Day 3. Examine gels from PCR. Learn about more molecular methods in microbial ecology

Transcription

1 Day 3 Examine gels from PCR Learn about more molecular methods in microbial ecology

2 1: dsrab 1800bp 2: mcra 750bp 3: Bacteria 1450bp 4: Archaea 950bp 5: Archaea + 950bp 6: Negative control Genes We Targeted

3 1: dsrab 1800bp 2: mcra 750bp 3: Bacteria 1450bp 4: Archaea 950bp 5: Archaea + 950bp 6: Negative control ZC, Col1 R, Col2 HL, Col3 JP, Col4

4 1: dsrab 1800bp 2: mcra 750bp 3: Bacteria 1450bp 4: Archaea 950bp 5: Archaea + 950bp 6: Negative control ME, Col6 KS, Col8 SM, Col10 OB, Col11

5 1: dsrab 1800bp 2: mcra 750bp 3: Bacteria 1450bp 4: Archaea 950bp 5: Archaea + 950bp 6: Negative control HRG, Col12

6 Some Problems with PCR Inhibitors in template DNA Amplification bias Gene copy number Limited by primer design Differential denaturation efficiency Chimeric PCR products may form Contamination w/ non-target DNA Potentially low sensitivity and resolution General screw-ups

7 (Some) Problems with Molecular Methods D/RNA extraction Storage PCR Anytime Incomplete sampling Resistance to cell lysis Enzymatic degradation Inhibitors in template DNA Amplification bias Gene copy number Fidelity of PCR Differential denaturation efficiency Chimeric PCR products Contamination w/ non-target DNA

8 So you have a positive PCR product: Now what? Get community fingerprint via T-RFLP, DGGE, etc. Clone and sequence Quantify it Go straight into sequencing (next generation sequencing)

9 Microbial community Community sampling approach Amplify single gene, for example, gene encoding 16S rrna Sequence and generate tree Extract total community DNA DNA Environmental genomics approach Restriction digest total DNA and then shotgun sequence, OR sequence directly (without cloning) using a high throughput DNA sequencer Assembly and annotation Outcomes Partial genomes Single-gene phylogenetic tree 1. Phylogenetic snapshot of most members of the community 2. Identification of novel phylotypes Total gene pool of the community 1. Identification of all gene categories 2. Discovery of new genes 3. Linking of genes to phylotypes 2012 Pearson Education, Inc.

10 B. Crump

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12 What do you DO with sequences? Perform a similarity search Align the sequences Build a tree and classify Reconstruct genomes Categorize functions Compare organisms/samples Design probes and quantify Examine expression patterns Etc. Etc. Etc.

13 BLAST Basic Local Alignment Search Tool

14 Making Sense of Sequences: Molecular Phylogeny 1. Align sequences so that homologous residues are juxtaposed. 2. Count the number of differences between pairs of sequences; this is some measure of evolutionary distance that separates the organisms. 3. Calculate the tree, the relatedness map, that most accurately represents all the pairwise differences.

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17 Quantitative PCR

18 Found similar novel dsr sequences in the sulfate-rich and methane-rich zones Different (and already known) dsr sequences in SMTZ

19 Quantitative PCR

20 Quantitative (Real Time) PCR Real time PCR monitors the fluorescence emitted during the reactions as an indicator of amplicon production at each PCR cycle (in real time) as opposed to the endpoint detection

21 Quantitative (Real Time) PCR Detection of amplification-associated fluorescence at each cycle during PCR No gel-based analysis Computer-based analysis Compare to internal standards Must insure specific binding of probes/dye

22 Quantitative PCR Used qpcr to quantify total bacteria (16S rrna) and total sulfate reducers (dsr)

23 Quantitative PCR Sulfate reducing bacteria (dsr gene) peaks at SMTZ

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25 Moving from who is there to who is active DNA RNA Proteins

26 Reverse Transcription PCR (RT-PCR) Looks at what genes are being expressed in the environment Isolate mrna Reverse transcribe mrna to produce complementary DNA (cdna) Amplify cdna by PCR Analyze genes from environment

27 RT-PCR RNA + Reverse Transcriptase + dntps= cdna cdna + Primers + Taq + dntps = gene of interest Who is active? What genes are active?

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30 qrt-pcr Gene copy and transcript numbers are greatest at the estuary head (Hythe), where the rates of denitrification/dnra are highest.

