Biology subjects

Pathak, A.

Publications and source records attributed to Pathak, A..

At least 55 records · Page 3Linked to original sources

bioRxiv2022

Acinetobacter baumannii defends against oxidative stress through a Mn2+-dependent small RNA-mediated suppression of type VI secretion system

Type VI secretion system (T6SS) is utilized by many Gram negative bacteria for eliminating competing bacterial species and manipulating host cells. Acinetobacter baumannii ATCC 17978 utilizes T6SS at the expense of losing pAB3 plasmid to induce contact-dependent killing of competitor microbes, resulting in the loss of antibiotic resistance carried by pAB3. However, the regulatory network associated with T6SS in A. baumannii remains poorly understood. Here, we identified an Mn2+-dependent post-transcriptional regulation of T6SS mediated by a bonafide small RNA, AbsR28. A. baumannii utilizes MumT (Mn2+-uptake inner membrane transporter) for the uptake of extracellular Mn2+ during oxidative stress. We demonstrate that the abundance of intracellular Mn2+ enables complementary base-pairing of AbsR28-tssM mRNA (that translated to TssM, one of the vital inner membrane components of T6SS), inducing RNase E-mediated degradation of tssM mRNA and resulting in T6SS repression. Thus, AbsR28 mediates a crosstalk between MumT and T6SS in A. baumannii. IMPORTANCESmall RNAs (sRNAs) are identified as critical components within the bacterial regulatory networks involved in fine regulation of virulence-associated factors. The sRNA-mediated regulation of Acinetobacter baumanniis T6SS was unchartered. Our findings reveal a novel underlying mechanism of an Mn2+-dependent sRNA-mediated regulation of T6SS in A. baumannii. We show that binding of Mn2+ to AbsR28 aids in the complementary base-pairing of AbsR28-tssM mRNA, resulting in RNase E-mediated processing of tssM and T6SS repression. The findings also shed light on A. baumanniis preference for antibiotic resistance over contact-dependent killing during infection.

microbiology↗

bioRxiv2022

Restoration of PITPNA in Type 2 diabetic human islets reverses pancreatic beta-cell dysfunction

Defects in insulin processing and granule maturation are linked to pancreatic beta-cell failure during type 2 diabetes (T2D). Phosphatidylinositol transfer protein alpha (PITPNA) stimulates activity of phosphatidylinositol (PtdIns) 4-OH kinase to produce sufficient PtdIns-4-phosphate (PtdIns-4-P) in the trans-Golgi network to promote insulin granule maturation. PITPNA in beta-cells of T2D human subjects is markedly reduced suggesting its depletion accompanies beta-cell dysfunction. Conditional deletion of Pitpna in the beta-cells of Ins-Cre;Pitpnaflox/flox mice leads to hyperglycemia resulting from decreased glucose-stimulated insulin secretion (GSIS) and reduced pancreatic beta-cell mass. Furthermore, PITPNA silencing in human islets confirmed its role in PtdIns-4-P synthesis and led to impaired insulin granule maturation and docking, GSIS, and proinsulin processing with evidence of ER stress. Restoration of PITPNA in islets of T2D human subjects reversed these beta-cell defects and identify PITPNA as a critical target linked to beta-cell failure in T2D.

cell biology↗

bioRxiv2022

Nuclear export inhibition jumbles epithelial-mesenchymal states and gives rise to migratory disorder in healthy epithelia

