Lecture 2 & 3 Flashcards
(24 cards)
Thermophilic bacteria
Grow at > 50 degrees or above
Psychrotrophic bacteria
Grow at refrigeration temperature (<5 degrees)
Thermoduric bacteria
Able to survive pasteurisation
Halotolerant bacteria
Able to survive high salt concentration (>10 degrees)
Aciduric bacteria
Able to survive at low pH (<4)
Osmophilic bacteria
Able to grow at relatively high osmotic environment
Gas producing bacteria
Produce gas during metabolism of nutrients
Slime producers
Produce slime because of their ability to produce extracellular polysaccharides
Spore formers
Ability to produce spores e.g. bacillus sp
Aerobes
Require oxygen to grow
Anaerobes
Cannot grow in the presence of oxygen
Facultative anaerobes
Can grow both at the presence and absence of oxygen
Coliforms
Gram -ve, non-motile, facultative anaerobic bacterium. Usually associated with enteric system of mammals
Faecal coliforms
Coliforms strictly associated with enteric systems of mammals e.g. e.coli
Enteric pathogens
Pathogens of gastrointestinal tract of mammals
microbial growth: Binary division
- Duplication of chromosome
- Continued growth of cell
- Division into two cells
Microbial growth: Budding
- Mother cell
- Bud develops at one end
- Develop into new cells
- Growth of the cell
- New cells
Bacteria growth
- Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly towards the other end of the cell
- Replication continues. One copy of the origin is now at each end of the cell
- Replication finishes. Plasma membrane grows inward, and new cell wall is deposited
- Two daughter cells result
Fungi growth
Spores (asexual reproduction)
Viruses replication
- Attachment - the phage attaches to the surface of the host
- Penetration - the viral DNA enters the host cell
- Biosynthesis - phage DNA replicated and phage proteins are made
- Maturation - new phage particles are assembled
- Lysis - the cell lyses, releasing the newly made phage
Microbial growth curve
Lag phase, exponential growth phase, stationary phase, death phase
Kinetics of microbial growth; Biomass concentration
X (g/L or g/Kg) function of time
Kinetics of microbial growth; Growth rate
- Growth rate constant, u, is a function of the substrate concentration, S
- Um is the maximum growth rate (the rate at which the substrate concentration is not limiting)
Generation time
G = 0.3t / (Log10z - log10x)
G= generation time (min) or td(h) 0.3 = constant value of log102 (doubling) t = duration of the study (min/h) x = initial number of cells/biomass z = final number of cells/biomass
