Biology subjects

Lee, C. K.

Publications and source records attributed to Lee, C. K..

15 recordsLinked to original sources

bioRxiv2026

Acute head shaking precedes chronic corpus callosum deficits during repeated cocaine exposure in common marmosets

Background: Stimulant exposure can induce acute stereotyped behaviors and chronic alterations in brain connectivity and white matter integrity. However, the temporal sequence and molecular changes linking these cocaine-induced phenotypes remain unclear. Methods: We combined LabGym-based behavioral analysis, longitudinal brain imaging, and cross-species molecular analysis in 11 common marmosets (Callithrix jacchus; seven male, four female): four underwent behavioral and imaging studies, six provided molecular data, and one provided immunohistochemical data. Male Cryab knockout and wild-type mice underwent functional studies. Results: Acute cocaine (5 mg/kg, intraperitoneally) induced rapid, repetitive lateral head movements, defined as head shaking. After 1 and 10 months of repeated exposure, resting-state functional connectivity was altered in sensory, parietal, prefrontal, motor, and hippocampal regions. Changes were detected at 1 month, whereas diffusion tensor imaging showed reduced fractional anisotropy and axial diffusivity in the corpus callosum splenium at 10 months, with no significant genu changes. Cross-species transcriptomic and proteomic comparison identified DPYSL2 and DNM3 as shared axon-associated molecules. Western blotting showed reduced DPYSL2 in brain tissue from cocaine-treated marmosets. CRYAB localized to O4-positive callosal oligodendrocytes and increased following chronic cocaine exposure. Cryab knockout mice had reduced corpus callosum thickness, increased forced-swim immobility, and reduced open-field distance traveled, supporting a role for CRYAB in corpus callosum integrity and depression-related behavior. Conclusions: These findings show that acute cocaine-induced stereotyped head shaking precedes functional connectivity changes and later corpus callosum deficits. Reduced DPYSL2 may be associated with axonal dysfunction, whereas increased CRYAB may represent a response to cocaine-induced white matter stress.

pharmacology and toxicology↗

bioRxiv2026

Restoration of circulating 2-arachidonoylglycerol levels attenuates cocaine self-administration through endocannabinoid-dopamine interactions in common marmosets

To date, no pharmacotherapy has been approved for cocaine use disorder. Endocannabinoid signaling is closely related to dopamine-dependent reinforcement and may regulate cocaine-related behaviors. In this study, we used common marmosets (Callithrix jacchus) to investigate whether 2-arachidonoylglycerol (2-AG), an endogenous cannabinoid lipid, reduces cocaine reinforcement in a non-restraint oral self-administration model. Marmosets performed oral cocaine self-administration under a fixed-ratio 1 schedule, and cocaine intake was confirmed using plasma benzoylecgonine detection. Dopamine transporter (DAT)-related positron emission tomography (PET) signal, DAT and G protein-coupled receptor 55 (GPR55)-associated fluorescent signals, GPR55/DAT immunofluorescence, and synaptosomal dopamine responses were assessed using 18F-N-(3-fluoropropyl)-2{beta}-carboxymethoxy-3{beta}-(4-iodophenyl) nortropane (18F-FP-CIT) PET imaging, ex vivo fluorescent ligand imaging, confocal microscopy, and dopamine quantification. Marmosets acquired oral cocaine self-administration with preferential active lever responding. Repeated cocaine self-administration reduced striatal DAT-related 18F-FP-CIT PET signal in vivo. In striatal slices, cocaine decreased fluorescent false neurotransmitter (FFN102)-associated DAT signal and increased T1117-associated GPR55 signal. Systemic 2-AG pretreatment reduced cocaine self-administration while restoring diminished circulating 2-AG levels. GPR55 and DAT immunofluorescent signals were colocalized in marmoset brain sections, and 2-AG enhanced cocaine-induced dopamine elevation in synaptosomal preparations. Taken together, these findings suggest that 2-AG attenuates cocaine-taking behavior and may be associated with GPR55/DAT-related dopaminergic responses in common marmosets.

