Changes in soil taxonomic and functional diversity resulting from gamma irradiation

Abstract

Little is known of the effects of ionizing radiation exposure on soil biota. We exposed soil microcosms to weekly bursts of 60 Co gamma radiation over six weeks, at three levels of exposure (0.1 kGy/hr/wk [low], 1 kGy/hr/wk [medium] and 3 kGy/hr/wk [high]). Soil DNA was extracted, and shotgun metagenomes were sequenced and characterised using MG-RAST. We hypothesized that with increasing radiation exposure there would be a decrease in both taxonomic and functional diversity. While bacterial diversity decreased, diversity of fungi and algae unexpectedly increased, perhaps because of release from competition. Despite the decrease in diversity of bacteria and of biota overall, functional gene diversity of algae, bacteria, fungi and total biota increased. Cycles of radiation exposure may increase the range of gene functional strategies viable in soil, a novel ecological example of the effects of stressors or disturbance events promoting some aspects of diversity. Moreover, repeated density-independent population crashes followed by population expansion may allow lottery effects, promoting coexistence. Radiation exposure produced large overall changes in community composition. Our study suggests several potential novel radiation-tolerant groups: in addition to Deinococcus-Thermus, which reached up to 20% relative abundance in the metagenome, the phyla Chloroflexi (bacteria), Chytridiomycota (fungi) and Nanoarcheota (archaea) may be considered as radiation-tolerant.

High temperatures enhance the microbial genetic potential to recycle C and N from necromass in high‐mountain soils

“…Other long‐term studies have conversely reported a shift in microbial C‐substrate degradation towards more labile substrates, which was attributed to increased plant inputs (Luo et al, 2014; Zhou et al, 2012). In our study, we found no detectable changes in TC or in DOC (representing a more readily available C pool, Table 1), which is in accordance with findings from an incubation study with similar duration (Ogwu et al, 2019). At 15°C, the majority of differentially abundant CAZy families increased, pointing towards an increased C‐cycling potential (Figure 6).…”

Sterilize Methods Comparison for Soils: Cost, Time, and Efficiency

“…On the one hand, it would increase production costs due to the consumption of electricity and gas, and, on the other hand, excessive heating of the support could lead to the formation of toxic compounds for some microorganisms [24]. On the other hand, soils subjected to gamma irradiation could have a taxonomically different biota than control soils, and the diversity of this biota will differ according to the radiation dose received [25]. DOI: 10.2147/ijm Available online at Journals.aijr.org…”

“…In line with this, each cycle would avoid the possibility of spore viability or other resistance structures, it could be a possible explanation for the low growth for advanced cycles [27]. Sterilization by autoclave has been reported in microcosm bioremediation studies [28]- [30] and, with irradiation, are de most used methods because do not produce chemicals residues, however, it is reported that could alter soil properties [31] and have taxonomic different microbiota in comparison of control soils and diversity which depends of the radiation doses [25].…”

A rather dry subject; investigating the study of arid-associated microbial communities

“…With the advent of new techniques and reduced sequencing cost, came a greater understanding of the influence of abiotic and biotic factors acting on microbial communities. Temperature [45][46][47][48], UV exposure [49,50], salinity [51,52], humidity [53], pH [54], irradiation [55], pressure [56], pollution [57] and oxygen concentration [58] have all been demonstrated to influence microbiomes.…”