Abstract
Commercial table salt is a condiment with food preservative properties by decreasing water activity and increasing osmotic pressure. Salt is also a source of halophilic bacteria and archaea. In the present research, the diversity of halotolerant and halophilic microorganisms was studied in six commercial table salts by culture-dependent and culture-independent techniques. Three table salts were obtained from marine origins: Atlantic Ocean, Mediterranean (Ibiza Island), and Odiel marshes (supermarket marine salt). Other salts supplemented with mineral and nutritional ingredients were also used: Himalayan pink, Hawaiian black, and one with dried vegetables known as Viking salt. The results of 16S rRNA gene sequencing reveal that the salts from marine origins display a similar archaeal taxonomy, but with significant variations among genera. Archaeal taxa Halorubrum, Halobacterium, Hallobellus, Natronomonas, Haloplanus, Halonotius, Halomarina, and Haloarcula were prevalent in those three marine salts. Furthermore, the most abundant archaeal genera present in all salts were Natronomonas, Halolamina, Halonotius, Halapricum, Halobacterium, Haloarcula, and uncultured Halobacterales. Sulfitobacter sp. was the most frequent bacteria, represented almost in all salts. Other genera such as Bacillus, Enterococcus, and Flavobacterium were the most frequent taxa in the Viking, Himalayan pink, and black salts, respectively. Interestingly, the genus Salinibacter was detected only in marine-originated salts. A collection of 76 halotolerant and halophilic bacterial and haloarchaeal species was set by culturing on different media with a broad range of salinity and nutrient composition. Comparing the results of 16S rRNA gene metataxonomic and culturomics revealed that culturable bacteria Acinetobacter, Aquibacillus, Bacillus, Brevundimonas, Fictibacillus, Gracilibacillus, Halobacillus, Micrococcus, Oceanobacillus, Salibacterium, Salinibacter, Terribacillus, Thalassobacillus, and also Archaea Haloarcula, Halobacterium, and Halorubrum were identified at least in one sample by both methods. Our results show that salts from marine origins are dominated by Archaea, whereas salts from other sources or salt supplemented with ingredients are dominated by bacteria.
Highlights
Sodium chloride, table salt, is widely used in the food industry as a taste, texture, and flavor enhancer (Henney et al, 2010a), stabilizer, and food preservative (Albarracín et al, 2011)
Comparing the culturomics results with the previous studies, of those, 27 isolates belonged to halotolerant and slightly halophilic bacteria, 45 strains belonged to moderately halophilic bacteria, and one genus corresponded to extremely halophilic bacteria, whereas six archaeal strains were isolated and identified
The next-generation sequencing analysis revealed that the three marine salts were rich in archaea, while the Himalayan pink salt, black salt, and Viking salt were rich in bacteria
Summary
Table salt, is widely used in the food industry as a taste, texture, and flavor enhancer (Henney et al, 2010a), stabilizer, and food preservative (Albarracín et al, 2011). Most processed products contain sodium chloride as a preservative, which strongly affects osmotic pressure (Albarracín et al, 2011). In the process of salting, sodium and chloride can interact with water molecules and reduce the water activity of the food (Tim, 2002). Salinity can prevent microbial spoilage (Henney et al, 2010b). In the presence of salt, microbial cells spend more energy by pumping sodium out from their cells to cope with the harsh effect of the osmotic shock (Henney et al, 2010b)
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