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1900-deaths causes by diseases, viruses, bacteria were high on the list (influenza, TB, gastroenteritis) but then vaccines, medicines, antibiotics were created so in 2008, deaths by infectious agents decreased. Now heart disease and cancer are highest due to living longer and unhealthy living styles
1. the suspected pathogen should be present in all diseased animals and not in healthy ones
2. suspected organism grown in pure culture (to be sure you're working with only 1 organism, to isolate suspected pathogen) outside host animal should cause disease in healthy animal
3. if it's isolated again, it should be same to original isolation
Hard with viruses because they need to reside and replicate in a host cell.
Can only be used by "true pathogens" like anthrax and TB (only able to caue disease in healthy hosts)
Not good for opprotunistic pathogens (organisms that only cause disease in an immunosuppresed organism (infection, genetic, other organism)
von Leuuwenhoek - 1st bacteria 1687
Pasteur - spontaneous generation 1861
Watson/Crick -DNA strcuture 1953
Pace - phylogenetic strains 1986 and rRNA sampling 1987
First genome sequence 1995
Era of environmental genomics, proteonomics, and transcriptomics (2004-now)
Membrane bound organelles (nucleus, mitochondria, chloroplasts)
Algae, fungi, protozoa
cytoplasmic membrane, ER, ribosomes, nucleus, nucleolous, nuclear membrane, golgi, cytoplasm, mitochondria, chloroplast(maybe)
Not true cells.
Lack metabolic abilities of their own (must infect a cell, obligate parasite)
Very important in genetic changes in bacteria and other cells (transduction, exchanges of genetic material between cells)
1. Eukarya (animals, plants, fungi)
3. Archaea (live in extreme environments like high NaCl concentrations or very hot (sea vents)) hard to study because its hard to replciate environment in the lab
Bacteria and Archaea are Prokaryotes
Stramatolites - fossilized microbial mats, biofilm (like plaque)
comprised of multiple different organisms
ofest found is 3.5byo
lacked oxygen, other gasses were oresent (methane, CO2, nitrogen, ammonia)
hotter than it is now (may have reached 100 degrees C)
free water accumulated as earth cooled
earliest cells were likely heat tolerant and didnt need oxygen
RNA=earliest replicating entity?
RNAs can perform different catalytic functions
-have ribozymes (can disrupt RNA and DNA bonds - used in gene therapy)
RNA may have been enclosed in a lipoprotein vesicle (gave stability). RNA is very unstable, hard to work with.
Primative organism became more complex leading to proteins then DNA
oxygenic photosynthesis evolved in cyanobacteria 2.8bya - uses light to produce ATP and oxygen
produced O2 that oxidiezed Fe2+ to Fe3+
when Fe2+ was consumed, atmospheric oxygen was able to accumulate
atmosphere changed from anoxic to oxic.
oxygen was now available as an electron acceptor - more ENERGY!
formation of ozone layer, more environments available for colonization (no UV light which induces mutations)
as cells became larger, genomes became larger
Evolution of multiple chromosomes and nucelsu instead of one big chromosome (helps conserve energy). multiple chromosomes give greater chance of genetic diversity with corssing over and saves more time and has less of a chance of detrimental mutations, increases efficiency
Why did other organelles evolve?
