Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Viruses, Bacteria, Archaea, and Protists The Diversity of Life 1 Amazing Living Things • Record Holders. – Biggest: 27m Blue Whale, 100m redwood tree, sea kelp 274m, 1,500 acre fungus. – Deepest: 3km bacteria; Highest: 12 species of bacteria in Himalayas. – Hottest: Archaean Pyrolobus fumarii lives at 113°C; Coldest: bacterium Phormidium frigidum freezing water. – Oldest: Sequoia 3,500; Bristlecone Pine 4,900; Bacterial spores in amber 25-40 Mya, or archaen spores in salt crystals from 250 Mya. Amazing Living Things • Importance of Microbes. – All living things classified in three domains: Bacteria, and Archae, or Eukarya – Microbes indispensable to life: produce half of Earth’s O2, nitrogen fixation, decomposition, and over half of Earth’s biomass. More bacterial than human cells in your body Viruses: Making a Living by Hijacking Cells • Viruses are not regarded as living organisms; lack some attributes of life. – Are infectious particles, incapable of replicating independently. – Lack cellular organization and metabolism. – Consist of RNA or DNA usually enclosed in protein coat (viroids viroids lack protein coat). Viruses: Making a Living by Hijacking Cells • Invade host cell and direct its genetic machinery to churn out multiple copies of virus. • Most viruses composed of three large-scale structures. – Genetic material in its core (DNA or as in HIV two strands of RNA) – Capsid protein coat. – Fatty membrane envelope with spike-like proteins on the surface that enable binding to target host cell. Viruses: Making a Living by Hijacking Cells • Invading the host cell. – Life Cycle: Binding and fusion with target host T-cell followed by reverse transcriptase creating DNA copy of viral RNA and then integrase allows integration of viral DNA into host chromosome. May remain dormant but can be triggered to enter replication phase. Viruses: Making a Living by Hijacking Cells • Invading the host cell. – Here the viral genetic material directs synthesis of more copies of itself and protein coat; these components then assemble themselves into viral particles; activity of an enzyme is then triggered, which leads to lysis of host cell and spread to other uninfected cells. Viruses: Making a Living by Hijacking Cells • Viruses infect many organisms, including bacteria (T4 injects its DNA inside bacteria), and are prevalent (1 ml of sea water has 10 million viral particles). Essay: An Unwanted Guest: The Persistence of Herpes • 1/5 Americans over 12 infected. • Caused by Herpes simplex viruses (cause chickenpox, shingles, and the Epstein-Barr disease). • Herpes simplex type 1 usually “oral,” type 2 usually “genital.” But either variety can end up in either location. Essay: An Unwanted Guest: The Persistence of Herpes • The herpes sores are the result of newly formed virus particles breaking out and destroying skin cells. • Lies dormant after initial infection by migrating up axons to the nucleus inside the cell body. • Stresses like UV light can trigger re-eruption. Viruses: Making a Living by Hijacking Cells • Effects on plants, and animals; cause much agricultural loss, mild to deadly human diseases (smallpox, chicken pox, measles, mumps, colds, flu, polio, herpes, rabies, AIDS, some types of cancer). Essay: Not Alive, but Deadly: Prions and “Mad Cow’’ Disease • Unusual for a transmissible human diseases because its cause is component part of a living thing –a misshapen version of a normal protein. Responsible for Creutzfeldt-Jakob disease, and also Mad Cow disease. Bacteria: Masters of Every Environment • Characteristics of bacteria. – Lack cell nucleus, as do all prokaryotes (eukaryotes have nucleus). – No membrane-bound organelles, no cytoskeleton. – DNA present as single chromosome; haploid organisms. – Reproduction is asexual, by simple splitting (binary fission); daughter cells genetic clone of parent cell. Bacteria: Masters of Every Environment • Characteristics of bacteria. – Are single-celled, extremely small. . Bacteria: Masters of Every Environment • Characteristics of bacteria. – Bacteria varied in shapes. • Cocci—spherical. Cocci • Bacilli—rod-shaped. Bacilli • Spirochetes—spiral-shaped. Spirochetes Bacteria: Masters of Every Environment • Bacteria exist in staggering numbers in a wide range of habitats. – Microflora