Nucleoid
Folded DNA with proteins; no nuclear envelope.
Biology here means energy and envelope. A cell must keep water balance, copy DNA and harvest electrons from light, food or minerals.
Endospores in Bacillus and Clostridium are survival bunkers, not a 'reproduction method' in the everyday sense.
Parts
Ribosomes (70S)
Protein factories; some antibiotics bind here and spare our 80S ribosomes.
Plasma membrane
Electron transport lives here ? bacteria have no mitochondria to outsource to.
Cell wall
Gram-positive thick mesh vs Gram-negative thin mesh plus outer membrane.
Flagella / pili
Motors and grappling hooks for swimming, sticking and some gene transfer.
Plasmids
Optional extra circles. Clinically famous when they carry resistance cassettes.
Life cycle
1Growth lag
Cells sense the new buffet and switch enzymes on.
2Exponential
Regular doubling while food and space last.
3Stationary
Death balances birth; stress programmes start.
4Decline or spore
Some die; some bunker as spores until conditions return.
When headlines say a bacterium 'mutated', they usually mean selection on a huge population, not a cartoon villain changing costume.
Keep exploring
More in Tree of microbes
Viruses
Packets of DNA or RNA that are not cells — they replicate only inside living hosts.
Familiarity 96Fungi
A eukaryotic kingdom of yeasts, moulds and mushrooms — chitin walls, external digestion, partners of plants.
Familiarity 80Archaea
A prokaryotic domain that is not bacteria — methanogens, extremophiles and no known human pathogens.
Familiarity 35Bacteriophages
Viruses that infect bacteria — Earth's most abundant biological entities, and a concept-level idea in medicine.
Familiarity 42Protozoa
Motile unicellular eukaryotes — a teaching grade that includes pond ciliates and a minority of serious parasites.
Familiarity 58