Module 2.1- Bacterial Morphology and Cytology Flashcards
The general shape of individual bacterium is usually discernible with:
light microscope
revealed distinct anatomical features of bacteria
electron microscope (1950s)
range of bacteria diameter
0.2 - 2.0 micrometers
range of length of bacteria
2-8 micrometers
three basic shapes of bacteria
> cocci
bacilli
spiral
usually spherical-shaped bacteria but can be oval, elongated or flattened on one side
cocci (clue: berries)
cocci may remain attached in groups due to
incomplete separation of cell during division
cocci that remain in pairs after division of a bacterial cell in one plane
Diplococci
cocci in chain-like patterns following division in one plane
Streptococci
cocci in groups of four resulting from division of bacterial cell in two planes
tetrads
cocci in cube-like groups of eight produced when bacterial cell divides in three planes
Sarcinae
cocci in grapelike clusters that form when bacterial cell divides in multiple planes
Staphylococci (clue: staphyle, bunch of grapes)
cocci in grapelike clusters that form when bacterial cell divides in multiple planes
Staphylococci (clue: staphyle, bunch of grapes)
rod-shaped and characteristically long and slender
Bacilli (clue: meaning little staffs)
bacilli that are oval and look so much like cocci
coccobacilli
difference between coccobacilli and cocci
Bacilli divide only across their short axis
most common type of bacilli
single rods
bacilli that appear in pairs after division
Diplobacilli
bacilli that occur in chains
streptobacilli
bacilli that are arranged in angular patterns that look like X, Y, V, and L” configuration
Cuneiforms (clue: looks like Chinese letters)
how cuneiforms form
bending of the bacterial cell at the point of division
example of cuneiform bacteria
Corynebacterium diphtheriae
bacilli in “picket fence” or cigar packet arrangement (side by side)
Palisades
how palisades form
slipping (sliding) of the bacterial cells during division
bacteria that have one or more twists; they are never straight.
spirals
spirals that look like rods curved into a form resembling a comma.
vibrios
spirals that have helical (i.e., coiling) shape, like corkscrews and have fairly rigid bodies
spirilla
spirals that are helical and flexible
spirochetes
most bacteria belong to this where they maintain a single shape
monomorphic (mono, one; morph, form)
bacteria which can have many shapes, not just one
pleomorphic (pleo, many; morph, form),
three (3) architectural regions of a bacterial cell
> cell envelope
appendages
cytoplasmic region
structure that encloses the cytoplasm of the cells, essentially the protective unit
cell envelope
three layers of the cell envelope (stratified structure)
> cell membrane
cell wall
glycocalyx
all cells have this part of the cell envelope
cell membrane
almost all bacteria have this part of the cell envelope
cell wall
only some bacteria have this part of the cell envelope
glycocalyx
thin, delicate membrane surrounding the cytoplasm and separating it from the environment.
cell membrane
two structural components of the cell membrane
> phospholipid bilayer (40%)
> proteins (60%)
two components of the phospholipid bilayer
> polar, hydrophilic glycerol head outside
> two non-polar hydrophobic fatty acid tails inward
The arrangement of the lipids and proteins to form a membrane is called the
fluid mosaic model
component that is found in eukaryotic cell membrane but not in bacterial cell membrane
sterols
only bacteria which have sterols to protect from osmotic lysis beacuse they do not have cell wall
genus Mycoplasma
Functions of the cell membrane
- selective permeability
- site of transport system
- site for biosynthesis
- specialized enzyme system
- chemotaxis
- participates in reproduction
- site of antibiotic action
The most important function of the plasma membrane
serve as a selective barrier
the property of the cell membrane that allow certain molecules to move through the membrane while restricting others
Semipermeability
uncharged molecules with molecular weights of about 100 Daltons which pass through the bacterial cell membrane freely
water
he free movement of water through the cell membrane from a region of lower solute concentration to a region of higher solute concentration
osmosis
Medium where the concentration of solutes is the same inside and outside of the cell. There is no net gain or loss of water, so the
cell will retain its original shape
isotonic medium
Medium where the solute concentration outside of the cell is lower than in the inside of the cell, and water enters the cell.
hypotonic medium
Limits a bacterium’s accumulation of water.
non expendable cell wall
The escape of the cytoplasm from cells without rigid cell walls when it ruptures due to high pressure
plasmoptysis
medium where the solute concentration is higher outside of the cell, and water leaves the cell.
