Studied by 2 people
Looks like no one added any tags here yet for you.
what are prokaryotes
made of prokaryotic cells
all unicellular
what defines prokaryotic cells
no nucleus no membrane bound organelles
how do prokaryotes reproduce
binary fission
what are the taxonomy of prokaryotes
domain: Bacteria and Archaea
kingdom: Bacteria and Archaea
what is a species
a group of organisms that can interbreed and have fertile offspring
why does the original species definition not work for prokaryotes?
prokaryotes breed by binary fission-asexually
how do we classify prokaryotes
based on similarities in appearance physiology and genes
what are subspecies strain or type
some species but have differing characteristics
what is a serotype
same species but stimulate a different immune response
what is a cell envelope
outer covering of cell
surrounds the cell
what are parts of prokaryotes
structures inside and outside of cell
what are the virulence factors for prokaryotes
increase ability to cause disease
secretion system
LPS
outer membrane
acid fast
glycocalyx
plasmids
bacterial endospores
what are the layers of the cell membrane
cell membrane and cell wall (peptidoglycan (PTG)
and outer membrane
what is the cell membrane
also called plasma membrane or cytoplasmic membrane
just outside the cytoplasm
denies the boundary
all cells have this
what is the cell membrane made of
two opposing leaflets of phospholipids (phospholipid bilayer)
is embedded with numerous proteins
what does a phospholipid bilayer contain
a hydrophilic head and hydrophobic tail
what is a cell wall
surrounds the cell membrane
what is the cell wall made of
peptidoglycan in most bacteria ~90%
outer membrane in some bacteria ~40%
what does the cell membrane distinguish
gram positive and gram negative
what does gram positive show
plasma membrane
large peptidoglycan area
protein
what does gram negative show
plasma membrane
protein
small peptidoglycan area
have an outer membrane
what is peptidoglycan (PTG)
chemical found only in bacteria
gives cell structural rigidity and shape
major target of antibodies
very important for target antibiotics
what is peptidoglycan made of
long sugar chains (glycan) connected by protein chains (peptide)
how are glycan chains held together
by peptide bridge (gives structure)
what is the outer membrane of PTGwhat
similar to cell membrane
outer leaflet of bilayer is made of lipopolysaccharides (LPS)
what can large amounts of LPS in the bloodstream mean
can result in death
what is LPS also called
endotoxin
what is LPS made of
polysaccharide that functions as a receptor
specific sequence helps us identify serotypes (o antigens)
ex) e coli
what is lipid a of LPS
the toxic part
what is the core of LPS
connector
what is the outer membrane in LPS
it protects bacteria from host immune system
very impermeable (prevents almost anything from going through)
how do small molecules cross outer membrane in LPS
facilitated diffusion
other substances may require secretion systems
what is the secretion system
protein complexes embedded within membranes to transport virulence factors (such as toxins) out of the cell
different types based on structure and function (can travel across one membrane or many)
who is Hands Christian Gram
found that different types of cells would retain the dye differently in his staining method
what is a gram stain
divide bacteria into two major categories based on the fundamental differences in cell walls
what is the key test in identification of bacterial species
purple- gram positive
pink-gram negative
what is the cell membrane of a gram positive envelope
small periplasmic space between the membrane and PTG
what is the peptidoglycan on a gram positive envelope
thick, many sheets (30-50)
permeable to numerous substances
has teichoic acid/lipoteichoic acid
what do teichoic acid/lipoteichoic acid do
link envelope together
what is the gram negative envelope summary
cell membrane
periplasmic space- thin layer of PTG (2-5)
outer membrane- outer leaflet made of LPS not permeable
what is a primary stain
crystal violet (basic)
what is a mordant stain
iodine (complexes)
what is decolorization/destaining
ace tone/alcohol/water
gram positive stains
fixation-clear
crystal violet-blue
iodine treatment-purple
decolorization- purple
counter stain w/ safranin-purple
gram negative stains
fixation-clear
Crystal violet-blue
iodine treatment-purple
decolorization-clear
counter stain w/ safranin- pink
what are cell wall expections
some bacteria have extra layers to their cell wall
acid fast bacteria have waxy lipid layer attached to cell wall made of mycolicacid
acid fast bacteria
technically gram positive cells but do not retain the gram stain
resists treatments with chemicals and dyes
what is acid fast stain- differential
use heat on organisms that do not readily take up dyes
what do some bacteria naturally lack
cell wall
what causes walking pneumonia mild pneumonia?
