide layer. This exposed the inner peptidoglycan layer, the coloured complexes are then washed away

Gram positive bacteria become dehydrated and traps the complexes in thicker peptidoglycan layer

How well did you know this?

Not at all

Perfectly

What is used for decolourisation?

Alcohol/acetone

How well did you know this?

Not at all

Perfectly

What is the outcome of counterstaining?

Gram negative become pink/reddish Gram positive become purple

Summarise the structure of gram positive bacteria

2 layered wall A thick peptidoglycan layer and a cytoplasmic membrane Has lipoteichoic acid

Summarise the structure of gram negative bacteria

3 layers An outer membrane Think peptidoglycan layer inside the periplasmic space Cytoplasmic membrane Has Lipopolysaccharide

Describe peptidoglycan (PGN)

Polymer of sugars and amino acids Forms a mesh-like layer outside plasma membrane

Describe lipoteichoic acid (LTA)

Complex of teichoic acid+lipids Provides cell rigidity Recognised by host immune cells

Describe lipopolysaccharide

Essential for function of outer membrane Elicits potent immune and inflammatory host response Produced endotoxins

What do outer membrane proteins do in the cell wall?

Not endotoxins but do contribute to virulence

Describe bacteria replication of genome

2 replication forks replicate DNA in a circular motion on either side of the ring

What is bacterial cell division called?

Binary fission

What is the four phases of bacterial growth?

Lag Log/exponential Stationary Death

What happens in the lag phase?

Bacteria prepare for reproduction by synthesising DNA and enzymes

What does the lag phase represent?

The period of active growth ie size. not number

What happens in the log/exponential phase?

Cells divide at maximum rate Uniform replication

What happens in the stationary phase?

The cessation of growth Exhaustion of nutrients

What happens in the death phase?

The number of dying cells start to exceed the number of newly born cells

What is bacterial recombination?

How bacteria share DNA

What are three examples of bacterial conjugation?

Conjugation Transformation Transduction

What is conjugation?

Genes are transferred through the pili tube

What is transformation?

Taking up DNA from surrounding environment

What is transduction?

Exchanging of bacterial DNA through bacteriophages

What are the different areas of bacterial classification?

Gram staining Cell shape Atmospheric preference Key enzymes Fastidiousness

What essentially is a virus?

A nucleic acid enclosed in a protein shell

What are the difference viral structural components?

Nucleic acid Capsid Envelope Spikes

What are the different forms of nucleic acid that can be found in a virus?

Double or single stranded Deoxyribonucleic or ribonucleic acid

What is the capsid?

A protein coat/shell

What forms capsid?

Composed of protein subunits called capsomeres

What are capsomeres made from?

Aggregated protomeres

What are the different shapes of capsid?

Rod-like Polyhedral Complex

Describe the viral envelope

Amorphous structure surrounding some virus Composed of lipid, protein and carbohydrate

Example of a virus with an envelope?

Herpes

Describe viral spikes

Glycoprotein projections arising from the envelope

What is the function of viral spikes?

May have enzymatic, adsorption or haemagglutinin activity

What is hemagglutination?

Clumping of RBC

How does a virus replicate?

Uses host's cellular machinery

What are the 6 steps of viral replication?

Adsorption Penetration Replication Assembly Maturation Release

What happens in the adsorption step of viral replication?

Virus binds to the host cell

What happens in the penetration step of viral replication?

Virus injects its genome into host cell via fusion, binding or ingestion

What happens in the replication step of viral replication?

Capsid digested by proteolytic enzymes Viral genome replicated using the host's cellular machinery

What happens in the assembly step of viral replication?

Viral components and enzymes are produced and begin to assemble

What happens in the maturation step of viral replication?

Virus fully develops

What happens in the release step of naked viruses in viral replication?

Viral enzymes break down bacterial cell wall RNA viruses released DNA viruses releases via autolyse or in inclusion bodies

What happens in the release step of enveloped viruses in viral replication?

Viruses migrate to either the plasma membrane or nuclear membrane Enveloped formed around nucleocapsids by "budding" of cell membrane No inclusion bodies

What are protozoa?

Single celled eukaryotes

How do we classify protozoa?

Sporozoa Flagellates Amoeba CIliates

What are sporozoa?

Intracellular parasites

What are flagellates?

Possess tail-like structures for motility

What are amoeba?

Use temporary cell-body projections called pseudopods

What are ciliates?

They move by beating multiple hair-like structures

What protozoa leads to malaria?

Plasmodium falciparum

What protozoa leads to giardiasis?

Giardia lamblia

What protozoa leads to toxoplasmosis?

Toxoplasma gondii

What protozoa leads to cryptosporidiosis?

Cryptosporidium parvum

What are fungi?

Multinucleated eukaryotic organisms

What is the wall of fungi made from?

Thick carbohydrate containing chitin and glucans

How do fungi reproduce?

Reproduce asexually by budding and occasionally by binary fission

What are fungal infection denoted by?

Mycoses

What is candidiasis and what is it caused by?

Fungal infection Candidiasis

What is cryptococcosis and what is it caused by?

Fungal infection Cryptococcus neoformans

How do you treat cryptococcosis?

Amphotericin B

What causes aspergillosis?

Aspergillus flavus

How does aspergillus flavus cause aspergillosis?

Production of aflatoxins which then are inhaled

What is ringworm caused by?

Tinea corporis

Where does ringworm effect?

Scalp, skin, fingernails, toenails and feet

What are helminths?

Parasitic worms

What are the 3 main groups f helminths?

Cestoda- tapeworms Trematoda- flukes Nematoda- roundworms

What are the four ways helminths can be transmitted?

Intermediate host Faecal-oral route Active skin penetration Injection by blood-sucking insect

What type of helminth is schistosomiasis caused by?

Fluke

What helminths cause schistosomiasis?

Schistosoma haematobium Schistosoma mansoni Schistosoma japonica

What type of helminth causes trichiuriasis?

Nematode

What helminth causes trichiuriasis?

Trichuris trichiuria

Example of a tapeworm

Taenia solium