hypertonic medium
Hypertonic medium causes the cell membrane and cytoplasm to shrink away from the cell wall. This is known as:
plasmolysis
cytoplasm rupture is referred to as
plasmoptysis
cytoplasm shrinking is referred to as
plasmolysis
Membrane proteins that mediate the passage of solutes through the cell membrane
carrier proteins or permeases
Because carrier proteins mediate solute passge, transport systems are therefore:
carrier-mediated
show specificity for solute
Three types of transport systems among bacteria
> facilitated diffusion
active transport
group translocation
The least common type of transport system in bacteria (e.g., glycerol uniporter in E. coli)
Facilitated diffusion
Used for transport of most solutes like amino acids, ions, and sugars
active transport
Used for accumulation of many ions, amino acids, or sugars into the bacterium
Active transport
Transports at a rate faster that diffusion alone
active transport
Used primarily for transport of sugars
(e.g., glucose specifically enters the channel from outside. but to enter the cytoplasm, it must be sequentially converted into pyruvic acid, which is the key metabolic intermediate, then bacteria process the pyruvic acid using a variety of fermentation pathways.)
group translocation
Is solute modified during facilitated diffusion?
No
Is solute modified during active transport?
No
Is solute modified during group translocation?
Yes
Does facilitated diffusio have energy expenditure?
No
Does active transport have energy expenditure?
Yes
Does group translocation have energy expenditure?
Yes
Does Facilitated Diffusion move against concentration gradient?
No
Does Active transport move against concentration gradient?
Yes
Does Group translocation move against concentration gradient?
Yes
Function that where the cell membrane allows for production of components that make up the bacterial cell wall and appendages.
Site for biosynthesis
Funnction of the cell membrane where it contains enzymes involved in many metabolic processes such as cell wall synthesis, membrane synthesis and DNA replication.
Specialized enzyme system
Bacterial ability to move/swim in response to environmental stimuli which is facilitated by their cell membrane
chemotaxis
Component of the bacterial cell membrane which determines the quality and quantity of certain chemicals in the environment
sensing protein
Bacterial cell swimming towards useful nutrients
positive chemotaxis
Bacterial cell swimming away from harmful substances
negative chemotaxis
Other types of tactic responses in bacteria which provides the evidence for the ecological advantage (survival) in bacteria.
phototaxis (towards light source)
aerotaxis (towards oxygen)
magnetotaxis (in response to Earth’s magnetic field)
reproduction of bacteria
binary fission
cytoplasmic invaginations of the cell membrane in the form of stacks or vesicles which coordinates DNA replication and segregation with septum formation
mesosomes
another function of mesosome
significantly increase the membrane surface area without increasing the cell size, allowing the cell greater activity for respiration and active transport.
What does mesosome do during cell division?
- attaches the DNA where it is replicated
- draws the 2 DNA molecules in opposite direction while the septum is formed between 2 chromosomal components
- 2 progeny cells form after septum formation
A type of antibiotic that pokes holes in the lipid bilayer
Polymyxin
chemical agents that dissolve the lipid bilayer resulting in leaking out of the cytoplasmic contents
alcohol and some detergents
how the cell dies when cytoplasmic contents are leaked
lysis
The rigid layer surrounding the cell membrane in most bacteria.
Cell wall
The strength of cell wall is primarily due to this substance which can only be found in bacteria
peptidoglycan
Other terms for peptidoglycan
murein or mucopeptide
The peptidoglycan is composed of:
Carbohydrate (CHO) backbone & peptide chains
The carbohydrate backbone of peptidoglycan is a polymer of disaccharides consisting of alternating units of
- N-acetylmuramic acid (NAM)
2. N-acetylglucosamine (NAG)
The peptide chain of peptidoglycan is composed of ________ and hence is called __________
4 amino acids
tetrapeptide
The peptide chain of peptidoglycan is attached to the:
N-acetylmuramic acid (NAM)
A single layer of peptidoglycan is a network of adjacent sugar chains bound together through the:
peptide chains
The peptidoglycan is a _________ structure
cross-linked
The part of the cell that determines gram staining
cell wall
A gram-positive cell wall is made up of:
> several layers of peptidoglycan
> Techoic acid (TA)
a gram negative cell wall is made up of:
> single layer of peptidoglycan
outer membrane
periplasm
Peptidoglycan of gram-positive cell wall vs. gram negative cell wall
gram+ 20-80 nm, 60-100% of cell wall
gram - 10 nm, 10-20% of cell wall
Backbones that are extensively cross-linked through the
tetrapeptide chains by
amino acid bridges
Interpeptide bridge;
pentaglycine
component of gram positive cell wall that are polymers of ribitol phosphate and glycerol
phosphate.
