Loop-extruders alter bacterial chromosome topology to direct entropic forces for segregation.

Entropic forces have been argued to drive bacterial chromosome segregation during replication. In many bacterial species, however, specifically evolved mechanisms, such as loop-extruding SMC complexes and the ParABS origin segregation system, contribute to or are even required for chromosome segregation, suggesting that entropic forces alone may be insufficient. The interplay between and the relative contributions of these segregation mechanisms remain unclear. Here, we develop a biophysical model showing that purely entropic forces actually inhibit bacterial chromosome segregation until late replication stages. By contrast, our model reveals that loop-extruders loaded at the origins of replication, as observed in many bacterial species, alter the effective topology of the chromosome, thereby redirecting and enhancing entropic forces to enable accurate chromosome segregation during replication. We confirm our model predictions with polymer simulations: purely entropic forces do not allow for concurrent replication and segregation, whereas entropic forces steered by specifically loaded loop-extruders lead to robust, global chromosome segregation during replication. Finally, we show how loop-extruders can complement locally acting origin separation mechanisms, such as the ParABS system. Together, our results illustrate how changes in the geometry and topology of the polymer, induced by DNA-replication and loop-extrusion, impact the organization and segregation of bacterial chromosomes.

Planctoellipticum variicoloris gen. nov., sp. nov., a novel member of the family Planctomycetaceae isolated from wastewater of the aeration lagoon of a sugar processing plant in Northern Germany.

In the present study, we characterise a strain isolated from the wastewater aeration lagoon of a sugar processing plant in Schleswig (Northern Germany) by Heinz Schlesner. As a pioneer in planctomycetal research, he isolated numerous strains belonging to the phylum Planctomycetota from aquatic habitats around the world. Phylogenetic analyses show that strain SH412T belongs to the family Planctomycetaceae and shares with 91.6% the highest 16S rRNA gene sequence similarity with Planctopirus limnophila DSM 3776T. Its genome has a length of 7.3 Mb and a G + C content of 63.6%. Optimal growth of strain SH412T occurs at pH 7.0-7.5 and 28 °C with its pigmentation depending on sunlight exposure. Strain SH412T reproduces by polar asymmetric division ("budding") and forms ovoid cells. The cell size determination was performed using a semi-automatic pipeline, which we first evaluated with the model species P. limnophila and then applied to strain SH412T. Furthermore, the data acquired during time-lapse analyses suggests a lifestyle switch from flagellated daughter cells to non-flagellated mother cells in the subsequent cycle. Based on our data, we suggest that strain SH412T represents a novel species within a novel genus, for which we propose the name Planctoellipticum variicoloris gen. nov., sp. nov., with strain SH412T (= CECT 30430T = STH00996T, the STH number refers to the Jena Microbial Resource Collection JMRC) as the type strain of the new species.

Identification of Factor XIII ß-Sandwich Residues Mediating Glutamine Substrate Binding and Activation Peptide Cleavage.

BACKGROUND: Factor XIII (FXIII) forms covalent crosslinks across plasma and cellular substrates and has roles in hemostasis, wound healing, and bone metabolism. FXIII activity is implicated in venous thromboembolism (VTE) and is a target for developing pharmaceuticals, which requires understanding FXIII - substrate interactions. Previous studies proposed the ß-sandwich domain of the FXIII A subunit (FXIII-A) exhibits substrate recognition sites. MATERIAL AND METHODS: Recombinant FXIII-A proteins (WT, K156E, F157L, R158Q/E, R171Q, and R174E) were generated to identify FXIII-A residues mediating substrate recognition. Proteolytic (FXIII-A*) and non-proteolytic (FXIII-A°) forms were analyzed for activation and crosslinking activities toward physiological substrates using SDS-PAGE and MALDI-TOF MS. RESULTS: All FXIII-A* variants displayed reduced crosslinking abilities compared to WT for Fbg αC (233 - 425), fibrin, and actin. FXIII-A* WT activity was greater than A°, suggesting the binding site is more exposed in FXIII-A*. With Fbg αC (233 - 425), FXIII-A* variants R158Q/E, R171Q, and R174E exhibited decreased activities approaching those of FXIII-A°. However, with a peptide substrate, FXIII-A* WT and variants showed similar crosslinking suggesting the recognition site is distant from the catalytic site. Surprisingly, FXIII-A R158E and R171Q displayed slower thrombin activation than WT, potentially due to loss of crucial H-bonding with neighboring activation peptide (AP) residues. CONCLUSION: In conclusion, FXIII-A residues K156, F157, R158, R171, and R174 are part of a binding site for physiological substrates [fibrin (α and γ) and actin]. Moreover, R158 and R171 control AP cleavage during thrombin activation. These investigations provide new molecular details on FXIII - substrate interactions that control crosslinking abilities.

