Micro exam 2 Flashcards
peptidoglycan
backbone of cell wall in prokaryotes, composed of repeating sugars NAG and NAM
assembly of cell wall
NAG and NAM repeat, assembled by enzymes transglycosylae, tarnspeptidase, polymerase, and hydrolase, how cell wall is made can be used for better antibiotics
Cytoplasmic Phase
NAG/NAM are built in cytoplasm and are constantly replenished, particularly when dividing
Membrane Associated Phase
enzymes link NAG and NAM with lipids to form peptidoglycan
Extracytoplasmic phase
new peptidoglycan moves from inside of cell towards outside, incorporating into cell wall
teichoic acid
in gram positive bacterial cells in addition to many layers of peptidoglycan (makes the gram positive cell have an overall negative charge)
Gram positive cell walls
very thick wall of peptidoglycan covering the plasma membrane with various lipoteichoic acid and wall associated proteins
Gram negative cell walls
outer membrane with porins with lipopolysaccharide (O-polysaccharide and lipid A), then a periplasmic space with lipoproteins, a small layer of peptidoglycan and then the plasma membrane
lipopolysaccharide layer
outer membrane, composed of lipids, proteins
Porins
proteins contain channels that vary in size and specificity and they are responsible for the passage of molecules and ions into and ort of the gram negative cell
translocation protein systems
move substances out of the cell
Periplasmic space
space between the plasma membrane and the other membrane, filled with gel-like material and contains variety of proteins secreted by the cell
M protien
virulence factor in gram positive organisms, protrudes from cell wall, required for infection, antibodies can inhibit it
Mycolic acid
in gram positive organisms, synthesizes waxy lipid known as mycolic acid that makes organisms resistant to antibiotics/disinfectants/ect
Lipid A
gram negative bacteria, anchors the LPS portion of the outer membrane to phospholipid bilayer, releases endotoxins
O polysaccharides
gram negative, carbohydrate chains that are part of the outer membrane located on the side of the membrane that faces the extracellular fluids
structures outside of bacterial cell in adherence
glcocalyx, fimbraie, and pili
structures outside of bacterial cell in movement
flagella, axial filament, and pilli
Glycocalyx
sticky substance on surface of cells made of polysaccharides and polypeptides, many is known as cell layer, and if adhered tightly is known as capsule
slime layer
dental decay, permits organisms to adhere to surface and then many organisms adhere to one another, form of glycolyx
The capsule
form of glycocalyx, required for infection, inhibits phagocytosis
Fimbriae and Pilli
cell wall components involved in adherence, composed of pilin protein, pili also used in transfer of genetic material through conjugation
immune escape
ability to evade a host immune response
phase variation
number of pilli decreases after initial infection, taking away target for antibodies
antigenic variation (post-translational modification)
change or mask the structure of pilli so that antibodies no longer recognize the bacteria invaders
S pilli
secreted fragments of pilli that bind to antibody molecules and inactivate them
axial filaments
flagellum like structures that wrap around bacterial cell and give it mobility, often referred to as endoflagella
flagella
long structure that extends far beyond the cell wall, used for motility and is a classic example of the relationship between structure and function, allow bacteria to move rapidly from one location to another
structure of flagella
filament (made of flagellin), hook (links filament to basal body), basal body(rod that has rings strategically fastened to it
Monotrichous
the most common form of flagellae, in which the barcterium has one flagellum located at one end of the cell
amphitrichous
in which the bacterium has two flagella, one at end of each cell
Lophotrichous
in which the bacterium has two or more flagella located at the same end of the cell
Perltrichous
another form in which the entire cell is surrounded by flagella
Plasma membrane
selective permeability, the membrane is made of hydrophillic (outside heads) and hydrophobic (inner layer) molecules, provides barriers between inside and outside of cell
integral proteins
fully penetrate the plasma membrane and in some cases contain a pore that connects the interior of the cell to the extremal environment
Osmosis
molecules can move across cell membrae “water chases concentration”
plasmolysis
cell loses water and shrivels up, hypotonic
osmotic lysis
water enters the cell causing cell to expand and eventually lyse , hypertonic
isotonic environment
