Bacteria vs. Viruses
Kerrigan Krueger
Bacteria
- Gram staining: used to identify unknown bacteria
- Pink color= negative, purple color= positive
- Shapes
- Cocci (spheres): Micrococcus luteus,
- Bacilli (rods): Bacillus subtilis, serratia marcescens
- Cocobacilli (ovals): Staphylococcus epidermidis
- Vibrio (curved rods): Escherichia coli
- Spirillia (rigid helices)
- Spirochetes (flexible helice)
Bacteria Growth and Nutrition
- Environmental factors
- Solutes
- Temperature (incubator)
- Radiation: x-rays, ultraviolet
- pH
- Oxygen concentration
- Nutrients (macro and micro)
- Chemical and physical factors
- Chemical: detergents, solvents, alcohols
- In lab: Hydrogen peroxide, bleach, lysol, isopropyl alcohol,
- Kills/inhibits bacterial growth
- Physical: Heat, dry heat, refrigeration
- In lab: Bunsen burner
Comparing and Contrasting
Bacterial growth curve
- Lag phase (slight increase in cells, synthesize ribosomes)
- Log phase (max rate of reproduction, population growth)
- Stationary phase (energy stores deplete, number of cells being produced and number dying are about equal)
- Death phase (number of cells dying exceeds number being produced)
Virus
Viruses
- Obligate intracellular parasites, sub-microscopic entity consisting of a single nucleic acid surrounded by a protein coat and capable of replication only within the living cells of bacteria, animals, or plants
- Structures and resistance:
- Naked capsid virus: DNA/RNA +capsid protein= Nucleocapsid
- Resistant to drying, heat, detergents, and acid
- Enveloped virus: Nucleocapsid + lipid membrane and glycoproteins
- Sensitive to drying, heat, detergents, and acid
- Virus replication
- Attachment and entry: hijacks healthy receptors for infection process
- Uncoating: virion breaks open and releases virus genome nucleic acid
- Transcription: virus mRNA provided using cellular enzymes or virus encoded enzymes)
- Genome replication: takes place in cytoplasm or nucleus of infected cells
- Translation: uses host cell ribosomes, enzymes, etc. and proteins are synthesized
- Virion assembly: new proteins and new genomic nucleic acid produce new virus particles
- Virion releases: virus buds through cell membrane and pick up envelope or the virus causes lysis of cell, and the host cell dies, releasing progeny virus
Virus transmission and infection
- Virus transmission
- Respiratory: SARS
- Fecal/oral
- Blood-borne
- Sexual: HIV
- Animal or insect vectors: Avian influenza
- Virus infection
- Development of viraemia (virus in blood) spreads throughout tissues
- Short incubation time, maximal virus production right after
- Symptoms appear right after peak
- Immune response generated, virus usually killed after 1 to 2 weeks
Compare and Contrast
- Bacteria: living, reproduces by dividing, exist everywhere
- Virus: non-living, require living hosts to multiply or they won't survive
- Bacterial infection: localized to specific parts of the body
- Viral infection: involve different parts of the body or more than one body system
- Bacteria: more complex structure than virus, larger than virus
- Both: contain DNA/RNA and enzymes, both cause illnesses
- Bacteria: has a cell wall
- Virus: has a protein coat
- Bacteria: one chromosome
- Virus: central core of DNA or RNA