Extremophiles are Archaea adapted to extreme conditions (e.g., high salinity, temperature). Halophiles and methanogens are specific subsets, not general terms.

Delta proteobacteria (e.g., Desulfovibrio) oxidize H₂S for energy in anaerobic environments, unlike other Proteobacteria.

Amphitrichous bacteria have flagella at both poles; peritrichous (all over), lophotrichous (one pole), atrichous (none).

Chemosynthetic bacteria oxidize compounds like ammonia (nitrifying bacteria), nitrate, or ferrous sulfate for energy.

The log (exponential) phase is when bacteria divide rapidly, unlike lag (adaptation), stationary (balanced), or death (decline) phases.

Genetically engineered bacteria (e.g., E. coli with insulin genes) produce human insulin, not all Gram-positive or Gram-negative bacteria.

Bacterial flagella are composed of flagellin protein, unlike eukaryotic flagella (microtubules, tubulin).

Pili (fimbriae) facilitate attachment and DNA transfer during conjugation, unlike flagella (motility) or cilia (eukaryotic).

The nucleoid is the region in prokaryotes where the chromosome is located, not a true nucleus or ribosome-free zone.

Robert Whittaker proposed the Five Kingdom Classification (Monera, Protista, Fungi, Plantae, Animalia) in 1969.

Binary fission is the primary asexual reproduction method in bacteria, splitting one cell into two.

Gram-positive bacteria retain crystal violet due to thick peptidoglycan layers, unlike Gram-negative bacteria.

Griffith’s 1928 experiment showed that non-virulent Pneumococcus could transform into virulent forms via DNA uptake, not flagellar traits.

Thermophilic cyanobacteria (e.g., Synechococcus) can survive up to 85°C in hot springs, a trait of extremophiles.

Bacteria lack a nucleus, preventing mitosis (eukaryotic nuclear division); they reproduce via binary fission.

The prokaryotic cell wall, primarily peptidoglycan, forms a single sacculus, a complex molecular structure.

Cyanobacteria blooms (e.g., Anabaena) produce odors like ‘pigeon odor’ due to organic compounds.

Endospores are resistant structures formed by bacteria (e.g., Bacillus) to survive harsh conditions.

Peptidoglycan, made of sugars (N-acetylglucosamine) and amino acids, forms bacterial cell walls.

Peritrichous bacteria (e.g., E. coli) have flagella distributed over their entire surface.

Cyanobacteria (blue-green algae) contain phycocyanin, a phycobiliprotein, aiding photosynthesis.

High-temperature short-time (HTST) pasteurization heats milk at 71°C for 15 seconds to kill bacteria.

Rhizobium, a nitrogen-fixing bacterium, is classified as Alpha-proteobacteria.

Generation time is the duration between bacterial cell divisions, reflecting growth rate.

During the log phase, bacteria multiply rapidly, producing toxins or causing symptoms.

Endotoxins (lipopolysaccharides in Gram-negative bacteria) are released upon cell lysis (death).

Archaea have ether-linked lipids in their plasma membranes, unlike bacteria’s ester-linked lipids, aiding extremophile survival.

Rhizobium in root nodules converts atmospheric N₂ to ammonia via nitrogenase, enriching soil.

Sulfur bacteria (e.g., Beggiatoa) oxidize H₂S to sulfate, contributing to sulfur cycling in ecosystems.

Cyanobacteria (e.g., Anabaena) fix nitrogen in specialized cells called heterocysts, protecting nitrogenase from oxygen.

Cyanobacteria store energy as glycogen, unlike plants (starch) or animals (glycogen, but not prokaryotes).

Cyanobacteria, via photosynthesis, are the simplest organisms producing oxygen, unlike other bacteria or eukaryotes like Chlamydomonas.

Conjugation transfers plasmids (e.g., antibiotic resistance genes) via pili, increasing genetic diversity.

‘Arkhaios’ means ‘ancient’ in Greek, reflecting Archaea’s evolutionary age.

Antonie van Leeuwenhoek first described microorganisms as ‘animalcules’ in the 17th century using his microscopes.

