Lakhasly

Microbiology o Microbiology: the study of organisms ??o Bacteria of medical importance

• 0.2 - 1.5 um in diameter
• 3 - 5 um in length Shape of Bacteria o Cocci - spherical/ oval shaped (major groups) o Bacilli - rod shaped o Vibrios - comma shaped o Spirilla - rigid spiral forms o Spirochetes - flexible spiral forms o Actinomycetes - branching filamentous bacteria.Cytoplasm - gel-like substance enclosed within the cell membrane contains cytoplasmic inclusions, ribosomes, mesosomes and nucleoid B. Additional structures - plasmid, slime layer, capsule, flagella, fimbriae (pili) and spores.o Microorganisms include: o ?Bacteria o ?Viruses o ?Fungi o ?Parasites {protozoa &helminthes (worms) } o ?Algae Antoni van Leeuwenhoek 1674.(father of microbiology)
• 1st person to actually see living microorganisms Cell Types There are several classes of living organisms Based on the organization of their cellular structures, all living cells can be divided into two categories: 1.Cells that do not have membrane-bound organelles
• called prokaryotic cells Eukaryotic cell types - Animals, plants, fungi, protozoa, and algae Prokaryotic cell types - Unicellular organisms such as bacteria and blue -green alga Similarities: both cell types are living cells o All cells are surrounded by a plasma membrane.o In an eukaryotic cell, chromosomes are contained in a membrane-enclosed organelle, the nucleus.Microorganisms are ubiquitous.Rigid cell wall 2.?2.3.4.5.6.7.8.

Microbiology
• Microbiology: the study of organisms 
too small to be seen without
magnification.
❖ Microorganisms are ubiquitous.
• Microorganisms include:
• Bacteria
• Viruses
• Fungi
• Parasites {protozoa &helminthes (worms) }
• Algae
Antoni van Leeuwenhoek 1674.(father of
microbiology)

• 1st person to actually see living microorganisms
  Cell Types
  There are several classes of living organisms
  Based on the organization of their cellular
  structures,
  all living cells can be divided into two categories:

1. Cell that have membrane-bound organelles
   – Called Eukaryotic Cells.


2. Cells that do not have membrane-bound
   organelles
   – called prokaryotic cells
   Eukaryotic cell types - Animals, plants, fungi,
   protozoa, and algae
   Prokaryotic cell types -
   Unicellular organisms such as bacteria and
   blue -green alga
   Similarities:
   both cell types are living cells
   • All cells are surrounded by a plasma membrane.
   • The semi-fluid substance within the cell
   Diffrences:
   A major difference between prokaryotic and
   eukaryotic cells is the location of
   chromosomes.
   • In an eukaryotic cell, chromosomes are contained
   in a membrane-enclosed organelle, the nucleus.
   • In a prokaryotic cell, the DNA is concentrated in
   the nucleoid without a membrane separating it
   from the rest of the cell.
   Prokaryotic Cells
   • Much smaller (microns) and more
   simple than eukaryotes.
   • Large surface-to-volume ratio :
   nutrients can easily and rapidly reach
   any part of the cells.
   Sizes of Bacteria
   • Unit of measurement in bacteriology is the
   micron / micrometre (µm).
   • Bacteria of medical importance

• 0.2 – 1.5 µm in diameter


• 3 – 5 µm in length
  Shape of Bacteria
  • Cocci – spherical/ oval shaped (major
  groups)
  • Bacilli – rod shaped
  • Vibrios – comma shaped
  • Spirilla – rigid spiral forms
  • Spirochetes – flexible spiral forms
  • Actinomycetes – branching filamentous
  bacteria.
  Gram positive cell wall
  • The Gram-positive cell wall is comp
  Anatomy of Bacterial Cell
  A. Outer layer - two components:

1. Rigid cell wall


2. Cell membrane or Plasma membrane
   present beneath cell wall.
   Cytoplasm - gel-like substance enclosed within the
   cell membrane contains cytoplasmic inclusions,
   ribosomes, mesosomes and nucleoid
   B. Additional structures - plasmid, slime layer,
   capsule, flagella, fimbriae (pili) and spores.
   Structure & Function of Cell Components
   CELL WALL:
   • Outermost layer, encloses cytoplasmic
   membrane


3. Confers shape and rigidity


4. Peptidoglycan is responsible for
   the rigidity of the bacterial cell
   wall and for the determination of
   cell shape.


5. Composed of Mucopeptide
   (peptidoglycan/ murein):
   • formed by N-acetyl glucosamine (NAG) &
   N-acetyl
   • muramic acid (NAM) alternating in chains,
   held by peptide bonds.


6. Can not be seen by direct light microscopy and do not
   stain with simple stains.


7. Carries bacterial antigens – important in virulence &
   immunity.


8. Chemical nature of the cell wall helps to divide bacteria
   into two broad groups – Gram positive & Gram negative .


9. Gram +ve bacteria have simpler chemical nature than
   Gram –ve bacteria.


10. Several antibiotics may interfere with cell wall synthesis
    e.g. Penicillin, Cephalosporins