Microbiology Vocabulary

Flashcards covering key vocabulary terms related to microbiology, including bacterial structures, classification methods, Gram staining, culture techniques, and bacterial growth measurement.

Cell wall

Made of murein (peptide and polysaccharide polymer-peptidogylcan). Prevents lysis under osmotic pressure and protects from damage

Cell/ plasma membrane

Selectively permeable, controlling the entry and exit of chemicals to the cell

Capsule

Composed of mucilaginous slime (sugars and water). Prevents dessication, water proofs the cell and allows it to stick to its host. It also protects the bacterium from other cells.

70s ribosomes

Synthesises proteins

Lipid droplets

Act as food reserves

Plasmids

Small circular pieces of DNA. These reproduce independently and consist of a handful of genes that may confer antibiotic resistance to the bacterium

Circular DNA loop

Possesses genetic information to control bacterial cell activities and allow for bacterial replication

Flagellum

Used to propel the cell through fluids

Bacillus

Rod-shaped bacteria

Coccus

Spherical bacteria

Spirillum

Spiral/corkscrew shaped bacteria

Diplo-

In pairs

Strepto-

Chain

Staphylo-

Cluster

Gram-positive

Positive phospholipid membrane, plus thick peptidoglycan cell wall

Gram-negative

Negative phospholipid membrane, thin peptidoglycan cell wall, additional lipopolysaccharide outer layer.

Crystal violet

Binds to peptidoglycan cell wall in Gram staining

Lugol's iodine

Binds crystal violet to peptidoglycan more strongly

Acetone-alcohol

Removes unbound crystal violet and lipopolysaccharide in Gram staining

Safranin

Stains Gram-negative bacteria red

Nutrient broth

Liquid medium for culturing bacteria

Nutrient agar

Solid medium for culturing bacteria

Defined medium

Contains only known ingredients

Undefined medium

Contains some unknown components

Selective medium

Only allows certain microorganisms to grow

Complete medium

Contains all the chemicals needed to support growth

Viable count

Counting living cells only

Total count

Describes dead and living cells

Colony (of microorganisms)

A cluster of cells (clone) which arises from a single bacterium or fungal spore by asexual reproduction

calculating population size

(number of colonies x dilution factor)/ volume of sample added to petri dish

problems with diluting sample too much

clumping = many colonies inaccurate count

diluting too much

too few to be statistically sound

how do u measure bacteria population with a colorimeter

light is passed through the culture and the percentage absorbance is measured. then a graph is plotted with light absorbance with the number of cells then an estimate is taken

is turbidimetry viable or total cell count

total cell count

conditions for culturing bacteria

nutrients

oxygen

temp

pH- alkaline

growth factors-ions magnesium,sodium, sulpate

obligate aerobes

can only survive in aerobic conditions

obligate anaerobes

can only survive in anaerobic conditions

facultative anaerobes

grow better in aerobic conditions but can survive in anaerobic conditions

how are gram positive bacteria affected by lysosome

lysosomes hydrolyses the hydrogen bonds holding peptidoglycan the cell wall together

how are gram positive bacteria affected by penicillin

penicillin prevents the formation of the bonds, weaking the cell wall causing osmotic damage and the leading to collapse of cell wall

why aren’t gram negative bacteria susceptible to antibiotics

they have an extra lipopolysaccharide layer which protects the cell wall and makes the resistant to lysosomes

describe the cell wall of gram positive bacteria

phospholipid layer and thick peptidoglycan layer

describe the cell wall of gram negative bacteria

phospholipid layer, thin peptidoglycan layer and a layer of lipopolysaccharide layer