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Bacteria RTN 470-477 Robert Hooke, van Leeuwenhoek: invention of microscope(17th century) first to observe bacteria Prokaryotes – unicellular organisms that lack a nucleus = bacteria Size = 1-5 micrometers (1 micrometer = 1 millionth of meter) most smaller than eukaryotes (cells with nucleus) CLASSIFYING PROKARYOTES(BACTERIA) Monera – Old grouping Eubacteria separate kingdom than Archaebacteria Domain – a level of classification higher than a kingdom; some biologist think that the 2 types of bacteria are so fundamentally different that they should be in their own domain EUBACTERIA Larger of the 2 kingdoms of bacteria Habitat = fresh water, salt water, land, on and within the human body o Example: Escherichia coli – found in human intestine Cell wall – determines bacteria’s shape/protects o Peptidoglycan= carbohydrate o Pili – involved in cell to cell contact o Flagella used for movement Cell membrane – surrounds cytoplasm - contains ribosomes- and DNA See figure 19-2 ARCHAEBACTERIA Do not have the peptidoglycan found in eubacteria Different membrane lipids DNA sequences of genes more like eukaryotes than eubacteria Think that archaebacteria are more closely related to eukaryotes Habitat – extremely harsh o Methanogens – oxygen free areas - guts of animals, thick mud, produce methane gas o Salty environments o Hot springs Identifying Prokaryotes Shape, Rod shaped = bacilli Spherical = cocci Spiral, corkscrew = spirilla chemical nature of cell walls, Gram stain – primary = violet Peptidoglycan(thick layer) absorbs violet color – then wash with alcohol, and stain persists = gram + Gram - = peptidoglycan(thin layer) surrounded by lipid layer – lipid dissolved by alcohol – thus stain is washed out of peptidoglycan layer - appear pink or light red Movement – No movement Flagella propelled Lash, snake, spiral forward Glide smoothly Metabolic Diversity – best means of identifying different bacteria HETEROTROPHS – Most bacteria Obtain E by consuming organic molecules made by other organisms need carbon Chemoheterotrophs – most animals are chemoheterotrophs Photoheterotrophs – photosynthetic, and need organic compounds for carbon source AUTOTROPHS Photoautotrophs – use light E to convert CO2 + water to carbon compounds and oxygen – just like plants Found in upper surfaces of water bodies Cyanobacteria – bluish pigment and chlorophyll a – key pigment in photosynthesis – UBIQUITOUS – first colonizing species “black” ring around rocks at ocean or lake edge Chemoautotrophs – make organic carbon molecules from Carbon dioxide – NO LIGHT- use chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur or iron as E source - some live in ocean vents – obtain E from hydrogen sulfide gas from hydrothermal vents on deep ocean floor RELEASING ENERGY Energy is released by: cellular respiration, fermentation or both OBLIGATE AEROBES – require Oxygen example – Mycobacterium tuberculosis OBLIGATE ANAEROBES – no oxygen – oxygen can kill OBLIGATE ANAEROBES(cont) Ex – Clostridium botulinum – found in soil or can grow in canned food that was not sterilized (BOTOX) FACULTATIVE ANAEROBES - don’t require Oxygen , but are not harmed by oxygen - can switch between cellular respiration( oxygen present) - fermentation(oxygen absent) – can live ANYWHERE Example – Escherichia coli – anaerobic in our intestine; aerobic in contaminated water GROWTH AND REPRODUCTION FOOD availability and Waste production limit the growth of bacteria (which can be as fast as every 20 minutes!!) BINARY FISSION – DNA replicated and cell divides 2 identical daughter cells Asexual since no exchange or recombination of DNA CONJUGATION - DNA is exchanged Hollow bridge forms between 2 cells Allows for genetic diversity in population SPORE FORMATION – when growth is unfavorable spores are formed = ENDOSPORE – remain dormant for long periods, Ex; Bacillus anthracis – “anthrax” IMPORTANCE OF BACTERIA Bacteria are vital to maintaining the living world Producers – capture E by photosynthesis Decomposers – break down nutrients in dead matter Human use Decomposers – bacteria – recycle nutrients back into ecosystem Decomposers (cont) – break down complex compounds in sewage, to produce pure water, nitrogen and Carbon dioxide gases, and products to make fertilizers NITROGEN FIXERS – (remember the nitrogen cycle??) Plants need N to make amino acids (protein synthesis) N gas = 80% atmosphere not usable by most organisms Bacteria can transform Ngas into NH3 (ammonia) = nitrogen fixation – SYMBIOTIC RELATIONSHIP OF plants and N fixing bacteria Example – legumes, soybeans, host Rhizobium bacteria Grows in nodules or knobs on roots – both organisms benefit (symbiosis) HUMAN USES of Bacteria Bacteria used in production of foods and beverages Used in Industry Digests petroleum – for use in oil spills Removal of waste and poison in water Mine minerals Synthesize drugs and chemicals through genetic engineering(insulin production) E.coli – in human colon(thus its name) synthesize vit K for us( calcium absorption, blood clotting) Biotechnology – archaebacteria – extreme environment bacteria – produce heat stable enzymes – used in medicine, food production industrial chemistry