![\"SEM](\"https:\/\/cdn.sci.news\/images\/enlarge14\/image_15045e-LCPH1.jpg\")
<\/a><\/p>\nSEM images of LCAP films incubated undisturbed for more than a year in pristine forest soil. The arrow in panel (d) points at an object inside of such a cavity that might represent a (damaged) microbial cell; however, these were found very rarely; empty cavities were more representative (a-c). Image credit: Lerner et al., doi: 10.1093\/ismejo\/wrag203.<\/p>\n
\u201cPlastic waste and its deterioration into micro- and nanoplastics, paired with slow biodegradation of most present-day plastic materials, has developed into a major environmental and human health concern,\u201d said lead author Dr. Harry Lerner and his colleagues from the University of Konstanz.<\/p>\n
\u201cIn addition to being recalcitrant physical pollutants, plastic debris can act as a vector for transporting chemical contaminants and colonizing microbes.\u201d<\/p>\n
\u201cFurthermore, microorganisms inhabiting the plastisphere, the biofilm community on plastic surfaces, have been shown to harbor disproportionately high levels of antibiotic resistance genes, raising concerns about plastic-mediated dissemination of antibiotic resistance genes throughout ecosystems.\u201d<\/p>\n
In the study, the researchers buried strips of a biodegradable plastic called LCAP, made from long-chain molecules derived from plant oils, in forest soil for more than a year.<\/p>\n
Microscopic images later showed the plastic riddled with tiny, bacteria-shaped pits, evidence that microbes had been eating away at its surface.<\/p>\n
\u201cWe buried small pieces of LCAP bioplastic film in the upper humus layer in the forest at the university\u2019s botanical garden, about ten centimeters deep,\u201d Dr. Lerner said.<\/p>\n
\u201cThis layer is where the breakdown of cellulose and other natural polymers, such as cutin \u2014 a plant-based polyester \u2014 takes place.\u201d<\/p>\n
By sequencing the DNA of soil microbes thriving on the plastic, the scientists identified a bacterial enzyme, which they named LCPH1, that closely resembled a class of proteins bacteria use to disable penicillin-type antibiotics.<\/p>\n
Structural modeling showed the enzyme had an unusually wide, open active site \u2014 nicknamed a \u2018pac-man\u2019 shape \u2014 capable of grabbing both plastic strands and antibiotic molecules.<\/p>\n
The enzyme also broke down the bioplastic into its component parts and also destroyed penicillin and ampicillin, even stripping the drugs of their ability to kill bacteria.<\/p>\n
The findings raise a provocative question for the growing field of plastic pollution research.<\/p>\n
\u201cThe enzyme\u2019s structure resembles that of esterases, but also that of beta-lactamases, which are bacterial enzymes that are capable of cleaving the beta-lactam ring of certain antibiotics, such as penicillin, thereby making bacteria resistant to antibiotics,\u201d Dr. Lerner said.<\/p>\n
\u201cThe plastisphere is a new habitat in our environment,\u201d added Dr. David Schleheck, senior author of the study.<\/p>\n
\u201cHumans have only been introducing plastic into the environment in significant quantities for around 50 to 75 years.\u201d<\/p>\n
\u201cSince then, it has theoretically been available to microbial communities \u2014 such as bacteria, yeasts and fungi \u2014 as an additional source of carbon and energy for their growth.\u201d<\/p>\n
\u201cBy theoretically, I mean that they would certainly like to use the plastic as a growth substrate \u2014 but they cannot, because the materials are actually indigestible to microbial metabolism and are therefore hardly degraded.\u201d<\/p>\n
\u201cI find this encouraging, because it seems that bacteria can adapt to breaking down polyester plastics more quickly than we expected.\u201d<\/p>\n
\u201cTo tackle the environmental problem of plastic pollution, we humans need to work with the capabilities of microbes.\u201d<\/p>\n
\u201cIdeally, this would involve using only polymers with biochemical breaking points, such as the hydrolysable ester bonds in polyesters like LCAP or other types of bioplastics.\u201d<\/p>\n