Bacteria
B Y L IL A H B OJ A NOS K I, J E NNA CAVA L I E R E, CHR I S T I NA
FONTA NA R O SA , T ESSA PR USHAN
Overview
• Prokaryotes
• Anaerobes
• Reproduction
• Genetic recombination
• Bacterial recombination
• Drug resistance
Characteristics of Prokaryotic Cells
• DNA is found in a single prokaryotic bacterial chromosome.
• Bacterial cells divide by binary fission
• Binary fission – a type of asexual reproduction
• The bacteria in a colony are identical to the parent cell
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Transformation
• “the uptake of foreign DNA from the surrounding environment”
• Frederick Griffith experimented with harmless bacteria that had DNA
from dead cells.
• This bacteria carried a gene that animals were immune to.
• Now this previously harmful bacteria can infect animals when they
gain this gene.
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Transduction
• “The transfer of bacterial genes by a phage”
• Phage - a virus that is in bacteria
• A DNA fragment that belongs to a phage’s host cell is accidentally
packaged within the phage’s coat instead of phage DNA.
• When the phage infects the bacterial cell, the DNA from the other
host is injected into the new host.
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Conjugation
• “This union of cells and the DNA transfer between them”
• “Male” donor cell has a sex pili that is attached to the “female”
recipient cell.
• Outside layers of the cell conjoined, cytoplasmic bridge formed
between them.
• The donor cell replicates its DNA so it doesn’t lose any genes.
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Background Anaerobes and Aerobes
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Superoxide- An oxide containing the negatively charged ion O2
Superoxide is deadly to obligate anaerobes
Fermentation used when there is no oxygen
Fermentation creates less energy than aerobic respiration
Oxidative stress occurs when a cell has a lot of oxygen inside it
Obligate Anaerobes
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Clostridium botulinum is an example of
an obligate anaerobe.
Obligate= strictly
Does not require oxygen to survive
Lives in an area without oxygen
Deadly for them to be exposed to atmospheric levels of oxygen
Do not have enzymes that change superoxide formed in their cells
Fermentation
Use sulfate, nitrate, iron, manganese, or carbon monoxide as electron carriers
Superoxide Dismutase is an enzyme that
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breaks down superoxide in the cells.
Facultative Anaerobes
• Can produce energy through aerobic respiration, but can switch to use anaerobic
respiration
• Depends on oxygen levels and the amount of fermentable material in the area
• If oxygen is available, they use aerobic respiration
• If oxygen is NOT available, some ferment and use anaerobic respiration
• Include fungi such as yeasts
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Yeast is an example of a
facultative anaerobe.
Obligate Aerobes
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Oxygen is needed
To get energy, they need oxygen to oxidize substrates such as sugars and fats
Oxygen is the final electron acceptor
Create more energy than obligate anaerobes, but they deal with high levels of
oxidative stress
• Includes most fungi, almost all animals, and some bacteria
Aerobic respiration
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How bacterial cells reproduce
• Bacteria cells are asexual and don’t
need a mate to reproduce
• Bacteria reproduce by binary fission
• The bacterium (single cell), divides into
2 identical daughter cells
• Binary fission begins when DNA of
bacterium divides into 2 (replicates)
• The bacterial cell lengthens and splits
into 2 daughter cells
• Each daughter cell is a clone of the
parent cell
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How bacterial cells reproduce
• When conditions are right,
temperature and nutrients are
available to bacteria
• That’s why we become ill when
pathogenic microbes (sickness
causing bacteria) infect our
bodies
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Genetic recombination
• A process in which pieces of
DNA are broken and
recombined to produce new
combinations of alleles
• involves exchanging of genetic
material between multiple
chromosomes or between
different parts of the same
chromosome
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Genetic recombination
• One ex. of recombination in
diploid eukaryotic organisms is
exchange of genetic information
between duplicated chromosomes
during meiosis
• outcome of recombination is to
make sure each gamete includes
maternal and paternal genetic
info, so the child inherits from all 4
grandparents, resulting in a max
amount of genetic diversity
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Obtaining Energy
• Photosynthesis
• Use solar energy to turn CO2 and water into glucose and oxygen
• Glucose is food for bacteria
• Decomposers
• Break down waste and dead organisms
• Use organic substrates broken down for energy
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Obtaining Energy
• Mutualism
• Depend on other organisms for survival
• Live in roots of legumes
• Turn nitrogen-containing molecules into nitrogen for plants to use
• Parasitism
• Cause illness
• Bacteria benefits, organism harmed
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Autotrophs and Heterotrophs
A UTOT R OPHS
HE T E R OT RO PHS
• Make their own food
• Have to consume their
energy
• Chemoautotroph
• Synthesize organic compounds from
carbon dioxide
• Photoautotroph
• Convert inorganic materials into organic
materials for biosynthesis
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• Inorganic material- not derived from living
organisms and contains no organically
produced carbon
• Biosynthesis- the production of complex
molecules within living organisms or cells
• Chemoheterotroph
• Use carbon for energy from
sulfur, carbohydrates, lipids, and
proteins
• Photoheterotroph
• Depend on light for their source
of energy
Antimicrobial Resistance
• When bacteria is able to resist antibacterial drugs
• Standard treatments become ineffective
• Bacteria evolve to become resistant/immune to medicine
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Summary
• Bacteria can consume or produce its own energy
• Oxygen may (aerobic) or may not (anaerobic) need to be present to
make energy
• Meiosis is an example of genetic recombination
• Bacterial cells divide by binary fission
• Bacteria can develop a resistance to antibacterial drugs