Του Γιώργου Λεκάκη
Επιστήμονες που μελετούν τον
παγετώνα στην Κίνα έχουν βρει ιούς ηλικίας σχεδόν 15.000 χρόνων, σε δύο
δείγματα πάγου, που ελήφθησαν από το Θιβετιανό Οροπέδιο. Οι περισσότεροι από
αυτούς τους ιούς, οι οποίοι επιβίωσαν επειδή παρέμειναν κατεψυγμένοι.
Όταν ανέλυσαν τον πάγο,
βρήκαν γενετικούς κώδικες για 33 ιούς. Τέσσερις από αυτούς τους ιούς έχουν ήδη
εντοπιστεί από την επιστημονική κοινότητα. Αλλά τουλάχιστον 28 από αυτούς είναι
νέοι. Περίπου οι μισοί από αυτούς φάνηκαν να έχουν επιβιώσει εξ αιτίας του
πάγου.
ΠΕΡΙΣΣΟΤΕΡΑ για τους ΙΟΥΣ, ΕΔΩ.
Τα ευρήματα θα μπορούσαν να
βοηθήσουν τους επιστήμονες να καταλάβουν πώς οι ιοί έχουν εξελιχθεί κατά την
διάρκεια αιώνων. Για αυτήν τη μελέτη, οι επιστήμονες δημιούργησαν επίσης μια
νέα, εξαιρετικά καθαρή μέθοδο ανάλυσης μικροβίων και ιών στον πάγο “χωρίς να μολύνουν”.
Οι ερευνητές ανέλυσαν πυρήνες
πάγου που ελήφθησαν το 2015 από το στρώμα πάγου της κορυφής Guliya (ύψους 6.820
μ.) στην δυτική Κίνα.
ΠΗΓΗ: Zhi-Ping Zhong (*), Funing
Tian, Simon Roux, M. Consuelo Gazitúa, Natalie E. Solonenko, Yueh-Fen Li, Mary
E. Davis, James L. Van Etten, Ellen Mosley-Thompson, Virginia I. Rich, Matthew
B. Sullivan & Lonnie G. Thompson «Glacier ice archives nearly 15,000-year-old microbes and phages», περ. Microbiome, vol. 9,
αρ. 160 (2021), 20.7.2021. ΑΡΧΕΙΟΝ ΠΟΛΙΤΙΣΜΟΥ, 21.7.2021.
(*) ο Zhi–Ping Zhong, επί κεφαλής συγγραφέας της μελέτης είναι ερευνητής στο
The State State University Byrd Polar and Climate Research.
Glacier ice archives information, including microbiology, that helps
reveal paleoclimate histories and predict future climate change. Though
glacier-ice microbes are studied using culture or amplicon approaches, more
challenging metagenomic approaches, which provide access to functional,
genome-resolved information and viruses, are under-utilized, partly due to low
biomass and potential contamination.
Results
We expand existing clean sampling procedures using controlled artificial
ice-core experiments and adapted previously established low-biomass metagenomic
approaches to study glacier-ice viruses. Controlled sampling experiments
drastically reduced mock contaminants including bacteria, viruses, and free DNA
to background levels. Amplicon sequencing from eight depths of two Tibetan
Plateau ice cores revealed common glacier-ice lineages including
Janthinobacterium, Polaromonas, Herminiimonas, Flavobacterium, Sphingomonas,
and Methylobacterium as the dominant genera, while microbial communities were
significantly different between two ice cores, associating with different
climate conditions during deposition. Separately, ~355- and ~14,400-year-old
ice were subject to viral enrichment and low-input quantitative sequencing,
yielding genomic sequences for 33 vOTUs. These were virtually all unique to
this study, representing 28 novel genera and not a single species shared with
225 environmentally diverse viromes. Further, 42.4% of the vOTUs were
identifiable temperate, which is significantly higher than that in gut, soil,
and marine viromes, and indicates that temperate phages are possibly favored in
glacier-ice environments before being frozen. In silico host predictions linked
18 vOTUs to co-occurring abundant bacteria (Methylobacterium, Sphingomonas, and
Janthinobacterium), indicating that these phages infected ice-abundant
bacterial groups before being archived. Functional genome annotation revealed
four virus-encoded auxiliary metabolic genes, particularly two motility genes
suggest viruses potentially facilitate nutrient acquisition for their hosts.
Finally, given their possible importance to methane cycling in ice, we focused
on Methylobacterium viruses by contextualizing our ice-observed viruses against
123 viromes and prophages extracted from 131 Methylobacterium genomes,
revealing that the archived viruses might originate from soil or plants.
Conclusions
Together, these efforts further microbial and viral sampling procedures
for glacier ice and provide a first window into viral communities and functions
in ancient glacier environments. Such methods and datasets can potentially
enable researchers to contextualize new discoveries and begin to incorporate
glacier-ice microbes and their viruses relative to past and present climate
change in geographically diverse regions globally.
