Culture-acquired genetic variation in human pluripotent stem cells: Twenty years on.

Genetic changes arising in human pluripotent stem cells (hPSC) upon culture may bestow unwanted or detrimental phenotypes to cells, thus potentially impacting on the applications of hPSCs for clinical use and basic research. In the 20 years since the first report of culture-acquired genetic aberrations in hPSCs, a characteristic spectrum of recurrent aberrations has emerged. The preponderance of such aberrations implies that they provide a selective growth advantage to hPSCs upon expansion. However, understanding the consequences of culture-acquired variants for specific applications in cell therapy or research has been more elusive. The rapid progress of hPSC-based therapies to clinics is galvanizing the field to address this uncertainty and provide definitive ways both for risk assessment of variants and reducing their prevalence in culture. Here, we aim to provide a timely update on almost 20 years of research on this fascinating, but a still unresolved and concerning, phenomenon.

The replication-competent HIV reservoir is a genetically restricted, younger subset of the overall pool of HIV proviruses persisting during therapy, which is highly genetically stable over time.

Within-host HIV populations continually diversify during untreated infection, and this diversity persists within infected cell reservoirs during antiretroviral therapy (ART). Achieving a better understanding of on-ART proviral evolutionary dynamics, and a better appreciation of how the overall persisting pool of (largely genetically defective) proviruses differs from the much smaller replication-competent HIV reservoir, is critical to HIV cure efforts. We reconstructed within-host HIV evolutionary histories in blood from seven participants of the Women's Interagency HIV Study who experienced HIV seroconversion, and used these data to characterize the diversity, lineage origins, and ages of proviral env-gp120 sequences sampled longitudinally up to 12 years on ART. We also studied HIV sequences emerging from the reservoir in two participants. We observed that proviral clonality generally increased over time on ART, with clones frequently persisting long term. While on-ART proviral integration dates generally spanned the duration of untreated infection, HIV emerging in plasma was exclusively younger (i.e., dated to the years immediately pre-ART). The genetic and age distributions of distinct proviral sequences remained stable during ART in all but one participant, in whom there was evidence that younger proviruses had been preferentially eliminated after 12 years on ART. Analysis of the gag region in three participants corroborated our env-gp120-based observations, indicating that our observations are not influenced by the HIV region studied. Our results underscore the remarkable genetic stability of the distinct proviral sequences that persist in blood during ART. Our results also suggest that the replication-competent HIV reservoir is a genetically restricted, younger subset of this overall proviral pool.IMPORTANCECharacterizing the genetically diverse HIV sequences that persist in the reservoir despite antiretroviral therapy (ART) is critical to cure efforts. Our observations confirm that proviruses persisting in blood on ART, which are largely genetically defective, broadly reflect the extent of within-host HIV evolution pre-ART. Moreover, on-ART clonal expansion is not appreciably accompanied by the loss of distinct proviral lineages. In fact, on-ART proviral genetic composition remained stable in all but one participant, in whom, after 12 years on ART, proviruses dating to around near ART initiation had been preferentially eliminated. We also identified recombinant proviruses between parental sequence fragments of different ages. Though rare, such sequences suggest that reservoir cells can be superinfected with HIV from another infection era. Overall, our finding that the replication-competent reservoir in blood is a genetically restricted, younger subset of all persisting proviruses suggests that HIV cure strategies will need to eliminate a reservoir that differs in key respects from the overall proviral pool.

Assessment of genetic homogeneity of in-vitro propagated apple root stock MM 104 using ISSR and SCoT primers.

