4. Paramecia: possess a contractile vacuole to pump water out of the cell
1.shape determining proteins
2. FtsZ = forms a "z-ring" in spherical cells
3. MreB: forms coil inside rod-shaped cells
4. CreS "crescentin": -forms a polymer along the inner side of crescent-shaped bacteria
Nucleus: euks vs. prok.
1. euks: have well-defined nucleus delimited by nuclear membrane
2. proks: have a nucleoid region that extends throughout the cytoplasm
1. in nucleoid
2. excluding a lot of protein
3. nucleoid forms about 50 loops or domains. Within each domain, the DNA is supercoiled by DNA-binding proteins.
1. proteins and DNA floating around "flag" or "anchor"
2. specific proteins recognize parts of DNA and code it back to flag "the origin"
3. proteins help bind, organize, and store DNA
Transcription and Translation
1. RNA polymerase transcribes DNA into a single strand of RNA.
2. For most genes, it is messenger RNA.
A. mRNA immediately binds to a ribosome for translation into a polypeptide.
B. This is aided by transfer RNA (tRNA), which brings the amino acids to the ribosome.
D. In prokaryotes, translation is tightly coupled to transcription. (saves time!)
tells amino acids their own order to make proteins
PROKARYOTE Protein Synthesis and Secretion
1. membrane proteins and secreted proteins are synthesized in association with the cell membrane.
2. aided by signal recognition particle (SRP) which binds to growing peptide
3. proteins supposed to be outside
4. SRP takes protein sequence to transport protein that knows that specific code
5. SRP is recognized by protein
1.also named cell fission
2. , requires highly coordinated growth and expansion of all the cell’s parts.
3. Unlike eukaryotes, prokaryotes synthesize RNA and proteins continually while the cell’s DNA undergoes replication.
4. Bacterial DNA replication is coordinated with the cell wall expansion and ultimately the separation of the two daughter cells.
2. In prokaryotes, a circular chromosome begins to replicate at its origin, or ori site.
3. Two replications forks are generated, which proceed outward in both directions.
a. -At each fork, DNA is synthesized by DNA polymerase with the help of accessory proteins (the replisome).
B. As the termination site is replicated, the two forks separate from the DNA
1. Replication of the termination site triggers growth of the dividing partition, or septum.
2.The septum grows inward, at last constricting and sealing off the two daughter cells
3. orientation of septum determines shape of cocci
2. Random planes
3. Perpendicular planes
1. polar aging: when bacterial cell poles differ in origin & "age"
2. In bacteria that appear superficially symmetrical, polar differences may appear at cell division
3. Some bacteria generate two kinds of daughter cells: one stationary and the other mobile
4. Example: the flagellum-to-stalk transition of the bacterium Caulobacter crescentus
5. poles of each daughter cell differ chemically from each other
extensively folded intracellular membranes
(a specialized structure)
polyhedral bodies packed with the enzyme Rubisco for CO2 fixation
(a specialized structure)
to increase buoyancy
(a specialized structure)
1. Specialized Structures
2. Glycogen, PHB, and PHA, for energy
3. Sulfur, for oxidation
1. Membrane-embedded crystals of magnetite, Fe3O4
2.Orient the swimming of magnetotactic bacteria
1. also named fimbriae
2. straight filaments of pilin protein
3. Used in attachment
4. sex pili used in conjugation- to pass DNA transfer between 2 bacterial cells
5. twitching motility
1. membrane-embedded extensions of the cytoplasm
2. Tips secrete adhesion factors called holdfasts
3. "glue" hold bacteria to specific surface
1. intercellular connections that pass material from one cell to the next.
2. can share cytoplasm to share food, communicate, etc.
1. how Prokaryotes that are motile generally swim by means of rotary
2. peritrichous cells have flagella randomly distributed around cell, hair all over bacteria!
a. hair rotate together in a bundle behind the swimming cell
3. each is made of flagellin: a spiral filament of protein monomers
4. filament rotates by a omtor driven by proton motive force
a. moves CW or CCW
1. movement of a bacterium in response to chemical gradients
2. Attractants cause CCW rotation.
aFlagella bundle together - Push cell forward - “Run”
3. Repellents cause CW rotation.
a. Flagellar bundle falls apart
b. “Tumble” = bacterium briefly stops, then changes direction
4. alternating runs and tumbles cause a “random walk.”
5. receptors detect attractant concentrations
a. sugars, amino acids
6. attractant concentration increases and prolongs
a. sugars, amino acids
7. attractant concentration increases and prolongs run
a. "biased random walk"
b. causes net movement of bacteria toward attractants (or away from repellents)
Spore formation as virulence factor
1. Gram-positive rod; rods occur in chains
2. causes anthrax, which was the disease studied by Robert Koch when formulating the famous Koch's Postulates
3. forms endospores that can survive in soil and animal products for decades
4. most commonly mentioned candidate for biological warfare because the endospores are so resistant to drying that they can survive dissemination in the air; infection via inhalation has nearly 100% mortality rate
function in attachment
short and very thin
up to 1000/cell
functions in motility
motility in spirochetes
1.protoplasmic cylinder: inner cylinder
rigid, generally helical
2. endoflagellum: rigid, rotates attached to one end of protoplasmic cylinder
3. outer sheath (flexible)
1. mitochondria and chloroplasts became eukaryotic organelles following the intracellular engulfment of prokaryotic cells
2. EVIDENCE, both m and c:
a. outer and inner membranes: outer like euk's, inner like prok.s
b. contain ribosomes that resemble those of bacteria (70s instead of 80s)
c. contain DNA (unusual for an organelle) and that DNA is circular like a bacterial chromosome
4. replicate semi-autonomously, replication not fully coordinated with rest of cell
-Major elements in cell macromolecules -
C, O, H, N, P, S-
Ions necessary for protein function - Mg2+, Ca2+, Fe2+, K+
1.Trace elements necessary for enzyme function
2.Co, Cu, Mn, Zn
defined minimal medium
contains only the compounds needed for an organism to grow.
