Lesson 7: BACTERIAL MORPHOLOGY AND FINE STRUCTURE Flashcards
The major characteristics of bacteria are based on their
size, shape and
arrangements
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.
singular: coccus meaning berries
Cocci
usually round 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
represented by single, discrete round cell
Monocuccus
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
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.
Sarcina
these are rod shaped or cylindrical bacteria which either remain singly or in pairs.
Bacilli
appear in pairs after cell divides
Diplobacilli
occurs in chain after cell division
Streptobacilli
oval shaped similar to cocci
Coccobacilli
curved, comma shaped bacteria and represented by a single genus
Vibro
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
Structures external to the cell wall
Glycocalyx
Flagella
Axial Filaments
Fimbriae
Pili
meaning sugar coat
Glycocalyx
are viscous substances that surrounds the cell composed of polysaccharide, polypeptide or both.
Glycocalyx
long outermost part that contains flagellin arranged in helix
filament
Functions of Glycocalyx
- enables bacteria to survive by attaching to surfaces, example: Streptococcus mutans attaches to the surface of the teeth and cause dental carries
- bacterial source of energy when supply is low
- protection to hosts cell by attaching to surface hence preventing the movements of nutrients out of cell during dehydration.
2 forms of glycocalyx
Capsule form and slime layer form
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
Capsule form
the substance in unorganized and is loosely attached to the cell wall.
Slime layer form
meaning whip
Flagella
Three basic parts of Flagella
Filaments
hook
Basal body
long filamentous appendages that propel bacteria
Flagella
where filament is attached to
hook
anchors the flagellum to the cell wall and plasma membrane. The flagella move by rotating from the basal body either in clockwise or counterclockwise direction.
Basal body
bacterium moves in one
direction
run or swim
movement is termed motility which is can be
presented in different patterns
run or swim
tumbles
swarm
rapid wavelike movement
swarm
periodic abrupt or random interruptions to run or swim
tumbles
also called endoflagella present in Spirochetes like Borrelia burgdorferi that causes Lyme disease. The filaments are actually bundled fibrils that arise at one end of Spirochetes and spiral around it. When these filaments rotate it causes the Spirochetes to a spiral motion.
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 surface
Fimbriae
another type of the protein pilin but is only presented in one or two per bacterium. helps bacterial cell to prepare DNA transfer from one cell to another
Pili
Functions of the cell wall
- prevents rupture of the cell
- maintain shape of cell
- anchors flagella
- contributes to the virulence of the bacteria
- site of action of some antibiotics
- the chemical composition of cell is used to differentiate types of bacteria.
Semi rigid structure protects the interior of the cell from the outside environment.
The cell wall
The bacterial cell wall is primarily composed of
Peptidoglycan
Gram positive bacteria contains which provide the antigenic capacity of the bacteria making it possible to identify it upon laboratory tests.
Teichoic Acid
Peptidoglycan is also called
Murein
primarily composed of network of peptidoglycan either alone or in combination with other substances
Bacterial cell wall
have multiple layers of peptidoglycan in its cell wall for a thick rigid structure.
Gram Positive Bacteria
has a thin layer of peptidoglycan making it very susceptible to mechanical breakage or environmental degradation.
Gram negative bacteria
also called
endotoxin
Lipopolysaccaharides
Gram negative bacteria cell wall (outer portion) is composed of
lipopolysaccharide
lipoproteins and
phospholipid
Functions of lipopolysaccharide lipoproteins and phospholipid
- evades phagocytosis and cell lysis
- barrier to antibiotics and other enzymes
- passage of molecules thru porin channels.
Functions of LPS
- provides antigenic capacity of the bacteria
- causes physiological effects when present in the bloodstream (toxicity, fever, sepsis, shock,
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 stains.
Mycolic Acid
Mycolic acid can be stained with
Carbolfuchsin
Bacteria that is composed of higher percentage of mycolic acid in their cell walls than peptidoglycan it can be stained with a carbolfuchsin which resist removal with acid alcohol thus called
Acid-fast bacteria
Some chemicals like ____________ can cause damage, or interfere with the synthesis of cell walls by cell lysis.
lysozyme
Example of acid-fast bacteria are
Mycobacterium sp
Nocardia sp.
Bacteria that have an atypical cell wall
Mycoplasma sp.
having no cell wall or with very little wall material
Atypical cell wall
Structures internal to the cell wall
Plasma membrane
cytoplasm
Nuclear area
Ribosomes
Inclusions
Endospores
underlying the cell wall is a thin layer of ____________ composed mainly of phospholipids arranged in two rows called lipid bilayer
Plasma membrane
inside of the bilayer (nonpolar tails) are
hydrophobic or water-fearing
The outer surfaces of the lipid bilayer (polar heads) are
hydrophilic or water-loving
Functions of plasma membrane
- entry/exit of substances in cell by selective permeability
- protect and lubricate the cell
- cell-to-cell interactions, and
- breakdown of nutrients and energy production.
includes
1. Simple diffusion
2. Facilitated diffusion
3. Osmosis
Passive Processes
The movement of materials/substances across the membrane can be either
Active or passive processes
movement of molecules from high concentration to low concentration
Simple diffusion
same with simple diffusion but substances are transported across the membrane via transporter
Facilitated diffusion
movement of a solvent molecule (water) from high concentration to low concentration via a selectively permeable membrane.
Osmosis
the substance inside the plasma membrane composed mainly of water and other substances like proteins, carbohydrates or lipids.
Cytoplasm
Includes
1. Active transport
2. group translocation
Active Processes
the cell uses energy to transport a substance from lower to higher concentration without altering the substance
Active transport
a special type of active that alters the substance being transported across a membrane.
Group Translocation
also called nucleoid, located in the cytoplasm of a bacterial cell contains double-stranded DNA each for the bacterial chromosome and plasmid.
Nuclear area
contains the genetic information of the cell
Bacterial Chromosomes
carry genes associated to antibiotic resistance, toxin production or enzyme synthesis. important in gene manipulation of bacteria.
Plasmid
Ribosomes have 2 subunits:
30s and 50s
present in both prokaryotic and eukaryotic cells and serve as sites for protein synthesis. The number of this is proportional to the rate of protein production.
Ribosomes
small and contains one
molecule of ribosomal [rRNA] in bacteria
30s subunit
larger and contains two molecules of rRNA in bacteria
50s subunit
Ribosomes in bacteria are called
70s bacteria
released when bacterial (parent) cell is degraded. It is capable of resistance to harsh chemicals, extreme environmental condition, and radiation. It can remain dormant for a thousand years and can return to vegetative state by germination when endospore’s coat is triggered either by physical or chemical damage.
Endospores
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
Reserve deposits
- metachromatic granules
- polysaccharide granules
- lipid inclusions
- sulfur granules
- carboxysomes
- gas vacuoles
- magnetosomes
these are reserve deposits
Inclusions
for carbon dioxide fixation
carboxysomes
Reserve Energy
Sulfur granules
use in ATP synthesis
Metachromatic granules
Maintain buoyancy
gas vacuoles
iron oxide that acts
like magnet to move until attachment
magnetosomes
