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Mononuclear phagocytes facilitate the dissemination of the obligate intracellular parasite Toxoplasma gondii. Here, we report how a set of secreted parasite effector proteins from dense granule organelles (GRA) orchestrates dendritic cell-like chemotactic and pro-inflammatory activation of parasitized macrophages. These effects enabled efficient dissemination of the type II T. gondii lineage, a highly prevalent genotype in humans. We identify novel functions for effectors GRA15 and GRA24 in promoting CCR7-mediated macrophage chemotaxis by acting on NF-κB and p38 mitogen-activated protein kinase signaling pathways, respectively, with contributions by GRA16/18 and counter-regulation by effector TEEGR. Furthermore, GRA28 boosted chromatin accessibility and GRA15/24/NF-κB-dependent transcription at the Ccr7 gene locus in primary macrophages. In vivo, adoptively transferred macrophages infected with wild-type T. gondii outcompeted macrophages infected with a GRA15/24 double mutant in migrating to secondary organs in mice. The data show that T. gondii, rather than being passively shuttled, actively promotes its dissemination by inducing a finely regulated pro-migratory state in parasitized human and murine phagocytes via co-operating polymorphic GRA effectors.ImportanceIntracellular pathogens can hijack the cellular functions of infected host cells to their advantage, for example, for intracellular survival and dissemination. However, how microbes orchestrate the hijacking of complex cellular processes, such as host cell migration, remains poorly understood. As such, the common parasite Toxoplasma gondii actively invades the immune cells of humans and other vertebrates and modifies their migratory properties. Here, we show that the concerted action of a number of secreted effector proteins from the parasite, principally GRA15 and GRA24, acts on host cell signaling pathways to activate chemotaxis. Furthermore, the protein effector GRA28 selectively acted on chromatin accessibility in the host cell nucleus to selectively boost host gene expression. The joint activities of GRA effectors culminated in pro-migratory signaling within the infected phagocyte. We provide a molecular framework delineating how T. gondii can orchestrate a complex biological phenotype, such as the migratory activation of phagocytes to boost dissemination.

Salmonella translocate to the gut epithelium via microfold cells lining the follicle-associated epithelium (FAE). How Salmonella localize to the FAE is not well characterized. Here we use live imaging and competitive assays between wild-type and chemotaxis-deficient mutants to show that Salmonella enterica serotype Typhimurium (S. Typhimurium) localize to the FAE independently of chemotaxis in an ex vivo mouse caecum infection model. Electrical recordings revealed polarized FAE with sustained outward current and small transepithelial potential, while the surrounding villus is depolarized with inward current and large transepithelial potential. The distinct electrical potentials attracted S. Typhimurium to the FAE while Escherichia coli (E. coli) localized to the villi, through a process called galvanotaxis. Chloride flux involving the cystic fibrosis transmembrane conductance regulator (CFTR) generated the ionic currents around the FAE. Pharmacological inhibition of CFTR decreased S. Typhimurium FAE localization but increased E. coli recruitment. Altogether, our findings demonstrate that bioelectric cues contribute to S. Typhimurium targeting of specific gut epithelial locations, with potential implications for other enteric bacterial infections.

UNLABELLED: Motility promotes biofilm initiation during the early steps of this process: microbial surface association and attachment. Motility is controlled in part by chemotaxis signaling, so it seems reasonable that chemotaxis may also affect biofilm formation. There is a gap, however, in our understanding of the interactions between chemotaxis and biofilm formation, partly because most studies analyzed the phenotype of only a single chemotaxis signaling mutant, e.g., cheA. Here, we addressed the role of chemotaxis in biofilm formation using a full set of chemotaxis signaling mutants in Helicobacter pylori, a class I carcinogen that infects more than half the worlds population and forms biofilms. Using mutants that lack each chemotaxis signaling protein, we found that chemotaxis signaling affected the biofilm initiation stage, but not mature biofilm formation. Surprisingly, some chemotaxis mutants elevated biofilm initiation, while others inhibited it in a manner that was not tied to chemotaxis ability or ligand input. Instead, the biofilm phenotype correlated with flagellar rotational bias. Specifically, mutants with a counterclockwise bias promoted biofilm initiation, e.g., ∆cheA, ∆cheW, or ∆cheV1; in contrast, those with a clockwise bias inhibited it, e.g., ∆cheZ, ∆chePep, or ∆cheV3. We tested this correlation using a counterclockwise bias-locked flagellum, which induced biofilm formation independent of the chemotaxis system. These CCW flagella, however, were not sufficient to induce biofilm formation, suggesting there are downstream players. Overall, our work highlights the new finding that flagellar rotational direction promotes biofilm initiation, with the chemotaxis signaling system operating as one mechanism to control flagellar rotation. IMPORTANCE: Chemotaxis signaling systems have been reported to contribute to biofilm formation in many bacteria; however, how they regulate biofilm formation remains largely unknown. Chemotaxis systems are composed of many distinct kinds of proteins, but most previous work analyzed the biofilm effect of loss of only a few. Here, we explored chemotaxis role during biofilm formation in the human-associated pathogenic bacterium Helicobacter pylori. We found that chemotaxis proteins are involved in biofilm initiation in a manner that correlated with how they affected flagellar rotation. Biofilm initiation was high in mutants with counterclockwise (CCW) flagellar bias and low in those with clockwise bias. We supported the idea that a major driver of biofilm formation is flagellar rotational direction using a CCW-locked flagellar mutant, which stays CCW independent of chemotaxis input and showed elevated biofilm initiation. Our data suggest that CCW-rotating flagella, independent of chemotaxis inputs, are a biofilm-promoting signal.

UNLABELLED: The bacterial chemotaxis system is a well-understood signaling pathway that promotes bacterial success. Chemotaxis systems comprise chemoreceptors and the CheA kinase, linked by CheW or CheV scaffold proteins. Scaffold proteins provide connections between chemoreceptors and CheA and also between chemoreceptors to create macromolecular arrays. Chemotaxis is required for host colonization by many microbes, including the stomach pathogen Helicobacter pylori. This bacterium builds chemoreceptor-CheA contacts with two distinct scaffold proteins, CheW and CheV1. H. pylori cheW or cheV1 deletion mutants both lose chemoreceptor array formation, but show differing semisolid agar chemotaxis assay behaviors: ∆cheW mutants exhibit total migration failure, whereas ∆cheV1::cat mutants display a 50% reduction. On investigating these varied responses, we found that both mutants initially struggle with migration. However, over time, ∆cheV1::cat mutants develop a stable, enhanced migration capability, termed migration-able (Mig+). Whole-genome sequencing analysis of four distinct ∆cheV1::cat Mig+ strains identified single-nucleotide polymorphisms (SNPs) in hpg27_252 (hp0273) that were predicted to truncate the encoded protein. Computational analysis of the hpg27_252-encoded protein revealed it encoded a hypothetical protein that was a remote homolog of the PilO Type IV filament membrane alignment complex protein. Although H. pylori lacks Type IV filaments, our analysis showed it retains an operon of genes for homologs of PilO, PilN, and PilM. Deleting hpg27_252 in the ∆cheV1::cat or wild type strain resulted in enhanced migration in semisolid agar. Our study thus reveals that while cheV1 mutants initially have significant migration defects, they can recover the migration ability through genetic suppressors, highlighting a complex regulatory mechanism in bacterial migration. IMPORTANCE: Chemotactic motility, present in over half of bacteria, depends on chemotaxis signaling systems comprising receptors, kinases, and scaffold proteins. In Helicobacter pylori, a stomach pathogen, chemotaxis is crucial for colonization, with CheV1 and CheW as key scaffold proteins. While both scaffolds are essential for building chemoreceptor complexes, their roles vary in other assays. Our research reexamines cheV1 mutants behavior in semisolid agar, a standard chemotaxis test. Initially, cheV1 mutants exhibited defects similar to those of cheW mutants, but they evolved genetic suppressors that enhanced migration. These suppressors involve mutations in a previously uncharacterized gene, unknown in motility behavior. Our findings highlight the significant chemotaxis defects in cheV1 mutants and identify new elements influencing bacterial motility.

