Week 5 Flashcards
Bacteria Cell Characteristics
- Prokaryotic cells
- No true nucleus
Capsule (Bacteria)
- Additional outer covering protecting cell when engulfed by other organisms
- Assists in maintaining moisture
- Helps cell adhere to surfaces and nutrients
Cell Wall (Bacteria)
- Outer covering that protects cell
- Gives shape
- Controls permeability
- Prevents dehydration
- Provides surface platform for flagella & pilus
Plama Membrane (Bacteria)
- Thin wall separating cell wall from cytoplasm
- Semi permeable membrane
- Controls inflow & outflow of metabolites
Cytoplasm (Bacteria)
- Gel like substance
- Composed of water, enzymes, salt, cell components
- Contains nucleus & ribosomes
Ribosomes (Bacteria)
Protein production
Nucleoid (Bacteria)
Contains single bacterial DNA molecule
Pilus (Bacteria)
- Hair like structures on cell surface
- Help to attach to other bacterial cells
Flagella (Bacteria)
- Long protrusions
- Aid in cellular locomotion
Bacterial Morphology
- Autonomously replicating
- Unicellular organisms
- Lack organized nucleus
- Contain DNA & RNA
Coccus
- Oval/sphere
- Diplococcus - pair
- Streptococcus - line of 4
- Tetrad - square
- Cuboidal packets - 8
- Staphylococcus - 14
Rod
- Single
- Diplobacillus - pair
- Streptobacillus - chains
- Cocco-bacillus - oval
Spiral
- Vibrio - curved/column shaped rod
- Spirochete - thin flexible spiral
- Spiral - thick rigid spiral
Bacteria Replication Steps
- Prokaryotic chromosome
- Duplication of chromosome
- Continued growth of cell
- Division into 2 identical cells
No genetic variations
Bacteria Recombination
- Genetic variation
- Genes from 1 prokaryotic incorporated into another
- Bacterial reproduction
- Transformation, transduction, conjugation
Bacteria Transformation
Uptake of short fragments of naked DNA by naturally transformable bacteria
Bacteria Transduction
Transfer of DNA from 1 bacterium into another via bacteriophages
Bacteria Conjugation
Transfer of DNA material via sexual pilus & requires cell-to-cell contact
Gram Positive Bacteria Components
- Peptidoglycan - thick
- Periplasmic space
- Plasma membrane
- Cytoplasm
Gram Negative Bacteria Components
- Lipopolysaccharide outer membrane
- Periplasmic space
- Peptidoglycan - thin
- Plasma membrane
- Cytoplasm
Obligate Aerobes
Cannot survive without oxygen
Facultative Aerobes
- Prefers high oxygen environments
- Can still survive in low oxygen environments
Microaerophilic Bacteria
Can only survive in environments with very little oxygen
Obligate Anaerobes
Cannot survive in presence of oxygen
Virus Characteristics
- Obligate intracellular organisms
- Require living cell for replication
- No energy
- Float around until contact with an appropriate cell
- DNA or RNA
- Unable to grow or undergo binary fission
Virus Replication
- Take control of host genetic machinery
- Need enzymes from host to build replicas
Virus Composition
Composed of capsid & genetic material
Virus Classification
- Type of viral genome
- Type of symmetry of virus capsid
- Presence/absence of lipid envelope
- Size
Virus Capsid
- Protein surrounds virus
- Composed of finite number of protein subunits - capsomeres
- Close to nucleic acid
Viral Genome Types
- Single stranded DNA/RNA
- Double stranded DNA/RNA
Lipid Envelope
- Outer lipid bilayer
- Some viruses have
- Called naked if no envelope
Replication Cycle of Viruses
- Absorption & penetration
- Uncoating of virus
- Genome replication
- Release of virions from the host cell
Absorption (Virus)
- Virus attaches to specific receptor site on host cell membrane
- Attachement facilitated by proteins (capsid) or glycoproteins in viral envelope
- Specificity of reaction determines host and cells within host that can be effected
Penetration (Virus)
- Nucleic acid enters cell naked, leaving capsid outside
- Plant & animal viruses enter through endocytosis - cell membrane engulfs virus
- Viral envelope can fuse directly with cell membrane
Uncoating
- Viral capsid is degraded
- Nucleic acid is released
- Available for replication & transcription
