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level: Level 1

Questions and Answers List

level questions: Level 1

1.Lag Phase 2.Log Phase 3.Stationary phase 4.Death phasePhases of Growth (4)
Bacteria are first introduced and ‘check out’ environment. Cells very metabolically active. Number of cells changes very little. 1 hour to several days.Lag phase
Rapid cell growth (exponential). Population doubles every generation. Microbes sensitive to adverse conditions.Log phase
Death rate=death of reproduction. Cells begin to encounter environmental stress (endospores would form now)Stationary phase
Death rate>rate of reproduction due to limiting factors in environment. Decline phase.Death phase
Lack of nutrients, water, space. Presence of metabolic waste. Oxygen and pHEnvironmental stress conditions
a resistant asexual spore that develops inside some bacteria cells.Endospores
pH, moisture content, oxidation-reduction potential, nutrient content, antimicrobial constituents, biological structures.Factors affecting growth (8)
Effects enzymes and nutrients. No know pathogen grows below pH 4.6pH
Most fresh foods Aw>0.99Moisture
Remove or bind waterHumectants
thrive in high salt conditionsHalophilic bacteria
tolerate high osmotic pressureModerate or facultative halophiles
require high osmotic pressureExtreme or obligate halophiles
-0.61. Can thrive in low AwXerophilic moulds
-0.83 Adapts to high salinityHalotolerant (haloduric)
0.61 Adapted to high sugar or high salt conditions- Osmophilic yeasts
Tolerant of high osmotic pressureOsmotolerant
0.86Lowest Aw for pathogen growth
the process in which cells lose water in a hypertonic solutionPlasmolysis
Ease at which the substrate loses of gains electronsOxidation/reduction potential
Cold loving. 0C-20CPsychrotrophs
Moderate temps. 20C-40CMesophile
Heat loving. 40C-100CThermophiles
Endure coldPsychroduric
Endure heatThermoduric
Needs oxygen for growthObligate aerobe
Oxygen required at levels below 0.2atmMicroaerophile
Can’t grow in presences of oxygenObligate anaerobe
Oxygen not required for growth but will be utilised if availableFacultative anaerobe
Not required and not utilisedAerotolerant anaerobe
Binary FissionGrowth and reproduction method