pharmacology and toxicology↗

bioRxiv2026

FASN Inhibition Resensitizes Chordoma to Radiotherapy by Targeting Adaptive Unsaturated Fatty Acid Metabolism

SUMMARYChordoma, a rare malignant notochordal tumor of the skull base and spine, is typically resistant to chemotherapy and radiotherapy and exhibits aggressive local recurrence. Here we show that chordoma recurrence correlates with a coordinated upregulation of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs), a low PFA/MUFA ratio and an adaptive, lipid peroxidation-resistant state that protects against DNA damage and cell death. Single-cell metabolic profiling identified a tumor subpopulation marked by a fatty acid biosynthesis-high state coupled to stemness. RT-tolerance was directly linked to elevated FASN and lipid droplet (LD) expansion, and MUFA-loading phenocopied RT-tolerance in chordoma cells. Mechanistically, LDs accumulated in response to RT via generation of ROS, and subsequent activation of ER-stress, SREBP1 and Fatty Acid Synthetase (FASN). DESI-MS showed that low-dose irradiation was sufficient to increase MUFAs early and build peroxidation resistant MUFA-LDs, whereas PUFA induction required a higher radiation dose. In a spatially defined manner in a patient-derived xenograft. Finally, in silico knockout and pharmacologic FASN blockade restored radiosensitivity and apoptosis in vitro and in vivo. Collectively, our result support a unifying model in which RT resistance in chordoma is shaped by an adaptive fatty acid metabolic program that buffers oxidative injury and increases survival of RT-resistant, stem-like tumor subpopulations. These findings further support FASN inhibition as a practical radiosensitization strategy for chordoma particulary where RT dose escalation is constrained by anatomy. KEYPOINTSO_LIRecurrent chordoma exhibits fatty acid-associated metabolic reprogramming. C_LIO_LIMUFA-associated lipid droplet accumulation is linked to radioresistance in chordoma cells. C_LIO_LITargeting FASN restores radiotherapy sensitivity of chordoma in vitro and in vivo. C_LI IMPORTANCE OF STUDYThis study underscores the clinical importance of targeting metabolic vulnerabilities to restore radiosensitivity in chordoma. By integrating transcriptomics, metabolomics, and in vitro and in vivo models, we identified adaptive fatty acid metabolic reprogramming as a central mechanism of RT resistance in chordoma. Recurrent tumors were characterized by coordinated enrichment of unsaturated fatty acids, especially monounsaturated fatty acids (MUFAs), together with a low PUFA/MUFA ratio and a lipid peroxidation-resistant state. Mechanistically, RT-tolerance chordoma cells exhibited a high-FASN state driven by activation of the ROS-ER stress-PERK/SREBP1/FASN axis, leading to intracellular lipid droplet expansion. Importantly, genetic and pharmacologic inhibition of FASN restored radiosensitivity and enhanced apoptosis in both in vitro and in vivo models, suggesting a translatable therapeutic strategy. Together, these findings link adaptive metabolic reprogramming to RT resistance and support new therapeutic approaches for chordoma management.

cancer biology↗

bioRxiv2025

Gaps and Advances in Long-Term Monitoring of Antarctic Near-Shore and Terrestrial Ecosystems

Environmental change due to greenhouse gas emissions is affecting ecosystems globally; in the polar regions in particular there is already significant evidence of change. The Antarctic Near-Shore and Terrestrial Observation System (ANTOS) aims to establish a cross-continent, cross-national observing network to assess environmental variability and change in the southern polar region. To understand how near-shore and terrestrial Antarctic ecosystems have and will continue to be impacted by anthropogenic environmental changes, a comprehensive review of current long-term monitoring efforts, and two surveys targeting Antarctic researchers, were carried out to evaluate existing monitoring efforts, environmental changes recorded, and to identify areas currently lacking sufficient observations. Results indicate that most data collection is manual and intra-annual, with significant long-term monitoring concentrated in regions with already established infrastructure. The surveys highlight the urgent need for comprehensive coverage of the Antarctics rapidly changing ecosystems using standardized monitoring protocols and increased collaboration. We recommend prioritizing areas experiencing rapid climatic changes and leveraging existing infrastructure to minimize environmental impact of monitoring activities and enhance data comparability across sites.

