Changes of the Bacterial Abundance and Communities in Shallow Ice Cores from Dunde and Muztagata Glaciers, Western China

Abstract

In this study, six bacterial community structures were analyzed from the Dunde ice core (9.5-m-long) using 16S rRNA gene cloning library technology. Compared to the Muztagata mountain ice core (37-m-long), the Dunde ice core has different dominant community structures, with five genus-related groups Blastococcus sp./Propionibacterium, Cryobacterium-related., Flavobacterium sp., Pedobacter sp., and Polaromas sp. that are frequently found in the six tested ice layers from 1990 to 2000. Live and total microbial density patterns were examined and related to the dynamics of physical-chemical parameters, mineral particle concentrations, and stable isotopic ratios in the precipitations collected from both Muztagata and Dunde ice cores. The Muztagata ice core revealed seasonal response patterns for both live and total cell density, with high cell density occurring in the warming spring and summer months indicated by the proxy value of the stable isotopic ratios. Seasonal analysis of live cell density for the Dunde ice core was not successful due to the limitations of sampling resolution. Both ice cores showed that the cell density peaks were frequently associated with high concentrations of particles. A comparison of microbial communities in the Dunde and Muztagata glaciers showed that similar taxonomic members exist in the related ice cores, but the composition of the prevalent genus-related groups is largely different between the two geographically different glaciers. This indicates that the micro-biogeography associated with geographic differences was mainly influenced by a few dominant taxonomic groups.

Clean Low-Biomass Procedures and Their Application to Ancient Ice Core Microorganisms

“…Members belonging to the genus Methylobacterium were also reported to dominate the microbial community in ancient ice cores from many previous studies ( Miteva, 2008 ; Segawa et al, 2010 ; Antony et al, 2012 ; Miteva et al, 2015 , 2016 ), including several microbial investigations of the Guliya ice cap ice cores using culture-dependent methods ( Christner et al, 2000 , 2001 ; Christner, 2003 ). Five other genera with relative abundances of 0.1–4.5%, which had recognized names, were also previously reported to be abundant in glacier ice cores, including the genera Flavobacterium ( Liu et al, 2015 ; Chen et al, 2016 ), Janthinobacterium ( Christner, 2003 ; Miteva, 2008 ), Polaromonas ( Liu et al, 2009 ; An et al, 2010 ; Chen et al, 2016 ), Sphingomonas ( An et al, 2010 ; Miteva et al, 2016 ), and Rhodobacter ( Liu et al, 2015 ). The detection of bacterial sequences belonging to similar genera in ice core samples from different glaciers located around the world can be explained by the ubiquitous distribution of certain species in geographically distant environments ( Baas Becking, 1934 ; Martiny et al, 2006 ).…”

“…Thus, microorganisms immured in ice cores represent those in the atmosphere at the time of deposition and hence reflect environmental conditions during the same time period ( Priscu et al, 2007 ; Xiang et al, 2009 ). Previous investigations of the microbial community in polar glaciers (e.g., Miteva et al, 2009 , 2015 ; Santibanez-Avila, 2016 ) and low-latitude glaciers (e.g., Yao et al, 2008 ; Chen et al, 2016 ) have suggested that microbial diversity and abundance preserved in deep ice cores are correlated with dust particle concentrations, local climate conditions, and global atmospheric circulation. Usually the biomass is very low in most glacier ice samples, with the estimated number of microbial cells ranging from 10 2 to 10 4 cells ml -1 ( Miteva, 2008 ).…”

Paleo-Rock-Hosted Life on Earth and the Search on Mars: A Review and Strategy for Exploration

“…Antarctic permafrost (brown crosses) and subglacial sediments (brown-filled triangles) exhibit cell concentrations that are also greater than those of the adjacent and overlying ice sheets (open triangles). In general, cell concentrations in ice sheets (open squares, triangles, and circles) do not diminish as a function of depth and age as rapidly as observed for permafrost sediments and likely reflect a combination of airborne input flux and in situ metabolism (Chen et al, 2016). Cell concentrations are higher near rock-ice interfaces and in dust-rich ice, pointing to the importance of chemical and physical gradients.…”

Phenotypic divergence of thermotolerance: Molecular basis and cold adaptive evolution related to intrinsic DNA flexibility of glacier‐inhabitingCryobacteriumstrains

“…Cryobacterium strains, within the family Microbacteriaceae , are Gram‐positive, non‐spore‐forming, irregular rod‐shaped, aerobic bacteria (Liu et al ., ). Cryobacterium strains were commonly discovered in cold environments, such as in ice core, surface soil and ice of mountain glaciers (Reddy et al ., ; Liu et al ., ; Chen et al ., ); the Antarctic, Arctic and Siberian permafrost soils (Suzuki et al ., ; Bajerski et al ., ; Schuerger and Nicholson, ); Antarctic sandy intertidal sediments (Yu et al ., ), surface seawater along the Victoria Land coast of Antarctica (Giudice et al ., ) and glacier cryoconite holes in the High Arctic (Singh et al ., ). Although the genus Cryobacterium is widespread in the cryosphere, it may be a rare taxon (Liu et al ., ).…”