Chemotactic bacteria not only navigate chemical gradients, but also shape their environments by consuming and secreting attractants. Investigating how these processes influence the dynamics of bacterial populations has been challenging because of a lack of experimental methods for measuring spatial profiles of chemoattractants in real time. Here, we use a fluorescent sensor for aspartate to directly measure bacterially generated chemoattractant gradients during collective migration. Our measurements show that the standard Patlak-Keller-Segel model for collective chemotactic bacterial migration breaks down at high cell densities. To address this, we propose modifications to the model that consider the impact of cell density on bacterial chemotaxis and attractant consumption. With these changes, the model explains our experimental data across all cell densities, offering insight into chemotactic dynamics. Our findings highlight the significance of considering cell density effects on bacterial behavior, and the potential for fluorescent metabolite sensors to shed light on the complex emergent dynamics of bacterial communities.

While much literature on chemotaxis systems focuses on bounded domains, this paper emphasizes the global existence of classical solutions for three primary chemotaxis systems with a logistic source on R n. We present a unified proof demonstrating global existence of solutions can be deduced from their locally uniform boundedness in L p (R n) for some p > max ⁡ { 1 , n 2 }. We then provide sufficient conditions for the global existence and boundedness of classical solutions. Notably, our findings even improve several existing results for bounded domains. [ABSTRACT FROM AUTHOR]

This article is dedicated to the no-flux attraction-repulsion chemotaxis model { u t = Δ u − χ ∇ ⋅ (u v ∇ v) + ξ ∇ ⋅ (u w ∇ w) + h (u) , x ∈ Ω , t > 0 , v t = Δ v − v + u , x ∈ Ω , t > 0 , w t = Δ w − w + u , x ∈ Ω , t > 0 defined in a smooth and bounded domain Ω ⊂ R n (n ≥ 1). The parameters χ , ξ > 0 and the logistic source fulfilling h (s) ≤ r − μ s γ or h (s) = r s − μ s 2 with r ≥ 0 , μ > 0 and proper γ > 0 are used in certain scenarios. Our first result exhibits that the corresponding initial-boundary value problem admits a classical solution which is global if γ > 2 or γ = 2 and μ is sufficiently large. Moreover, assuming that h (s) satisfies the latter condition, the global existence of a weak solution is achieved. [ABSTRACT FROM AUTHOR]

Machining scheme selection is presently time-consuming and inefficient due to singularity and uncertainty in decision-making. Typically, the selection is based on a singular feature, with eventual outcomes remaining uncertain. In response, this paper proposes a feature-group-oriented re-optimized bacterial foraging algorithm to solve this problem by selecting the optimal machining schemes for multiple similar features in one part at once. Our focus is on designing the re-optimized bacterial foraging algorithm to optimize machining schemes, which considers the processes of chemotaxis, fine-tuning, replication, and adaptive migration with re-optimization. Then, comparative studies with varying weights and algorithms are conducted as an illustration of machining scheme selection for the hole feature-group. The results indicate that the re-optimized bacterial foraging algorithm accurately produces three distinct machining schemes based on varying weights. Additionally, the optimal average value outperforms other algorithms in the comparative study, demonstrating the algorithm's validity and superiority. [ABSTRACT FROM AUTHOR]

This work deals with a three-component chemotaxis system u t = Δ u - ∇ · (u χ 1 (w) ∇ w) + w - μ 1 u 2 , x ∈ Ω , t > 0 , v t = Δ v - ∇ · (v χ 2 (w) ∇ w) + w + r u v - μ 2 v 2 , x ∈ Ω , t > 0 , w t = Δ w + u + v - w , x ∈ Ω , t > 0 , describing the spatiotemporal Alopecia Areata dynamics with signal-dependent sensitivity under homogeneous Neumann boundary conditions in a smoothly bounded domain Ω ⊂ R n (n ≥ 1) , where the parameters μ 1 , μ 2 , r are positive constants. The chemotactic function χ i (w) (i = 1 , 2) is smooth and satisfying some conditions. Given suitably regular initial data, it is shown that the corresponding initial-boundary value problem admits a unique global bounded classical solution. Furthermore, by constructing the appropriate energy function, it is proved that the unique coexistence equilibrium is globally convergent in a specific parameter regime. These results generalize and improve some well-known results in the literature. [ABSTRACT FROM AUTHOR]

Alopecia areata (AA) is an autoimmune disease whose clinical phenotype is characterized by the formation of distinct hairless patterns on the scalp or other parts of the body. In this paper, we study a three-component chemotaxis model for AA, which describes the complex interactions among CD 4 + T cells, CD 8 + T cells and interferon-gamma (IFN- γ ). Our first purpose is to establish the uniform boundedness of classical solutions for the model by self-map method, which extends the corresponding results of Lou and Tao (J Differ Equ 305:401–427, 2021, JDE) and Zhang et al. (Math Biosci Eng 20(5):7922–7942, 2023, MBE) to the case of arbitrary spatial dimensions and non-equidiffusive coefficients. Another purpose is to consider the globally asymptotic stability and convergence rate of the positive equilibrium under either (i) small proliferation rate and large degradation parameters or (ii) weak chemoattractive effect or strong random motions. It is shown under the above two cases that sparse patches occur in or around diseased hair follicles, gradually develop into diffuse or total hair loss and ultimately induce AA. [ABSTRACT FROM AUTHOR]

In this paper, we deal with the following quasilinear chemotaxis–consumption system with degenerate signal-dependent motility u t = ∇ · (v α ∇ u m) + α ∇ · (v α - 1 u ∇ v) + r u - μ u 2 , x ∈ Ω , t > 0 , v t = Δ v - u v , x ∈ Ω , t > 0 , under the homogeneous Neumann boundary condition in Ω ⊂ R n (n ≥ 1) with α , r , μ > 0 and m > 1 . It is shown that above system admits at least one global weak solution fulfilling the following boundedness property ‖ u (· , t) ‖ L p (Ω) + ‖ v (· , t) ‖ W 1 , ∞ (Ω) ≤ C for all t > 0 , p > 2 and m > 1 . This result gives an evident of the regularized effect of porous-medium-type diffusion. [ABSTRACT FROM AUTHOR]

We consider the no-flux initial-boundary value problem for the growth-expansion model with chemotaxis in nutrient-replete environments in smoothly bounded domains Ω ⊂ ℝ n . It is shown that if n = 1 or if n = 2 under some structural assumptions on parameter functions therein, for any suitably regular initial data the problem admits a unique global bounded classical solution. For any dimensions n ≥ 3 , we also prove that the problem has a unique global classical solution which is bounded under a small assumption on the initial data. Moreover, we obtain that these solutions stabilize to a uniquely determined spatially uniform equilibrium. We also provide exponential rates of convergence of solutions in a special case. [ABSTRACT FROM AUTHOR]