of human gut includes 600 species of bacteria in mouth alone; 100 trillion bacteria in digestive tract, equal to number of cells in human body. 10,000 different species in a handful of earth, the number of individual bacteria in mouth probably exceeds number of people ever existed, onequarter of feces by weight consists of bacteria. Bacteria: Masters of Every Environment • Bacteria exist in staggering numbers in a wide range of habitats. – Nitrogen-fixing bacteria have symbiotic relationship with some plants—convert molecular nitrogen into forms usable by plant; nitrogen needed by animals comes ultimately from plants. We also get various sugars and vitamins for our diet from resident bacteria. – Bacteria play an important role as decomposers (as in city sewage plants). Bacteria: Masters of Every Environment • Intimate Strangers: Humans and Bacteria. – Mutualism: relationship between two organisms that benefits both. • Rats with digestive bacteria wiped out require 30% more calories to maintain body weight, because they have a lower number of intestinal cells that move nutrients. • Metabolize sugars we cannot digest and produce some vitamins. Bacteria: Masters of Every Environment • Bacteria and Human Disease. – Some bacteria are pathogenic, disease-causing: tuberculosis, syphilis, gonorrhea, cholera, tetanus, botulism, leprosy, typhoid fever, and diphtheria, food poisonings and blood-borne infections,bubonic plague, Anthrax (Bacillus anthracis). – Damage comes from substances secreted or left behind (toxins, substances that harmfully alter living tissue or interfere with biological processes). Bacteria: Masters of Every Environment • Bacteria and Human Disease. – Antibiotics must exploit differences in cell biology of bacteria and humans to keep from harming patient (e.g., penicillin destroys bacterial cell walls, but has no effect on animal cells). – Threat of antibiotic resistance. Half antibiotics go to livestock in animal feed as growth stimulants. Essay: The Discovery of Penicillin • Antibiotics are used to kill bacteria. – Originated from fungi. Essay: Modes of Nutrition • Autotrophs. – Photoautotrophy—use light energy and carbon dioxide to create energy-rich carbon compounds, as do plants, some bacteria, and many protists. – Chemoautotrophy—use inorganic compounds (hydrogen sulfide, ferrous iron) to fix carbon from carbon dioxide. Some bacteria and archaea. Essay: Modes of Nutrition • Heterotrophs. – Obtain energy from organic material, as do animals and fungi. – Photoheterotrophy, uses sunlight for energy, but the carbon comes from surrounding organic material. Some bacteria and archaea. – Chemoheterotrophy, in which organic materials (better known as food) act as both carbon supplier and energy source Almost all animals, all fungi, most bacteria, many protists, and a few plants. Domain Archaea: From Marginal Player to Center Stage • Newly recognized as ancient group of prokaryotes, possibly ancestral to all life. – Divergent from all other life-forms; most genes (from Methanococcus) unique to group, not previously known to science. Are prevalent; 30 percent of microscopic organisms living off Antarctica are Archaea. – Are microscopic, single-celled, lack nuclei. Domain Archaea: From Marginal Player to Center Stage • Some live in extreme environments (extremophiles). – High or low temperatures, high pressure, high salt, extreme pH. – Hard to culture in lab, therefore little known. – Of great interest to biotechnologists. Protists: Pioneers in Diversifying Life • Protista are grab-bag category of eukaryotes, defined by what they are not – Are not plants, fungi, or animals. – Most are single-celled, most in moist or aquatic habitats. – Some are photoautotrophic, some are ingestive heterotrophs, some are capable of both modes of nutrition. Protists: Pioneers in Diversifying Life • Plants evolved from one group of protists (green algae), animals from another (probably choanoflagellates), fungi from yet another (probably chytrid-like Protista). • Movement powered by flagella, cilia, or pseudopodia. • Some protists are colonial; may have been a steppingstone toward multicellularity. Protists: Pioneers in Diversifying Life • Some protists are multicellular. – Significance of multicellularity—makes division of labor among cells possible; greater tissue complexity. – Some seaweeds (multicellular) can be enormous— giant kelps grow 60m in a year. – 100,000 known species. Protists: Pioneers in Diversifying Life • Some protists are multicellular. – Harmful to humans: Plasmodium falciparum, causes malaria; intestinal parasite Giardia contaminates water causing diarrhea if ingested; sleeping sickness, and amoebic dysentery caused by protists. 