3.3 Microbiology

Alcohol

________ removes the outer LPS membrane and because the peptidoglycan layer is thinner, it is more permeable and crystal violet washes out.

Gram Stain

________ is a quick test to give patients antibiotics very quickly.

Indirect Counts

________- Using turbidity (cloudiness) to estimate the number of bacteria.

Gram Positive

________- Deep Purple Colour, stains the thicker less permeable peptidoglycan.

Gram Negative

________- Pale Red Colour, stains the thinner more permeable membrane.

Single Sphere

Coccus (s), Cocci (P)

Chain of spheres

Streptococci

Bunch of Spheres

Staphylococci

Rod

Bacillus

Spiral

Spirillum

Gram Positive

Deep Purple Colour, stains the thicker less permeable peptidoglycan

Gram Negative

Pale Red Colour, stains the thinner more permeable membrane

Bacterial cell count

find out use by date, water contamination levels, adding cultures to milk & cheese

Viable

Living bacteria

Direct Counts

Counting the number of cells, can be either a viable count or a total count

Indirect Counts

Using turbidity (cloudiness) to estimate the number of bacteria

Viable Count

If we want to know the number of bacteria per cm^3

Viable cell count

Aseptic technique, count clumps,

Haemocytometer

Microscope slide with counting grids