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Blanca Perez-Uz, Elena Alonso Fernandes and Mercedes Martin-Cereceda
Universidad Complutense de Madrid, Spain
Posters & Accepted Abstracts: J Microbio and Biotech Rept
Statement of the Problem: The increase of bacterial populations in natural environments in response to impacts caused by human activities is also associated with the increase of bacterial predators such as ciliates. These protists are able to eliminate bacteria, as part of their activities in the microbial loop, channeling this matter and energy to other links in the food web. Therefore, the bacterial production could be potentially eliminated through the activities of other microbial components of the ecosystem. We worked during a year assessing the environmental impact of visitor activities through the study of Fecal Indicator Bacteria (FIB) in three points of the main river crossing a National Park. During this time, we isolated bacterivorous ciliates and bacteria, both coliform and enterococci from some of the samples and developed experiments to assess the capability of ciliates predatory activities on these bacteria. Methodology & Theoretical Orientation: Ciliates (Cyclidium sp. and Colpidium colpoda) were isolated from samples retrieved to enumerate FIB. These ciliates were kept in cultures with bacterial suspensions promoted with wheat grass. FIB bacteria isolated were fecal Enterococci (EC), selected on Slanetz-Bartley and Bile Sculin Agars and fecal coliforms Enterobacteria (EB) on EMB, Chromocult and EC. Short term experiments with Fluorescently Labeled Enterococci (FLE) and Coliforms (FLC) were used to evaluate the capacity of ciliates to capture them at concentrations between105-106 bacteria ml-1. Long term experiments were carried out to assess the ability of ciliates to grow in the presence of both bacteria. This would be an indication that those bacteria could be used as a food source and therefore eliminated effectively. Findings: Both ciliates Cyclidium sp. and Colpidium colpoda were able to ingest the EC and the EB, but they only grew on EB. Cyclidium ingestion was much less effective than Colpidium colpoda and had as well a preference to ingest EC over the EB. Colpidium colpoda had the opposite preference, ingesting more EB (9 times more than Cyclidium) than EC and these were more than twice those ingested by Cyclidium. Conclusion & Significance: These results show that capture of preys by ciliates did not predicted their capability to eliminate them from the environment. Growth experiments would be important to confirm their possible use in the elimination of FIB.
Blanca Perez-Uz has her expertise in microbial ecology and the use of microbial bioindicators both prokaryotic and eukaryotic in different natural and artificial environments. Her main interest has been the adaptations and effects of predatory activities of protist on bacterial populations and the possibility to use these activities to test the effects on wastewater treatment plants and natural environmental setups.
E-mail: perezuz@bio.ucm.com