Apple is an important fruit crop that is always in demand due to its commercial and nutraceutical value. Also, the requirement for quality planting material for this fruit crop for new plantations is increasing continuously. In-vitro propagation is an alternative approach, which may help to produce genetically identical high grade planting material. In this study, for the first time, an efficient and reproducible propagation protocol has been established for apple root stock MM 104 via axillary bud. Culturing axillary buds on Murashige and Skoog apple rootstock (MM 104) resulted in better in-vitro propagation. (MS) basal medium supplemented with 3.0% (w/v) sucrose and 0.8% (w/v) agar. The axillary buds were established in MS basal medium with BA (5.0 µM), NAA (1.0 µM) and further used to establish invitro propagation protocol. Plant Growth Regulators (PGRs), BA (1.0 µM) in combination with NAA (1.0 µM) was found most efficient for shoot multiplication (100%) and produced 9.8 shoots/explants with an average shoot length of (2.4 ± cm). All the shoots produced roots in 0.1 µM IBA with a 5-day dark period. Acclimatization of in-vitro raised plantlets was obtained with vermiculite: perlite: sand: soil (2:2:1:1) resulting in 76% survival under field conditions. The study showed that the use of axillary bud is efficient for multiple-shoot production of apple rootstock (MM 104). This is the first comprehensive report on in-vitro growth of apple root stock MM 104 with an assessment of genetic stability using DNA fingerprinting profiles based on Inter Simple Sequence Repeats (ISSR) and Start Codon Targeted (SCoT). The genetic stability of in-vitro-produced plants, as determined by SCoT and ISSR primers, demonstrated genetic closeness to the mother plant.

Genetic heterogeneity of engineered Escherichia coli Nissle 1917 strains during scale-up simulation.

Advanced microbiome therapeutics have emerged as a powerful approach for the treatment of numerous diseases. While the genetic instability of genetically engineered microorganisms is a well-known challenge in the scale-up of biomanufacturing processes, it has not yet been investigated for advanced microbiome therapeutics. Here, the evolution of engineered Escherichia coli Nissle 1917 strains producing Interleukin 2 and Aldafermin were investigated in two strain backgrounds with and without the three error-prone DNA polymerases polB, dinB, and umuDC, which contribute to the mutation rate of the host strain. Whole genome short-read sequencing revealed the genetic instability of the pMUT-based production plasmid after serial passaging for approximately 150 generations using an automated platform for high-throughput microbial evolution in five independent lineages for six distinct strains. While a reduction of the number of mutations of 12%-43% could be observed after the deletion of the error-prone DNA polymerases, the interruption of production-relevant genes could not be prevented, highlighting the need for additional strategies to improve the stability of advanced microbiome therapeutics.

A growth-coupling strategy for improving the stability of terpenoid bioproduction in Escherichia coli.

BACKGROUND: Achieving cost-competitiveness remains challenging for industrial biomanufacturing. With whole-cell biocatalysis, inefficiency presents when individual cells vary in their production levels. The problem exacerbates when the basis for such production heterogeneity is heritable. Here, evolution selects for the low- and non-producers, as they have lowered/abolished the cost of bioproduction to fitness. With the scale of population expansion required for industrial bioproduction, the asymmetrical enrichment can be severe enough to compromise the performance, and hence commercial viability of the bioprocess. Clearly, addressing production heterogeneity is crucial, especially in improving the stability of bioproduction across the cell generations. In this respect, we designed a growth-coupling strategy for terpenoid bioproduction in Escherichia coli. By knocking out the native 1-deoxy-D-xylulose 5-phosphate reductoisomerase (dxr) gene and introducing the heterologous mevalonate pathway, we created a chassis that relies solely on the latter for synthesis of all terpenoids. We hypothesise that the need to sustain the biosynthesis of endogenous life-sustaining terpenoids will impose a minimum level of productivity, which concomitantly improves the bioproduction of our target terpenoid. RESULTS: Following the confirmation of lethality of a dxr knockout, we challenged the strains with a continuous plasmid-based bioproduction of linalool. The Δdxr strain achieved an improved productivity profile in the first three days post-inoculation when compared to the parental strain. Productivity of the Δdxr strain remained observable near the end of 12 days, and after a disruption in nutrient and oxygen supply in a separate run. Unlike the parental strain, the Δdxr strain did not evolve the same deleterious mutations in the mevalonate pathway, nor a viable subgroup that had lost its resistance to the antibiotic selection pressure (a plausible plasmid loss event). We believe that this divergence in the evolution trajectories is indicative of a successful growth-coupling. CONCLUSION: We have demonstrated a proof of concept of a growth-coupling strategy that improves the performance, and stability of terpenoid bioproduction across cell generations. The strategy is relatively broad in scope, and easy to implement in the background as a 'fail-safe' against a fall in productivity below the imposed minimum. We thus believe this work will find widespread utility in our collective effort towards industrial bioproduction.