Methylobacterium sp. 2A, a plant growth‐promoting rhizobacteria (PGPR) able to produce indole‐3‐acetic acid (IAA), significantly promoted the growth of Arabidopsis thaliana plants in vitro. We aimed to understand the determinants of Methylobacterium sp. 2A–A. thaliana interaction, the factors underlying plant growth‐promotion and the host range. Methylobacterium sp. 2A displayed chemotaxis to methanol and formaldehyde and was able to utilise 1‐aminocyclopropane carboxylate as a nitrogen source. Confocal microscopy confirmed that fluorescent protein‐labelled Methylobacterium sp. 2A colonises the apoplast of A. thaliana primary root cells and its inoculation increased jasmonic and salicylic acid in A. thaliana, while IAA levels remained constant. However, inoculation increased DR5 promoter activity in root tips of A. thaliana and tomato plants. Inoculation of this PGPR partially restored the agravitropic response in yucQ mutants and lateral root density was enhanced in iaa19, arf7, and arf19 mutant seedlings. Furthermore, Methylobacterium sp. 2A volatile organic compounds (VOCs) had a dose‐dependent effect on the growth of A. thaliana. This PGPR is also able to interact with monocots eliciting positive responses upon inoculation. Methylobacterium sp. 2A plant growth‐promoting effects can be achieved through the regulation of plant hormone levels and the emission of VOCs that act either locally or at a distance. Summary statement: Arabidopsis thaliana–Methylobacterium sp. 2A interaction and communication involve the modulation of plant hormones, root colonisation, and the production of volatile organic compounds. Methylobacterium sp. 2A promotes plant growth via auxin‐mediated regulation of the root architecture. [ABSTRACT FROM AUTHOR]

The use of algae for industrial, biotechnological, and agricultural purposes is spreading globally. Scenedesmus species can play an essential role in the food industry and agriculture due to their favorable nutrient content and plant-stimulating properties. Previous research and the development of Scenedesmus-based foliar fertilizers raised several questions about the effectiveness of large-scale algal cultivation and the potential effects of algae on associative rhizobacteria. In the microbiological practice applied in agriculture, bacteria from the genus Azospirillum are one of the most studied plant growth-promoting, associative, nitrogen-fixing bacteria. Co-cultivation with Azospirillum species may be a new way of optimizing Scenedesmus culturing, but the functioning of the co-culture system still needs to be fully understood. It is known that Azospirillum brasilense can produce indole-3-acetic acid, which could stimulate algae growth as a plant hormone. However, the effect of microalgae on Azospirillum bacteria is unclear. In this study, we investigated the behavior of Azospirillum brasilense bacteria in the vicinity of Scenedesmus sp. or its supernatant using a microfluidic device consisting of physically separated but chemically coupled microchambers. Following the spatial distribution of bacteria within the device, we detected a positive chemotactic response toward the microalgae culture. To identify the metabolites responsible for this behavior, we tested the chemoeffector potential of citric acid and oxaloacetic acid, which, according to our HPLC analysis, were present in the algae supernatant in 0.074 mg/ml and 0.116 mg/ml concentrations, respectively. We found that oxaloacetic acid acts as a chemoattractant for Azospirillum brasilense. [ABSTRACT FROM AUTHOR]

The following two-species chemotaxis system with signal-dependent motilities and indirect signal consumption u t = Δ γ 1 w u + μ 1 u 1 - u - a 1 v , x ∈ Ω , t > 0 , v t = Δ γ 2 w v + μ 2 v 1 - a 2 u - v , x ∈ Ω , t > 0 , w t = Δ w - w z , x ∈ Ω , t > 0 , z t = Δ z - z + u + v , x ∈ Ω , t > 0 , is considered in a smooth bounded domain Ω ∈ R n (n ≥ 1) with homogeneous Neumann boundary conditions, where the parameters a i > 0 , μ i ≥ 0 (i = 1 , 2) and the motility functions satisfy that γ i (w) ∈ C 3 ([ 0 , ∞ ]) , γ i (w) > 0 for all w ≥ 0 . It is proved that the associated initial-boundary value problem possesses a unique global and uniformly bounded classical solution in higher space dimensions for μ i > 0 properly large and in any dimension for small | | w 0 | | L ∞ (Ω) with μ i = 0 . Furthermore, it is shown that the global bounded solution of this system converges to different steady states under the different values of μ i and a i . Meanwhile, the precise convergence rates of global solutions are derived in the paper. [ABSTRACT FROM AUTHOR]

In this paper, we investigated a distributed optimal control problem for the viscous Cahn-Hilliard-Oono system. In this system, chemotaxis, active transport, and nonlocal interaction of Oono's type were also taken into account. The system consisted of a viscous Cahn-Hilliard equation for the difference in volume fractions of the two components $ \varphi $ and a diffusion-reaction equation for the nutrient concentration $ \sigma $. Our aim was to achieve a desired goal of the difference in volume fractions of the two components by minimizing the cost functional of standard tracking type. To begin, the strong well-posedness of the state system was addressed. Then, we establish the existence of optimal controls. Afterward, we presented the Fréchet differentiability of the control-to-state operator $ \mathcal S $. Lastly, we derived the first-order necessary optimality conditions by considering the backward adjoint system. [ABSTRACT FROM AUTHOR]

This paper deals with the chemotaxis system with signal-dependent motility and indirect signal consumption and logistic source$ \begin{eqnarray*} \left\{ \begin{array}{llll} u_t = \Delta (u\gamma(v))+au-bu^l, \quad &x\in \Omega, t>0, \\ v_t = \Delta v - vw, \quad &x\in \Omega, t>0, \\ w_t = - \delta w + u, \quad &x\in \Omega, t>0, \end{array} \right. \end{eqnarray*} $under homogeneous Neumann boundary conditions in a smooth bounded domain $ \Omega\subset \mathbb{R}^n $ ($ n\geq1 $). Here the parameters $ \delta >0 $, $ a>0 $, $ b>0 $ and $ l>1 $, and the motility function $ \gamma \in {C^3}\left({\left[ {0, + \infty } \right)} \right) $ is positive on $ [0, \infty) $. For all suitably regular initial data, if one of the following cases holds:(ⅰ) $ n \le 3, l > 1 $;(ⅱ) $ n \ge 4, l > 2 $;(ⅲ) $ n \ge 4, l = 2 $ and $ b $ is sufficiently large,then the corresponding initial boundary value problem possesses global bounded classical solutions. Our goal extends the global solution result by Li et al. [19] with sufficiently large values of $ l > \max \{ 1, \frac{n}{2}\} $. [ABSTRACT FROM AUTHOR]

We consider a parabolic-elliptic chemotaxis system with singular sensitivity and sublinear production: u t = Δ u - χ ∇ · u v α ∇ v , 0 = Δ v - v + g (u) in a smooth bounded domain Ω ⊂ R n (n ⩾ 2) with χ > 0 , α ∈ (0 , 1 ] , k 1 u β 1 ⩽ g (u) ⩽ k 2 u β 2 with β 1 , β 2 ∈ (0 , 1) and k 1 , k 2 > 0 . It proved that the system possesses a globally bounded classical solution when α ∈ (0 , 1) and β 2 ∈ 0 , 2 n with χ > 0 , or α = 1 and β 2 ∈ (0 , 1) with χ ∈ (0 , min { 1 , 2 n β 2 }) . This entails that sublinear productive effect is indeed benefit to ensure globally bounded classical solution to parabolic-elliptic chemotaxis with singular chemotactic mechanism. [ABSTRACT FROM AUTHOR]

We consider a non-local tumour growth model of phase-field type, describing the evolution of tumour cells through proliferation in presence of a nutrient. The model consists of a coupled system, incorporating a non-local Cahn-Hilliard equation for the tumour phase variable and a reaction-diffusion equation for the nutrient. First, we establish novel regularity results for such a model, by applying maximal regularity theory in weighted L p spaces. This technique enables us to prove the local existence and uniqueness of a regular solution, including also chemotaxis effects. By leveraging time-regularisation properties and global boundedness estimates, we further extend the solution to a global one. These results provide the foundation for addressing an optimal control problem, aimed at identifying a suitable therapy, guiding the tumour towards a predefined target. Specifically, we prove the existence of an optimal therapy and, by studying the Fréchet-differentiability of the control-to-state operator and introducing the adjoint system, we derive first-order necessary optimality conditions. [ABSTRACT FROM AUTHOR]

