Waddington’s Landscapes in the Bacterial World

Conrad Waddington’s epigenetic landscape, a visual metaphor for the development of multicellular organisms, is appropriate to depict the formation of phenotypic variants of bacterial cells. Examples of bacterial differentiation that result in morphological change have been known for decades. In addition, bacterial populations contain phenotypic cell variants that lack morphological change, and the advent of fluorescent protein technology and single-cell analysis has unveiled scores of examples. Cell-specific gene expression patterns can have a random origin or arise as a programmed event. When phenotypic cell-to-cell differences are heritable, bacterial lineages are formed. The mechanisms that transmit epigenetic states to daughter cells can have strikingly different levels of complexity, from the propagation of simple feedback loops to the formation of complex DNA methylation patterns. Game theory predicts that phenotypic heterogeneity can facilitate bacterial adaptation to hostile or unpredictable environments, serving either as a division of labor or as a bet hedging that anticipates future challenges. Experimental observation confirms the existence of both types of strategies in the bacterial world.

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Comprehensive analysis of single cell ATAC-seq data with SnapATAC

Nature Communications ◽

10.1038/s41467-021-21583-9 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Rongxin Fang ◽

Sebastian Preissl ◽

Yang Li ◽

Xiaomeng Hou ◽

Jacinta Lucero ◽

...

Keyword(s):

Single Cell ◽

Single Cell Analysis ◽

Expression Patterns ◽

Regulatory Elements ◽

Cellular Heterogeneity ◽

Specific Gene ◽

Open Chromatin ◽

Cell Type ◽

Process Data ◽

Cell Type Specific

AbstractIdentification of the cis-regulatory elements controlling cell-type specific gene expression patterns is essential for understanding the origin of cellular diversity. Conventional assays to map regulatory elements via open chromatin analysis of primary tissues is hindered by sample heterogeneity. Single cell analysis of accessible chromatin (scATAC-seq) can overcome this limitation. However, the high-level noise of each single cell profile and the large volume of data pose unique computational challenges. Here, we introduce SnapATAC, a software package for analyzing scATAC-seq datasets. SnapATAC dissects cellular heterogeneity in an unbiased manner and map the trajectories of cellular states. Using the Nyström method, SnapATAC can process data from up to a million cells. Furthermore, SnapATAC incorporates existing tools into a comprehensive package for analyzing single cell ATAC-seq dataset. As demonstration of its utility, SnapATAC is applied to 55,592 single-nucleus ATAC-seq profiles from the mouse secondary motor cortex. The analysis reveals ~370,000 candidate regulatory elements in 31 distinct cell populations in this brain region and inferred candidate cell-type specific transcriptional regulators.

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Global Analysis of Cell Type-Specific Gene Expression

Comparative and Functional Genomics ◽

10.1002/cfg.281 ◽

2003 ◽

Vol 4 (2) ◽

pp. 208-215 ◽

Cited By ~ 16

Author(s):

David W. Galbraith

Keyword(s):

Gene Expression ◽

Fluorescent Protein ◽

Global Analysis ◽

Expression Patterns ◽

Three Dimensional ◽

Global Gene Expression ◽

Cell Types ◽

Reasonable Assumption ◽

Specific Gene ◽

Different Cell Types

The tissues and organs of multicellular eukaryotes are frequently observed to comprise complex three-dimensional interspersions of different cell types. It is a reasonable assumption that different global patterns of gene expression are found within these different cell types. This review outlines general experimental strategies designed to characterize these global gene expression patterns, based on a combination of methods of transgenic fluorescent protein (FP) expression and targeting, of flow cytometry and sorting and of high-throughput gene expression analysis.