Intraspecific and interspecific interaction and fitness cost of stink bugs Euschistus heros, Diceraeus melacanthus, and Piezodorus guildinii in soybean.

BACKGROUND: The most common pentatomid species in soybean crops are Euschistus heros (F.), Piezodorus guildinii (W.), and Diceraeus melacanthus (D.), causing a significant reduction in yield. It is known that these stink bugs inhabit the reproductive structures of soybeans simultaneously; however, there are few studies addressing their intraguild interactions, as well as aspects of possible competition between them in plants. Thus, the interspecific and intraspecific interactions of these stink bugs were evaluated in laboratory and field conditions, throughout the duration of the instars and adulthood, including longevity, mortality, and the number of eggs per female. RESULTS: Euschistus heros had a higher competitive capacity in the interaction with D. melacanthus and P. guildinii, negatively interfering in the abundance or development (duration of instar, fertility, and mortality) of these stink bugs in soybean crops. This interference may act on the natural balance of these insect pests. Mortality of adults in interactions containing E. heros as a competitor or not showed that this species was not affected by the other species under field conditions. In the scenario where D. melacanthus was evaluated, it was observed that the presence of other species caused higher mortality in D. melacanthus. Additionally, higher P. guildiniii mortality was observed in interspecific interactions. CONCLUSION: Our results suggest that E. heros has a greater competitive ability in the soybean crop, followed by D. melacanthus and P. guildinii. Therefore, the results found justified the greater abundance of E. heros and helped to explain the increasing occurrence of D. melacanthus in soybean crops, contributing to new directions for understanding the interaction of the soybean stink bug complex. © 2023 Society of Chemical Industry.

Fbg αC 389-402 Enhances Factor XIII Cross-Linking in the Fibrinogen αC Region Via Electrostatic and Hydrophobic Interactions.

Coagulation Factor XIII (FXIII) stabilizes blood clots by cross-linking glutamines and lysines in fibrin and other proteins. FXIII activity in the fibrinogen αC region (Fbg αC 221-610) is critical for clot stability and growth. Fbg αC 389-402 is a binding site for thrombin-activated FXIII, (FXIII-A*), with αC E396 promoting FXIII-A* binding and activity in αC. The current study aimed to discover additional residues within Fbg αC 389-402 that accelerate transglutaminase activity toward αC. Electrostatic αC residues (E395, E396, and D390), hydrophobic αC residues (W391 and F394), and residues αC 328-425 were studied by mutations to recombinant Fbg αC 233-425. FXIII activity was monitored through MS-based glycine ethyl ester (GEE) cross-linking and gel-based fluorescence monodansylcadaverine (MDC) cross-linking assays. Truncation mutations 403 Stop (Fbg αC 233-402), 389 Stop (Fbg αC 233-388), and 328 Stop (Fbg αC 233-327) reduced Q237-GEE and MDC cross-linking compared to wild-type (WT). Comparable cross-linking between 389 Stop and 328 Stop showed that FXIII is mainly affected by the loss of Fbg αC 389-402. Substitution mutations E396A, D390A, W391A, and F394A decreased cross-linking relative to WT, whereas E395A, E395S, E395K, and E396D had no effect. Similar FXIII-A* activities were observed for double mutants (D390A, E396A) and (W391A, E396A), relative to D390A and W391A, respectively. In contrast, cross-linking was reduced in (F394A, E396A), relative to F394A. In conclusion, Fbg αC 389-402 boosts FXIII activity in Fbg αC, with D390, W391, and F394 identified as key contributors in enhancing αC cross-linking.