In this paper, we provide the normal form for the Hopf bifurcation of a class of the reaction‐diffusion equation with memory‐based diffusion and nonlocal effect, where the delay is present in the differential term, similar to the chemotaxis model with time delay. The eigenvalue problems and the decomposition of the phase space are discussed in detail. Through a series of variable transformations, we obtain the third‐order truncated normal form of the model constrained on the central manifold and its equivalent equation in polar coordinates. Then, with the help of the dynamic analysis for the finite dimensional equations, the key parameters for determining the direction and stability of the Hopf bifurcation are given. These theoretical results are applied to the Bazykin's model, the stability, Turing bifurcation and Hopf bifurcation of the equilibrium are demonstrated through both theoretical and numerical methods. [ABSTRACT FROM AUTHOR]

We mainly study the negligibility of haptotaxis effect on global existence, boundedness and convergence of classical solutions to a four-component chemotaxis-haptotaxis system with indirect signal production: { u t = Δ u − χ ∇ ⋅ (u ∇ v) − ξ ∇ ⋅ (u ∇ w) in Ω × (0 , ∞) , v t = Δ v − v + m in Ω × (0 , ∞) , m t = Δ m − m + u in Ω × (0 , ∞) , w t = − v w + η w (1 − w) in Ω × (0 , ∞) , in a bounded and smooth domain Ω ⊂ R n (1 ≤ n ≤ 5) with nonnegative parameters χ , ξ , η , nonnegative regular initial data (u 0 , v 0 , m 0 , w 0) and homogeneous Neumann boundary conditions. When n ≤ 3 , it is proven that solutions to the corresponding Neumann initial-boundary value problem exist globally in time for any η ≥ 0 and remain bounded for small η ≥ 0 ; when n = 4 , η = 0 and Ω is a ball centered at the origin, global boundedness of radially symmetric solutions is shown under ‖ u 0 ‖ L 1 (Ω) < (8 π) 2 χ ; and when n ∈ { 4 , 5 } , η = 0 and χ = 0 , global boundedness of solutions is shown. In either case, the global bounded w -solution component is shown to decay exponentially in W 1 , ∞ (Ω) and the global bounded (u , v , m) -solution component converges exponentially in L ∞ (Ω) to that of the corresponding indirect chemotaxis-only model for suitably small χ ≥ 0. This project incorporates a biological mechanism modeling indirect signal production in chemotaxis-haptotaxis models and our results extend the previous work of Fujie & Senba (2017) [11] on indirect chemotaxis-only system (w ≡ 0) to indirect chemotaxis-haptotaxis one, revealing that the effect of haptotaxis can be neglected even in a chemotaxis system with indirect signal production. Furthermore, our findings demonstrate that indirect chemotaxis mechanism has positive effect on boundedness and enlarges critical blow-up mass comparing to the existing result of Jin & Xiang (2021) [19] on the corresponding direct chemotaxis-haptotaxis model, providing a further understanding about this indirect mechanism in chemotaxis-haptotaxis settings. [ABSTRACT FROM AUTHOR]

Microgliosis plays a critical role in diet-induced hypothalamic inflammation. A few hours after a high-fat diet (HFD), hypothalamic microglia shift to an inflammatory phenotype, and prolonged fat consumption leads to the recruitment of bone marrow-derived cells to the hypothalamus. However, the transcriptional signatures and functions of these cells remain unclear. Using dual-reporter mice, this study reveals that CX3CR1-positive microglia exhibit minimal changes in response to a HFD, while significant transcriptional differences emerge between microglia and CCR2-positive recruited myeloid cells, particularly affecting chemotaxis. These recruited cells also show sex-specific transcriptional differences impacting neurodegeneration and thermogenesis. The chemokine receptor CXCR3 is emphasized for its role in chemotaxis, displaying notable differences between recruited cells and resident microglia, requiring further investigation. Central immunoneutralization of CXCL10, a ligand for CXCR3, resulted in increased body mass and decreased energy expenditure, especially in females. Systemic chemical inhibition of CXCR3 led to significant metabolic changes, including increased body mass, reduced energy expenditure, elevated blood leptin, glucose intolerance, and decreased insulin levels. This study elucidates the transcriptional differences between hypothalamic microglia and CCR2-positive recruited myeloid cells in diet-induced inflammation and identifies CXCR3-expressing recruited immune cells as protective in metabolic outcomes linked to HFD consumption, establishing a new concept in obesity-related hypothalamic inflammation. [ABSTRACT FROM AUTHOR]

In this paper we consider radially symmetric solutions of the following parabolic-elliptic cross-diffusion system { u t = Δ u − ∇ (u f (| ∇ v | 2) ∇ v) , 0 = Δ v − μ (t) + g (u) , μ (t) = 1 | Ω | ∫ Ω g (u (⋅ , t)) d x u (x , 0) = u 0 (x) , in Ω × (0 , ∞) , with Ω a ball in R N , N ≥ 1 under homogeneous Neumann boundary conditions, g (u) a regular function with the prototype g (u) = u k , u ≥ 0 , k > 0 . The function f (ξ) = k f (1 + ξ) − α , k f > 0 , describes gradient-dependent limitation of cross diffusion fluxes. Under suitable conditions on the data, we prove that the solution is global in time. If N ≥ 3 , under conditions on f , g and initial data, we prove that if the solution u (x , t) blows up in L ∞ -norm at finite time T m a x then for some p > 1 it blows up also in L p -norm. Moreover a lower bound of blow-up time is derived. [ABSTRACT FROM AUTHOR]

This paper deals with a predator-prey system with density-dependent diffusion and indirect pursuit-evasion interaction under homogeneous Neumann boundary conditions. By providing appropriate conditions, the asymptotic stability of solution is investigated. [ABSTRACT FROM AUTHOR]

This paper is concerned with the dynamical stability of spiky steady states to a chemotaxis-consumption model with signal-dependent motilities on the half space, where no-flux boundary condition for the bacteria and inhomogeneous Dirichlet boundary condition for the nutrient are prescribed. The motilities of bacteria depend on the concentration of nutrient in the form of power law, which means that they are degenerate if the power-law exponent is positive and are singular if the exponent is negative at the zero state of nutrient. We show that in both cases the spiky patterns admitted by the model are nonlinearly stable under appropriate perturbations. We introduce a unified approach to dealing with both degeneracy and singularity in the diffusivity for this model. The approach is based on a combination of weighted energy estimates and weighted elliptic estimates, where various weights are artfully constructed to capture the complex behaviors of solutions near the zero state. Numerical simulations are also carried out to confirm our theoretical results. [ABSTRACT FROM AUTHOR]

This paper is concerned with the Keller–Segel system with flux limitation, (⁎) { u t = Δ u − ∇ ⋅ (u f (| ∇ v | 2) ∇ v) , v t = Δ v − v + u in bounded n -dimensional domains with homogeneous Neumann boundary conditions, where f generalizes the prototype obtained on letting f (ξ) = k f (1 + ξ) − α , ξ ≥ 0 , with k f > 0 and α > 0. In this framework, it is shown that if either n = 1 and α > 0 is arbitrary, or n ≥ 2 and α > n − 2 2 (n − 1) , then for any nonnegative initial data belonging to the space of Radon measures for the population density and to a suitable first-order Sobolev space for the signal density, there exists a global classical solution of the Neumann problem for (⁎) , which is continuous at t = 0 in an appropriate sense. [ABSTRACT FROM AUTHOR]