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Modifying TIMER to generate a slow-folding DsRed derivative for optimal use in quickly-dividing bacteria

PLoS Pathogens ◽

10.1371/journal.ppat.1009284 ◽

2021 ◽

Vol 17 (7) ◽

pp. e1009284

Author(s):

Pavan Patel ◽

Brendan J. O’Hara ◽

Emily Aunins ◽

Kimberly M. Davis

Keyword(s):

Stationary Phase ◽

Yersinia Pseudotuberculosis ◽

Fluorescent Protein ◽

Bacterial Species ◽

Bacterial Cells ◽

Deep Tissue ◽

Bacterial Populations ◽

Novel Variant ◽

Slow Growing ◽

Host Tissues

It is now well appreciated that members of pathogenic bacterial populations exhibit heterogeneity in growth rates and metabolic activity, and it is known this can impact the ability to eliminate all members of the bacterial population during antibiotic treatment. It remains unclear which pathways promote slowed bacterial growth within host tissues, primarily because it has been difficult to identify and isolate slow growing bacteria from host tissues for downstream analyses. To overcome this limitation, we have developed a novel variant of TIMER, a slow-folding fluorescent protein, named DsRed42, to identify subsets of slowly dividing bacteria within host tissues. The original TIMER folds too slowly for fluorescence accumulation in quickly replicating bacterial species (Escherichia coli, Yersinia pseudotuberculosis), however DsRed42 accumulates red fluorescence in late stationary phase cultures of E. coli and Y. pseudotuberculosis. We show DsRed42 signal also accumulates during exposure to sources of nitric oxide (NO), suggesting DsRed42 signal detects growth-arrested bacterial cells. In a mouse model of Y. pseudotuberculosis deep tissue infection, DsRed42 signal was detected, and primarily accumulates in bacteria expressing markers of stationary phase growth. There was no significant overlap between DsRed42 signal and NO-exposed subpopulations of bacteria within host tissues, suggesting NO stress was transient, allowing bacteria to recover from this stress and resume replication. This novel DsRed42 variant represents a tool that will enable additional studies of slow-growing subpopulations of bacteria, specifically within bacterial species that quickly divide.

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HMEJ-mediated efficient site-specific gene integration in chicken cells

Journal of Biological Engineering ◽

10.1186/s13036-019-0217-9 ◽

2019 ◽

Vol 13 (1) ◽

Cited By ~ 2

Author(s):

Long Xie ◽

Juanjuan Sun ◽

Lifen Mo ◽

Tianpeng Xu ◽

Qaisar Shahzad ◽

...

Keyword(s):

Fluorescent Protein ◽

Expression Patterns ◽

Primordial Germ Cells ◽

Great Promise ◽

Specific Gene ◽

Transgenic Chicken ◽

Site Specific ◽

Chicken Cell ◽

Chicken Oviduct ◽

Gene Integration

Abstract Background The production of transgenic chicken cells holds great promise for several diverse areas, including developmental biology and biomedical research. To this end, site-specific gene integration has been an attractive strategy for generating transgenic chicken cell lines and has been successfully adopted for inserting desired genes and regulating specific gene expression patterns. However, optimization of this method is essential for improving the efficiency of genome modification in this species. Results Here we compare gene knock-in methods based on homology-independent targeted integration (HITI), homology-directed repair (HDR) and homology mediated end joining (HMEJ) coupled with a clustered regularly interspaced short palindromic repeat associated protein 9 (CRISPR/Cas9) gene editing system in chicken DF-1 cells and primordial germ cells (PGCs). HMEJ was found to be a robust and efficient method for gene knock-in in chicken PGCs. Using this method, we successfully labeled the germ cell specific gene DAZL and the pluripotency-related gene Pou5f3 in chicken PGCs through the insertion of a fluorescent protein in the frame at the 3′ end of the gene, allowing us to track cell migration in the embryonic gonad. HMEJ strategy was also successfully used in Ovalbumin, which accounts for more than 60% of proteins in chicken eggs, suggested its good promise for the mass production of protein with pharmaceutical importance using the chicken oviduct system. Conclusions Taken together, these results demonstrate that HMEJ efficiently mediates site-specific gene integration in chicken PGCs, which holds great potential for the biopharmaceutical engineering of chicken cells.

