MICROBIOLOGY EBIO 3400
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This 3 page Study Guide was uploaded by Madisen Robel on Thursday October 29, 2015. The Study Guide belongs to EBIO 3400 at University of Colorado at Boulder taught by Steve Schmidt in Fall. Since its upload, it has received 53 views. For similar materials see /class/231848/ebio-3400-university-of-colorado-at-boulder in Ecology, Evolution, and Marine Biology at University of Colorado at Boulder.
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Date Created: 10/29/15
Review for Final Study Old exams I will reuserewrite some of those questions RCVlCW big themes see the rest of this lecture and last lecture Anaerobic respiration Same thing but with a different e39 acceptor AH2 B A BH2 For anaerobic chernoheterotrophs anaerobic respiration CHZO No3 co2 N20 See Fig 68 Remember from lec 2 Kluyver and van Niel proposed that all respiratory reactions aerobic and anaerobic could be summarized using the simple formula AH2 B A BH2 Aerobic Resp For Beggiatoa example of aerobic respiration SH2 02 so H20 For aerobic chernoheterotrophs example of aerobic respiration CHZO 02 co2 H20 All catabolic reactions are oxidationreduction reactions 7 it s all about movement of electrons An extreme illustration of this is Geobacter sulfurreducens Delmerteobacteria it can use metal electrodes as electron acceptors for anaerobic respiration It is now being tested in microbial fuel cells to generate electricity It can use acetate as its e39 quot 39 39 39 39 39 oxidation of acetate to onor carbon dioxide A on t I k I M 39 I to side ofthe batery Please read the abstmctto this paper Electricity Production by Geobacler sullurreducens Attached to Electrodes Appl Environ Microbiol 69 1548 1555 D P Eondamp D P Lovley Full paperl on cla Web lie u39 39y uu i my unmian Appl Environ Microbiol 69 1548 1555 DR Bond amp DR Lovley Previous studies have suggested that members of Geabacter can use electrodes as electron acceptors for anaerobic respiration In order to better understand this electron transfer process for energy production 6 sulfurreduoenswas inoculated into chambers in which a graphite e ectrode served as the sole electron acceptor and acetate or hydrogen was the electron donor The electronaccepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium fuel cells or to potentiostats that poised electrodes at 02 V versus an AgAgCl reference electrode poised potential When a small inoculum of G 39 J 439 t 39 t quot t 39 39 g c ambers electrical re production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially indicating for the first time that electrode reduction supported the growth of this organism When the medium was replaced with an anaerobic buffer lacking nutrients required for growth acetatedependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks This represents the first report of microbial electricity production solely by cells attached toan electrode Electrodeattached cells completely oxidized acetate to levels below detection lt10le and hydrogen was metabolized to a threshold of 3 Pa The rates of electron transfer to electrodes 021 to 12pmol of electronstrig of proteinmin were similar to those observed for respiration with Fe citrate as the electron acceptor Eo39 O37 V The production of current in microbial fuel cell 65 mAm2 of electrode surface or poisedpotential 163 to 1143 mAm2 mode was greater than what has been reported for other micro 39al systems event ose that employed higher cell densities and electronshuttling compounds Since acetate was completely oxidized the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing quot 39 39 39 of 39 electrod wlul 1 As an illustration Rabbits in Australia Rabbits were first introduced to Australia from England in 1859 Because they had no natural enemies they soon became major pests Finally in 1950 a scientist isolated a Myxoma virus that caused a not very serious disease in a species of Brazilian rabbits When this Virus was brought to Australia it was a new disease to those English rabbits it was extremely virulent to them Within a year 999 of all the rabbits in Australia died Over the following 20 years scientists closely monitored the co evolution of this new disease and the rabbits of Australia The main finding of these studies was that the Virulence of the Virus decreased each year and the resistance of the rabbits increased Finally after about ten years the number of rabbits in Australia increased back up to about 20 of their pre virus levels Evolution of diseases In many cases the longer a population is exposed to a pathogen the less susceptible that population is to the disease Over the short term months to years this is due to the fact that more hosts become immune Over the long term this is due to natural selection which tends to weed out extremely virulent pathogens because if they kill all of their hosts then they too will go extinct Simultaneously hosts that are more resistant to a prevalent pathogen have more offspring Thus through evolutionary time specific pathogens tend to become less virulent to their hosts become more resistant to their pathogens It is thought that some non pathogenic relationships evolved from former antagonistic ones via a progression like this Pathogenic gt Commensalistic gt Mutualistic Two important points about the above story 1 The long term change in the rabbits was genetic ie more resistant rabbits were selected for 2 It took about ten rabbit generations assuming 1 generation per year for the rabbits and virus to reach a equilibrium in which the rabbit was quite resistant and the virus was much less virulent Let s quickly review that with an overhead Of course not all diseases evolve exactly like the rabbitmyxoma case Co evolution is a back and forth process that can lead to a balance as in the rabbitmyxoma case or to either the pathogen or the host gaining advantage at any point in time And evolution can lead to re emergence of diseases like the u plague and other diseases we have discussed Emerging Infectious Diseases The rabbit story is pertinent to how and why new diseases keep cropping up see Lecture 23 From Lec 23 Fig 2010 Some emerging infectious diseases Most are old diseases that are re emerging or diseases thatjump from animals to humans HIV Ebola Some reasons for emerging diseases 0 climate change 0 Over use of antibiotics human encroachment on wilderness use of wild animals as food 0 increased international travel faster dispersal of new pathogens From Lec 23Emerging Diseases New reemerging or drugresistant infections whose incidence in humans has increased within the past two decades or whose incidence threatens to increase in the near future Know reservoirs vectors and pathogens including where on the big tree they fall for diseases we have discussed Also try to understand why they are on the increase or emerging Emerging diseases AIDS jumped from animals Anthrax biological warfareterrorism Cholera disruptions in public sanitation due to poverty tsunamis etc Tuberculosis antibiotic resistance AIDS breakdown in public health West Nile Virus international travel Whooping CoughPertussis lax immunization programs Yellow fever global warming Flu jumps from animals every year Plague could reiemerge due to large reservoirs and lack of public awareness Prion diseases poor practice in feed lots and burger industry
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