The chemotaxis-consumption model { u t = ∇ ⋅ ((u + 1) α ∇ u) − ∇ ⋅ (u (u + 1) β − 1 ∇ v) , x ∈ Ω , t > 0 0 = Δ v − u v , x ∈ Ω , t > 0 is considered in a smooth bounded domain Ω ⊂ R n under the boundary conditions (u + 1) α ∂ ν u = u (u + 1) β − 1 ∂ ν v and ∂ ν v = (γ − v) g on ∂Ω, with parameters α , β ∈ R , γ > 0 and the nonnegative function g ∈ C 1 + ω (Ω ¯) for some ω ∈ (0 , 1). If β − α ≤ 1 , it is proved that there exists a global bounded classical solution (u , v) for suitably regular initial data u 0. Furthermore, for the given mass m = ∫ Ω u ∞ > 0 , the corresponding stationary system admits a unique classical solution (u ∞ , v ∞) , appearing as a large-time limit in the sense that if γ > 0 is small enough, then ‖ u (⋅ , t) − u ∞ ‖ L ∞ (Ω) + ‖ v (⋅ , t) − v ∞ ‖ L ∞ (Ω) → 0 as t → ∞ , with ∫ Ω u ∞ = ∫ Ω u 0 = m > 0. [ABSTRACT FROM AUTHOR]

The bacterial chemotaxis system is one of the best-understood cellular pathways and serves as the model for signal transduction systems. Most chemotaxis research has been conducted with transmembrane chemotaxis systems from Escherichia coli and has established paradigms of the system that were thought to be universal. However, emerging research has revealed that many bacteria possess alternative features of their chemotaxis system, demonstrating that these systems are likely more complex than previously assumed. Here, we compare the canonical chemotaxis system of E. coli with systems that diverge in supramolecular architecture, sensory mechanisms, and protein composition. The alternative features have likely evolved to accommodate chemical specificities of natural niches and cell morphologies. Collectively, these studies demonstrate that bacterial chemotaxis systems are a rapidly expanding field that offers many new opportunities to explore this exceedingly diverse system. [ABSTRACT FROM AUTHOR]

The social amoeba Polysphondylium violaceum uses chemoattractants different from those of Dictyoctelium discoideum for cell aggregation. However, the detailed mechanisms in P. violaceum remain unknown. We have previously reported that the polyketide synthase StlA is involved in inducing aggregation in this species. To elucidate the mechanism of StlA-induced aggregation in P. violaceum , we analyzed the phenotype of P. violaceum stlA − (Pv - stlA −) mutants in more detail. Unlike our previous results, the mutant cells did not exhibit proper chemotaxis toward glorin. Defective aggregation was not restored by glorin pulses, 8Br-cAMP, or deletion of the homologue of PufA that is a translational repressor of protein kinase A, whereas mutant cells grown in the presence of 4-methyl-5-pentylbenzene-1,3-diol (MPBD), the putative Pv-StlA product, aggregated normally without it after starvation. Furthermore, the early developmental marker gene, dscA , was downregulated in the mutant cells. Our data thus suggested that StlA is required for the transition from growth to development in P. violaceum. [ABSTRACT FROM AUTHOR]

Tumor-associated macrophages (TAMs) in the tumor microenvironment (TME) promote immune evasion, cancer cell proliferation, and metastasis. Ongoing research is focused on finding ways to prevent tumor growth by inhibiting TAM polarization, which has shown a correlation with unfavorable prognosis in clinical studies. Pancreatic adenocarcinoma up-regulated factor (PAUF) is a protein secreted from pancreatic cancer (PC) and acts as a TME modulator that affects the TME by acting on not only cancer cells but also stromal cells and immune cells. Tumor cells can evade the immune system by PAUF binding to Toll-like receptor (TLR) in monocytes, as this research shows. In this study, the examination centered around the recruitment of human monocytes by PAUF and the subsequent differentiation into macrophages. In an in vitro chemotaxis assay, PAUF induced chemotactic migration of TLR2-mediated monocytes. In addition, PAUF induced differentiation of monocytes into M2 macrophages, which was verified based on expressing surface markers and cytokines and morphological analysis. The inhibition of T cell proliferation and function was observed in differentiated M2 macrophages. To conclude, these findings indicate that PAUF functions as a promoter of cancer progression by regulating the recruitment and differentiation of macrophages within TMEs, ultimately causing immunosuppression. [ABSTRACT FROM AUTHOR]

We consider the nonlinear elliptic system $$\begin{align*} \left\{ \begin{array}{ll} u \in W_{0}^{\frac{N}{N-1}}(\Omega): & -\textrm{div}(M(x)\nabla u) + u = -\textrm{div}(u\,M(x)\,\nabla\psi) + f(x),\\ \displaystyle \psi \in W_0^{1,2}(\Omega): & -\textrm{div}(M(x)\nabla \psi) + \psi = R(u) + E(x)\,\nabla\psi, \end{array} \right. \end{align*}$$ { u ∈ W 0 N N − 1 (Ω) : − div (M (x) ∇u) + u = − div (u M (x) ∇ψ) + f (x) , ψ ∈ W 0 1 , 2 (Ω) : − div (M (x) ∇ψ) + ψ = R (u) + E (x) ∇ψ , where Ω is a bounded, open subset of $ \mathbb {R}^N $ R N , $ N \geq ~3 $ N ≥ 3 ; $ M(x) $ M (x) is a coercive, symmetric matrix with $ L^{\infty }(\Omega) $ L ∞ (Ω) coefficients; $ f(x) $ f (x) and $ E(x) $ E (x) belong to some Lebesgue space, and $ R(s) $ R (s) is a continuous function such that $$\begin{align*} 0 \leq R(s)\leq |s|^{\theta}, \quad \mbox{for}\ \theta { \lt } \frac{2}{N}. \end{align*}$$ 0 ≤ R (s) ≤ | s | θ , for θ < 2 N. Using a duality technique, we prove existence of at least a weak solution $ (u,\psi) $ (u , ψ). Moreover, if N=3 or N=4, we prove under stronger assumptions on $ f(x) $ f (x) and $ E(x) $ E (x) that the solution u belongs to $ W_0^{1,2}(\Omega) $ W 0 1 , 2 (Ω). [ABSTRACT FROM AUTHOR]

Summary: Escherichia coli (E. coli) biofilm is the major cause of its high lethality in foodborne illness. Controlling E. coli biofilm formation is a critical way to reduce foodborne diseases. Here, chiral borneol isomers (L‐borneol, D‐borneol, and isoborneol) were identified as E. coli chemorepellents, which reduced reversible adhesion at the initial stage of biofilm formation. Borneols directly inhibited biofilm production and their inhibitory capacities were associated with the chiral stereochemical structures (L‐borneol > D‐borneol > isoborneol). A transcriptomic study revealed the inhibitory mechanism of borneols was attributed to the bacterial motility intention and motility energy system. The most effective isomer, L‐borneol, reduced bacterial energy metabolism and increased E. coli chemotaxis motility intention through the up‐regulation of genes associated with flagellar assembly and bacterial chemotaxis pathways. This work demonstrates that borneols are biofilm inhibitors and supports the potential of borneols as a stereochemical antimicrobial strategy to reduce foodborne pathogenic bacterial contamination. [ABSTRACT FROM AUTHOR]

In this paper, the pattern formation of a volume-filling chemotaxis model with bistable source terms was studied. First, it was shown that self-diffusion does not induce Turing patterns, but chemotaxis-driven instability occurs. Then, the asymptotic behavior of the chemotaxis model was analyzed by weakly nonlinear analysis with the method of multiple scales. When the chemotaxis coefficient exceeded a threshold value and there was a single unstable mode, the supercritical and subcritical bifurcation of the model was discussed. The amplitude equations and the asymptotic expressions of the patterns were obtained. When the chemotaxis coefficient was large enough, the two-mode competition behavior of the model with two unstable modes was analyzed, and the corresponding amplitude equations and the asymptotic expressions of the patterns were obtained. Finally, numerical simulations were provided to further illuminate the above analytical results. [ABSTRACT FROM AUTHOR]

