Download Chapter2 INTRODUCTION TO BACTERIOLOGY

Introduction to Bacteriology
Bacteria are living forms that are
micro-scopical in size (1-10 µm) and
relatively simple, unicellular, in
structure.
General Bacteriology
1.Agriculture Bacteriology
2.Food Bacteriology
3.Industrial Bacteriology
4.Medical Bacteriology.
Prokaryote
characters
Eukaryote
vs. Prokaryote
General Characteristic:
•Prokaryote
•Like a warm, dark, and
moist environment
•Mostly single-celled
•They are found almost
•Circular single
everywhere:
chromosome
–Water, air, soil, food
•Cell walls
–Skin
•It reproduces by binary
fission, not by mitotic
division.
–inside the body
–On most objects
•Reproduce mostly asexually
•Anaerobic or aerobic : depending on the
species, bacteria can be aerobic which means
they require oxygen to live or anaerobic which
means oxygen is deadly to them .
•Bacteria can be autotrophs or heterotrophs
•Depend on the Gram staining (or Gram's
method) which is an practical method of
differentiating bacterial species based on the
chemical and physical properties of their cell
walls Bacteria can be classified into two
types: Gram Positive Bacteria and Gram
Negative Bacteria
•The Gram stain, which divides most clinically
significant bacteria into two main groups, is the first
step in bacterial identification.
•Bacteria stained purple are Gram + (positive) their cell
walls have thick petidoglycan and teichoic acid.
•Bacteria stained pink are Gram – (Negative) their cell
walls have thin peptidoglycan and lipopolysaccharides
with no teichoic acid.
Bacterial Structures:
The bacterial structures may be divided
into three categories:
A.Essential structures, present in all bacteria
B.Structures present in some species
(primary taxonomic characters)
C.Structures present in some strains of some
species
A.Essential structures,
B. Structures present
present in all bacteria
in some species :
1.Protoplast (cytoplasm
1.Flagella
and nuclear body)
2.Spores
2.Cytoplasmic membrane
3.Inclusion granules.
3.Cell wall
Structures present in some strains of
some species:
1.Fimbriae
2.Sex pili
3.Glicocalix (capsule, microcapsule,
loose slime).
Shapes of Bacteria
Bacteria have different shapes.
1. Coccus: The cocci are spherical or oval bacteria e.g.
staphylococcus, diplococcus; two cells together
2. Rod-shaped bacterium or Bacillus, e.g Escherichia
coli.
3. The spiral: Spirals come in one of three forms, a
vibrio, a spirillum, or a spirochete.
Major Structures of a Bacteria Cell
Nucleoid
 A ring made up of DNA
 No real complete nucleus
Cytoplasm
 Clear jelly-like material that makes up most of the
cell
Capsule
 keeps the cell from drying out and helps it stick to
food or other cells
 Cell wall
Thick outer covering that maintains the overall shape of
the bacterial cell
 Ribosomes
Ribosomes give the cytoplasm of bacteria a granular
appearance and it is where proteins are made
 Flagella
A whip-like tail that some bacteria have for movement
 Pilli
Heavy hair-like structures made of protein
Allows bacteria to attach to other cells.
Classification of Bacteria
1.Archaebacteria: extremists
2.Eubacteria:
a)Heterotrophs
b)Photosynthetic autotrophs
c)Chemosynthetic autotrophs
1.Archaebacteria
•Live in extreme locations:
– Oxygen-free environments
– Concentrated salt-water
– Hot, acidic water
Eubacteria - Heterotrophs
•Found everywhere
•Parasites: depend on other organisms
•Saprobes: depend on dead organisms
or waste (recyclers)
a.Eubacteria: Photosynthetic Autotrophs
1.Photosynthetic: make their own food from light
2.Cyanobacteria: blue-green, yellow, or red
3.Ponds, streams, moist areas
a.Eubacteria: Chemosynthetic Autotrophs
1.Get energy by breaking down inorganic substances like
sulfur and nitrogen
2.Make nitrogen in the air usable for plants
Reproduction of Bacteria
•Bacteria are multiply by a simple cell division
known as binary fission (splitting into two). The
single piece of DNA reproduces itself exactly.
•When bacterial species produce several forms
each with its own characteristics, these variants are
called strains.
•Growth depends on temperature, pH, osmotic
pressure, oxygen, and nutrients
•In the Binary Fission- the process of one
organism dividing into two organisms
•Fission is a type of asexual reproduction
•It is Asexual reproduction- reproduction of
a living thing from only one parent
•The one main (circular) chromosome makes
a copy of itself
•Then it divides into two
•The time of reproduction depends on how
desirable the conditions are
•Bacteria can rapidly reproduce themselves in
warm, dark, and moist conditions
•Some can reproduce every 20 minutes, one
bacteria could be an ancestor to one million
bacteria in six hours)
Bacterial Cell &
Nucleiod DNA Ring
DNA replication
Cell wall synthesis
Cell separation
20
Bacteria survival
Endospore-
• A thick celled structure that forms inside the cell
• They are the major cause of food poisoning
• Allows the bacteria to survive for many years
• They are highly resistant structures, which can withstand
boiling, freezing, and extremely dry conditions
• It encloses all the nuclear materials and some cytoplasm
Bacteria Survival – Food sources
1.parasites – bacteria that feed on living things
2.saprophytes – use dead materials for food (exclusively)
3.decomposers :
•get food from breaking down dead matter into simple
chemicals
•important- because they send minerals and other materials
back into the soil so other organisms can use them
Harmful Bacteria
• some bacteria cause diseases
• Animals can pass diseases to humans
Communicable Disease –
Disease passed from one organism to another
This can happen in several ways:
• Air
• Touching clothing, food, or toothbrush
• Drinking water that contains bacteria
Bacterial Arrangement
•Paired: diplo
•Grape-like clusters:
staphylo
•Chains: strepto