bacteria lecture

1. MORPHOLOGY OF BACTERIA
MICROBIOLOGY FOR
NURSING TEACHING GROUP

2. 1969, Robert H. Whittaker founded the five-kingdom
5 main kingdoms:
 Protista (mostly single celled)
 Fungi (unicellular or multicellular, absorptive
 Plantae(metaphytakingdom,multicellualr,photosynthetic)
 Animalia(metazoa kingdom,multicellular,digestive)
 Monerans(unicellualr)

3. 3 Domains
Eubacteria
true bacteria, peptidoglycan
Archaea
Prokaryotic, odd bacteria ,No peptidoglycan,
that live in extreme environments, high salt,
heat, methanogens (extremophiles)
Eukarya
have a nucleus & organelles (animals,
plants,fungi,protozoa,etc…..)
 1978, Carl R. Woes
 Differences in RNA, membrane lipid structure, sensitivity
to antibiotics

5. Bacteria
 Unicellular free living organisms without chlorophyll
 Having both DNA and RNA
 They are capable of performing all essential processes of life, e.g.
growth, metabolism and reproduction

6. Scientific nomenclature
 Binomial nomenclature.
 Genus name and specific epithet (species)
 Both names are printed underlined or italicized
 The genus name is always a noun and capitalized
 The species name is usually an adjective and lowercase
 e.g. Staphylococcus aureus, Bacillus anthracis, Escherichia coli
 OR S. aureus, B. anthracis, E. coli

7.  micron(μm)
 Varies with kinds age and external environment.
o Cocci: sphere, 1μm , e. g: Staphylococcus sp.( bunches of grapes),
Streptococcus sp.(chains), diplococci (forming pairs), tetrads and sarcina
o Bacilli: rods , 0. 2-0. 5 μm in width 2-10 μm in length, Brucella(coccobacilli)
e.g: Bacillus sp., Corynebacteria (Chinese letter arrangement), Vibrio (comma
shaped), Spirochaetes (spiral), Actinomycetes (branching filamentous ),
Size and shape of bacteria

8. Actinomycetes (branching filamentous ) Corynebacteria (Chinese letter arrangement),

9.  L form bacteria: Bacteria with defective cell wall either spontaneously
or as a result of drug, e.g. in presence of penicillin . Morphology is not
stable
e.g:Mycoplasma sp.(appear round with interlacing filaments)
 Pleomorphism: Some species of bacteria show great variation in shape
and size of undivided cell.
e.G :Haemophilus sp.
 Involution: Certain species show swollen aberrant forms in aging
cultures especially in presence of high salt concentration.
It may be due to defective cell wall synthesis. e.g : plague Bacillus
Size and shape of bacteria:

10. Pleomorphism of Haemophilus sp.
Mycoplasma pneumniae(L forms)

11.  PROTOPLAST and SPHEROPLAST formed due the action of
lysozymes on bacterial cell walls
 PROTOPLAST : gram positive bacteria lost part of the cell wall by
the action of lysozymes but not completely destroyed and remain
surrounded by cytoplasmic membrane
 SPHEROPLAST : gram negative bacteria lost part of the cell wall
by the lysozymes but maintain part of its outer membrane, cell wall
and cellular content.
 Both are spherical
 Associated with chronicity like in pyelonephritis.

12. Bacterial Anatomy

13. Gram-negative Cell Wall
Lipoprotein layer which connects outer
membrane to peptidoglycan.
Phospholipid bilayer containing specific
proteins that form porins
 Other proteins are target sites for phages,
antibiotics and bacteriocins.
Lipopolysaccharide consists of lipid A and
polysaccharide
Polysaccharide represents a major surface
antigen, the O antigen.
Lipopolysaccharide is the endotoxin of Gram-
negative bacteria

14. The space in between the inner and outer membranes
Contain proteins (such as enzymes and binding proteins for specific
substrates) and oligosaccharides (which play an important role in
osmoregulation of the cells).
Gram-negative Cell Wall
Periplasmic space

15. Gram-positive Cell Wall
Teichoic acids constitute major surface
antigens of Gram-positive bacteria.
Other components of Gram-positive cell
wall contain antigens such as the
polysaccharide and protein.

16. CELL WALL
Freely permeable to solute molecules
 Protects the internal structure
 Composed of mucopeptide (muerin)
 Confers rigidity and ductility (mucopeptide).
 Role in division of bacteria.
 Offers resistance to harmful effect of environment.
 Contains receptor sites for phages and colicin.
 Provides attachment to complement.

17. GLYCOCALYX
 Substances containing polysaccharides lying external to cell wall
 Slime layer and capsule
 Slime producing bacteria show mucoid growth on agar, e.g :
Klebsiella pneumoniae

18. Capsule
Gelatinous secretion of bacteria organized as a thick coat around cell wall
Capsulated bacteria are usually non motile
Microcapsule, thinner than true capsules e.g. Meningococci, Streptococcus
pyogenes and Haemophilus influenzae
It may be composed of complex polysaccharide (pneumococci and klebsiella) or
polypeptide (Bacillus anthracis) or hyaluronic acid (Streptococcus pyogenes
Protection against lytic enzymes.
 Virulent factor by inhibiting phagocytosis.
 Hapten elicit an immune response

19. Cytoplasmic membrane
 Consists of phospholipid with small amount of protein.
 Sterol is absent except in mycoplasma
 Controls inflow and outflow of metabolites
 Its permease selectively controls the passage of nutrients.
 Contains respiratory enzymes and pigments that manufacture the
substance of cell wall and extracellular structure.
 Provides little mechanical strength to bacterial cell.
 It helps DNA replication.

