HTH 245 Week 2 Notes
HTH 245 Week 2 Notes HTH 245
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This 4 page Class Notes was uploaded by Katlyn Palka on Monday September 12, 2016. The Class Notes belongs to HTH 245 at James Madison University taught by in Fall 2016. Since its upload, it has received 5 views. For similar materials see Foundations of Infectious Disease in Health Sciences at James Madison University.
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Date Created: 09/12/16
HTH 245 Week 2 Notes Chapter 2: The Microbial World ● Cell Theory (schleiden, Schwann, and Virchow) ○ All organisms are composed of fundamental units called cells ○ All organisms are unicellular (single cells) or multicellular (more than one cell) ○ All cells are fundamentally alike with regard to their structure and their metabolism ○ Cells arise only from previously existing cells (“life begets life”) ● The cell theory DOESN’T apply to viruses and prions ○ They are described as acellular, subcellular, or as biological agents ● Characteristics of life ○ Cellular organization: the cell is the basic unit of life; organisms are unicellular or multicellular ○ Energy production: organisms require energy and a biochemical strategy to meet their energy requirement ○ Reproduction: organisms have the capacity to reproduce by asexual or secual methods and in doing so pass on genetic material (DNA) to their progeny ○ Irritability: organisms respond to internal and external stimuli ○ Growth and development: organisms grow and develop in each new generation; specialization and differentiation occur in multicellular organisms ● Most organisms, including microbes, are heterotrophs, meaning that they require organic compounds (proteins, fats, and carbohydrates) as an energy source ● Microorganisms and plant life are autotrophs and they do not require organic compounds, but they do require energy ○ Some directly use the sun (photosynthetic autotrophs) ○ Some use energy from the metabolism of inorganic compounds (chemosynthetic autotrophs) ● Heterotrophs are dependent on autotrophs for energy ● Aerobes: organisms that require oxygen for their metabolic activities ● Anaerobes: organisms that DON’T require oxygen ○ Some are actually killed by oxygen ● Facultative anaerobes: bacteria that grow better in the presence of oxygen but can shift their metabolism allowing them to grow in the absence of oxygen ● What makes a microbe? ○ They are macroscopic: they can be seen with the naked eye ○ The term microbe is used to describe biological agents, in a collective sense, that in general are too small to be seen without the aid of a microscope ● Subcellular cells make up cells which make up tissues which make up organs which make up organ systems ○ All microbes are at the subcellular level or the cellular level (the only exception is that fungi and some algae approach the tissue level) ○ Prions and viruses are at the acellular level or the subcellular level (this means that they are less than cells) ● Procaryotic cells: simple morphology, and primarily distinguished by the fact that there is no membrane around the nucleus ○ There are no membranebound cellular structures (organelles) ○ They lack a nucleus but they have a nucleoid ○ Procaryotes are the ancestors for eukaryotes (which have a nucleus) ● Woese's threeDomain classification system ○ There is a universal ancestor that stems to create the 3 domains ■ Bacteria (eubacteria) ■ Archaea (archaebacteria): “extreme” bacteria that grow in highsalt environments and at extreme temperatures (hot and cold). They are not disease producers ● Extremophiles: bacteria found in the harshest environment ○ Hyperthermophile: (heatloving) they grow the best at temperatures above 100 degrees Celsius ○ Psychrophile: (coldloving) they are able to grow in sub freezing temperatures ○ Halophile: (saltloving) they can grow in extreme salinity (the dead sea is an example) ■ Eucarya: most algae, fungi, protozoans, and “higher” animals (humans) and plants ● Microbes ○ 5 types: ■ Bacteria, viruses, prions, fungi, protozoans ○ They are measured in very small units (either micrometers or nanometers) ○ Bacteria ■ They are microscopic (need a microscope to see it), unicellular, prokaryotic, they have cell walls, and they reproduce asexually ■ Most are heterotrophs (need energy from organic compounds), but some are autotrophs (they can create their own energy) ■ Some are motile (means they can move) by flagella ■ Most bacteria are beneficial, however a few are harmful ■ Example: Escherichia coli ○ Viruses ■ Viruses are NOT organisms ■ They are subcellular ■ They contain either DNA or RNA (but not both) ■ They are described as obligate intracellular parasites which means they