Chapter 28: Microbiology Slides PDF

Chapter 28: Microbiology John D. L. Shadwick Department of Biological Sciences University of Arkansas at Fayetteville [email protected] About 2 pounds of bacteria live in or on your body. A. True B. False The Microbial World Microbiology Study of microbes, including bacteria, archaea, protis...

Chapter 28: Microbiology John D. L. Shadwick Department of Biological Sciences University of Arkansas at Fayetteville [email protected] About 2 pounds of bacteria live in or on your body. A. True B. False The Microbial World Microbiology Study of microbes, including bacteria, archaea, protists, fungi, viruses, and prions. Microbes are very abundant in air, soil, water and on objects. Microbiota on our bodies Some bacteria and fungi are decomposers Photosynthetic protists and bacteria are primary producers Pasteur and Spontaneous Generation All life is related! “But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity etcetera present, that a protein compound was chemically formed, ready to undergo still more complex changes [..] " ~Charles Darwin, in a letter to Joseph Hooker (1871) Origin of Microbial Life All traced back to a single common ancestor called the last universal common ancestor (LUCA). Stage 1: Organic monomers - evolution of monomers, Primoridal soup Oparin-Haldane hypothesis Miller-Urey Experiment Stage 2: Organic polymers – evolution of polymers Stage 3: Protobionts – evolution of protobionts Development of the cell membrane Stage 4: Living cells – evolution of living cells The Evolution of Monomers Miller-Urey experiment (1953). Early earth had reducing atmosphere. After a week,water turned brown. Amino acids and other organic acids produced. Repeatedly tested over the decades. Even greater number of organic molecules The Evolution of Monomers Other sources of organic monomers. Hydrothermal vents. Meteors or comets. The Evolution of Polymers Protein First Hypothesis. RNA-first hypothesis Solar energy causes amino RNA evolved first and acted acids at shoreline to form as both hereditary material simple ploypeptids with and enzyme. catalytic properties. The Evolution of Protobionts 1 Ptotobionts Outer membrane made of fatty acids. Proteins or other polymers on inside. Larger “Vesicles” able to divide. The Evolution of Living Cells Cells with membranes and DNA, RNA, and Protein. RNA first hypothesis supports this. Codon Chart seems optimized to deal with mutation. May have been natural selection on codons. Prokaryotic Diversity: Archaea Domain Bacteria and domain Archaea are both prokaryotes. Start Here Wed. 002 Archaeal Size and Structure Archaea Small Genome is a single, closed, circular DNA molecule plasma membrane single lipid layer with branched side chains Three main types are based on unique habitats and metabolism Organic monomers, like amino acids and sugars, could form without the presence of life. A. True B. False Start Here Wednesday Types of Archaea Halophiles - salty habitats (12-15%) Isolated from environments such as the Great Salt Lake, the Dead Sea, and hypersaline soils. Thermoacidophiles - extremely hot, acidic, aquatic environments. Hot springs, geysers and underwater volcanoes Evolved to function at temperatures as high as 800C Methanogens - use carbon dioxide and hydrogen as energy sources. Produce methane as a byproduct In anaerobic environments like swamps, and intestines of animals. Cows and other animals, including humans Domain Bacteria Bacteria (domain Bacteria) are the most common type of prokaryote on Earth. Over 11,000 different species but probably millions. Most bacteria are between 0.2-10µm in size Bacteria have three basic shapes. Rod (bacillus, pl., bacilli); spherical (coccus, pl., cocci); and spiral-shaped or helical (spirillum)  Bacterial Size and Structure Motile bacteria have flagella for locomotion. These are structurally different from eukaryotic flagella. Some bacteria have fimbriae used to bind to various surfaces. Certain bacteria that infect the urinary tract use fimbriae to attach to cell surfaces. Figure 28.9  Bacterial Size and Structure Most bacteria have a single circular chromosome. Located in nucleoid region Many bacteria also have plasmids. Accessory rings of DNA that carry certain genes, such as antibiotic resistance. Figure 28.9 Bacterial Reproduction and Gene Transfer Bacteria reproduce