20. CYTOPLASM
 It does not exhibit internal mobility
 Lacks endoplasmic reticulum or mitochondria
 Contains ribosomes, mesosomes, inclusions and vacuoles.

21. Ribosomes
Sedimentation coefficient is 70 svedberg units(70S)
Sites of protein synthesis
Mesosomes
Invaginations of plasma membrane in the cytoplasm
 Prominent in Gram-positive bacteria
 Their function is not well known:
 Coordinate nuclear and cytoplasmic division during binary fission????!!!).
 Responsible for compartmenting DNA at sporulation????!!!

22. Intracytoplasmic Inclusions
Cytoplasmic granules
Glycogen (enteric bacillium)
polybetis hydroxybutyrate (bacillus and pseudomonas)
Babes Ernst (corynebacterium, Yersinia pestis).
Reserve of energy and phosphate for cell metabolism.
Carbon sources during protein and nucleic acid synthesis
 Convert excess H2S from environment into intracellular granules of element
sulfur.
Storage of lipids

23. NUCLEUS
Long filament of DNA inside the cytoplasm
Not surrounded by nuclear membrane
It does not have nucleolus.
Bacterial chromosome is haploid and replicates by simple fission
Plasmid or episomes
Extranuclear genetic material
 Transmitted to daughter cells during :
binary fission, conjugation and by bacterial phages
 They may confer certain properties like toxigenicity ,virulence and drug resistance

24. Bacterial Plasmid can be transmitted to daughter cells during binary fission

25. Bacterial Plasmid can be transmitted to recipient cell by conjugation

26. Bacterial phage

27. Fimbriae:
Hair like appendages, many
Involved in adherence and colonization
Biofilm formation
Pili:
Longer than fimbriae ,one or two/cell
For twitching motility : contact to surfaces or cells by pilin subunits e.g:Pseudomonas
aeruginosa
Gliding motility : movement in environment with low water content such as biofilms and
soil,e.g :Mycobacteria
Conjugation or Sex pili: transfer of genetic material like drug resistance

28. ENDOSPORES
Highly resistant dormant state of bacteria found in bacillus,
clostridium, sporosarcina (Gram-positive coccus) and Coxiella
burnetii (sporelike structures)
Not destroyed by ordinary methods of boiling for several
hours
Destroyed at autoclaving: ( 15 lb pressure per square inch at
121°C for 20 minutes)
They make survival of certain organisms possible under
unfavorable condition like dry state
Used as sterilization control mainly:
 Bacillus stearothermophilus is killed at 121°C in 15 to 30
minutes.
 Bacillus subtilis may be destroyed at105°C in 5 minutes.

29. BIOFILM
Thin slimy layer encasing single or diverse group of bacteria species adheres to a surface
 Irreversibly attached to biological or non biological surface(human tooth, mucous
membranes,etc…).
 Microorganisms are more resistant to traditional antibiotics inside it.
Protected from host defense mechanisms
Associated with chronicity and persistence of diseases
Nosocomial infections connected with use of central venous catheters, urinary catheters,
prosthetic heart valves, intraocular lenses and orthopedic devices are associated with
biofilms .
Staphylococcus epidermides; Staphylococcus aureus, Pseudomonas aeruginosa

30. Biofilm development.

31. Gram-positive Cell Wall vs Gram Negative Cell Wall

32. Study the Morphology of Bacteria
Optical Methods: motility, size, shape and arrangement of bacteria.
Light microscopy
Phase contrast microscopy
Dark ground microscopy
Fluorescence microscope
Electron microscope
 Polarization microscope
Autoradiography

33.  Gram’s Stain
 Acidic Acridine Orange Stain
 Albert Stain
 Ziehl-Neelsen Stain
STAINING OF BACTERIA

34. Gram in 1884
Study morphologic appearance of bacteria
Aid in diagnosis
Gram-positive organisms and Gram-negative organisms.
Gram-positive organisms are not decolorized and retain color of basic stain, e.g.
crystal violet
Gram-negative organisms lose cystal violet stainwhen treated with decolorizing
agent and take up the counter stain, e.g. dilute carbol fuchsin or safranin
Gram’s Stain

35. Gram’s Stain

36. Is also called acid-fast stain.
Some organisms retain carbol fuchsin even when decolorized with acid due
to mycolic acid present in their cell walls.
They are called acid-fast organisms.
Ziehl-Neelsen Stain

37.  Classification – ordering
*Kingdom
Phylum
Class
Order
Family
*Genus ( 1st name)
*Species ( 2nd name identifier)
Classification and Identification of Bacteria

38. Classification of Bacteria
 Morphology – size and shape arrangement , culture characteristics , spore
 Staining properties: Gram stain, Acid fast stain.
 Resistance: heat, antibiotics, disinfectants
 Metabolism: oxygen, need of carbon dioxide, pigment production, hemolysis
 Motility
 Bacteriophage typing
 Pathogenicity using laboratory animal models

39. END OF LECTURE