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Lecture 14

MBIO 1010 Lecture 14: Lecture 14

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University of Manitoba
MBIO 1010
Christopher Rathgeber

Microbiology 1010 – Lecture Notes Temperature Classes of Microorganisms (Continued…) Mesophiles: organisms that have midrange temperature optima; found in o Warm-blooded animals o Terrestrial and aquatic environments o Temperate and tropical latitudes Microbial Life in the Cold Extremophiles Organisms that grow under very hot or very cold conditions Psychrophiles Organisms with cold temperature optima (<20 C) Inhabit permanently cold environments (for example deep ocean, Arctic and Antarctic environments) (Figure 5.21) Psychrotolerant Organisms that can grow at 0ºC but have optima of 20ºC to 40ºC More widely distributed in nature than true psychrophiles Microbial Life in the Cold (Continued…) Molecular adaptations that support psychrophily Production of enzymes that function optimally in the cold Modified cytoplasmic membranes: High unsaturated fatty acid content (note: saturated fatty acids freeze at higher than unsaturated fatty acids) The membrane isn’t moving around because of the cold Saturated = double bonds = kink 78 Microbiology 1010 – Lecture Notes Microbial Life at High Temperatures Above ~65ºC, only prokaryotic life forms exist (no eukaryotes) Chemoorganotrophic and chemolithotrophic species are present No phototrophy above approx. 70 C o High prokaryotic diversity (both Archaea and Bacteria are represented Thermophiles: organisms with growth temperature optima between 45ºC and 80ºC (terrestrial hot springs, very active compost). Hyperthermophiles: organisms with optima greater than 80ºC Inhabit hot environments, including boiling hot springs and seafloor hydrothermal vents, that can experience temperatures in excess of 100ºC Current temperature maximum record is held by an archaeon, Methanopyrus o kandleri, which can grow at 122 C! The pressure = allows the water to stay at 100. Microbial Life at High Temperatures (Continued…) Molecular adaptations to thermophily Specific modifications provide thermal stability to enzymes and proteins Modifications in cytoplasmic membranes to ensure heat stability o Bacteria have lipids rich in saturated fatty acids o Archaea have lipid monolayer rather than bilayer Tetra ether – no coboynal group (no ester group) – not acidic structures 5.13 Microbial Life at High Temperatures (Continued…) Hyperthermophiles produce enzymes widely used in industrial microbiology Example: Taq polymerase, used to automate the repetitive steps in the polymerase chain reaction (PCR) technique Hydrolytic enzymes (proteases, cellulases, lipases) Enzymes of thermophiles are more stable and tend to have higher activity than their mesophilic counterparts. PCR = Keeping the temp high to unzip the DNA and use taq polymerase to duplicate the template.. Use in lab to duplicate the Dna strand that is small. Then we use the same DNA to be 30 strands thick so we can see it. 79 Microbiology 1010 – Lecture Notes 16.12 Upper Temperature Limit for Microbial Life What are the upper temperature limits for life? o New species of thermophiles and hyperthermophiles are still being discovered o Laboratory experiments with biomolecules suggest 140–150°C Hyperthermophilic Archaea, H 2, and Microbial Evolution Hyperthermophiles may be the closest descendants of ancient microbes Hyperthermophilic Archaea and Bacteria are found on the deepest, shortest branches of the phylogenetic tree The oxidation of H 2 is common to many hyperthermophiles and may have been the first energy-yielding metabolism Energy – is the amount of electrons that can be transferred. Push protons out or keep them from coming in = acidiphilies must have this. 80 Microbiology 1010 – Lecture Notes After the midterm….. Effects of pH on Microbial Growth The pH of an environment greatly  affects microbial growth Some organisms have evolved to grow best at low or high pH, but most organisms grow best between pH 6 and 8 (neutrophiles) Effects of pH on Microbial Growth (Continued…) Acidophiles - Organisms that grow best at low pH (<6)  Alkaliphiles - Organisms
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