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Viruses and Bacteria Biology Ch. 21 Ms. Haut Viruses: “Non-living” Entities • Small packages of nucleic acids in a protein coat • Are NOT cells—no cytoplasm and do not perform metabolic reactions • Obligate intracellular parasites— dependent upon other cells for replication Types of Viruses • DNA viruses – Genome is DNA • RNA viruses – Genome is RNA – Smaller than DNA viruses – Lack of proofreading—leads to evolution rate Bacteriophage: virus that infects bacteria Viruses Replicate Inside Living Cells • Viruses lack enzymes needed for metabolism and have no structures to make proteins • Use cells own machinery to replicate viruses • Pathogen: agent that causes disease – Viruses damage cells during replication Lytic Cycle Virulent Viruses Temperate Viruses Viruses can Cause Disease in Animals HIV Virus:Retrovirus that causes AIDS •Genetic flow : RNA DNA •2 identical strands of RNA •Infects white blood cells Vaccinations • Antibiotics don’t work—no metabolic reactions to interfere with • Vaccinations—parts of viruses, modified or killed viruses are injected into the body – Allows immune system to make antibodies against specific markers on the viral coat • HIV mutates too fast for immune system to keep up with The Prokaryotes They’re (almost) everywhere! •Most numerous and widespread organisms on earth •Only prokaryotic organisms, those that lack a nucleus or other membrane-bound organelles •Have a simpler structure than eukaryotes Shapes of Bacteria •Cocci-spherical-shaped Shapes of Bacteria •Cocci-spherical-shaped •Bacilli-rod-shaped Shapes of Bacteria •Cocci-spherical-shaped •Bacilli-rod-shaped •Spirilli-spiral-shaped Reproduction Binary fission 1. DNA replicates 2. Plasma membrane pinches inward 3. 2 daughter cells form with identical genomes Bacteria Divide and Multiply Reproduction Conjugation 1. A portion of the DNA of one moneran passes across the pili into another moneran 2. Homologous pieces line up 3. Recipient DNA portion is destroyed and the new DNA is substituted Special features and Movement Plasmid-circular DNA Capsule-protective layers of polysaccharide around cell wall Endospore-tough envelope that encases DNA and some cytoplasm during harsh environmental conditions Pili-protein strands that aid in attachment Flagella-protein filaments used in movement Nutrition Heterotroph-use food produced by other organisms -can feed on dead or decaying matter Autotroph-produce own food photoautotroph-use sunlight as source of energy chemoautotroph-use chemical reactions as source of energy •Gleocapsa x1000. A blue green bacterium. Individual cells secrete a gelatinous material. Respiration • Aerobic: must have oxygen to survive • Anaerobic: cannot survive in the presence of oxygen Bacteria can Cause Disease • Heterotrophic bacteria can break down organic structure in their environment and then absorb them – Mycobacterium tuberculosis –causes tuberculosis • Some bacteria secrete chemical compounds (toxins) into their environment – Toxins are poisonous to the cells – Salmonella typhimurium –produce endotoxins •Clostridium botulinum x1000. These bacteria cause botulism poisoning. Antibiotics-inhibit bacterial growth by interfering with cellular processes Bacteria Antibiotic Discs Bacteria are Important • Used to make food, antibiotics, and chemicals • Fixes atmospheric nitrogen so plants can use it • Clean environment (chemical spills) • Cycle important elements Lactobacillus-most common in the environment application is industrial, specifically for dairy production.
