15,000-Year-Old Viruses and Bacteria Found in Glacier Ice from Tibet

A team of U.S. researchers has found ancient viruses and bacteria in ice from two cores drilled on the summit and plateau of the Guliya ice cap in northwestern Tibetan Plateau, China.

Ohio State University researchers cut an ice core retrieved from the Guliya ice cap in the Kunlun Mountains in Tibet in 2015. Image credit: Giuliano Bertagna, Byrd Polar and Climate Research Center, Ohio State University.

“While glacier ice cores provide climate information over tens to hundreds of thousands of years, study of microbes is challenged by ultra-low-biomass conditions, and virtually nothing is known about co-occurring viruses,” said lead author Dr. Zhi-Ping Zhong, a scientist in the Byrd Polar and Climate Research Center and the Department of Microbiology at Ohio State University.

“We establish ultra-clean microbial and viral sampling procedures and apply them to two ice cores from the Guliya ice cap to study these archived communities.”

Using their novel procedures, together with previously described decontamination methods, the researchers analyzed microbial and viral communities in the samples of 520- and 15,000-year-old glacier ice.

The microbes differed significantly across the two cores, presumably representing the very different climate conditions at the time of deposition.

Collectively, the samples contained 254 genera of bacteria, 118 of which were identified to the genus level.

“Genera including Janthinobacterium (relative abundance 1.0-23.8%), Polaromonas (2.6-4.1%), Flavobacterium (2.3-23.6%), and unknown genera within the families Comamonadaceae (15.5-24.3%) and Microbacteriaceae (7.1-48.5%) were abundant in the samples,” the scientists said.

“This indicates that members belonging to these lineages are adapted to cold environments and may subsist over long periods of time, although their relative abundances vary across ice core depths.”

The analysis also revealed 33 viral populations that represented four known genera and likely 28 novel viral genera.

“In silico host predictions linked 18 of the 33 viral populations to co-occurring abundant bacteria, including Methylobacterium, Sphingomonas, and Janthinobacterium, indicating that viruses infected several abundant microbial groups,” the study authors said.

“Together, these experiments establish a clean procedure for studying microbial and viral communities in low-biomass glacier ice and provide baseline information for glacier viruses, some of which appear to be associated with the dominant microbes in these ecosystems.”

The team’s paper was published online on the bioRxiv.org preprint platform.

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Zhi-Ping Zhong et al. Glacier ice archives fifteen-thousand-year-old viruses. bioRxiv, published online January 7, 2020; doi: 10.1101/2020.01.03.894675