Prokaryotes lack a nucleus and membrane-bound organelles but have a peptidoglycan (bacteria) or pseudomurein (Archaea) cell wall.

Prokaryotes (e.g., nitrogen-fixing bacteria, cyanobacteria) drive essential biogeochemical cycles, making life possible.

Approximately 10,000 prokaryote species are identified, though millions may exist, based on current microbiology data.

Prokaryotes diverged into Archaea and Bacteria, the two prokaryotic domains, distinct from eukaryotes.

Archaea differ from Bacteria in plasma membrane lipids (ether vs. ester), cell wall composition (pseudomurein vs. peptidoglycan), and extremophile adaptations.

Archaea thrive in extreme (e.g., hot springs) and moderate (e.g., soil) environments.

Extremophiles are Archaea adapted to extreme conditions; methanogens are a subset, not the general term.

Antextremophiles are Archaea in moderate environments, unlike extremophiles or methanogens.

Extremophiles include thermophiles (heat-loving) and halophiles (salt-loving), not cyanobacteria.

Methanogens (e.g., Methanococcus) thrive in anaerobic environments, producing methane.

Antonie van Leeuwenhoek, in the 1670s, first observed bacteria with his handcrafted microscopes.

Bacteria are the most abundant organisms, found in diverse environments, outnumbering plants or insects.

Proteobacteria (e.g., E. coli) are Gram-negative, with a thin peptidoglycan layer and outer membrane.

Chlamydia bacteria are Gram-negative, lacking significant peptidoglycan but with an outer membrane.

Alpha-Proteobacteria (e.g., Rhizobium) form symbiotic nitrogen-fixing relationships with legumes.

Delta-Proteobacteria (e.g., Desulfovibrio) oxidize H₂S in anaerobic respiration.

Beta-Proteobacteria (e.g., Nitrosomonas) oxidize ammonia to nitrates, aiding nitrogen cycling.

Gamma-Proteobacteria (e.g., E. coli) are diverse but not specifically tied to these roles; none fits perfectly.

Actinomycetes (e.g., Mycobacterium) cause leprosy and tuberculosis, not fungal diseases like Athlete’s Foot.

Mycoplasma lacks a cell wall, unlike cyanobacteria or spirochetes, making it resistant to some antibiotics.

Streptomyces produce antibiotics (e.g., streptomycin), widely used in medicine.

Cyanobacteria, through photosynthesis, produced oxygen, raising atmospheric levels over billions of years.

The glycocalyx is a loosely bound polysaccharide layer, unlike the tighter capsule.

Bacterial cell walls are made of peptidoglycan (also called murein), a sugar-amino acid polymer.

Leeuwenhoek’s handcrafted microscopes (up to 300x magnification) allowed the first observations of bacteria.

Gram-negative bacteria, with an outer membrane, are more resistant to antibiotics than Gram-positive bacteria.

Not all bacteria have a capsule; cell membrane, chromatin, and ribosomes are universal.

A bacterial flagellum has three parts: filament (flagellin), hook, and basal body.

Spirochetes (e.g., Treponema) range from 100–300 micrometers in length, typical for their helical shape.

Koch’s germ theory includes four postulates linking microbes to specific diseases.

Coccobacillus bacteria (e.g., Bordetella) are oval, resembling an egg, not springs or bats.

Sarcina is a cubical arrangement of 8 cocci; Staphylococcus is irregular clusters.

Streptobacillus refers to rod-shaped bacteria in chains; Staphylococci are grape-like clusters.

Cocci (e.g., Streptococcus) are typically non-motile and lack flagella, unlike spirilla or bacilli.

Flagella enable bacterial motility, allowing movement toward nutrients or away from toxins.

A flagellum consists of a filament (flagellin), hook (connects filament), and basal body (motor).

Some bacteria (e.g., Myxobacteria) use gliding motility, driven by surface protein secretions, not flagella.

Chemotaxis involves bacteria moving toward chemical attractants (e.g., nutrients) or away from repellents via flagellar rotation.