Incorporating Consumers' Needs in Nutrition Apps to Promote and Maintain Use: Mixed Methods Study.

BACKGROUND: Nutrition apps seem to be promising tools for supporting consumers toward healthier eating habits. There is a wide variety of nutrition apps available; however, users often discontinue app use at an early stage before a permanent change in dietary behavior can be achieved. OBJECTIVE: The main objective of this study was to identify, from both a user and nonuser perspective, which functionalities should be included in nutrition apps to increase intentions to start and maintain use of these apps. A secondary objective was to gain insight into reasons to quit using nutrition apps at an early stage. METHODS: This study used a mixed methods approach and included a qualitative and a quantitative study. The qualitative study (n=40) consisted of a home-use test with 6 commercially available nutrition apps, followed by 6 focus group discussions (FGDs) to investigate user experiences. The quantitative study was a large-scale survey (n=1420), which was performed in a representative sample of the Dutch population to quantify the FGDs' results. In the survey, several app functionalities were rated on 7-point Likert scales ranging from 1 (very unimportant) to 7 (very important). RESULTS: A total of 3 different phases of app use, subdivided into 10 user-centric app aspects and 46 associated app functionalities, were identified as relevant nutrition app elements in the FGDs. Relevance was confirmed in the survey, as all user-centric aspects and almost all app functionalities were rated as important to include in a nutrition app. In the starting phase, a clear introduction (mean 5.45, SD 1.32), purpose (mean 5.40, SD 1.40), and flexible food tracking options (mean 5.33, SD 1.45) were the most important functionalities. In the use phase, a complete and reliable food product database (mean 5.58, SD 1.41), easy navigation (mean 5.56, SD 1.36), and limited advertisements (mean 5.53, SD 1.51) were the most important functionalities. In the end phase, the possibility of setting realistic goals (mean 5.23, SD 1.44), new personal goals (mean 5.13, SD 1.45), and continuously offering new information (mean 4.88, SD 1.44) were the most important functionalities. No large differences between users, former users, and nonusers were found. The main reason for quitting a nutrition app in the survey was the high time investment (14/38, 37%). This was also identified as a barrier in the FGDs. CONCLUSIONS: Nutrition apps should be supportive in all 3 phases of use (start, use, and end) to increase consumers' intentions to start and maintain the use of these apps and achieve a change in dietary behavior. Each phase includes several key app functionalities that require specific attention from app developers. High time investment is an important reason to quit nutrition app use at an early stage.

Transglutaminase Activities of Blood Coagulant Factor XIII Are Dependent on the Activation Pathways and on the Substrates.

Factor XIII (FXIII) catalyzes formation of γ-glutamyl-ε-lysyl crosslinks between reactive glutamines (Q) and lysines (K). In plasma, FXIII is activated proteolytically (FXIII-A*) by the concerted action of thrombin and Ca2+. Cellular FXIII is activated nonproteolytically (FXIII-A°) by elevation of physiological Ca2+ concentrations. FXIII-A targets plasmatic and cellular substrates, but questions remain on correlating FXIII activation, resultant conformational changes, and crosslinking function to different physiological substrates. To address these issues, the characteristics of FXIII-A* versus FXIII-A° that contribute to transglutaminase activity and substrate specificities were investigated. Crosslinking of lysine mimics into a series of Q-containing substrates were measured using in-gel fluorescence, mass spectrometry, and UV-Vis spectroscopy. Covalent incorporation of fluorescent monodansylcadaverine revealed that FXIII-A* exhibits greater activity than FXIII-A° toward Q residues within Fbg αC (233-425 WT, Q328P Seoul II, and Q328PQ366N) and actin. FXIII-A* and FXIII-A° displayed similar activities toward α2-antiplasmin (α2AP), fibronectin, and Fbg αC (233-388, missing FXIII-binding site αC 389-402). Furthermore, the N-terminal α2AP peptide (1-15) exhibited similar kinetic properties for FXIII-A* and FXIII-A°. MALDI-TOF mass spectrometry assays with glycine ethyl ester and Fbg αC (233-425 WT, αC E396A, and truncated αC (233-388) further documented that FXIII-A* exerts greater benefit from the αC 389-402 binding site than FXIII-A°. Conformational properties of FXIII-A* versus A° are proposed to help promote transglutaminase function toward different substrates. A combination of protein substrate disorder and secondary FXIII-binding site exposure are utilized to control activity and specificity. From these studies, greater understandings of how FXIII-A targets different substrates are achieved.