Teichoic acid (TA)
2 Types of Cell wall teichoic acid
membrane teichoic acid
wall teichoic acid.
Techoic acid that is anchored to the cell membrane lipids
Membrane TA
Since Membrane TA are anchored to the cell membrane lipids, they can also be called:
lipoteichoic acid (LTA)
Techoic acid that is covalently linked to the NAM of the cell wall.
Wall TA
Function of Techoic Acid
Major surface antigens of the gram-positive cell wall which stimulate host immune system to make antibodies.
The tetrapeptide chain link in gram negative peptidoglycan
interpeptide bond between amino acids of adjacent backbones
Which is more fragile? gram negative or gram positive? why?
gram-negative cell wall because of less peptidoglycan layers
Surrounds the peptidoglycan layer of a gram negative cell
Outer membrane
two functions of the outer membrane (OM) to a gram negative cell
> major permeability barrier to hydrophobic molecules
> protection from antipeptidoglycan chemicals such as lysozyme or the antibiotic penicillin.
Characteristic of gram negative outer membrane
similar to phospholipid bilayer but contains specialized polysaccharides and proteins
The inner leaflet of the outer membrane consists of:
phospholipids and proteins
two proteins found in the inner leaflet of the outer membrane
Braun lipoproteins
Porin proteins
protein in the inner leaflet that anchors the OM with
the underlying peptidoglycan, thus
stabilizing the cell wall.
Braun lipoproteins
protein in the inner leaflet that completely spans the outer membrane and form pores of fixed diameter which act as transmembrane allowing hydrophilic molecules to pass
Porin proteins
clue: pore
The outer leaflet of the OM contains
> phospholipids
> mainly Lipopolysaccharides (LPS)
LPS in the outer leaflet of the OM is made up of:
> Lipid A
> Outer polysaccharide
Lipid A in the outer leaflet of the OM is commonly referred to as:
endotoxin
(endo- within the cell wall
toxin- toxic to host)
When gram negative bacterium is destroyed within the human body, it is released from the cell wall. It elicits toxic reaction in the host, such as:
fever (pyrogenic)
shock (hypotension)
disseminated intravascular coagulation (DIC)
hemorrhage.
It is composed of repeating sugar units and extends outward from lipid A. These are the outermost molecules of the cell wall.
Outer polysaccharide
Outer polysaccharide is also known as:
somatic antigen O antigen (O stands for Ohne hauch in German "without breath")
function of O antigen/ outer polysaccharide
constitutes the major surface antigen that accounts for serotype or serovar (classification based on surface antigen) among gram negative bacteria
The space between the OM and the inner cell membrane (cell membrane) in a gram negative cell wall
Periplasm
Function of periplasm
stores enzymes for biosynthesis > for peptidoglycan assembly (transglycosylases, carboxypeptidases, and transpeptidases) > degradative enzymes (phosphatases, proteases) > detoxifying enzymes (beta-lactamase, penicillinase) > Binding proteins (for amino acids, sugars, vitamins or ions)
Functions of the Cell Wall
> rigidity and shape > protection from osmotic lysis > Gram’s stain reaction > contributes to pathogenicity > Site of antigenic determinants > Barrier from certain antibiotics
The cell wall gives rigidity and shape to the cell by acting as a
exoskeleton
Gram-positive bacteria stains color _____ by ______
violet, crystal violet
Gram-negative bacteria stains color _____ by ______
red/ink, safranin
How does cell wall affect gram staining?
Thicker peptidoglycan traps crystal violet more extensively so it cannot be decolorized by alcohol.
Alcohol dissolves lipid in OM of gram negative bacteria so it decolorizes easily.
Component of gram negative cell wall that elicits elicits certain toxic symptoms of diseases
Lipid A
Surface antigens of bacteria
Techoic acid (TA) in gram positive O antigen (outer polysaccharide) in gram negative
target site of action of antibiotics
peptidoglycan
a lytic enzyme naturally present in human tears, saliva, sweat, and other body fluids
lysozyme
Two (2) groups of bacteria that do not have cell walls or have very little cell wall material.
