microbiology (viruses + origin of life)

when was earth approximately formed?

4.6 bya

when was the first fossil evidence for life discovered?

3.5bya

chemical evolution 1st stage

1. the abiotic synthesis and accumulation of small organic molecules, such as amino acids and nitrogenous bases

chemical evolution 2nd stage

2. the joining of these molecules into macromolecule, such as proteins and nucleic acids

chemical evolution 3rd stage

3. the packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings

chemical evolution 4th stage

4. the origin of self replicating molecules that eventually made inheritance possible

synthesis of organic compounds on early earth

early atmosphere was low in oxygen but water vapour, nitrogen (and oxides), carbon dioxide, methane, ammonia, and hydrogen were abundant.

miller urey experiment

an experiment simulating early earth conditions

• water mixture in sea flask was heated, vapour entered atmosphere flask

• atmosphere contained a mixture of hydrogen gas, methane, ammonia, water vapour

• sparks were discharged to mimic lighning

• condenser cooled the atmosphere, raining water, any dissolved molecules down the sea flask

• as material continued to cycle, samples were collected for analysis

abiotic synthesis of macromolecules

once monomers were formed on early earth, they had to be joined together to make polymers. polymers of amino acids have been formed when solutions of amino acids are dropped onto hot sand, clay, rock

protocells

living things must reproduce, metabolize, homeostasis,

• evolved through vesicles —> membrane bound droplets that can form spontaneously when lipids are put into water

rna world hypothesis

scientists believe that rna was the first nucleic acid

• can act like a catalyst, speeding up chemical reactions

• can direct its own replication

• has a genotype and and a phenotype —> susceptible to natural selection

• can direct synthesis of DNA

what makes up a virus?

a virus consists of a nucleic acid surrounded by a protein coat, smaller than bacteria and animal cells and ribosomes

virus

an infectious particle consisting of little more than genes and protein coat

viral genomes

• dna or rna

• single stranded or double stranded

• linear or circular

capsid

protein shell enclosing the viral genome (consists of individual proteins called capsomeres)

viral envelopes

membranous envelopes surrounding the capsid (derived from host cell)

• contains host cell phospholipids and proteins in addition to viral proteins and glycoproteins

where can viruses replicate?

host cells

• viruses can reproduce within a host cell: obligate intracellular parasites

• each virus can only infect a limited number of host species: host range

• they identify the host cell using a lock key fit between viral surface proteins and receptors on cell exteriors

viral life cycle

1. virus enters the cell and is uncoated, releasing viral dna and capsid proteins

2. host enzymes replicate the viral genome

3. meanwhile host enzymes transcribe the viral genome into viral mrna, which host ribosomes use to make more capsid proteins

4. viral genomes and capsid proteins self-assemble into new virus particles which exit the cell

lytic cycle of virus

• immediate replication, hijacking the host cell to produce new viruses

• cell bursts and dies

lysogenic cycle of virus

• viral genome goes into the host genome

• replicates with the host cell instead of destroying it immediately

bacterial defenses against phage

1. natural selection

2. restriction enzymes: bacterial enzymes that cut up foreign DNA

3. crispr-cas system

how do viruses cause damage?

• damage/kill cells by releasing enyzmes from lysosomes

• cause infected cells to produce toxins/some are toxic

how can we fight viruses?

• vaccines: harmless variant or derivative of a pathogen that simulates the immune system

• antiviral drugs: interfere with nucleic acid replication

herd immunity

when a high percentage of a population is vaccinated

prions

infectious proteins

• act slowly, can incubate for 10 years

• indestructible, causes functioning proteins to turn into prions

epidemiological triangle

public health approach to fighting disease

what is the organization for prokaryotes

• unicellular

• some organize colonies

what are the ways colonies can be organized?

• straph - clusters

• strep - chains

• diplo - in pairs

shapes of prokaryotes

• cocci (coccus)

• bacilli (bacillus; rods)

• spirochetes and spirilla (helical)

cell wall

• protects and maintains shape

• prevents cell from bursting from osmosis

• bacteria: composed of peptidoglycan

• archaea: lack peptidoglycan

capsule

• sticky protective layer outside the cell wall

• enable bacteria to adhere to their substrate

• glue cells of colonies

pili

appendages that pull two cells together prior to conjugation

internal organization

• prokaryotic cells lack compartmentalization

• some prokaryotic cells have specialized membranes that perform metabolism

• circular dna that is found in the nucleoid region

plasmid

small circular pieces of dna that are self replicating and contain contingency genes (not necessary for day-day) antibiotic resistance, ability to digest lactose

ribosomes

protein synthesis, smaller than eukaryotic ribosomes

transformation

prokaryotic cells are able to take up foreign dna

transduction

occurs when bacteriophages carry prokaryotic genes from one bacterium to another

conjugation

dna is transferred between two prokaryotic cells; this exchange is only one way

bacteria - prokaryotic diversity

• most prokaryotes

• classified as gram positive or gram negative

archaea - prokaryotic diversity

• share traits with both bacteria and eukaryotes

• live in extreme environments

what are the three main types of archaea?

1. extreme thermophiles

2. extreme halophiles

3. methanogens

extreme thermophiles

live in very hot environments

extreme halophiles

live in very salty environments

methanogens

anaerobic, release methane as a waste product of their metabolism

• live in swamps and marshes; guts of cows

mutualistic bacteria

microbiome

what are the types of pathogenic bacteria?

• exotoxins

• endotoxins

exotoxins

proteins secreted by prokaryotes that cause illness; bacteria can cause disease without being present

endotoxins

components of the outer membranes of gram-negative bacteria that cause illness

bioremediation

sewage treatment plants, oil spills

food - research and tech

cheese, yogurt, beer, wine, pepperoni, sauerkraut, soy sauce

genetic engineering

production of insulin, crispr

metabolic cooperation

prokaryotic cells work together

biofilm

community of microbial cells that adheres to a surface and is encased within a self-produced, protective matrix