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Bacteria
Characteristics of Bacteria
• Single-celled prokaryotic organisms
• Most smaller than 10 micrometers
• Contain cell walls of a protein and carbohydrate matrix called peptidoglycan
• Structurally different from Archaea or plants
• Do not contain a nucleus or membrane-bound organelles
• Nucleoid – a nuclear region in bacteria where DNA is concentrated
• Plasmids are small circular segments of bacterial DNA
• Capsule – a protective coating located outside the cell wall in bacteria
• Some are autotrophs
• Some perform photosynthesis
• Some perform chemosynthesis
• Deep sea vents, other ocean environments, and hot springs
• Some are heterotrophic
• Aerobic bacteria – a variety of bacterium that requires oxygen for metabolism
• Anaerobic bacteria – a variety of bacterium that does not require oxygen for metabolism
• Obligate anaerobes – a group of bacteria that cannot grow in or tolerate the presence of oxygen
• Facultative anaerobes – a group of bacteria that are able to use fermentation if oxygen
is not available or cellular respiration if oxygen is available
Reproduction of Bacteria
• Binary fission – a form of asexual reproduction in bacteria that results in cell division
• 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
Biology 15.2 – Bacteria
Bacteria
• Conjugation – a DNA exchange in bacteria involving pili and direct cell contact
• Similar to eukaryotic genetic recombination
• 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
• Pathogenic – a disease-causing organism
• Bacterial diseases are spread through:
• Droplets in the air
• On surfaces
• Through contaminated food
• Direct contact with the bacterium
• In fluids
• Tuberculosis (TB) – bacterial disease caused by the bacterium Mycobacterium tuberculosis
• Opportunistic disease
• May cause lung damage
• Anthrax – a bacterial disease caused by Bacillus anthracis; typically a disease of farm animals
• Endospores – a non-reproductive structure that becomes dormant in response to adverse conditions
• Can survive for many years
• Can regenerate into colonies of active bacteria
• Type of anthrax developed depends on the location of infection
• Biological weapon in 2001
• Envelopes which contained a powdery form of anthrax endospores were mailed
• Caused cutaneous anthrax and inhalation anthrax
• Streptococcal disease – any bacterial disease, including strep throat, that is caused by streptococcus genus
• Meningitis – infection of the coverings of the brain and spinal cord
• Some forms caused by various bacteria
• Salmonellosis – a bacterial gastrointestinal disease usually spread through contaminated food or contact with reptiles
Biology 15.2 – Bacteria
Bacteria
Disease
Transmission
Tuberculosis
Very contagious,
Airborne
✔
Gastrointestinal
anthrax
Ingesting
contaminated soil
or meat
✔
Cutaneous anthrax
Entering skin
through open
wound
Inhalational
anthrax
Inhalation of
endospores
✔
✔
Streptococcal
disease
Highly contagious
in children
✔
✔
Bacterial
meningitis
Caused by a
variety of bacteria
Salmonellosis
Ingesting
contaminated
food or reptile
contact
Fever Aches Fatigue Nausea
✔
✔
✔
Diarrhea Other Symptoms Treatment
Chills
Persistent cough Antibiotics
Weight loss
✔
✔
Swelling
Redness of skin
Ulcer with
blackened skin
Vomiting
Difficulty
breathing
Red throat with
possible white
patches
Chills
Appetite loss
Headache
Stiff neck
Mental symptoms
Spotted rash
✔
✔
✔
✔
Appetite loss
Abdominal pain
✔
Headache
Cramps
Abdominal pain
Antibiotics
Antibiotics
Antibiotics,
Mortality
rate is high
Antibiotics
Extremely
serious,
Vaccine
available
Fluids
Rest
Antibiotics
Biology 15.2 – Bacteria
Bacteria
Ecological Impact of Bacteria
• Impact of bacteria on biosphere
• Ocean-dwelling cyanobacteria 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
• Bacteria maintain health of organisms through biotechnology
• Vaccines and antibiotics
• Ex) Biotechnologists purify a substance produced by Streptomyces griseus to make the antibiotic streptomycin
• Ex) Lactobacillus bulgaricus is used to produce dairy products
• Bacteria used in genetic engineering
• 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
Biology 15.2 – Bacteria