Essential cellular modules for the proliferation of the primitive cell

Bacteria appeared early in the evolution of cellular life on planet Earth, and therefore the universally essential genes or biological pathways found across bacterial domains may represent fundamental genetic or cellular systems used in early life. The essential genes and the minimal gene set required to support bacterial life have recently been experimentally and computationally identified. It is, however,still hard to estimate the ancient genes present in primitive cells compared to the essential genes in contemporary bacteria, because we do not know how ancestral primitive cells lived and proliferated, and therefore cannot directly evaluate the essentiality of the genes in ancestral primitive cells. The cell wall is normally essential for bacterial proliferation and cellular division of walled bacterial cells is normally highly controlled by the essential FtsZ cell division machinery. But, bacteria are capable of reverting to their cell wall deficient ancestral form, called the ＂L-form＂. Unlike ＂normal＂ cells, L-forms divide by a simple physical mechanism based on the effects of membrane dynamics, suggesting a mode of primitive proliferation before the appearance of the cell wall. In this review, we summarize the experimental and computational investigations of minimal gene sets and discuss the minimal cellular modules required to support the proliferation of primitive cells, based on L-form proliferation.

Biogeographical note on Antarctic microforae: Endemism and cosmopolitanism

This study deals with the biogeography of Antarctic microflora （Antarctica acts as best model to study microbial biogeography） such as cyanobacteria and selected halophiles with special emphasis on Halomonas variabilis and Bacillus licheniformis.Halophiles are known to be resistant not only to salt stress,but also to extreme temperature,pressure,and aridity and they are capable of surviving in harsh environments such as polar regions,deep-sea habitats,and deserts.Many microbes are known to be resistant to hostile environmental conditions,and are capable of surviving in harsh environments.Our group has isolated 444 strains belonging to 28 genera of halophiles from various environments around the world.The 16S rRNA gene sequences revealed that many of the isolated strains from geographically distant habitats having different environmental conditions,were closely related to each other,with some strains possessing 100％ identical sequences.Organisms possessing survival mechanism such as spore formation are usually ubiquitous.The genus Halomonas is represented by potentially endemic strains and the ubiquitous H.variabilis,while spore-forming B.licheniformis showed cosmopolitan distribution.One potentially endemic （moderate endemicity that is regional and/or continental distribution） strain was reported from Syowa station,East Antarctica,and Mario Zucchelli station,West Antarctica,which are geographically separated by 3000 km.Moreover,15 strains having 100％ similarity with B.licheniformis were considered cosmopolitans.The results of this work provide support for the middle-ground model that some microbes have moderate endemicity and others have cosmopolitan distribution.These results will contribute to a greater understanding of microbial biogeography with special emphasis on Antarctica.

Do not curse the darkness of the spinal cord,light TDP-43

Cytoplasmic inc lus ions containing the transactivation response element(TAR)DNAbinding protein-43(TDP-43)aggregates are hallmarks of neurodegenerative disorders,such as amyotrophic lateral sclerosis(ALS)and frontotemporal dementia(Arai et al.,2006;Neumann et al.,2006).Despite the well-recognized correlation between TDP-43 aggregation and neuronal degeneration,whether this relationship is causal has remained unclear.

Nine requirements for the origin of Earth’s life:Not at the hydrothermal vent, but in a nuclear geyser system

The origin of life on Earth remains enigmatic with diverse models and debates.Here we discuss essential requirements for the first emergence of life on our planet and propose the following nine requirements:(1)an energy source(ionizing radiation and thermal energy);(2)a supply of nutrients(P.K.REE.etc.);(3)a supply of life-constituting major elements;(4)a high concentration of reduced gases such as CH4,HCN and NH3;(5)dry-wet cycles to create membranes and polymerize RNA;(6)a non-toxic aqueous environment;(7)Na-poor water;(8)highly diversified environments,and(9)cyclic conditions,such as dayto-night,hot-to-cold etc.Based on these nine requirements,we evaluate previously proposed locations for the origin of Earth’s life,including:(1)Darwin’s"warm little pond",leading to a"prebiotic soup"for life;(2)panspermia or Neo-panspermia(succession model of panspermia);(3)transportation from/through Mars;(4)a deepsea hydrothermal system;(5)an on-land subduct ion-zone hot spring,and(6)a geyser systems driven by a natural nuclear reactor.We conclude that location(6)is the most ideal candidate for the o rigin point for Earth’s life because of its efficiency in continuously supplying both the energy and the necessary materials for life,thereby maintaining the essential"cradle"for its initial development.We also emphasize that falsifiable working hypothesis provides an important tool to evaluate one of the biggest mysteries of the universe-the origin of life.

Dps Is a Stationary Phase-Specific Protein of <i>Escherichia coli</i>Nucleoid

Bacterial genomic DNA is highly organized into one or few compacted bodies known as nucleoid, which is composed of DNA, RNA and several DNA-binding proteins. These DNA-binding proteins require essential alterations in their expression during stationary phase of growth in order to re-spond to stressful environmental conditions. Dps (DNA-binding protein from starved cells) is one of such DNA-binding proteins, which accumulates most when E. coli cells reach to the stationary phase. Here, we have characterized Dps protein under various growth phases. Immunofluorescent microscopic observation reveals that Dps plays a key role in final round of genome compaction during the stationary phase. Similar results are also obtained by Western immunoblot analysis, after quantification of Dps protein from the exponential phase and early stationary phase nucleoid bound fractions, separated by sucrose density gradient centrifugation. Our results support the conclusion that Dps occupies more than half of the stationary phase nucleoid in E. coli.

