Download How Bacteria Reproduce

How Bacteria
Reproduce
By: Stephanie and Anna
Asexual Reproduction
 Bacterial cells cannot reproduce
 Lack nuclei therefore cannot go through mitosis or meiosis
 Genetic material is contained in a single chromosome with
the cell
 Binary fission: the asexually reproductive process of cell
division in bacteria
 As a bacterial cell grows, it duplicates its original, single
chromosome
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 It gets longer and separates into two chromosomes.
 Builds a wall and than splits itself into two smaller cells.
 The two smaller cells are genetically identical
 This is sequence is called exponential growth.
 This process happens all very quickly , reproducing two
new cells every 20 minutes.
Sexual Reproduction
 Conjugation: produces cells with new genetic
combinations
 Some may be better adapted to changing conditions
 Bacterial cells become linked through pili (singular pilus)
 Bacterium transfers all or part of its chromosome to the
other
 The receiving cell undergoes binary fission to produce
more cells with the same genetic make-up
Gene Transfer
 Plasmids: small loops of DNA that separate from the main
chromosome
 Contain from one to a few genes which are different than
the ones found in the chromosome
 Can split from the chromosome and rejoin it
 Important method of producing genetic recombination
 Plasmids are transferred during conjugation
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 Scientists use this as a tool for genetic engineering to
introduce new genes into cells
Spore Formation
 Life cycle includes a dormant stage
 Cells can survive in an unfavourable environment
 Develop a tough outer coating around their DNA
 Forms small seed like structures called endospores
 Bacteria do not grow or reproduce in the endospore stage
 Endospores can live in extreme conditions
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 Endospores lose their coat and grow and divide like normal
cells when favourable conditions return
 Endospores can be killed
Bacteria and Human Health
 Anaerobic: reactions in the absence of molecular oxygen
 Botulism: food poisoning caused by anaerobic bacteria
 Bacteria forms endospores that germinate in anaerobic
conditions
 Bacteria’s metabolism produces toxic products that cause
illness or death in humans
 Bacteria are not dangerous unless they’re trapped in
anaerobic conditions for a long period of time
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 Food must be heated under high pressure (with the
temperature above the boiling point of water) to ensure
the bacterial endospores are killed