Bacterial Cell Presentation2
Bacterial Cell Presentation2
Bacterial Cell Presentation2
Kingdom -Protista
They have unique outer most covering - the cell wall not commonly found
in animal cells.
Spiral bacteria
1. Spirillum----a
1. helical shape, like a corkscrew,
Vibrios
-curved rods
Bacterial CellStructural
Components
Bacterial Surface Structures Internal Bacterial Structures
Glycocalyces Cytoplasm
Non-membranous Organelles
Flagella Ribosomes
Fimbria &Pili Cytoskeleton
Inclusions
Cell Wall
Mesosomes
Cell Membranes Plasmids
Nucleoid
Glycocalyces
2. Slime layer
Glycocalyces
Capsule Slime layer
Gram +ve rods (e.g. Listeria spp) & cocci( Enterococcus &
Vagococcus spp
Flagella Arrangement
Basal body :-
is composed of M,S,P and L rings anchored in the membrane ,
periplasmic space , peptidoglycan and LPS outer membrane .
Basal body anchors filament and hook to cell wall by a rod and a
series of either two or four rings of integral proteins
Function of Flagella -Motility
Motility is due to rotation of flagella
Filament capable of rotating 360
Mechanism of rotation:
The ability of the organisms to express two types of flagella alternately is k/a
phase variation.
First recognized in enteric gram-ve bact ( e.g. Salmonella spp), but also occurs
in other spp such as N. gonorrhoeae.
Found in Spirochetes----Cork
Screw Motion
T. pallidum Syphills
Virulence factor
Pili
Fimbriae of gram negative bacteria that
function specifically in transfer of DNAfrom
one cell to another during process of
conjugation
Thickness 1580 nm 2 nm
Lipid content 25% 1520%
Teichoic acid Present Absent
Variety of amino acid Few Several
Aromatic amino acid Absent Present
Action as endotoxin No Yes
Sulfur-containing amino Absent Present
acid
Treatment with Protoplast Spheroplast
lysozyme
Diagrammatic Difference b/w Gram positive
and Gram negative cell wall
Gram Negative Bacteria--Lipopolysacharide
LPS mol high mol wt complex glycolipids
Consisting of 3 major components:
1. Lipid A
2. Core polysaccharide region
3. O-specific polysaccharide side chain
Lipid A Composed of : hydroxymyristic
Glucosamine disaccharide acid, a unique fatty
hydroxyl groups disaccharide unit is acid, which is
esterified to -hydroxy fatty acids associated with
examples endotoxic activity
of the LPS
Core Core polysaccharide contains 2 two Linked to lipid A.
polysacch characteristic sugars Covalently b/w
aride 8C-ketodeoxyoctanoic acid (KDO) and hepatose lipid A
Region 7C-a heptose
O-specific are attached to core polysaccharide &
side are responsible for antigenic specificity of
chains individual isolates.
Gram Negative Bacteria--
Lipopolysacharide
Acid-fast Cell Walls
Bacteria with No Cell Wall: Mycoplasmas
Instead, have cell membrane
which incorporates
cholesterol compounds
(sterols), similar to
eukaryotic cells
Cannot be detected by
typical light microscopy
Functions of Cell Wall
It helps maintain the shape of a bacterium
Gram +ve bacteria : lies immediately within the cell wall peptidoglycan.
1. Phosphatidyl glycerol
2. Phosphatidyl ethanolamine
3. Diphosphatidyl glycerol
Bacterial Cytoplasmic Membrane-Structure( Contd)
5. -DNA replication
Cytoplasm Matrix
4. Cytoplasmic enzymes
1. Function in both anabolic & catabolic processes
- bacterial virulence
- genes for antimicrobial resistance
- virulence-related adhesins
- toxin production
- resistance to heavy metal ions
Site for antibiotics
1. Chloramphenicol
Ribosomes 2. Clindamycin
3. Erythromycin
4. Linezolid
Ribosomes sites of protein synthesis
Nonmembranous Organelles Site for antibiotics
1. Aminoglycosides
The ribosomes are 70S( mol wt of 2. Tetracyclins
80kDa.)
10-20nm in diameter
Exist in a dissociated state as 2
subunits ; 30S & 50S.
The 30S subunit contains the
16S RNA species
The 50S subunit contains both
23S & 5S RNA
Ribosomes(Contd----)
Composed of both RNA and proteins.
Length=300 to 1400 m
May differ in their location within the cell ( central, terminal or sub
terminal )