10:00 AM - 10:15 AM
[ACG31-05] The presence of halophiles in Antarctic millennium-scale ice could serve as an indicator of the global glacial climate events: The case study of the Vostok ancient ice
Keywords:Antarctica, Ancient glacier ice, Aeolian microbial communities, Halomonas spp., Glaciation, Nanopore sequencing
This research project aimed to analyze the DNA content of microbial communities found in the deep glacier ice of Antarctica using high throughput Oxford Nanopore sequencing technology. The purpose was to identify and describe the microbial communities present and to identify species that may have served as indicators of past global climate change on Earth.
The samples from the Vostok 5G-1 included adjacent 3460m and 3462m ice segments.
Despite the ice being disturbed by glacier movement and having folded layers, the samples were aged to approximately 560+/-40 Kyr, indicating they were likely deposited during a glacial period such as MIS 14. This is due to the significant eolian dust content found at these depths.
The ice segments were strictly decontaminated in cold room facilities following detergent decontamination in clean room facilities. The meltwater obtained was filtered through 10 kDa and 3 kDa membranes. The resulting matter was used to isolate genomic DNA, amplified with the bacterial v3-v4 region of the 16S rRNA gene-targeted degenerate primers. The amplicons generated (~450 bs in size) were Oxford Nanopore sequenced. The data obtained was basecalled using the Super-accurate with Trim barcodes options. The reads were compared to the entries in Genbank for classification. The controls were also included in the sequencing set.
The analytical chemistry data were obtained by ionic chromatography using the ThermoFisher Scientific INTEGRION system for cations and anions. The dust particle analysis intends to use the Beckman Coulter Counter Multisizer 3.
As a result, a million reads were obtained for each of the three samples (two of ice and one of control). The amplicons for the 3460m ice core generated about 635000 classified reads, for 3462 – about 691000 classified reads, and for controls – 491000 classified reads. Plenty of identified species overlapped all three samples, indicating their contaminant status. The remaining noncontaminant species were uniquely distributed as follows.
Two main findings dominated the aeolian microbial communities for the 3460m ice core: Brevundimonas (three species, major B. variabilis) – about 5800 reads along with scarce Bradyrhizobium australiense – about 700 reads, and Chryseobacterium aquaticum – about 4400 reads.
The adjacent 3462m core showed four unique findings: Sphingomonas (three species, major S. gilva) – about 18600 reads; Rhizorhabdus (three species, major R. starnbergensis) - about 9800 reads; Rhodococcus sovatensis – about 9700 reads, and Psychrobacter (two species, major P. cibarius) – about 8200 reads.
It was surprising to discover that both cores shared almost an equal number of four species of Halomonas, with H. azerica being the most prevalent, followed by H. glaciei, H. maris, and H. sedimenti. These species belong to the Gamma-Proteobacteria and were found in approximately 6400 and 5800 reads, respectively. The halophilic species in both cores suggest dry, winter-like climatic conditions during the deposition period.
We hypothesize that the microbial communities are associated with the aeolian dust of continental origin, which had significant input onto the polar ice sheets during the glacial periods. Our main findings represent the species identified in soil, saline lake/ocean water, sediment, puddle mud, and Antarctic ice.
In addition, the EPICA EDML ice samples from the Holocene and LGM periods were briefly examined. It was discovered that Halomonas spp. were present only in the glacial ice, with approximately 5100 reads for H. azerica, followed by the same three species found in the two Vostok samples. This finding supports the suggested correlation between halophiles and glacial dust/period.
Regarding the chemistry, it was found that the Vostok ice cores under study have a higher concentration of sea salt and crustal dust compared to the penultimate interglacial period, but lower levels than the glaciation period. More analyses are still underway.