应用线粒体DNA D-loop区遗传多样性分析云南4个少数民族的遗传关系

对傣、佤、拉祜和藏族４个群体的９９名个体ｍｔＤＮＡ非编码区（Ｄ－ｌｏｏｐ）高变区I１６０４８～１６５６９及１～４１的５６３ｂｐ片段进行序列分析。计算了核酸多态度，并用Ｎｅｉｇｈｂｏｒ－Ｊｏｉｎｉｎｇ 法构建系统进化树，在进化树中，９９个ｍｔＤＮＡ序列分别聚在４个群中。所有在ＣＯ Ⅱ ／ｔＲＡＮ Ｌｙｓ 基因间序列存在９ｂｐ缺失的个体均聚在Ｃ１群中，Ｃ２群由１个佤族个体和４个藏族个体组成，Ｃ３群中除２个藏族个体外均为其他３个民族个体，４个群体的大部分个体聚在Ｃ４群。根据核酸多态度计算的净遗传距离重建的进化树显示，傣族、佤族和拉祜族的亲缘关系较接近，与藏族距离较远。结果表明遗传距离与他们的地理分布是非常一致的。而拉祜族与相传同为氐羌后裔并有相近语言的藏族跗距离却较远，这一结果提示这两个民族可能具有不同的起源。

Prevascularized Micro‑/Nano‑Sized Spheroid/Bead Aggregates for Vascular Tissue Engineering

Efficient strategies to promote microvascularization in vascular tissue engineering,a central priority in regenerative medicine,are still scarce;nano-and micro-sized aggregates and spheres or beads harboring primitive microvascular beds are promising methods in vascular tissue engineering.Capillaries are the smallest type and in numerous blood vessels,which are distributed densely in cardiovascular system.To mimic this microvascular network,specific cell components and proangiogenic factors are required.Herein,advanced biofabrication methods in microvascular engineering,including extrusion-based and droplet-based bioprinting,Kenzan,and biogripper approaches,are deliberated with emphasis on the newest works in prevascular nano-and micro-sized aggregates and microspheres/microbeads.

Growth phase dependent changes in the structure and protein composition of nucleoid in Escherichia coli

The genomic DNA of bacteria is highly compacted in a single or a few bodies known as nucleoids. Here, we have isolated Escherichia coli nucleoid by sucrose density gradient centrifugation. The sedimentation rates, structures as well as protein/DNA composition of isolated nucleoids were then compared under various growth phases. The nucleoid structures were found to undergo changes during the cell growth; i. e., the nucleoid structure in the stationary phase was more tightly compacted than that in the exponential phase. In addition to factor for inversion stimulation(Fis), histone-like nucleoid structuring protein(H-NS), heat-unstable nucleoid protein(HU) and integration host factor(IHF) here we have identified, three new candidates of E. coli nucleoid, namely DNA-binding protein from starved cells(Dps), host factor for phage Qβ(Hfq) and suppressor of td- phenotype A(Stp A). Our results reveal that the major components of exponential phase nucleoid are Fis, HU, H-NS, Stp A and Hfq, while Dps occupies more than half of the stationary phase nucleoid. It has been known for a while that Dps is the main nucleoid-associated protein at stationary phase. From these results and the prevailing information, we propose a model for growth phase dependent changes in the structure and protein composition of nucleoid in E. coli.

Two Tightly Linked Genes at the hsal Locus Cause Both F1 and F2 Hybrid Sterility in Rice

Molecular mechanisms of hybrid breakdown associated with sterility (F2 sterility) are poorly understood as compared with those of F1 hybrid sterility. Previously, we characterized three unlinked epistatic loci, hybrid sterility-a1 (hsa1), hsa2, and hsa3, responsible for the F2 sterility in a cross between Oryza sativa ssp. indica and japonica. In this study, we identified that the hsa1 locus contains two interacting genes, HSA1a and HSA1b, within a 30-kb region. HSA1a-j (japonica allele) encodes a highly conserved plant-specific domain of unknown function protein (DUF1618), whereasthe indica allele (HSA1a-is) has two deletion mutations that cause disruption of domain structure. The second gene, HSA1b-is, encodes an uncharacterized proteinwith some similarity to a nucleotide-binding protein. Homozygous introgression of indica HSA1a-is-HSA1b-is alleles into japonica showed female gamete abortion at an early mitotic stage. The fact that the recombinant haplotype HSA1a-j-HSA1b-is caused semi-sterility in the heterozygous state with the HSA1a-is-HSA1b-is haplotype suggests that variation in the hsa1 locus is a possible cause of the wide-spectrum sterility barriers seen in F1 hybrids and successive generations in rice. We propose a simple genetic model to explain how a single causal mechanism can drive both F1 and F2 hybrid sterility.

A Multifunctional Modulator Coordinates Nuclear Transcription and Plastid Metabolism and Proliferation

The photosynthetic plastid(chloroplast)arose more than one billion years ago,when a free-living cyanobacterium became a permanent endosymbiont and remodeled as an organelle in an ancient eukaryotic algal cell(Archibald,2015).Seed plants further evolved mechanisms of plastid differentiation,whereby several types of non-green non-photosynthetic plastids develop in addition to chloroplasts,including amyloplasts,which accumulate starch granules,and chromoplasts,which deposit carotenoids(Pyke,2010,Sun et al.,2018).Plastid differentiation enables multicellular plants to assign specialized roles to different tissues upon cellular differentiation and/or in response to developmental and environmental changes.