Is there a way to isolate bacteria and viruses without a centrifuge?

Question

Is there a way to isolate bacteria and phages from soil samples if you do not have access to a centrifuge? The purpose for which we need to isolate bacteria is for basic phage hunting.

Answer 1

In the seaphages discovery guide the protocol for direct isolation states:

Allow the sample to sit until particulate matter has mostly settled. This may take as few as 2 minutes or as many as 20 minutes. Alternatively, you can centrifuge these samples to hasten this process. To do this, balance the tubes and centrifuge at 2,000 x g for 10 minutes to pellet (i.e., force to the bottom of the tube) most of the soil.

So filtration is really doing most of the job in separating the phage from the bacteria. Centrifugation mostly just speeds up the process.

Answer 2

Filtration is the correct answer - the very first viruses were identified as being filtratable (using the technology at the time) agents that could pass through the filters when bacteria couldn't.

Basically for phage isolation from a mostly water sample you just need to get rid of the sediment and ideally any bacteria that might be there too. Sedimentation (i.e letting it sit, centrifuge to speed up, as in Johan Wikstrom's answer) works well, but the best non-centrifuge method is to let large particulate matter settle, then start with filter papers of different grades to remove particulate matter, fine sediments and then work up to 0.45 micrometre filters to remove bacteria.

Of course you also need suitable plates and liquid media with a suitable host bacterium. E. coli works well for many bacteriophages in the Lambda group, but many other species of bacteria have bacteriophages of their own.