Bio 11 microbiology

Dmitri Iwanowski : Found that juice in tobacco leaves caused infections in other plants

• Martinus Beijerinck : Realized tiny particles in juice that caused infection
• -named particle "virus" which means infection

-Non-cellular particle made of genetic material and protein that can invade living cells.

• 1. Core of nucleic acids (DNA, RNA)
• 2. protein coat (capsid) that surrounds nucleic acid
• *some have more complex structures.

-Virus that infects bacteria

• a) rods
• b) cubes
• c) Helix

• between 10-300 nm. (nano-metres)
• * must use scanning electron microscope or transmission electron microscope

-Can only infect a specific host

ex: HIV specific to humans

Viruses are obligate intercellular parasites.

(must feed off of host cell)

• -genetic material
• -replicate (reproduce)
• -evolve (mutate)

• -non-cellular
• -requires host
• -doesn't use energy

-Causes infections by injecting DNA into host

• 1. infection
• 2. growth
• 3. replication
• 4. Lysis

• 1. Lytic infection
• 2. Lysogenic infection

• - Growth phase of Lysogenic infection:
• *Viral DNA is incorporated into host DNA (prophage)
• -remains dormant for a long period of time
• -cell replicates viral DNA by binary fission

• -virus attaches to host cell using tail fibres
• -inserts DNA into cell

• -Host's RNA polymerase (enzyme) make MRNA from viral DNA
• -MRNA takes over host cell

-virus uses host's machinery (ribosomes, golgi apparatus etc) to construct :

• 1) DNA
• 2) Capsids (protein)

• -Host cell becomes filled with new viruses....then bursts (lyse)
• - Spreads viruses to neighbouring cells.

25 mins

• -evolved after first living cell (because must live inside host)
• - evolved from genetic material of living cells, mutated and evolved

• - genetic research (cancer)
• - Gene therapy
• - genetic engineering (injecting specific DNA)

1. Disease (HIV, Influenza) viruses are pathogens

• 2. Cancer
• - during infection when DNA is inserted, gene may become an oncogene causing cancer
• -cell undergoes uncontrolled divisions forming tumor (benign or malignant)

• 1. good hygiene
• 2. Healthy lifestyle (diet, exercise)

1. Non-specific defences

2. Specific defenses

• - skin (oil and sweat provide acidic environment)
• -cilia/mucus (traps virus)
• -secretions (destroys virus)
• -phagocytes (engulf bact/viruses -> leads to fever)
• -interferon (infected cell produces protein that interferes with virus & slows it)

• 1. Antibodies/immune response
• 2. Immunity
• 3. Cell mediated immunity

Pathogen specific antibodies are produced that bind to and inactivate virus (antigen)

• i) active : injection of vaccine that causes body to produce antibodies
• ii) passive: injection of antibodies produced in another animal

Killer T-cells attack antigen-bearing cells and destroy them

Prokaryotic cells do not have a nucleus, or membrane.

• -all monerans are prokaryotic
• - All called bacteria
• - Divided into 4 phyla

• -eubacteria
• -cyanobacteria
• - archaebacteria
• -prochlorobacteria

• - surrounded by cell wall composed of complex carbs
• - within cell wall is membrane
• -some have flagella
• - photosynthetic

• -photosynthetic
• -contain chlorophyll
• -found on water+land
• -first to recolonize after nat. disaster

-live in extremely harsh environments

• -contain chlorophyll A and B as principal pigments
• - similar to chloroplasts of plants
• -only 2 species discovered

• -rod
• -sphere
• -spiral

• -rod
• -produce endospores (dormant, waiting for ideal conditions)
• -gram positive

• -Spherical
• -grow in colonies of two cells
• -long chains
• - clumps or clusters

• -spiral
• - possess bipolar tufts of flagella

• - propelled by flagella
• - lash, snake, spiral forward
• - glide on slimelike material
• - sessile (no movement)

• Autotrophs
• heterotrophs

a) Phototrophic autotrophs : obtain energy from sunlight

b) chemotrophic autotrophs: live in harsh environments, obtain energy from inorganic molecules

a) chemotrophic heterotrophs: Break down organic molecules, most bacteria and animals

b) phototrophic heterotrophs : Photosynthetic but also need organic compounds

using gram staining

crystal violet (purple)

safranine (red)

• -gram positive
• eg. clostridium tetanus

• -gram-negative bacteria
• *more toxic, more resistant to antibiotics

eg: e coli.