Epithelial-mesenchymal (E-M) phenotypes govern collective cellular behaviors to facilitate diverse tissue functions, including embryogenesis, wound healing, and cancer invasion. Cellular E-M state is regulated by dynamic nucleocytoplasmic transport of corresponding E-M factors; yet, it remains unknown how concurrently trapping these factors affects epithelia at the macroscale. To explore this question, we performed nuclear export inhibition (NEI) via Leptomycin B treatment, which biases nuclear localization of CRM1- associated E-M factors. We examined changes in collective cell migration across a range of substrate stiffnesses. Our results show that NEI fosters an atypical E-M state wherein cells concurrently strengthen intercellular adhesions and develop mechanoactive characteristics. Following NEI, soft substrates elevate collective migration for up to 24 h, while stiffer substrates reduce migration at all timepoints. We demonstrate that excluding Yes-associated protein 1 from NEI shifts affected cells toward an epithelial phenotype. Meanwhile, removing -catenin maintains NEIs intercellular adhesion strengthening and mechanoactivation capabilities, but prevents mechanoactive characteristics from reaching collective behavior. Overall, our results show that NEI disrupts epithelial migration through competition between intercellular adhesions, mechanoactivation, and cell-cell coordination. Ultimately, these findings of mechanoactive NEI outcomes for healthy cells could warrant additional investigation in the context of NEI-centered cancer therapies.

biophysics↗

bioRxiv2022

A Cdh3-Lam332 signaling axis in a leader cell subpopulation controls protrusion dynamics and tumor organoid collective migration

Carcinoma dissemination can occur when heterogeneous tumor and tumor stromal cells clusters migrate together via collective migration. Cells at the front lead and direct collective migration, yet how these leader cells form and interact with the microenvironment to direct migration are not fully appreciated. From live videos of primary mouse and human breast tumor organoids in a 3D microfluidic system that mimics the native breast tumor microenvironment, we developed 3D computational models which hypothesize that leader cells generate high protrusive forces and overcome extracellular matrix (ECM) resistance. Using single cell sequencing, we reveal leader cells are heterogeneous, and identify and isolate a unique Cadherin-3 (Cdh3) positive leader cell subpopulation that is necessary and sufficient to lead migration. Cdh3 controls leader cell protrusion dynamics through the local production of Laminin-332 which is required for integrin/focal adhesion function. Our findings highlight how a subset of leader cells interact with the microenvironment to direct collective migration. TeaserHigher protrusions of Cdh3+ leader cells polarize tumor organoids that then invade collagen via Lam332 adhesion feedback.

cancer biology↗

bioRxiv2022

Mechanically primed cells transfer memory to fibrous matrices for persistent invasion

In disease and development, cells sense and migrate across mechanically dissimilar environments. We investigated whether mechanical memory of past environments empowers cells to navigate new, three-dimensional environments. Here, we show that cells primed by stiff matrices apply higher forces, compared to soft-primed cells, to accumulate and align collagen fibers towards sustained invasion. This priming advantage persists in dense or stiffened collagen. Through an energy-minimization model, we elucidate how memory-laden cells overcome mechanosensing of softer or challenging environments via a cell-matrix transfer of memory. Consistent with model predictions, depletion of -catenin and YAP hamper coordinated forces and cellular memory required for collagen remodeling before invasion. We release tension in collagen fibers via laser ablation and disable fiber remodeling by lysyl-oxidase inhibition; both of which disrupt cell-to-matrix transfer of memory and reduce invasion. These results have implications for cancer, fibrosis, and aging, where potential matrix memory may generate prolonged cellular response. One-Sentence SummaryCell invasion across mechanically dissimilar environments is mediated by force-based storage and extraction of cell and matrix memory.

