MicrobeHunter.com Microscopy Forum

Ciliates have a transcriptionally quiescent germline micronucleus and a transcriptionally active macronucleus responsible for the day to day functioning of the organism. The macronucleus is composed of tens of thousands gene-sized chromosomes and this presents the unique problem of how to replicate them in a timely manner for the next cell division event. In Spirotrich ciliates such as Oxytricha and Euplotes a unique solution has been evolved. A vectorial system coordinates DNA synthesis in time and space in a so called replication band. Two disc-shaped replication bands fire at the polar ends of an elongated macronucleus and they migrate towards the midpoint of the macronucleus where replication terminates. The replication band is divided into a frontal zone, characterized by protein phosphorylation, a rear zone, characterized by protein acetylation and the site of the DNA synthesis in the middle.



Technical details:
Zeiss Phomi III
Planapo 40/0,95
Canon 50D (RAW)
12V 100W tungsten halogen lamp
450/40 excitation filter, 510 dichroic mirror, 540/80 emission filter

Sample preparation.
Cultured pond sample was mixed with methylcellulose (1 % final concentration) and 50 micrograms/ml acridine orange (much higher concentration than actually required). Sample was incubated for 40 minutes at room temperature before imaging.

Best regards,
Wes

Hi Wes,
great observation and photo! For me it is interesting that such a life process can be shown with the light microscope.

Bob

Cool photo, how long does the process last? You just look around the sample until you find one that happens to be in the middle of it?

Thank you Bob and Hans!

MicroBob wrote: ↑

Sun Jul 11, 2021 7:11 pm

For me it is interesting that such a life process can be shown with the light microscope.

I have also always been interested in the opportunity to observe things like cell division and the appearance of structure as a result of replication, transcription and such. Here for example you can notice coarse granules composed of chromatin/RNA in the replicated DNA and their finer counterparts in the unreplicated part.

hans wrote: ↑

Sun Jul 11, 2021 8:27 pm

how long does the process last? You just look around the sample until you find one that happens to be in the middle of it?

No idea, but most likely on the order of a few hours. To get a better chance of finding such events you want a happy well fed population. Otherwise you will observe programmed nuclear death which is similarly fascinating.

Interesting project and a great final image. You are getting a lot out of that microscope!

75RR wrote: ↑

Mon Jul 12, 2021 12:50 pm

Interesting project and a great final image. You are getting a lot out of that microscope!

Thanks 75', finding an interesting specimen without getting too much spherical aberration is most of the work anyway. I only noticed these replication bands after reading the article linked below, I went back to some much older photos and I realized I've shot them in the past but never realized it till now.

https://www.sciencedirect.com/science/a ... 2220314470