Viewing Bacteria With Bright-field Microscopy

[MicroscopyLearning]

Ok. I see what you mean now, but doesn't a starter culture sometimes contain yeast sometimes though?

Yeast doesn't produce yogurt.

From what I have read some yoghurts do contain yeast, but I am not sure if the starter culture contains it. What do you think? Also, about how high should the resolution of the usual 40 times objective be, mine appears to be rather blurry, more so than Microbehunter's objective shows in his videos. This might be due to contamination, but even the first time it was used, it was still rather blurry. The objective is a dry 40 times objective from the SW350T-AK-PK microscope model. Do you think the rather blurred image is due to the quality of the objective?

[Alexander]

This is hard to tell. Despite the fact your objective is not exactly high-end it should give a reasonable image. With a 40x you should see bacteria colonies. Please describe your problem with blurriness in more detail.

[Alexander]

Just a quick and dirty picture of what you could expect. The picture shows some Cocci with gram-staining.

Bacteria.jpg (134.07 KiB) Viewed 2512 times

[MichaelG.]

.

That provides an excellent ‘reality check’ Alexander

… Thanks for sharing it.

MichaelG.

[MicroscopyLearning]

Just a quick and dirty picture of what you could expect. The picture shows some Cocci with gram-staining.
Bacteria.jpg

Do you have any recommendations on what to view with a phase contrast microscope, while I would like to be able to view bacteria with bright-field, I am also fine with doing it with phase contrast. I have tried looking at yoghurt in phase contrast, but it was not yoghurt I had made, so I feel the bacteria quantity was probably less than it could have been, even though it was a kind that the manufacturer inoculated with bacteria. I am not sure at what part of the yoghurt they would have done this, so I am not sure if the sample was exactly homogeneous. Do you have any recommendations for samples to view?

[Alexander]

Just a quick and dirty picture of what you could expect. The picture shows some Cocci with gram-staining.
Bacteria.jpg

Do you have any recommendations on what to view with a phase contrast microscope,

...

Do you have any recommendations for samples to view?

Phase contrast is of limited help to view bacteria. This has been explained to you before.

An easy example specimen is the following:

Put some large thick slices of carrot into boiling water for two minutes. Then put them into petri dishes and fill some water in. Within a few days a dense colony of bacteria will populate the slices. Just touch the surface of one slice with a slide. Here is your sample. Let it dry in air. Then fix it by heat. Then stain it with methylene blue. Here you are.

[Alexander]

Do you have any recommendations on what to view with a phase contrast microscope,

...

Do you have any recommendations for samples to view?

Phase contrast is of limited help to view bacteria. This has been explained to you before.

An easy example specimen is the following:

Put some large thick slices of carrot into boiling water for two minutes. Then put them into petri dishes and fill some water in. Within a few days a dense colony of bacteria will populate the slices. Just touch the surface of one slice with a slide. Here is your sample. Let it dry in air. Then fix it by heat. Then stain it with methylene blue. Here you are.

The picture I posted came from the white film on the liquid in a forgotten can of olives in the fridge.

[DonSchaeffer]

Look for biofilm. That's where you find bacteria. You find bits of it floating on the surface of stagnant water. When you lift it with a tweezer it is mucous-like.

[MicroscopyLearning]

Do you have any recommendations on what to view with a phase contrast microscope,

...

Do you have any recommendations for samples to view?

Phase contrast is of limited help to view bacteria. This has been explained to you before.

An easy example specimen is the following:

Put some large thick slices of carrot into boiling water for two minutes. Then put them into petri dishes and fill some water in. Within a few days a dense colony of bacteria will populate the slices. Just touch the surface of one slice with a slide. Here is your sample. Let it dry in air. Then fix it by heat. Then stain it with methylene blue. Here you are.

The picture I posted came from the white film on the liquid in a forgotten can of olives in the fridge.

Thank you for the recommendation. Can they be viewed decently at 40 times as well as 100 or would you say that 100 times is ideal? Also, did you use a dry objective or an oil objective for the photo you took.

[DonSchaeffer]

That could be mold spores in the olive can.

[Alexander]

Can they be viewed decently at 40 times as well as 100 or would you say that 100 times is ideal? Also, did you use a dry objective or an oil objective for the photo you took.

You will see stained bacteria clearly with the 40x. With a 100x they appear bigger but the depth of field is less. Always a trade-off.

I used an oil immersion 40x. A dry one would have done the job as well.