must be (obligate) and inside living cells (intracellular) in order to replicate ● They are not capable of autonomous replication which means they can NOT replicate on their own they need that living cell in order to do so (they feed off the living cell) ■ Examples: HIV, measles, rabies ○ Prions ■ Prion is an abbreviation for proteinaceous infectious particles ■ Prions are protein molecules that do NOT have either DNA or RNA (they have no genome) ■ Abnormal prions convert normal protein in the body into infectious protein which then continues to spread throughout the body ■ Prions are acellular ■ They are submicroscopic ■ Example: mad cow disease ○ Fungi ■ Fungi are eukaryotes that are divided into two groups yeast and mold ● Yeasts are unicellular that are produced by budding ● Molds are multicellular that consist of long, branched, and intertwined filaments called hyphae ● They have cell walls ● They are opportunistic pathogens, which means that they are NOT usually considered pathogens, but when the immune system is weakened already they cause disease ○ Protozoans ■ Protozoans are unicellular and eukaryotes that are classified according to their means of movement ■ They require energy that is produced through the utilization of organic compounds ■ They are motile by flagella. Cilia, or pseudopods Chapter 3: Beneficial Aspects of Microbes: The other Side of the Coin ● Only a few microbes are disease producers and many are beneficial in our lives ● Microbes are the foundation of the biosphere ● They act as decomposers and recyclers ● Bacteria and fungi are the decomposers and the link between the producers (have photosynthetic capabilities that cause the production of organic compounds and oxygen) and the consumers (take oxygen and exhale carbon dioxide) ● The microbial population decomposes waste materials ● Bacteria are the basis for the biogeochemical cycles (the processes of recycling carbon, nitrogen, sulfur, iron, and phosphorus and returning them to nature) ○ Carbon Cycle ■ Carbon atoms are one of the key elements in living systems and are found in proteins, carbohydrates, fats and DNA ● Most of the carbon that is used by organisms is found in association with carbon dioxide ■ Microbes are essential in the conversion of atmospheric carbon dioxide to organic compounds and back to the atmosphere ● Photosynthetic organisms capture the sun’s energy and use that energy to convert the carbon dioxide and water to produce glucose and other energyrich carbohydrates ● Bioremediation: when you add materials to the environment to increase the rate natural biodegradation occurs. ○ Fertilizers and microorganisms are examples ○ Ex: throwing a banana peel on the ground and allowing its nutrients to settle as it decomposes ● Bioaugmentation: when nutrients are sprayed to promote the growth of indigenous microbes to accelerate degradation of pollutants ○ When there is a pollutant (on beaches or in a forest, etc.) we use microbes to make the pollutant go away faster. When the microbes are inserted into the environment it speeds of the biogeochemical cycle and return the elements (carbon, nitrogen, etc.) back into the environment faster ● Advantages of using microbes in bioremediation ○ They are cheap to grow ○ They are self limiting ■ They go away when the contaminant are gone and have a minimal disruption to the environment ● Ex: oil spill: microbes break down the oil from the oil spill, but once the oil is completely gone the microbes leave also. ○ They are used with sewage and wastewater treatment ■ Wastewater: what you put down the drain (sink and shower water) ■ They eliminate fecal pathogens before returning treated water to rivers and streams ○ They are also used as research tools ■ Used to create vaccines and used with gene therapy ● They helped sequence the human genome ● Gene therapy: microbes are used to infect human cells to change the DNA ○ This helps with genetic disorders (use a virus to copy itself in the cells to cancel out the diseased cells) ● Microbes are used in food ○ Yeasts are microbes that are found in the starter culture of bread. They allow the bread to rise ○ Various bacteria are found in the starter culture of cheese. This allows cheese to vary in texture, taste, and aroma ● Probiotics ○ There are both helpful and harmful effects of probiotics ○ Our intestines have bacteria throughout that are necessary to keep the body functioning healthily. Probiotics add healthy microbes (bacteria) back into the intestines ■ When someone has a yeast infection probiotics can help fix that. ■ If you have a weakened immune system taking a probiotic can be more harmful to your body than it would be helpful
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