The study found that two segments of ancient glacial ice from the Vostok ice core (about 600,000 years old) contain a unique microbial community structure. The shared component discovered (halophiles, specifically, Halomonas spp.) along with chemical data seems to be associated with aeolian dust input from a cold climatic period, meaning that the ice under study could originate from a cold climatic period in the past. Given the Halomonas spp. inhabit soil from the desert and arid areas from southern continents, their source availability and transportation toward Antarctica have to be evaluated. Further analysis of ice from different sites and deposited under different climatic periods will be helpful.
The samples from the Vostok 5G-1 included adjacent 3460m and 3462m ice segments.
Despite the ice being disturbed by glacier movement and having folded layers, the samples were aged to approximately 560+/-40 Kyr, indicating they were likely deposited during a glacial period such as MIS 14. This is due to the significant eolian dust content found at these depths.
The ice segments were strictly decontaminated in cold room facilities following detergent decontamination in clean room facilities. The meltwater obtained was filtered through 10 kDa and 3 kDa membranes. The resulting matter was used to isolate genomic DNA, amplified with the bacterial v3-v4 region of the 16S rRNA gene-targeted degenerate primers. The amplicons generated (~450 bs in size) were Oxford Nanopore sequenced. The data obtained was basecalled using the Super-accurate with Trim barcodes options. The reads were compared to the entries in Genbank for classification. The controls were also included in the sequencing set.
The analytical chemistry data were obtained by ionic chromatography using the ThermoFisher Scientific INTEGRION system for cations and anions. The dust particle analysis intends to use the Beckman Coulter Counter Multisizer 3.
As a result, a million reads were obtained for each of the three samples (two of ice and one of control). The amplicons for the 3460m ice core generated about 635000 classified reads, for 3462 – about 691000 classified reads, and for controls – 491000 classified reads. Plenty of identified species overlapped all three samples, indicating their contaminant status. The remaining noncontaminant species were uniquely distributed as follows.
Two main findings dominated the aeolian microbial communities for the 3460m ice core: Brevundimonas (three species, major B. variabilis) – about 5800 reads along with scarce Bradyrhizobium australiense – about 700 reads, and Chryseobacterium aquaticum – about 4400 reads.
The adjacent 3462m core showed four unique findings: Sphingomonas (three species, major S. gilva) – about 18600 reads; Rhizorhabdus (three species, major R. starnbergensis) - about 9800 reads; Rhodococcus sovatensis – about 9700 reads, and Psychrobacter (two species, major P. cibarius) – about 8200 reads.
It was surprising to discover that both cores shared almost an equal number of four species of Halomonas, with H. azerica being the most prevalent, followed by H. glaciei, H. maris, and H. sedimenti. These species belong to the Gamma-Proteobacteria and were found in approximately 6400 and 5800 reads, respectively. The halophilic species in both cores suggest dry, winter-like climatic conditions during the deposition period.
We hypothesize that the microbial communities are associated with the aeolian dust of continental origin, which had significant input onto the polar ice sheets during the glacial periods. Our main findings represent the species identified in soil, saline lake/ocean water, sediment, puddle mud, and Antarctic ice.
In addition, the EPICA EDML ice samples from the Holocene and LGM periods were briefly examined. It was discovered that Halomonas spp. were present only in the glacial ice, with approximately 5100 reads for H. azerica, followed by the same three species found in the two Vostok samples. This finding supports the suggested correlation between halophiles and glacial dust/period.
Regarding the chemistry, it was found that the Vostok ice cores under study have a higher concentration of sea salt and crustal dust compared to the penultimate interglacial period, but lower levels than the glaciation period. More analyses are still underway.
The study found that two segments of ancient glacial ice from the Vostok ice core (about 600,000 years old) contain a unique microbial community structure. The shared component discovered (halophiles, specifically, Halomonas spp.) along with chemical data seems to be associated with aeolian dust input from a cold climatic period, meaning that the ice under study could originate from a cold climatic period in the past. Given the Halomonas spp. inhabit soil from the desert and arid areas from southern continents, their source availability and transportation toward Antarctica have to be evaluated. Further analysis of ice from different sites and deposited under different climatic periods will be helpful.