Mycoplasma species (naturally-occuring wall-less bacteria)
L-forms (wall-less variants of normal cells arising from mutation or from physical or chemical agents)
two types of L-form bacteria
a. protoplast (created from gram-positive)
b. spheroplast (created from gram negative but still has OM)
A gelatinous layer external to the cell wall found in some bacteria
glycocalyx
The glycocalyx can be in the for of either:
> capsule
> slime layer
glycocalyx that is thick, organized, firmly attached to the cell wall (not easily removed) and is clearly differentiated from the environment
Capsule
The chemical composition of the capsule is genetically determined, but most capsules consist of
polysaccharide
The chemical composition of Bacillus anthracis capsule
polypeptide
glycocalyx that is unorganized, loosely attached to the cell wall, and diffuse into the medium.
slime layer
the slime layer usually contains a mass of tangled fibers of a polysaccharide called:
dextran
glycocalyx functions
> protection from dehydration > Retards phagocytosis > Attachment to surfaces > Site of antigenic determinant > Antibiotic barrier. > Component of vaccines
The glycocalyx can protect the bacteria from desiccation (drying out) due to its:
high water content
Capsules increase pathogenicity because it protects against white blood cells called _______
phagocytes
Scientists believe that the repulsion between bacterial cell and phagocytes is because
capsule and phagocyte surface both have strongly negative charge
Glycocalyx function that is crucial in the development of disease.
attachment to cells
Serologic typing of bacterial capsules can be done through identification of
K-antigen
clue: K for kapsel - german
It is an impenetrable barrier to most common sites of antibiotic action
glycocalyx
3 types of cell appendages
> flagellum
pili and fimbriae
axial filament
A cell appendage which is long, thin, thread-like or whip-like, filamentous appendage that arise from the cytoplasmic membrane and extend into the medium.
flagellum
Protein building block of flagellum
flagellin
Three basic parts of a flagellum
> Filament
Basal body
Hook
the outermost whip-like structure of the flagellum
Filament
The part of the flagellum that is embedded in the cell membrane which acts as an anchor to the cell membrane and motor to turn the filament like a propeller.
Basal body
Part of the filament that acts like a universal joint between the filament and basal body.
Hook
four basic types of flagellar arrangement on bacteria:
Peritrichous
Lophotrichous
Amphitrichous
Monotrichous
flagellar arrangement where there is flagella all over the surface
Peritrichous
clue: Peri = periphery of surface
flagellar arrangement where there is a tuft of flagella at one end
Lophotrichous
flagellar arrangement where there is one or more flagella at each end
Amphitrichous
amphi - two or both ends
flagellar arrangement where there is one flagellum located at one end
Monotrichous
mono- one
Bacteria without flagella are called
atrichous.
two functions of the flagellum
> confers motility
> Site of antigenic determinant
bacterial movement towards a favorable environment/stimulus, or away from an adverse one.
taxis
When the bacterium moves in one direction for a length of time, the movement is called a
“run” or “swim”
“run” or “swim” movements is achieved when the flagella rotates in what direction
counterclockwise.
Runs are interrupted by random, abrupt change in direction which are called
“tumbles”
“tumbles” are achieved when the flagella rotates _____
clockwise
flagella antigens are termed
H antigens
(H is for hauch which means “breath” in German. The movement of motile bacteria in agar medium spreads the same way as breath on glass)
H antigen are:
> heat labile
> proteins (flagellin)
Elongate, rigid tubular structures that extend from the cell, which are straighter and shorter than flagella. This can only be observed by electron microscopy
Pili (meaning hair)
special protein constituting a pili
pilin
There are only about _____ pili in a cell, which are _____ in diameter
1-10
9-10 nm
pili that allows for attachment of the cell to surfaces thereby acting as a determinant of pathogenicity
common pili
pili that facilitates conjugation
sex pili
The process of transfer of genetic material (DNA) from a donor bacterium to a recipient bacterium. It confers new characteristics and functions.
Conjugation
similar to the pili but smaller and more numerous.
fimbriae
Bacterial fimbriae are chiefly composed of what protein
fimbrillin
It acts as a scaffolding on the surface of cells onto which specific adhesive molecules are
attached.
fimbriae
consists of bundles of fibrils that arise and extend from one or both poles of the cell but fold back so that it is spirally wound/wrapped along the cell body.
axial filament
Axial filament is found between
cell wall and the cell membrane
other term for axial filament
endoflagellum
endo-inside, flagellum-like function
function of axial filament
responsible for the motility of
spirochetes in a spiral motion (like corkscrew)
gram-negative, coiled bacteria
spirochetes,
refers to the internal matrix of the cell contained inside the cell membrane
cytoplasm
The chemical characteristics of the the cytoplasm
80% water
three differences of prokaryotic from eukaryotic cytoplasm
- no membrane bound organelles (ER, golgi, mitochondria, lysosome)
- no cytoskeleton (microfilament, microtubule)
- no cytoplasmic streaming (movement of cytoplasm)
5 constituents of the cytoplasmic region
- nucleoid
- plasmid
- ribosomes
- inclusions
- endospores
The region of the chromosome in a
bacterial cell
nucleoid
Structure of the nucleoid
> long, single, circular
double stranded DNA
no histones
no membrane
Function of the nucleoid
genetic storehouse of the bacterium
DNA molecule in bacteria that is physically separate from the chromosomal DNA within the cell.
