《环境工程微生物学》课程扩展资料（scientist microbiology from Harvard）Genes that are Universal to Life

Hypothesis: That lifeonMarswill be related to lifeon EarthWhy?AtthepointofmassivemeteoriticexchangebetweenMarsand Earth,life had already evolved to modern cellularforms andmetabolism.AndMarswasprobablywetterand warmer.How doesthishelp us look for life on Mars?1.alllifeonEarthisrelatedtoacommonancestor2. one particular gene, the 16S gene, has changed theleast overthepast3.5billionyearsandispresentinallknownlife3.anextremelysensitiveandspecificDNA-based lifedetectorthattargetsthisgeneisnowusedtoprospectfordiverselifeonEarth.4.if life on Mars sharesthat commonancestor,wecan detectitusingthis lifedetectiontechnology.Theinstrument:a 1.5 kg thermal cycling soil analysispackagethatamplifies andanalyzes the16SgeneinsituonMarsThe life signature: a DNA sequence with predictable features thatcannot be generated abiotically

Hypothesis: That life on Mars will be related to life on Earth Why? At the point of massive meteoritic exchange between Mars and Earth, life had already evolved to modern cellular forms and metabolism. And Mars was probably wetter and warmer. How does this help us look for life on Mars? 1. all life on Earth is related to a common ancestor 2. one particular gene, the 16S gene, has changed the least over the past 3.5 billion years and is present in all known life 3. an extremely sensitive and specific DNA-based life detector that targets this gene is now used to prospect for diverse life on Earth. 4. if life on Mars shares that common ancestor, we can detect it using this life detection technology. The instrument: a 1.5 kg thermal cycling soil analysis package that amplifies and analyzes the 16S gene in situ on Mars The life signature: a DNA sequence with predictable features that cannot be generated abiotically

There was already life on Earth during the period ofintense exchange with a warmer and wetter Marsfossilized bacterial3.5-forms3.63.7-3.8BombardmentPeriod:isotopicevidence3.9-1.106 to109Earth ejecta of.3to6meterforlifeonEarthnotheatedabove100°C4.02.Transittimes107yearsorless--survivalofmicrobespossible4.1-3.Arrive on awarm and wet Mars4.2-calculatedbyMileikowskyetal (lcarus145:391-427)4.3-4.4Lunarformation4.54.6Planetaryformationbillions of years ago

3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 4.3 4.4 4.5 4.6 billions of years ago Bombardment Period: 1. 106 to 109 Earth ejecta of .3 to 6 meter not heated above 100°C 2. Transit times 107 years or less-survival of microbes possible 3. Arrive on a warm and wet Mars calculated by Mileikowsky et al (Icarus 145: 391-427) There was already life on Earth during the period of intense exchange with a warmer and wetter Mars isotopic evidence for life on Earth fossilized bacterial forms Lunar formation Planetary formation

Launchand reentry:Possibleacceleration to escape velocity and deceleration from escapevelocity without majorheating:for a 1to 2o Km impactor,108lowtemperatureejectaOrbiting ejecta,at slightly lessthan escapevelocityarerefugia to microbes (but not dinosaurs) duringbombardmentperiodBlackbodytemperaturebetweenMarsandEarth130-200degK.Atmosphericentryof10sKm/secobjecttakesafewseconds.Transit:TransittimebetweenMarsandEarthlessthan10,000,000yearsfor5%6metersof rock can protect vs cosmicand solar radiationforhundredsofmillionsofyears

Launch and reentry: Possible acceleration to escape velocity and deceleration from escape velocity without major heating: for a 1 to 20 Km impactor, 108 low temperature ejecta Orbiting ejecta, at slightly less than escape velocity are refugia to microbes (but not dinosaurs) during bombardment period Black body temperature between Mars and Earth 130- 200 deg K. Atmospheric entry of 10s Km/sec object takes a few seconds. Transit: Transit time between Mars and Earth less than 10,000,000 years for 5% 6 meters of rock can protect vs cosmic and solar radiation for hundreds of millions of years

SurvivingonMars1.Waswarmer and wetter3.5 billionyears ago2.Marslostitsatmosphereas itsmagneticfielddecayedsothat3.Uvisnow1oo0xmoreintenseonMarsthanEarth4.Low UV is probably a recent invention on Earth,afterphotosynthesisevolved5.HighUvfluxmaybetheancestral stateinwhichlifeactuallyevolved6.HighUv isoxidizing,butoxidantssupply metabolic energyby acceptingelectronstransferredbytheelectrontransportchainAstrobiologists worrytoo muchabout UV....chill outdudes.Thekeyis whereisthe watertoday and how muchis needed for life.MicrobesinoasesshouldbedetectablebyPCRifviableorganismsblowaroundinthewind

