Loss Of Motility Research Articles

Undocking of an extensive ciliary network induces proteostasis and cell fate switching resulting in severe primary ciliary dyskinesia.

Primary ciliary dyskinesia is a rare monogenic syndrome that is associated with chronic respiratory disease, infertility, and laterality defects. Although more than 50 genes causative of primary ciliary dyskinesia have been identified, variants in the genes encoding coiled-coil domain-containing 39 (CCDC39) and CCDC40 in particular cause severe disease that is not explained by loss of ciliary motility alone. Here, we sought to understand the consequences of these variants on cellular functions beyond impaired motility. We used human cells with pathogenic variants in CCDC39 and CCDC40, Chlamydomonas reinhardtii genetics, cryo-electron microscopy, and proteomics to define perturbations in ciliary assembly and cilia stability, as well as multiple motility-independent pathways. Analysis of proteomics of cilia from patient cells identified that the absence of the axonemal CCDC39/CCDC40 heterodimer resulted in the loss of a network of more than 90 ciliary structural proteins, including 14 that were defined as ciliary address recognition proteins, which provide docking for the missing structures. The absence of the network impaired microtubule architecture, activated cell quality control pathways, switched multiciliated cell fate to mucus-producing cells and resulted in a defective periciliary barrier. In CCDC39 variant cells, these phenotypes were reversed through expression of a normal CCDC39 transgene. These findings indicate that the CCDC39/CCDC40 heterodimer functions as a scaffold to support the assembly of an extensive network of ciliary proteins, whose loss results in both motility-dependent and motility-independent phenotypes that may explain the severity of disease. Gene therapy might be a potential treatment option to be explored in future studies.

Порушення іонтранспортувальних процесів у сперматозоїдах неплідних чоловіків

During the study of the plasma membrane of spermatozoa and its organelles, a great variety of specifically localized ion channels, exchangers, and ATPases was discovered. Although the activity of ion channels and membrane transporters has been studied in detail, their involvement in the mechanisms leading to the dysfunction of male germ cells remains insufficiently elucidated. Numerous scientific works show that the absence of certain transport systems of the plasma membrane due to genetic mutations or their low activity leads to a decrease or loss of sperm motility, morphological changes that worsen the quality of sperm, and is the cause of male infertility. The review examines some ion transport systems that maintain resting membrane potential and ion homeostasis in spermatogenesis. It notes the possibility of using ion channels and membrane transporters as markers to establish the functionality of spermatozoa or as molecular targets for drugs in the treatment of male infertility.

Distribution and functional significance of KLF15 in mouse cerebellum

Kruppel-like factor 15 (KLF15), a member of the KLF family, is closely involved in many biological processes. However, the mechanism by which KLF15 regulates neural development is still unclear. Considering the complexity and importance of neural network development, in this study, we investigated the potent regulatory role of KLF15 in neural network development. KLF15 was detected highly expressed in the cerebellum and enriched in Purkinje cells, with a significant increase in KLF15 expression between 15 and 20 days of neural development. Knockdown of KLF15 led to loss of Purkinje cells and impaired motility in mice. Therefore, our study aims to elucidate the relationship between KLF15 and Purkinje cells in mice, may provide a new research idea for the developmental mechanism of the mouse cerebellum.

Motile cilia modulate neuronal and astroglial activity in the zebrafish larval brain.

The brain uses a specialized system to transport cerebrospinal fluid (CSF), consisting of interconnected ventricles lined by motile ciliated ependymal cells. These cells act jointly with CSF secretion and cardiac pressure gradients to regulate CSF dynamics. To date, the link between cilia-mediated CSF flow and brain function is poorly understood. Using zebrafish larvae as a model system, we identify that loss of ciliary motility does not alter progenitor proliferation, brain morphology, or spontaneous neural activity despite leading to an enlarged telencephalic ventricle. We observe altered neuronal responses to photic stimulations in the optic tectum and hindbrain and brain asymmetry defects in the habenula. Finally, we investigate astroglia since they contact CSF and regulate neuronal activity. Our analyses reveal a reduction in astroglial calcium signals during both spontaneous and light-evoked activity. Our findings highlight a role of motile cilia in regulating brain physiology through the modulation of neural and astroglial networks.

