Microbial Growth Pt1 0.0 / 5 ? BiologyMicrobiologyUniversityNone Created by: georgia160502Created on: 13-04-22 14:19 What are the factors affecting microbial growth? Temperature pH Aeration Moisture content Presence of inhibitory substances 1 of 31 What type of microorganisms can grow at -5-20 degrees Psychrophiles 2 of 31 What type of microorganisms can grow at 15-45 degrees Mesophiles 3 of 31 What type of microorganisms can grow at 42-80 degrees Thermophiles 4 of 31 What type of microorganisms can grow at 75-105 degrees Hyperthermophiles 5 of 31 What type of microorganisms can grow at pH 1-4 Acidophile 6 of 31 What type of microorganisms can grow at pH 8-12 Alkaliphile 7 of 31 What group of microorganisms tend to be more acid-tolerant Fungi 8 of 31 What type of microorganisms only grow in the presence of oxygen Obligate aerobes 9 of 31 What type of microorganisms only grow in the absence of oxygen Obligate anaerobes 10 of 31 What do obligate anaerobes use as a substitute for oxygen? Nitrogen 11 of 31 What type of microorganisms grows in the presence of oxygen but can switch their metabolic pathway and grow if there is an absence of oxygen? Facultative anaerobes 12 of 31 What type of microorganisms can grow at any concentration of oxygen Aerotolerant anaerobes 13 of 31 Why is CO2 an important factor? pH changes Inhibitory at high concentrations 14 of 31 What does water availability depend on? Absolute water content of the environment Concentration of solutes e.g. salt 15 of 31 What is water availability expressed as? Water activity (aw) 16 of 31 What is water activity? The relationship between the moisture content of the substrate and the relative humidity of the air surrounding it 17 of 31 What are the survival structures in fungi? Spores 18 of 31 What are the survival structures in bacteria? Spores and cysts 19 of 31 What are the population growth phases? Lag phase Exponential phase Stationary Phase Death phase 20 of 31 What is the phase that lies between the exponential and stationary phase called? Deceleration phase 21 of 31 What forms during the deceleration phase? Survival structures 22 of 31 Why do fungi produce spores? Survival Dispersal 23 of 31 What are the two main types of spore? Sexual Asexual 24 of 31 What are sexual spores? Thick-walled Resistant to unfavourable environmental conditions 25 of 31 What are asexual spores? Produced in large numbers for dispersal Low resistance to unfavourable conditions 26 of 31 What are the two genera of Gram-positive bacteria that can form endospores inside vegetative cells? Bacillus Clostridium 27 of 31 What is a vegetative cell? A growing cell 28 of 31 What do endospores do? Withstand extreme conditions of desiccation Remain viable in a metabolically inactive state And then germinate when conditions become favourable 29 of 31 What compound do endospores have large amounts of? Calcium dipicolinate 30 of 31 What is a bacterial cyst? Modified vegetative cell Develops a thick chemically and physically resistant cell wall 31 of 31
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