Root exudates play a pivotal role in shaping the microbial community in the rhizosphere and can impact the efficacy of bacteria in controlling nematode populations. This study identified Proteus vulgaris BX-1 as significantly effective in controlling Meloidogyne incognita. The infection of tomato plants with this nematode induced noticeable alterations in the composition of tomato root exudates and led to an increased colonization rate of strain BX-1. Further investigation into how strain BX-1 responded to changes in tomato root exudates revealed that specific metabolites, such as caffeic acid, coumarin, salicylic acid, sebacic acid, and butyric acid, strongly attracted strain BX-1. This attraction potentially contributed to its enhanced colonization and improved efficiency in controlling nematodes. Understanding the correlation between specific metabolites in root exudates and the response of antagonistic bacteria provides valuable insights for enhancing their effectiveness as biological control agents against plant-parasitic nematodes. [ABSTRACT FROM AUTHOR]

During recovery from septic shock, circulating mitochondrial N -formyl peptides predispose to secondary infection by occupying formyl peptide receptor 1 on the neutrophil (polymorphonuclear leukocyte) membrane, suppressing cytosolic calcium ([Ca2+]i)-dependent responses to secondarily encountered bacteria. However, no study has yet investigated therapeutic clearance of circulating mitochondrial N -formyl peptides in clinical settings. Thus, we studied how to remove mitochondrial N -formyl peptides from septic-shock plasma and whether such removal could preserve cell-surface formyl peptide receptor 1 and restore sepsis-induced polymorphonuclear leukocyte dysfunction by normalizing [Ca2+]i flux. In in vitro model systems, mitochondrial N -formyl peptide removal rescued polymorphonuclear leukocyte formyl peptide receptor 1-mediated [Ca2+]i flux and chemotaxis that had been suppressed by prior mitochondrial N -formyl peptide exposure. However, polymorphonuclear leukocyte functional recovery occurred in a stepwise fashion over 30 to 90 min. Intracellular Ca2+-calmodulin appears to contribute to this delay. In ex vivo model, systems using blood samples obtained from patients with septic shock, antimitochondrial N -formyl peptide antibodies alone failed to eliminate mitochondrial N -formyl peptides from septic-shock plasma or inhibit mitochondrial N -formyl peptide activity. We therefore created a beads-based antimitochondrial N -formyl peptide antibody cocktail by combining protein A/sepharose with antibodies specific for the most potent human mitochondrial N -formyl peptide chemoattractants. The beads-based antimitochondrial N -formyl peptide antibody cocktail treatment successfully removed those active mitochondrial N -formyl peptides from septic-shock plasma. Furthermore, the beads-based antimitochondrial N -formyl peptide antibody cocktail treatment significantly restored chemotactic and bactericidal dysfunction of polymorphonuclear leukocytes obtained from patients with septic shock who developed secondary infections. By clearing circulating mitochondrial N -formyl peptides, the immobilized antimitochondrial N -formyl peptide antibody therapy prevented mitochondrial N -formyl peptide interactions with surface formyl peptide receptor 1, thereby restoring [Ca2+]i-dependent polymorphonuclear leukocyte antimicrobial function in clinical septic-shock environments. This approach may help prevent the development of secondary, nosocomial infections in patients recovering from septic shock. [ABSTRACT FROM AUTHOR]

Neutrophils are essential cells involved in inflammation. However, the specific mechanism of neutrophil chemotaxis induced by Treponema pallidum remains unknown. In this study, human umbilical vein endothelial cells (HUVECs) were utilized as target cells to investigate the expression levels of chemokines when stimulated with different concentrations of Tp0768 (also known as TpN44.5 or TmpA, a T. pallidum infection dependent antigen). The results indicated that Tp0768 treatment enhanced neutrophil chemotaxis in HUVECs, which was closely associated with the expression levels of CXCL1, CXCL2, and CXCL8 (also known as interleukin-8). At the same time, the results show that the Toll-like receptor 2 (TLR2) signaling pathway is activated and that endoplasmic reticulum (ER) stress occurs. Furthermore, the findings revealed that the use of protein kinase RNA-like endoplasmic reticulum kinase (PERK) and immunoglobulin-regulated enhancer 1 (IRE1) inhibitors reduced the expression levels of CXCL1, CXCL2, and CXCL8. Additionally, inhibiting TLR2 significantly decreased the expression levels of ER stress–related proteins (PERK and IRE1), CXCL1, CXCL2, and CXCL8. Consequently, neutrophil chemotaxis was significantly inhibited after treatment with TLR2, PERK, and IRE1 inhibitors. These findings shed light on the role of Tp0768 in enhancing neutrophil chemotaxis in endothelial cells, providing a foundation for further exploration of syphilis pathogenesis and offering a new direction for the diagnosis and treatment of T. pallidum infection. [ABSTRACT FROM AUTHOR]

This work considers the doubly degenerate nutrient model u t = ∇ · u m - 1 v ∇ u - ∇ · f (u) v ∇ v + ℓ u v , x ∈ Ω , t > 0 , v t = Δ v - u v , x ∈ Ω , t > 0 , under no-flux boundary conditions in a smoothly bounded convex domain Ω ⊂ R n ( n ≤ 2 ), where the nonnegative function f ∈ C 1 ([ 0 , ∞)) is assumed to satisfy f (s) ≤ C f s α with α > 0 and C f > 0 for all s ≥ 1 . When m = 2 , it was shown that a global weak solution exists, either in one-dimensional setting with α = 2 , or in two-dimensional version with α ∈ 1 , 3 2 . The main results in this paper assert the global existence of weak solutions for 1 ≤ m < 3 and classical solutions for 3 ≤ m < 4 to the above system under the assumption α ∈ m - 1 , min m , m 2 + 1 if n = 1 , and m - 1 , min m , m 2 + 1 if n = 2 , which extend the range α ∈ (1 , 3 2) to α ∈ (1 , 2) in two dimensions for the case m = 2 . Our proof will be based on a new observation on the coupled energy-type functional and on an inequality with general form. [ABSTRACT FROM AUTHOR]

The chemotaxis-Navier–Stokes system n t + u · ∇ n = Δ (n c - α ) , c t + u · ∇ c = Δ c - n c , u t + (u · ∇) u = Δ u + ∇ P + n ∇ Φ , ∇ · u = 0 , modelling the behavior of aerobic bacteria in a fluid drop, is considered in a smoothly bounded domain Ω ⊂ R 2 . For all α > 0 and all sufficiently regular Φ , we construct global classical solutions and thereby extend recent results for the fluid-free analogue to the system coupled to a Navier–Stokes system. As a crucial new challenge, our analysis requires a priori estimates for u at a point in the proof when knowledge about n is essentially limited to the observation that the mass is conserved. To overcome this problem, we also prove new uniform-in-time L p estimates for solutions to the inhomogeneous Navier–Stokes equations merely depending on the space-time L 2 norm of the force term raised to an arbitrary small power. [ABSTRACT FROM AUTHOR]

