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Bacteria and Evolution

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Bacteria and Evolution This week is about bacteria. • Review the lecture on bacteria • Watch the video about bacteria: amoeba sisters bacteria • Complete antibiotic resistance reading and questions • Complete the Prokaryotic and Eukaryotic worksheet You will be graded you based on the rubric below. If you get below a 70% I will allow you to redo the assignment. Bacteria and Evolution SOPHOMORE CP LAB BIODIVERSITY Prokaryotes vs. Eukaryotes Eu = do Pro = No ◦ Eukaryotes do have a nucleus ◦ Prokaryotes have no nucleus ◦ Plant, animal, protist, fungi ◦ Bacteria ◦ Uni or multicellular ◦ Unicellular ◦ Membrane bound organelles (ER, ◦ No membrane bound organelles Golgi, mitochondria) Bacterial Organization Bacteria Eubacteria Archaebacteria Found Found in Everywhere harsh environments Can Live in Live in Cause Ancestors of soil human body illnesses Eukaryotic cells BACTERIA Type of Prokaryote – ◦ A single celled organism that lacks a nucleus and other membrane bound organelles Bacteria Example: ◦ E.coli ◦ Streptococcus pneumoniae – strep throat ◦ Staphylococcus epidermidis - staph infection (skin) ◦ Methicillin-resistant Staphylococcus aureus - MRSA BACTERIA 1. Has Cell wall ◦ Thick outer covering made proteins and sometimes of peptidoglycan (combination of carbohydrates & proteins) ◦ Conduct a Gram stain in order to determine if peptidoglycan is present ◦ Gram + contain peptidoglycan = has protein ◦ Gram – no peptidoglycan = no protein BACTERIA 2. Has Cell (plasma) membrane ◦ Protects cell, regulates what enters and leaves 3. Has Ribosomes ◦ Make proteins May Have: ◦ Flagellum (Flagella) – whip like tail (s) ◦ Pili – shorter thinner hair like structures ◦ Both help bacteria cells move, ◦ Not all bacteria move, some stay in place BACTERIAL DNA Two Types: 1. Chromosomal - Single circular chromosome ◦ not x shaped like eukaryotes ◦ Circular chromosome and some proteins form a nucleoid ◦ Contains all the information a bacteria needs to survive and make proteins 2. Plasmid – smaller circular DNA molecules ◦ Contain just a few genes that help bacteria overcome stressful situations ◦ Not in all bacteria ◦ Can easily be transferred between different bacteria cells ◦ Can replicate on its own ◦ Can have hundreds of copies in a single bacteria cell Bacteria Structure Ribosome Cell wall Peptidoglycan Cell membrane Flagellum Pili DNA BACTERIAL REPLICATION ◦Asexual Reproduction - One parent, No sex necessary ◦Includes bacterial reproduction and mitosis in eukaryotes ◦Produces two new identical daughter cells ◦each with half new and half old DNA BACTERIAL REPLICATION Binary Fission – bacteria cell reproduction ◦Two stages: 1. DNA Replication – DNA is copied and each new cell will have a copy of the genetic information ◦ Limited error check and regulation – frequent mutations 2. Cytokinesis- Cell divides pinched into two independent cells. BACTERIAL CONJUGATION ◦Conjugation allows bacteria to exchange genetic material with nearby bacteria ◦Direct cell to cell contact or forms a bridge using pili ◦Allows for greater genetic diversity BACTERIAL EVOLUTION ◦Bacteria can evolve rapid – we can actually witness this evolution ◦Reproduce rapidly – many generation in short time period ◦Not as complex – less error check leads to frequent mutations ◦Can easily exchange genetic material through conjugation ◦This means bacteria can easily adapt in just a few generations Getting Energy Bacteria can be: •Autotrophs – can preform photosynthesis or chemosynthesis •Heterotrophs – engulf other organisms and nutrients, usually use endocytosis Controlling Bacteria Antiseptics ◦Chemicals that inactivate the infecting organism Antibiotics ◦Blocks the growth and reproduction of bacteria ◦Attacks cell wall = not effective against viruses Antibiotics: An Overview Antibiotics are a type of medicine which are used to treat bacterial infections. Every day we encounter thousands of bacterial cells. We are colonized with lots of different types of bacteria which live on us, and inside of us; everywhere from the grooves of your fingerprint, to the nooks and crannies of your intestines. If you count all of the bacteria, they actually outnumber us (by "us" we mean our human cells) about 10 to 1. To stay healthy, we need to maintain a healthy ecosystem of bacteria, called normal flora (not all bacteria are bad!), while selectively getting rid of the harmful, “pathogenic” bacteria which can cause an infection. Pathogenic bacteria is a relative term. Some bacteria can cause illness in you no matter what. Other bacteria cause illness when they wander from their normal location (e.g. intestines) and try to live in a new location (e.g. bladder), which is what happens when you develop a urinary tract infection (UTI). The body’s immune system responds