A droplet vitrification cryopreservation protocol for conservation of hops (Humulus lupulus) genetic resources.

Hops (Humulus lupulus L.) is essentially used in the brewing industry as it contributes to flavor, and aroma of beer. However, the genetic diversity of hops is increasingly threatened by diseases, environmental changes, and urbanization. Cryopreservation has emerged as a pivotal strategy for safeguarding and maintaining the genetic diversity of hops. The present work presents a comprehensive study on the cryopreservation of hops, focusing on the development and optimization of a droplet vitrification based cryopreservation protocol. Shoot tips excised from one month old in vitro cultures were precultured on 0.3 M sucrose, dehydrated in a loading solution followed by treatment with PVS2 solution for different durations. Significant effect of PVS2 dehydration was observed on post-thaw survival and regeneration after cryoconservation with maximum 50% post-thaw regeneration observed in shoot tips dehydrated in PVS2 for 30 min. Genetic fidelity of the regenerated plants was confirmed using 30 ISSR markers. Reproducibility of the developed protocol was tested on seven other accessions and post thaw regeneration ranging from 43 to 70% was observed across the accessions. The present study reports a highly efficient protocol for conservation of hops germplasm. The results indicate that droplet vitrification can be used as a reliable and sustainable approach for hop genetic preservation, with high survival rates and minimal genetic alterations observed in cryopreserved samples. To the best of our knowledge, this is the first report on DV based cryopreservation of hops germplasm.

Rescue of codon-pair deoptimized respiratory syncytial virus by the emergence of genomes with very large internal deletions that complemented replication.

Recoding viral genomes by introducing numerous synonymous but suboptimal codon pairs-called codon-pair deoptimization (CPD)-provides new types of live-attenuated vaccine candidates. The large number of nucleotide changes resulting from CPD should provide genetic stability to the attenuating phenotype, but this has not been rigorously tested. Human respiratory syncytial virus in which the G and F surface glycoprotein ORFs were CPD (called Min B) was temperature-sensitive and highly restricted in vitro. When subjected to selective pressure by serial passage at increasing temperatures, Min B substantially regained expression of F and replication fitness. Whole-genome deep sequencing showed many point mutations scattered across the genome, including one combination of six linked point mutations. However, their reintroduction into Min B provided minimal rescue. Further analysis revealed viral genomes bearing very large internal deletions (LD genomes) that accumulated after only a few passages. The deletions relocated the CPD F gene to the first or second promoter-proximal gene position. LD genomes amplified de novo in Min B-infected cells were encapsidated, expressed high levels of F, and complemented Min B replication in trans This study provides insight on a variation of the adaptability of a debilitated negative-strand RNA virus, namely the generation of defective minihelper viruses to overcome its restriction. This is in contrast to the common "defective interfering particles" that interfere with the replication of the virus from which they originated. To our knowledge, defective genomes that promote rather than inhibit replication have not been reported before in RNA viruses.

Assessment of Genetic Stability in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes by Using Droplet Digital PCR.