Comparing meat abstainers with avid meat eaters and committed meat reducers.

Shifting our eating patterns toward less animal-based and more plant-based diets is urgently needed to counter climate change, address public health issues, and protect animal welfare. Although most consumers agree that these are important topics, many consumers are not particularly willing to decrease the meat intensity of their diets. In supporting consumers to shift their diets, it is important to understand consumers' attitudes, motivations, and preferences related to meat consumption and to take differences across consumers on these aspects into account. This study aims to in-depth research meat abstainers (vegetarians and vegans), and to explore how and to what extent they differ from avid meat eaters and committed meat reducers in terms of their (1) socio-demographic characteristics, (2) attitudes and norms, (3) food choice motives, and (4) food preferences and behavior. A survey has been conducted among a representative sample of Dutch adults. Comparisons show that meat abstainers (N = 198) differ from committed meat reducers (N = 171) and avid meat eaters (N = 344) on the four included categories of variables. In terms of demographics, we largely confirm the stereotype of vegans and vegetarians being highly educated females. In attitudes and norms, large differences exist with meat abstainers being least pro-meat and avid meat eaters being most pro-meat. Food choice motives confirm this, with meat abstainers valuing animal welfare and a good feeling higher than committed meat reducers and avid meat eaters. Finally, differences across the groups are most pronounced in terms of their food preferences and consumption, with a much higher appreciation of plant-based protein sources among meat abstainers, a high appreciation of non-meat animal-based proteins across committed meat reducers and a high appreciation of meat products among avid meat eaters. This shows that although differences across the groups are gradual and expected, in terms of reduction motivations and preferences of protein sources the three groups (frequent meat consumption-meat reduction-meat avoidance) are very distinct, which makes it unlikely to expect big shifts from one group to another in the short term.

Social Norms Support the Protein Transition: The Relevance of Social Norms to Explain Increased Acceptance of Alternative Protein Burgers over 5 Years.

Developing alternative protein products-based on protein sources other than regular meat-is a possible pathway to counter environmental and health burdens. However, alternative proteins are not always accepted by consumers, and more research is needed to support a shift to more alternative proteins. Prior studies have mainly focused on individual drivers and perceptions; although we expect that social norms-the perceptions of the opinions of relevant others-are highly relevant in accepting alternative proteins. Online surveys were conducted among 2461 respondents in 2015 and 2000 respondents in 2019 (cross-sectional datasets); a subsample (n = 500) responded to both surveys (longitudinal dataset). We add to the literature by (1) demonstrating the added explanatory value of social norms beyond a range of individual drivers; (2) showing that this finding holds over time, and (3) comparing the impact of social norms across different dietary consumer groups. Meat lovers and flexitarians are more prone to follow social norms whereas meat abstainers are more prone to follow their individual attitudes and values. This study highlights the relevance of investigations beyond personal variables such as personal norms and attitudes and underscores the relevance of considering the social aspects of accepting alternative proteins.

The Impact of Both Individual and Contextual Factors on the Acceptance of Personalized Dietary Advice.

