Distribution And Enrichment Patterns Of Rhizosphere Bacteria Of Two Typical Desert Plants In The Desert Area

Plants depend mainly upon beneficial interactions between roots and microbes for providing a plethora of functional capacities: nutrient availability,growth promotion,and resistance to biotic and abiotic stressors.The rhizosphere is the most active area for plant-microbe-soil communication,especially in the desert.Here we present a detailed characterization of the rhizosphere microbiomes of typical desert plants(Nitraria sibirica,Haloxylon.ammodendron)by deep sequencing and culture-dependent technologiesand assess microbial diversity and structural differentiation within different niches.The main results are as follows:1)The spatial distribution of the bacteria microbiome in the rhizosphere was concluded.a)The ?-diversity variability of bacterial microbiomes was driven by different biogeographical factors.There is no statistical significance in ?-diversity among different sampling sites and different depth.However ?-diversity where in bulk soil was significantly less than the rhizosphere,which showed ‘Rhizo-type'was the most crucial factors influencing the bacterial ?-diversity.b)According to the bacterial community similarity,it was attributed to four type's metacluster in the sampling area,and the microbiome of sampling area varied significantly(R: 0.84).The result is of great significance for predicting the structure of bacterial community and ecological niche.c)Microbial community structures were mostly distinct across spatial distance and environmental factors.MRT and RDA all verified that the microbial structure in rhizosphere was significantly affected by Rhizo-type,EC and PC.Among sampling sites,the community dissimilarities increased with spatial distance.VPA further indicated that the effects of spatial distance and environmental factors on community variation were far less than their respective effects.d)Network analysis indicated that microbial communities had non-random and functionaldriven co-occurrence patterns and identified three key genus for the stability of the network structure:Nitriliruptor,Arthrobacter and Glycomyces.Further analysis showed that a few of modules in rhizosphere associated with most of the functional traits,rhizosphere ecological functions assumed by a faw bacteria,rather than bulk soil bacterial biologiacal functional traits spread to most of the microbiome.2)Colonization patterns of rhizospheric microbial communities of two plants were expounded.Actinobacteria,Proteobacteria,Chloroflexi,Bacteroidetes,and Firmicutes are significantly enriched in the rhizosphere of the two plants.Rhizospheric microbiome acquisition of N.sibirica were affected by geographical location,the EC and plant coverage,and showed clear trend: MA >MF >YF.However,the steady-state assembly of H.ammodendron rhizospheric microbiomes showed in three sampling site,and it was not affected by geographical location and environment.This study indicated that the microbiome colonized in H.ammodendron rhizosphere was much steady,and so that H.ammodendron can be better adapted to the desert.3)The distribution characteristics of functional genes were revealed.16 s PICRUSt and STAMP analysis showed that gene clusters associated with PGP traits demonstrated the spatial resolution distinguished three sampling location,in which the abundance of nitrogenase and phosphate-solubilizing were the highest in MA.IAA and ACCd gene mainly gathered in rhizosphere soil of fixed sand.The variation of gene clusters related to geochemical cycles was mainly affected by the plant.Genes related to N-assimilation and P-absorption were distributed in Nit_R and bulk soil,while abundace of genes related to P-scavenging and C-cyclic correlation were highest in Hal_R.4)A total of 467 strains of bacteria were isolated through culture-dependent technologies.They were divided into 8 phyla,mainly Actinobacteria(41.2%),Proteobacteria(30.77%),Bacteroides(11.54%),Firmicutes(8.24%)and Chloroflexi(4.95%).The sequencing results showed that the strains only accounted for 10.45% of the high-throughput sequencing,and were mostly the dominant population in high-throughput sequencing results,but the number of sequences accounted for 38.71%(Coverage: 80%).The pattens of bacterial enrichment and functional strain distribution were consistent with that of high-throughput sequencing analysis,which further verified the reliability of the conclusion.In this study,the spatial distribution pattern of rhizospheric microbiome and the mechanism of microbiomes assembled in rhizosphere of different plants in desert areas were expounded,and the distribution patterns of functional genes and strains were clearly defined.The results provide basis for the cultivation of undefined microbes in the future.