The pyrethroid insecticide deltamethrin disrupts neuropeptide and monoamine signaling pathways in the gastrointestinal tract.

Enteroendocrine cells (EECs) are a rare cell type of the intestinal epithelium. Various subtypes of EECs produce distinct repertoires of monoamines and neuropeptides which modulate intestinal motility and other physiologies. EECs also possess neuron-like properties, suggesting a potential vulnerability to ingested environmental neurotoxicants. One such group of toxicants are pyrethroids, a class of prevalent insecticides used residentially and agriculturally. Pyrethroids agonize voltage-gated sodium channels (VGSCs), inducing neuronal excitotoxicity, and affect the function of monoamine-producing neurons. Given their anatomical location at the interface with the environment and their expression of VGSCs, EECs likely represent a vulnerable cell-type to oral pyrethroid exposure. In this study, we used the EEC cell line, STC-1 cells, to evaluate the effects of the common pyrethroid deltamethrin on the functional status of EECs. We find that deltamethrin impacts both expression of serotonergic pathways and inhibits the adrenergic-evoked release of an EEC hormone, GLP-1, in vitro . In a mouse model of oral exposure, we found that deltamethrin induced an acute, yet transient, loss of intestinal motility, in both fed and fasted conditions. This constipation phenotype was accompanied by a significant decrease in peripheral serotonin production and an inhibition of nutrient-evoked intestinal hormone release. Together, these data demonstrate that deltamethrin alters monoaminergic signaling pathways in EECs and regulates intestinal motility. This work demonstrates a mechanistic link between pyrethroid exposure and intestinal impacts relevant to pyrethroid-associated diseases, including inflammatory bowel disease, neurodegenerative disease, and metabolic disorders.

Influence of Flagella on Salmonella Enteritidis Sedimentation, Biofilm Formation, Disinfectant Resistance, and Interspecies Interactions.

Flagella are essential for bacterial motility and biofilm formation by aiding bacterial attachment to surfaces. However, the impact of flagella on bacterial behavior, particularly biofilm formation, remains unclear. This study constructed two flagellar mutation strains of Salmonella Enteritidis (SE), namely, SE-ΔflhD and SE-ΔflgE, and confirmed the loss of flagellar structures and motility in these strains. The mutant strains exhibited growth comparable with the wild-type (WT) strain but had higher sedimentation rates. Biofilm biomass did not differ significantly between the WT and mutant strains, except for SE-ΔflgE at 3 d. SE-ΔflgE showed increased susceptibility to sodium hypochlorite compared to the WT. The co-sedimentation rate of flagella-deficient strains was lower than the WT, and the biomass of dual-species biofilm formed by Bacillus paramycoides B5 with SE-ΔflhD or SE-ΔflgE was significantly lower than with the WT. These findings emphasize the significance of SE flagella in biofilm formation and interspecies interactions, offering insights into targeted biofilm prevention and control measures.

Flagellar motility and the mucus environment influence aggregation mediated antibiotic tolerance of Pseudomonas aeruginosa in chronic lung infection.

Antibiotic recalcitrance of chronic Pseudomonas aeruginosa infections in muco-obstructive airway diseases is a primary driver of mortality. Mechanisms that drive antibiotic tolerance are poorly understood. We investigated motility phenotypes related to P. aeruginosa adaptation and antibiotic tolerance in the diseased mucus environment. Loss of flagellar motility drives antibiotic tolerance by promoting aggregate formation. Regulation of flagellar motility appears to be a key step in aggregate formation as the inability to turn off flagellin expression resulted in poor aggregate formation and increased antibiotic susceptibility. These results deepen our understanding of the formation of antibiotic tolerant aggregates within the MADs airway and opens novel avenues and targets for treatment of chronic P. aeruginosa infections.

Synergistic phenotypic adaptations of motile purple sulphur bacteria Chromatium okenii during lake-to-laboratory domestication.

