Microbiology

Prokaryotes

• No membrane bound organelles
• No membrane bound nuceleus
• Smaller ribosomes than eukaryotes
• Cell wall made up of peptidoglycan
• 0.5-5 micrometers
• Reproduce by binary fission

Gram Positive Bacteria

• Thick layer of peptidoglycan
• Stains purple when crystal violet is added
• Penicillin is effective against them

Gram Negative Bacteria

• Thin layer of peptidoglycan and a thick layer of lipopolysaccharide 
• Stains red because of the counter stain Safrinin
• Penicillin is not effective against them

Nutrients needed for Microbes

• Carbon - Usually organic e.g. glucose energy source
• Nitrogen - Inorganic (nitrate) or organic (amino acids)
• Inorganic ions - Growth factors
• Vitamins - Growth factors

Types of Antibiotics

• Bacteriostatic - Agents/chemicals that stop the growth and division of the bacteria by inhibiting protein synthesis or by inhibiting replication of DNA.
• Bacteriocidal - Chemicals/drugs that kill bacteria by breaking down the cell membrane or by stopping the formation of the cell wall.

Counting Bacteria

• Viable cell count - counting living cells only by serial dilution
• Total cell count - counting living and dead cells by using a haemocytometer or turbidity using a colorimeter

Biotechnology

• The industrial use of living organisms to produce food, drugs or other commercial products
• Drugs synthesised by microbes include antibiotics and insulin
• Microbes are also used to synthesise biofuels and the enzymes added to biological washing powders

Growth of microbes in a closed culture

• Bacteria divide by binary fission
• The time taken for the population to double is the generation time

Types of culture

• Batch culture
• Continuous culture

Population Growth

Population: a group of organisms if a single species, interbreeding and occupying a paticular area

Species: a group of organisms which share a large number of common characteristics and which can interbreed to produce fertile offspring

Population numbers…