Unintended genetic modifications that occur during the differentiation and proliferation of human induced pluripotent stem cells (hiPSCs) can lead to tumorigenicity. This is a crucial concern in the development of stem cell-based therapies to ensure the safety and efficacy of the final product. Moreover, conventional genetic stability testing methods are limited by low sensitivity, which is an issue that remains unsolved. In this study, we assessed the genetic stability of hiPSCs and hiPSC-derived cardiomyocytes using various testing methods, including karyotyping, CytoScanHD chip analysis, whole-exome sequencing, and targeted sequencing. Two specific genetic mutations in KMT2C and BCOR were selected from the 17 gene variants identified by whole-exome and targeted sequencing methods, which were validated using droplet digital PCR. The applicability of this approach to stem cell-based therapeutic products was further demonstrated with associated validation according to the International Council for Harmonisation (ICH) guidelines, including specificity, precision, robustness, and limit of detection. Our droplet digital PCR results showed high sensitivity and accuracy for quantitatively detecting gene mutations, whereas conventional qPCR could not avoid false positives. In conclusion, droplet digital PCR is a highly sensitive and precise method for assessing the expression of mutations with tumorigenic potential for the development of stem cell-based therapeutics.

Controlled Experimental Infection in Pigs with a Strain of Yersinia enterocolitica Harboring Genetic Markers for Human Pathogenicity: Colonization and Stability.

Yersinia enterocolitica (Ye) is one of the major causes of foodborne zoonosis. The BT4/O:3 bioserotype is most commonly isolated in human infections. Pigs are considered the main reservoir of Ye, and hence, understanding the dynamics of infection by this pathogen at the individual and group levels is crucial. In the present study, an experimental model was validated in Large White pigs infected with a BT4/O:3 strain. This study showed that Ye contamination in pigs may occur via the introduction of the bacteria not only by mouth but also by snout, with a colonization process consisting of three periods corresponding to three contamination statuses of pigs: P1, corresponding to the 24 h following ingestion or inhalation of Ye with the appearance of bacteria in tonsils or in feces; P2, from 2 days postinoculation (dpi), corresponding to expansion of Ye and colonization of the digestive system and extraintestinal organs associated with an IgG serological response; and P3, after 21 dpi, corresponding to regression of colonization with intermittent Ye detection in tonsils and feces. Although the inoculated strain persisted up to 56 dpi in all pigs, genetic variations with the loss of the gene yadA (a gene involved in human infection) and the emergence of two new multilocus variable-number tandem-repeat analysis (MLVA) profiles were observed in 33% of the 30 isolates studied. This experimental infection model of pigs by Ye provides new insights into the colonization steps in pigs in terms of bacterial distribution over time and bacterial genetic stability.

Human Induced Pluripotent Stem Cells: From Cell Origin, Genomic Stability, and Epigenetic Memory to Translational Medicine.

The potential of human induced pluripotent stem cells (iPSCs) to self-renew indefinitely and to differentiate virtually into any cell type in unlimited quantities makes them attractive for in vitro disease modeling, drug screening, personalized medicine, and regenerative therapies. As the genome of iPSCs thoroughly reproduces that of the somatic cells from which they are derived, they may possess genetic abnormalities, which would seriously compromise their utility and safety. Genetic aberrations could be present in donor somatic cells and then transferred during iPSC generation, or they could occur as de novo mutations during reprogramming or prolonged cell culture. Therefore, to warrant the safety of human iPSCs for clinical applications, analysis of genetic integrity, particularly during iPSC generation and differentiation, should be carried out on a regular basis. On the other hand, reprogramming of somatic cells to iPSCs requires profound modifications in the epigenetic landscape. Changes in chromatin structure by DNA methylations and histone tail modifications aim to reset the gene expression pattern of somatic cells to facilitate and establish self-renewal and pluripotency. However, residual epigenetic memory influences the iPSC phenotype, which may affect their application in disease therapeutics. The present review discusses the somatic cell origin, genetic stability, and epigenetic memory of iPSCs and their impact on basic and translational research.

A risk-based approach for cell line development, manufacturing and characterization of genetically engineered, induced pluripotent stem cell-derived allogeneic cell therapies.

