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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