biophysics↗

bioRxiv2022

Multiscale obstruction sensitivity in collective cell migration

Cellular forces and intercellular cooperation generate collective cell migration. Pathological changes in cell-level genetic and physical properties cause jamming, unjamming, and scattering in epithelial migration. Separately, changes in microenvironment stiffness and confinement can produce varying modes of cell migration. However, it remains unclear whether and how mesoscale disruptions in matrix topology alter collective cell migration. To address this question, we microfabricated matrices with stumps of defined geometry, density, and orientation, which serve as obstructions in the path of collectively migrating healthy mammary epithelial cells. Here, we show that cells lose their speed and directionality when moving through dense obstructions, compared to those sparsely spaced. On flat surfaces, leader cells are significantly stiffer than follower cells, while dense obstructions lead to the overall softening of cells. In moving through dense obstructions, epithelial cells lose the sense of leaders and followers in their physical properties, migration phenotypes, and fluidity. Although Rac inhibition reduces obstruction sensitivity, loss of cell-cell cooperation and induction of leader-like phenotype via -catenin depletion eliminates the effect of matrix obstructions on epithelial migration. Through a lattice-based model, we identify cellular protrusions, polarity, and leader-follower communication as key mechanisms for obstruction-sensitive collective cell migration. Together, microscale cytoskeletal response, mesoscale softening and disorder, and macroscale multicellular communication enable epithelial cell populations to sense topological obstructions encountered in challenging environments. These results reveal that cohesive, healthy populations are more obstruction sensitive than the dysfunctional, aggressive ones. The obstruction-sensitivity could add to the emerging disease mechanotypes such as cell stiffness and traction forces.

biophysics↗

bioRxiv2021

Therapeutic potential of methylxanthine drug on alpha synuclein protein in Parkinson's disease

Parkinsons disease (PD) is the second most common neurodegenerative disorder after Alzheimer. It exists in sporadic (90 to 95%) and familial (5 to 10%) form. Its pathogenesis is due to oxidative stress, glutamate excitotoxicity, protein aggregation, neuroinflammation and neurodegeneration. There is currently no cure for this disease. The protein-protein interaction and gene ontology/functional enrichment analysis have been performed to find out the prominent interactor protein and shared common biological pathways, especially PD pathway. Further in silico docking analysis was performed on target protein to investigate the prominent drug molecule for PD. Through computational molecular virtual screening of small molecules from selected twelve natural compounds, and among these compounds methylxanthine was shown to be prominent inhibitor to SNCA protein that ultimately prevent PD. The interaction of methylxanthine compound with the target protein SNCA suggested that, it interacted with prominent binding site with good docking score and might be involved in blocking the binding of neuroinducing substances like: 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to SNCA protein. Thus methylxanthine compounds can be explored as promising drugs for the prevention of Parkinsons disease.

bioinformatics↗

bioRxiv2021

Preservation of neural synchrony at peak alpha frequency via global synaptic scaling compensates for white matter structural decline over adult lifespan

We propose that preservation of functional integration, estimated from measures of neural synchrony, is a key neurocompensatory mechanism associated with healthy human ageing. To support this proposal, we demonstrate how phase-locking at peak alpha frequency from Magnetoencephalography (MEG) data is invariant over lifespan in a large cohort of human participants, aged 18-88 years. Using empirically derived connection topologies from diffusion tensor imaging (DTI) data, we create an in-silico model of whole-brain alpha dynamics. We show that enhancing inter-areal coupling can cancel the effect of increased axonal transmission delay associated with age-related degeneration of white matter tracts and thus, preserve neural synchrony. Together with analytical solutions for non-biological all-to-all connection scenarios, our model establishes the theoretical principles by which frequency slowing with age, frequently observed in the alpha band in diverse populations, can be viewed as an epiphenomenon of the underlying neurocompensatory mechanisms.

neuroscience↗

bioRxiv2021

Dynamic Self-Reinforcement of Gene Expression Determines Acquisition and Retention of Cellular Mechanical Memory

Mechanotransduction describes activation of gene expression by changes in the cells physical microenvironment. Recent experiments show that mechanotransduction can lead to long-term "mechanical memory", where cells cultured on stiff substrates for sufficient time (priming phase) maintain altered phenotype after switching to soft substrates (dissipation phase), as compared to unprimed controls. The timescale of memory acquisition and retention is orders of magnitude larger than the timescale of mechanosensitive cellular signaling, and memory retention time changes continuously with priming time. We develop a model that captures these features by accounting for positive reinforcement in mechanical signaling. The sensitivity of reinforcement represents the dynamic transcriptional state of the cell composed of protein lifetimes and 3D chromatin organization. Our model provides a single framework connecting microenvironment mechanical history to cellular outcomes ranging from no memory to terminal differentiation. Predicting cellular memory of environmental changes can help engineer cellular dynamics through changes in culture environments.