Advances in cellular reprogramming and gene-editing approaches have opened up the potential for a new class of ex vivo cell therapies based on genetically engineered, induced pluripotent stem cell (iPSC)-derived allogeneic cells. While these new therapies share some similarities with their primary cell-derived autologous and allogeneic cell therapy predecessors, key differences exist in the processes used for generating genetically engineered, iPSC-derived allogeneic therapies. Specifically, in iPSC-derived allogeneic therapies, donor selection and gene-editing are performed once over the lifetime of the product as opposed to as part of the manufacturing of each product batch. The introduction of a well-characterized, fully modified, clonally derived master cell bank reduces risks that have been inherent to primary-cell derived autologous and allogeneic therapies. Current regulatory guidance, which was largely developed based on the learnings gained from earlier generation therapies, leaves open questions around considerations for donor eligibility, starting materials and critical components, cell banking and genetic stability. Here, a risk-based approach is proposed to address these considerations, while regulatory guidance continues to evolve.

Refactoring the architecture of a polyketide gene cluster enhances docosahexaenoic acid production in Yarrowia lipolytica through improved expression and genetic stability.

BACKGROUND: Long-chain polyunsaturated fatty acids (LC-PUFAs), such as docosahexaenoic acid (DHA), are essential for human health and have been widely used in the food and pharmaceutical industries. However, the limited availability of natural sources, such as oily fish, has led to the pursuit of microbial production as a promising alternative. Yarrowia lipolytica can produce various PUFAs via genetic modification. A recent study upgraded Y. lipolytica for DHA production by expressing a four-gene cluster encoding a myxobacterial PKS-like PUFA synthase, reducing the demand for redox power. However, the genetic architecture of gene expression in Y. lipolytica is complex and involves various control elements, offering space for additional improvement of DHA production. This study was designed to optimize the expression of the PUFA cluster using a modular cloning approach. RESULTS: Expression of the monocistronic cluster with each gene under the control of the constitutive TEF promoter led to low-level DHA production. By using the minLEU2 promoter instead and incorporating additional upstream activating UAS1B4 sequences, 5' promoter introns, and intergenic spacers, DHA production was increased by 16-fold. The producers remained stable over 185 h of cultivation. Beneficially, the different genetic control elements acted synergistically: UAS1B elements generally increased expression, while the intron caused gene-specific effects. Mutants with UAS1B16 sequences within 2-8 kb distance, however, were found to be genetically unstable, which limited production performance over time, suggesting the avoidance of long repetitive sequence blocks in synthetic multigene clusters and careful monitoring of genetic stability in producing strains. CONCLUSIONS: Overall, the results demonstrate the effectiveness of synthetic heterologous gene clusters to drive DHA production in Y. lipolytica. The combinatorial exploration of different genetic control elements allowed the optimization of DHA production. These findings have important implications for developing Y. lipolytica strains for the industrial-scale production of valuable polyunsaturated fatty acids.

Physiochemical and Microbial Analysis of Tibetan Yak Milk Yogurt in Comparison to Locally Available Yogurt.

Yak yogurt, which is rich in microorganisms, is a naturally fermented dairy product prepared with ancient and modern techniques by Chinese herdsmen in the Qinghai-Tibet Plateau. The objective of this research was to assess the impact of Lactobacillus bulgaricus and Streptococcus thermophilus starter cultures on the quality and shelf life of yak yogurt, as well as the genetic stability across multiple generations, in comparison to commercially available plain yogurt and peach oat flavor yogurt. Following that, the samples were evenly divided into four treatment groups denoted as T1 (treatment 1), T2, T3, and T4, with each group employing a distinct source of yogurt formulation. T1 included L. bulgaricus, T2 comprised S. thermophilus, T3 consisted of plain yogurt, and T4 represented peach oat yogurt flavor. The findings indicate that T1 yogurt consistently presents a lower pH and higher acidity compared to the other three yogurt types throughout the entire generation process. Moreover, the fat content in all generations of the four yogurt types exceeds the national standard of 3.1 g/100 g, while the total solid content shows a tendency to stabilize across generations. The protein content varies significantly among each generation, with T1 and T4 yogurt indicating higher levels compared to the T2 and T3 yogurt groups. In terms of overall quality, T1 and T4 yogurt are superior to T2 and T3 yogurt, with T1 yogurt being the highest in quality among all groups. The findings revealed that the inclusion of L. bulgaricus led to enhanced flavor, texture, and genetic stability in yak yogurt. This study will serve as a valuable source of data, support, and methodology for the development and screening of compound starters to be utilized in milk fermentation in future research and applications.