(1) Background: The aim of the current study is to investigate which between- and within-person factors influence the acceptance of personalized dietary advice. (2) Methods: A repeated measurements design was used in which 343 participants (M (SD) age = 48 (17.3), 49% female) filled out a baseline survey and started with nine repeated surveys. (3) Results: The results show that the acceptance of personalized dietary advice is influenced by both within-person and between-person factors. The acceptance is higher at lunch compared to breakfast and dinner, higher at home than out of home, higher at moments when individuals have a high intention to eat healthily, find weight control an important food choice motive and have a high healthy-eating self-efficacy. Moreover, the acceptance is higher when individuals do not see the eating context as a barrier and when individuals believe that personalized dietary advice has more benefits than risks. (4) Conclusions: Future behavioral interventions that use personalized dietary advice should consider the context as well as individual differences.

Context matters: Self-regulation of healthy eating at different eating occasions.

Self-regulation plays an important role in healthy eating behaviors. The current research explores temporary fluctuations in self-regulation next to variations between individuals. In an online observational study, 892 participants (Mage = 44.3, SDage = 12.7) monitored their self-regulation three times a week before a meal moment for 3 weeks. To analyze the data, a random intercept and slopes model was used, including variables on within-individual level (i.e. meal moment, tiredness, distractedness, social, and physical environment) and variables on between-individual level (i.e. self-efficacy, intrinsic motivation, and perception of social and physical opportunity). Self-regulation was found to be higher at breakfast compared with dinner (estimate = -0.08, p < .001), higher at home than out-of-home (estimate = -0.08, p < .001) and lower when individuals are more tired (estimate = 0.04, p < .001) and distracted (estimate = 0.07, p < .001). Moreover, self-regulation was higher for individuals with higher levels of intrinsic motivation (estimate = 0.19, p < .001) and self-efficacy (estimate = 0.41, p < .001). Insights from this research advance our knowledge regarding temporal influences on self-regulation and can provide input for behavior change tools such as personalized dietary advice.

Healthy eating strategies: Individually different or context-dependent?

Individuals can apply different healthy eating strategies to help them make healthy eating choices. Previous research showed that individuals differ in their preferred strategy, but also that a mix of strategies is often applied by a single person across contexts. The current research investigated the extent to which differences within an individual across contexts (i.e., meal moments, social environment and physical environment) predicted openness to healthy eating strategies in addition to personal predictors that differ between individuals (i.e., intrinsic motivation, self-efficacy, physical opportunity and social opportunity). A representative sample of the Dutch adult population was recruited (N = 892). The within-individual (contextual) predictors were measured nine times just before a meal moment over a period of three weeks, by means of a smartphone application. The between-individual (personal) predictors were administered with a baseline questionnaire. Exploratory factor analysis distinguished three healthy eating strategies: Increasing healthy foods, Limiting unhealthy foods and consuming Light products. A random intercept model, in which within-individual predictors and between-individual predictors were entered successively, showed that context matters for openness to all three strategies, but is most important for increasing healthy foods and least important for light products. Individuals are most open to increase healthy foods at dinner as compared to breakfast, whereas the opposite is true for limiting unhealthy foods and consuming light products. Eating at home is beneficial for openness to all three strategies and eating with others positively influences openness to increase healthy foods but has no effect on the other strategies. Insights gained from this research increase our understanding of an individual's openness to apply healthy eating strategies.