systems biology↗

bioRxiv2021

A rigorous framework for detecting SARS-CoV-2 spike protein mutational ensemble from genomic and structural features

The recent release of SARS-CoV-2 genomic data from several countries has provided clues into the potential antigenic drift of the coronavirus population. In particular, the genomic instability observed in the spike protein necessitates immediate action and further exploration in the context of viralhost interactions. By temporally tracking 527,988 SARS-CoV-2 genomes, we identified invariant and hypervariable regions within the spike protein. We evaluated combination of mutations from SARS-CoV-2 lineages and found that maximum number of lineage-defining mutations were present in the N-terminal domain (NTD). Based on mutant 3D-structural models of known Variants of Concern (VOCs), we found that structural properties such as accessibility, secondary structural type, and intra-protein interactions at local mutation sites are greatly altered. Further, we observed significant differences between intra-protein networks of wild-type and Delta mutant, with the latter showing dense intra-protein contacts. Extensive molecular dynamics simulations of D614G mutant spike structure with hACE2 further revealed dynamic features with 47.7% of mutations mapping on flexible regions of spike protein. Thus, we propose that significant changes within spike protein structure have occurred that may impact SARS-CoV-2 pathogenesis, and repositioning of vaccine candidates is required to contain the spread of COVID-19 pathogen.

genomics↗

bioRxiv2020

14-3-3s reduce propagation and toxicity of pathologic alpha-synuclein in the in vivo preformed fibril model

Alpha-synuclein (syn) is the key component of proteinaceous aggregates termed Lewy Bodies (LBs) that pathologically define a group of disorders known as synucleinopathies, including Parkinsons Disease (PD) and Dementia with Lewy Bodies (DLB). Syn is hypothesized to misfold and spread throughout the brain in a prion-like fashion. Transmission of syn necessitates the release of misfolded syn from one cell and the uptake of that syn by another, in which it can template the misfolding of endogenous syn upon cell internalization. 14-3-3 proteins are a family of highly expressed brain proteins that are neuroprotective in multiple PD models. We have previously shown that 14-3-3{theta} acts as a chaperone to reduce syn aggregation, cell-to-cell transmission, and neurotoxicity in the in vitro pre-formed fibril (PFF) model. In this study, we expanded our studies to test the impact of 14-3-3s on syn toxicity in the in vivo syn PFF model. We used both transgenic expression models and adenovirus associated virus (AAV)-mediated expression to examine whether 14-3-3 manipulation impacts behavioral deficits, syn aggregation, and neuronal loss in the PFF model. 14-3-3{theta} transgene overexpression in cortical and amygdala regions rescued social dominance deficits induced by PFFs at 6 months post injection, whereas 14-3-3 inhibition by transgene expression of the competitive 14-3-3 peptide inhibitor difopein in the cortex and amygdala accelerated social dominance deficits. The behavioral rescue by 14-3-3{theta} overexpression was associated with delayed syn aggregation induced by PFFs in these brain regions. Conversely, 14-3-3 inhibition by difopein in the cortex and amygdala accelerated syn aggregation and cortical pyramidal neuron loss induced by PFFs. 14-3-3{theta} overexpression by AAV in the substantia nigra (SN) also delayed syn aggregation in the SN and partially rescued PFF-induced dopaminergic cell loss in the SN. 14-3-3 inhibition in the SN accelerated nigral syn aggregation and increased PFF-induced dopaminergic cell loss. These data indicate a neuroprotective role for 14-3-3{theta} against syn toxicity in vivo.

neuroscience↗

bioRxiv2020

Rab27 GTPases regulate alpha-synuclein uptake, cell-to-cell 1 transmission, and toxicity

