Bacterial communities on chopping boards

Last week we met up with our group of citizen scientists to discuss the results of their chopping board experiment.

The experiment saw the group splitting into two teams. One team selected wooden chopping boards, the other plastic ones. Each household unpacked their new board and washed it according to their own habits. Each household also kept a record of the different foodstuffs they chopped on their board each day.

Each chopping board was swabbed six times over a period of 14 days. The swabs were prepared and analysed using 16S sequencing to identify the types of bacteria found on them at each time interval. 

The graph below is a similarity plot. The red points are from plastic boards, and the blue points from wooden ones. Each point on the graph is a community of bacteria on a chopping board. How close two points are to each other reflects how similar their bacterial communities are. You don't need to try and understand the axes - just think of them like the grid squares on a road atlas.

Similarity Plot for bacterial communities on chopping boards. Red dots = plastic boards; Blue dots = wooden boards.

Similarity Plot for bacterial communities on chopping boards. Red dots = plastic boards; Blue dots = wooden boards.

As you can see, the bacterial communities we found don't seem to be that different based on the type of board. We were a bit surprised by this, as we thought we might see different types of bacterial community preferring different surfaces. Perhaps we would need to keep swabbing the boards over a longer period for this to occur? Or perhaps the frequent washing and seeding of the boards with different foodstuffs stopped identifiable patterns emerging? There was no clear signal emerging from the type of foodstuff being chopped on each board, but this may have been due to the general diversity in foodstuffs being prepared across all the boards.

Similarity plots for all chopping boards, sampled 6 times over 14 days. Red dots = swabs from day 14. Grey dots = swabs from previous days.

Similarity plots for all chopping boards, sampled 6 times over 14 days. Red dots = swabs from day 14. Grey dots = swabs from previous days.

This second plot is from the end of the two-week period. The red dots are from the swabs on day 14, and all the grey dots are from swabs on previous days. As project microbiologist Rich explains,

"It looks as though perhaps that the points are becoming a little bit closer together - a hint that there is such a thing as a set of bacterial species that are happy on chopping boards. In the past, at day zero, you had all sorts of things living on them, and then the ones that aren't so happy on plastic or wood are dying off." 

So whilst we didn't see much difference between wooden and plastic boards, we did perhaps see the beginnings of an emerging, generic "chopping board" community of bacteria.