Introduction: The rhizosphere is the zone of soil surrounding plant roots that is directly influenced by root exudates released by the plant, which select soil microorganisms. The resulting rhizosphere microbiota plays a key role in plant health and development by enhancing its nutrition or immune response and protecting it from biotic or abiotic stresses. In particular, plant growth-promoting rhizobacteria (PGPR) are beneficial members of this microbiota that represent a great hope for agroecology, since they could be used as bioinoculants for sustainable crop production. Therefore, it is necessary to decipher the molecular dialog between roots and PGPR in order to promote the establishment of bioinoculants in the rhizosphere, which is required for their beneficial functions. Methods: Here, the ability of root exudates from rapeseed (Brassica napus), pea (Pisum sativum), and ryegrass (Lolium perenne) to attract and feed three PGPR (Bacillus subtilis, Pseudomonas fluorescens, and Azospirillum brasilense) was measured and compared, as these responses are directly involved in the establishment of the rhizosphere microbiota. Results: Our results showed that root exudates differentially attracted and fed the three PGPR. For all beneficial bacteria, rapeseed exudates were the most attractive and induced the fastest growth, while pea exudates allowed the highest biomass production. The performance of ryegrass exudates was generally lower, and variable responses were observed between bacteria. In addition, P. fluorescens and A. brasilense appeared to respond more efficiently to root exudates than B. subtilis. Finally, we proposed to evaluate the compatibility of each plant–PGPR couple by assigning them a “love match” score, which reflects the ability of root exudates to enhance bacterial rhizocompetence. Discussion: Taken together, our results provide new insights into the specific selection of PGPR by the plant through their root exudates and may help to select the most effective exudates to promote bioinoculant establishment in the rhizosphere. [ABSTRACT FROM AUTHOR]

Zoospores of the filamentous actinomycete Actinoplanes missouriensis swim vigorously using flagella and stop swimming to initiate germination in response to nutrient exposure. However, the molecular mechanisms underlying swimming cessation remain unknown. A protein (FtgA) of unknown function encoded by a chemotaxis gene cluster (che cluster-1) was found to be required for flagellar rotation arrest; the zoospores of ftgA-knockout mutants kept swimming awkwardly after germination. An ftgA-overexpressing strain exhibited a non-flagellated phenotype. Isolation of a suppressor strain from this strain and further in vivo experiments revealed that the extended N-terminal region of FliN, a component of the C-ring of the flagellar basal body, was involved in the function of FtgA; FliN-P101S canceled the flagellar rotation arrest by FtgA, as well as the negative effect of ftgA-overexpression on flagellation. Furthermore, bacterial two-hybrid assays suggested that FtgA interacted not only with the C-terminal core region of FliN but also with chemotaxis regulatory proteins CheA1 and CheW1-2, which are encoded by che cluster-1. We propose the following working model of motility regulation in A. missouriensis zoospores: the chemotaxis sensory complex initially captures FtgA to allow zoospores to swim and then releases FtgA to stop flagellar rotation (i.e., swimming) in response to external nutrient signals. The actinomycete Actinoplanesmissouriensis produces flagellated zoospores that stop swimming before germination. A genetic study has revealed that a hypothetical protein encoded by a chemotaxis gene cluster is required for flagellar rotation arrest. [ABSTRACT FROM AUTHOR]

In this paper, we consider the following 2D incompressible chemotaxis‐Navier–Stokes equations with the fractional diffusion ∂tn+u·∇n−Δn=−∇·(n∇c)+n(1−n)(n−a),∂tc+u·∇c−Δc=−cn,∂tu+u·∇u+∧2αu+∇P=−n∇ϕ,$$ \left\{\begin{array}{l}{\partial}_tn&#x0002B;u\cdotp \nabla n-\Delta n&#x0003D;-\nabla \cdotp \left(n\nabla c\right)&#x0002B;n\left(1-n\right)\left(n-a\right),\\ {}{\partial}_tc&#x0002B;u\cdotp \nabla c-\Delta c&#x0003D;- cn,\\ {}{\partial}_tu&#x0002B;u\cdotp \nabla u&#x0002B;{\wedge}&#x0005E;{2\alpha }u&#x0002B;\nabla P&#x0003D;-n\nabla \phi, \end{array}\right. $$ where ∧:=(−Δ)12$$ \wedge :&#x0003D; {\left(-\Delta \right)}&#x0005E;{\frac{1}{2}} $$ and α∈[12,1]$$ \alpha \in \left[\frac{1}{2},1\right] $$. The gravitational potential ϕ$$ \phi $$ is generally supposed to be sufficiently smooth given functions. By establishing the new priori estimates, we get the global well‐posedness for the above system with large initial data. [ABSTRACT FROM AUTHOR]

Multifunctional nanoagents are robust to remodel environments for managing chronic diabetic wounds. However, their delivery primarily relies on Brownian motion and randomly enhanced diffusion. Here, taking advantage of wound heterogeneity, such as the uneven distribution of glucose, hyperglycemia targeting nanomotors are proposed. They are capable of efficiently targeting hyperglycemic interfaces in diabetic wounds for significantly accelerating their healing by employing endogenous glucose‐activated cascade reactions and responding to local glucose gradients. Compared to previous counterparts, they show a four‐fold enhancement in effective coverage within 60 s and a multiplied accumulation at hyperglycemic interfaces, facilitating deep penetration. Correspondingly, the downregulation of glucose levels is apparently enhanced, while pH‐lowering and oxygen‐supplying are both improved. In comparison to the counterparts delivered by passive diffusion and randomly enhanced diffusion, the hyperglycemia targeting nanomotor‐based spray accelerates the wound healing upon diabetic mice by approximately 30% and 23%, resulting from the restricted inflammatory response, effective reactive oxygen species (ROS) scavenging and elevated vascular endothelial growth factor levels (VEGF). This study presents a generally efficient approach to facilitating the targeted delivery of nanoagents for the effective management of diabetic wounds by utilizing wound heterogeneity, which can be extended to other therapeutic systems. [ABSTRACT FROM AUTHOR]

Effective intratumoral drug penetration is pivotal for successful cancer treatment. However, due to the disrupted capillary networks and poor perfusion in solid tumors, there exist challenges to realize autonomous directional drug penetration and controlled drug release within the tumor. Considering the specificity of glucose within tumor tissue, we draw inspiration from nature and engineer asymmetrical hollow structures exhibiting chemotaxis towards high glucose levels. By incorporating multiple shells into these structures, we enhance the local chemical concentration gradients, thereby improving cellular uptake and precise targeting. The advantages of anisotropic hollow multishell structure (a‐HoMS) can be reflected from the diffusion coefficient and directivity, which increase by 73.4 % and 273 % respectively compared to conventional isotropic hollow spheres, achieving the most linear movement while ensuring the speed of movement. Furthermore, the multi‐level porosity and temporal‐spatial order of a‐HoMS enable sequential drug delivery that inhibits angiogenesis with inducing cell apoptosis. After the eradication of localized tumor cells, the a‐HoMS can automatically migrate to the alive tumor cells under the glucose gradient, inducing another cycle of drug delivery and chemotaxis, resulting in excellent antitumor efficacy. These anisotropic HoMS demonstrate intelligence, adaptability, and precision in tumor therapy, providing valuable insights for programmable treatment within tissues. [ABSTRACT FROM AUTHOR]

Collective migration of eukaryotic cells is often guided by chemotaxis, and is critical in several biological processes, such as cancer metastasis, wound healing, and embryogenesis. Understanding collective chemotaxis has challenged experimental, theoretical and computational scientists because cells can sense very small chemoattractant gradients that are tightly controlled by cell-cell interactions and the regulation of the chemoattractant distribution by the cells. Computational models of collective cell migration that offer a high-fidelity resolution of the cell motion and chemoattractant dynamics in the extracellular space have been limited to a small number of cells. Here, we present Dynamic cluster field modeling (DCF), a novel computational method that enables simulations of collective chemotaxis of cellular systems with O (1000) cells and high-resolution transport dynamics of the chemoattractant in the time-evolving extracellular space. We illustrate the efficiency and predictive capabilities of our approach by comparing our numerical simulations with experiments in multiple scenarios that involve chemoattractant secretion and uptake by the migrating cells, cell migration in confined spaces, regulation of the attractant distribution by cell motion, and interactions of the chemoattractant with an enzyme. The proposed algorithm opens new opportunities to address outstanding problems that involve collective cell migration in the central nervous system, immune response and cancer metastasis. [ABSTRACT FROM AUTHOR]

