Obstacles to flow cytometric analysis of rumen microbial samples.

Several methods were tested that would improve the fluorescence signal from hybridized rumen bacterial cells. Disruption of cell envelopes by lysozyme, EDTA, proteinase K and/or SDS caused only a minor increase in fluorescence signal. Use of helper unlabeled oligonucleotide probes was successful only with the Puni[H672] probe which, however, when used with specific PBBl4-labeled probe, gave fluorescence signal drop. No substantial rise in fluorescence signal was also observed with cells subjected to growth-without-cell-division treatment. Further improvements are needed to make the fluorescent in situ hybridization (FISH)-flow cytometry combination applicable to rumen bacteria.