Reduced growth-factor requirement of keloid-derived fibroblasts may account for tumor growth (

Mixed-species microbial mats that were dominated by the cyanobacterium Oscillatoria sp. and contained heterotrophic and purple autotrophic bacteria were constructed for specific bioremediation applications. When the mats were challenged with metals, production and secretion of metal-binding extracellular polysaccharide bioflocculants were observed. The concentration of these negatively charged polysaccharides was correlated with the removal of manganese from the water column beneath a surface microbial mat. Bioflocculants from an Oscillatoria sp. that was isolated from the mat were collected and concentrated for characterization. A chromatographic analysis revealed a heterogeneous population of polysaccharides with respect to charge density and molecular size. The subpopulation of polysaccharides which exhibited the highest level of flocculating activity was polyanionic and had a molecular weight of more than 200,000. A glycosyl analysis of the bioflocculants revealed the presence of galacturonic acid (2.2%) and glucuronic acid (1.86%). The presence of these components, which were negatively charged at the pH levels generated by the mats during photosynthesis (pH > 7.5), may account for the metal-binding properties of the mats.

At the Tennessee Valley Authority's Fabius Coal Mine, Alabama, manganese was more effectively removed from a pond containing an algae mat consortium and limestone substrate than from ponds containing only limestone or pea gravel substrates. The algae mat resulted from the integration of a microbial mat and volunteer filamentous green algae. The microbial mat consisted of blue-green algae (predominately Oscillatoria spp.) and bacteria isolated from the site, cultured in the laboratmy, and returned to the site. System operation ran from August 1992 through March 1993. Manganese and iron were consistently removed more efficiently in the algae mat pond (mean flow of 4.2 L/min) than through gravel-only ponds even as water temperatures dropped to less than 5° C in the winter.. Based on filtered water samples, during winter months, at 2 m from the influent point of each pond, the algae mat pond removed 2.59 g/d/m' manganese, compared with 0.80 in the limestone pond and 0.37 in the pea gravel pond. At 1 m from the influent pipe in the algae mat pond, 2.67 mg manganese and 34.25 mg iron were deposited in a gram of dried mat. In March 1993 two events likely caused the loss of much of the algae mat: (1) a 50-cm snowfall followed by a heavy runoff and (2) establishment of a snail population, as well as other possible invertebrate herbivores, which consumed the algae mat. The algae mat was reestablished in June 1993 and has persisted to date. A green algae and microbial mat consortium may be a cost-effective treatment technique for permanently removing metals from mine drainage.

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