Bacterial diversity was studied in the rhizosphere of Suaeda japonica Makino, which is native to Suncheon Bay in South Korea. Soil samples from several sites were diluted serially, and pure isolation was performed by subculture using marine agar and tryptic soy agar media. Genomic DNA was extracted from 29 pure, isolated bacterial strains, after which their 16S rDNA sequences were amplified and analyzed. Phylogenetic analysis was performed to confirm their genetic relationship. The 29 bacterial strains were classified into five groups: phylum Firmicutes (44.8%), Gamma proteobacteria group (27.6%), Alpha proteobacteria group (10.3%), phylum Bacteriodetes (10.3%), and phylum Actinobacteria (6.8%). The most widely distributed genera were Bacillus (phylum Firmicutes), and Marinobacterium, Halomonas, and Vibrio (Gamma proteobacteria group). To confirm the bacterial diversity in rhizospheres of S. japonica, the diversity index was used at the genus level. The results show that bacterial diversity differed at each of the sampling sites. These 29 bacterial strains are thought to play a major role in material cycling at Suncheon Bay, in overcoming the sea/mud flat-specific environmental stress. Furthermore, some strains are assumed to be involved in a positive interaction with the halophyte S. japonica, as rhizospheric flora, with induction of growth promotion and plant defense mechanism.

The use of calcite-forming bacteria (CFB) in crack remediation and durability improvements in construction materials creates a permanent and environmentally-friendly material. Therefore, research into this type of application is stimulating interdisciplinary studies between microbiology and architectural engineering. However, the mechanisms giving rise to these materials are dependent on calcite precipitation by the metabolism of the CFB, which raises concerns about possible hazards to cement-based construction due to microbial metabolic acid production. The aim of this study was to determine target microorganisms that possibly can have bio-corrosive effects on cement mortar and to assess multi-functional CFBs for their safe application to cement structures. The chalky test was first used to evaluate the CaCO3 solubilization feature of construction sites by fungi, yeast, bacterial strains. Not all bacterial strains are able to solubilize CaCO3, but C. sphaerospermum KNUC253 or P. prolifica KNUC263 showed CaCO3 solubilization activity. Therefore, these two strains were identified as target microorganisms that require control in cement structures. The registered patented strains Bacillus aryabhatti KNUC205, Arthrobacter nicotianae KNUC2100, B. thuringiensis KNUC2103 and Stenotrophomonas maltophilia KNUC2106, reported as multifunctional CFB (fungal growth inhibition, crack remediation, and water permeability reduction of cement surfaces) and isolated from Dokdo or construction site were unable to solubilize CaCO3. Notably, B. aryabhatti KNUC205 and A. nicotianae KNUC2100 could not hydrolyze cellulose or protein, which can be the major constituent macromolecules of internal materials for buildings. These results show that several reported multi-functional CFB can be applied to cement structures or diverse building environments without corrosive or bio-deteriorative risks. 3, 5, 8, 9, 11, 12, 15, 18-21, 27-28, 30, 33, 34] Key words