Recently, in vitro synthetic biology has been actively engaged in the reconstitution of artificial systems implemented with life-like characteristics to understand the principle and origins of life. One of the most important characteristics of life is self-reproducibility, which is originated from the self-regeneration ability of the gene replication and expression system (i.e., central dogma). In this review, we summarize recent progress in in vitro reconstitution of biological functions that constitute central dogma, DNA replication, transcription, and translation.

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The minimal cell is the simplest bacterium designed and engineered to have almost only essential genes. It is based on a bacterium Mycoplasma, and is designed to have only 473 genes (531 kbp), reducing from 901 genes (1,079 kbp) of the wild strain. This is expected to greatly advance our understanding of the basics of life, is a major step toward the creation of artificial life, and must be a milestone in microbiology. This mini review summarizes the procedures for creating the minimal cell and examples of its use.

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To evaluate bacterial cellular polyamine distributions as a chemotaxonomic marker for classification and as a growth factor for extremophilic environments, acid-extracted polyamines from new available members including various extremophiles belonging to the emended phylum Proteobacteria including the classes, Alphaproteobacteria (164 strains), Betaproteobacteria (35), Hydrogenophilalia (3), Gammaproteobacteria (113), Acidithiobacillia (11) and Zetaproteobacteria (2), and the newly validated phyla Epsilonbacteraeota (22), Bdellovibrionota (2) and Myxococcota (1) separated from the former phylum Proteobacteria, were analyzed by HPLC and HPGC-MS. Distribution of homospermidine, spermidine and aminopropylcadaverine were found within Alphaproteobacteria. 2-Hydroxyputrescine and 2-hydroxyspermidine were found within Betaproteobacteria and Hydrogenophilalia. Occurrence of 1,3-diaminopropane and norspermidine was specific to certain members of Gammaproteobacteria. Only spermidine was detected as a major polyamine in Acidithiobacillia and Zetaproteobacteria. Spermidine was a major polyamine in Epsilonbacteraeota. Spermidine-dominant or homospermidine-dominant species were found within Bdellovibrionota and Myxococcota. Thermophilic species have a high level of spermine in the four phyla. No clear polyamine profile patterns were observed in acidophiles, alkaliphiles, psychrophiles and halophiles of the four phyla.

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The heart creates positive and negative pressure in a regular rhythm to pump blood. The cardiac chambers seen in vertebrates are an advanced pump design. Many species, such as the hagfish, still have accessory pumps, but they are considered vestigial. Additionally, the processes by which the circulatory system develops in vertebrates, including heart development, are largely unknown. In this study, we examined the heart of hagfish (Eptatretus burgeri) using histological analysis. In E. burgeri, three types of hearts were observed: branchial, cardinal, and portal. Photomicrographs showed that there are many empty spaces in all three types. These hearts pump blood in and out of the sponge to absorb and discharge water. The cardinal heart near the brain in E. burgeri may be primitive because its cell structure is similar to that of skeletal muscle.

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