Urease-producing bacteria can precipitate calcite nano-crystals by producing urease in the presence of urea and calcium. Calcite precipitation resulting from microbial activity is a process which causes cementation of soil particles in nature. The purpose of this study was to isolate urease-producing halophilic bacteria in order to precipitate calcite in saline soil. Natural samples, including soil and saline waters, were selected for this purpose. At First, halophilic bacteria were isolated by salt-containing TSB medium. Then, a selective medium containing phenol red and urea facilitated the isolation of urease-producing bacteria. Hydrolysis of urea by urease causes alkalization of the medium and the formation of pink halo around colonies. Finally, the best isolate was selected for further study by measuring the release of ammonium by the Nessler method. The ability or inability of isolates to produce calcite was investigated by culturing the isolates on sedimentary medium with different salt concentrations for 10 days. In total, 110 halophilic isolates were isolated, among which 58 isolates had the ability of urease production. The microscopic studies of colonies showed that only 6 isolates were able to produce crystals on precipitation medium. Isolate 6 was selected for further study and then analyzed by X-ray diffraction crystals on precipitation medium. Isolate 6 was selected for further study and then analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with an energy dispersive X-ray (EDX) detector. Studies of urease activity showed that this strain released 20.86 mM ammonium after 18 hours. This bacterium was identified by biochemical and molecular analyses and the comparison of its 16S rRNA gene sequence showed 99.92% similarity with the similar gene sequence in Staphylococcus xylosus and then this sequence was submitted in NCBI database with the accession number MG655155. This isolate was able to produce calcite in free salt medium, with salinity up to 10%. Nowadays, many efforts have been made to produce environmental-friendly cements, and therefore, the use of urease-producing halophilic bacteria is an appropriate candidate for bio-cementing in saline environments.
 
 

 

In the present study, seed surface ornamentations in 31 species (34 populations) and the capsule surface sculpturing in five species of the genus Scrophularia L. distributed in Iran were examined using Scanning Electronic Microscopy. Based on the published seed surface terminologies, all examined seeds show the reticulate pattern with scalariform inner ornamentations. However, there is enough but untrustworthy variations in epidermal cell shapes and the walls’ characteristics to divide the seed surface sculpturing patterns into four different groups: (1) cells with completely irregular shape; (2) cells without distinct shape so that their boundaries are not clear; (3) reticulate polygonal cells bordered with distinct walls neither undulate nor vesiculate, divided in two subgroups; forming elongated narrow cells and wide cells; (4) reticulate polygonal cells bordered with undulated or sometimes vesiculate walls divided in two subgroups; forming elongated narrow cells and wide cells. In addition, all the species' seeds can be alveolate, ridged or without distinct alveoli or ridges regarding their surfaces. There have also been variations in size, shape and color of the seeds even in a single individual. There are no applicable features of capsule surface sculpturing analyzed here, based on which species could be classified in certain groups.