Isolating microorganisms from natural environments for cultivation under optimized laboratory settings has markedly improved our understanding of microbial ecology. Artificial growth conditions often diverge from those in natural ecosystems, forcing wild isolates into distinct selective pressures, resulting in diverse eco-physiological adaptations mediated by modification of key phenotypic traits. For motile microorganisms we still lack a biophysical understanding of the relevant traits emerging during domestication and their mechanistic interplay driving short-to-long-term microbial adaptation under laboratory conditions. Using microfluidics, atomic force microscopy, quantitative imaging, and mathematical modeling, we study phenotypic adaptation of Chromatium okenii, a motile phototrophic purple sulfur bacterium from meromictic Lake Cadagno, grown under laboratory conditions over multiple generations. Our results indicate that naturally planktonic C. okenii leverage shifts in cell-surface adhesive interactions, synergistically with changes in cell morphology, mass density, and distribution of intracellular sulfur globules, to suppress their swimming traits, ultimately switching to a sessile lifeform. A computational model of cell mechanics confirms the role of such phenotypic shifts in suppressing the planktonic lifeform. By investigating key phenotypic traits across different physiological stages of lab-grown C. okenii, we uncover a progressive loss of motility during the early stages of domestication, followed by concomitant deflagellation and enhanced surface attachment, ultimately driving the transition of motile sulfur bacteria to a sessile state. Our results establish a mechanistic link between suppression of motility and surface attachment via phenotypic changes, underscoring the emergence of adaptive fitness under laboratory conditions at the expense of traits tailored for natural environments.

EbsA is essential for both motility and biofilm formation in the filamentous cyanobacterium Nostoc punctiforme.

Many cyanobacteria, both unicellular and filamentous, exhibit surface motility driven by type IV pili (T4P). While the component parts of the T4P machinery described in other prokaryotes are largely conserved in cyanobacteria, there are also several T4P proteins that appear to be unique to this phylum. One recently discovered component is EbsA, which has been characterized in two unicellular cyanobacteria. EbsA was found to form a complex with other T4P proteins and is essential for motility. Additionally, deletion of ebsA in one of these strains promoted the formation of biofilms. To expand the understanding of ebsA in cyanobacteria, its role in motility and biofilm formation were investigated in the model filamentous cyanobacterium Nostoc punctiforme. Expression of ebsA was strictly limited to hormogonia, the motile filaments of N. punctiforme. Deletion of ebsA did not affect hormogonium development but resulted in the loss of motility and the failure to accumulate surface pili or produce hormogonium polysaccharide (HPS), consistent with pervious observations in unicellular cyanobacteria. Protein-protein interaction studies indicated that EbsA directly interacts with PilB, and the localization of EbsA-GFP resembled that previously shown for both PilB and Hfq. Collectively, these results support the hypothesis that EbsA forms a complex along with PilB and Hfq that is essential for T4P extension. In contrast, rather than enhancing biofilm formation, deletion of both ebsA and pilB abolish biofilm formation in N. punctiforme, implying that distinct modalities for the relationship between motility, T4P function and biofilm formation may exist in different cyanobacteria.

Flagellum-deficient Pseudomonas aeruginosa is more virulent than non-motile but flagellated mutants in a cystic fibrosis mouse model.

