LESSON 7: BACTERIAL MORPHOLOGY AND FINE STRUCTURE Flashcards
The size of most bacteria ranges from 0.2 μm (micrometer) to 2.0 μm
in diameter and from 2.0 μm to 8.0 μm. Bacteria come
usually ound but can either be oval, elongated, spherical or elliptical shape. Either they may remain as a single cell or
may aggregate together for various configurations
Cocci
Cocci :
a. Monococcus:
b. Diplococcus:
c. Streptococcus:
d. Tetracoccus:
e. Staphylococcus:
f. Sarcina:
: represented by single, discrete round cell.
Monococcus
: the cell of the divides but the cells remain
attached to each other.
Diplococcus
: here the cells divide repeatedly in one plane to form chain
of cells.
Streptococcus
: this consists of four round cells, which divide in two planes at
right angles to one another and remain in group of four.
Tetracoccus
: here the cells divided into three planes forming a
structured like bunches of grapes giving and irregular configuration.
Staphylococcus
: here the cells divided into three planes forming a
structured like bunches of grapes giving and irregular configuration.
Staphylococcus
: these cells divide in three planes but they form a cube like
configuration consisting of eight or sixteen cells but they have a regular
shape
F. Sarcina
: these are rod shaped or cylindrical bacteria which either remain singly or
in pairs.
Bacilli
Bacilli 3
a. Diplobacilli:
b. Streptobacilli:
c. Coccobacilli:
appear in pairs after cell division
Diplobacilli
occurs in chain after cell division
Streptobacilli
: oval shaped similar
Coccobacilli
: curved, comma shaped bacteria and represented by a single genus.
Vibro
: spiral or spring like with multiple curvature and terminal flagella with
fairly rigid bodies.
Spirilla
: helical and flexible which move by means of axial filaments
resembling flagella but contained within an external sheath
Spirochete
BACTERIAL Structure
BACTERIAL Structure
: (meaning sugar coat) are viscous substances that surrounds the cell
composed of polysaccharide, polypeptide or both
Glycocalyx
Functions
: (1) enables bacteria
to survive by attaching to surfaces, example: Streptococcus mutans attaches tothe surface of the teeth and cause dental carries,
(2) bacterial source of energy
when supply is low, and
(3) protection to hosts cell by attaching to surface hence
preventing the movements of nutrients out of cell during dehydration.
Glycocalyx
It come in two forms:
– the substance is organized, is firmly attached to
the cell wall, and clinically contributes to the virulence (ability to cause disease) of
bacteria due to its capacity to evade phagocytosis by hosts cells,
(a.) capsule form
form – the substance in unorganized and is loosely attached to the cell wall
b.) slime layer
: (singular: flagellum, meaning whip) are long filamentous appendages
that propel bacteria.
Flagella
Three basic parts: fragella
(1) filament: long outermost part that
contains flagellin arranged in helix,
(2) hook: where filament is attached to, and
(3) basal body: anchors the flagellum to the cell wall and plasma membrane. The
flagella move by rotating from the basal body either in clock
Its movement is termed motility which is can be
presented in different patterns:
(a) run or swim: bacterium moves in one
direction,
(b) tumbles: periodic abrupt or random interruptions to run or swim and
(c) swarm: rapid wavelike movement
H
: also called endoflagella present in Spirochetes like Borrelia
burgdorferi that causes Lyme disease
Axial filaments
: is a type of a protein called pilin. It is a numerous hair like appendages
that surrounds the bacterium and helps to attach to hosts surfaces.
Pili: is another type of the protein pilin but is only presented in one or two per
bacterium. Pili helps bacterial cell to prepare DNA transfer from one cell to
another.
Fimbriae
: is another type of the protein pilin but is only presented in one or two per
bacterium. Pili helps bacterial cell to prepare DNA transfer from one cell to
another.
Pili
is a semi rigid structure protects the interior of the cell
from the outside environmen
The bacterial cell wall
6 Functions of cell wall
: (1) prevents rupture of the cell,
(2)maintain shape of cell,
(3) anchors flagella,
(4) contributes to the virulence of the
bacteria,
(5) site of action of some antibiotics, and
(6) the chemical composition
of cell is used to differentiate types of bacteria.
bacterial cell wall is primarily composed of network of peptidoglycan
(also called murein), either alone or in combination with other substances
Peptidoglycans
(also called murein),
have multiple layers of peptidoglycan in its cell wall for a thick
rigid structure
Gram
positive bacteria
It contains – which provide the antigenic capacity of
the bacteria making it possible to identify it upon laboratory tests
teichoic acids
has a thin layer of peptidoglycan
making it very susceptible to mechanical breakage or environmental degradatio
the cell wall of Gram negative bacteria
Cell wall (outer portion) Is composed of 3
- Lipopolyssachrides
- Lipoprotein
- Phospholipids
There are bacteria that is composed of higher percentage of —-
in their cell walls than peptidoglycan (Mycobacterium sp, Nocardia sp.), which
prevents reaction to Gram stain
mycolic acid
it can be stained with a carbolfuchsin
which resist removal with acid alcohol thus called
acid-fast bacteria
Structures internal to the cell wall
Plasma membrane: underlying the cell wall is a thin layer of plasma membrane
composed mainly of phospholipids arranged in two rows called
lipid bilayer
The outer surfaces of the lipid bilayer (polar heads) are
hydrophilic or water-loving
while the inside of the bilayer (nonpolar tails) are
hydrophobic or water-fearing
Functions OF PLASMA MEMBRANE
(1) entry/exit of substances in cell by selective permeability
(2)protect and lubricate the cell
(3) cell-to-cell interactions, and
(4) breakdown of
nutrients and energy production.
The movement of materials/substances across the membrane can be either
Passive or Active processes
PASSIVE INCLUDES:
- Simple diffusion
- Facilitated diffusion
- Osmosis
movement of molecules from high concentration to low concentration
1) Simple diffusion:
: same with simple diffusion but substances are transported
across the membrane via transporter
(2)
Facilitated diffusion:
: movement of a solvent
molecule (water) from high concentration to low concentration via a selectively
permeable membran
(3) Osmosis
Active process includes:
- Active transport
- Group translocation
: the cell
uses energy to transport a substance from lower to higher concentration without
altering the substance
(1) Active transport
: a special type of active that
alters the substance being transported across a membrane.
(2) group translocation
the substance inside the plasma membrane composed mainly of
water and other substances like proteins, carbohydrates or lipids.
Cytoplasm
also called nucleoid, located in the cytoplasm of a bacterial cell
contains double-stranded DNA each for the bacterial chromosome and plasmid.
Nuclear Area
present in both prokaryotic and eukaryotic cells and serve as sites
for protein synthesis
Ribosomes
Ribosomes have 2 subunits:
30S (small and contains one
molecule of ribosomal [rRNA] in bacteria),
50S subunit (larger and contains
two molecules of rRNA in bacteria).
Ribosomes in bacteria are called
called 70S
ribosomes.
Inclusions: these are reserve deposits of
(1) metachromatic granules (used in
ATP synthesis),
(2) polysaccharide granules,
(3) lipid inclusions,
(4) sulfurgranules (energy reserve), (5) carboxysomes (for carbon dioxide fixation)
(6) gasvacuoles (maintain buoyancy)
(7) magnetosomes: are iron oxide that acts
like magnet to move until attachment site
: these are specialized resting cell formed internal the cell
membrane when a bacterial cell goes into vegetative state (active cell that
undergoes metabolism) in a process called sporulation
Endospores
