BRAINCAKEBacteria and Disease
Revision notes for Bacteria and Disease in Edexcel Biology B (9BI0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.
- Culturing MicroorganismsMicroorganisms such as bacteria and fungi can be grown in the laboratory in a culture medium, a mixture that supplies everything they need to grow…
- Aseptic Culture TechniquesAseptic technique is a set of procedures that prevents unwanted microorganisms contaminating a culture, and stops the cultured microorganisms…
- Selective MediaMany samples contain a mixture of microorganisms.
- Growing a Pure CultureA pure culture contains only one species (or strain) of microorganism.
- Counting the Number of CellsMicrobiologists often need to know how many cells are in a culture, for example to follow its growth over time.
- TurbidityAs bacteria multiply in a liquid broth, the broth becomes cloudy, or turbid.
- Dilution PlatingDilution plating gives a viable count: it counts only cells that are alive and able to divide.
- Area and Mass of FungiMoulds such as Penicillium grow as long, branching threads called hyphae, which form a tangled network called a mycelium.
- Growth of Bacterial ColoniesWhen bacteria are put into fresh nutrient broth in a closed culture (no nutrients added and no waste removed), the population follows a typical…
- Logarithmic ScaleBacterial populations can grow from a few hundred cells to billions in a day.
- Exponential GrowthBacteria reproduce by binary fission: one cell divides into two.
- Bacterial ToxinsPathogenic bacteria cause disease in two main ways: by invading and damaging host tissues, and by producing toxins.
- EndotoxinsEndotoxins are lipopolysaccharides (LPS): molecules made of a lipid part joined to a chain of carbohydrate.
- Salmonella spp.Salmonella species are rod-shaped, Gram-negative bacteria.
- ExotoxinsExotoxins are soluble proteins made by living bacteria and secreted into their surroundings.
- Staphylococcus spp.Staphylococcus species are Gram-positive, spherical bacteria (cocci) that grow in grape-like clusters.
- Host Tissue InvasionTo cause disease, many bacteria must first enter the body and invade host tissues.
- Mycobacterium tuberculosisMycobacterium tuberculosis is the rod-shaped bacterium that causes tuberculosis (TB).
- AntibioticsAn antibiotic is a chemical that kills bacteria or inhibits their growth, without harming the cells of the host.
- Broad-spectrum, Narrow spectrum, Bacteriostatic and BactericidalAntibiotics can be described in two separate ways: by the range of bacteria they act on, and by what they do to the bacteria.
- AntimetabolitesAn antimetabolite is a substance that interferes with a normal metabolic pathway, usually because it has a similar shape to one of the pathway's…
- Protein synthesis InhibitorsBacteria have 70S ribosomes, made of a small 30S subunit and a large 50S subunit.
- Cell Wall AgentsBacterial cells are surrounded by a cell wall made of peptidoglycan (murein): long polysaccharide chains held together by short peptide cross-links.
- Cell Membrane AgentsThe cell membrane (plasma membrane) of a bacterium controls what enters and leaves the cell.
- DNA Gyrase InhibitorsBacterial DNA is a long, circular molecule packed into a small cell.
- Antibiotic ResistanceAntibiotic resistance means that an antibiotic no longer kills or inhibits the growth of a bacterium at the doses normally used.
- Creating Drug-Resistant BacteriaAntibiotics do not cause resistance mutations, but they select for bacteria that already carry them.
- MRSAMRSA stands for methicillin-resistant Staphylococcus aureus.
- Clostridium difficileClostridium difficile (often called C. difficile or C. diff) is a Gram-positive, rod-shaped, anaerobic bacterium that forms spores.
- Prevention and Control of InfectionHospitals have strict codes of practice to prevent and control healthcare-associated infections (HCAIs), such as MRSA and C. difficile.
On the specification
- 6.1 Microbial techniques
- 6.2 Bacteria as pathogens
- 6.4 Antibiotic resistance