Structure, Function, Reproduction and Classification of Micro-organisms Flashcards
Symbiotic Associations?
symbiotic organisms live in close nutritional relationships with one another
Symbiotic Associations: Commensalism?
host is not harmed, nor benefits
Symbiotic Associations: Mutualism?
both members benefit
Symbiotic Associations: Parasitism
parasitic microbe depends on host; host is harmed
disease can result
Which symbiotic association can cause disease?
parasitism, relationship is causing harm to the host
Bacteria?
prokaryotic, no nuclei, single celled, lives in pairs, chains, clusters
Why are humans so sensitive to bacteria?
bacteria is prokaryotic and humans are eukaryotic, identify bacteria as foreign
Viruses?
Acellular, not visible by microscope, microbes made of genetic material surrounded by protein coat
Can viruses make proteins? how do viruses make proteins?
can’t make their own proteins, they must infect the cell of a host to make proteins
Do viruses reproduce or replicate?
replicate
Is algae harmful to humans?
no
Fungi?
eukaryotic, has a nuclei, cell wall, organelles, obtain nutrients from other organisms
2 examples of fungi?
yeasts and molds
Which microbe is most like humans?
fungi, both eukaryotic. few differences then us.
Why do humans not handle anti fungal agent well?
because fungi is like us, few agents to destroy them
Protozoa?
eukaryotic, single celled, has a nuclei
What is more destructive and harmful to humans’ viral infections or bacterial infections?
bacterial, more severe
Example of a protozoa?
parasites
Helminths?
eukaryotic, multicellular, has a nuclei, visible with naked eye
What microbe is visible to us with our aged eye? examples?
helminths. tape worms
order these 3 microbes based on size, protozoan, virus, bacteria (small to large)
small- virus, bacteria, protozoan- large
Shape of bacterial cell?
rod shaped
What organelle of a bacterial cell is a good target for antibiotics?
ribosomes
Plasmid’s function of a bacterial cell?
carry info about resistance to a host or resistance to an antibiotic
“DNA”
Function fo a cell wall?
provides structure
Characteristics of bacterial cells?
no nucleus, smaller DNA particles as “plasmids”, ribosomes are smaller than those of eukaryotic , cell wall and cell membrane, flagella and pili
How are bacterial infections exploited?
using antibiotics, to exploit the difference b/w prokaryotic and eukaryotic cells without damaging the host’s cells
How to classify bacterial cells based on morphology?
shape, arrangement, colony morphology, external structures, capsules and spore formation
How to classify bacterial cells based on cell wall structure?
staining and microscopy; gram and acid fast stain
How to classify bacterial cells based on growth characteristics?
oxygen and energy requirements
How to classify bacterial cells based on metabolism?
carbohydrate utilization, fermentation products
How to classify bacterial cells based on molecular techniques?
DNA sequencing
Bacterial cell morphology: diplococci, streptococci, staphylococci, bacilli, coccobacilli?
diplococci= 2 round Paris cocci= round streptococci= grows in pairs and chains and always gram positive staphylococci= gram positive, grows in clusters bacilli = grows in rods coccobacilli= more rounder rods
What allows for tentative bacterial classification?
letting the bacteria grow on agar plates to allow for characteristic development
What is a flagella?
protein filaments that extend from cell membrane
Function of the flagella?
rotate 360 degrees for movement in response to stimuli, whip like motion
Flagella:
polar=?
spirillium=?
peritrichous?
polar= 1 flagella spirillium= 2 flagella peritritious= multiple flagella
Fimbriae?
straight filaments from cell wall of bacteria
shorter than flagella
not used for propulsion
Function of fimbriae?
- “pulls” the bacterium
- acts as adhesions binding to a specific host cell
Conjugation pili function?
used to transfer DNA from one bacteria to another
Bacteria: glycocalyx?
what is it made out of?
-protective substance surrounding some bacteria
acts as a force shield
-made from polysaccharides
-presence/ absence can be used for classification
Function of glycocalyx?
helps bacteria avoid phagocytosis
2 types of glycocalyx
- slime layer: prevents dehydration, allows bacteria to bind to surfaces and form a protective layer
- capsule: attached to cell wall, facilitates adherence and impairs phagocytosis
Endospores?
- defensive strategy against unfavourable environmental conditions
- resistant to heat, cold, chemicals and radiation
- wait it out until environment changes to what it needs to survive and grow
How to destroy endospores?
sterilization (steam, under pressure, chemical sterilants)
Bacterial cell wall function?