mycoplasma
what are structures outside of the cell
glycocalyx ( extracellular matrix, simple layer, capsule)
appendages (flagella, frimbrae, pili)
what is glycocalyx
viscous and gelatinous
made of carbohydrates and/ or protein
protect the cell from drying out and/ or host immune system
sometimes helps the cell adhere to the environment
differ among bacteria in thickness/organization and chemical composition
what are the two types of glycocalyx
slime layer (s layer)
capsule
what is the slime layer
loose Shiel that protects some bacteria from loss of water and nutrients
(diffuse and irregular)
what is a capsule
count more tightly to the cell and is denser and thicker
is a virulence factor
protect the bacteria against immune system
important in the formation of biofilms
what are biofilms
mixed communities of different species of microbes
free living planktonic bacteria attach to a surface
other microbes attach to the pioneer and begin secreting capsule that covers entire colony
parts can break away and infect other places
removal is extremely difficult
resists immune response, heat, chemical, mechanical remover
where are biofilms naturally found in the body
dental plaque
where can biofilms be found
in sewage treatment systems; can clog pipes
what are biofilms involved in
70% of infections of catheters, intrauterine devices, pacemakers, heart valves, contact lenses, etc
what is a capsule stain
a gelatinous covering that do not accept most dyes
consist of two dyes ( acidic and basic)
appears as a halo around the cell
what step is missing compared to a normal smear and stain?why?
we never fix (put under heat)
can’t get hot so capsule will stain
what are appendages
some bacteria have external appendages
not essential of life but aid in survival in certain environments
3 types
flagella
fimbriae
pili
what is flagella
filamentous appendages external of the cell
responsible for motility (movement)
use propeller like movements to push bacteria
three basic parts
filament-extend to exterior; made of proteins called flagellin; also called H antigen(distinguish among serotypes (ex. e coli))
hook- connects filament to basal body
basal body-anchors flagellum into cell wall
what is monotrichous
single flagellum at one pole
what is lophotrikhous
tuft of flagella at one end
what is amphitrichous
flagella at both poles
what is peritrichous
flagella all over
what is chemotaxis
bacteria sense chemicals and move accordingly
nutrients may attract, toxins may repel
bacterial movement is series of Rons (straight line) and tumbles (change in direction)
what is aerotaxis
movement bc of oxygen
what is magnetoraxis
movement bc of magnetic field
what is thermotaxis
movement because of temperature
what is phototaxis
movement bc of light
what can be used as a diagnostic tool
motility and the presence of flagella
how do you observe motility
wet mount
movement in agar-agar stab
what is a flagella stain
coats the flagella to thicken appearance, making them visible under a light microscope
what are axial filaments
also called endoflagella
found in spirochetes
wrapped around entire cell
rotation causes cell to move like a corkskrew
what are other appendages
frimbriae- velcro; small bristle like protein fibers; tend to stick to each other and to surfaces
sex pili- elongated rigid tubular structures; made of protein pillion; used in conjugation
what are the internal structures of bacteria suspended in
cytosol-gelatinous solution;70-80% water; site for most biochemical. and synthetic activities
what is the entire interior of the cell referred as
cytoplasm
prokaryotic dna
usually circular
main chromosome is required and has all the genes needed for life
the main chromosome is located in a dense gel like region-nucleoid
replicants during binary fission
nonessential and optional but often confer protective traits such as drug resistance or the production of toxins and enzymes
few to several hundred genes (~5% size of the chromosome)
independently replicating
what are plasmids
prokaryotes small circular pieces of DNA that exist independently of the chromosome
what is vertical gene transfer
