1. MORPHOLOGY OF BACTERIA
DR.RUPAL PATEL

2. Pro = “before”, karyon = “nucleus” Prokaryotes :
Kingdom : PROTISTA
Prokaryotes :evolutionarily ancient. first and for billions of years ,only form of life..
Pro = “before”, karyon = “nucleus”
Prokaryotes :
Prokaryotes most always single-celled,.
Lack a membrane bound nucleus.
Genetic material naked within the cytoplasm,
Ribosomes their only type of organelle.
Nucleoid region of cytoplasm where chromosomal DNA is located, usually a singular, circular chromosome.
Reproduce by means of binary fission, duplicating their genetic material and then essentially splitting to form two daughter cells identical to the parent.
Bacteria (including the blue green "algae") are prokaryotes.
Higher organisms together with microorganisms such as fungi, protozoa are eukaryotes.

3. PROKARYOTES VERSUS EUKARYOTES
a) Size
1-10 microns
microns
b) Complexity
unicellular, rarely small clusters or filaments
sometimes unicellular more often multicellular
c) Membrane bound organelles
none (mesosome is infolding of cytoplasmic membrane)
nuclei, mitochondria, chloroplasts, lysosomes, endoplasmic reticulum, golgi, & vacuoles
d) Nucleus no
yes
e) Chromosomes
single & circular
usually several & linear
f) Mitosis & Meiosis
absent
present
g) Endocytosis & cytoplasmic streaming
h)Sterols
usually absent
used as hormones and in plasma membrane

4. Shapes of Bacteria Coccus Bacillus Coccobacillus Vibrio = curved
Chain = Streptoccus
Cluster = Staphylococcus
Bacillus
Chain = Streptobacillus
Coccobacillus
Vibrio = curved
Spirillum
Spirochete

5. Coccus:
The cocci are spherical or oval bacteria having one of several distinct arrangements:

8. Bacillus:
Bacilli are rod-shaped bacteria. They divide in one plane producing one of the following:

9. Spiral:
A helical or corkscrew- shaped bacterium. Spirals come in 1 of 3 form
Vibrio: curved or comma- shaped rod
Spirillum: thick, rigid spiral
Spirochete: thin, flexible spiral

10. Bacterial Structures Cell Wall Plasma Membrane Cytoplasm Flagella
- Lipopolysaccharides
-Teichoic Acids
Plasma Membrane
Cytoplasm
Flagella
Pili (fimbria)
Capsule
Inclusions
Spores

13. Cell Wall Functions : 20-40% of bacteria
Unique structure which surrounds the cell membrane.
Not present in every bacterial species
Functions :
-Maintaining the cell's characteristic shape
-Countering the effects of osmotic pressure
-Providing attachment sites for bacteriophages- teichoic acids attached to the outer surface of the wall are like landing pads for viruses that infect bacteria
-Providing a rigid platform for surface appendages- flagella, fimbriae, and pili
Some antibiotics effect directly
Penicillin

14. Peptido-glycan Polymer (amino acids + sugars)
Cell Wall
Peptido-glycan Polymer (amino acids + sugars)
Sugars; NAG & NAM
- N-acetylglucosamine
- N-acetymuramic acid
D form of Amino acids used
The peptidoglycan polymer is composed of an alternating sequence of N-acetylglucosamine and N- acetyl-muraminic acid.
Each peptidoglycan layer is connected, or cross linked, to the other by a bridge made of amino acids and amino acid derivatives.
The cross linked peptidoglycan molecules form a network which covers the cell like a grid.

17. There are two major types of walls: -Gram-positive and Gram-negative.
The cell walls of all bacteria are not identical.
Cell wall composition is one of the most important factors in bacterial species analysis and differentiation.
There are two major types of walls:
-Gram-positive and Gram-negative.

18. Gram-positive bacteria
Many polymer layers of peptidoglycan connected by amino acid bridges.
90% of the Gram-positive cell wall is comprised of peptidoglycan.
TEICHOIC ACIDS
-Glycerol, Phosphates, & Ribitol
-Attachment for Phages

19. Gram-negative bacteria
Much thinner, only 20% peptidoglycan.
Two unique regions
A) Periplasmic space
- separates the outer plasma membrane from the peptidoglycan layer.
- contains proteins which destroy potentially dangerous foreign matter present in this space.
B) Lipopolysaccharide layer(LPS)
- Located adjacent to the exterior peptidoglycan layer.
- Phospholipid bilayer attached to the peptidoglycan by lipoproteins.
-The lipid portion of the LPS contains a toxic substance, called Lipid A, responsible for most of the pathogenic affects associated with harmful Gram-negative bacteria.
-Polysaccharides extend out from the bilayer contibute to the toxicity of LPS.
The LPS, lipoproteins, and the associated polysaccharides together form what is known as the outer membrane

21. LPS (cont’d) Functions Heat Resistant; hard to remove
Toxic:
Gm -ve septicemia; death due to LPS
Pyrogen; causes fever
Heat Resistant; hard to remove
Acetone or alcohol can remove
O Antigen of Salmonella and E. coli
2,000 different O Ags of Salmonella
100’s different O Ags of E. coli
E. coli O157

