The Immense Functional Attributes of Maize Rhizosphere Microbiome: A Shotgun Sequencing Approach

The northwest (NW) province of South Africa is a semi-arid area, often disturbed by soil extremes such as drought and intense temperature. However, many functions possessed by the rhizosphere microbiome are still required, especially those inhabiting arid and semi-arid soils. This study involves a metagenomic comparison of the major metabolic attributes of two maize rhizosphere soils and their surrounding soils. Here, we hypothesized that there is a considerable difference between the functional diversity of maize rhizosphere and bulk soils and that the rhizosphere soil has distinct functional traits of agricultural importance. A high-throughput sequencing approach was used to assess the metabolic profile of rhizosphere soil microbiota of maize collected from the Gauteng and NW provinces of South Africa. The relative abundance of 13 functional hit categories was significantly different between the sampling sites. The diversity indices showed a considerable difference between the rhizosphere and surrounding soils. The difference in the chemical properties of the sampling sites was responsible for the variation in the microbial functional composition. Nevertheless, the presence of a high relative abundance of functional categories with unknown functions in SEED subsystem-2 coupled with the large number of functional hits conferring a response to soil stressors viz. oxidative stress, heat shock, osmotic stress, and cold shock noticed in the rhizosphere samples may indicate the presence of novel genes at the sampling sites. Exploring the plant growth-promoting traits of microorganisms present at these sites could eliminate the constraint posed by soil stressors on sustainable agriculture.