Some organisms have adapted so well to their natural habitat that we still don’t know how to grow them in the lab.
1.obtain energy from oxidation-reduction reactions
inorganic molecules as a source of electrons
considered an autotroph
use organic molecules
proton motive force.
1.the H+ gradient plus the charge difference form an electrochemical potential
2.(A membrane potential is generated when chemical energy is used to pump protons outside of the cell)
3. The potential energy stored can be used to transport nutrients, drive flagellar rotation, and make ATP by the F1FO ATP synthase.
1. makes 79% of earths atmosphere
2. nitrogen fixers:possess nitrogenase, which converts N2 to ammonium ions (NH4+).
3. Nitrifiers: oxidize ammonia to nitrate (NO3–).
4. Denitrifiers: convert nitrate to N2
Selective permeability is achieved in three ways:
1.Substrate-specific carrier proteins, or permeases
2. Dedicated nutrient-binding proteins that patrol the periplasmic space
3.Membrane-spanning protein channels or pores
1. helps solutes move across a membrane from a region of high concentration to one of lower concentration.
2. -It does not use energy and cannot move a molecule against its gradient.
Coupled transport systems
1. are those in which energy released by moving a driving ion down its gradient is used to move a solute up its gradient
2. symport : travel in same direction
3. antiport: actively transported molecule moves in direction opposite to driving ion
1. largest family of energy-driven transport systems is ATP-binding cassette superfamily, or ABC transporters
2. found in all 3 domains of life
3. 2 main types:
a. uptake ABC T's: critical for transporting nutrients
b. Efflux ABC transporters: generally used as multidrug efflux pumps.
1. are specialized molecules secreted to bind ferric ion (Fe3+) and transport it into the cell.
2. iron released into cytoplasm and reduced to more useful ferrous (fe2+) form
3. recognizes transferin, protein stores iron
1.a process that uses energy to chemically alter the substrate during its transport.
2.phosphotransferase system (PTS) is an example present in all bacteria.
3. PTS attaches phosphate added to sugars so you get overall influx of sugars
1.We have succeeded in culturing only 0.1% of the microorganisms around us.
2. Microbes in nature exist in complex, multispecies communities, but for detailed studies they must be grown separately in...
2 main types of culture media
1. liquid or broth
2. solid (usually gelled with agar)
a. useful for trying to separate mixed cultures form clinical specimens or natural environment
-Dragging a loop across the surface of an agar plate
-Tenfold serial dilutions are performed on a liquid culture-A small amount of each dilution is then plated
are nutrient rich but poorly defined.
liquid leftover from grinding meat
are precisely defined
are complex media to which specific blood components are added.
favor the growth of one organism over another
exploit differences between two species that grow equally well
Petroff-Hausser counting chamber
Microorganisms can be counted directly by placing dilutions on a special microscope slide,
Fluorescence-Activated Cell Sorter (FACS)
laser hit cells emits fluroescent light off of bacteria cells and count those cells w/out destroying them
A viable bacterium is defined as being capable of replicating and forming a colony on a solid medium.-Viable cells can be counted via the pour plate method
Microorganisms can be counted indirectly via biochemical assays of cell mass, protein content, or metabolic rate.
where one parent cell splits into two equal daughter cells
how long it takes bacteria to double
2^n , n = # of generations
or rate of increase in cell numbers or biomass, is proportional to the population size at a given time.
The simplest way to model the effects of a changing environment is to culture bacteria in a
cells in a population achieve a steady state, which allows detailed study of bacterial physiology.
ensures logarithmic growth by constantly adding and removing equal amounts of culture media.
ex/human gastrointestinal tract
1. In nature, many bacteria form specialized, surface-attached communities
2. one or multiple species, and can form on a range of organic or inorganic surfaces.
3. Bacterial biofilms form when nutrients are plentiful.
Once nutrients become scarce, individuals detach from the community to forage for new sources of nutrients
4.Biofilms in nature can take many different forms and serve different functions for different species.
5.The formation of biofilms can be cued by different environmental signals in different species.
1.Clostridium and Bacillus species can produce dormant spores that are heat resistant.
2.Starvation initiates an elaborate 8-hour genetic program that involves:
3.An asymmetrical cell division process that produces a forespore and ultimately an endospore
4Sporulation can be divided into discrete stages based primarily on morphological appearance.
1.Bacteria faced with environmental stress undergo complex molecular reprogramming that includes changes in cell structure.
2.Examples include:-Endospores of Gram-positive bacteria-Heterocysts of cyanobacteria-Fruiting bodies of Myxococcus xanthus-Aerial hyphae and arthrospores of Streptomyces
Anabaena differentiates into specialized cells called heterocysts.-Allow it to fix nitrogen anaerobically while maintaining oxygenic photosynthesis
Myxococcus xanthus uses gliding motility.-Starvation triggers the aggregation of 100,000 cells, which form a fruiting body.
1.Streptomyces bacteria form mycelia and sporangia analogous to those of fungi.
2. As nutrients decline, aerial hyphae divide into arthrospores that are resistant to drying