Loss of the flagellum marks the pathoadaptation of Pseudomonas aeruginosa to the cystic fibrosis (CF) airway environment during lung disease. Losing the flagellum is advantageous to the bacterium as the flagellum can be recognized by immune cells. The primary purpose of the flagellum is, however, to provide motility to the bacterium. Our goal was to determine whether the loss of flagellar motility or the loss of flagellum expression contributes to P. aeruginosa lung infection in CF. To address this, wild-type and gut-corrected FABP-human cystic fibrosis transmembrane conductance regulator (hCFTR) mice deficient in the murine Cftr gene were infected intratracheally with lethal doses of wild-type or flagellum-deficient P. aeruginosa. While there was no significant difference in the survival of wild-type mice after infection with either of the bacterial strains, a significantly higher mortality was observed in FABP-hCFTR mice infected with flagellum-deficient P. aeruginosa, compared to mice infected with their flagellated counterparts. When FABP-hCFTR mice were infected with isogenic, motility-deficient flagellated mutants, animal survival and lung bacterial titers were similar to those observed in mice infected with the wild-type bacterium. Airway levels of neutrophils and the amount neutrophil elastase were similar in mice infected with either the wild-type bacteria or the flagellum-deficient P. aeruginosa. Our results show that FABP-hCFTR mice have a different response to flagellum loss in P. aeruginosa compared to wild-type animals. The loss of flagellum expression, rather than the loss of motility, is the main driver behind the increased virulence of flagellum-deficient P. aeruginosa in CF. These observations provide new insight into P. aeruginosa virulence in CF.IMPORTANCEPseudomonas aeruginosa, a major respiratory pathogen in cystic fibrosis, is known to lose its flagellum during the course of infection in the airways. Here, we show that the loss of flagellum leads to a more enhanced virulence in Cftr-deficient cystic fibrosis mice than in control animals. Loss of flagellum expression, rather than the loss of flagellar swimming motility, represents the main driver behind this increased virulence suggesting that this appendage plays a specific role in P. aeruginosa virulence in cystic fibrosis airways.

Anthelmintic Activity of Alcoholic Leaf Extract of Tectona grandis

Background: Helminthiasis is a major concern in the livestock sector due to the immense afflictions in the production and economy of the farmer. Chemical anthelmintics are used to combat them and parasites are acquiring resistance against these drugs. Hence, the development of new drugs or alternatives is the need of the hour for combating such infestations. This study was undertaken to determine the effect of methanolic leaf extract of Tectona grandis on strongyles. Materials and Methods: The dried leaves of Tectona grandis were subjected to Soxhlet extraction using methanol, and the extract was tested for its anthelmintic activity in vitro using egg hatch assay and larval motility assay. A dose of 250, 125, 62.5, 31.25, 15.625, and 7.8125 mg/ mL was used for the study. Fresh strongyle ova were exposed to different concentrations of the extract and observed after 48 hours for the hatch. L3 larvae obtained from coproculture were subjected to treatment with extract at different concentrations, and mortality per unit time was calculated. Fourier transform infrared (FTIR) spectroscopic analysis and Gas chromatography-mass spectrometry (GC/MS) were performed to identify the chemical nature of the extract. Results: There was a dose-dependent inhibition of hatch and larval mortality with a maximum inhibition of hatch at 250 mg/mL. There was a cent percent hatch in control wells and no loss of progressive motility in the larval motility test. On exposure to the extract, the larvae progressively lost their motility, and finally, there were caesurae of movement which indicated their death. The extract at 250 mg/mL killed all the larvae by 30 min, whereas, at 31.25 mg/mL, the mortality was 66.6% after 2 hr. Conclusion: The results suggest that methanolic extract from Tectona grandis leaves has a promising anthelmintic property and further studies are required for the isolation of active molecules.

ELFN1 is a new extracellular matrix (ECM)-associated protein

AimsThe ELFN1, discovered in 2007, is a single-pass transmembrane protein. Studies conducted thus far to elucidate the function of the Elfn1 have been limited only to animal studies. These studies have reported that ELFN1 is a universal binding partner of metabotropic glutamate receptors (mGluRs) in the central nervous system and its functional deficiency has been associated with the pathogenesis of neurological and neuropsychiatric diseases. In 2021, we described the first disease-associated human ELFN1 pathogenic gene mutation. Severe joint laxity, which was the most striking finding of this new disease and was clearly seen in the patients since early infancy, showed that the ELFN1 may have a possible function in the connective tissue besides the nervous system. Here, we present the first experimental evidence of the extracellular matrix (ECM)-related function of the ELFN1. Materials and methodsPrimary skin fibroblasts were isolated from the skin biopsies of ELFN1 mutated patients and healthy foreskin donors. For the clinical trial in a dish, in vitro ECM and DEM (decellularized ECM) models were created from skin fibroblasts. All the in vitro models were comparatively characterized and analyzed. Key findingsThe mutation in the ELFN1 signal peptide region of patients resulted in a severe lack of ELFN1 expression and dramatically altered the characteristic morphology and behavior (growth, proliferation, and motility) of fibroblasts. SignificanceWe propose that ELFN1 is involved in the cell-ECM attachment, and its deficiency is critical enough to cause a loss of cell motility and soft ECM stiffness.

