Changes in Streptomyces Bacteria in Rhizospheric Soil as Compared to Non-Rhizospheric Soil: A Case Study from North-East of Qatar

This chapter elucidate the changes in the microbial community (especially Streptomyces bacteria) at the saline lands (rhizospheric and non-rhizospheric), and how the presence of native plants, halophytes for example, attract some new species of Streptomyces bacteria by conducting some important biochemical and biological tests. Plants are part of a rich ecosystem including numerous and diverse microorganisms in the soil. It has been long recognized that some of these microbes, such as mycorrhizal fungi or nitrogen fixing symbiotic bacteria, play important roles in plant performance by improving mineral nutrition. The biological activities performed by plants and microorganisms in dry and saline soil play an important role in making them thrive in these extreme environmental conditions. Therefore, in this research, four halophyte plants namely: Caroxylon imbricatum, Sporobolus ioclados, Tamarix aphylla, and Tetraena qatarensis, were chosen to investigate the properties, characteristics, and activities of Streptomyces isolates in these habitats. The chemical and physical properties of soil at the study area (Al Ghariya Sabkha) revealed that pH levels are almost uniform and homogenous across the Sabkha; ranging between 7.7-7.9, and salinity levels were very high at non-rhizospheric soil as compared to the rhizospheric soils, thus, all elements at the rhizospheres of the studied plants have lower concentrations than those at the non-rhizospheric soils. Numerous types of isolates with unique colony characteristics and peculiarities were found in the rhizospheric soil of halophytes. These findings suggest that a considerable number of strains of Streptomyces bacteria have flourished in these miniature habitats within the canopy of these plants. The current study revealed a limited number of species of this genus in the non-rhizospheric soils, only four isolates at this mini-habitat of the halophytes under investigation were recognized, these isolates showed limited characteristics of colony features which included: aerial mycelium color, soluble pigment, reverse color, and the form of the whole colony. The enzyme activities of the isolates that have been studied in the rhizospheric and non-rhizospheric soils have shown more variable isolates in the rhizosphere of the plants under investigation than those of non-rhizospheric soils. The majority of the Streptomyces isolates at these mini-habitats shown a strong antibacterial effect against the strains that were examined, including Gram-positive (B. subtilis, S. aureus, and S. epidermidis) and Gram-negative (E. coli). Overall, the results of this research showed that the properties and characteristics of Streptomyces bacteria explaining their biodiversity were high in rhizospheric soils of halophytes as compared to non-rhizospheric soils.