Parkinsons disease and Dementia with Lewy Bodies are two common neurodegenerative disorders marked by proteinaceous aggregates composed primarily of the protein -synuclein. -Synuclein is hypothesized to have prion-like properties, by which misfolded -synuclein induces the pathological aggregation of endogenous -synuclein and neuronal loss. Rab27a and Rab27b are two highly homologous Rab GTPases that regulate -synuclein secretion, clearance, and toxicity in vitro. In this study, we tested the impact of Rab27a/b on the transmission of pathogenic -synuclein. Double knockout of both Rab27 isoforms eliminated -synuclein aggregation and neuronal toxicity in primary cultured neurons exposed to fibrillary -synuclein. In vivo, Rab27 double knockout mice lacked fibril-induced -synuclein inclusions, dopaminergic neuron loss, and behavioral deficits seen in wildtype mice with fibril-induced inclusions. Studies using AlexaFluor488-labeled -synuclein fibrils revealed that Rab27a/b knockout prevented -synuclein internalization without affecting bulk endocytosis. Rab27a/b knockout also blocked the cell-to-cell spread of -synuclein pathology in multifluidic, multichambered devices. This study provides critical insight into the role of Rab GTPases in Parkinsons disease and identifies Rab27s as key players in the progression of synucleinopathies.

neuroscience↗

bioRxiv2020

Sex, Age, and Parental Harmonic Convergence Behavior Affect the Immune Performance of Aedes aegypti Offspring

Aedes aegypti is an important vector of several pathogenic arboviruses including dengue, chikungunya and Zika. Innovative approaches to control Aedes populations, involving synthetic transgenic modifications as well as Wolbachia bacteria, appear promising. For the various techniques requiring offspring inheritance of a trait, released males must successfully compete for mating partners against wildtype males. However, very little is known about mechanisms of mate selection in mosquitoes in general and in particular about potential correlations between mating success and offspring immune performance. Harmonic convergence signals have been proposed as a cue for females to predict male quality. We investigated whether offspring of converging parental pairs showed differences in immune competence compared to offspring derived from non-converging parental pairs using three different types of immune assays. We found that offspring immune responses (melanization response and response to a bacterial challenge) differed between offspring from converging and non-converging parents. However, immune responses were shaped by several interacting factors such as sex, age, reproductive status, and parental mating behavior. Parental mating behavior had a stronger effect on the immune response of male offspring than on female offspring. Further, a population of female offspring derived from converging parental pairs reached their peak dengue virus dissemination rate earlier compared to a population of offspring derived from non-converging parental pairs. Our results provide insight into a wide range of selective pressures shaping mosquito immune function. Evolutionary trade-offs between naturally and sexually selected traits can have important implications for disease transmission and control and should be considered in the development of reproductive control strategies.

ecology↗

bioRxiv2020

Deletion of FUNDC2 and CMC4 on chromosome Xq28 is sufficient to cause hypergonadotropic hypogonadism in men

BackgroundHypergonadotropic hypogonadism (HH) is characterized by low sex steroid levels and secondarily elevated gonadotropin levels with either congenital or acquired etiology. Genetic factors leading to HH have yet to be fully elucidated. MethodsHere, we report on genome and transcriptome data analyses from a male patient with HH and history of growth delay who has an inherited deletion of chromosome Xq28. Furthermore, expression analyses were done for this patient and his unaffected family members and compared to normal controls to identify dysregulated genes due to this deletion. ResultsOur patients Xq28 deletion is 44,806bp and contains only two genes FUNDC2 and CMC4. Expression of both FUNDC2 and CMC4 are completely abolished in the patient. Gene ontology analyses of differentially expressed genes in the patient in comparison to controls show that significantly up-regulated genes in the patient are enriched in Sertoli cell barrier regulation, apoptosis, inflammatory response and gonadotropin-releasing regulation. Indeed, our patient has an elevated FSH level, which regulates Sertoli cell proliferation and spermatogenesis. In his mother and sister, who are heterozygous for this deletion, X-chromosome inactivation is skewed towards the deleted X, suggesting a mechanism to avoid FSH dysregulation. ConclusionCompared to the previously reported men with variable sized Xq28 deletions, our study suggests that loss of function of FUNDC2 and/or CMC4 results in dysregulation of apoptosis, inflammation and FSH, and is sufficient to cause Xq28-associated HH.