Multidisciplinary approach to a complex duodenal obstruction: From duodenal atresia to superior mesenteric artery syndrome

We present a 21yo female with a nausea, vomiting, and weight loss. Her history was remarkable for duodenal atresia repair as an infant. Following extensive evaluation, she was found to have progressive dilation of the proximal duodenum and loss of motility without obstruction (megaduodenum) which eventually lead to substantial weight loss resulting in superior mesenteric artery (SMA) syndrome. Given her symptomatic presentation, she was offered surgery and underwent a lateral duodenal tapering procedure and division of the ligament of Treitz and duodenal derotation (Strong procedure). Through the collaborative efforts of gastroenterology, pediatric surgery, radiology, and acute care surgery, she now has excellent functional status, has gained weight, and is asymptomatic. This case serves as an important example that congenital anomalies are a lifelong consideration when caring for patients

Positive In Vitro Effect of ROCK Pathway Inhibitor Y-27632 on Qualitative Characteristics of Goat Sperm Stored at Low Temperatures.

Y-27632, as a cytoskeleton protector, is commonly used for low-temperature preservation of cells. Goat sperm are prone to damage to the cytoskeleton under low-temperature conditions, leading to a loss of sperm vitality. However, the Y-27632 small molecule has not yet been used in research on low-temperature preservation of goat semen. This study aims to address the issue of low temperature-induced loss of sperm motility in goats by using Y-27632, and explore the regulation of Y-27632 on goat sperm metabolism. At a low temperature of 4 °C, different concentrations of Y-27632 were added to the sperm diluent. The regulation of Y-27632 on the quality of low temperature-preserved goat semen was evaluated by detecting goat sperm motility, antioxidant capacity, mitochondrial activity, cholesterol levels, and metabolomics analysis. The results indicated that 20 µM Y-27632 significantly increased plasma membrane integrity (p < 0.05), and acrosome integrity (p < 0.05) and sperm motility (p < 0.05), increased levels of superoxide dismutase (SOD) and catalase (CAT) (p < 0.01), increased total antioxidant capacity (T-AOC) (p < 0.05), decreased levels of malondialdehyde (MDA) and reactive oxygen species (ROS) (p < 0.01), and significantly increased mitochondrial membrane potential (MMP). The levels of ATP, Ca2+, and TC in sperm increased (p < 0.01). Twenty metabolites with significant differences were identified, with six metabolic pathways having a significant impact, among which the D-glutamic acid and D-glutamine metabolic pathways had the most significant impact. The artificial insemination effect of goat semen treated with 20 μM Y-27632 was not significantly different from that of fresh semen. This study indicates that Y-27632 improves the quality of low-temperature preservation of sperm by protecting the sperm plasma membrane, enhancing sperm antioxidant capacity, regulating D-glutamine and D-glutamate metabolism, and promoting the application of low-temperature preservation of semen in artificial insemination technology.

