Flashcards in The Final Countdown Deck (114):
Built first compound microscope, looked at cork, coined term cell
Antonie van Leeuwenhoek
observed single-celled microbes and called them "small animals", built single-lens magnifiers
Disproved spontaneous generation through the cover over meat experiment
Disproved spontaneous generation by boiling broth covered and uncovered
Disproved spontaneous generation by heating broth in swan neck bottles, one broken and one normal
Established postulates which established a link between a specific microbe and disease
1) microorganism is present in every case of disease and not in healthy people
2) Microorganism must be grown in pure culture
3) Same disease must result when a healthy host is infected with disease
4) the same strain of microbe must be obtained from the new diseased host.
Swallowed bacterium to give himself stomach ulcers to prove his theory right
Used medical statistics to demonstrate the significance of mortality due to disease
Discovered penicillium mold generated a substance that kills bacteria
Howard Florey and Ernst Chain
Purified penicillin to make first commercial antibiotic
Studied microbes in natural habitats, discovered lithotrophs, developed enrichment cultures, built Winogradsky column
Bright Field Microscope
light source on specimen to produce a virtual image that shows something is there but can't see specifics or viruses
Dark field Microscope
shows microbes as halos of bright light against darkness, useful for narrow cells
Shows refractive difference in cell components (shows internal components)
adds dye or protein (fluorophores) to specimens to show fluorescent image of object, protein, structure
Methylene blue/ crystal violet/ safranin, bind to negatively charged molecules
Eosin/ Rose bengal, bind to positively charged molecules
Gram stain procedure
Add crystal violet->both are purple
Then add Iodine as a mordant to trap the dye in the cell wall-> both still purple
Add alcohol (decolorizing step)-> now only gram positive is purple, gram negitive is clear
Clear cells are low contrast so a counter stain is added (safrin) to see gram negative cells as pinkish/red
Safrin does stain gram positive but the violet is too dark to see it
Electrons used instead of light, used for viruses and small cell structures
Scanning electron microscope
Shows surface details and color
Transmission Electron Microscope
Shows interior details and components (color can be computer generated)
Single celled, Peptidoglycan cell wall, Lack membrane bound nucleus, Found in soil/water/air, Some species may survive extreme temp/pH/salt
RNA sequences, Unusual metabolic characteristics, Usually found in extreme temp/pH/salt, associated with extreme enviornments, Don’t have peptidoglycan in their cell walls but can have pseudopeptidoglycan:
use L-glycerol and have ether links
the movement of a bacterium in response to chemical gradients.
Attached bacteria form complex, slime enclosed communities containing Exopolysaccharide that makes it sticky, form when nutrients are plentiful
communication of microcolonies to form biofilms
Peptidoglycan (Murein) Structure
Meshlike polymer of identical subunits forming long strands containing 2 sugars and amino acids.
Two alternating sugars:
N- acetylmuramic acid (NAM)
bacteria produce beta-lactamases to keep penicillin from binding to the cell wall, or they have efflux pumps that pump penicillin out of the cells
why are gram positive bacteria purple?
The teichoic acid threads retain the stain
Thermophiles or Hyperthermophiles adaptions
They have increased hydrogen bonds, less flexible polypeptides, and other DNA binding proteins to stabilize in extreme heat
ex. Taq DNA polymerase
How do cells survive in a hypotonic environment
They have pressure sensitive channels in the plasma membrane to allow solutes to leave the cell
How do cells survive in a hypertonic environment
The cells can increase cellular osmotic concentration by synthesizing or importing solutes
Adaptations of Halophiles
Have ion pumps to excrete sodium and replace it with other cations like potassium
Adaptations of Psychrophiles
Have unsaturated fatty acids to allow the membrane to remain semi-fluid in the cold
involves organic electron donors and inorganic or organic terminal electron acceptors.
involves inorganic electron donors and inorganic or organic terminal acceptors.
involves photo (light) excited electrons
Studied Streptococcus pneumoniae in mice
Hypothesized that the bacteria could “transfer information” to each other, smooth strains caused cell death and even killed could pass the fatal gene to different cells of a different strain
Horizontal gene transfer requiring cell contact. Live cell to live cell
condenses chromosome to keep it in one small area, done by topoisomerases
Positive DNA supercoiling
DNA is overwound, extreme archaea have it
Negative DNA supercoiling
DNA is underwound, not as tight, found in bacteria, eukaryotes, and some archaea
Initiation of replication of DNA
starts at single origin of replication, replication bubble forms and 2 replication forks move in separate directions, DnaA initiates replication (rise as cell grows and is activated by binding of DnaA-ATP complexes) and SeqA inhibits replication
is the process of importing free DNA into bacterial cells.