Demanda asistencial en un Servicio de Pediatría durante el estado de alarma secundario a la COVID-19 / Demand for care in a Pediatric Service during the state of alarm secondary to COVID-19

Antecedentes y objetivos. La COVID-19 es una enfermedad producida por el virus SARS-CoV-2. En España,entre el mes de marzo y junio de 2020 se declaró el primer Estado de Alarma con el fin de contener la pandemia.Nuestro objetivo es evaluar la demanda asistencial y lasenfermedades que acudieron a Urgencias Pediátricas y quefueron ingresadas durante el tiempo que duró el primer Estado de Alarma, comparando con los mismos meses delos años 2018 y 2019.Resultados. Existe una reducción del número de ingresosde 345 a 141, un incremento de la complejidad demostrada por una mayor duración de los ingresos hasta 7,3±12,4 días(6,2±8,6 días en 2018 y 4,8±6,9 en 2019). Las enfermedades infecciosas (principalmente las respiratorias) descendieron, permaneciendo estables los ingresos por neoplasias, patología psiquiátrica, apendicitis y enfermedades circulatorias. EnUrgencias Pediátricas, en los años 2018 y 2019 (de 1 marzoa 30 junio) se atendieron 9.075 y 8.525 pacientes, mientras que en el 2020 se atendieron 2.215, aumentando el porcentajede ingresos procedentes de urgencias del 3,6% y 3,4% al 6%en 2020. Las enfermedades que aumentaron de forma más importante fueron las lesiones traumáticas y las intoxicaciones. Tanto en los ingresos como en urgencias existe unincremento en la edad de los pacientes. Conclusiones. El Estado de Alarma influyó en la presión asistencial y en el tipo de enfermedades atendidas enel Servicio de Pediatría, con una disminución del número de Urgencias y de ingresos, un incremento de la edad y unamodificación del tipo de enfermedades atendidas.

Introduction and objectives. COVID-19 is a disease caused by the SARS-CoV-2 virus. In Spain, between March and June 2020, the first State of Alarm was declared in order to contain the pandemic. Our objective is to evaluate the health care demand and the diseases that came to the Pediatric Emergency Department and were admitted during the time that the first State of Alarm lasted, comparing with the same months of the years 2018 and 2019.Results. There is a reduction in the number of admissions from 345 to 141, an increase in complexity demonstrated by a longer duration of admissions to 7.3±12.4 days (6.2 ± 8.6 days in 2018 and 4, 8±6.9 in 2019). Infectious diseases (mainly respiratory) decreased, with admissions for neoplasms, psychiatric pathology, appendicitis and circulatory diseases remaining stable. In Pediatric Emergencies, in the years 2018 and 2019 (from March 1 to June 30), 9,075 and 8,525 patients were attended, while in 2020, 2,215 were attended, increasing the percentage of admissions from the emergency room of 3.6% and 3.4% to 6% in 2020. The diseases that increased most significantly were traumatic injuries and poisonings. Both in admissions and in emergencies there is an increase in the age of the patients. Conclusions. The State of Alarm influenced the care pressure and the type of diseases treated in the Pediatric Service, with a decrease in the number of Emergencies and admissions, an increase in age and a modification of the type of diseases treated (AU)

Elongation at Midcell in Preparation of Cell Division Requires FtsZ, but Not MreB nor PBP2 in Caulobacter crescentus.

Controlled growth of the cell wall is a key prerequisite for bacterial cell division. The existing view of the canonical rod-shaped bacterial cell dictates that newborn cells first elongate throughout their side walls using the elongasome protein complex, and subsequently use the divisome to coordinate constriction of the dividing daughter cells. Interestingly, another growth phase has been observed in between elongasome-mediated elongation and constriction, during which the cell elongates from the midcell outward. This growth phase, that has been observed in Escherichia coli and Caulobacter crescentus, remains severely understudied and its mechanisms remain elusive. One pressing open question is which role the elongasome key-component MreB plays in this respect. This study quantitatively investigates this growth phase in C. crescentus and focuses on the role of both divisome and elongasome components. This growth phase is found to initiate well after MreB localizes at midcell, although it does not require its presence at this subcellular location nor the action of key elongasome components. Instead, the divisome component FtsZ seems to be required for elongation at midcell. This study thus shines more light on this growth phase in an important model organism and paves the road to more in-depth studies.

An unexpected puzzle piece links polarity and chromosome segregation.