- provides structure
- maintains shape
- protects from pressure
- plateform for flagella and fimbriae
- contributes to adherence
- target for antibiotics (adhere to the cell wall)
Gram stain function?
-purple stain on bacteria to determine whether the bacteria is gram negative or gram positive
Gram positive?
Gram negative?
G+= purple, retain the purple stain G-= red, does not retain the purple stain
Why does gram positive retain the purple stain and why does gram negative bacterium not?
gram positive (purple) bacterium have a thick, non porous cell wall gram negative (red) bacterium have a thin cell wall with an outer membrane
What does a gram negative bacterium have gram positive bacterium do not have?
outer cell membrane
What does gram negative bacterium have in their cell membrane?
Lipid A (endotoxin)
Human body and lipid A?
all immune systems recognize lipid A and causes inflammation, fever, vasodilation and can induce shock and blood clot formation
Most hospital acquired infections are from?
gram negative bacterium
Where is there a large number of gram negative bacterium? gram positive bacterium?
- hospitals
- communities
Safranin?
pink stain, gram negative bacterium will retain this giving it a red appearance
What is the effect of human error when mishandling a gram-positive bacterium species?
looses cell wall integrity, stains as “gram negative” (red)
Can some non-bacterial organisms with thick cell walls stain gram-positive?
yes
Clinically, why is gram staining important
important for classifying bacterial pathogens, which is critical for choosing a treatment method
What does a large amount of neutrophils mean?
bacterial infection is present
Acid fast stain?
differential bacterial stain that distinguishes b/w organisms with a waxy cell wall (retains the stain)
When to use acid fast stain? Example?
- when mycobacterial infections are suspected
- TB (waxy cell wall)
Bacterial classification based on oxygen requirements?
- used to figure out last name of organism
- oxygen is a free radical and very dangerous to bacterial species, make it hard to survive
3 Enzymes that bacteria uses to detoxify reactive oxygen products
- catalase
- peroxidase
- superoxidase dismutase
Bacterial obligate aerobes organisms?
- need oxygen to survive
- have all 3 enzymes in order to survive
Microaerophiles?
-species that tolerate low amounts of oxygen
Facultative anaerobes?
-prefer to grow in oxygen but can produce in environments that are oxygen deprived
Fewer enzymes produced=?
less likely that those species tolerate oxygen
Obligate anaerobes?
- can’t tolerate oxygen
- lack of enzymes
- susceptible to damage as they don’t produce enzymes
Bacteria reproduction; Asexual
- Exponential phase?
- Stationary phase?
- Death phase?
- Lag phase?
- binary fission
- EP= number of cells grow exponentially as nutrients are available
- SP= nutrients deplete, toxic waste accumulates which slows growth rate
- DP= no new sources of nutrients causes bacteria to die
- LP= new environment, bacteria have to adapt and get used to environment prior to expanding
How long does it take to identify a specimen based on growth rate?
48hrs hours
What does bacteria sexual reproduction require?
conjugation pili
Obligate intracellular bacteria?
- need a host to survive
- cant make their own energy
- grow in cell cultures
Facultative intracellular bacteria?
- avaoid phagocytosis
- reproduce and grow within immune cells
- shield from antibodies and immune defences
- mechanisms to defend against lysosomal enzymes produced by phagocytic cells
- takes longer for body to identify infection
Greater risk for infection with obligate or facultative intracellular bacteria?
- facultative, b/c it can survive phagocytosis and avoid antibodies
- greater risk for infection
Viruses; obligate intracellular pathogen?
- can’t replicate independently
- need host cells to replicate
- uses host cells energy, organelles, enzymes to replicate
Viruses; acellular pathogens?
- lack a cell membrane
- only have a few organelles
- DNA and RNA housed in a capsid
- capsid has recognition sites that bind to receptors on host and it helps to protect the DNA and RNA
Virus “envelopes”
- some acellular viruses have this
- allows for entry into a host cell
- replaces cellular membrane proteins with virus derived proteins making entry into host cell easier
Capsid?
- protein coat protecting DNA and RNA
- has recognition sites on it to help bind to host cells
Are viruses acellular or cellular?
acellular, b/c they are not “alive”
What 4 characteristics of viruses are used to classify them?
What are more detailed characteristics of viruses used to classify them?
- vision structure
- mechanism of replication
- nature of genome
- molecular techniques
- cytopathic effect on host cells
- nature of disease
- serological reactions
- AA sequences of proteins, nucleic acid sequences
Viral replication
- can’t reproduce by itself
- lack enzymes for replication
- don’t have ribosomes for protein synthesis
- when host cell is controlled by viral genome, viral genetic material is replicated and proteins are translated
5 steps of viral replication: 1. Attachment
- interaction with host cell receptor
5 steps of viral replication: 2. Entry (3 ways)
- direct penetration
- membrane fusion
- endocytosis
What happens to viruses capsule after penetration?