to an infection by trying to fight and destroy the invading bacteria! What are antibiotics? To help the immune system, we sometimes use antibiotics, which are chemicals (specifically a swarm of small molecules) that enter and stick to important parts (think of targets) of the bacterial cell, and interfere with its ability to survive and multiply. If the bacteria are susceptible to the antibiotic, then they will stop growing or simply die. These important parts in a bacteria include: • Proteins/sugars in the bacterial wall • Important enzymes that make new bacterial DNA or proteins When an antibiotic molecule sticks to its target, it will disable or destroy that protein or enzyme. If enough of the antibiotic is present, the bacterial cell is crippled and either stops growing (bacterio-static effect) or simply dies (bacteri-cidal effect). Just to be clear, antibiotics don’t affect viruses, fungi, or parasites - they only bind to bacterial cell targets so they only affect bacterial cells. In fact, they specifically target bacteria rather than human cells. How do antibiotics work? Let's take a look at an example of one antibiotic called Penicillin. Penicillin is a fabulous antibiotic because it isn't toxic to humans at concentrations that can kill bacteria and it can kill a lot of different types of bacteria. In short, penicillin causes the bacteria to weaken its own cell wall and prevents the bacteria from being able to repair itself. With a weak wall, water seeps in, and the bacteria swells up and explodes. Antibiotic Development Over the years, several antibiotics have been discovered in nature or synthesized in the lab. Some antibiotics target only specific bacteria and are called “narrow spectrum” antibiotics, whereas other antibiotics target many types of bacteria and are called “broad spectrum” antibiotics. Developing completely new classes of antibiotics (as opposed to variations on existing antibiotics) is very difficult. It’s easy to find chemicals that kill bacteria, but not so easy to find substances that could be used as medicines, even if researchers were given infinite resources! In fact, the most recent discovery of a novel antibiotic class was in 1987, more than 30 years ago (Silver, L., 2011)! While there are a few new antibiotics currently in development, researchers don’t know if they’ll ever become usable as medicine. This void in the discovery of new antibiotics is problematic. When a bacteria becomes resistant to a specific drug within a drug class, it gains some level of resistance to drugs within the same class. For example, if a bacteria became resistant to ampicillin, it would also have some level of resistance to other penicillin-like antibiotics. How does antibiotic resistance develop exactly? When a bacteria is exposed to antibiotics there are three possible outcomes - they will die, they will stagnate (not multiply), or they will multiply. Three main factors will predict which is more likely to happen; antibiotic concentration, bacterial mutation, and bacterial genetic exchange. • Antibiotic concentration Generally, the more antibiotic getting to a bacteria will cause it to stagnate/die, and less antibiotic will allow it to multiply. Some bacteria live within a “biofilm”, which is a jelly-like substance where thousands of bacterial cells are suspended inside (think raspberry seeds in raspberry jelly). It’s sort of like a big, thick energy shield. The antibiotic has to move (diffuse) through the biofilm to reach all of the bacterial cells. Some cells that are buried deep within the biofilm are exposed to only a fraction of the antibiotic that reaches the surface. • Bacterial mutation When bacterial cells replicate, there is a small chance the new bacterial cell will not be exactly the same as the original bacterial cell. We call these errors in the copied cell a mutation. In one bacterial cell, the cell wall could be slightly different, in another an enzyme works poorly, and so on. Mutations are key to the idea of evolution, and all of the diversity you can see in nature came from a series of many mutations over hundreds of thousands of years. In animals, it can take centuries or millennia for a species to adopt a mutation which helps it survive and reproduce. Bacteria on the other hand can multiply within hours, allowing for more mutations to occur over a shorter period of time. These mutations can make it difficult for the antibiotics to enter the bacteria or stick to it, making the antibiotic less effective at hurting or killing the bacteria. • Bacterial genetic exchange A curious habit of bacteria is that they love to share information when they meet. This happens even between two different bacterial species. As a result, once a single bacterial species has managed to resist antibiotics with a gene(s), that gene(s) can get copied
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