To ensure successful daughter cell production with one chromosome each, C. crescentus bacteria use an extensively regulated phosphorelay to link all involved cellular processes. In this issue of Developmental Cell, Guzzo et al. (2021) show that the activity of this phosphorelay depends on the translocation of the segregating chromosome.

ATG9A protects the plasma membrane from programmed and incidental permeabilization.

The integral membrane protein ATG9A plays a key role in autophagy. It displays a broad intracellular distribution and is present in numerous compartments, including the plasma membrane (PM). The reasons for the distribution of ATG9A to the PM and its role at the PM are not understood. Here, we show that ATG9A organizes, in concert with IQGAP1, components of the ESCRT system and uncover cooperation between ATG9A, IQGAP1 and ESCRTs in protection from PM damage. ESCRTs and ATG9A phenocopied each other in protection against PM injury. ATG9A knockouts sensitized the PM to permeabilization by a broad spectrum of microbial and endogenous agents, including gasdermin, MLKL and the MLKL-like action of coronavirus ORF3a. Thus, ATG9A engages IQGAP1 and the ESCRT system to maintain PM integrity.

Retinyl esters form lipid droplets independently of triacylglycerol and seipin.

Lipid droplets store neutral lipids, primarily triacylglycerol and steryl esters. Seipin plays a role in lipid droplet biogenesis and is thought to determine the site of lipid droplet biogenesis and the size of newly formed lipid droplets. Here we show a seipin-independent pathway of lipid droplet biogenesis. In silico and in vitro experiments reveal that retinyl esters have the intrinsic propensity to sequester and nucleate in lipid bilayers. Production of retinyl esters in mammalian and yeast cells that do not normally produce retinyl esters causes the formation of lipid droplets, even in a yeast strain that produces only retinyl esters and no other neutral lipids. Seipin does not determine the size or biogenesis site of lipid droplets composed of only retinyl esters or steryl esters. These findings indicate that the role of seipin in lipid droplet biogenesis depends on the type of neutral lipid stored in forming droplets.

Learning the distribution of single-cell chromosome conformations in bacteria reveals emergent order across genomic scales.

The order and variability of bacterial chromosome organization, contained within the distribution of chromosome conformations, are unclear. Here, we develop a fully data-driven maximum entropy approach to extract single-cell 3D chromosome conformations from Hi-C experiments on the model organism Caulobacter crescentus. The predictive power of our model is validated by independent experiments. We find that on large genomic scales, organizational features are predominantly present along the long cell axis: chromosomal loci exhibit striking long-ranged two-point axial correlations, indicating emergent order. This organization is associated with large genomic clusters we term Super Domains (SuDs), whose existence we support with super-resolution microscopy. On smaller genomic scales, our model reveals chromosome extensions that correlate with transcriptional and loop extrusion activity. Finally, we quantify the information contained in chromosome organization that may guide cellular processes. Our approach can be extended to other species, providing a general strategy to resolve variability in single-cell chromosomal organization.

Generating asymmetry in a changing environment: cell cycle regulation in dimorphic alphaproteobacteria.

While many bacteria divide by symmetric binary fission, some alphaproteobacteria have strikingly asymmetric cell cycles, producing offspring that differs significantly in their morphology and reproductive state. To establish this asymmetry, these species employ a complex cell cycle regulatory pathway based on two-component signaling cascades. At the center of this network is the essential DNA-binding response regulator CtrA, which acts as a transcription factor controlling numerous genes with cell cycle-relevant functions as well as a regulator of chromosome replication. The DNA-binding activity of CtrA is controlled at the level of both protein phosphorylation and stability, dependent on an intricate network of regulatory proteins, whose function is tightly coordinated in time and space. CtrA is differentially activated in the two (developing) offspring, thereby establishing distinct transcriptional programs that ultimately determine their distinct cell fates. Phase-separated polar microdomains of changing composition sequester proteins involved in the (in-)activation and degradation of CtrA specifically at each pole. In this review, we summarize the current knowledge of the CtrA pathway and discuss how it has evolved to regulate the cell cycle of morphologically distinct alphaproteobacteria.