ecology↗

bioRxiv2024

Immunological correlates of protection mediated by a whole organism Cryptococcus neoformans vaccine deficient in chitosan

The global burden of infections due to the pathogenic fungus Cryptococcus is substantial in persons with low CD4+ T cell counts. Previously, we deleted three chitin deacetylase genes from C. neoformans to create a chitosan-deficient, avirulent strain, designated cda1{Delta}2{Delta}3{Delta} which, when used as a vaccine, protected mice from challenge with virulent C. neoformans strain KN99. Here, we explored the immunological basis for protection. Vaccine-mediated protection was maintained in mice lacking B cells or CD8+ T cells. In contrast, protection was lost in mice lacking /{beta} T cells or CD4+ T cells. Moreover, CD4+ T cells from vaccinated mice conferred protection upon adoptive transfer to naive mice. Importantly, while monoclonal antibody-mediated depletion of CD4+ T cells just prior to vaccination resulted in complete loss of protection, significant protection was retained in mice depleted of CD4+ T cells after vaccination, but prior to challenge. Vaccine-mediated protection was lost in mice genetically deficient in IFN{gamma}, TNF, or IL-23p19. A robust influx of leukocytes and IFN{gamma}- and TNF-expressing CD4+ T cells was seen in the lungs of vaccinated and challenged mice. Finally, a higher level of IFN{gamma} production by lung cells stimulated ex vivo correlated with lower fungal burden in the lungs. Thus, while B cells and CD8+ T cells are dispensable, IFN{gamma} and CD4+ T cells have overlapping roles in generating protective immunity prior to cda1{Delta}2{Delta}3{Delta} vaccination. However, once vaccinated, protection becomes less dependent on CD4+ T cells, suggesting a strategy for vaccinating HIV+ persons prior to loss of CD4+ T cells. ImportanceThe fungus Cryptococcus neoformans is responsible for >100,000 deaths annually, mostly in persons with impaired CD4+ T cell function such as AIDS. There are no approved human vaccines. We previously created a genetically engineered avirulent strain of C. neoformans, designated cda1{Delta}2{Delta}3{Delta}. When used as a vaccine, cda1{Delta}2{Delta}3{Delta} protects mice against a subsequent challenge with a virulent C. neoformans strain. Here, we defined components of the immune system responsible for vaccine-mediated protection. We found that while B cells and CD8+ T cells were dispensible, protection was lost in mice genetically deficient in CD4+ T cells, and the cytokines IFN{gamma}, TNF, or IL-23. A robust influx of cytokine-producing CD4+ T cells was seen in the lungs of vaccinated mice following infection. Importantly, protection was retained in mice depleted of CD4+ T cells following vaccination, suggesting a strategy to protect persons who are at risk for future CD4+ T cell dysfunction.

immunology↗

bioRxiv2024

Antarctic geothermal soils exhibit an absence of regional habitat generalist microorganisms

Active geothermal systems are relatively rare in Antarctica and represent metaphorical islands ideal to study microbial dispersal. In this study, we tested the macroecological concept that high dispersal rates result in communities being dominated by either habitat generalists or specialists by investigating the microbial communities on four geographically separated geothermal sites on three Antarctic volcanoes (Mts. Erebus, Melbourne and Rittman). We found that the microbial communities at higher temperature (max 65{square}) sites (Tramway Ridge on Erebus and Rittmann) were unique from each other and were dominated by a variety of novel Archaea from class Nitrososphaeria, while lower temperature (max 50{square}) sites (Western Crater on Erebus and Melbourne) had characteristically mesophilic communities (Planctomycetes, Acidobacteriota, etc) that were highly similar. We found that 97% of the detected microbial taxa were regional habitat specialists, with no generalists, with community assembly driven by high dispersal rates and drift (25 and 30% of community assembly, respectively), not environmental selection. Our results indicate that for microbial communities experiencing high dispersal rates between isolated communities, habitat specialists may tend to out-compete habitat generalists.