asexually, by binary fission. The bacterial cell replicates its genome and divides into two new daughter cells. Some bacteria can form a resistant endospore Endospore for survival in harsh conditions Bacterial Reproduction and Gene Transfer No sexual reproduction in prokaryotes Three mechanisms of genetic recombination Conjugation: donor cell passes DNA to a recipient cell by way of a sex pilus Transformation: bacterium takes up DNA from environment released by dead bacteria Transduction: viruses carry bacterial DNA from cell to cell All bacteria on the skin cause parasitic infection. A. True B. False Bacterial Metabolism Most are heterotrophic – require organic carbon for food Some are chemoautotrophs – use inorganic chemicals to fix carbon dioxide into organic form Cyanobacteria are photoautotrophs – Have Chlorophyll and do Figure 28.11 Cyanobacteri photosynthesis that a Bacterial Diseases in Humans Most bacteria do not cause diseases Strep Throat Pathogenic bacteria have genes for virulence factors. Often for toxins or factors to adhere to tissues Streptococcus infections Streptococcus pyrogenes: causes the most diseases Impetigo Pharyngitis: commonly called strep throat Impetigo in infants: mild skin disease Scarlet fever: produces red rash Rheumatic fever: auto-immune Can cause heart damage, other problems Caused by untreated strep throat leading to autoimmune problems Scarlet Fever Staphylococcus aureus and MRSA About 20% of people are carriers Usually limited to skin infections. A strain resistant to methicillin is called MRSA. Kills young, otherwise healthy individuals Has genes for toxins Bacterial Diseases in Humans Food Poisoning Two types of food poisoning. Some produce a toxin while growing in food. Mainly of vomiting and diarrhea, usually self-limiting Clostridium botulinum – produces one of the most toxic substances on Earth For Beauty? Some cause an infection while growing in the intestines. – Salmonella causes symptoms after several days of growing  If you get very sick two hours after eating at a restaurant, the type of food poisoning is probably caused by bacterium that A. caused an infection in your intestines. B. released toxins into the food.  Drug Control of Bacterial Diseases Antibiotics inhibit bacteria by interfering with a unique metabolic pathway of bacteria. Not expected to harm human cells Antibiotics work in two ways. Inhibit protein synthesis by bacteria Ex: Erythromycin and tetracyclines Drug Control of Bacterial Diseases Problems related to antibiotic therapy Potentially fatal allergic reactions Killing off of normal flora (beneficial bacteria) May cause overgrowth of harmful bacteria in intestines or yeast in the vagina. Bacterial resistance Strains have evolved that are resistant to typical antibiotic therapy. Newly resistant gonorrhea bacterium One species of bacterium can get resistance genes from another. Start Here Thursday 004, 003 Viruses and Prions Viruses are acellular Smaller than bacteria (0.03- structures that are 0.2µm) parasites Two main components to all Viruses use the host cell’s viruses Capsid (outer portion comprised replication machinery, of proteins) such as ribosomes and May be surrounded by a lipid certain enzymes. envelope May have spikes for attachment to a host cell Nucleic acid core (DNA or RNA) Virus Structure Viral Reproduction Viruses are specific to a particular host. Spikes on a virus configure exactly to receptor molecules on the membrane of a potential host cell. The reproductive cycle of a typical enveloped animal RNA virus has six steps. The Common Cold and Influenza Colds are caused mainly by rhinoviruses Over 100 species Flu is caused by influenza viruses Antigens on cold and flu viruses can change. Antigenic drift – small changes in the virus, mutation Antigenic shift – new combinations of surface spikes Antigenic Drift and Antigenic Shift Two viruses infecting the same cell and exchanging spike genes have evolved by antigenic shift. A. True B. False Start Here Friday 001, 002 Prion s Prions are protein infectious particles. Normal proteins change their shape; this causes other normal proteins to change their shape. Causes degenerative diseases in nervous system Prions passed through ingestion of infected tissues Bovine spongiform encephalopathy (“mad cow disease”) - cattle Chronic wasting disease - deer, elk and moose Humans?