Genomic evidence for stability of the Bacillus Calmette-Guérin (BCG) vaccine strain (Pasteur 1173P2) from different batches in Iran.

AIMS: Investigate the genetic stability of the BCG vaccine produced in Iran from different batches compared to the reference strain. METHODS AND RESULTS: We comparatively analyzed the whole genome sequences of the vaccine batches from different years. Eleven vials of different batches from 2010, 2018, and 2019 were included. Complete genome analyses revealed no difference between the old (2010) and new (2018 and 2019) vaccine batches. Additionally, minor genetic changes include five single nucleotide polymorphisms (SNPs) and insertions/deletions (indels) were observed compared to the BCG Pasteur 1173P2 reference strain, which were shared among all batches. Besides, the batches were identical to the reference strain in terms of antibiotic resistance genes, prophage sequences, and clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated (Cas) systems. CONCLUSIONS: High genetic stability of the BCG vaccine used in the national immunization program was confirmed, which indicates the optimal conditions in the vaccine production process. SIGNIFICANCE AND IMPACT OF THE STUDY: Genetic differences within and between vaccine strains have been declared as one of the main parameters related to the BCG vaccine variable protective efficacy. No study has been done to investigate the genetic variations of the vaccine batches at the single-base level.

Amber codon is genetically unstable in generation of premature termination codon (PTC)-harbouring Foot-and-mouth disease virus (FMDV) via genetic code expansion.

The foot-and-mouth disease virus (FMDV) is the causative agent of FMD, a highly infectious and devastating viral disease of domestic and wild cloven-hoofed animals. FMD affects livestock and animal products' national and international trade, causing severe economic losses and social consequences. Currently, inactivated vaccines play a vital role in FMD control, but they have several limitations. The genetic code expansion technology provides powerful strategies for generating premature termination codon (PTC)-harbouring virus as a live but replication-incompetent viral vaccine. However, this technology has not been explored for the design and development of new FMD vaccines. In this study, we first expanded the genetic code of the FMDV genome via a transgenic cell line containing an orthogonal translation machinery. We demonstrated that the transgenic cells stably integrated the orthogonal pyltRNA/pylRS pair into the genome and enabled efficient, homogeneous incorporation of unnatural amino acids into target proteins in mammalian cells. Next, we constructed 129 single-PTC FMDV mutants and four dual-PTC FMDV mutants after considering the tolerance, location, and potential functions of those mutated sites. Amber stop codons individually substituted the selected amino acid codons in four viral proteins (3D, L, VP1, and VP4) of FMDV. We successfully rescued PTC-FMDV mutants, but the amber codon unexpectedly showed a highly degree of mutation rate during PTC-FMDV packaging and replication. Our findings highlight that the genetic code expansion technology for the generation of PTC-FMD vaccines needs to be further improved and that the genetic stability of amber codons during the packaging and replication of FMDV is a concern.

Assessment of genetic stability on in vitro and ex vitro plants of Ficus carica var. black jack using ISSR and DAMD markers.