microbiology↗

bioRxiv2023

Dysregulated Pulmonary Inflammatory Responses Exacerbate the Outcome of Secondary Aspergillosis Following Influenza

Inhalation of airborne conidia of the ubiquitous fungus Aspergillus fumigatus commonly occurs but invasive aspergillosis is rare except in profoundly immunocompromised persons. Severe influenza predisposes patients to invasive pulmonary aspergillosis by mechanisms that are poorly defined. Using a post-influenza aspergillosis model, we found that superinfected mice had 100% mortality when challenged with A. fumigatus conidia on days 2 and 5 (early stages) of influenza A virus infection but 100% survival when challenged on days 8 and 14 (late stages). Influenza-infected mice superinfected with A. fumigatus had increased levels of the pro-inflammatory cytokines and chemokines IL-6, TNF, IFN{beta}, IL-12p70, IL-1, IL-1{beta}, CXCL1, G-CSF, MIP-1, MIP-1{beta}, RANTES and MCP-1. Surprisingly, on histopathological analysis, superinfected mice did not have greater lung inflammation compared with mice infected with influenza alone. Mice infected with influenza had dampened neutrophil recruitment to the lungs following subsequent challenge with A. fumigatus, but only if the fungal challenge was executed during the early stages of influenza infection. However, influenza infection did not have a major effect on neutrophil phagocytosis and killing of A. fumigatus conidia. Moreover, minimal germination of conidia was seen on histopathology even in the superinfected mice. Taken together, our data suggest that the high mortality rate seen in mice during the early stages of influenza-associated pulmonary aspergillosis is multifactorial, with a greater contribution from dysregulated inflammation than microbial growth. ImportanceSevere influenza is a risk factor for fatal invasive pulmonary aspergillosis; however, the mechanistic basis for the lethality is unclear. Utilizing an influenza-associated pulmonary aspergillosis (IAPA) model, we found that mice infected with influenza A virus followed by A. fumigatus had 100% mortality when superinfected during the early stages of influenza but survived at later stages. While superinfected mice had dysregulated pulmonary inflammatory responses compared to controls, they had neither increased inflammation nor extensive fungal growth. Although influenza-infected mice had dampened neutrophil recruitment to the lungs following subsequent challenge with A. fumigatus, influenza did not affect the ability of neutrophils to clear the fungi. Our data suggest that the lethality seen in our model IAPA is multifactorial with dysregulated inflammation being a greater contributor than uncontrollable microbial growth. If confirmed in humans, our findings provide a rationale for clinical studies of adjuvant anti-inflammatory agents in the treatment of IAPA.

immunology↗

bioRxiv2022

Next generation digital PCR: high dynamic range single molecule DNA counting via ultra-partitioning

Digital PCR (dPCR) was first conceived for single molecule quantitation. However, current dPCR systems often require DNA templates to share partitions due to limited partitioning capacities. Here, we introduce Ultra-dPCR, a next generation dPCR system where DNA counting is performed in a single-molecule regimen through a 6-log dynamic range using a swift and parallelized workflow. Each Ultra-dPCR reaction is divided into >30 million partitions without microfluidics to achieve single template occupancy. Combined with a unique emulsion chemistry, partitions are optically clear and enable the use of a 3D imaging technique to rapidly detect DNA-positive partitions. Single molecule occupancy also allows for more straightforward multiplex assay development due to the absence of partition-specific competition. As a proof-of-concept, we developed a 222-plex Ultra-dPCR assay and demonstrated its potential use as a rapid, low-cost screening assay for non-invasive prenatal testing (NIPT) for as low as 4% trisomy fraction samples with high precision, accuracy, and reproducibility.