chloroplasts and mitochondrial 16s RNA sequences are closely related to bacteria (rather than eukaryotes)
Eukaryotic organelle ribosomes are inhibited by antibiotics that inhibit bacteria
Mitochondria and chloroplasts have small circular pieces of DNA like plasmids of bacteria
Functionally homologous (does same thing in each organism)
Any change over time must be extremely slow
Most widely used is ribosomal RNA
isolate DNA -> PCR -> sequence analysis -> generate phylogenetic tree
total length of the branches separating any two organisms is proportional to their evolutionary distance
everything fits into the 3 Domains (bacteria, archaea, eukarya)
almost all bacteria have cell walls containing peptidoglycan
peptidoglyca is not in Eukaryotes
Archaea have variation of PG -
Bacteria and eukaryotes have ester link between glycerol and fatty acid chains
Archawa have ether link (not ester link)
science of biological classification based on phenotypic analyses
classification = arrangement into groups
nomenclature = assignment of names to taxonomic groups
identification = determining that a particular isolate belongs to a recognized taxon
morphology (size, shape, gram reaction)
no universally accepted concept of species - phenotypic, genotypic, and phylogenic data used
important grouping traits - 16S sequence (anything with a greater than 3% difference at 16S levels is a new species, needs >97% agreement)
determined by characterization of a single species descended from a single cell - can have tremendous variation
Ex; Streptococcus agalactiae (inhaled by newborns, some cause meningitis)
7,000 species formally recognized.
Rod - bacilli
Vibrio - curved rod
Spiral - spirilla, spirochete
Cocci can form chains, clusters or tetrads (or larger cubes)
Rods can form chains
cell arrangements determined by plane division
1 plane - diplococcus - if stays attached streptococcus chain
2 perpendicular panes - tetrad(4cells) - sarcina (packet of 8-64 cells)
several planes - irregular clusters (staphylococcus)
rods takes less energy to cut in half short ways than long ways - energy conservation
Outside of cytoplasmic mem = bind substrates in the environment, transport
Inside of " " = energy yeildeding reactions - pump protons out
Span " " = various functions - integral proteins
lipids are different than for bacteria or eukaryotes. ether linkages instead of ester between glycerol and side chains. isoprene side chains instead of fatty acids
can have glycerol diethers that form lipid bilayers or diglyercol tetraethers that form a lipid monolayer (decreases flexibility of membrane, increases strength and stability especially in heat)
glucose gets P group from transmembrane protein - there are 3 specidic protein compoenents for the specific sugar being transported and 2 nonspecific proteins that can be resued for many PTS systems - PEP -> P group transported -> glucose -> glucose 6-P
Energy conservation mechanism, doesn't use P from ATP so you can make more ATP in the long run (gets P from PEP)
3 components - periplasmic binding proteins (environment directly outside of cell usually between cell mem and cell wall or further) - membrane spanning proteins, ATP hydrolizing proteins. 200+ ABC systems identified - uptake of nutrients very specific
Specific - cell can control waht sugars are brought into cell, doesnt bring in sugars it can't use
nonspecific- energy conservation, can be reused
Sec system (secretory)
proteins are transported across plasma membrane or integrates them into the plasma membrane itself - signal peptide (N terminal) is recognized - chaperones (SecB and SRP -signal recognition particle) transport preprotein to translocon
polypetide transported unfolded bc too big if it isn't - c terminus has wall anchor motif LPXTG 5 AA (X is any) embedded into mem or cell waqll if they have this motif, recognized by sortase
varies, can be connected directly between D-alanine and diaminopimelic acid (DAP)
-can be connected by peptide interbridge
-target of antibiotics
Gram + like S. auereus typically linked by peptide interbridge, separated a bit btwn NAM NAG, thick PG layer so they can retain rigidity through multiple layers
-Gram - cells like e. coli have NAMNAG directly linked and close together, needs to be compact and rigid because they have think PG layer
x axis = glycosidic bonds
y axis = peptide bonds
lattice work, chain link fence
penicillin prevents formation of cross-links of PG, does not destroy existing cross-links - most effective on young actively dividing growing cells after replication process, then these cells are sensitive to osmolarity changes
cells can survive in an isotonic enronment without a cell wall (protoplast) - very fragile
lysozyme can destory the glycan portion (NAM-NAG) enzyme found in tears, sliva, eggs whites - can destroy pre-existing bonds
thick PG layer, thin periplasmic space (or non-existent), teichoic acids (polymers of glycerol or ribitol joined by phosphate groups, connected to NAME or to membrane lipids), surface proteins (noncovalently attached, synthesis of PG, adhesion, etc), use peptide interbridge, tolerate changes in osmolarity better than gram - cells - ONE MEMBRANE, energy conservation!
