BIO UNIT 3 Flashcards
viruses
Obligate intracellular Parasites
virion
single virus particle
general size viruses
very small, 20-250nm
Most viruses can only be seen with…
electron microscopy
DNA and poxviruses can be observed with…
light microscopy
Viruses Evolution hypotheses (3)
- Regressive hypothesis – from free living cells
- Progressive hypothesis – RNA or DNA that escaped host cells
- Self-replicating hypothesis
Non-cellular – Biological entities with no cellular structure
- Nucleic acid core
- Outer protein coating = capsid
- Phospholipid membrane = envelope – not always present
Complexity not associated with host
bacteriophage
shaped
- Helical – many plant viruses
- Icosahedral – Roughly sphere – Poliovirus, herpesvirus
- Enveloped – Animal viruses - HIV
- Head-and-tail – Infect bacteria
Virus Core
contains the genome
RNA viruses
only RNA
* Must encode own enzymes to replicate RNA to RNA or RNA to DNA (retroviruses)
* More prone to change –RNA polymerases make more errors
DNA viruses
Viral DNA “tricks” host cell into replicating its genome
Virus Classification: Structure
Enveloped or not, capsid structure, RNA or DNA
Baltimore Classification
Morphology, genetics, how mRNA is produced
Permissive
Host cells where virus replicates, Must have receptor *permission is first step!!!
Attachment
needs specific receptor, this is second step!
Entry
endocytosis (plant and animal), membrane fusing, third step!
Replication and Assembly
Viral mRNA, reverse transcription (HIV)
Egress
release of new virions
* Lysis & apoptosis * Budding
DISEASE: Acute
symptoms get worse for a short period before elimination from body
DISEASE: Chronic
long term
(could be intermittent or asymptomatic)
DISEASE: Oncogenic Viruses
ability to cause cancer
Vaccine
live, killed, molecular subunits of viruses
* Live strains and back mutation
*High mutation rate of viruses
Anti-viral Drugs
- Manage symptoms – not curative
- May control viral replication rates (HIV drugs)
Non-Virus Disease Organisms: Prions
– Cause TSE’s
* Cause misfolding in normal proteins
* Usually fast acting and always fatal
Human Prions
Kuru, Krutzfeldt-Jakob Disease
Animal Prions
Bovine Spongiform Encephalopathy, Chronic Wasting Disease, Scrapie
First organisms on Earth
Subjected to harsh conditions
Microbial mats – 3.5 BYA
Multilayer sheet of prokaryotes
Stromatolite
sedimentary structure formed as minerals are precipitated out of water by prokaryotes
Extremophiles
Lovers of extremes (Early Earth was anoxic, hot, subject to solar radiation and volcanic eruptions)
Phototrophs within… cyanobacteria…
1 billion years of earth, 1 Billion years later (Oxygenation)
Koch and Petri
- Culture method still used today
- Koch’s postulates – infected samples, healthy samples, re-infection
Non-culturable Prokaryotes
- 99% of prokaryotes – unknown conditions – DNA, PCR, NGS
- Viable-but-non-culturable state – previously cultured – stressed
- Resuscitation – goes back to normal state with improved conditions
Biofilms
- Microbial community held together by a gummy-like texture
- Protects prokaryotes from the environment
Prokaryote Structure
- Single-celled with no membrane-bound organelles
- Usually single chromosome
- Circular DNA in nucleoid
Cell wall
– protective layer
– determines shape
Capsule
outside of cell wall – protection – pathogens…
Flagella
locomotion
Pili (pilus singular)
attachment to surfaces (HGT)
Plasmids
(extra-chromosomal DNA)
Major bacterial Phyla
** Proteobacteria (largest lineage)
** Chlamydial (smallest lineage) – obligate parasites
* Spirochaetes
* Cyanobacteria
* Gram-positive bacteria
Archaea
- Euryarchaeota
*Crenarchaeota - Nanoarcheota
- Korarchaeota
membrane
- Thin lipid bilayer plasma membrane
- Selectively permeable
- Archaea – replace fatty acids (link glycerol) with isoprene
- Some lipid monolayers
Cell walls
outside membrane – withstands high osmotic pressure
***Gram pos. bacteria have a THICK peptidoglycan layer
Archaea four cell wall types
*Pseudopeptidoglycan, polysaccharide, glycoprotein, pure protein
Reproduction: Rates vary
minutes to longer (mutation and resistance)
Reproduction: Asexual
usually binary fission = clones
* No genetic recombination
Gene transfer in Prokaryotes
Transformation
Transduction
Conjugation
Micronutrients
required in small amounts ex. iron
Macronutrients
required in large amounts (CHONPS)
* Components of proteins, carbohydrates, lipids…
Phototrophs
light energy
Chemotrophs
chemical compounds
Energy producing pathways
aerobic or anaerobic
Carbon cycle
- CO2 removed and returned
- Primary producers, consumers, decomposers
Nitrogen Cycle
- Nitrogen fixation
- Ammonification
- Denitrification
Pathogen
Bacteria or infectious agent that causes harm to its host
Pandemic
Widespread (worldwide) epidemic
Epidemic
Within the same population at the same time
Endemic disease
always present, usually in low incidence, in a population
Zoonoses
Diseases normally in animals that can infect humans (animals to humans**)
Plague of Athens (430 B.C.)
salmonella enterica (typhoid fever)
Bubonic Plagues – Yersinia pestis
- Justinian Plague (from 541-750) – 1⁄4 - 1⁄2 of the human population
- Black Death (1346-1361), Mid 1600’s
(New cases annually= 10-20 American Southwest)
Historical & Foodborne Diseases: Biofilms
can resist 1,000x antibiotic concentration
*catheters, orthopedic devices
Foodborne Diseases
- Botulism
- E. coli
- Listeria monocytogenes
antibiotic
Chemical that suppresses or inhibits the growth of other organisms
Resistance
arises from overexposure to antibiotics * Humans and livestock
MRSA (methicillin-resistant Staphylococcus aureus)
- Usually easily treated – normal strain
- Skin, can be in the bloodstream, lungs, urinary tract, sites of injury
- Community-associated (23 yrs average), normal 68 yrs average
Nitrogen Fixation
Biological nitrogen fixation
– only prokaryotes (65% in agriculture)
- Symbionts (more than free living by 10x) and free living
* Legumes
Prokaryotes in our food
- Cheese, yogurt, pickles, kimchi, sauerkraut, beer, wine, bread
- Bacteria and yeast (really a fungus)
- Allowed for longer storage of milk products and other foods
Bioremediation
- Using biological organisms to remove harmful chemicals from the environment
- Fertilizers to **oil spills
to infect a new host, steps!
- permission
- attachment
- entry
protein causing CWD
prion
largest lineage of bacteria
proteobacteria
found in deep oceans or along volcanoes
extremophiles, archaea OR bacteria
(could be any)
prokaryotes have an essential role in…
both N and C cycles
why do we still not know much about prokaryotes?
99% unculturable
bacterial diseas in both humans and animals
zoonoses