Tag Archives: 08:3-15

qPCR – Black Abalone with XC Prophage Portal Primers

Ran qPCR with black abalone samples from the 1st and 2nd experiments to see if the Xenocal prophage portal gene is detected.

Master mix calcs (Google Sheet): 20160421 – qPCR Black Abs XenoCal phage portal

All samples were run in duplicate.

Black abalone sample 08:13-2 was run as a positive control.

Plate layout, cycling params, etc. can be seen in the qPCR Report (see Results below).

Results:
qPCR Report (PDF): Sam_2016-04-21 14-11-09_CC009827.pdf
qPCR Data File (CFX): Sam_2016-04-21 14-11-09_CC009827.pcrd

Two samples failed to produce amplification: 06:6-44 and 07:12-18. All other samples amplified. Will compile this data with WSN and RLOv DNA helicase and send along to Carolyn and Stan.

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Data Aggregation – WS RLO and RLOv DNA Helicase qPCR and WS RLO Infection Intensities

Carolyn asked me to send her the data described above.

RLOv DNA helicase qPCR data were grabbed from the qPCR I ran on 20160106.

The qPCR data for withering syndrome RLO were culled from these three different spreadsheets:

 

The summary is below. I have emailed a copy of the spreadsheet to Carolyn.

Google Sheet: 20160404_Summary_RLO_RLOvDNAhelicase_qPCR_HistoIntensities

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qPCR – Repeat Phage Portal Primer Specificity Check

This should be the last time I run this for the time being. Re-running this with undiluted RLOv- samples to improve the melt curve resolution for better comparison to the RLOv+ melt curves.

See the earlier qPCR run for master mix calcs.

All samples were run in duplicate.

See the qPCR Report (see Results below) for plate layout, cycling params, etc.

Results:

qPCR Report (PDF): Sam_2016-03-17 13-30-29_CC009827.pdf
qPCR Data File (CFX): Sam_2016-03-17 13-30-29_CC009827.pcrd

These results are interesting and I believe they are real, as opposed to the confusing/conflicting information I got from the previous two qPCRs from earlier today with the phage portal gene primers.

The poor/confusing results from the two previous qPCR attempts seem to have stemmed from low sample concentration. Using undiluted RLOv- samples in this run has resulted in clear, definitive data.

The melt curves are of a single peak in all RLOv+ samples.

The phage portal gene is NOT detected in RLOv- samples. However, it is present in RLOv+ samples and at significantly lower abundance than the RLOv DNA helicase (DNA helicase comes up at ~23 Cqs in samples that have been diluted 1:1000, while the phage portal gene comes up at ~28 Cqs in UNDILUTED samples). Alternatively, it is possible that the phage portal qPCR is less efficient and/or is experiencing some sort of inhibition; both seem unlikely, though.

Will discuss with Carolyn to see if she wants to go forward with cloning/sequencing and construction of a plasmid standard curve for the phage portal gene.


qPCR Amplification Plots (DNA helicase in green; Phage portal gene in blue)

 


 

qPCR Amplification Plots of Phage Portal Gene

 

qPCR Melt Curves of Phage Portal Gene

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qPCR – Repeat Phage Portal Primer Specificity Check

Due to the odd (and poor) results from the first qPCR to look at this phage portal gene, I’m repeating the qPCR exactly, but have made fresh 1:1000 dilutions of the two RLOv+ samples (08:3-15, 08:3-16) with TE.

See the earlier qPCR run for master mix calcs.

All samples were run in duplicate.

See the qPCR Report (see Results below) for plate layout, cycling params, etc.

Results:

qPCR Report (PDF): Sam_2016-03-17 10-42-54_CC009827.pdf
qPCR Data File (CFX): Sam_2016-03-17 10-42-54_CC009827.pcrd

Firstly, the fresh dilutions resolved the issue with the poor amplification previously seen with the RLOv DNA helicase assay; they look perfect in this run.

Quick summary for the phage portal qPCR:

  • Amplification in all 4 samples (RLOv- & RLOv+).
  • Much, much earlier amplification in RLOv+ samples.
  • Good, single peaks in melt curves
  • RLOv+ and RLOv- samples show different temps for peaks in melt curves

If the phage portal gene was present in the RLOv, then we would expect the amplification (i.e. the Cq values) of DNA helicase and the phage portal gene to be extremely close. However, in the RLOv+ samples, there’s a ~1000-fold difference in DNA helicase/phage portal levels.

