🦠 Microbiology

Microorganisms

Living things too small to see without a microscope, including bacteria, archaea, protists, fungi and microscopic algae.

Bacteria

Single-celled prokaryotes found everywhere, vital for nutrient cycling, digestion and some disease.

Archaea

Prokaryotes distinct from bacteria, often thriving in extreme environments like hot springs and salt lakes.

Bacterial Shapes

Cocci are spherical, bacilli are rod-shaped and spirilla are spiral.

Gram Staining

A staining technique that divides bacteria into Gram-positive and Gram-negative by cell wall structure.

Binary Fission

Asexual reproduction in which a bacterial cell copies its DNA and splits into two identical cells.

Fungi

Eukaryotic organisms with chitin cell walls that absorb nutrients, including yeasts, moulds and mushrooms.

Yeast

A single-celled fungus used in baking and brewing that ferments sugars into carbon dioxide and ethanol.

Protists

A diverse group of mostly single-celled eukaryotes such as amoebae, paramecia and algae.

Algae

Photosynthetic protists and plant-like organisms that produce a large share of the world's oxygen.

Probiotics

Live beneficial microbes that, in adequate amounts, support gut health.

Fermentation

Anaerobic breakdown of sugars producing products like lactic acid or ethanol, used in yogurt and bread.

Pathogens

Disease-causing microorganisms, including some bacteria, viruses, fungi and protozoa.

Sterilisation and Aseptic Technique

Methods that eliminate contaminating microbes so cultures and procedures stay pure.

Intermediate topics (19)

Growth Curve

A graph of bacterial number over time with lag, log, stationary and death phases.

Culture Media

Nutrient mixtures, liquid or agar, designed to grow microorganisms in the laboratory.

Selective and Differential Media

Selective media favour certain microbes; differential media show visible differences between them.

Bacterial Cell Wall

Peptidoglycan gives bacteria shape and strength; Gram-negative species add an outer membrane.

Bacterial Flagella and Pili

Flagella propel cells while pili attach to surfaces and transfer DNA during conjugation.

Endospores

Dormant, highly resistant structures produced by Bacillus and Clostridium to survive harsh conditions.

Bacterial Genetics

Bacteria change genetically through mutation and by exchanging DNA by transformation, transduction and conjugation.

Plasmids

Small circular DNA molecules in bacteria that often carry genes for antibiotic resistance.

Conjugation

Direct transfer of DNA, such as a plasmid, between bacterial cells through a pilus.

Transformation and Transduction

Uptake of free DNA from the surroundings, or transfer of DNA between bacteria by bacteriophages.

Antibiotics

Drugs that kill or inhibit bacteria, such as penicillin, which blocks cell wall synthesis.

Bacterial Metabolism

Bacteria are aerobes, anaerobes or facultative, and may be phototrophs or chemotrophs.

Nitrogen-Fixing Bacteria

Rhizobium and others convert atmospheric nitrogen into ammonia for plants.

Cyanobacteria

Photosynthetic bacteria that oxygenated Earth's atmosphere billions of years ago.

Fungal Reproduction

Fungi reproduce by spores, sexually or asexually, dispersed through the air.

Lichens

A mutualistic partnership between a fungus and an alga or cyanobacterium.

Mycorrhizae

Symbiosis between fungal hyphae and plant roots that improves nutrient and water uptake.

Protozoan Parasites

Single-celled eukaryotes such as Plasmodium and Trypanosoma that cause malaria and sleeping sickness.

Microbiome

The community of microorganisms living in and on a host, such as the human gut.

Advanced topics (21)

Biofilms

Structured communities of microbes embedded in a self-made matrix, resistant to antibiotics and immune attack.

Quorum Sensing

Bacteria release and detect signalling molecules to coordinate behaviour as population density rises.

Antibiotic Resistance Mechanisms

Bacteria resist drugs by enzymes like beta-lactamase, efflux pumps, altered targets and reduced uptake.

Two-Component Systems

Sensor kinase and response regulator pairs that let bacteria sense and respond to environmental changes.

Bacterial Chemotaxis

Cells bias a random walk toward attractants by controlling flagellar rotation through CheY.

Extremophiles

Organisms thriving in extremes of heat, acidity, salt or pressure, with specialised enzymes.

Thermophilic Enzymes

Heat-stable enzymes such as Taq polymerase from Thermus aquaticus enable PCR.

Metagenomics

Sequencing DNA directly from environmental samples to study unculturable microbial communities.

16S rRNA Sequencing

Comparing a conserved ribosomal gene to identify and classify bacteria and archaea.

Microbial Consortia

Cooperating microbial communities divide metabolic labour, as in syntrophic methane production.

Bacterial Secretion Systems

Protein machines types I to IX that export toxins and effectors across bacterial envelopes.

Toxins

Exotoxins are secreted proteins and endotoxins are lipopolysaccharide parts of Gram-negative walls that cause disease.

Methanogenesis

Archaea produce methane anaerobically from carbon dioxide and hydrogen or acetate.

Chemolithotrophy

Microbes obtain energy from oxidising inorganic compounds such as hydrogen sulfide or ammonia.

Gut-Brain Axis

Bidirectional communication between gut microbes and the nervous system via metabolites, immune and vagal signals.

Phage Therapy

Using bacteriophages to treat bacterial infections, especially those resistant to antibiotics.

Synthetic Microbiology

Engineering microbes with designed genetic circuits for medicine, industry and the environment.

Bioremediation

Using microbes to degrade or neutralise pollutants like oil spills and heavy metals.

Fungal Pathogens

Fungi like Candida and Aspergillus cause infections, particularly in immunocompromised people.

Microbial Taxonomy

Classification of microbes using phenotypic traits, rRNA and whole-genome similarity.

Horizontal Resistance Spread

Mobile genetic elements such as integrons and transposons rapidly distribute resistance across species.