solute concentrations inside and outside the cell are essentially equal
passive transport
simple diffusion and facillitated diffusion
facilitated diffusion
molecules are brought across the plasma membrane by carrier molecules (permeases) binding of solute changes shape of protien
active transport
the carrying of solute either into or out of a cell against the concentration gradient requires expenditure of ATP and uses specific carrier proteins found in plasma membrane
Efflux pumping
proteins are part of “super family of transporters” “revolving door” mechanism in which membrane pumps bring in certain molecules and expel others at the same time
ABC transport system
molecule transported forms a complex with binding protien on the outside of the plasma membrane
group translocation
unique to bacteria, want to stay in ex) glucose is transformed using phosphotransferase enzyme to glucose-6-phosphate so it can no longer move across cell membrane
secretion
involves moving substances from the inside of the cell to the extracellular fluid. secretion involves several plasma membrane proteins that act in a specific sequence
Nuclear region
region that is most discernable supercoiled and associated with specific positively charged proteins that stabilize it
inclusion bodies
membrane enclosed organelles used to stored materials
metachromatic granules
store phosphates in inclusion bodies
physical requirements for bacteria growth
temperature, pH, osmotic pressure
psychrophiles
bacteria that grow at cold temperatures (0-15 C)
Psychotrophs
subset of psychophiles, bacteria that grow best between 20-30C
Mesophiles
bacteria that grow best at moderate temperatures, 25-40C, most common types of bacteria and human pathogens
Thermophiles
bacteria that grow only at temperatures above 45C, extreme thermophiles if above 80C
minimum growth temperature
lowest temperature at which an organism grows
optimal growth temperature
the temperature at which the highest rate of growth occurs
acidophiles
bacteria that grow at extremely low pH values
osmotic pressure
pressure exerted on bacteria by their surroundings, can affect bacterial growth
halophiles
bacteria that love being in a high salt environment. Obligate require high salt concentrations, facultative can live with or without it and extreme can grow in the presence of very high salt levels
what are the two ways bacteria obtain carbon?
the breakdown of preexisting molecules that contain carbon
atoms, which are then used for construction of new molecules. This
“recycling” process is very common in biological systems, and organisms
that use it are referred to as chemoheterotrophs. (pathogenic bacteria)
CO2 molecules,
and these organisms are referred to as chemoautotrophs.
Nitrogen
required for making bacterial amino acids and nucleic acids
Sulfur
required for making some bacterial amino acids
Phosphorous
required for making bacterial nucleic acids, membrane phospholipid bilayer, and ATP
Potassium, magnesium, calcium
required for functioning of certain bacterial enzymes
iron
required for bacterial metabolism
aerobes
bacteria that require oxygen
faculatative aerobes
can grow with or without oxygen
superoxide dimutase
convert free radical oxygen into molecular oxygen and peroxide, then uses catalase to convert hydrogen peroxide to water and oxygen
catalase
converts hydrogen peroxide to water and oxygen
aerotolerant bacteria
can grow in the presence of oxygen but do not use it in metabolism
peroxidase
convert hydrogen peroxide to water
microaerophiles
aerobic bacteria but require only low levels of oxygen for growth
Sodium thioglycolate
This medium forms an oxygen
gradient such that the farther into the medium we go, the less oxygen
there is. When bacteria with different oxygen requirements are compared
using this medium (Figure 10.6), obligate anaerobes will always grow in
the area of the tube where oxygen is absent, whereas obligate aerobes
grow only where the oxygen concentration is highest. Facultative anaerobes,
which can grow either with or without oxygen, grow throughout
the sodium thioglycolate medium even though the oxygen concentration
decreases steadily from top to bottom of the tube.
GasPak Jar
incubation jar totally devoid of oxygen, only obligate and facultative anaerobes can grow in it
fastidious bacterium
slow growing, require a large number of growth factors
chemically defined growth medium
chemical composition is precisely known
Complex media
complex media contain not
only numerous ingredients of known chemical composition but also
digested proteins and extracts derived from plants or meat. Such media
are referred to as complex because the exact chemical composition of
these digests and extracts is not known.
