Preliminary estimates of the number and diversity of the culturable endophytic bacteria from Deschampsia antarctica and Colobanthus quitensis

Abstract

Endophytes are able to promote the plant's growth and are essential for their hosts to overcome biotic and abiotic stress. Plant-promoting capacities of these microorganisms can be crucial for Antarctic plants. The aim of the study was to estimate the number and diversity of culturable endophytic microorganisms from Deschampsia antarctica and Colobanthus quitensis growing in different localities of the West Antarctic Peninsula. Methods. Serial dilutions of the surface-sterilized plant biomass were inoculated on the CASO (Merk, USA) and R2A (Merk, USA) media and cultured at room temperature for a week. Number of colonies and their morphotypes were estimated. Results. The number of colony-forming units in the aboveground part and roots of D. antarctica was 4×106 ±2×106 and 7×106 ±2×106 per g of biomass, respectively. The colony forming units CFU number in the aboveground part of C. quitensis was 3×106±1×106 per g of biomass. The highest number of CFU was in the roots of D. antarctica from Galindez Island on both media (n×107). The highest CFU number in C. quitensis was in plants from Deception Island on nutrient-poor (7×106) and -rich (1×107) media. The lowest value was found for C. quitensis from Cape Pérez (7×103 on R2A and 1×104 on CASO). There was no significant difference in the number of CFU grown on nutrient-poor and nutrient-rich medium, but the morphology of the CFU varied on the two media. 112 pure cultures of endophytes were isolated. The vast majority (78%) of the isolates were gram-negative rods. The number of cultured endophytes of Antarctic vascular plans varied across the samples, which can be affected both by the features of the individual plants and the ecology of sites where they grow. Bacterial communities did not significantly vary in number depending on the medium but did somewhat differ in morphology. A collection of 112 endophyte isolates was developed, which is important to study their genetic and physiological traits and mechanisms of plant-bacteria interaction. Conclusions. Isolation of the endophytic microorganisms is important to study their genetic and physiological traits and mechanisms of plant-bacteria interaction.Keywords: Antarctic hairgrass, Antarctic pearlwort, maritime Antarctica, symbionts of plants