Bacteria
Characteristics of Bacteria | Reproduction of Bacteria
Characteristics of Bacteria
• Single-celled prokaryotic organisms
• Contain cell walls composed of a protein and carbohydrate
matrix called peptidoglycan
– Structurally different from Archaea or plants
• Do not contain a nucleus or membrane-bound organelles
Characteristics of Bacteria
• Nucleoid – region within bacteria where DNA is organized
• Plasmids are small circular segments of bacterial DNA
• All contain:
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Plasma membrane
Cytoplasm
Ribosomes
Capsule – a protective coating outside of bacterial cell walls
• Some contain:
– Flagella which are used for locomotion
– Pili function in some forms of reproduction
Characteristics of Bacteria
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Streptococcus Causes
Strep Throat
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Bacillus - E. coli
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Spirochetes
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Characteristics of Bacteria
• Bacteria are very diverse
– Some are autotrophs
– Some perform photosynthesis with chlorophyll
– Some perform chemosynthesis
• Deep sea vents, other ocean environments, and hot springs
• Some are heterotrophic
– Obtain energy by absorbing or ingesting food
Characteristics of Bacteria
• Aerobic bacteria – require oxygen in the process of cellular
respiration
• Anaerobic bacteria – do not use oxygen
Reproduction of Bacteria
• Cell division = reproduction in prokaryotes
• Binary fission – simplified form of cell division used by
bacteria
• Steps:
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DNA is replicated
Cell increases in size, splits in two
Plasma membrane pinches together and a new cell plate forms
Control of the bacterial cell cycle: growth rates, biochemical
signals, and environmental conditions
Reproduction in Bacteria
Reproduction in Bacteria
• Ability to exchange DNA with another bacterium
• Conjugation – exchange of DNA in bacteria
– Similar to genetic recombination in eukaryotes
Reproduction in Bacteria
• Donor bacterium
connects to another
bacterium using pilus
• DNA is transferred to
the recipient cell through
pilus
– Aided by proteins
• DNA donated can be a
plasmid
• Donated DNA may
contain beneficial genes
Diseases Caused by Bacteria
• Some bacteria disrupt the health of other organisms
• Pathogenic – bacteria that cause disease
• Bacterial diseases are spread through:
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Droplets in the air
Direct contact with the bacterium
On surfaces
In fluids
Through contaminated food
Diseases Caused by Bacteria
• Streptococcal disease – any bacterial disease, including
strep throat, that is caused by streptococcus genus
• Common infection in children
• Highly contagious
• Symptoms:
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Sudden fever
Aches
Nausea
Red throat with possible white patches
• Treated with antibiotics
Ecological Impact of Bacteria
• Impact of bacteria on biosphere
Produce oxygen
– Bacteria decompose dead plant and animal matter
• Release carbon dioxide into atmosphere
• Multicellular organisms have bacteria living in their
digestive tract
– Mutualistic relationship
– Bacteria break down indigestible compounds for host to absorb
– Bacteria receive nutrition and a place to live
Ecological Impact of Bacteria
• Bacteria maintain health of organisms through
biotechnology
– Vaccines and antibiotics
• Bacteria used in genetic engineering
Ecological Impact of Bacteria
• Bacteria help in producing and cycling nitrogen
– Bacteria in soil make nitrogen useable through nitrogen fixation
– Break down dead organisms and waste into ammonium
– Other bacteria then change ammonium into nitrates for plants
• These bacterial processes allow nitrogen to cycle
– From atmosphere
– Through food chain
– Within soil
Nitrogen Cycle