plasmids are passed down to the next generation of cells
this is a normal part of cell division
what is horizontal gene transfer
plasmids are transferred to existing cells in the same generation
3 ways of occurring-
transformation transduction conjugation
steps for conjugation-sex pili
1)donor cell attaches to a recipient cell with its pilus. the pilus draws the cells together (tube that connects)
2)the cells contact one another
3)one strand of plasmid DNA transfers to the recipient
4)the recipient synthesizes a complementary strand to become an f+ cell; the donor synthesizes a complementary strand restoring its complete plasmid
what are ribosomes
responsible for translation (protein synthesis)
made of RNA and protein 50/50
prokaryotic ribosomes are 70s
-small subunit 30s
-large subunit 50s
-suedburg: how things sink or rise
what are inclusion bodies
vary in size number and content
-gas vacuoles maintain buoyancy
-storage sites for nutrients during periods of abundance that serve as storehouse when nutrients become depleted
-sulfur, lipids, polysaccharides
what is prokaryotic cytoskeleton
inferior protein framework
contributes to cell shape and likely involved in cell division
similar to the cytoskeletal filaments of eukaryotes
what are bacterial endospores
found virtually anywhere
protective
-may remain dormant for 100 years or longer
-extremely resistant to heat, desiccation, chemicals, UV light, and boiling water
produced only 3 genera
some diseases are related to the persistence and resistance of their spores
-bacillus anthraces: anthrax
-clostridioides difficile: pseudomembranous colitis (c. diff)
-clostridium tentani: tetanus (lockjaw)
c. perfringens: gas exchange
c. botulinum: botulism
what is the medical significance of endospores
are constant with intruders where sterility and cleanliness are important
-resist ordinary cleaning methods: boiling water soaps and disinfectant
-frequently contaminate cultures and media
-hospitals must protect against endospores in wounds
-destruction of endospores is important in the food canning industry
what are the steps for endospore formation
vegetative cell
metabolically active and growing
conditions are favorable for growth
sporulation
process of vegetative cell converting to an endospore
caused by unfavorable conditions
process takes about 8 hours
free endospore
hardiest of all life forms
many layers protect DNA
excludes molecules and maintains dehydrated state protects from heat
germination
spore turns back into vegetative cell
occurs in the presence of warmth water and a specific germination agent (ex: amino acid or salt)
quite rapid (1.5 hours)
what is a endospore stain
spores are resistant to staining
use heat to force color inside
what is archaea
the most primitive of all life forms
most closely related to cells that originated 4 billion years ago
what are extremophiles
live in habitats that are similar to the extremes found anciently- heat, salt, acid, pH, pressure, and atmosphere
what are methanogens
convert carbon dioxide and hydrogen gas into methane
-common in habitats of anaerobic swamp mud, bottom sediments of lakes and oceans and the digestive systems of animals
what are halophiles
live in 36% NaCl that would destroy most cells
-exist in inland seas, salt lakes, salt mines, and in salted fish
what are hyperthermophiles
grow at very high temperature
-live in volcanic waters and soils and submarine vents
-often salt and acid tolerant as well as heat tolerant
what did archaea used to be considered
a type of bacteria
-early bacteriologist classified according to shape arrangement growth characteristics and habitat
what is evolutionary relatedness
the most accurately determined through comparison of nitrogen bases in ribosomal RNA
-tend to remain stable over long periods
-any major differences in the signature sequence indicates distance in ancestry
what domain are archaea more related to
eukarya
share ribosomal rna sequences not found in bacteria
what is the difference of archaea from other cell types
unique method of DNA compaction
unique membrane lipids cell wall composition and pillion proteins
Note
Flashcard