DNA Virus Replication
- Host cell proteins & enzymes used to make additional DNA
- Transcribed to messenger RNA
- Used to direct protein synthesis
RNA Virus Replication
- Use RNA core as a template for synthesis
- Viral messenger RNA directs host cells to synthesis viral enzymes & capsid proteins
Release of New Virions
Able to infect adjacent cells & repeat replication cycle
Host Cell Outcome (Virus Infected)
- Death
- Transformation
- Latent infection
- Chronic slow infection
Cytopathic Effects
- Viral replication produces dramatic biochemical & structural changes in host cell
- May cause cell damage, death
Host Cell Transformation
- Infection activates/produces oncogenes - cause cancer
- Uncontrolled/uninhibited cell growth
Host Cell Latent Infection
- Virus survives in sleeping state
- Various factors can reactivate virus
- Immunity to virus may decline in this time
- Common with herpes, chickenpox
Host Cell Chronic Slow Infection
- Virus causes infection after many years/decades
- Hep C
- Lack of symptoms
Fungi Characteristics
- Free living
- Eucaryotic organisms
- Some are members of human microflora
- Few fungi capable of causing disease in humans
- Immune systems & competition with flora for nutrients keep fungi in check
- Sexual or asexual reproduction capabilities
Fungal Overgrowth
- Sets stage for infection opportunity
- Caused by disfunction of immune system or nutrient competition
Yeast
- Single cell organisms
- Reproduce via budding process - separate from parent cell, identical daughter cells
Mold
Long hallow branching filaments - hyphae
Dimorphic Fungi
Produce as yeast at one temperature and mold at another
Yeast & Mold Wall
- Produce rigid cell wall layer
- Chemically unrelated to peptidoglycan of bacteria
- No susceptible to effects of Penicillin (antibiotics)
Superficial Yeast Infection
- Wet work
- Pregnancy, oral contraceptives
- Diabetes mellitus
- Broad spectrum antibiotics
- HIV infection, CD4<500
Deep Yeast Infection
- Cytotoxic chemotherapy, corticosteroids
- Indwelling venous catheters
- Broad spectrum antibiotics
- Intravenous drug abuse - portal of entry, infections
- HIV infection, CD4<200
Immunocompromised
Candida Albicans
- Most common yeast causing infection
- Normal flora of oropharynx, vagina, bowel, skin
- Causes acute & chronic superficial infections of skin, nails, mucous membranes
- Severe systemic infections in immunocompromised patients
Protozoa
- Passed through sexual contact, contaminated food/water, arthropod vector
- Fusion of 2 cells, exchange DNA, separate again
DNA replication, division into 2 cells - asexually
Helminths
- Collection of worm like parasites
- Nematodes, cestodes (tape worms), trematodes
- Macroscopic - visible to naked eye
- Sexual reproduce within host
- Ingestion of ova, penetration of infectious larva through skin
Arthropods
- Vectors of infectious diseases - tick, mosquitos, biting flees, ectoparasites
- Carry organism & inject into humans while feeding
Ectoparasites
- Infest external body surfaces
- Cause localized tissue damage/inflammation
- Bite/burying
- Contact with immature/mature pods or eggs causes transmission
Prions
- Transmissible
- Create spongy pathological changes in brain
- Results in encephalopathy causing brain damage
- Fatal neurodegenerative disorders of human & animal
- Mad cow disease most common
Prion Disease Characteristics
- Long incubation time - months to years
- Gradual increase in severity leading to death within months of onset
- No host immune response
- Non-inflammatory processes in the brain
- Inherited
- Infectious - agent consists of mainly prion proteins
Neuropathological Findings with Prions
- Macroscopic exam often normal
- Microscopic changes cause neuronal loss & amyloid plaques with prion protein accumulation (PRP)
Prion Transmission
- Oral
- Inoculation
Prion Disease Clinical Features
- Rapidly progressive dementia
- Psychiatric symptoms
- Cerebellar symptoms - ataxia (clumsy movements)
- Involuntary movements - myoclonic jerks
- Death