Cellular landscape of the esophageal epithelium in systemic sclerosis

Abstract Systemic sclerosis (SSc) is a rare autoimmune disease characterized by vasculopathy and progressive fibrosis of the skin and internal organs. Individuals with SSc often suffer from chronic acid reflux and dysphagia due to loss of esophageal motility, but this pathogenesis is poorly understood. Recently, studies have suggested that esophageal epithelial cells (EECs) may play a central role in the pathogenesis of SSc esophageal dysmotility. In this study, we performed a thorough transcriptomic investigation of the SSc esophageal epithelium in humans to determine whether distinct changes in EECs contribute to esophageal impairment in SSc. We performed single-cell RNA sequencing of paired proximal and distal esophageal mucosa biopsies from 10 individuals with SSc, 4 comparator individuals with gastroesophageal reflux disease (GERD), and 6 healthy controls (HCs), yielding 230,720 EECs across 40 samples. SSc and GERD samples had significantly fewer terminally differentiated, superficial cells than HCs, and differential gene expression between conditions was primarily limited to superficial EECs. Gene dysregulation in SSc was highly correlated with GERD, but was relatively greater in the proximal region, including unique dysregulation of immune mediators that correlated with esophageal dysmotility. This work sheds light on the cellular roots of esophageal dysfunction in SSc and serves as an atlas to guide future efforts to identify actionable targets in the esophagus in SSc.

RNAi-directed knockdown in the cnidarian fish blood parasite Sphaerospora molnari

RNA interference (RNAi) is an effective approach to suppress gene expression and monitor gene regulation. Despite its wide application, its use is limited in certain taxonomic groups, including cnidarians. Myxozoans are a unique group of cnidarian parasites that diverged from their free-living ancestors about 600 million years ago, with several species causing acute disease in farmed and wild fish populations. In this pioneering study we successfully applied RNAi in blood stages of the myxozoan Sphaerospora molnari, combining a dsRNA soaking approach, real-time PCR, confocal microscopy, and Western blotting. For proof of concept, we knocked down two unusual actins, one of which is known to play a critical role in S. molnari cell motility. We observed intracellular uptake of dsRNA after 30 min and accumulation in all cells of the typical myxozoan cell-in-cell structure. We successfully knocked down actin in S. molnari in vitro, with transient inhibition for 48 h. We observed the disruption of the cytoskeletal network within the primary cell and loss of the characteristic rotational cell motility. This RNAi workflow could significantly advance functional research within the Myxozoa, offering new prospects for investigating therapeutic targets and facilitating drug discovery against economically important fish parasites.

Deleterious effects of free fatty acids and hydrogen peroxide towards the dinoflagellate Gymnodinium catenatum

Allelopathy refers to biochemical interactions among competing microalgae, it involves a donor species that produces metabolites which can cause inhibitory effects on susceptible species. This phenomenon can participate in the regulation of harmful algal blooms. The dinoflagellate Gymnodinium catenatum is negatively affected by allelopathic interactions with co-occurring microalgae species, like Chattonella marina var. marina, which has been suggested to produce reactive oxygen species (ROS) and free fatty acids (FFA) as nocive and allelopathic agents. This study explored the effect of hydrogen peroxide (H2O2) and the main fatty acids produced by C. marina. An analysis of fatty acids content of C. marina in exponential phase detected 16:0 (12.5 ± 0.01%), 18:4ω-3 (15.4 ± 0.36%) and 20:5ω-3 (35.4 ± 0.71%) as the most abundant. These fatty acids along with H2O2 were used in dose-response bioassays with cultures of G. catenatum in exponential phase. Results suggest that these substances affect cell morphology, including the loss of motility and signs of chlorosis, as well as the chain forming qualities of G. catenatum. Toxicity among these substances varied, suggesting that the polyunsaturated fatty acid 18:4ω-3 can potentially act as a more effective allelochemical (LD50 = 1.7 ± 0.19 mg L-1 at 24 h), followed by 20:5ω-3 (LD50 = 3.6 ± 0.17 mg L-1 at 24 h) and the saturated fatty acid 16:0 (LD50 = 6.2 ± 1.05 at 48 h). Our results suggest these substances can act, at least partially, as allelochemicals, with PUFA being the most effective metabolites. These results contribute in elucidating the potential role of ROS and FFA in allelopathy in marine phytoplankton communities.

A hybrid receptor binding protein enables phage F341 infection of Campylobacter by binding to flagella and lipooligosaccharides.

