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MICROORGANISMS - MICROORGANISMS Bacteria are characterized...

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MICROORGANISMS Bacteria are characterized by their simplicity. They are Prokaryotic cells. This means they contain no nucleus or any other internal membrane systems. Small size is dictated by the lack of internal membranes. Their simplicity means they must remain small. It also makes cell reproduction a very simple process. Reproduction Bacteria reproduce by binary fission, resulting in two genetically identical daughter cells. Mechanism is simpler than for eukaryotic cells. Plasma membrane plays a critical role in separating DNA replicates Simplicity gives potential for very rapid population growth Bacteria contain only a single chromosome and they only have one copy of it. Think back to all the steps required for mitosis and meiosis. All a bacteria has to do it duplicate one chromosome. The copies are attached to different spot on the plasma membrane. As the bacteria increases in size the chromosomes are separated. A membrane is formed in the middle of the original cell and the two new cells can separate. Some bacteria may contain extra pieces of DNA called plasmids. Plasmids contain extra genes. They are not required for survival under normal circumstances, but may be beneficial in certain environments. The most famous of these are the plasmids that confer resistance to certain antibiotics. Bacteria are not too picky about where the plasmid comes from and they can often absorb plasmids from other bacteria growing with them. This makes the transfer of resistance much faster. Plasmids Plasmids are small circles of DNA that carry only a few genes. They replicate independently of the main chromosome. F plasmids permit conjugation; R plasmids carry resistance genes and carry genes for antibiotic resistance. When we discuss biotechnology we will discuss how genes from other organisms including plants and animals can be inserted in bacteria by means of plasmids. Factors that affect the growth of bacteria:
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Nutrients pH Oxygen tension Temperature Water activity Presence of other microorganisms. Growth Reproduce by binary fission in a geometric manner Under ideal conditions can double in 20 min. 100 organisms can become 1 million in 3.5 hr. In may cases between 100,000 and 1 million organisms per gram will cause an effect. In some special cases this number may be as low as 10 viable organisms. Nutrient Content Some microorganisms can survive on a source of carbon, nitrogen and a few trace minerals.
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