Plasmid
Structure of the plasmid:
> small circular
double-stranded DNA molecule
capable of replicating autonomously within a suitable host
two states of plasmid
“free” state (separate from bacterial chromosome)
“integrated” state (incorporated into the bacterial chromosome)
plasmid is considered a:
replicon (region of DNA that is independently replicated)
Function of the plasmid:
carry genes for additional genetic traits that are are not essential for cell viability.
plasmid which contain genes which
codes for expression of sex pili
F plasmids (fertility plasmids)
plasmid which contain genes that provide resistance against antibiotics or poisons.
R plasmids (resistance) (previously r-factors)
plasmid which contain genes that code for secretion of bacteriocins (proteins that can kill other bacteria)
Bacteriocinogenic plasmids,
plasmids which enable the digestion of unusual substances (like toluene and salicylic acid)
Degradative plasmids,
plasmids which turn the bacterium into a pathogen.
Virulence plasmids
Small, spherical structure distributed throughout the cytoplasm, and occupy most of the cytoplasmic volume.
Ribosomes
Constituent of ribosomes
40% proteins
60% ribosomal RNA (rRNA)
Subunits of bacterial ribosome
70S ribosome
30S
50S
Functions of the ribosome
Sites of protein synthesis
Site of antibiotic action
How does ribosome contribute to antibiotic action?
they attach to either the 30s or 50s subunit and interfere with protein synthesis.
Antibiotics that attach to the 30S subunit
streptomycin and gentamicin
Antibiotics that attach to the 50S subunit
erythromycin and chloramphenicol
Reserve deposits of nutrient materials within the cytoplasm of bacteria.
inclusions, (inclusion granules or inclusion bodies)
two types of inclusions
Organic inclusions
Inorganic inclusions
reserves of carbon and serve as energy sources
Organic inclusions
storage of glycogen and starch (polyglucose)
Polysaccharide inclusions
represents storage form of lipid and
fatty acid
Poly-β-hydroxybuterate (PBH)
inclusions found in certain bacterial pathogens that are referred to as metachromatic granules because they take up a color different from the color of the dye used.
Polyphosphates
stains red and purple in methylene blue dye
inclusions found in photosynthetic
bacteria
Sulfur deposits
Metachromatic granules in Corynebacterium diphtheriae
Babes-Ernst granules.
spherical or ovoidal, metabolically dormant structure formed by vegetative bacterial cell when essential nutrients in their environment become depleted.
endospore.
term for vegetative bacterial cell
sporangium
Four structural components of an endospore
- Core
- Cortex
- Spore coat
- Exosporium
the innermost membrane or wall of the
endospore.
Core or spore protoplast
the endospore core contains:
> entire bacterial chromosome
some ribosomes
other soluble cytoplasmic materials as energy source
the thickest layer of the spore envelope.
Cortex
the cortex contains
peptidoglycan with fewer cross-linkages
composed of a keratin-like protein
containing many intramolecular disulfide bonds making it hydrophobic and impermeable
Spore coat
confers to spores relative resistance to antibacterial chemical agents
Spore coat
the thin and delicate outermost layer of the endospore.
Exosporium (clue: exo-outside)
most resistant of all life forms, capable of withstanding extremes in heat, drying, freezing, radiation, and chemicals that would readily kill vegetative cells.
Endospores
heat resistance of endospores is linked to their:
high calcium dipicolinate content
removes water bc thermal inactivation of cells require water
confers endospores protection against radiation and chemicals
cortex
The endospore does not
assimilate materials from the environment. it is
metabolically inactive
term for spore formation
sporulation or sporogenesis
stimulus for sporulation
depletion of nutrients
The process of sporulation
basahin niyona lang sa module hehe
An endospore returns to its vegetative state by a process called
germination
One vegetative cell forms a single endospore, which remains one cell after germination. Therefore, _____
sporulation is not a means of reproduction
The majority of spore-formers belong to what group of bacteria?
rod-shaped bacteria
members of the genera Clostridium and Bacillus
