5. BACTERIA
• Bacteria are large group of single celled
prokaryotic microorganisms
• 10 times as many bacteria cells in the human
flora as there are human cell in the body
8. Bacterial Size
• Bacteria range in size from about 0.2 to 5 µm.
• The smallest bacteria (Mycoplasma) are about the
same size as the largest viruses (poxviruses) and are
the smallest organisms capable of existing outside
the host.
• The longest bacteria rods approach the size of some
yeasts and human R.B.Cs
10. According to staining
• Gram positive Thick peptidoglycan layer
and teichoic acid
• Gram negative Thin peptidoglycan layer and
lipopolysaccharide- endotoxin
• Acid fast bacilli Mycolic acid (lipids)
11. • Some bacteria are variable in shape
• PLEOMORPHIC----many shaped
• Shape of the bacteria is determined by its rigid
cell wall
• The microscopic appearance of bacterium is most
important criteria for its identification
12. 12
pH requirements
• Most grow best at pH of 6.5 to 7.0
• Many act as decomposers
recycling nutrients
• Some cause disease (Pathogenic)
13. The Prokaryote
• Structural Components
MACROMOLECULE SUBUNIT POSITION IN CELL
PROTEIN Amino Acid Flagella, pili, cell wall,
cytoplasmic membrane,
ribosomes, cytoplasm
POLYSACCHARIDE Sugar/Carbohydrate Capsule, Inclusions, Cell wall
PHOPHOLIPID Fatty Acid Membranes
NUCLEIC ACID
(DNA/RNA)
Nucleotide DNA, Nucleoid, Plasmids,
Ribosomes,
16. BACTERIAL STRUCTURE
COVERING LAYERS
• Cell wall
• Peptidoglycan
Sugar back bone
with peptide side
chains,which are
cross linked
Rigidity osmotic
protection , site of
action of antibiotic,
lysozyme degrade.
Outer membrane
Gram Negative
bacteria
Lipid A
Polysaccharide
Toxic component
of endotoxin.
Surface antigen.
Surface fiber on
Gram Positive
bacteria
Teichoic acid Surface antigen
17.
18. 18
Protection
• Cell Wall made of Peptidoglycan
• May have a sticky coating called
the Capsule for attachment to
host or other bacteria
19. FUNCTION OF CELL WALL
• Maintaining the cell's characteristic shape
• Countering the effects of osmotic pressure
• Providing attachment sites for
bacteriophages-teichoic acids
• Providing a rigid platform for surface
appendages- flagella, fimbriae
22. COMPARISON
Property Gram Positive Gram Negative
Thickness of wall 20-80 nm 10 nm
Number of layers in wall 1 2
Peptidoglycan content >50% 10-20%
Teichoic acid in wall + -
Lipid and lipoprotein content 0-3% 58%
Protein content 0% 9%
Lipopolysaccharide 0 13%
Sensitive to penicliiin + - (not as much)
Digested by lysozyme + - (not as much)
23. Properties of cell wall
• Gram negative bacteria contains endotoxin---
lipopolysaccharide
• Polysaccharides and proteins are antigens
• Porin proteins helps entry of hydrophilic
molecules
• Teichoic acid are fibers on outer surface of
gram positive ---ability to induces septic shock
24. Cell Membrane
• Composed of phospholipid bilayer
• FUNCTIONS
• Active transport
• Energy generation---oxidative phosphorylation
• Synthesis of precursors of cell wall
• Secretion of enzymes and toxins
25. 25
• Infoldings of cell membrane carry
on photosynthesis & cellular
respiration
• Infoldings called Mesosomes
28. Plasmids
• Molecules of DNA that are found in bacteria
separate from the bacterial chromosome.
• A circular molecule only much SMALLER than the
genomic DNA
• REPLICATE AUTONOMOUSLY from the genomic
chromosome. Often there are MANY PLASMID
COPIES present in one cell. Further, a cell may
contain SEVERAL DIFFERENT PLASMIDS or it may
contain NO PLASMIDS at all. Plasmids generally carry
genes that are NOT ESSENTIAL for a cell's survival
• May carry genes for ANTIBIOTIC RESISTANCE
29. Transposons
• Transposons are pieces of DNA move from one
site to another ---- within or between the
DNAs of bacteria plasmid or bacteriophage.
• Nick name as Jumping genes
• Genes for one or more (usually more) proteins
imparting resistance to antibiotics. When such
a transposon is incorporated in plasmid, it can
leave the host cell and move to another. This
is the way that the alarming phenomenon of
multidrug antibiotic resistance spreads so
rapidly.
31. 31
Flagella
• Bacteria that are
motile have
appendages called
flagella
• Attached by Basal
Body
• A bacteria can have
one or many
flagella
32. 32
Flagella
• Made of Flagellin
• Used for Classification
• Monotrichous: 1
flagella
• Lophotrichous: tuft at
one end
• Amphitrichous: tuft at
both ends
• Peritrichous: all around
bacteria
33. 33
Pili
• Short protein appendages PILIN
• Smaller than flagella
• Adhere bacteria to surfaces
• Used in conjugation for Exchange of
genetic information
• Aid Flotation by increasing buoyancy
