Abstract:
Eutrophication of freshwater bodies followed by cyanobacterial bloom and toxin production is an
important issue in freshwater supply in both developed and developing countries. The primary
mechanism for microcystins (MCs) (the main class of cyanobacterial toxins) dissipation is microbial
degradation. Repeated exposure of freshwater bodies to cyanobacterial toxins MCs may affect indigenous
microbial communities and may also enhance biodegradation of MCs, but the factors driving this
relationship remain unclear. Six Scottish freshwater bodies with different histories of natural exposure to
MCs and ability to degrade MC-LR (the most common microcystin) were chosen as case study. Terminal
Restriction Fragment Length Polymorphism (T-RFLP) and Biolog EcoPlate were used to study the
structure and physiology of the bacterial communities. Previous exposure to MCs significantly
contributed to the bacterial communities shape and microbial physiology of the water bodies under
study. Other factors that significantly affected the bacterial communities were dissolved organic carbon
and concentration of nitrogen compounds as well as temperature. Moreover a significant relationship
was found between bacterial communities’ structure and MC-LR half-life. These data suggest that
exposure to MCs drives changes in structure and physiology of bacterial communities and in turn those
communities differentially perform degradation of MC-LR.
