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Transcript
MICROBIOLOGY - ALCAMO LECTURE: CRITERIA FOR PROKARYOTES & EUKARYOTES Introduction - Cells • All living organisms have cells • Basic unit of structure • Large organisms – many cells • Cells are organized into: – Tissues – stomach lining – Organs – esophagus, stomach, intestines – Systems – digestive system MICROORGANISMS One or a few cells take care of all functions Prokaryotic Cell: • No nuclear membrane • No other internal membranes (no organelles) • Only has a cell membrane • Examples – bacteria, cyanobacteria . PROKARYOTES - They are very small cells - They have a very thin cell wall: - Shape - Protection - They have a cell membrane: - Lines the cell wall - Regulates molecular traffic - They have a nucleoid or nuclear region where their one, looped molecule of DNA resides PROKARYOTES - Their cytoplasm is a soup of chemicals (including free ribosomes), where all cell activities take place - They may contain a flagella – a long hairlike appendage made of protein and responsible for motion in MO’s - May have one or many - Made of protein flagellin - Movement is chemically driven - chemotaxis Eukaryotic Cell: •Has a nuclear membrane •Has other membrane bound organelles: mitochondria Golgi bodies endoplasmic reticulum •Examples – animals, plants, fungi, protozoa, unicellular algae EUKARYOTES - They are larger cells than the prokaryotes - They may have a 3 layer cell wall: - Shape - Protection - They have a cell membrane: - Lines the cell wall - Regulates molecular traffic - They have a nucleus with a nuclear membrane: - Double stranded DNA (chromosomes) - RNA . - They have a cytoplasm – Soup of chemicals containing membrane bound organelles for all cell activities - They may have a flagella – - cable-like - Made of tubulin protein - Arranged in a microtubule array of 9 doublets around 2 singlets Prokaryotic vs. Eukaryotic Cells Characteristic Prokaryotes Eukaryotes Nucleus Absent Present with nuclear membrane Organelles Absent Present in a variety of forms DNA Structure Single closed loop Naked strand with no protein Multiple chromosomes Protein associated with DNA Chlorophyll When present – dissolved in cytoplasm When present –contained in chloroplasts Ribosomes Smaller and free in cytoplasm Larger and often bound to membranes Cell walls Present and complex Present /absent and simple Reproduction Fission – no mitosis Mitosis Examples Bacteria, Cyanobacteria Fungi, protozoa, plants, animals, humans Classification of Organisms -Eukaryotes - all multicellular organisms and unicellular organisms (except 2) Examples: mammals, fish, plants, fungi, algae and protozoa -Prokaryotes – (the other 2) only bacteria and cyanobacteria Microorganism Size • Micrometer – unit of length most commonly used (1/1,000,000 of a meter) • MO’s range in size from almost visible protozoa (100um) down to incredibly small viruses (0.01 um) • Most bacteria are 1 – 5 um in length Bacteria • Prokaryotes and one of the most abundant organisms on earth • Can affect us positively (digest sewage, extract N from air for plants, break down dead and decaying matter) • Can be harmful to us (produce toxins in our bodies, infect plants and animals, etc) • Are able to live under almost any conditions (arctic ice, hot springs, ocean trenches, acidic conditions, no oxygen) Small Bacteria • Rickettsiae barely seen with light microscope • Transmitted by arthropods such as ticks and lice • Can cause Rocky Mountain spotted fever and typhus fever Small Bacteria • Chlamydiae – even smaller than rickettsiae and can’t be seen with light microscope – One species causes the gonorrhea-like disease known as chlamydia • Mycoplasmas – smallest known bacteria and do not have cell walls – Can cause one form of pneumonia and one type of sexually transmitted disease Cyanobacteria • Used to be known as blue-green algae, but are more closely related to bacteria • They are prokaryotes and have light trapping pigments for photosynthesis • Many are blue, but some are black, green or red (Red Sea) • Inhabit freshwater and marine environments (ponds turn green, need algicide in pools) Protozoa • Single celled microscopic eukaryotes • Some cause diseases such as malaria and sleeping sickness • Come in many shapes and sizes and some are capable of photosynthesis • Classified according to how they move (flagella, cilia, cytoplasmic extensions called pseudopodia) Cilliate Amoeba Fungi • Primary decomposers of organic matter in the world • Can cause human diseases such as athlete’s foot • Used to be classified as plants but: – Don’t do photosynthesis – must obtain preformed food – Cells have different cell wall Fungi • Eukaryotic organisms – 2 groups: – Yeasts – unicellular, ~ size of large bacteria • Play a vital role in fermentation of beer and wine and production of bread – Molds – long chains of cells seen as fuzzy masses Yeast Mold Unicellular Algae • The term algae refers to any plant-like organisms that practice photosynthesis and differ structurally from land plants • Two important algae for microbiology: – Diatoms – Dinoflagellates Diatoms • Eukaryotic marine organisms • They are photosynthetic – make carbohydrates – passed on to other marine organisms when they are eaten • Cell walls are impregnated with silicon dioxide (glasslike) • When they die their remains accumulate on the sea floor as diatomaceous earth (used to produce filters) Dinoflagellates • Photosynthetic eukaryotes • Important in the world’s food chains • They can also produce periodic red tides in the oceans Viruses • Neither prokaryotes nor eukaryotes • They are non-cellular, do not grow, do not show any nutritional pattern • Only observable activity is replication, which can only be done inside a living cell • They are just a fragment of DNA or RNA inside of a protein sheath • Cause many human diseases – flu, polio, hepatitis, chickenpox