genomics↗

bioRxiv2022

Phylogenetic analysis of human parainfluenza type 3 virus strains responsible for the outbreak during the COVID-19 pandemic in Seoul, South Korea

BackgroundHuman parainfluenza virus 3 (HPIV3) is a major respiratory pathogen that causes acute respiratory infections in infants and children. Since September 2021, an out-of-season HPIV3 rebound has been noted in Korea. The objective of this study was to analyze the molecular characteristics of the HPIV3 strains responsible for the outbreak in Seoul, South Korea. MethodsA total of 61 HPIV3-positive nasopharyngeal swab specimens were collected between October and November 2021. Using 33 HPIV3-positive specimens, partial nucleotide sequences of the HPIV3 hemagglutinin-neuraminidase (HN) gene were aligned with previously published HN gene sequences for phylogenetic and genetic distance (p-distance) analyses. ResultsPhylogenetic tree revealed that all Seoul HPIV3 strains grouped within the phylogenetic subcluster C3. However, these strains formed a unique cluster that branched separately from the C3a lineage. This cluster showed 99% bootstrap support with a p-distance < 0.001. Genetic distances within the other C3 lineages ranged from 0.013 (C3a) to 0.023 (C3c). Deduced amino acid sequences of the HN gene revealed four protein substitutions in Seoul HPIV3 strains that have rarely been observed in other reference strains: A22T, K31N, G387S, and E514K. ConclusionsPhylogenetic analysis of Seoul HPIV3 strains revealed that the strain belonged to a separate cluster within subcluster C3. Genetic distances among strains within subcluster C3 suggest the emergence of a new genetic lineage. The emergence of a new genetic lineage could pose a potential risk of a new epidemic. Further monitoring of the circulating HPIV3 strains is needed to understand the importance of newly discovered mutations.

microbiology↗

bioRxiv2021

Protection of mice against experimental cryptococcosis by synthesized peptides delivered in glucan particles

The high global burden of cryptococcosis has made development of a protective vaccine a public health priority. We previously demonstrated that a vaccine composed of recombinant Cryptococcus neoformans chitin deacetylase 2 (Cda2) delivered in glucan particles (GPs) protects BALB/c and C57BL/6 mice from an otherwise lethal challenge with a highly virulent C. neoformans strain. An immunoinformatic analysis of Cda2 revealed a peptide sequence predicted to have strong binding to the MHC Class II (MHC II) H2-IAd allele found in BALB/c mice. BALB/c mice vaccinated with GPs containing a 32 amino acid peptide (Cda2-Pep1) that included this strong binding region were protected from cryptococcosis. Protection was lost with GP-based vaccines containing versions of recombinant Cda2 protein and Cda2-Pep1 with mutations predicted to greatly diminish MHC II binding. Cda2 has homology to the three other C. neoformans chitin deacetylases, Cda1, Cda3 and Fpd1, in the high MHC II binding region. GPs loaded with homologous peptides of Cda1, Cda3 and Fpd1 protected BALB/c mice from experimental cryptococcosis, albeit not as robustly as the Cda2-Pep1 vaccine. Finally, seven other peptides were synthesized based on regions in Cda2 predicted to contain promising CD4+ T cell epitopes in BALB/c or C57BL/6 mice. While five peptide vaccines significantly protected BALB/c mice, only one protected C57BL/6 mice. Thus, GP-based vaccines containing a single peptide can protect mice against cryptococcosis. However, given the diversity of human MHC II alleles, a peptide-based Cryptococcus vaccine for use in humans would be challenging and likely need to contain multiple peptide sequences. ImportanceCryptococcosis, due to infection by fungi of the Cryptococcus neoformans species complex, is responsible for substantial morbidity and mortality in immunocompromised persons, particularly those with AIDS. Cryptococcal vaccines are a public health priority yet are not available for human use. We previously demonstrated mice could be protected from experimental cryptococcosis with vaccines composed of recombinant cryptococcal proteins encased in hollow highly purified yeast cell walls (glucan particles). Here, we examined one such protective protein, Cda2, and using bioinformatics, identified a region predicted to stimulate strong T cell responses. A peptide containing this region formulated in glucan particle-based vaccines protected mice as well as the recombinant protein. Other peptide vaccines also protected, including peptides containing sequences from proteins homologous to Cda2. These preclinical mouse studies provide a proof of principle that peptides can be effective as vaccines to protect against cryptococcosis and that bioinformatic approaches can guide peptide selection.

