Plastic microbeads are very much in the news right now – and as if the other environmental damage they cause isn’t enough, new research has shown potentially lethal bacteria are living on them and hitching a ride into the North Sea.
Summer heatwaves could result in the strong proliferation of pathogenic bacteria in North and Baltic Seas. In recent years, this also included bacteria of the genus Vibrio which can cause diarrhoeal diseases or severe inflammations. “Vibrios are climate change winners, because their numbers soar at higher temperatures,” Dr. Gunnar Gerdts, microbiologist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) on Heligoland explains.
In moderate summers, the bacteria are only sporadically evident in sea water, but can proliferate explosively during heat waves if water temperatures rise above 22°C. Especially in nearshore areas of the Baltic Sea, such heatwaves have in the past repeatedly been associated with cases of disease or death caused by the bacterium Vibrio vulnificus, a cousin of the bug that causes cholera.
Gerdts and his team have taken samples from the sea and examined whether the bacteria benefit from a new habitat known as the plastisphere. Bacteria, fungi and microalgae growing in a mucous layer live in biofilms on the surface of plastic particles. They are known, for example, as the basis for growth on ships’ hulls. The composition of these biofilms varies depending on the condition of the surface and the living organisms in the surrounding water. Gene sequencing suggested that vibrios may also be part of this ecosystem.
For the first time now, the Heligoland microbiologists have succeeded in proving the existence of living, potentially human-pathogenic Vibrio species in biofilms on microplastic particles. “This illustrates the potential of pathogens hitchhiking on these particles, i.e. disseminating as free loaders within an ecosystem and proliferating beyond,” Gunnar Gerdts classifies the latest research findings.