Bacteria & Viruses Chapter 21

Bacteria vs. Viruses Bacteria Viruses Fully functioning cellular organisms Lack a nucleus Reproduce asexually - binary fission Viruses Obligate intracellular parsites Reproduce inside bacteria, plant cells, animal cells capsid

Bacteria vs. Viruses Virus Bacteria

Bacteria – Gram Stains Gram-positive retain stain and appear purple Have thicker layer in cell wall. Gram-negative do not retain stain and take second pink stain instead.

Gram Stains Phylum Shape Motility Metabolism Gram reacion Cyanobacteria Bacilli, Cocci Gliding, some non-motile Aerobic, photosynthetic autotrophic Gram-negative Spirochetes Spirals Corkscrew Aerobic, and anaerobic; heterotrophic Gram-Pos Bacilli, cocci Flagella; some non-motile Aer/anaer.; heterotrophic, photosynthetic Mostly gram-positive Proteobacteria Bacilli, cocci, spiral Aer/anaer.; heterotrophic, photosynthetic autotrophic

Bacteria: Key Characteristics Single-celled Prokaryotic Oldest living organisms Most common type of prokaryote

Bacteria Classification Nutrition Reactivity to oxygen Archaebacteria vs Eubacteria

Bacteria Classification - Nutrition Autotrophs Photoautotrophs: photosynthetic autotrophs produce energy from light (blue-green algae) Chemoautotrophs: produce energy from inorganic substances Heterotrophs Bacteria that feed off of hosts

More Bactiera Nutrition - Heterotrophic Prokaryotes Most free-living bacteria are chemoheterotrophs that take in pre-formed organic nutrients As aerobic sapotrophs, there is probably no natural organic molecule that cannot be broken downby some prokaryotic species

Bacteria Classification: Reactivity to Oxygen Obligate Aerobes: requires oxygen for respiration & growth Obligate Anaerobes: oxygen serves as a poison – must avoid! Facultative Anaerobes: can use oxygen if available but can also survive without it

Bacteria Classification: Archaebacteria vs Eubacteria Live in extreme environments Extreme Halophiles: “salt lovers” live in environments w/ high salt concentration Methanogens: bacteria that produce methane as a waste product Thermoacidophiles: bacteria that love hot acidic environments

Types of Archaea Methanogens: live under anaerobic environments where they produce methane (eg marshes) Halophiles: require high salt concentrations (eg Great Salt Lake) Thermoacidophiles: live under hot, acidic environments (eg geysers)

Bacteria Classification: Archaebacteria vs Eubacteria Moderate environments Categorized according to shape, motility, cell-wall composition, pathogenic nature Proteobacteria Gram-positive bacteria Gram-negative bacteria Cyanobacteria Spirochetes Chlamydias Chemosynthetic bacteria Nitrogen-fixing bacteria ****BE ABLE TO DESCRIBE EACH OF THE ABOVE BACTERIA!!***

Structure of Prokaryotes Outer wall strengthened by peptidoglycon (molecule containing amino disacharride & peptide fragments Some move by use of flagella Adhere to surfaces by means of fimbriae

Reproduction in Prokaryotes Reproduce asexually through binary fission Mutations are chief means of genetic variation

Kingdom Archaebacteria First discovered in extreme environments Methanogens: Harvest energy by converting H2 and CO2 into methane gas Anaerobic, live in intestinal tracts Extreme halophiles: Salt loving live in Great Salt Lake, and Dead sea. Thermoacidophiles: Live in acid environments and high temps. Hot Springs, volcanic vents

Kingdom Eubacteria Spirillum – spiral-shaped Bacilli – rod-shaped Cocci – round or spherical

Viruses Noncellular parasitic agent consisting of an outer capsid and an inner core of nucleic acid Have DNA or RNA genome, but can only reproduce by using the metabolic machinery of a host cell

Viral Structure Shape: varies from theadlike to polyhedral All viruses have same basic anatomy: outer capsid with protein subunits & inner core of nucleic acid

Categorizing Viruses Type of nucleic acid Size and shape DNA or RNA (not both) Single-stranded or double-stranded Size and shape Presence or absence of an outer envelope

Viruses: Parasitic Nature Obligate intracellular parasites Host Specific: infect a variety of cells Viruses can mutate Viruses evolve & reproduce, but they are not obligate intracellular parasites – they only grow inside their specific host cells

Lytic Cycle & Lysogenic Cycle

Lytic Cycle 5 Stages 1. Attachment: capsid combines with receptor 2. Penetration: viral DNA enters host 3. Biosynthesis: viral components are synthesized 4. Maturation: assembly of viral components 5. Release: new viruses leave host cell

Lysogenic Cycle Viral DNA integrated into host DNA The phage becomes a prophage that’s integrated into the host genome Bacteriophage (phage): viruses that parasitize bacteria Phage may reenter lytic cycle; reproduction and release of the virus then occur

Viroids and Prions Viroids- naked strands of RNA, directs the cell to make more viroids Prions- (proteinaceous infectious particles), newly discovered disease agents that differ from viruses and bacteria