immunology↗

bioRxiv2021

Force-induced changes of PilY1 drive surface sensing by Pseudomonas aeruginosa

During biofilm formation, the opportunistic pathogen Pseudomonas aeruginosa uses its type IV pili (TFP) to sense a surface, eliciting increased second messenger production and regulating target pathways required to adapt to a surface lifestyle. The mechanisms whereby TFP detect surface contact is still poorly understood, although mechanosensing is often invoked with little data supporting this claim. Using a combination of molecular genetics and single cell analysis, with biophysical, biochemical and genomics techniques we show that force-induced changes mediated by the von Willebrand A (vWA) domain-containing, TFP tip-associated protein PilY1 are required for surface sensing. Atomic force microscopy shows that PilY1 can undergo force-induced, sustained conformational changes akin to those observed for mechanosensitive proteins like titin. We show that mutation of a single cysteine residue in the vWA domain results in modestly lower surface adhesion forces, increased nanospring-like properties, as well as reduced c-di-GMP signaling and biofilm formation. Mutating this cysteine has allowed us to genetically separate TFP function in twitching from surface sensing signaling. The conservation of this Cys residue in all P. aeruginosa PA14 strains, and its absence in the ~720 sequenced strains of P. aeruginosa PAO1, could contribute to explaining the observed differences in surface colonization strategies observed for PA14 versus PAO1. ImportanceMost bacteria live on abiotic and biotic surfaces in surface-attached communities known as biofilms. Surface sensing and increased levels of the second messenger molecule c-di-GMP are crucial to the transition from planktonic to biofilm growth. The mechanism(s) underlying TFP-mediated surface detection that triggers this c-di-GMP signaling cascade are unclear. Here, we provide a key insight into this question: we show that the eukaryotic-like, vWA domain of the TFP tip-associated protein PilY1 responds to mechanical force, which in turn drives production of a key second messenger needed to regulate surface behaviors. Our studies highlight a potential mechanism that could account for differing surface colonization strategies.

microbiology↗

bioRxiv2020

Fine tuning cyclic-di-GMP signaling in Pseudomonas aeruginosa using the type 4 pili alignment complex

To initiate biofilm formation it is critical for bacteria to sense a surface and respond precisely. Type 4 pili (T4P) have been shown to be important in surface sensing, however, mechanism(s) driving downstream changes important for the switch to biofilm growth have not been clearly defined. Here, using macroscopic bulk assays and single cell tracking analyses of Pseudomonas aeruginosa, we uncover a new role of the T4P alignment complex protein, PilO, in modulating the activity of the diguanylate cyclase (DGC) SadC. Two hybrid and bimolecular fluorescence complementation assays show that PilO physically interacts with SadC and that the PilO-SadC interaction inhibits SadCs activity resulting in decreased biofilm formation and increased motility. We show that disrupting the PilO-SadC interaction contributes to greater variation of cyclic-di-GMP levels among cells, thereby increasing cell-to-cell heterogeneity in the levels of this signal. Thus, this work shows that P. aeruginosa uses a component of the T4P scaffold to fine-tune the levels of this nucleotide signal during surface commitment. Finally, given our previous findings linking SadC to the flagellar machinery, we propose that this DGC acts as a bridge to integrate T4P and flagellar-derived input signals during initial surface engagement. Significance StatementT4P of P. aeruginosa are important for surface sensing and regulating intracellular cyclic-di-GMP levels. This work identifies a new role for the T4P alignment complex, previously known for its role in supporting pili biogenesis, in surface-dependent signaling. Furthermore, our findings indicate that P. aeruginosa uses a single DGC, via a complex web of protein-protein interactions, to integrate signaling through the T4P and the flagellar motor to fine-tune cyclic-di-GMP levels. A key implication of this work is that more than just regulating signal levels, cells must modulate the dynamic range of cyclic-di-GMP to precisely control the transition to a biofilm lifestyle.