31 All require a priori knowledge to design primers or probes Community sampling approach Amplify single gene, for example, gene encoding 16S rrna Sequence and generate tree Extract total community DNA DNA Microbial community Environmental genomics approach Restriction digest total DNA and then shotgun sequence, OR sequence directly (without cloning) using a high throughput DNA sequencer Assembly and annotation Outcomes Partial genomes Single-gene phylogenetic tree 1. Phylogenetic snapshot of most members of the community 2. Identification of novel phylotypes Total gene pool of the community 1. Identification of all gene categories 2. Discovery of new genes 3. Linking of genes to phylotypes 2012 Pearson Education, Inc.

32 Sequencing Revolution

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35 Traditional 16S rrna Cloning Schematic courtesy of B. Crump

36 NextGen Approaches Schematic courtesy of B. Crump

37 What is the difference between standard and next-gen sequencing?

38 Metagenomics Clone (BAC, Fosmid or Small Insert) or Directly Sequence (Illumina) Total Environmental DNA

39 Metagenomics Clone (BAC, Fosmid or Small Insert) or Directly Sequence (Illumina) Total Environmental DNA

40 Metagenomics Clone (BAC, Fosmid or Small Insert) or Directly Sequence (Illumina) Total Environmental DNA Access genomes of uncultured microbes: Functional Potential Metabolic Pathways Horizontal Gene Transfer

41 2012 Pearson Education, Inc. Reconstruct Genomes

42 2012 Pearson Education, Inc. Categorize Functions

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44 Metagenomics Clone (BAC, Fosmid or Small Insert) or Directly Sequence (Illumina) Total Environmental DNA 16s rrna gene Gammaproteobacteria SAR86 Proteorhodopsin gene

45 Proteorhodopsin gene

46 A new way of using sunlight in the surface ocean DeLong EF, Béjà O (2010) The Light-Driven Proton Pump Proteorhodopsin Enhances Bacterial Survival during Tough Times. PLoS Biol 8(4): e doi: /journal.pbio

47 Proteorhodopsins occur in 13%-80% of marine bacteria and archaea in oceanic surface waters Venter et al. 2004

48 Moving from who is there to who is active DNA RNA Proteins

49 Metatranscriptomics Clone (BAC, Fosmid or Small Insert) or Directly Sequence (Illumina) Total Environmental DNA Access expressed genes of uncultured microbes Looking at expression of defined genes via PCR GeoChip-type analyses with RNA Etc.

50 Stable Isotope Probing (SIP) Links specific metabolic activity to diversity using a stable isotope Microorganisms metabolizing stable isotope (e.g., 13 C) incorporate it into their DNA/RNA/Lipids Characterization of DNA/RNA/Lipids with 13 C can then be used to identify the organisms that metabolized the 13 C

51 RNA SIP Lueders et al. 2016

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53 Who are the active autotrophs of the subseafloor? What metabolic pathways are they using across geochemical gradients? How do viruses impact the subseafloor community? How does this new production influence deep carbon cycling?

54 Diverse Metabolisms

55 Venting fluids as window into subseafloor biosphere

56 RNA-SIP Vent Fluid

57 RNA Concentration (ng/ul) RNA-SIP 2.5 RNA Precipitation C C Buoyant Density

58 RNA Concentration (ng/ul) Uptake of Bicarbonate L 13H Active autotrophs 1 12C-30 13C L 12H Buoyant Density

59 30 C, 36 hr Marker 113 Vent Active autotrophs 55 C, 36 hr Active autotrophs 80 C, 18 hr Active autotrophs Fortunato & Huber, ISME J 2016

60 Fortunato & Huber, ISME J 2016 mrna Taxonomy Caminibacter Sulfurimonas Methanocaldococcus Nautilia Methanothermococcus

61 Carbon Fixation Pathways Fortunato & Huber, ISME J 2016

62 Energy Fortunato & Huber, ISME J 2016

63 Not all Vents are the Same! Vent Characteristic: Anemone Marker 33 Marker 113 Temperature, C Hydrogen sulfide, mmol L Ammonia, µmol L ph Hydrogen, µmol kg < 1.0 Methane, µmol kg Oxygen, µmol L

64 mrna: 13 C, 80 C Aquifex Desulfurobacterium Sulfur, nitrate reduction Hydrogen oxidation Methanogenesis Carbon fixation Methanocaldococcus Thermovibrio Methanocaldococcus Anemone Mkr 33 Mkr 113 Fortunato et al, Unpub

65 mrna: 13 C, 80 C Aquifex Desulfurobacterium Sulfur, nitrate reduction Hydrogen oxidation Methanogenesis Carbon fixation Methanocaldococcus Thermovibrio Methanocaldococcus Anemone Mkr 33 Mkr 113 Fortunato et al, Unpub

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67 And the list goes on Optical tweezers Single cell genomics Meta-proteomics Microarrays Flow Cytometry Nano-SIMS FISH In-situ PCR and FISH