PRESNTATION ON BACTERIA
FIRDOUS FATIMA
B.SC(ZOOLOGY)
4TH SEM
INTRODUCTION TO BACTERIA
Bacteria are microscopic, unicellular, prokaryotic
organisms.
They do not have membrane-bound cell organelles
and lack a true nucleus
bacterium,word is derived from the Ancient Greek
word “backērion” meaning “cane”
as the first bacteria observed were bacilli.
The study of ‘Bacteria’ is called ‘Bacteriology’; a
branch of ‘Microbiology’.
HABITAT TO BACTERIA
They are not only in normal ecological habitats but
are also found in extreme environments. Such
bacteria are called extremophilic bacteria.
They are found in extreme cold (Psychrophiles),
extremely hot (thermophiles),
extreme pH (acidophiles and Alkaliphiles),
extreme pressure (barophiles),
anoxic environments (anaerobic),
desertic area (xerophiles),
STRUCTURE OF BACTERIA
Bacteria are unicellular i.e. made up of a single
cell. They are prokaryotes and their cells are
different from animal and plant cells. the
structure of bacteria can be studied as external
and internal structures;
OUTER STRUCTRE OF BACTERIA
1. Flagella (sing. Flagellum)
Flagella are long hair-like filamentous structures
of about 4 – 5 μm long . They confer motility to
the bacteria.
Flagella are divided into three parts;
filament, hook, and the basal body.
PILLI
They are the short, hollow, non-helical
filamentous structure of about 0.5 μm in length
and 0.01 μm in diameter.
They are exclusively found in Gram-Negative
bacteria.
CELL WALL
It is a viscous outermost layer surrounding
the cell wall.
It is composed of either polysaccharides or
polypeptides .
They are present only in some species of bacteria.
The capsule is of 2 types; macro-capsule
micro-capsule
SHEATH….
A sheath is a hollow tube-like structure mostly
aquatic bacteria. It provides mechanical strength
to the chain
The cell wall is a rigid structure made up of
peptidoglycan that surrounds the plasma
membrane as an external coat.
INTERNAL STRUCTURE OF CELL….
CELL MEMBRANE
It is the innermost phospholipid bilayer, just
beneath the cell wall, enclosing cytoplasm. It is a
thin and semipermeable layer.
The plasma membrane is equipped with several
porin proteins for the passive transport of
nutrients and ions.
CYTOPLASM
It is a colorless, colloidal, viscous fluid with
suspended organic and inorganic solutes enclosed
within the plasma membrane.
RIBOSOMES
. Their main role is to synthesize bacterial
proteins and enzymes.
MESOSOMES
. They represent the eukaryotic mitochondria in
function and are the site of action of the bacterial
respiration enzymes.
INCLUSION BODIES
They are believed to be storage food. They are of
two types; (i) organic inclusion bodies, containing
glycogen and (ii) inorganic inclusion bodies,
containing polyphosphate or sulfur granules.
BACTERIA NUCLEOUS…..
They are called nucleoids. Unlike eukaryotic
nuclei, they are not enclosed in the nuclear
membrane and lack nucleolus and nucleoplasm
SHAPE OF BACTERIA
1.COCCI
They are spherical bacteria. Based on the arrangement of cells
they are further sub-grouped as;
Monococci; singular cocci. Eg. Micrococcus luteus,
Diplococci; two spherical bacteria are arranged in pairs.
Eg.pneumoniae, etc.
Streptococci; spherical bacteria are arranged in a long chain.
Eg. Streptococcus pyogenes, etc.
Staphylococci; spherical bacteria arranged in irregular clusters
like a bunch of grapes. Eg. saprophyticus, etc.
Tetrad; arrangement in a group of 4 cocci.
Sarcinae; arrangement of cocci in a group of 8.
BACILLUS
They are rod-shaped bacteria. Based on the
arrangement of cells they are also sub-grouped as;
Bacillus /Mono–bacillus; single unattached rod-
shaped bacteria. Eg. Bacillus cereus, etc.
Diplobacilli; bacilli arranged in a pair. Eg.
Moraxella bovis,etc.
Streptobacilli; bacilli arranged in a chain. Eg.
Streptobacillus moniliform, etc
COMMA SHAPED
They are long helical-shaped or twisted bacteria.
Eg. Spirilla spp. , Spirochetes spp. , etc.
They are comma (,) like in structure. Eg. Vibrio
spp.
Filamentous (E.g. Actinobacteria, etc. )
Star shaped (E.g. Stella humosa, etc)
CLASSIFICATION OF BACTERIA BASED ON GRAM STAINING….
GRAM POSITIVE BACTERIA GRAM NEGATIVE BACTERIA
Stains violet/purple during Gram staining
Thick cell wall Stains red/pink during Gram staining
Thick peptidoglycan layer Thin cell wall
Thin peptidoglycan layer
Mesosomes present Mesosomes absent (rarely present)
Fimbriae or pili absent Fimbriae or pili present
Presence of an outer layer
Lack an outer layer
