Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Past Lectures - Winter 2025 PDF

Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Professor: Dr. Michael Cardinal-Aucoin Winter 2025 Biol1000 - Dr. M. Cardinal-Aucoin 1 Biol1000 - Dr. M. Cardinal-Aucoin 2  Cells Part I: Bacteria and Archaea Chapter...

Biology 1 – Cells, Molecular Biology and Genetics (Biol 1000) Professor: Dr. Michael Cardinal-Aucoin Winter 2025 Biol1000 - Dr. M. Cardinal-Aucoin 1 Biol1000 - Dr. M. Cardinal-Aucoin 2  Cells Part I: Bacteria and Archaea Chapter 7 Domains of Life Bacteria – Characteristics Archaea Biol1000 - Dr. M. Cardinal-Aucoin 3 Biol1000 - Dr. M. Cardinal-Aucoin 4 Evolution is responsible for producing the vast diversity of life on Earth. There are estimated to be about 8.7 million species alive today representing less than 1% of all the species that have ever existed. Biol1000 - Dr. M. Cardinal-Aucoin 5  3 Domains of life There are millions of species on Earth (~1.5 million catalogued so far). They can be divided into 2 big groups based on cell type. Prokaryotes divided into Archaea and Bacteria based on molecular differences. Eukaryotes Eukaryotes Archaea Bacteria Prokaryotes Biol1000 - Dr. M. Cardinal-Aucoin 6 Prokaryotes and Eukaryotes According to morphology, there are two broad groupings of life: 1. Prokaryotes, which lack a membrane-bound nucleus 2. Eukaryotes, which have such a nucleus According to phylogeny, or evolutionary history, there are three domains: 1. Bacteria 2. Archaea  prokaryotic 3. Eukarya – eukaryotic Biol1000 - Dr. M. Cardinal-Aucoin 7 BACTERIA Prokaryotes ARCHAEA 3 Domains of Life EUKARYA Note that Archaea are more closely related to Eukarya than to Bacteria. Biol1000 - Dr. M. Cardinal-Aucoin 8 Characteristics of Cells All cells: Contain genetic material (i.e. DNA) Are bounded by a cell membrane within which is the cytosol Have ribosomes (for protein synthesis) Can use some form of energy (metabolism) Can grow and reproduce Can sense and react to environment They’re alive!! Evolve Biol1000 - Dr. M. Cardinal-Aucoin 9 Bacteria Bacteria are: – Are small 0.5–5 µm. – Lack membrane-bound organelles. – Have a single circular chromosome (nucleoid). – Usually have a small circular DNA molecule (plasmid). – Can have flagellum and/or cilia. Divide by binary fission. Biol1000 - Dr. M. Cardinal-Aucoin 10 Bacteria No nucleus. All cells have these. Single chromosome. Fimbriae Cytosol Nucleoid Ribosomes Plasma Small (0.5-5 µm) membrane Bacterial chromosome Cell wall Capsule 0.5 m (a) A typical Flagella (b) A thin section rod-shaped through the bacterium bacterium Bacillus coagulans (TEM) Most have a cell wall. Biol1000 - Dr. M. Cardinal-Aucoin 11  Bacteria Bacteria have a single circular chromosome. Nucleoid: Discrete Plasmids: small circular concentration of DNA located molecules of DNA that carry a within the cell’s interior. small number of genes. nucleoid Biol1000 - Dr. M. Cardinal-Aucoin 12  Bacteria Pili: threadlike hollow structures that extend from one bacterial cell to another that allow the transfer of plasmids. Biol1000 - Dr. M. Cardinal-Aucoin 13 Bacteria Prokaryotes are able to move in liquid and wet surfaces because they have structures called flagella. Flagella are whiplike extensions that function to propel the cell forward. These flagella are made up of rigid helical proteins which rotate like propellers of a boat (it spins around its axis). This rotation of bacterial flagellum is actually In order to move, the flagellum driven by H+ flow. rotates counter-clockwise and this movement is driven by a rotor. – As the H+ flows between the membranes, this drives the rotor. – Similar to how H+ flow used by mitochondria to make ATP. Biol1000 - Dr. M. Cardinal-Aucoin 14  Bacteria Structure and mechanism differ between flagella of bacteria, archaea, and eukarya but function is the same. Divergent evolution Convergent