Highly specialized bacterial communities within three distinct rhizocompartments of Antarctic hairgrass (Deschampsia antarctica Desv.)

Antarctic hairgrass, Deschampsia antarctica Desv. (Poaceae), is one of the two flowering plants that have an established presence in Maritime Antarctica. It has adapted to varying edaphic and climatic conditions. D. antarctica's associations with soil-dwelling bacteria have long been suspected to add to its remarkable resilience. In this study, three compartments within D. antarctica root system and soil have been investigated as microbial habitats: the rhizosphere (root-adjacent soil particles), rhizoplane (root surface) and endosphere (root interior). For this purpose, a modification of existing methods of bacterial extraction from cryophilic plant rhizocompartments was devised with the temperature sensitivity of the source material in mind. Next-generation targeted 16S rRNA gene amplicon sequencing and a culture-based approach were employed to explore the bacterial community residing within those three rhizocompartments. Results showed that each of the compartments housed a distinct bacterial community not only in terms of phylogenetic diversity but also concerning plant-beneficial and -adaptive traits. Although most cultivable bacteria displayed plant-growth promoting abilities such as rock-phosphate solubilisation and phytohormone production (Arthrobacter spp.), some could be potential pathogens (Clavibacter sp.). This study highlights the need for amending the still scarce information on the microbiome of Antarctic flora but also gives tools and insight to explore it further.