1840s Irish Potato Famine caused by fungus-like protist, Phytophthora infestans. Close relative, Phytophthora ramorum, is now wiping out stands of California oak trees and bay laurels. Protists and Sexual Reproduction • Most reproduce by cell-splitting, but some evolved sexual reproduction. – Ancient, early-evolving protist, single-celled algae Chlamydomonas usually divides through cell-splitting, but under nutritional stress two haploid cells fuse to create a zygote which then undergoes meiosis to create four new offspring with combinations of the original parental chromosomes. – Two mating types (+ and – differ in whip-like flagellar structures). Plant-Like Protists • “Golden” alga, freshwater Synura scenedesmus shows transition between the single-celled and multicelled life; Exhibit colonial multicellularity: individual cells form stable associations with one another but do not take on specialized roles. Plant-Like Protists • Volvox, green algae, has true-multicellularity (individual cells exist in stable groups, with different cells in a group specializing in different functions. Colony of 500-60,000 cells forming a sphere use their flagella to move. Not all cells in colony reproduce, only select group without flagella. As such, Phytoplankton are single-celled protists called algae. Plant-Like Protists • Brown alga —giants of the protist world (sea kelp 100 meters long), notable for organized assemblages of cells that conduct food (leaf-like “blades” and stem-like “stalks”). • All are phytoplankton: small photosynthetic organisms in ocean surface, perform much of Earth’s photosynthesis at base of food web, produce much of its oxygen. Sustain aquatic food chains—zooplankton eat them, and in turn are eaten by larger animals and other heterotrophs; some whales feed on plankton directly. Animal-Like Protists • Formerly protozoa), do not obtain nutrients from photosynthesis, instead from consumption and internal digestion. • Paramecium. – Takes food in through gullet, digests in a food vacuole, and then empties the resulting waste into the outside world through an exterior pore. Some species even have tiny dartlike structures (called trichocysts) that they can shoot out when threatened. Animal-Like Protists • Paramecium. – Ameboid protists use pseudopods, take in food by endocytosis. – Examples. • Entamoeba hystolytica, ~ 100,000 deaths per year, mostly in the tropics, by entering the human digestive system through contaminated water (amoebic dysentery). Animal-Like Protists • Paramecium. – Examples. • Giardia lamblia, reason not to drink stream or lake water without filtering, boiling, and/or treating it (with iodine or chlorine). Lives in small intestines of humans and other animals. Symptoms include nausea, diarrhea, and vomiting. It gets around by pairs of whip-like flagella like algae protists. Fungi-Like Protists • Fungi obtain nutrients by sending out slender filaments, releasing digestive enzymes and then absorbing the nutrients. Fungus-like protists, oomycetes, operate the same way. • Examples. – Irish Potato Famine, Phytophthora infestans. – Water mold (saprobes) saprobes), saprobes) organisms that obtain their nutrition from dead organic matter. Fungi-Like Protists • Examples. – Plasmodial slime mold: several forms during its life-cycle. Fuses plasma membranes of many cells resulting moving mass of cytoplasm with multiple nuclei; moving by “cytoplasmic streaming,” it consumes underlying bacteria, fungi, and bits of organic material. Like fungi, when nutrition is scarce, it changes shape, forming a structure that releases fungus-like spores. Fungi-Like Protists • Examples. – Dictyostelium discoideum, “cellular slime mold” can exist as individual microscopic cells, but if its bacterial food runs low, individual cells aggregate and develop into a migrating “slug” of up to 100,000 cells which can finally arrange into a stalk-like reproductive structure that releases spores from its apex.