Surviving on Mars 1. Was warmer and wetter 3.5 billion years ago 2. Mars lost its atmosphere as its magnetic field decayed so that 3. UV is now 1000x more intense on Mars than Earth 4. Low UV is probably a recent invention on Earth, after photosynthesis evolved 5. High UV flux may be the ancestral state in which life actually evolved 6. High UV is oxidizing, but oxidants supply metabolic energy by accepting electrons transferred by the electron transport chain Astrobiologists worry too much about UV.chill out dudes. The key is where is the water today and how much is needed for life. Microbes in oases should be detectable by PCR if viable organisms blow around in the wind

Some common features of life on EarthDNA,RNA,proteins(core=500)biochemistry1micron3ATPH+H+H+H2=2H++2e-orNADHH+H+ reductant,e.g.H2carbonoxidant(e.g cO2ors0)H+ H+source,e.g. c02

reductant, e.g. H2 carbon source, e.g. CO2 biochemistry DNA, RNA, proteins (core=500) ATP H+ H+ H+ H+ H+ H+ H+ H2= 2H+ + 2e-or NADH Some common features of life on Earth 1 micron3 oxidant (e.g CO2 or S0)

CO2InorganiccompoundProtonElectronCarbonATPflowmotiveflowforce+so02SO42-NO3Biosynthesis(b)Chemolithotrophicmetabolism

PeriplasmCellmembraneFe3+CellwallFe2+Out(pH2)RusticyaninH+H+H+cytccytaNAD+12e1/2022H+H20In (pH 6)ADPCO2+ATPATPNADHCalvincycle

Eo (M)CoupleExamplesofreactions-0.50withH,asedonorCO2/glucose(-0.43)24e2H+/H2(-0.42)2e0.40CO,/methanol(-0.38)6e0.30NAD+/NADH(-0.32)2e(1)(1) H2 + fumarate?-→ succinate?-0.20CO,/acetate(-0.28)8eAG%=-86kJS/HS(-0.28)2e0.10SO2-/HS(-0.22)8e0.0Pyruvate/lactate(-0.19)2e-S.O62-/SO32-(+0.024)2e+0.10Fumarate/succinate(+0.03)2e+0.20(2)(2) H2 + NO → NO2 + H,OCytochromeboxreg(+0.035)1e+0.30AG= -163kJFe3+/Fe2+(+0.2)1e,(pH7)Ubiquinoneox/red(+0.11)2e+0.40Cytochrome Cox/red (+0.25)1e+0.50Cytochromeaox/red (+0.39)1eNO3-/NO(+0.42)2e+0.60+0.70WNO3-/%N（+0.74)5e(3) H, + 2 02 →H,0(3)+0.80-Fe3+/Fe2+(+0.76)1e,(pH2)AG%=-237kJ0/H0(+0.82)2e+0.90