Cells must be competent which is generated by quorum sensing and Competence factor will induce it (except in gram negative bacteria)
Methyl Mismatch repair
is based on recognition of the methylation pattern (parent strand) in DNA bases, hopefully parent strand has correct sequence so MutS can bind to mismatch and it can be looped, cleaved by MutH and repaired and replaced with the correct sequence
Nucleotide excision repair
An endonuclease removes a patch of single-stranded DNA containing damaged bases.
Does not distinguish between parental/daughter strands.
Jacques Monod and François Jacob
proposed idea that genes could be regulated by studying E.coli and inducible lactose enzymes, glucose is preferred carbon source
Only turns on gene for lactose utilization if there is lactose in the media- induction because LacZYA operon makes glucose from lactose but you don't need it if glucose is already available
most common form of glycolysis occurs in the cytoplasm of the cell, and functions in the presence or absence of O2, has 2 stages the glucose activation stage and Energy yielding stage, yields 2 pyruvate, 2 ATP, and 2 NADH
Studied mostly in prokaryotes, occurs in the cytoplasm, enables intestinal bacteria to feed on mucus, less efficient, most primitive, yields 1ATP, 1 NADH, and 1 NADPH
Occurs in the cytosol of the cell (aqueous component of cytoplasm), can operate independently or at the same time as other pathways, no oxygen requirement, yield 1 ATP and 2 NADPH
Antibiotic classification- Broad Spectrum
Effective against many species
Effective against few or a single species
Antibiotic classification- bactericidal
antibiotics kill target organisma
Antibiotic classification- bacteriostatic
antibiotics prevent growth of organisms so immune system can take care of it and create antibodies against it
Minimal Inhibitory Concentration
is the lowest concentration that prevents growth, tested by diluting antibiotic
Studied Tobacco Mosaic Disease, observed agent was not removed by filters
Studied Tobacco Mosaic Disease:
agent must be so small it passes through filters
Loeffler and Frosch
Studied foot and mouth disease
Studied sarcomas (tumors) in chickens, diseased chickens could transmit tumors to healthy chickens= cancer transmitted by a virus
molecule of DNA or RNA enclosed in coat of protein (nucleocapsid), cannot reproduce independent of living cells nor carry out cell division, helical or icosahedral or complex shape, variety of genome types
Bacteriophage quickly replicates, killing host cell, causes cell burst by creating an enzyme that breaks down cell walls, can be triggered by stress
Bacteriophage is quiescent, integrates into cell chromosome, as a prophage, can reactivate to become lytic
Herpes Virus characteristics
-Tegument (layer of proteins around it)
-attach to host heparan sulfate and full atachment requires nectin
-enter via fusion or endocytosis
-release via exocytosis and by upregulating host heparanase
each partner species benefits from the other and may fail to grow independently ex. lichen
optional cooperation where both species benefit, but can grow independently, ex. gut flora
One species benefits, while the partner species neither benefits nor is harmed, ex. Beggiatoa in wetlands, consume H2S and help out other organisms
One species benefits by harming the other.
Relationship is nonspecific, ex. strepomyces that secrete antibiotics into soil
One species benefits at the expense of the other, ex. legionella
Under stress the Zooanthellae are expulsed from the coral, or can occur due to infectious disease from Vibrio shiloi bacteria that kill zooxanthellae
Milk --> Cheese
obtain milk and pasteurize it --> add starter cultures (bacteria ferment and pH declines, milk proteins unfold exposing hydrophobic residues)--> rennet added (sometimes) and caseins are cleaved into hydrophobic (curds) and hydrophilic (whey) components --> add salt to curds --> age with microbes
Innate immune system physical barrier-skin
Has SALT (the Langerhans cells that digest forgien debris and take to other immune cells for them to determine if an immune response is appropriate)
Innate immune system physical barrier-mucous membrane
Has products that can destroy pathogens
-Lysozyme- hydrolyzes sugar bonds in peptidoglycan
-Lactoferrin- keeps iron from plasma
-Lactoperoxidase- creates superoxide radicals
Innate immune system chemical barrier-bacteriocins
Peptides produced by normal flora.
-Lantibiotics: Many Gram (+)
Forms holes in target cell membrane.