22. cytoplasmic membrane :delicate and plastic structure that completely encloses the cell cytoplasm (or protoplasm)
Made up of a phospholipid bilayer
Proteins are embedded in the membrane.
-TRANSPORT proteins that BIND specific molecules and carry them into or out of the cell as required.
These proteins are held in the membrane by virtue of hydrophobic and hydrophilic regions on the protein.
Contains enzymes involved in cellular respiration, peptidoglycan biosynthesis

23. Cytoplasm
Colloidal system containing organic and inorganic solutes in a viscous watery solution
Ribosomes :
-protein synthesis
-slightly smaller than eukaryotic cells (70 S)
Mesosomes :
-vesicular, convoluted or multilaminated structures
- site of the synthesis of cross wall septa
Intracytoplasmic inclusions
- volutin granules present in Diptheria bacilli

24. Nucleus No nuclear membrane
Genome :single , circular ,double stranded DNA
Extra nuclear genetic elements : Plasmids
- transferred from one bacterium to another either through conjugation or through bacteriophages
- confer properties like toxigenecity and drug resistance

25. Flagella
Flagella are whip-like structures protruding from the bacterial cell wall and are responsible for bacterial motility (i.e. movement).
Long (3 to 12 µm), diameter about nanometers
The protein subunits of a flagellum are assembled to form a cylindrical structure with a hollow core.
Immunogenic
Constitute a group of protein antigens called the H antigens, which are characteristic of a given species, strain, or variant of an organism.
Antigenic changes of the flagella known as the phase variation of H1 and H2 occurs in Salmonella typhimurium

26. A flagellum consists of three parts:
(1) long filament, which lies external to the cell surface;
(2) hook structure at the end of the filament;
(3) basal body, to which the hook is anchored with series of rings that drive the flagella. and which imparts motion to the flagellum.

27. Typical arrangements of bacterial flagella

28. Detecting Bacterial Motility
1. Flagellar stains : outline flagella and show their pattern of
distribution. If a bacterium possesses flagella, it is presumed to
be motile.

29. 2.Motility test medium :. straight- line stab.
-Semisolid medium (0.5 % % agar ) inoculated with bacteria in a
straight- line stab.
-After incubation : turbidity (cloudiness) due to bacterial growth away
from the line of the stab : bacteria able to swim through the medium.

30. 3. Direct microscopic observation in a wet mount.
-Brownian movement, due to random collisions between water molecules and bacterial cells.
-True motility ,bacterium swim from one side of the microscope field to the other side.

31. Fimbriae and Pili Fimbria :
-protein tubes that extend out from the outer membrane.
-generally short in length
-present in high numbers about the entire bacterial cell surface.
-facilitate the attachment of a bacterium to a surface (e.g. to form a biofilm) or to other cells (e.g. animal cells during pathogenesis).
Pili :
-similar in structure
-much longer
-present on the bacterial cell in low numbers.
-involved in the process of bacterial conjugation.

32. Fimbriae (common pili) and flagella on the surface of bacterial cells.
Left: dividing Shigella enclosed in fimbriae. The structures are probably involved in the bacterium's ability to adhere to the intestinal surface.
Right: dividing pair of Salmonella displaying both its peritrichous flagella and its fimbriae. The fimbriae are much shorter and slightly smaller in diameter than flagella.

33. Capsules and Slime Layers
A true capsule : Discrete detectable layer of polysaccharides deposited outside the cell wall. Sharply defined.
Slime layer (biofilm ):A less discrete structure or matrix which embeds the cells .Loose undemarked secretion
Glycocalyx or microcapsule: very thin layer of tangled polysaccharide fibers on the cell surface.
Generally composed of polysaccharides; rarely they contain amino sugars or peptides.

34. Functions Adherence of cells to surfaces.
Protect bacterial cells from engulfment by protozoa or white blood cells (phagocytes)
Protect from attack by antimicrobial agents
protect cells from effects of drying or desiccation.
Ability to block some step in the phagocytic process so prevent the bacterial cells from being engulfed or destroyed by phagocytes (white blood cells).
-Streptococcus pneumoniae (lobar pneumonia)
-Bacillus anthracis (anthrax)
-Neisseria meningitidis (meningitis

35. spore
Endospores are highly heat-resistant, dehydrated resting cells formed intracellularly in members of the genera Bacillus and Clostridium.
Sporulation, the process of forming endospores, is an unusual property of certain bacteria.
The process, usually begins in the stationary phase of the vegetative cell cycle, is initiated by depletion of nutrients (usually readily utilizable sources of carbon or nitrogen, or both).
The cell then undergoes a highly complex, well-defined sequence of morphologic and biochemical events that ultimately lead to the formation of mature endospores.

36. Structure of a bacterial endospore, renowned as the most durable and long-lived type of cell on earth

37. The cross section of a bacterial spore, such as anthrax, shows its hard, multilayered coats, which both make the spore difficult to kill and allow it to remain dormant for many years.

38. The cycle of spore formation and germination
At the beginning of spore formation, a septum forms, separating the nascent spore from the rest of the cell and all of the genetic material of the cell is copied into the newly-forming cell.
The spore contents are dehydrated and the protective outer coatings are laid down.
Once the spore is matured it is released from the cell.
On germination, the spore contents rehydrate and a new bacterium emerges and multiplies.

39. Spore structure and arrangements.
General structure of a bacterial Endospore
A = oval, terminal;
B = rectangular, terminal;
C = rectangular, subterminal,
D = rectangular, central;
E = circular, terminal;
F = circular, central;
G = terminal, club-shaped.