genomics↗

bioRxiv2020

Mechanical memory in cells emerges from mechanotransduction with transcriptional feedback and epigenetic plasticity

Emerging evidence shows that cells are able to sense and store a memory of their past mechanical environment. Since existing mechanotransduction models are based on adhesion and cytoskeletal dynamics that occurs over seconds and minutes, they do not capture memory observed over days or weeks. We postulate that transcriptional activity and epigenetic plasticity, upstream of adhesion-based signaling, need to be invoked to explain long-term mechanical memory. Here, we present a theory for mechanical memory in cells governed by three key components. First, cells on a stiff matrix are primed by a transcriptional reinforcement of cytoskeletal signaling. Second, longer stiff-priming progressively produces more memory-regulating factors and reduces epigenetic plasticity. Third, when stiff-primed cells move to soft matrix, the reduced epigenetic plasticity blocks new transcription required for cellular adaptation to the new matrix. This stalled transcriptional state gives rise to memory. We validate this model against previous experimental findings of memory storage and decay in epithelial cell migration and stem cell differentiation. We also predict wide-ranging memory responses for different cell types of varying protein kinetics and priming conditions. This theoretical framework for mechanical memory expands the timescales of mechanotransduction captured by conventional models by integrating cytoskeletal signaling with transcriptional activity and epigenetic plasticity. Our model predictions explain mechanical memory and propose new experiments to test spatiotemporal regulation of cellular memory in diverse contexts ranging from cell differentiation to migration and growth.

biophysics↗

bioRxiv2020

Histogenesis of the reticulum of non- descript goat (Capra hircus) of India

The study was conducted on 36 developing reticulum from healthy and normal embryos/ foeti of Indian goat. Embryos/foeti were assigned into three groups. Histo-differentiation of reticulum of goat stomach took place at 38 days of gestation. The wall of foetal reticulum was made up of three strata i. e. epithelium, pleuripotent blastemic tissue and serosa up to 49 days of fetal age and definite four layers viz. epithelium, propria-submucosa, tunica muscularis and serosa were observed first at 51 days of gestation. Upto 100 days of gestation the reticulum was lined by undifferentiated stratified epithelium and thereafter gradually transformed into stratified squamous epithelium. Keratinization was noticed at term. Primary and secondary reticular crests made their appearance at 60 and 112 days of gestation, respectively. Corial papillae were detected in primary and secondary reticular crests at 121 and 145 days of gestation, respectively. Near term, the core of the reticular crest also contained muscularis mucosae in its proximal 1/3rd region while core of the corial papillae contained only lamina propria. Reticular, collagen and elastic fibers came into sight at 46, 100 and 134 days of gestation, respectively. Summary statementThe study was conducted on intrauterine reticulum of Indian goat. From this study it can be concluded that the histogenesis of reticulum was almost completed in prenatal life. However, to become functional it still required more time as the relative sizes of reticulum and process of keratinization were yet to be completed.

