engleski

Northern Adriatic mesocosm experiment Rovinj 2003: changes in bacterial community by fatty acid profiling

We applied fatty acid analysis to characterise changes within culturable bacterial community structure and relative frequencies of the branched fatty acid bacteria (BrFA) among the colony-forming units (CFU). These results are expected to provide an insight into changes within organic matter quality during course of the bloom. Two different enrichment regimes, P-deficient and nutrient-balanced, were investigated. Bacteria were cultured in liquid (Marine broth) and solid (Marine agar) media. The particulate matter was separated by filtration on GF/F and PC filters. The fatty acids were analysed by capilary GC/MSD. Among colony-forming units, three types of Proteobacteria and variety of species related to Cytophaga group were identified. During experiment the overall greatest contribution of Proteobacteria was found. Increases in culturability and disproportion between culturability and CTC-activity were particularly expressed in the nutrient-balanced mesocosm. BrFA bacteria dynamics (Cytophaga-related species) were similar in all mesocosms until 17th day. After this date the BrFA contribution remained constant in the P-deficient, but increased in the nutrient-balanced mesocosm. The cultured bacterial community dynamics observed by fatty acid profiling were similar in both nutrient balanced and P-deficient conditions, as well as in the control mesocosm. Continuous increase in disproportion between culturability and CTC-activity toward the end of experiment as well as dynamics of Cytophaga-related species imply the accumulation of unutilised organic matter and increase in proportion of refractory organic compounds in nutrient-balanced mesocosms. The characteristics of particulate matter from the nutrient balanced mesocosm were similar to that found in dense and compact mucilaginous aggregates.

fatty acid composition; bacterial community; particle matter; CFU; CTC activity

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