Flashcards in L3 The Prokaryotic Cell Deck (8):
What are the main distinguishing features of pro- and eukaryotic cells? Give a microbial example of each.
(1) DNA not enclosed in a membrane; circular chromosome (usually one)
(2) No organelles
(3) Most have cell walls made from peptidoglycan (or similar) or protein
(4) Simple morphological structure
e.g. Bacteria, archaea
(1) DNA enclosed in membrane-bound nucleus' multiple linear chromosomes
(2) Have organelles (mitochondria, golgi bodies, endoplasmic reticulum, chloroplasts)
(3) If present, cell walls do not contain peptidoglycan
(4) Complex morphological structure
e.g. Fungi, algae, protozians
Name the main bacterial shapes.
- Coccus (or sphere): can be single, pairs/diplococci, chains, clusters
- Bacillus (or rod): can be rectangular, have pointed ends, chains
- Filamentous, rigid spirals, flexible spirals, comma- shaped rods, pleiomorphic (variable)
Name the main bacterial structures and their functions.
- Plasma membrane: selectively permeable barrier, boundary of cell, nutrient and waste transport, respiration
- Cell wall: gives cell shape and protection
- Ribosomes: protein synthesis
- Nucleoid: location of DNA, single chromosome
- Capsules and slime layers: resistance to phagocytosis, adherence to surfaces
- Fimbriae/pili: adherence to surfaces, DNA transfer (sex pili), twitching and gliding motility (type IV pili)
- Flagella: swimming and swarming motility
- Endospore: survival under harsh conditions
How do bacteria grow?
By a process called "binary fission"
(1) Cell enlarges and chromosome replicates
(2) Septum begins to grow, chromosomes and other cytoplasmic components move to opposite ends
(3) Septum completely synthesised, 2 separate cell chambers
(4) 2 daughter cells separate completely or remain attached to form chains, doublets etc
What are the factors that influence bacterial growth? Describe the different bacterial groups for each factor.
- Obligate aerobe* (needs O2 for growth and respiration)
- Facultative anaerobe* (doesn't need O2 but grows better in its presence)
- Obligate anaerobe* (killed by O2, may gain energy by fermenting sugars)
- Mesophile* (moderate temp, functions between 15-45C but optimal 20-45)
- Psychrophile (cold temp, -5-20C)
- Thermophile (hot temp, 40-80C)
- Hyperthermophile (extremely hot temp, 65-113C)
* Bacterial pathogens members of these groups
What are the 2 common methods of growing bacteria in the laboratory?
(1) Liquid culture: bacteria grown as a liquid suspension ("broth culture")
(2) Solid culture: bacteria grown on an agar (gel) surface ("plate culture"), bacteria form colonies of characteristic size and appearance
Define the terms "species" and "strain" in relation to bacteria.
Species = a collection of strains that share many stable properties and differ from other groups of strains
Strain = populations derived from single cells; descendants of a single, pure microbial culture. Strains differ slightly between each other, e.g. antibiotic R or S