5.1 : The Bacteria and Archaea PART 1

Bacteria

• procaryotic, unicellular organisms

• usuallydivide by binary fission

• Cell wall contains peptidoglycan

or mucopeptide

1.coccus or berry

2.bacillus or rod

3.spirillum or spiral

What are the three general shapes of bacteria?

Cocobacillus- rod isshort and

plump;

- Vibrio- gentlycurved

What are the two actual form of bacillus or rod?

Coccus/Cocci

length( 0.5 to 3 μm) in diameter

Diplococcus

Cocci by pair –

eg. Neisseria gonorrheae and D. salivarious

Streptococcus

Cocci in chain – eg. S. pneumoniae

Sarcinae

In cubical packets of eight - eg. S. ventriculi

Staphylococcus

• Cocci in irregular clusters – eg. S.

Rod shape: Bacillus

• 0.2 – 2.0 μm (W) by 0.5 – 20 μm (L)

• Occur as slender rod

eg. Salmonella typhi (typhoid fever)

• Rectangle with square ends as

anthrax Bacillus anthracis

• some are curved as Vibrio cholerae

• Most occur in single form or diplo

form and finally as chain

Spiral shape

• 0.2 – 2.0 μm (W) 0.5 – 100

μm (L)

• Twisted rod that resemble a

cork screw include:

• true spiral end curved

bacteria

eg. Spirochetes Treponema

pallidum (cause of syphilis) and

Leptospira (leptospirosis)

Actinomycetes/Actinobacteria

Actino means ray; mykes means fungi

Have elongated cells which have definite tendency to

branch to produce branched mycelium and multiply by

spores

• The cell structure is procaryotic like the proper bacteria

Streptomyces griseus

Streptomyces aureofaciens

Streptomyces norsei

What are the three examples of beneficial Actinomycetes?

Streptomyces griseus

– source of streptomycin antibiotic

Streptomyces aureofaciens -

source of tetracycline

antibiotic

Streptomyces norsei–

source

of Nystatin- an antifungal

agent

Appendages

structures that sprout from

surface of bacteria; not present in all species;

flagella and axial filaments

.those that provide motility

Fimbriae and pili

2.those that provide attachments or channels

Flagella/Flagellum

–confers motility or self-propulsion.

• may also function for detection and movement in

response to chemicals (chemotaxis) or light (phototaxis)

stimulus

• Generally all spirilla, about half of the bacilli and a small

number of cocci are flagellated

1.polar arrangement

flagella attached at one

or both ends of the cell

Peritrichous arrangement

flagella

dispersed over surface of the cell

atrichous

no flagella

Polar arrangement

Peritrichous arrangement

atrichous

What are the General Patterns of Bacterial

Flagellation?

monotrichous

lophotrichous

amphitrichous

In polar arrangement what are the three under in it?

monotrichous

with a single flagellum e.g.

Bdellovibrio at one end

lophotrichous

– with small bunches or tufts of flagella

emerging from the same site e.g. Vibrio fischeri

amphitrichous

– with flagella at both poles of

the cell

Periplasmic flagella or axial

filaments

a type of internal flagellum

enclosed between the cell wall and

cell membrane;

• The filaments curl closely around

the bacterium giving spirochetes

wriggly mode of locomotion

fimbriae/fimbria-

small, bristle-like fibers sprouting from

surface of many bacterial cells

have tendency to stick to each other and to surfaces

• enable the bacteria to bind to specific receptor structures and

thereby to colonize specific surfaces.

Pilus (sex pilus)

Elongate, rigid, tubular structure made up of protein called pilin

• Found only in Gram-negative bacteria

• Involved in the partial transfer of DNA from one cell to another

during conjugation

The Surface Coating

also known as glycocalyx

• made up of repeating polysaccharide units, protein or

both

• protects the cell or may cause it to adhere to its

environment

• differ among bacteria in thickness, organization

and chemical composition

Slime layer

Capsules

What are the two forms of glycocalyx?

1.slime layer

– thin, loose soluble sheath

- protects bacteria from loss of water and

nutrients

capsules

•Bound more tightly to the cell than the slime layer

•Protects bacterial cells from phagocytes

•Mycobacterium tubercolusis has thick capsule

which make them more resistant to drugs

Pleomorphic -

(only one species but with variable shape)