Penguin poo as a source of antibiotic-resistant genes

Antibiotic-resistant genes (ARGs), which can pass into bacteria and make them immune to antibiotics, have been detected in more or less every environment on Earth. They are present even in Antarctica, despite its isolated location, small human population, and extreme weather. Scientists have known that penguins play a role as disseminators of pathogens with ARGs. But a recent study suggests that this might be happening on a bigger scale than previously thought (Environ. Sci. Technol. 2024, 10.1021/acs.est.4c02732).

Researchers from the University of Science and Technology of China say that penguin guano might be propagating ARG pollution even more than their local human counterparts. Ice and snow melts move guano from penguin colonies into lakes, creating sediments rich in organic matter, nitrogen, and phosphorus. In this work, the researchers analyzed samples of these ornithogenic lake sediments (OLS) from around colonies, as well as nonornithogenic lake sediments (NOLS) from around scientific research stations. In all, samples were taken from 16 Antarctic lakes.

ARGs were present in greater abundance and diversity in samples of OLS than in those of NOLS. To confirm the presence of penguin poo, the researchers looked for chemicals that the material has a lot of, such as phosphorus, sulfur, barium, copper, and zinc. They then quantified the ARGs using high-throughput quantitative polymerase chain reaction.

The findings indicate that penguin-driven dissemination of ARGs might greatly outweigh spread from local human activity, says Renbin Zhu, the lead author of the study. This is despite the ever-increasing human footprint altering the ARG profile in the Antarctic environment, especially around research stations.

Penguins account for over 90% of biomass of Antarctic birds and can carry ARGs through long-distance migration; they defecate in and around the Antarctic lakes, which leads to high concentrations of ARGs in the sediments, Zhu says. Thus, penguin migration, food chains, and guano deposition might be closely connected with widespread ARG pollution at the global scale.

This study has important implications for understanding the spread, evolution, and risk assessments of antibiotic resistance in pristine Antarctic environments, Zhu says. It highlights the need for more comprehensive monitoring of antibiotic resistance to understand the dissemination mechanisms. “We are working on further studies on the evolution of ARGs in Antarctic environments and the effects of natural and anthropogenic factors,” he adds.