> See also: > - [[Non-Eukaryotic Cell Cycles]] # Environmental Factors Affecting Microbial Growth Microorganisms that thrive in harsh conditions are called **extermophiles** Osmophiles Halophiles: A microorganism that requires high levels of sodium chloride for growth In terms of an environment’s **nutrient availability**: - *Eutrophic Environments:* High in nutrients - *Oligotrophic Environments:* Low in nutrients In terms of pH - *Acidophiles* (0-5.5 pH) - Neutrophiles (5.5-8 pH) - Alkaliphiles (8-11.5 pH) In terms of temperature The cardinal temperatures of an organisms growth represent the minimum, optimum, and maximum. > [!question] Hypertonic vs Salt Concentration > > How does the tonicity of a solution related to the concentration of salt > - I know that in everyday life the addition of salt to something generally causes it to shrivel up which makes sense for hypertonic environments but I still feel like I’m missing something when trying to connect the two concepts (why salt specifically and not any other solute) ## Oxygen Tolerance > See also: [[Metabolism]] ![[Pasted image 20231003192427.png|400]] - *Obligate Aerobe:* Only grow in the presence of oxygen - *Microaerophile:* Require lower concentrations of oxygen (2-10%) - *Facultative Anaerobe:* Can grow with or without oxygen but grow faster in its presence - *Aerotolerant Anaerobe:* Grow well regardless of oxygen concentration - *Strict Anaerobe:* Only grow when no oxygen is present ## Temperature An organism’s optimal growth temperature is closest to its maximum growth temperature The distinct cardinal temperatures for a specific microbe include the minimum, optimum, and maximum growth temperatures ![[Pasted image 20231003182755.png|500]] - Psychrophiles: - Psychotolerants - Mesophiles - Thermophiles - Hyperthermophiles - Many species of [[Archaea]] are in this category, Adaptations at Low Temperatures Adaptations at High Temperatures: - ## Pressure piezophile barotolerant ## Radiation