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Approximately 10 trillion cells in human body10 bacteria/archaea cells to every human cellIn total volume, bact/archaea cells are dominantBiological Impact:AbundantLive in diverse habitatsFound almost everywhere and anywhereSome thrive in extreme environments- extremophilesHigh salt, high temp., high pressure habitatsCan help with understanding the origin of lifePredicted that the First life forms lived in these environmentsCommercial applications- since their enzymes work in extreme conditions, they can be used in researchMedical importanceOnly a fraction of the thousands of bacterial species in your body can disrupt bodily functions enough to cause illnessThese disease causing bacteria are pathogenicTend to affect tissues at the entry points to the bodyKoch’s postulates:Hypothesized that bacteria was responsible for infectious diseasesTested the hypothesis by seeing what caused anthraxFour criteria had to be met:1) microbe present in infected & absent in healthy ppl.2) organism must be isolated and grown in pure culture3) if injected into a healthy person, symptoms should appear4) organism should be isolated again and should be the sameSome things don’t always work:Can’t grow every bacteria in cultureThe Germ Theory (of disease):Certain diseases are infectious and can be passed ppl to ppl.Bacteria and viruses can be passed by transmission and grownLaid the foundation for modern medicineGreatest impact initially was on influencing sanitizationPathogenic bacterial cellsVirulence- the ability to cause diseaseHeritable trait that varies among individuals in a populationGenomes of some cells in the same species are larger than others because the pathogenic cells have acquired virulence genes (making them able to cause a disease)Toxin proteins are coded by virulence genesThey inhibit protein synthesis by ribosomesAntibiotics (past, present and future)- molecules that kill bacteriaProduced naturally by soil-dwelling bacteria and fungiAntibiotics in soil are predicted to help cells reduce competition for nutrients and resourcesAt first- gave doctors effect weapons against bacterial infectionsNow- many bacteria are now drug-resistant, some even eat antibioticsAnother advantage of bacteria- biofilmsDense colonies covered by a polysaccharide-rich matrix that protects bacteria from antibioticsRole in Bioremediation: cleaning up sites polluted with organic solventsArchaea and bacteria can be helpful in this techniqueThey can grow in the spills and degrade the toxinsCan be enhanced by two complementary bioremediation strategies:Fertilized the sites to encourage growth of bacteriaSeeding or adding specific bacteria to sitesHow we study Bacteria/Archaea:Enrichment Cultures- technique to isolate new typesEstablish certain growing conditions and seeing which cells thrive in these conditionsCreate an abundant amount of bacteria sample to study fartherMetagenomics- analysis that allows biologists to quickly identify organisms that have never been seen beforeExtract and sequence the DNA from a sample and identify species & biochemical pathways by comparing to known genesPhylogenetic Trees- use of small subunits of RNA found in ribosomes to create these trees (16S and 18S RNA)Based on the data from ribosomal RNA molecules, the major divisions of life are:BacteriaArchaeaEukaryaDiversity of bacteria and archaea:Morphological diversity:Bacteria onlySize: bacteria range from smallest of all free living cells to a billion sizes largerShape: range in shape from filaments, spheres, rods, chains and spiralsMobility: can move by rotating flagella; can either move ahead or tumble, gliding also occurs but we don’t know howCell wall differences b/w bothGram staining- only for bacteria with cell walls; helpful in determining which drugs to use against bacteria+ = purpleplasma membrane surrounded by cell wall with extensive peptidoglycan- = pinkplasma membrane with thin peptidoglycan surrounded by phospholipid bilayer on outsideMetabolic Diversity- chemical rxns that go on inside the cellsVery diverse in the compounds they can use as foodProducing ATP:Phototrophs- light feeders, use light to excite electronsChemotrophs- inorganic or organic materials serve as electron donors and are oxidizedCarbon source:Autotrophs- organisms that make their own building blocks from simple starting compounds (CO2, CH4) “self feeders”Heterotrophs- absorb ready to use organic compounds from their environment; acquire from other compounds “other-feeders”Bacteria/archaea can be all different mixes of the aboveEvolution allowed variations of these mixes to live in diverse habitatsVARIATIONS IN METABOLISMProducing ATP through Cellular RespirationMany bacteria and archaea vary in their electron donors and electron acceptorsEukaryotes usually use CO2 to donate and O2 to accept but bact./arch. Can use other moleculesThings with high potential energy are donors, low potential energy molecules are electron acceptorsProducing ATP through Fermentation:No outside electron acceptor is used, so it is much less efficientBacteria and archaea are able to ferment things other than glucose (which is usually the starting point for fermentation)Producing ATP through Photosynthesis: (variation in electron sources/pigments)Phototrophs can perform photosyn. In three ways:1) Chemiosmosis drives synthesis of ATP2) Some use radiation instead of light (in hydrothermal vents)3) As electrons are passed from high to low energy states, the energy released is used to create ATPSpecies that use water as their electron source are oxygenic (“oxygen-producing”)Others that don’t use water are called anoxygenic (“non-oxygen producing”)Many different pigments have been discoveredObtaining building-blocks from compounds (CARBON):Not all use the Calvin cycle to make building block moleculesNot all start with CO2 as the source of carbon atomsBacteria and archaea can use different starting materials and different pathways to create building blocksGlobal Impacts:Oxygen revolution:Cyanobacteria were the first to perform oxygenic photosynthesisAerobic respiration was now a possibility and oxygen could be used as a final electron acceptorA huge increase in concentration of oxygen in the atmosphere occurredNitrogen fixation and the nitrogen cycle:N2 is hard to break and use since it has triple bondsOnly some bacteria and archaea can use molecular nitrogen to convert it into ammonia (NH3) aka nitrogen fixationNitrogenase- responsible enzyme for n


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Pitt BIOSC 0160 - Bacteria and Archaea

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