developmental biology↗

bioRxiv2019

Ephrin-B1 blocks adult cardiomyocyte proliferation and heart regeneration

AimsDeciphering the innate mechanisms governing the blockade of proliferation in adult cardiomyocytes (CMs) is challenging for mammalian heart regeneration. Despite the exit of CMs from the cell cycle during the postnatal maturation period coincides with their morphological switch to a typical adult rod-shape, whether these two processes are connected is unknown. Here, we examined the role of ephrin-B1, a CM rod-shape stabilizer, in adult CM proliferation and cardiac regeneration.\n\nMethods and resultsTransgenic- or AAV9-based ephrin-B1 repression in adult mouse heart led to substantial proliferation of resident CMs and tissue regeneration to compensate for apex resection, myocardial infarction (MI) and senescence. Interestingly, in the resting state, CMs lacking ephrin-B1 did not constitutively proliferate, indicative of no major cardiac defects. However, they exhibited proliferation-competent signature, as indicated by higher mononucleated state and a dramatic decrease of miR-195 mitotic blocker, which can be mobilized under neuregulin-1 stimulation in vitro and in vivo. Mechanistically, the post-mitotic state of the adult CM relies on ephrin-B1 sequestering of inactive phospho-Yap1, the effector of the Hippo-pathway, at the lateral membrane. Hence, ephrin-B1 repression leads to phospho-Yap1 release in the cytosol but CM quiescence at resting state. Upon cardiac stresses (apectomy, MI, senescence), Yap1 could be activated and translocated to the nucleus to induce proliferation-gene expression and consequent CM proliferation\n\nConclusionsOur results identified ephrin-B1 as a new natural locker of adult CM proliferation and emphasize that targeting ephrin-B1 may prove a future promising approach in cardiac regenerative medicine for HF treatment.\n\nSignificanceThe mammalian adult heart is unable to regenerate due to the inability of cardiomyocytes (CMs) to proliferate and replace cardiac tissue lost. Exploiting CM-specific transgenic mice or AAV9-based gene therapy, this works identifies ephrin-B1, a specific rod-shape stabilizer of the adult CM, as a natural padlock of adult CM proliferation for compensatory adaptation to different cardiac stresses (apectomy, MI, senescence), thus emphasizing a new link between the adult CM morphology and their proliferation potential. Moreover, the study demonstrates proof-of-concept that targeting ephrin-B1 may be an innovative therapeutic approach for ischemic heart failure.

physiology↗

bioRxiv2019

Meningitis pathogens evade immune responses by thermosensing

Bacterial meningitis is a major cause of death and disability in children worldwide. Two human restricted pathogens, Streptococcus pneumoniae and Haemophilus influenzae, are the major causative agents of bacterial meningitis, attributing to 200,000 deaths annually. These pathogens are often part of the nasopharyngeal microflora of healthy carriers. However, what factors elicit them to disseminate and cause invasive diseases remain unknown. Elevated temperature and fever are hallmarks of inflammation triggered by infections and can act as warning signal to these pathogens. Here, we investigate whether these pathogens could sense environmental temperature to evade host complement-mediated killing. We show that expression of two vital virulence factors and vaccine components, the capsule and factor H binding proteins, are temperature dependent. We identify and characterize four novel RNA thermosensors in S. pneumoniae and H. influenzae within their 5'-untranslated regions of genes, responsible for capsular biosynthesis and production of factor H binding proteins. Our data further demonstrate that these pathogens have co-evolved thermosensing abilities independently with unique RNA sequences, but distinct secondary structures, to evade the human immune system.\n\nAuthor SummaryStreptococcus pneumoniae and Haemophilus influenzae are bacteria that reside in the upper respiratory tract. This harmless colonization may progress to severe and often lethal septicaemia and meningitis, but molecular mechanisms that control why these pathogens invade the circulatory system remain largely unknown. Here we show that both S. pneumoniae and H. influenzae can evade complement killing by sensing the temperature of the host. We identify and characterize four novel RNA thermosensors in S. pneumoniae and H. influenzae within their respective 5'-untranslated regions of genes, influencing capsular biosynthesis and production of factor H binding proteins. Moreover, we show that these RNA thermosensors evolved independently with exclusive unique RNA sequences to sense the temperature in the nasopharynx and in other body sites to avoid immune killing. Our finding that regulatory RNA senses temperatures and directly regulate expression of two important virulence factors and vaccine components of S. pneumoniae and H. influenzae, is most important for our understanding of bacterial pathogenesis and for vaccine development. Our work could pave the way for similar studies in other important bacterial pathogens and enables clinicians and microbiologists to adjust their diagnostic techniques, and treatments to best fit the condition of the patients.

microbiology↗