Insights into C1 and C3 assimilation pathways in type I methanotrophic bacterium from co-production of 1,2-propanediol and lactate.

Methanotrophic bacteria are attractive hosts for mining metabolic pathways of C1 assimilation to produce value-added products. Herein, the type I methanotroph Methylotuvimicrobium alcaliphilum 20Z was employed to explore the carbon flux from methane and methanol via the EMP pathway to produce 1,2-propanediol (1,2-PDO). The production of 1,2-PDO on methane was found to be mainly restricted by the lower carbon flux toward the EMP pathway. The co-utilization of C1 substrates and glycerol (C3) could contribute to enhance 1,2-PDO. Lactate was co-produced in much higher amounts than 1,2-PDO. This unexpected product was probably derived from lactaldehyde by inherent aldehyde dehydrogenases. The 1,2-PDO production without increased accumulation of lactate was observed via establishing the acetol-based pathway by propane utilization with the overexpression of pmoD. This is the first study to provide experimental insights into the operation of metabolic routes for 1,2-PDO and lactate co-production from C1 and C3 compounds in methanotrophs.

Sustainable biosynthesis of chemicals from methane and glycerol via reconstruction of multi-carbon utilizing pathway in obligate methanotrophic bacteria.

Obligate methanotrophic bacteria can utilize methane, an inexpensive carbon feedstock, as a sole energy and carbon substrate, thus are considered as the only nature-provided biocatalyst for sustainable biomanufacturing of fuels and chemicals from methane. To address the limitation of native C1 metabolism of obligate type I methanotrophs, we proposed a novel platform strain that can utilize methane and multi-carbon substrates, such as glycerol, simultaneously to boost growth rates and chemical production in Methylotuvimicrobium alcaliphilum 20Z. To demonstrate the uses of this concept, we reconstructed a 2,3-butanediol biosynthetic pathway and achieved a fourfold higher titer of 2,3-butanediol production by co-utilizing methane and glycerol compared with that of methanotrophic growth. In addition, we reported the creation of a methanotrophic biocatalyst for one-step bioconversion of methane to methanol in which glycerol was used for cell growth, and methane was mainly used for methanol production. After the deletion of genes encoding methanol dehydrogenase (MDH), 11.6 mM methanol was obtained after 72 h using living cells in the absence of any chemical inhibitors of MDH and exogenous NADH source. A further improvement of this bioconversion was attained by using resting cells with a significantly increased titre of 76 mM methanol after 3.5 h with the supply of 40 mM formate. The work presented here provides a novel framework for a variety of approaches in methane-based biomanufacturing.

Developments of Riboswitches and Toehold Switches for Molecular Detection-Biosensing and Molecular Diagnostics.

Riboswitches and toehold switches are considered to have potential for implementation in various fields, i.e., biosensing, metabolic engineering, and molecular diagnostics. The specific binding, programmability, and manipulability of these RNA-based molecules enable their intensive deployments in molecular detection as biosensors for regulating gene expressions, tracking metabolites, or detecting RNA sequences of pathogenic microorganisms. In this review, we will focus on the development of riboswitches and toehold switches in biosensing and molecular diagnostics. This review introduces the operating principles and the notable design features of riboswitches as well as toehold switches. Moreover, we will describe the advances and future directions of riboswitches and toehold switches in biosensing and molecular diagnostics.

Comparison of genetic variation between northern and southern populations of Lilium cernuum (Liliaceae): Implications for Pleistocene refugia.

The so-called "Baekdudaegan" (BDDG), a mountain range that stretches along the Korean Peninsula, has been recently proposed as a major "southern" glacial refugium for boreal or temperate plant species based on palaeoecological and, especially, genetic data. Genetic studies comparing genetic variation between population occurring on the BDDG and more northern ones (i.e. in NE China and/or in Russian Far East) are, however, still too few to draw firm conclusions on the role of the BDDG as a refugium and a source for possible northward post-glacial recolonizations. In order to fill this gap, we selected a boreal/temperate herb, Lilium cernuum, and compared levels of allozyme-based genetic diversity of five populations from NE China with five populations from South Korea (home of its hypothesized refuge areas). As a complementary tool, we used the maximum entropy algorithm implemented in MaxEnt to infer the species' potential distribution for the present time, which was projected to different past climate scenarios for the Last Glacial Maximum (LGM). Permutation tests revealed that Korean populations harbored significantly higher levels of within-population genetic variation than those from NE China (expected heterozygosity = 0.173 vs. 0.095, respectively). Our results suggest that the lowered levels of genetic diversity in NE Chinese populations might be due to founder effects associated with post-glacial migration from southern regions. Congruent with genetic data, past distribution models showed higher probability of occurrence in southern ranges than in northern ones during the LGM. In addition, a positive correlation was detected between the expected heterozygosity and environmental LGM suitability. From a conservation perspective, our results further suggest that the southern populations in South Korea may be particularly worthy of protection.