microbiology↗

bioRxiv2020

Nonlinearities between inhibition and T-type calcium channel activity bidirectionally regulate thalamic network oscillations

Absence seizures result from 3-5 Hz generalized thalamocortical oscillations that depend on highly regulated inhibitory neurotransmission in the thalamus. Efficient reuptake of the inhibitory neurotransmitter GABA is essential, and reuptake failure worsens seizures. Here, we show that blocking GABA transporters (GATs) in acute brain slices containing key parts of the thalamocortical seizure network modulates epileptiform activity. As expected, we found that blocking either GAT1 or GAT3 prolonged oscillations. However, blocking both GATs unexpectedly suppressed oscillations. Integrating experimental observations into single-neuron and network-level computational models shows how a non-linear dependence of T-type calcium channel opening on GABAB receptor activity regulates network oscillations. Receptor activity that is either too brief or too protracted fails to sufficiently open T-type channels necessary for sustaining oscillations. Only within a narrow range does prolonging GABAB receptor activity promote channel opening and intensify oscillations. These results have implications for therapeutics that modulate GABA transporters.

neuroscience↗

bioRxiv2019

Heterogeneity in surface sensing produces a division of labor in Pseudomonas aeruginosa populations

The second messenger signaling molecule cyclic diguanylate monophosphate (c-di-GMP) drives the transition from planktonic to biofilm growth in many bacterial species. Pseudomonas aeruginosa has two surface sensing systems that produce c-di-GMP in response to surface adherence. The current thinking in the field is that once cells attach to a surface, they uniformly respond with elevated c-di-GMP. Here, we describe how the Wsp system generates heterogeneity in surface sensing, resulting in two physiologically distinct subpopulations of cells. One subpopulation has elevated c-di-GMP and produces biofilm matrix, serving as the founders of initial microcolonies. The other subpopulation has low c-di-GMP and engages in surface motility, allowing for exploration of the surface. We also show that this heterogeneity strongly correlates to surface behavior for descendent cells. Together, our results suggest that after surface attachment, P. aeruginosa engages in a division of labor that persists across generations, accelerating early biofilm formation and surface exploration.

microbiology↗

bioRxiv2018

Microbial biogeography of 1,000 geothermal springs in New Zealand

Geothermal springs are model ecosystems to systematically investigate microbial biogeography as they i) represent discrete, homogenous habitats; ii) are abundantly distributed across multiple geographical scales; iii) span broad geochemical gradients; and iv) have simple community structures with reduced metazoan interactions. Taking advantage of these traits, we undertook the largest known consolidated study of geothermal ecosystems (http://1000springs.org.nz) to determine factors that influence biogeographical patterns. Rigorously standardised methodologies were used to measure microbial communities, 46 physicochemical parameters, and metadata from 1,019 hotspring samples across New Zealand. pH was found to be the primary influence on diversity in springs < 70 {degrees}C with community similarity decreasing with geographic distance. Surprisingly, community composition was dominated by two genera (Venenivibrio and Acidithiobacillus) in both average relative abundance (11.2 and 11.1 %) and prevalence (74.2 and 62.9 % respectively) across physicochemical spectrums of 13.9 - 100.6 {degrees}C and pH < 1 - 9.7. This study provides an unprecedented insight into the ecological conditions that drive community assembly in geothermal springs, and can be used as a foundation to improve the characterisation of global microbial biogeographical processes.

microbiology↗