BACKGROUND: Clonal propagation is one of the attributes of plant tissue culture. Therefore, analysis of genetic stability among the in vitro cultured plants is a crucial step. It helps to signify the clonal propagation of the micropropagated plants. Regenerated Ficus carica var. Black Jack plantlets were established using woody plant medium supplemented with 20 µM 6-Benzylaminopurine and 8 µM Indole-3-acetic acid under different light treatments such as normal fluorescent white light (60 µmol m-2 s-1), and four different LED spectra, white (400-700 nm), blue (440 nm), red (660 nm) and blue + red (440 nm + 660 nm). Genetic stability analysis was performed on the in vitro and ex vitro plants of Ficus carica var. Black Jack. METHODS AND RESULTS: Ten primers of each, ISSR and DAMD molecular markers, were used to assess the genetic stability of the eight samples of Ficus carica var. Black Jack. ISSR markers showed 97.87% of monomorphism whereas DAMD markers showed 100% monomorphism. Polymorphism of 2.13% was observed for the UBC840 ISSR-DNA primer which was negated under the genetic similarity index analysis for the eight samples. The findings of this study revealed that ISSR and DAMD markers are efficient in determining the polymorphism and monomorphism percentage among the in vitro and ex vitro samples of Ficus carica var. Black Jack. CONCLUSION: Monomorphism of 100% obtained using DAMD markers and more than 95% of monomorphism obtained using ISSR markers indicate that the regenerated plants are significantly genetically stable. These molecular markers can be used to test the genetic stability of in vitro regenerated plants. It is recommended that genetic stability analysis should be performed for long-term maintenance of such micropropagated plants.

Food-Grade Expression and Characterization of a Dextranase from Chaetomium gracile Suitable for Sugarcane Juice Clarification.

The microbial production of dextranase using cheap carbon sources is beneficial to solve the economic loss caused by the accumulation of dextran in syrup. A food-grade microbial cell factory was constructed by introducing the dextranase encoding gene DEX from Chaetomium gracile to the chromosome of Bacillus subtilis, and the antibiotic resistance marker gene was subsequently deleted via the Cre/loxP strategy. The dual-promoter system with a sequentially arranged constitutive P43 promoter resulted in an 85 % increase in DEX expression. Under the optimal fermentation conditions of 10 g/L maltose, 15 g/L casein, 1 g/L Na2 HPO4 , 1 g/L FeSO4 and 8 g/L NaCl, DEX activity was increased from 2.625 to 64.34 U/mL. Recombinant DEX was purified 5.98-fold with a recovery ratio of 26.67 % and specific activity of 3935.02 U/mg. Enzyme activity was optimal at 55 °C and pH 5.0 and remained 80.34 % and 71.36 % of the initial activity at 55 °C and pH 4.0 after 60 min, respectively. The enzyme possessed high activity in the presence of Co2+ , while Ag+ showed the strongest inhibition ability. The optimal substrate was 20 g/L dextran T-2000. The findings could facilitate the low-cost, large-scale production of food-grade DEX for use in the sugar industry.

Assessment of Genetic Stability During Serial In Vitro Passage and In Vivo Carriage.

In this study, our objective was to evaluate the genetic stability of foodborne bacterial pathogens during serial passage in vitro and persistent in vivo carriage. Six strains of Listeria, Campylobacter, Escherichia, Salmonella, and Vibrio were serially passaged 20 times. Three colonies were picked for whole-genome sequencing (WGS) from passes P0, P5, P10, P15, and P20. In addition, isolates of Salmonella and Escherichia from three patients with persistent infections were sequenced. Genetic stability was evaluated in terms of variations detected in high-quality single-nucleotide polymorphism (hqSNP), core genome multilocus sequence typing (cgMLST), seven-gene MLST, and determinants encoding serotype, antimicrobial resistance (AMR), and virulence. During serial passage, increasing diversity was observed in Listeria, Salmonella, and Vibrio as measured by hqSNPs (from median of 0 SNPs to median of 3-5 SNPs, depending on the organism) and to a lesser extent with cgMLST (from median of 0 alleles to median of 0-5 alleles), while Escherichia and Campylobacter genomes showed minimal variation. The serotype, AMR, and virulence markers remained stable in all organisms. Isolates from persistent infections lasting up to 10 weeks remained genetically stable. However, isolates from a persistent Salmonella enterica ser. Montevideo infection spanning 9 years showed early heterogeneity leading to the emergence of one predominant genotype that continued to evolve over the years, including gains and losses of AMR markers. While the hqSNP and cgMLST variation observed during the serial passage was minimal, culture passages should be limited to as few times as possible before WGS. Our WGS data show that in vivo carriage lasting for a few weeks did not appear to alter the genotype. Longer persistent infections spanning for years, particularly in the presence of selective pressure, may cause changes in the genotype making it challenging to differentiate persistent infections from reinfections.