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Faculty Opinions recommendation of RNA visualization in live bacterial cells using fluorescent protein complementation.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718145205.793485382 ◽

2013 ◽

Author(s):

Luc Jaeger

Keyword(s):

Fluorescent Protein ◽

Bacterial Cells ◽

Protein Complementation ◽

Live Bacterial Cells

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A Global Vista of the Epigenomic State of the Mouse Submandibular Gland

Journal of Dental Research ◽

10.1177/00220345211012000 ◽

2021 ◽

pp. 002203452110120

Author(s):

C. Gluck ◽

S. Min ◽

A. Oyelakin ◽

M. Che ◽

E. Horeth ◽

...

Keyword(s):

Gene Expression ◽

Transcriptional Control ◽

Expression Patterns ◽

Global Gene Expression ◽

Regulatory Elements ◽

Specific Gene ◽

Submandibular Salivary Gland ◽

Data Sets ◽

Control Mechanisms ◽

Chromatin Immunoprecipitation Sequencing

The parotid, submandibular, and sublingual glands represent a trio of oral secretory glands whose primary function is to produce saliva, facilitate digestion of food, provide protection against microbes, and maintain oral health. While recent studies have begun to shed light on the global gene expression patterns and profiles of salivary glands, particularly those of mice, relatively little is known about the location and identity of transcriptional control elements. Here we have established the epigenomic landscape of the mouse submandibular salivary gland (SMG) by performing chromatin immunoprecipitation sequencing experiments for 4 key histone marks. Our analysis of the comprehensive SMG data sets and comparisons with those from other adult organs have identified critical enhancers and super-enhancers of the mouse SMG. By further integrating these findings with complementary RNA-sequencing based gene expression data, we have unearthed a number of molecular regulators such as members of the Fox family of transcription factors that are enriched and likely to be functionally relevant for SMG biology. Overall, our studies provide a powerful atlas of cis-regulatory elements that can be leveraged for better understanding the transcriptional control mechanisms of the mouse SMG, discovery of novel genetic switches, and modulating tissue-specific gene expression in a targeted fashion.

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Genome-wide analysis and expression profile of the bZIP gene family in poplar

BMC Plant Biology ◽

10.1186/s12870-021-02879-w ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Kai Zhao ◽

Song Chen ◽

Wenjing Yao ◽

Zihan Cheng ◽

Boru Zhou ◽

...

Keyword(s):

Salt Stress ◽

Systems Biology ◽

Gene Family ◽

Stress Responses ◽

Metal Ion ◽

Gene Networks ◽

Expression Patterns ◽

Gene Set Enrichment Analysis ◽

Specific Gene ◽

Biological Processes

Abstract Background The bZIP gene family, which is widely present in plants, participates in varied biological processes including growth and development and stress responses. How do the genes regulate such biological processes? Systems biology is powerful for mechanistic understanding of gene functions. However, such studies have not yet been reported in poplar. Results In this study, we identified 86 poplar bZIP transcription factors and described their conserved domains. According to the results of phylogenetic tree, we divided these members into 12 groups with specific gene structures and motif compositions. The corresponding genes that harbor a large number of segmental duplication events are unevenly distributed on the 17 poplar chromosomes. In addition, we further examined collinearity between these genes and the related genes from six other species. Evidence from transcriptomic data indicated that the bZIP genes in poplar displayed different expression patterns in roots, stems, and leaves. Furthermore, we identified 45 bZIP genes that respond to salt stress in the three tissues. We performed co-expression analysis on the representative genes, followed by gene set enrichment analysis. The results demonstrated that tissue differentially expressed genes, especially the co-expressing genes, are mainly involved in secondary metabolic and secondary metabolite biosynthetic processes. However, salt stress responsive genes and their co-expressing genes mainly participate in the regulation of metal ion transport, and methionine biosynthetic. Conclusions Using comparative genomics and systems biology approaches, we, for the first time, systematically explore the structures and functions of the bZIP gene family in poplar. It appears that the bZIP gene family plays significant roles in regulation of poplar development and growth and salt stress responses through differential gene networks or biological processes. These findings provide the foundation for genetic breeding by engineering target regulators and corresponding gene networks into poplar lines.

