Domain Bacteria

Cell type: Prokaryotic

Cell wall: Peptidoglycan while

some have another outer

layer called a capsule.

Domain Bacteria

Mode of Nutrition:

autotrophs or heterotrophs

Reproduction: usually

asexual (if stressed, sexual)

Habitat: VERY diverse

(ubiquitous)

Domain Bacteria

Some bacteria form an

endospore to protect

them from environmental

stresses (low food, etc.).

When the situation

becomes better, they

reanimate and become

normal bacteria again.

Domain Bacteria

Some bacteria form an

endospore to protect

them from environmental

stresses (low food, etc.).

When the situation

becomes better, they

reanimate and become

normal bacteria again.

Domain Bacteria

How will we

identify them?

Bacterial Shapes

10

Spiral:Spirilla (spirillum)

rod-shaped:bacilli (bacillus)

Round:cocci (coccus)

Bacterial forms

diplococcus

streptococcus

staphylococcus

The Gram Stain

The Gram stain, which divides most clinically

significant bacteria into

two main groups, is

useful in bacterial

identification.

The Gram Stain

Bacteria stained purple

are Gram +. Their cell

walls have a thick

peptidoglycan layer.

The Gram Stain

Bacteria stained pink are

Gram -. Their cell walls

have a thin peptidoglycan

layer and

lipopolysaccharides.

Is this gram stain positive or negative?

Identify the bacteria.

Is this gram stain positive or negative? Identify the bacteria.

Importance of Bacteria

Bacteria colonise every environment on earth.

More than 80% of life’s history was bacterial.

You have millions of bacterial cells in your body!.

The average human gut contains about 1

kg of bacteria. Of these, approximately

0.1% are normally E. coli.

Bacteria Growing on Agar Plate

Importance of Infection

• Decisive role in history

• Still major cause of death and misery worldwide

• Public anxieties

–Meningitis, Food poisoning

–Emerging infections

• Hospital Infection

–Antibiotic-Resistant Superbugs