Flagellotropic bacteriophages are interesting candidates as therapeutics against pathogenic bacteria dependent on flagellar motility for colonization and causing disease. Yet, phage resistance other than loss of motility has been scarcely studied. Here we developed a soft agar assay to study flagellotropic phage F341 resistance in motile Campylobacter jejuni. We found that phage adsorption was prevented by diverse genetic mutations in the lipooligosaccharides forming the secondary receptor of phage F341. Genome sequencing showed phage F341 belongs to the Fletchervirus genus otherwise comprising capsular-dependent C. jejuni phages. Interestingly, phage F341 encodes a hybrid receptor binding protein (RBP) predicted as a short tail fiber showing partial similarity to RBP1 encoded by capsular-dependent Fletchervirus, but with a receptor binding domain similar to tail fiber protein H of C. jejuni CJIE1 prophages. Thus, C. jejuni prophages may represent a genetic pool from where lytic Fletchervirus phages can acquire new traits like recognition of new receptors.

Cytopathic effects in Mimivirus infection: understanding the kinetics of virus-cell interaction.

Giant viruses have brought new insights into different aspects of virus-cell interactions. The resulting cytopathic effects from these interactions are one of the main aspects of infection assessment in a laboratory routine, mainly reflecting on the morphological features of an infected cell. In this work, we follow the entire kinetics of the cytopathic effect in cells infected by viruses of the Mimiviridae family, spatiotemporally quantifying typical features such as cell roundness, loss of motility, decrease in cell area and cell lysis. Infections by Acanthamoeba polyphaga mimivirus (APMV), Tupanvirus (TPV) and M4 were carried out at multiplicity of infection (MOI) 1 and MOI 10 in Acanthamoeba castellanii. Monitoring of infections was carried out using time lapse microscopy for up to 72 hours. The images were analyzed using ImageJ software. The data obtained indicate that APMV is the slowest virus in inducing the cytopathic effects of rounding, decrease in cell area, mobility and cell lysis. However, it is the only virus whose MOI increase accelerates the lysis process of infected cells. In turn, TPV and M4 rapidly induce morphological and behavioral changes. Our results indicate that mimiviruses induce different temporal responses within the host cell and that it is possible to use these kinetic data to facilitate the understanding of infection by these viruses.

Using Cell Motility and Particle Tracking to Deduce Mechanisms and Kinetics Underlying Photocatalytic Water Disinfection in Real Time

Photocatalysis is a promising water disinfection method that has the potential to complement traditional approaches to water remediation. Large-scale implementation of photocatalysis for water remediation requires a two-fold improvement to the current state-of-the-art: understanding of the mechanisms underlying photocatalyst-pathogen interaction and pathogen inactivation during photocatalysis, and a process for rapid catalyst discovery that provides for evaluating photocatalyst efficacies in a reliable manner. Toward this goal, we will discuss the use of novel tools developed in our laboratory to track the viability loss of bacterial cells inactivated by photocatalytic treatment in real time. Using optical microscopy and particle-tracking algorithms, we observed that, when exposed to titanium dioxide (TiO2) nanowire-assisted photocatalytic stressors, the change in the motility of Escherichia coli (E. coli) cells tracks viability loss precisely. Furthermore, using phase and fluorescence optical microscopy, real-time observations of the interactions between the cells and the photocatalyst nanowires were also performed. Our findings suggest that these interactions occur through collisions between the nanowires and bacteria. Based on these observations, we developed a phenomenological model explaining the pseudo-first-order kinetics of E. coli inactivation. Through the use of fluorescence-based microscopy, we observed that the motility loss (and hence viability loss) was due to the dissipation of the proton motive force that powers motility, caused by cell membrane integrity loss. Our experiments show a good match between the kinetics of motility loss and viability loss for various operating conditions, showing that the methods presented here are versatile in applicability. Overall, our results indicate that these in situ methods offer significant time-savings for characterizing viability loss of pathogens over the traditional ex-situ methods. As indicated above, these methods will also help accelerate the evaluation of novel antibacterial agents, including, but not limited to novel photocatalysts, against emerging treatment-resistant pathogens, for applications ranging from water disinfection to equipment decontamination in healthcare facilities.