If you're a parent, you know that kids' bath toys can get pretty gross, especially the ones with a small hole that allows water to get in and never come out. Well, these scientists were inspired by that observation to actually figure out what's inside that gross black moldy residue. To do this, they collected "19 real bath toys (e.g., rubber ducks) from five different Swiss households" (in the acknowledgements, they thank the children "for the generous donation of their beloved bath toys"). They then proceeded to "dissect" the toys in half and use a variety of methods to characterize the gunk growing inside. Unsurprisingly, they found fungi (mold), as well as "dense biofilms with complex bacterial and fungal communities."
Check out Figure 1 below for all the gory details... if you dare!
Ugly ducklings—the dark side of plastic materials in contact with potable water
"Bath toys pose an interesting link between flexible plastic materials, potable water, external microbial and nutrient contamination, and potentially vulnerable end-users. Here, we characterized biofilm communities inside 19 bath toys used under real conditions. In addition, some determinants for biofilm formation were assessed, using six identical bath toys under controlled conditions with either clean water prior to bathing or dirty water after bathing. All examined bath toys revealed notable biofilms on their inner surface, with average total bacterial numbers of 5.5 × 106 cells/cm2 (clean water controls), 9.5 × 106 cells/cm2 (real bath toys), and 7.3 × 107 cells/cm2 (dirty water controls). Bacterial community compositions were diverse, showing many rare taxa in real bath toys and rather distinct communities in control bath toys, with a noticeable difference between clean and dirty water control biofilms. Fungi were identified in 58% of all real bath toys and in all dirty water control toys. Based on the comparison of clean water and dirty water control bath toys, we argue that bath toy biofilms are influenced by (1) the organic carbon leaching from the flexible plastic material, (2) the chemical and biological tap water quality, (3) additional nutrients from care products and human body fluids in the bath water, as well as, (4) additional bacteria from dirt and/or the end-users’ microbiome. The present study gives a detailed characterization of bath toy biofilms and a better understanding of determinants for biofilm formation and development in systems comprising plastic materials in contact with potable water."
Bonus figure from the main text:
Visualization of biofilms on the inner surface of bath toys. a The inner surface of a bath toy used under real conditions. b Optical coherence tomography image of the biofilm structure and thickness of the same bath toy (scale bar: 50 µm). c Scanning electron microscopy image revealing the complex structure and composition of these bath toy biofilms. Colors were added artificially to draw attention to varied structures (scale bar: 2 µm).
For additional images, see supplementary information Related content: Do you know what’s growing in your dishwasher? Do you want to?These plastic-eating worms could be the solution to pollution.Microbiologists discover caffeine-adapted bacteria living in the sludge in their office coffee machine.