Evolution Prokaryotic ATPases flagellum Kishikawa J-i, Ibuki T, Nakamura S, Nakanishi A, Minamino T, Miyata T, et al. (2013) Common Wikimedia Commons Evolutionary Origin for the Rotor Domain of Rotary Atpases and Flagellar Protein Export Apparatus. PLoS ONE 8(5): e64695. https://doi.org/10.1371/journal.pone.0064695 Biol1000 - Dr. M. Cardinal-Aucoin 15 Prokaryote Structure Bacterial cell walls: – Composed of peptidoglycan (= protein + carb) – Strong, maintains shape, resists bursting. A polysaccharide or protein layer called a capsule covers many prokaryotes. Used to classify Bacteria into 2 main categories. Biol1000 - Dr. M. Cardinal-Aucoin 16 Bacteria Biol1000 - Dr. M. Cardinal-Aucoin 17 http://www.medicinehack.com/2012/02/gram-staining-procedure-mechanism.html Biol1000 - Dr. M. Cardinal-Aucoin 18  Bacteria Penicillin kills gram-positive bacteria. – Interferes with peptidoglycan synthesis. – No effect on eukaryotic cells; they lack petpydoglycan cell walls. – Gram-negative bacteria more likely to be antibiotic resistant. Gram Gram positive Negative -thick -thin peptidoglycan peptidoglycan layer layer Biol1000 - Dr. M. Cardinal-Aucoin 19 Bacteria Bacteria and archaea contain protein fibres that perform a variety of roles. Form the basis of the cytoskeleton: – Maintains cell shape (e.g. MreB) – Assists in cell division (e.g. FtsZ) Biol1000 - Dr. M. Cardinal-Aucoin 20 Bacterial Cell Division Binary fission (asexual reproduction): Bacteria have single circular chromosome. 1. Chromosome replicates. 2. Two resulting chromosomes migrate to polar ends of cell (cell elongates to provide room for both chromosomes). 3. Plasma membrane grows inward at center of cell (between nucleoid regions). 4. New cell wall deposited until 2 daughter cells result. Details of the process are sill unclear. Biol1000 - Dr. M. Cardinal-Aucoin 21 Bacterial Cell Division Biol1000 - Dr. M. Cardinal-Aucoin 22 Archaea Archaea are Prokaryotes. Archaea split from Bacteria and share a common ancestor with Eukarya. Appear superficially similar to Bacteria but have many differences and many similarities to Eukarya. – Mostly distinguished at molecular level. Biol1000 - Dr. M. Cardinal-Aucoin 23 Archaea Like bacteria, archaea are prokaryotic cells Smaller than eukaryotic cells. Diverse morphologies. Nucleoid, circular chromosome. Ribosomes, cytoskeleton. Most have cell walls (polysaccharides and proteins but lack peptidoglycan). Some have glycocalyx, flagella, fimbria-like structures. Biol1000 - Dr. M. Cardinal-Aucoin 24 Archaea Some archaea live in extreme environments and are called extremophiles. Extreme halophiles live in highly saline environments. Extreme thermophiles thrive in very hot environments. Biol1000 - Dr. M. Cardinal-Aucoin 25  Metabolic Diversity Prokaryotes can do all of these!! – Complex biochemistries. Major Nutritional Modes Source of carbon: Organic molecules CO2 (e.g. protein, glucose, etc.) Consumers Source of energy: Light Inorganic chemical Photoheterotrophy Chemoheterotrophy Light + Org. mol. Organic molecules Some bacteria Animals, etc. Biol1000 - Dr. M. Cardinal-Aucoin 26 Bacteria Many prokaryotes have internal photosynthetic membranes: – Convert energy in sunlight to chemical energy. – Develop from folds of the plasma membrane. Biol1000 - Dr. M. Cardinal-Aucoin 27  Main Sites of Human Microbiota Bacterial Colonization We are an ecosystem! mouth About 40 trillion bacterial cells, fungal cells, and protists live on and in our bodies! gut – Therefore about 1:1 ration of bacteria to human cells (Sender et al. 2016, Cell). Human intestines are home to about reproductive 500–1,000 species of bacteria. tract – Some Archaea inhabit our gut but no pathogens yet identified! skin Biol1000 - Dr. M. Cardinal-Aucoin 28 Summary Domains of Life Properties and structure of Bacteria Archaea Bacterial Metabolism Human microbiota Biol1000 - Dr. M. Cardinal-Aucoin 29