-Colicins E. coli (Gram -)
Damage DNA, stop protein synthesis, & forms holes in inner membrane.
Innate immune system chemical barrier- complement
Host serum proteins that augment (or “complement”) the antibacterial activity of antibodies.
-Have signals that recruit phagocytes to their activation site.
- Can puncture cell membranes causing cell lysis.
Innate immune system chemical barrier- cytokines
Soluble proteins that act as signaling molecules.
-Cell movement (chemokines)
Innate immune system chemical barrier- Interferons
Type of cytokine
-Type I: Bind to receptors on uninfected host cell, and render them resistant to viral infection.
Cleave dsRNA and block viral RNA translation.
-Type II: Has immunomodulatory function
Innate immune system physical barrier- Inflamation (signs)
Nonspecific, can release kalikrein to increase capillary dilation and blood flow, fibrin clots, phagocytes accumulate in inflamed area
5 Cardinal signs:
Innate immune system- fever
Pyrogens are substances that raise the hypothalamus set-point: 98.6˚F
-Impairs microbial growth.
-Activates immune cells.
Innate immune system- phagocytes
host cells have CD47 to differentiate
Innate immune system- natural killer cells
Destroy infected and cancerous host cells
-healthy host cells make MHC class 1
Adaptive immunity- Humoral immunity
B cells produce antibodies (when differentiated into plasma cells)
that directly target antigens of invaders, recognize epitotes, presents helper T cells with a piece of antigen and it is activated by a peptide
Adaptive immunity- Cell-mediated immunity
Antigen presenting cells activate T helper cells which rapidly divide and activate cytotoxic T cells which can directly kill infected host cells, handles intracellular microbes
Stimulate stronger immune response than normal antigens by “tricking” T cells into activation, nonspecific and evoke global T cell response
measured by the number of microbes that will cause infection in half of test animals
Measured via the number of microbes that kill half of test animals.
Easiest way to transmit disease
through a sneeze or cough
Utilizes lytic substances.
Lytic substances “attack” normal host tissue
ex. collagenase and streptokinase
Chance scenarios allow spread to deeper tissues.
Ex. Insect bites or wounds
blood (complex media with specific blood components)
favor growth of one species over another ex. only gram negative grow on MacConkey
exploit differences between 2 different species that grow equally well ex. only colonies that ferment will be pink
Rely on other organisms for carbon source, release CO2
Reduce CO2 for carbon to make complex cell constituants
Energy from oxidation-reduction reactions
Why are enzymes useful?
Bring substrates close together at specific sites (active sites) to react which can lower activation energy
Competes at active site to fill it and keep the substrate from binding ex. penicillin
Competes at allosteric site to change enzyme conformation
Deep branching Thermophiles- Aquificae
Oxidizes hydrogen gas to form water.
-Found in thermal vents
-Ether linked membrane lipids.
- grows long rod shape in wild, and forms pink streamers
Deep branching Thermophiles- Thermotogae
“Toga”-Loosely bound sheath, absence of “classical” outer membrane- possible advantage in high heat
-Mosaic (shared) genomes (bacterial-archaeal)
-Gram negative (atypical)
Deep branching Thermophiles- Chlorofelxi
-have chlorosomes and are green
-sulfur is toxic
-form biofilms in hot springs
-gram negative, but with thick peptidoglycan
-mutualistic associations in microbial mats
-no standard cell shape, can be multicellular
-have heterocysts for nitrogen fixation, thylakoids for photosynthesis, and carboxysomes to fix CO2
Gram positive firmicutes
-many form endospores
-many are pathogens ex. botulism
Gram positive Actinobacteria
-form complex multicellular filaments
-some are acid-fast- technically stained gram positive but it is difficult to stain
-most likely arose from a single ancestor
Phylogeny of eukaryotes
Algae and green plants, protists, Fungi and animals
competitive inhibitor for neuraminidase so influenza can't release from host cell, must be taken early into infection
Antiviral, acts as nucleotides, incorporated into viral DNA, stops polymerization of herpes virus
-Changes the host cell membrane which surrounds healthy cells so that virus can't enter cells
-not an antiviral, in order to be effective must be applied at earliest signs of outbreak
Peptidoglycan (cell wall) synthesis is halted so precursors are never carried across the cell membrane
inhibits cell wall synthesis of Gram + bacteria by inhibiting transpeptidase by binding to substrates
treats fungal infections ex. blastomycosis, weakens cell membranes