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Fluorescent protein expression in temperature tolerant and susceptible reef-building corals

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315421000059 ◽

2021 ◽

pp. 1-10

Author(s):

Exequiel Gabriel S. Dizon ◽

Jeric P. Da-Anoy ◽

Melissa S. Roth ◽

Cecilia Conaco

Keyword(s):

Spectral Properties ◽

Coral Species ◽

Fluorescent Protein ◽

Fluorescent Proteins ◽

Expression Profiles ◽

Expression Patterns ◽

Antioxidant Properties ◽

Variable Expression ◽

Acropora Digitifera ◽

Insight Into

Abstract Fluorescent proteins (FPs) are reported to play an important role as photoprotectants and antioxidants in corals subjected to stressful conditions. Identifying the various FP genes expressed and FP gene expression patterns under stress in diverse coral species can provide insight into FP function. In this study, we identified 16 putative FP homologues from the transcriptomes of corals with varying susceptibility to elevated temperature, including Acropora digitifera, Favites colemani, Montipora digitata and Seriatopora caliendrum. Each coral expressed a different complement of FP transcripts, which were predicted to have distinct spectral properties. The most diverse and abundant repertoire of FP transcripts, including at least 6 green FPs, were expressed in the temperature-tolerant coral, F. colemani. In comparison, the other corals expressed fewer FP types. Specific FP transcripts exhibited variable expression profiles in coral fragments subjected to 32 ± 1 °C (treatment) or 28 ± 1 °C (control) for up to 72 h, suggesting that distinct FPs may have different roles. Further studies on the expression of the proteins encoded by these FP transcripts, their fluorescence activity, tissue localization, and possible antioxidant properties, are needed to reveal their contribution to thermal stress tolerance in certain species of corals.

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Stochasticity in Colonial Growth Dynamics of Individual Bacterial Cells

Applied and Environmental Microbiology ◽

10.1128/aem.03629-12 ◽

2013 ◽

Vol 79 (7) ◽

pp. 2294-2301 ◽

Cited By ~ 64

Author(s):

Konstantinos P. Koutsoumanis ◽

Alexandra Lianou

Keyword(s):

Kinetic Parameters ◽

Single Cells ◽

Growth Curves ◽

Growth Dynamics ◽

Time Lapse ◽

Initial Population ◽

Bacterial Cells ◽

Stochastic Growth ◽

Bacterial Populations ◽

Content Type

ABSTRACTConventional bacterial growth studies rely on large bacterial populations without considering the individual cells. Individual cells, however, can exhibit marked behavioral heterogeneity. Here, we present experimental observations on the colonial growth of 220 individual cells ofSalmonella entericaserotype Typhimurium using time-lapse microscopy videos. We found a highly heterogeneous behavior. Some cells did not grow, showing filamentation or lysis before division. Cells that were able to grow and form microcolonies showed highly diverse growth dynamics. The quality of the videos allowed for counting the cells over time and estimating the kinetic parameters lag time (λ) and maximum specific growth rate (μmax) for each microcolony originating from a single cell. To interpret the observations, the variability of the kinetic parameters was characterized using appropriate probability distributions and introduced to a stochastic model that allows for taking into account heterogeneity using Monte Carlo simulation. The model provides stochastic growth curves demonstrating that growth of single cells or small microbial populations is a pool of events each one of which has its own probability to occur. Simulations of the model illustrated how the apparent variability in population growth gradually decreases with increasing initial population size (N0). For bacterial populations withN0of >100 cells, the variability is almost eliminated and the system seems to behave deterministically, even though the underlying law is stochastic. We also used the model to demonstrate the effect of the presence and extent of a nongrowing population fraction on the stochastic growth of bacterial populations.

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