Do you need capsule intact for entry?
- sheds/ “uncaring”
- need this to allow for replication
- yes, you need capsule intact for entry
5 steps of viral replication: 3. Synthesis (DNA and RNA)
- DNA synthesis occurs in nucleus
RNA synthesis occurs in cytoplasm
5 steps of viral replication: 4. Assembly
- once synthesized, they are assembles into virions
Virion?
- entire virus particle
5 steps of viral replication: 5. Release from host cell (budding and lysis/exocytosis)
budding= visions are extruded through cell wall membranes, forming viral envelope exocytosis= vision is extruded without acquiring an envelope lysis= virus released by host cell, killing the host cell
Aborted viral infection?
- little or no detectable effect
- can be nothing if body does not recognize it or you are not exposed enough
Persistent viral infection?
- alterations of antigenic specificity of cell surface due to the presence of viral glycoproteins
- host cell is intact so you get gradual, prolonged release of viral particles
- HEP B (chronic infections)
Latent viral infection?
- viral genome is persistent in cell
- can be reactivated at anytime
Transformation viral infection?
- viral genome integration in host cell may disrupt host cell growth, replication and metabolism
- result is tumour production
Viral infection; host cell death?
- rapid lysis of host cells and release of progeny
- feel “sick”
Examples of persistent, latent and transformation viral infections?
- Hep B
- Cold sores
- HPV, cervical cancer
Fungi
- grow as single cell or multicellular
- most are not pathogenic (saprophytic)
- identified by direct examination or in lab cultures
Where do most fungi get their food from (saprophytic)?
- dead organic matter
Example of a single celled fungi?
- yeast
Example of a multi celled fungi?
- mold
Dimorphic fungi?
-can grow in both single celled or multicellular forms
Hyphae?
-gives mold its fuzzy appearance
How do yeasts reproduce?
budding
How do molds and dimorphic fungi reproduce?
- form asexual spores
- spores germinate to make new organisms once an ideal environment is found
Cell wall; fungus vs bacteria
- fungus cell wall= made of chitin
- bacteria cell wall= made of peptidoglycan
Cell membrane; fungus vs humans
- fungus= ergosterol
- humans= cholesterol
Difference b/w ergosterol and cholesterol and anti fungal agents?
- difficult to find the difference, thus anti fungal agents can cause many adverse affects
Mycoses?
- chronic fungal infections
- grow slowly
- classified into 5 categories
Mycoses; Superficial infections
- outermost layer of skin, hair, nails
- treat topically
Mycoses; Cutaneous infections
- deeper, keritonized skin layers
- itchy, scaling skin, inflamed
- topical therapy may not work
Is cutaneous fungal infection transmissible?
- yes
Examples of cutaneous fungal infections?
- ringworm, tinea
Mycoses; Subcutaneous infections
- dermal layer, subcutaneous layer, muscle layer as well
- sessions of the skin
- difficult to treat, excision or amputation is often needed
Mycoses; Systemic infections
- primary infection
- start in lungs then travel into blood stream
- associated with inhaled spores
- found in feces of birds and bats
Mycoses; Opportunistic infections
- in people with impaired host defences
- AIDS, DM, cancer, immunosuppressive therapies
Parasites?
- develop in poor sanitation country’s
- most common in tropical country’s (food and water)
- 70% of people in the world are infected with a parasite
- long chronic infections, can be serious
Protozoa?
- eukaryotic
- unicellular
- doesn’t have a cell wall
- exist in a feeding state
- form spores that protect from harsh environments
Protozoan cyst?
- thick capsule, low metabolic rate
- infective form
- protects from harsh environments
Trophozoite?
- active form
- can replicate and grow
Site of infection for protozoans?
- GI
- UG tracts
- Blood
- Tissues
Mode of locomotion for protozoans? (amoebas, flagellates, ciliates, sporozoa)
Amoebas- extend cytoplasmic projections outward from body to move
Flagellates- whip-like projections rotate and propel
Ciliates- hair-like projections on cell surface move in unison to move the cell
Sporozoa- non-motile, adult males can have a flagella
Protozoan reproduction
- asexual (binary fission)
- some is by sexual reproduction
How do parasites gain access to human hosts
- via ingestion or penetration (bite), attachment, replication and host damage