If the phage portal gene was present in just the RLO, then we would expect similar amplification (i.e. Cq values) in both RLOv+/- samples. However, we see an EXTREME difference in phage portal gene levels between RLOv+ samples and the RLO- samples (~10,000-fold difference in levels). If the phage portal gene was present in both RLOv+/- samples, then that could possibly help explain this difference, due to the massive phage load in the RLOv+ samples (based on DNA helicase data). However, this doesn’t seem to be the case…

We see two distinct melt curve peak temps between the RLOv+/- samples. If the phage portal gene was present in both sample types, then the RLOv+ samples should exhibit a dual peak in the melt curves. However, this is not the case. This is difficult to explain since the RLOv+ samples also contain RLOv- (i.e. the RLO bacteria) DNA. If the PCR product generated in the RLOv- samples is indeed distinct from that produced in the RLOv+ samples, then we should see that product in the melt curve of the RLOv+ samples, but we don’t.

I will repeat this qPCR using undiluted, source DNA from the RLOv- samples. This should shift their amplification ~10 Cq (a 10-fold difference in amplification equates to ~3.32 Cqs) earlier. This, in turn, will allow their signal to generate higher levels of fluorescence and, hopefully, increase the melt curve peak for a more accurate assessment of melt temp(s); just to make sure the melt temp is accurate.


 

qPCR Amplification Plots (DNA helicase in green; Phage portal gene in blue)


qPCR Amplification Plots of Phage Portal Gene

qPCR Melt Curves of Phage Portal Gene

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qPCR – Phage Portal Primer Specificity Check

Stan Langevin recently identified a RLOv phage portal protein sequence that he wanted to see if this gene is incorporated in the withering syndrome bacteria (RLO) or the phage (RLOv). He designed a primer and probe set:

I’ve ordered/received the primers and need to test them out verify their specificity (via melt curve analysis) to ensure they only amplify a single target before proceeding with the expense of ordering a probe, as well as the time/effort that will be needed to, potentially, create a plasmid standard curve.

Set up qPCR on the following samples using the new RLOv phage portal primer set, as well as the RLOv DNA helicase qPCR assay to serve a positive control. These samples have been previously qPCR’d with the RLOv DNA helicase assay to establish the presence/quantities of RLOv in these samples. Samples are 1:1000 dilutions of the source DNA (made 20160106, but made fresh dilutions of RLOv negative samples today in H2O) due to the extremely high levels of RLOv detected in the RLOv positive samples.

SAMPLE RLOv +/-
08:4-3 NEGATIVE
08:4-4 NEGATIVE
08:4-15 POSITIVE
08:4-16 POSITIVE

 

RLOv phage portal master mix calcs (Google Sheet): 20160317 – qPCR XenoCal phage portal specificity

RLOv DNA Helicase master mix calcs (Google Sheet): 20160317 – qPCR RLOv

All samples were run in duplicate. Plate layout, cycling params, etc. are in the qPCR Report (see Results below).

Results:

qPCR Report (PDF): Sam_2016-03-17 08-03-13_CC009827.pdf
qPCR Data File (CFX): Sam_2016-03-17 08-03-13_CC009827.pcrd

The results are very odd and the qPCR should be repeated with fresh dilutions of the source DNA. Here are the reasons:

  • Almost no amplification with DNA helicase in RLOv+ samples
  • Amplification in all but one sample with phage portal – expected in all, none, RLOv- only, or RLOv+ only
  • Phage portal melt curves differ across samples – even within same sample type (i.e. RLOv-
  • Multiple peaks in phage portal melt curve in one RLOv- sample
  • Single peak in phage portal melt curve in the RLOv+ sample

See the amplification plots and melt curves below for a better idea of what’s happening.

 


qPCR Amplification Plots (DNA helicase in green; Phage portal gene in magenta)


 

 

qPCR Amplification Plots of Phage Portal Gene

 

qPCR Melt Curves of Phage Portal Gene

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