nutrient broth vs solid
both complex media, broth in liquid form, solid is media with agar added
selective media
one that contains ingrediants that prohibit the growth of some organisms while fostering the growth of others
differential medium
contains ingredients that can differentiate between organisms
MacConkey medium
culture and differentiation of bacteria based on their ability to ferment lactose, lactose fermenters form red to pink colonies, non fermenters form colorless or transparent colonies
Eosin methylene blue (EMB) agar
isolation, culture, and differentiation of gram-negative bacteria. Lactose fermenting bacteria form green metallic sheen, non fermenting bacteria form colorless or light purple colonies
Triple sugar Iron agar
Differentiation of
Gram-negative
bacteria on the basis
of their fermentation
of glucose, sucrose,
and lactose and on
their production of
H2S gas
Red slant/red butt, no
fermentation; yellow slant/
red butt, glucose fermentation;
yellow slant/yellow butt, glucose
and lactose fermentation; butt
turns black, H2S produced
Blood agar
Culture of fastidious
bacteria and
differentiation of
hemolytic bacteria
Partial digestion of blood, alpha
hemolysis; complete digestion
of blood, beta hemolysis; no
digestion of blood, gamma
hemolysis
Mannitol Salt agar (MSA)
selective/differential medium that is useful for identifying Gram-positive organisms. Uses high salt concentration to select for Staphylococcus species while inhibiting
the growth of other bacteria. In addition to this selection, the mannitol
sugar in MSA permits differentiation between species of Staphylococcus.
Generation time
time interval between divisions of bacteria (bacteria divide using binary fission)
lag phase
stage of bacterial growth the bacteria are adjusting to their environment
and may have to synthesize enzymes to utilize the nutrients available
in the environment. In this phase, little if any binary fission occurs, indicated
by the fact that the growth curve is horizontal
Log phase
the number of bacteria doubles and increases exponentially and will have reached the constant
minimum generation time. This level of growth can be sustained only
while environmental conditions remain favorable and, more importantly,
only if an adequate supply of nutrients remains available
Stationary phase of ggrowth
the phase in which
the number of cells dying is essentially equal to the number being produced
through cell division. This phase is relatively short because it is
predicated on the availability of nutrients, which continue to disappear
as the growth curve shifts to the last phase.
death phase
represents
a continuous decline in the number of dividing cells. This decline
is caused by exhaustion of the nutrient supply as well as collapse of the
environment due to the build-up of toxic waste materials
DNA structure
deoxyribonucleic acid, double stranded helical model made of nucleotides (phosphate and sugar with deoxyribose backbone), antiparallel (3’->5’ and reverse)
purines
adenine and guanin, large double ring structures
pyrimidines
thymine and cytosine, single ring structures
DNA pairings
adenine with thymine and cytosine with guanine (AT Genetics Class)
structure of RNA
RNA contains the sugar ribose rather than deoxyribose.
* The bases in RNA are adenine, cytosine, guanine, and uracil, and
the base pairings are adenine with uracil, cytosine with guanine.
* RNA is usually found in a single-stranded form. However, RNA can
fold on itself and form areas that are in a double-stranded form (see
the discussion below).
messenger RNA
containing information derived from DNA that is used for construction of proteins
Transfer RNA
carries amino acids to the ribosome where protein is being constructed
ribosomal rna rRNA
helps in maintaining the proper shape of the ribosome and the orientation of the protein under construction
Supercoiling
helix twists around itself, before strands can be unwound and separated for replication and transcription, topoisomerase does unwinding
helicase
once enzyme is relaxed from supercoiling by topoisomerase, helicase unwinds and separates the chains
Primer:template junction
Once the double-stranded DNA has
been unwound, each unwound single DNA strand is called a template.
A portion of this template is then paired with a short segment of RNA
called a primer.
gives the DNA polymerase a place to which the next base can be attached
DNA polymerase
enzyme, uses primer:junction as a guide and then takes any of the bases and binds them, can bind many bases at onetime, proofreads
exonuclease
enzymes that attack the open ends of molecules, proofread on growing end of 3’, strongly attracted to bases that are improperly added and degrades them
replication fork
where in DNA double helix replication is occuring, and the double helix is being unwound and the strands are being separated from eachother,
leading strand
the 3’ DNA strand which has an addition onto it’s 3’ end polymerase can add bases and moves towards the fork
lagging strand
the 5’ DNA strand which is moving away from the fork, necessitates replicating the lagging strand in pieces AKA Okazaki fragments
primase
can synthesize RNA without a 3’ end being present (this synthesis can occur at any place along the DNA sequence). As the replication fork moves, the lagging strand of DNA elongates, and a primase molecule attaches to the strand and synthesizes a small piece of
RNA. This RNA becomes the primer part of the primer:template junction.
DNA ligase
the ends of DNA pieces are linked together after RNAaseH removes primer
RNAaseH
enzyme that removes the primer RNA the dap that results from the missing primer is filled by DNA polymerase