negative = simple structure, no LPS (sensitive to antibiotics like penicillin)
composes of phospholipids, proteins, and LPS
LPS varies greatly, toxic to many animals (endotoxin), antigenic structure/diversity. porins - allow diffusion of small molecules, not permeable to enzymes, retained in periplasmic space, chemoreceptors
Frimbriae = short appendages for attachment, usually specific, possible location to attack pathogen (block fimbriae)
Pili = larger than frimbriae, required for bacterial mating(conjugation) genetic exchange of materials between organisms, can be site for viral attachment. why are they larger? because DNA needs to pass through. upregulation of surface proteins in virus before conjugation (movement in a single direction)
specialized cells for survivial. resistant to heat, acids, dessication, disinfectants, radiation. can survive for thousands of years, but can germinate in 15 minutes, need special stain to visualize. Only 3 genera make spores and they're all gram + rods (bacillus, clostridium, sporsarcina).
Survival mechanism triggered by a depeltion of nutrients, endospore formation, spore becomes resistant to bad envrionments, better equipped to survive than normal cells. EX Anthrax
exosporium = thin covering, lost quickly, fragile
spore coat = several protein layers, impermeable
cortex = cross linked peptidoglycan for strucutre and rigidity
core wall = surrounds core
core = normal cell structures, metabolically inactive, contains all genetic info everything needed for survival, resting structure (dormant), doesnt need to worry about getting nutrients, can survive for 1,000s of years
Dipicolinic - with Ca2+, helps to dehydrate core, stabilize DNA, resistnat to heat denaturation
dehydration also confers resistance to H2O2 causes enzymes to become inactive.core becomes acidic, small acid soluble proteins, bind to DNA for UV protection. these proteins produced, bind to DNA to provide more stability and potect against UV radiation.
dehydration -> changes shape of enzyme ->cant function ->shuts down
normal cell ->dehydration stimulus with depeltion of nutrients like carbon and nitrogen -> conversion to a sporangium (committed to sporulating cell).
Sporulation ->indentations, condense DNA ->spore vs everything else ->spore has essential DNA ->spore gets layers _>dehydrated to decrease metabolism -> calcium and dipicolinic acid ->maturation -> lysis of cell and release of endospore
motility - vary in number and arrangement - polar (attached at one or both ends of the cell
monotrichous = single flagellum "one hair-like"
lophotrichous = small bundles, clusters or tufts at one pole
amphitrichous = flagella at both poles
peritrichous = flagella dispersed randomly over the structure (NOT POLAR)
all have similar structure- gram neg LPS, lots of periplasm, 2 membranes, different flagella structure in Gram pos (no L ring, modified P ring). series of rings, hook does rotation, filament (corkscrew, individual flagellin)
C, MS, and P rings make up th basal body - responsible for rotary motion. Energy from proton motive force. 1000 protons/rotation. Actual mechanism unknown. Turns because of conformational change.
ATP synthase in mitochondria works like this. Diffusion of protons causes a change and rotates. about 6 protons diffuse back in to make ATP, lots of energy needed! takes alot of protons to make one rotation
Filament composed of a single protein (flagellin) Flagellin subunits transported through filament's hollow internal core. growth is at the tip not at the bsa, self assembles. filament is final structure made. flagellin in helix type formation. subunits travel thru internal tube and filament to the tip. no enzyme needed bc self assembles. growth from inside out.
Forward or Random (run or tumble)
Forward mvoement -> flagella pushes apart (tumble) and stop ->rotate to different position ->run
Series of runs and tumbles. random movement with no stimulus but may respond to stimulus
phototaxis, aerotaxis (O2), osmotaxis (osmolarity)
other things cells respond to to.
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