Hitching a ride? Deadly bacteria cling on to discarded plastic

When one man’s trash is another’s treasure: new study finds discarded plastic bags and bottles can become a floating home for deadly species of bacteria.

25th July 2016
Hitching a ride? Deadly bacteria cling on to discarded plastic © Alfred-Wegener-Institut

Deployment of catamaran taking samples © Alfred-Wegener-Institut

Is our disposable lifestyle catching up on us? While in the past, human migration has been responsible for the spread of infectious disease, the plastic we now carelessly throw away may also be allowing bacteria to hitchhike and disseminate across the North and Baltic Seas.

Much of the plastic chucked away as rubbish finds its way into our seas, where it is shredded into tiny fragments by UV radiation and the sheer force of waves bashing into it. When these pieces are smaller than 5mm they are defined as microplastic, which is estimated make up 92 per cent of the 268,000 tonnes of plastic floating near the sea’s surface, creating a massive soup of discarded junk.

Research published in Marine Environmental Research finds that the Vibrio species of bacteria, which can potentially cause diarrhoea and severe inflammation, survives on these microplastic particles as part of a biofilm.

A team of microbiologists from Alfred Wegener Institute in Germany took samples from 62 stations in the North and Baltic Seas, using a catamaran to skim off microplastic particles from below the water’s surface. Out of the 185 particles collected, they found evidence of Vibrio bacteria on 19 of them.

“This illustrates the potential of pathogens hitchhiking on these particles, i.e. disseminating as free loaders within an ecosystem and proliferating beyond," says corresponding author Gunnar Gerdts, of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research on Heligoland.

Several Vibrio species are evident in this sample © Alfred-Wegener-Institut / Antje Wichels
Several Vibrio species are evident in this sample © Alfred-Wegener-Institut / Antje Wichels

Future summer heat waves could worsen the proliferation of Vibrio clinging on to our plastic trash. If temperatures rise above 22 degrees Celsius they can reproduce rapidly, causing a population explosion. Worryingly, previous long hot summers have been associated with nearshore deaths caused by Vibrio vulnificus, although thankfully all species of Vibrio identified by this project were not pathogenic strains.

However, if the trends of rising temperatures and plastic disposal continue it may not be plain sailing, Gerdts argues: “It would be a cause for concern if microplastic particles 'charged' with Vibrios became a regular occurrence in the future, as biofilms generally have a higher bacterial density than open water."

Humans are not the only species affected by the accumulating microplastic, and the debate about how best to tackle this problem is on-going, but if you find yourself reaching for a shiny new bottle of spring water every morning before work, you may want to reconsider what you do when you’ve finished with it.

 


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