nd
and PARASITOLOGY 2
Semester
has a complex glycolipid called lipid A,
Chapter 3: BACTERIAL MORPHOLOGY
responsible for its endotoxin activity.
• BACTERIA -It is located in the outer leaflet of the outer
- are prokaryotic, have simpler structures membrane.
compared to eukaryotic organisms. -The inner core is a polysaccharide made up of
May be classified into three basic shapes: repeat units also called as O antigen.
(a) Spherical or Cocci- (ex: 2. Lipoprotein– functions to anchor the outer
Staphylococcus, Streptococcus) membrane to the peptidoglycan layer and
(b) Rod-shaped or Bacilli- (ex: Escherichia stabilizes the outer membrane.
coli, Salmonella) 3. Periplasmic space – a fluid filled space
(c) Curved or Spiral between the outer membrane and the inner
plasma membrane.
• ENVELOPE STRUCTURES -It contains enzymes for the breakdown of large
Prokaryotic cells are surrounded by a complex non transportable molecules into transportable
envelope that may vary in composition. ones and enzymes that serve to detoxify and
-Serves to protect the bacteria from harsh inactivate antibiotics.
environmental conditions.
GLYCOCALYX Acid-fast cell wall:
- the outermost covering of some bacteria. - acid fast organisms possess an outer layer
- a gelatinous substance that is located that is lipid rich.
external to the cell wall, composed of - composed of large amounts of waxes that are
polysaccharide or polypeptide, or both. known as mycolic acids.
-It is called capsule if it is strongly attached - Hydrophobic
to the cell wall and slime layer if it is loosely • PROTECTING STRUCTURES
attached. FLAGELLA
-The presence of the capsule is indicative of -thread like structures made up entirely of
the virulence of an organism, aiding the molecules of the protein sub unit flagellin.
organism in the evasion of phagocytosis. It They project from the capsule and are organs
is also antigenic. for motility.
-protect the organism from dehydration. -Classified into four types:
a) Monotrichous (single polar flagellum);
CELL WALL (b) lophotrichous (a tuft of flagella at one
-sometimes called the murein sacculus. end of the bacterium)
-provides rigid support and shape to the (c) Amphitrichous (flagella at both ends of
bacteria. the bacterium); and
-its principal component is peptidoglycan (d) Peritrichous (flagella all around the
-It is multi layered in gram positive bacterium).
bacteria and single layered in gram Bacteria without flagella are called
negative bacteria. atrichous.
-It protects the bacteria from osmotic damage
and plays an important role in cell division PILI or FIMBRIAE
- fine and short in comparison with flagella.
Special components of gram-positive cell walls: -structural protein sub-units are called pilins.
1. Teichoic acids – function for the attachment of -It functions for adherence to cell surface
the bacterium to the host cell. (common pilus) or attachment during
-also provide tensile strength to gram positive conjugation (sex pilus).
bacterial cell walls. -Pili may also function for motility.
2.Polysaccharides–polysaccharide molecules
include neutral sugars such as mannose and AXIAL FILAMENTS
glucosamine. It also includes some acidic sugars - are also called endoflagella and are found in
such as glucuronic acid and mannuronic acid. spirochetes.
- These are composed of bundles of fibrils,
Special components of gram-negative cell walls: the structures of which are similar to flagella.
1. Outer membrane– a bi layered structure They arise from the ends of the bacterial cell
where the inner leaflet is composed of a and spiral around the cell.
lipopolysaccharide(LPS). It has special protein
channels that allow the passage of small or low
molecular weight hydrophilic substances. LPS
and PARASITOLOGY 2
Semester
has a complex glycolipid called lipid A,
Chapter 3: BACTERIAL MORPHOLOGY
responsible for its endotoxin activity.
• BACTERIA -It is located in the outer leaflet of the outer
- are prokaryotic, have simpler structures membrane.
compared to eukaryotic organisms. -The inner core is a polysaccharide made up of
May be classified into three basic shapes: repeat units also called as O antigen.
(a) Spherical or Cocci- (ex: 2. Lipoprotein– functions to anchor the outer
Staphylococcus, Streptococcus) membrane to the peptidoglycan layer and
(b) Rod-shaped or Bacilli- (ex: Escherichia stabilizes the outer membrane.
coli, Salmonella) 3. Periplasmic space – a fluid filled space
(c) Curved or Spiral between the outer membrane and the inner
plasma membrane.
• ENVELOPE STRUCTURES -It contains enzymes for the breakdown of large
Prokaryotic cells are surrounded by a complex non transportable molecules into transportable
envelope that may vary in composition. ones and enzymes that serve to detoxify and
-Serves to protect the bacteria from harsh inactivate antibiotics.
environmental conditions.
GLYCOCALYX Acid-fast cell wall:
- the outermost covering of some bacteria. - acid fast organisms possess an outer layer
- a gelatinous substance that is located that is lipid rich.
external to the cell wall, composed of - composed of large amounts of waxes that are
polysaccharide or polypeptide, or both. known as mycolic acids.
-It is called capsule if it is strongly attached - Hydrophobic
to the cell wall and slime layer if it is loosely • PROTECTING STRUCTURES
attached. FLAGELLA
-The presence of the capsule is indicative of -thread like structures made up entirely of
the virulence of an organism, aiding the molecules of the protein sub unit flagellin.
organism in the evasion of phagocytosis. It They project from the capsule and are organs
is also antigenic. for motility.
-protect the organism from dehydration. -Classified into four types:
a) Monotrichous (single polar flagellum);
CELL WALL (b) lophotrichous (a tuft of flagella at one
-sometimes called the murein sacculus. end of the bacterium)
-provides rigid support and shape to the (c) Amphitrichous (flagella at both ends of
bacteria. the bacterium); and
-its principal component is peptidoglycan (d) Peritrichous (flagella all around the
-It is multi layered in gram positive bacterium).
bacteria and single layered in gram Bacteria without flagella are called
negative bacteria. atrichous.
-It protects the bacteria from osmotic damage
and plays an important role in cell division PILI or FIMBRIAE
- fine and short in comparison with flagella.
Special components of gram-positive cell walls: -structural protein sub-units are called pilins.
1. Teichoic acids – function for the attachment of -It functions for adherence to cell surface
the bacterium to the host cell. (common pilus) or attachment during
-also provide tensile strength to gram positive conjugation (sex pilus).
bacterial cell walls. -Pili may also function for motility.
2.Polysaccharides–polysaccharide molecules
include neutral sugars such as mannose and AXIAL FILAMENTS
glucosamine. It also includes some acidic sugars - are also called endoflagella and are found in
such as glucuronic acid and mannuronic acid. spirochetes.
- These are composed of bundles of fibrils,
Special components of gram-negative cell walls: the structures of which are similar to flagella.
1. Outer membrane– a bi layered structure They arise from the ends of the bacterial cell
where the inner leaflet is composed of a and spiral around the cell.
lipopolysaccharide(LPS). It has special protein
channels that allow the passage of small or low
molecular weight hydrophilic substances. LPS
