Let me give you an alternative to expensive laser equipment for isolating
single species from mixtures. This will not pick up a single bacterial
cell but it can enrich for a single species or bacterial type. There is a
relatively new methodology that many of us have used called immunomagnetic
enrichment. This process uses latex particles filled with iron. The outside
of the particle can be coated with just about anything you like, i.e.
specific or monoclonal antibody, antigens, DNA fragments. The beads are
added to whatever mixture you like and gently mixed, the specific reaction
occurs between the antibody-antigen on the particle, then a simple magnet is
applied to the side of the tube drawing the magnetized particle with its
reactant attached to it. The solution can be decanted, the beads washed as
necessary using only the magnet to hold the beads in the reaction test tube.
At this point, one can do anything from probing, PCR, gram staining, direct
culturing, etc. We have used this to remove specific bacteria from human
specimens. Several publications regarding the use of this method
are available by Olsvik, et al. The magnetic beads are commercially
available here in the U.S.