515Fisoneuniversal16Sprimer5'GTGCCAGCAG CCGCGGTAAT3'UNIVERSALH.SAPIGGCAAGTCTG GTGCCAGCAG CCGCGGTAAT TCCAGCTCCA ATAGCGTATA650ANIMAL615X.LAEVGGCAAGTCTGGTGCCAGCAG CCGCGGTAAT TCCAGCTCCA ATAGCGTATAS.CERV601FUNGALGGCAAGTCTG GTGCCAGCAG CCGCGGTAAT TCCAGCTCCA ATAGCGTATA601P.MICAGGCAAGTCTGGTGCCAGCAG CCGCGGTAAT TCCAGCTCCA ATAGCGTATADINOFLAZ.MAYS605PLANTGGCAAGTCTG GTGCCAGCAG CCGCGGTAAT TCCAGCTCCA ATAGCGTATAGIARDIGCAAGGTCTGGTGCCAGCAG CCGCGGTAAT TCCAGCTCGG CGAGCGTCGC481PROTOZO516D.MOBIGGCAAGTCTG GTGTCAGCCG CCGCGGTAAT ACCAGCCCCG CGAGTGGTCGARCHAEA513S.SOLFGGCAAGTCTGGTGTCAGCCG CCGCGGTAAT ACCAGCTCCGCGAGTGGTCG513GGTAAGTCTG GTGTCAGCCG CCGCGGTAAT ACCAGCCCCG CGAGTGGTCAT.TENX500E0CY89GGCAAGTCGG GTGTCAGCCGCCGCGGTAAT ACCCGCTCCC CGAGTGGTGG20EOCY78GGCAAGGCTG GTGGCAGCCG CCGCGGTAAA ACCAGCTCCC CGAGGGGTTCGGCAAGTCTG GTGTCAGCCG CCGCGGTAAT ACCAGCCCCG CGAGCGGTCGPYRODIMPYRUSGGCAAGACCG CTGCCAGCCG CCGCGGTAAT AGCGGCGCCG CAAGTGGTGGT.CELRGGCAAGGCCG GTGGCAGCCG CCGCGGTAAT ACCGGCGGCC CGAGTGGTGG507ARGLB.GGCAAGGCCG GTGGCAGCCG CCGCGGTAAT ACCGGCGGCCCGAGTGGCGG492T.ACIDGGCAAGACGG GTGCCAGCCG CCGCGGTAAC ACCCGCAGCT CGAGTGGTGA486M.VANNGGCAAGTTCGGTGCCAGCAGCCGCGGTAAT ACCGACGGCCCGAGTGGTAG805MB.FORGGCAAGACCGACCGGCAGCTCAAGTGGTGGGTGCCAGCCGCCGCGGTAACMS.HUNGGCAAGACCGGTGCCAGCCGCCGCGGTAAT ACCGGCGGCTCGAGTGGTGG488M.SOEHGGCAAGACCG GTGCCAGCCG CCGCGGTAAC ACCGGCGGCT CGAGTGGTAA492H.VOLCGGCAAGACCG GTGCCAGCCG CCGCGGTAAT ACCGGCAGCT CAAGTGATGA机HC.MORGGCAAGACCG GTGCCAGCCG CCGCGGTAAT ACCGGCAGCT CGAGTGATAGH.HALOGGCAAGACCG GTGCCAGCCG CCGCGGTAAT ACCGGCAGTC CGAGTGATGGH.CUTIGGCAAGACCG GTGCCAGCCG CCGCGGTAAT ACCGGCAGTC CGAGTGATGGT.MTMAGGCTAACTACGTGCCAGCAG CCGCGGTAAT ACNTAGGGGG CAAGCGTTACBACTTM.ROSGGCTAACTACGTGCCAGCAG CCGCGGTAAG ACGTAGGGGG CGAGCGTTACCFX.AUGGCTAACTCT GTGCCAGCAG CCGCGGTAAGACAGAGGGGG CNAGCGTTGTAN.NIDGGCTAATTCC GTGCCAGCAG CCGCGGTAAT ACGGGAGAGGCAAGCGTTATBC.SUBGGCTAACTACGTGCCAGCAGCCGCGGTAAT ACGTAGGTGGCAAGCGTTTTE.COLIGGCTAACTCC GTGCCAGCAG CCGCGGTAAT ACGGAGGGTG CAAGCGTTAAAG.TUMGGCTAACTTC GTGCCAGCAG CCGCGGTAAT ACGAAGGGGG CTAGCGTTGT501Z.MCHLGGCTAACTCTGTGCCAGCAG CCGCGGTAAG ACAGAGGATG CAAGCGTTATCHLOROP

[0-7{0-10][0-559][0-837][0-180]V4[0-2][0-196524(0-146)V8[0-310]10-1571505[0-10][0-15][0-410.2[0-10]Reference sequenceand structure: Escherichie coli1J01695)t.celulerorgarNovembe2001[3:245] 5Numeerotsequences:73550-25V9Positons with a nuclectide in rrore than 95% of the soguences are[0,11] [0-179]shown in one ot feur categories.ACGU -98+%conservedacgu-90.9% conoerved - 80-90% conserved10-1-lossthan80%conservedOtherwise, the segions are represented by arcsDArclsbeisindicntetheurperandlowernumbercfmuciechcoskenownto axistwithin theassociabodvariableregion.10-411Blue tags indicate insertions relafive to the reference stquenteIserions tmat aopear are:(1) longih 1-4 in more than 10% ot soguences(2) orgth 5 or greater in at ieast one sequence10-560withformat:(Max.Length ofirserton:Poroentageof socswinary iongih ineertion)Citatonandreiatedintormationavailsbleathttp:/wwwrnaicmb.utexas.edu

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