Bacterial Structure Flashcards
Explain the tree of life?
Carl Woese - organisms in 3 domains based on cell wall composition, cell membrane composition, & RNA sequence - bacteria, archaea, eucarya - close on tree=closely related
Explain prokaryotic cells?
1-10μm & simple - no membrane bound organelles, no microtubules, divide via binary fission, metabolically active, tolerant of extreme conditions, 70s ribosome, & single chromosome (no nuclear membrane)
Explain eukaryotic cells?
10-100μm, complex compartmentalised interior, mitotic cell division, aerobic respiration, photosynthesis, & fermentation only, 80s ribosome, linear chromosome enclosed in a nuclear membrane
Mention the morphologies and which ones are usually pathogenic?
Pathogenic - coccus, bacillus, spirillum, spirochete
Non-pathogenic - filamentous & appendaged bacteria (hyphae & stalks)
Explain different type of cocci bacteria & examples?
Cocci - round
Diplococci - duplicates once - Streptococcus pneumoniae
Streptococci - long chain in 1 direction - Streptococcus pyogenes
Tetrad - 4 cells - duplicate in x & y direction - Aerococcus
Sarcinae - 8 cells - duplicate in x, y, & z - Sarcina ventriculi
Staphylococci - duplicate in all directions - Staphylococcus aureus
Explain different types of bacilli and examples?
Single - bacillus subtilis
Diplobacilli - 2 bacilli duplicated & joined at end - Moraxella bovis
Streptobacilli - long chain - Streptobacillus moniliformis
Coccobacillus - short stubby rod - Haemophilus influenzae
Explain different types of Spirilla and examples?
Vibrio - arched rod - Vibrio cholerae
Spirillum - short spiraled - Helicobacter pylori
Spirochete - long spiraled - Treponema pallidum
Explain other shapes of bacteria and examples?
Filamentous - Candidatus
Star-shaped - Stella
Rectangular bacteria - Holoarcula
Pleomorphic (no cell wall & any shape) - Mycoplasma
Give an example of the size ranges of bacteria?
Smallest = Mycoplasma gallicepticum (200-300nm)
Average = E. coli (1-6μm)
Largest = Thiomargarita namibiensis - Namibia - (0.1-0.3mm but have reached 0.75mm)
What is the Glycocalyx?
Polysaccharide material outside of cell, capsule if attached - slime layer if not attached to cell
What is the lipopolysaccharide?
Gram - outer membrane - lipid A (endotoxin - embedded in membrane), core oligosaccharide, & O-antigen (highly variable & recognised by immune cells)
How do spirochetes move?
Axial filaments encased in Gram - outer membrane - rotates to give corkscrew-motility - penetration of viscous substrates & tissues
What are flagella?
Long thin structure made up of protein subunits (flagellin) - motile swimming(1 bacterium in fluid) & swarming(group over flat surface) - one end attached to cytoplasmic membrane - H+ ions cause the segment to spin & flagellum moves
Explain the different types of flagella?
Peritrichous - flagella arranged all over cell - move by bundling at one end - flagella pushed apart causing it to tumble
Polar monotrichous - 1 flagellum at end
Polar lophtrichous - multiple flagella at one end
How do polar reversible flagella work?
Changes rotation direction to change direction
How do unidirectional flagella work?
1 direction - cell stops & reorients to change direction
What are the bristle like fibres on cells called?
Fimnriae & Pili
What are Fimbriae?
Shorter than flagella & more numerous, made of proteins, not all bacteria, adhere to surfaces e.g. tissue
What are Pili?
Longer than fimbriae & less numerous, attachment to tissue, motility, & conjugation
Twitching Motility - propulsion of type IV pili - pilus extends & grab surface, retraction-motor for extension/retraction
Conjugation - conjugation pilus joins 2 cells & plasmid or piece of chromosomal DNA donated
What is the nucleoid?
DNA aggregated in dense area - no nuclear membrane - singular, circular double stranded DNA - (5 Mbp) - E. coli = circumference of 1.6mm must fit into 5μm cell - organised to enable transcription - supercoiling by gyrase & topoisomerase (50 supercoiled domains) - stabilised by structural proteins
Human genome size vs. E. coli genome size?
3.2 Gbp & 5 Mbp
What is a plasmid?
Circular double stranded DNA - not essential but beneficial - 1)resistance to antibiotics (Rbk of E. coli) 2)fertility - conjugation & DNA transfer (F of E. coli) 3)Killer - synthesis of toxins that kill other bacteria (Col of E. Coli for calicin production) 4) Degradation enzymes for metabolism of unusual molecules (TOL of P. putida for toluene metabolism)
What are bacterial ribosomes?
Translate mRNA into proteins - 10,000/cell - 70s ribosome = 30s subunit (16s rRNA & 21 proteins) & 50s subunit (23s rRNA, 5s rRNA, & 30 proteins) - used to identify bacteria
What does the s stand for in ribosomes?
Svedberg Unit - measure how quickly particles sediment in an ultracentrifuge
What are storage granules?
Vary in size, number, & content - energy storage & structural building blocks - poly-b-hydroxybutyrate (PHB) - contains glycogen, polyphosphate, iron oxide, or elemental sulfur
What are magnetosomes?
Aquatic prokaryote - intracellular inclusions of iron mineral magnetite (Fe3O4) - permanent magnetic dipole - orient themselves & migrate towards along geomagnetic field lines
What are gas vesicles?
Gas-filled structure made of protein - buoyancy - motility (position themselves in water for optimum light) - cyanobacteria
What are cyanobacteria most similar to?
Gram positive bacteria
What are crystalline inclusions
BT toxin - protein from Bacillus thuringiensis - transferred into corn - corn borer ingests protein - penetrates & collapse cell lining gut & insect dies
What is sporulation?
Production of endospore - cellular differentiation - >200 genes - terminal, subterminal, central
What is germination?
Endospores convert back to vegetative cells very quickly
What state are bacterial cells in favourable conditions?
Vegetative
What are endospores?
Form in inert forms - found in soil bacillus & clostridium genera - triggered by environmental distress e.g. nutrient starvation - resistant to heat, drying, freezing, radiation, & chemicals - survive for millions of years
Name some bacteria that form endospores?
Bacillus anthracis (anthrax)
Clostridium tetani (tetanus)
Clostridium botulinum (botulism)
