Basic microbiology

Question 1

What does nomenclature depend on?

Answer 1

Nomenclature depends on species specific typing so…

E. coli O157:H7

S. pyogenes M3T3

‘O’ antigen
‘H’ antigen

M protein
T protein

Question 2

Describe the shapes of bacteria

Answer 2

Round - ‘coccus / cocci’
e.g Streptococcus sp,
Enterococcus sp

Long – ‘bacillius / bacilli’
E.g. Enterobacter sp.

A few are spiral / branched (filamentous), comma shaped

Question 3

Discuss the practice of gram staining

Answer 3

Depends primarily on the amount of peptidoglycans in bacterial cell wall

In practice
Dry on glass plate

Stain with ‘crystal violet’ and set with iodine

Decolourise with alcohol

Counterstain with safranin (pink colour)

Gram positive- Purple
Gram negative- Pink

Question 4

Discuss bacterial growth

Answer 4

Bacteria may grow in chains or clusters
Especially important for Gram positive cocci

Different requirements for growth
Atmosphere
Nutrients

Different patterns of growth
Down the microscope
Form chains / clusters

On solid culture medium
Form colonies – different sizes / shapes
Excrete enzymes, waste products etc into environment