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Viruses and Bacteria Why Do We Need To Know? • Viruses and bacteria are some of the most simple and elegant organisms on the planet • However, just because they are not complex does not mean that they are not important • Viruses and bacteria shape the world as we know it Why Do We Need To Know? • There are at least ten times more viruses than there are all other species on earth • Viruses are some of the most simple “living” things on the earth – They test our definitions of what is alive and not alive • They can actually be reverse engineered to carry out work that impossible for humans Why Do We Need To Know? • Bacteria are everywhere inside and on living organisms • There are over 100 Trillion bacteria that call the human body home • That means between 35 lbs of your body mass is bacteria Viruses • Viruses are simple organisms • They are nothing more than genes in a box • The genes that they carry can be in the form of DNA or RNA • They are protected by a tough outer layer called capsid Viruses • Viruses can have one of two life cycles • In the lytic cycle the virus injects its genetic material into a cell and the resulting viruses will break free of the host cell • In the lysogenic cycle the virus replicates without destroying the host cell Viruses • In the lytic cycle, the virus in essence hijacks the cell and causes the cell to create more viruses • When the cell has created more viruses, they will cause the cell to lyse and the new viruses are released Viruses • In the lysogenic cycle a virus incorporates its DNA to a host’s genome • The cell then proceeds like normal • When there is an environmental trigger, the viral genome then switches on and follows a path similar to the lytic cycle Video • https://www.youtube.c om/watch?v=TVLo2CtB 3GA Bacteria • Bacteria are simple prokaryotic organisms • They have a single circular loop of DNA that is in the cytoplasm • Bacteria normally use the asexual binary fission to reproduce Bacteria • However there are three different ways that bacteria can exchange genetic material with other cells – Transformation – Transduction – Conjugation Bacteria • Transformation is a process where bacterial cells uptake DNA from the surrounding environment and incorporate it into their genome • This allows bacteria to inherit new characteristics from organisms that are no longer functional, alive or whole Bacteria • Sometimes viruses guide the genome of a bacteria • During the lytic cycle a section of the host cell’s DNA might be put into a virus • This means that the next cell it infects is receiving new bacterial DNA instead of a viral genome • This process is called transduction Bacteria • Bacteria can also “mate” • This mating is different from prototypical eukaryotic mating, however genetic information is transferred from a host cell to a recipient cell • Bacterial mating is called conjugation Bacteria • When conjugation occurs the donor cell copies a part of its DNA and sends it or it sends a plasmid • A plasmid is a small circular section of DNA that is separate from the rest of the bacterial DNA