Rapid Production and Genetic Stability of Human Mesenchymal Progenitor Cells Derived from Human Somatic Cell Nuclear Transfer-Derived Pluripotent Stem Cells.

Pluripotent stem cell-derived mesenchymal progenitor cells (PSC-MPCs) are primarily derived through two main methods: three-dimensional (3D) embryoid body-platform (EB formation) and the 2D direct differentiation method. We recently established somatic cell nuclear transfer (SCNT)-PSC lines and showed their stemness. In the present study, we produced SCNT-PSC-MPCs using a novel direct differentiation method, and the characteristics, gene expression, and genetic stability of these MPCs were compared with those derived through EB formation. The recovery and purification of SCNT-PSC-Direct-MPCs were significantly accelerated compared to those of the SCNT-PSC-EB-MPCs, but both types of MPCs expressed typical surface markers and exhibited similar proliferation and differentiation potentials. Additionally, the analysis of gene expression patterns using microarrays showed very similar patterns. Moreover, array CGH analysis showed that both SCNT-PSC-Direct-MPCs and SCNT-PSC-EB-MPCs exhibited no significant differences in copy number variation (CNV) or single-nucleotide polymorphism (SNP) frequency. These results indicate that SCNT-PSC-Direct-MPCs exhibited high genetic stability even after rapid differentiation into MPCs, and the rate at which directly derived MPCs reached a sufficient number was higher than that of MPCs derived through the EB method. Therefore, we suggest that the direct method of differentiating MPCs from SCNT-PSCs can improve the efficacy of SCNT-PSCs applied to allogeneic transplantation.

RAPD, ISSR, and SCoT markers based genetic stability assessment of micropropagated Dendrobium fimbriatum Lindl. var. oculatum Hk. f.- an important endangered orchid.

Dendrobium fimbriatum is an ornamental and medicinal orchid listed in the Red data book of IUCN. Phytohormones' effect on the in vitro regeneration of the orchid was studied using Mitra medium supplemented with different growth regulators. KN produced effective shoot formation when present alone or in combination with IBA or NAA. The shooting was gradually increased when KN concentration was increased from 0.8 to 4.8 mg L-1, but the opposite response was observed with BAP at higher concentration (4.8 mg L-1). IBA either in combination with BAP or KN promoted effective root development and multiplication. Micropropagated orchids grown in the basal medium devoid of any phytohormone showed 100% monomorphism, while low genetic polymorphism of 1.52% (RAPD-Random Amplification of Polymorphic DNA), 1.19% (ISSR-Inter Simple Sequence Repeat) and 3.97% (SCoT-Start Codon Targeted) was exhibited among the regenerants propagated in the hormone enriched medium. UPGMA (Unweighted pair group method using arithmetic averages) dendrograms showed the grouping of mother plant (MP) with the in vitro regenerants. The principal coordinate analysis (PCoA) further confirmed the clustering patterns as determined by the cluster analysis. The study reported for the first time the successful in vitro propagation of Dendrobium fimbriatum and their genetic stability assessment using molecular markers.