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The Dong Taijinar (DT) and Xi Taijinar (XT) Salt Lakes have been extensively researched for their mineral richness. However, the composition and distribution of their microbial communities are still poorly known. In this study, we employed metagenomic sequencing to explore the diversity and potential functions of the microbial populations in DT and XT. Our findings indicate that the salinity levels in DT (332.18–358.30 g/L) were tenfold higher than in XT (20.09–36.83 g/L). Notably, archaea dominated the DT domain at 96.16%, while bacteria prevailed in XT at 93.09%. In DT, the bacterial community comprised 33 phyla and 1717 genera, with Marinobacter emerging as the dominant genus, showing a positive correlation with the total phosphorus content. The archaeal community in DT included four main phyla and 153 genera. The most abundant genera were Natronomonas (24.61%) and Halorubrum (23.69%), which had a strong positive correlation with the concentrations of Na+, Ca2+, and Cl−. Conversely, XT hosted 33 phyla and 1906 bacterial genera, with Loktanella as the dominant genus. The archaeal taxonomy in XT encompassed four phyla and 149 genera. In both salt lakes, Proteobacteria and Euryarchaeota were the most abundant bacterial and archaeal phyla, respectively. Our analysis of the halophilic mechanisms of these microorganisms suggests that the bacteria in XT tend to synthesize compatible solutes, whereas the archaea in DT adopt a 'salt-in' strategy, integrating salt into their cellular machinery to cope with the high-salinity environment. [ABSTRACT FROM AUTHOR]

Ectoine has gained considerable attention as a high-value chemical with significant application potential and market demand. This study aimed to increase ectoine yields by blocking the metabolic shunt pathway of l-aspartate-4-semialdehyde, the precursor substrate in ectoine synthesis. The homoserine dehydrogenase encoded by hom in H. campaniensis strain XH26 is responsible for the metabolic shunt of l-aspartate-4-semialdehyde to glycine. CRISPR/Cas9 technology was used to seamlessly knockout hom, blocking the metabolic shunt pathway to increase ectoine yields. The ectoine yield of XH26/Δhom was 351.13 mg (g CDW)−1 after 48 h of incubation in 500 mL shake flasks using optimal medium with 1.5 mol L−1 NaCl, which was significantly higher than the 239.18 mg (g CDW)−1 of the wild-type strain. Additionally, the absence of the ectoine metabolic shunt pathway affects betaine synthesis, and thus the betaine yields of XH26/Δhom was 19.98 mg (g CDW)−1, considerably lower than the 69.58 mg (g CDW)−1 of the wild-type strain. Batch fermentation parameters were optimized, and the wild-type strain and XH26/Δhom were fermented in 3 L fermenters, resulting in a high ectoine yield of 587.09 mg (g CDW)−1 for the defective strain, which was significantly greater than the ectoine yield of 385.03 mg (g CDW)−1 of the wild-type strain. This study showed that blocking the metabolic shunt of synthetic substrates effectively increases ectoine production, and a reduction in the competitively compatible solute betaine appears to promote increased ectoine synthesis. [ABSTRACT FROM AUTHOR]

Salt lakes are significant components of global inland waters. Salt lake (SL) water can provide precious mineral resource for microbial growth. The prospect of utilizing diluted SL water for cultivation of a terrestrial oil-producing microalga Vischeria sp. WL1 was evaluated under laboratory conditions. Based on the detected mineral element composition, the water from Gouchi Salt Lake was diluted 2, 4, 6 and 8 folds and used with supplementation of additional nitrogen, phosphorus and iron (SL + water). It was found that 4 folds diluted SL + water was most favorable for biomass and oil production. When cultivated in this condition, Vischeria sp. WL1 gained a biomass yield of 0.82 g L -1 and an oil yield of 0.56 g L -1 after 24 days of cultivation, which is comparable to the optimum productivity we previously established. In addition, total monounsaturated fatty acid contents (64.4∼68.1 %) of the oils resulted from cultures in diluted SL + waters were higher than that in the control (55.5 %). It was also noteworthy that in all these cultures the oil contents (652.0∼681.0 mg g -1 ) accounted for the most of the biomass, which are far more than the protein and starch contents. This study demonstrates the feasibility of using SL water as a cost-effective mineral resource to cultivate microalgae for biomass and oil production., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)