Introduction to Bacteriology

Bacteria are living forms that are

micro-scopical in size (1-10 µm) and

relatively simple, unicellular, in

structure.

1.Agriculture Bacteriology

2.Food Bacteriology

3.Industrial Bacteriology

4.Medical Bacteriology.

General Bacteriology

Prokaryote characters

Eukaryote vs. Prokaryote

Eukaryote vs. Prokaryote

•Like a warm, dark, and

moist environment

•They are found almost

everywhere:

–Water, air, soil, food

–Skin

–inside the body

–On most objects

•Prokaryote

•Mostly single-celled

•Circular single

chromosome

•Cell walls

•It reproduces by binary

fission, not by mitotic

division.

General Characteristic:

•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:

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

The bacterial structures may be divided into three categories:

B. Structures present

in some species :

1.Flagella

2.Spores

3.Inclusion granules.

A.Essential structures,

present in all bacteria

1.Protoplast (cytoplasm

and nuclear body)

2.Cytoplasmic membrane

3.Cell wall

1.Fimbriae

2.Sex pili

3.Glicocalix (capsule, microcapsule,

loose slime).

Structures present in some strains of some species:

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.

Shapes of Bacteria

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

Major Structures of a Bacteria Cell

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.

1.Archaebacteria: extremists

2.Eubacteria:

a)Heterotrophs

b)Photosynthetic autotrophs

c)Chemosynthetic autotrophs

Classification of Bacteria

1.Archaebacteria

•Live in extreme locations:

– Oxygen-free environments

– Concentrated salt-water

– Hot, acidic water

•Found everywhere

•Parasites: depend on other organisms

•Saprobes: depend on dead organisms or

waste (recyclers)

Eubacteria - Heterotrophs

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

•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

Reproduction of Bacteria

•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)

20

Bacterial Cell & Nucleiod DNA Ring

DNA replication

Cell wall synthesis

Cell separation

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

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

Bacteria Survival – Food sources

Harmful Bacteria

•some bacteria cause diseases

•Animals can pass diseases to humans

Disease passed from one organism to another

This can happen in several ways:

•Air

•Touching clothing, food, or toothbrush

•Drinking water that contains bacteria

Communicable Disease –

•Paired: diplo

•Grape-like clusters:

staphylo

•Chains: strepto

Bacterial Arrangement