The perfect ‘pathogenic’ storm – Deadly bacteria adapt to plastic

The genomics study in the Caribbean and Sargasso Seas marks the first assembly of vibrios bacteria derived from plastic waste.

Recent research has revealed how the interaction between Sargassum kindsplastic marine litter and Vibrio the bacterium makes the ideal “pathogen” that poses a threat to marine biodiversity and public health. Vibrio bacteria commonly found in global waters are the leading cause of marine-related human deaths. For example, Damaged vibriooften known as flesh-eating bacteria, can cause severe foodborne illness from eating seafood and can lead to infections and death from open wounds.

From 2011 onwards, there was a significant increase in the presence of Sargassum, a species of free-living brown macroalgae, in the Sargasso Sea and other open ocean areas such as the Greater Atlantic Sargasso Belt, with regular and unusual algal bloom events occurring on beaches. Additionally, plastic marine litter, originally found in the surface waters of the Sargasso Sea, has become a global problem due to its persistence, persisting for decades longer than natural substrates in the marine ecosystem.

Currently, little is known about the ecological relationship of vibrios with Sargassum. Furthermore, genomic and metagenomic evidence is lacking as to whether vibrios colonizing plastic marine debris and Sargassum can potentially infect humans. With summer in high gear, efforts are underway to find innovative diversion solutions sargassum, could these substrates pose a triple threat to public health?

Florida Atlantic University researchers and collaborators have completely sequenced the genomes of 16 Vibrio strains isolated from eel larvae, plastic marine debris, Sargassumand seawater samples collected from the Caribbean and Sargasso Seas in the North Atlantic Ocean. What they found is Vibrio pathogens have the unique ability to “stick” to microplastics, and that these microbes may simply adapt to the plastic.

“Plastic is a new element that has been introduced into the marine environment and has only been around for about 50 years,” said Tracy Mincer, Ph.D., lead author and assistant professor of biology at FAU’s Harbor Branch Oceanographic Institution and the Harriet L. Wilkes Honors College. “Our laboratory work showed that these Vibrio are extremely aggressive and can seek out and stick to plastic in minutes. We also found that there are attachment factors that microbes use to stick to plastics, and it’s the same kind of mechanism that pathogens use.

The study, published in Water research, illustrates that open-ocean vibrios represent a previously undescribed group of microbes, some representing potential new species, possessing a mixture of pathogenic and low nutrient uptake genes, reflecting their pelagic habitat and the substrates and hosts they colonize. Using a metagenome-assembled genome (MAG), this study represents the first Vibrio spp. a genome assembled from plastic waste.

The study highlights vertebrate pathogenic genes closely related to cholera and non-cholera bacterial strains. Phenotypic testing of cultivars confirmed rapid biofilm formation, hemolytic and lipophospholytic activity, consistent with pathogenic potential.

The researchers also found that zonula blocked toxin or “zot” genes first described in Vibrio cholerae, which is a secreted toxin that increases intestinal permeability, are some of the most well-conserved and selected genes in vibrios that they found. It appears that these vibrios enter through the gut, get stuck in the gut, and become infected that way.

“Another interesting thing we found is a set of genes called ‘zot’ genes that cause leaky gut syndrome,” Minser said. “For example, if a fish eats a piece of plastic and gets infected from that Vibriowhich then leads to leaky gut and diarrhea, it will release waste nutrients such as nitrogen and phosphate that could stimulate Sargassum growth and other surrounding organisms.

The findings show some Vibrio spp. in this environment they have an “omnivorous” lifestyle targeting both plant and animal hosts combined with the ability to persist in oligotrophic conditions. With increased human-Sargassum – plastic marine litter interactions, the associated microbial flora of these substrates may contain potent opportunistic pathogens. Importantly, some cultivation-based data show that they are discarded Sargassum appear to contain large amounts Vibrio bacteria.

“I don’t think at this point anyone really thought about these microbes and their ability to cause infections,” Minser said. “We really want to make the public aware of these associated risks. In particular, care must be taken regarding the harvesting and handling of Sargassum biomass until the risks are studied more thoroughly.’

Reference: “Sargasso Sea Vibrio Bacteria: Understudied Potential Pathogens in a Disturbed Habitat” by Tracy J. Mincer, Ryan P. Bos, Eric R. Zettler, Shiye Zhao, Alejandro A. Asbun, William D. Orsi, Vincent S. Guzetta, and Linda A. Amaral-Zettler, 3 May 2023, Water research.
DOI: 10.1016/j.waters.2023.120033

Co-authors of the study are the Royal Netherlands Institute for Marine Research NIOZ, the Japan Agency for Marine and Earth Science and Technology, Ludwig Maximilian University of Munich, Germany, Emory University, the University of Amsterdam and the Marine Biological Laboratory.

This research was supported by the National Science Foundation (NSF) (grant OCE-1155671 awarded to Mincer), the FAU World Class Faculty and Scholar Program (awarded to Mincer), NSF (grant OCE-1155571 awarded to Linda A. Amaral-Zettler , PhD, corresponding author, NIOZ), NSF (grant OCE-1155379, awarded to Erik R. Zettler, Ph.D., co-author, NIOZ), NSF grant TUES (DUE-1043468, awarded to Linda Zettler and Erik Zettler).