Background: E. coli chemotactic motion in the presence of a chemonutrient field can be studied using wet laboratory experiments or macroscale-level partial differential equations (PDEs) (among others). Bridging experimental measurements and chemotactic Partial Differential Equations requires knowledge of the evolution of all underlying fields, initial and boundary conditions, and often necessitates strong assumptions. In this work, we propose machine learning approaches, along with ideas from the Whitney and Takens embedding theorems, to circumvent these challenges. Results: Machine learning approaches for identifying underlying PDEs were (a) validated through the use of simulation data from established continuum models and (b) used to infer chemotactic PDEs from experimental data. Such data-driven models were surrogates either for the entire chemotactic PDE right-hand-side (black box models), or, in a more targeted fashion, just for the chemotactic term (gray box models). Furthermore, it was demonstrated that a short history of bacterial density may compensate for the missing measurements of the field of chemonutrient concentration. In fact, given reasonable conditions, such a short history of bacterial density measurements could even be used to infer chemonutrient concentration. Conclusion: Data-driven PDEs are an important modeling tool when studying Chemotaxis at the macroscale, as they can learn bacterial motility from various data sources, fidelities (here, computational models, experiments) or coordinate systems. The resulting data-driven PDEs can then be simulated to reproduce/predict computational or experimental bacterial density profile data independent of the coordinate system, approximate meaningful parameters or functional terms, and even possibly estimate the underlying (unmeasured) chemonutrient field evolution. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a chemotaxis system under homogeneous Neumann boundary conditions within a bounded domain with a smooth boundary. The system describes the movement of cells in response to two chemical signal substances: one acts as a chemoattractant, while the other serves as a chemorepellent, both produced by the cells. The system takes into account chemotactic sensitivity in the reaction movement when detecting these chemicals. Under certain assumptions, we demonstrate the existence of a unique global bounded classical solution for the proposed problem. To further understand the time evolution of the system's solutions, we conduct numerical experiments and analyze the dynamic properties of the L∞(Ω)$$ {L}&#x0005E;{\infty}\left(\Omega \right) $$ norm of the solutions with respect to variations in chemical production rates. [ABSTRACT FROM AUTHOR]

Chemotaxis is the ability of some organisms to direct their motion in response to chemical signals. This behavior is important across biological scales, from olfactory navigation in animals, to cell migration in development. Chemotaxis is particularly important for bacteria, many of which are capable of directing their motion towards nutrients and away from toxins. The history of bacterial chemotaxis as a field stretches as far back as the late 19th century when scientists observed various species' ability to localize around gas bubbles and pipettes filled with nutrients. After these initial observations, however, it would take over 60 years for the mechanisms of this behavior to come into focus. In this primer, Moore and Emonet introduce the problem of chemotaxis in bacteria from both the biological and the mathematical perspectives. They discuss how the intersection of these perspectives has been useful for deciphering both the mechanisms and the core logic underlying navigation in bacteria. [ABSTRACT FROM AUTHOR]

Plant economics, the way plants allocate and utilize resources, affect multiple soil processes through interactions with root and associated microbial communities. However, the interplay between plant economics and microbial ecological strategies remains poorly understood, which is crucial for integrated manipulation of plant‐ and microbe‐mediated functions in mitigating climate change and sustaining soil health. We used a field experiment with 11 cover crop species grown monocultures in the same base soil to test whether microbial ecological strategies are associated with plant economic strategies and if their interactions are linked to soil functions. A principal component analysis (PCA) was performed on root and leaf traits to identify the loadings of cover crop species on the plant trait space. Metagenomic analysis of rhizosphere microbial communities was conducted to infer their ecological strategies based on genetically encoded community‐aggregated traits. We found a synchronous relationship between the conservation gradient of plant economic strategies and the trade‐offs in microbial ecological strategies. Conservative plant strategists, such as Lolium multiflorum, Triticum turgidum and Brassica juncea, fostered microbial communities characterized by high growth yield potentials (Y‐strategies). This included increased microbial carbon fixation pathways, citrate cycle, ribosome and valine, leucine and isoleucine biosynthesis. As a result, microbial metabolic efficiency improved, shown by higher microbial biomass carbon content and a lower metabolic quotient (qCO2), led to enhanced soil organic carbon accumulation. In comparison, acquisitive plants like Astragalus sinicus, Vicia villosa, Trifolium incarnatum and Medicago sativa stimulated microbial resource‐acquisition strategies (A‐strategies). This included enhanced bacterial chemotaxis, secretion systems, biotin metabolism and cell motility pathways, which in turn increased soil exoenzyme activity and accelerated soil nitrogen mineralization. Consequently, these species enhanced soil nitrogen availability and had substantial feedbacks on subsequent main crop productivity. Synthesis. This study demonstrates how plant economic strategies influence the balance between different microbial ecological strategies, specifically the trade‐offs in Y‐ and A‐strategies. These interactions exert control over carbon and nitrogen dynamics in the soil ecosystem. The findings provide insights for implementing nature‐based solutions to improve agroecosystem management practices. [ABSTRACT FROM AUTHOR]

In this paper, the following cross-diffusion system is investigated { u t = ∇ ⋅ ((u + 1) m ∇ u) − ∇ ⋅ (u (u + 1) β − 1 ∇ v (1 + | ∇ v | 2) α) + a − b u r , x ∈ Ω , t > 0 , 0 = Δ v − v + u , x ∈ Ω , t > 0 , in a bounded domain Ω ⊂ R n (n ≥ 2 ) with smooth boundary ∂ Ω . Under the condition that α > 2 n − m n − 2 2 (n − 1) , m ≥ 1 , and β ≤ m + 2 2 , it is shown that the problem possesses a unique global bounded classical solution. Moreover, it is obtained that the corresponding solution exponentially converge to a constant stationary solution when the initial data u 0 is sufficiently small. [ABSTRACT FROM AUTHOR]

As frontline cells, the precise recruitment of neutrophils is crucial for resolving inflammation and maintaining the homeostasis of the organism. Increasing evidence suggests the pivotal role of neutrophil chemotaxis in cancer progression and metastasis. Here, we collected clinical data and peripheral blood samples from patients with tumours to examine the alterations in the neutrophil quantity and chemotactic function using the Cell Chemotaxis Analysis Platform (CCAP). Transcriptome sequencing data of pan-cancer were obtained from The Cancer Genome Atlas (TCGA). Using the least absolute shrinkage and selection operator (LASSO) Cox regression model, we selected a total of 29 genes from 155 neutrophil- and chemotaxis-related genes to construct the ChemoScore model. Meanwhile, nomogram-based comprehensive model was established for clinical application. Furthermore, immunofluorescence (IF) staining was employed to assess the relationship between the neutrophils infiltrating and the survival outcomes of tumours. In this observational study, the chemotactic function of neutrophils was notably diminished in patients. The establishment and validation of ChemoScore suggested neutrophil chemotaxis to be a risk factor in most tumours, whereby higher scores were associated with poorer survival outcomes and were correlated with various immune cells and malignant biological processes. Moreover, IF staining of tumour tissue substantiated the adverse correlation between neutrophil infiltration and the survival of patients with lung adenocarcinoma (P = 0.0002) and colon adenocarcinoma (P = 0.0472). Taken together, patients with tumours demonstrated a decrease in chemotactic function. ChemoScore potentially prognosticates the survival of patients with tumours. Neutrophil chemotaxis provides novel directions and theoretical foundations for anti-tumour treatment. [ABSTRACT FROM AUTHOR]