Antarctic Hairgrass Rhizosphere Microbiomes: Microscale Effects Shape Diversity, Structure, and Function

Abstract

The rhizosphere microbiome of the native Antarctic hairgrass Deschampsia antarctica from the central maritime Antarctic was investigated using 16S RNA metagenomics and compared to those of the second native Antarctic plant Colobanthus quitensis and closely related temperate D. cespitosa . The rhizosphere microbial communities of D. antarctica and D. cespitosa had high taxon richness, while that of C. quitensis had markedly lower diversity. The majority of bacteria in the rhizosphere communities of the hairgrass were affiliated to Proteobacteria , Bacteroidetes , and Actinobacteria . The rhizosphere of C. quitensis was dominated by Actinobacteria . All microbial communities included high proportions of unique amplicon sequence variants (ASVs) and there was high heterogeneity between samples at the ASV level. The soil parameters examined did not explain this heterogeneity. Bacteria belonging to Actinobacteria , Bacteroidetes , and Proteobacteria were sensitive to fluctuations in the soil surface temperature. The values of the United Soil Surface Temperature Influence Index (UTII, I t i ) showed that variations in most microbial communities from Galindez Island were associated with microscale variations in temperature. Metabolic predictions in silico using PICRUSt 2.0, based on the taxonomically affiliated part of the microbiomes, showed similarities with the rhizosphere community of D. antarctica in terms of the predicted functional repertoire. The results obtained indicate that these communities are involved in the primary processes of soil development (particularly the degradation of lignin and lignin-derived compounds) in the central maritime Antarctic and may be beneficial for the growth of Antarctic vascular plants. However, due to the limitations associated with interpreting PICRUSt 2.0 outputs, these predictions need to be verified experimentally.

Moss bank composition on Galindez Island (Argentine Islands, maritime Antarctic)

“…Yet, there are moss banks comparable in depth to those from Lazorev Bay within the more northern region of the Argentine Islands. The prevalence of micro-conditions over the latitude gradient is also shown by other studies(Nuzhyna et al 2021;Prekrasna et al 2022).Drainage is a crucial factor for the moss banks' development, as it was noted byOchyra et al (2008). Development of thick moss banks (1-2 m) on the well-drained substrate in the maritime Antarctic supports this statement.…”

Study of the Bacterial, Fungal, and Archaeal Communities Structures near the Bulgarian Antarctic Research Base “St. Kliment Ohridski” on Livingston Island, Antarctica

“…This sample exhibited the highest relative abundance of Actinobacteria among all samples in our study. Coupled with the elevated prevalence of Proteobacteria and Bacteroidetes, it mirrors a bacterial composition akin to previous Antarctic rhizoanalyses [61,62]. The high diversity could be attributed to the properties of the plant rhizosphere.…”

“…Studies in more temperate climate zones have shown decreased bacterial diversity in the plant rhizosphere than in the surrounding bulk soil due to selective interactions between the plant and the bacterial species [63]. However, Antarctic plants have also been shown to function as harbors against the unfavorable conditions of cold, oligotrophic deserts by moisture retention, easing temperature stress, preventing desiccation, and providing nutrients to the community [62].…”

Study of the Bacterial, Fungal, and Archaeal Communities Structures near the Bulgarian Antarctic Research Base “St. Kliment Ohridski” on Livingston Island, Antarctica

“…This sample exhibited the highest relative abundance of Actinobacteria among all samples in our study. Coupled with the elevated prevalence of Proteobacteria and Bacteroidetes, it mirrors a bacterial composition akin to previous Antarctic rhizoanalyses [52,53]. The high diversity could be attributed to the properties of the plant rhizosphere.…”

“…Studies in more temperate climate zones have shown decreased bacterial diversity in the plant rhizosphere than in surrounding bulk soil due to selective interactions between the plant and the bacterial species [54]. However, Antarctic plants have also been shown to function as harbors against the unfavorable conditions of cold, oligotrophic deserts by moisture retention, easing temperature stress, preventing desiccation, and providing nutrients to the community [53].…”