MICROBIAL FLOC STABILIZATION AND PREPARATION FOR STRUCTURAL-ANALYSIS BY CORRELATIVE MICROSCOPY

In the analysis of microbial flocs from activated sludge it is importa nt to Stabilize these structures and their components for structural s tudies sufficiently to assess, minimize and conceptually balance artif acts, particularly during manipulation. By employing multi-technique s tabilization and immediate preservation it is possible to analyze a si ngle sample by correlative microscopy (conventional optical microscopy (COM), scanning confocal laser microscopy (SCLM), and transmission el ectron microscopy (TEM)). This approach minimizes variability associat ed with multiple sampling. Floc samples were collected using plankton chambers consisting of reservoirs with a removable circular microscope slide. Flocs which come to rest on the slide are stabilized within lo w melting point agarose. The solidified gel is a clear, highly porous and resilient medium amenable to further staining, washing, sub-sampli ng or direct microscopic analysis. Stabilization in agarose was found not to significantly influence flee size distribution. The use of agar ose was found to be compatible with SCLM and TEM techniques and minimi zed perturbations. Agar-embedded samples were easily infused with Nano plast, a hydrophilic melamine resin, which stabilizes material in its natural state. This facilitates the ultrastructural analysis of the th ree-dimensional fibrillar architecture of the flee matrix. The matrix is found to consist of complex pores bounded by fibrils of 4-6 nm diam eter. Copyright (C) 1996 IAWQ.