Poor Colonization Research Articles

Establishment of the improved colonization of Escherichia coli laboratory strain in the intestine mediated by single gene deletion

In light of the emerging importance of the gut microbiome in human health, there is a need to improve the colonization efficiency of therapeutic bacteria called probiotics. Despite their recognized potential, artificially administered bacteria exhibit poor colonization in the intestine, limiting their therapeutic efficacy. Addressing this challenge requires innovative strategies; however, reported examples are limited. In nature, including in the intestinal tract, bacteria live via biofilm formation. Recently, it has been reported that RNase I, a member of the RNase T2 family conserved among almost all species, including bacteria, inhibits biofilm formation in Escherichia coli. In this study, we focus on these results and investigate the relationship between high biofilm formation and intestinal attachment using a non-settling E. coli laboratory strain as a probiotic model. The intestinal colonization abilities were evaluated through a microfluidic device mimicking the intestinal tract and through oral administration to mice. The in vitro and in vivo experiments showed that the E. coli strain lacking RNase I exhibited remarkable stability in intestinal colonization. We investigated the observation of colonization using fluorescence in situ hybridization, and inoculated E. coli cells were aggregated with the gut microbiome in the cecum and colon. This study proposes a technique to improve the intestinal colonization of bacteria by simply manipulating a single gene disruption, and it is expected to contribute to future research on the colonization of useful bacteria.

Deep-sea microorganisms-driven V5+ and Cd2+ removal from vanadium smelting wastewater: Bacterial screening, performance and mechanism

The disorderly discharge of industrial wastewater containing heavy metals has caused serious water pollution and ecological environmental risks, ultimately threatening human life and health. Biological treatment methods have obvious advantages, but the existing microorganisms exhibit issues such as poor resistance, adaptability, colonization ability, and low activity. However, a wide variety of microorganisms in deep-sea hydrothermal vent areas are tolerant to heavy metals, possessing the potential for efficient treatment of heavy metal wastewater. Based on this, the study obtained a group of deep-sea microbial communities dominated by Burkholderia-Caballeronia-Paraburkholderia through shake flask experiments from the sediments of deep-sea hydrothermal vents, which can simultaneously achieve the synchronous removal of vanadium and cadmium heavy metals through bioreduction, biosorption, and biomineralization. Through SEM-EDS, XRD, XPS, and FT-IR analyses, it was found that V(V) was reduced to V(IV) through a reduction process and subsequently precipitated. Glucose oxidation accelerated this process. Cd(II) underwent biomineralization to form precipitates such as cadmium hydroxide and cadmium carbonate. Functional groups on the microbial cell surface, such as -CH2, C=O, N-H, -COOH, phosphate groups, amino groups, and M-O moieties, participated in the bioadsorption processes of V(V) and Cd(II) heavy metals. Under optimal conditions, namely a temperature of 40 °C, pH value of 7.5, inoculation amount of 10%, salinity of 4%, COD concentration of 600 mg/L, V5+ concentration of 300 mg/L, and Cd2+ concentration of 40 mg/L, the OD600 can reach its highest at 72 h, with the removal efficiency of V5+, Cd2+, and COD in simulated vanadium smelting wastewater reaching 86.32%, 59.13%, and 61.63%, respectively. This study provides theoretical insights and practical evidence for understanding the dynamic changes in microbial community structure under heavy metal stress, as well as the resistance mechanisms of microbial treatment of industrial heavy metal wastewater.

Phenotypic, genotypic and proteomic variations between poor and robust colonizing Campylobacter jejuni strains

Campylobacter jejuni is one of the major causes of bacterial gastrointestinal disease in humans worldwide. This foodborne pathogen colonizes the intestinal tracts of chickens, and consumption of chicken and poultry products is identified as a common route of transmission. We analyzed two C. jejuni strains after oral challenge with 105 CFU/ml of C. jejuni per chick; one strain was a robust colonizer (A74/C) and the other a poor colonizer (A74/O). We also found extensive phenotypic differences in growth rate, biofilm production, and in vitro adherence, invasion, intracellular survival, and transcytosis. Strains A74/C and A74/O were genotypically similar with respect to their whole genome alignment, core genome, and ribosomal MLST, MLST, flaA, porA, and PFGE typing. The global proteomes of the two congenic strains were quantitatively analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) and 618 and 453 proteins were identified from A74/C and A74/O isolates, respectively. Cluster of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that carbon metabolism and motility proteins were distinctively overexpressed in strain A74/C. The robust colonizer also exhibited a unique proteome profile characterized by significantly increased expression of proteins linked to adhesion, invasion, chemotaxis, energy, protein synthesis, heat shock proteins, iron regulation, two-component regulatory systems, and multidrug efflux pump. Our study underlines phenotypic, genotypic, and proteomic variations of the poor and robust colonizing C. jejuni strains, suggesting that several factors may contribute to mediating the different colonization potentials of the isogenic isolates.

Hymenoscyphus fraxineus persistence in the ash litter

AbstractHymenoscyphus fraxineus causes ash dieback in Europe. It overwinters on ash leaf residue (rachis) within the forest litter. In late spring, the fungus produces apothecia on the rachises and releases ascospores to infect leaves. Previous studies reported that H. fraxineus was able to produce apothecia on the rachis for 5 years after the leaf infection under artificial conditions. However, ash litter is known to decompose rapidly in situ. We therefore monitored the decomposition kinetics of ash leaf debris and the persistence of the pathogen, as well as its ability to produce apothecia in the forest litter. For this, leaves shed in autumn in stands affected by ash dieback were placed in mesh bags and left in the forest litter for 6, 18 and 30 months. At each sampling period, litter mass loss and level of colonization of the rachises by H. fraxineus were measured, as was the pathogen's ability to produce apothecia on them. Despite high fragmentation, about 14% of the rachis dry weight remained in the mesh bags after 30 months, and the pathogen retained the ability to produce apothecia on these rachises. A simulation estimating the age composition of the colonized rachises present in the litter during the fruiting period was developed from these results. It shows that the persistence of H. fraxineus in old rachises of the litter represents a reservoir of inoculum that could compensate for poor colonization of autumn leaves and revive local outbreaks after years of unfavourable weather for the development of the pathogen.

Poly-L-lactic acid/gelatin electrospun membrane-loaded bone marrow-derived mesenchymal stem cells attenuate erectile dysfunction caused by cavernous nerve injury

Radical prostatectomy (RP) can cause neurogenic erectile dysfunction (ED), which negatively affects the quality of life of patients with prostate cancer. Currently, there is a dearth of effective therapeutic strategies. Although stem cell therapy is promising, direct cell transplantation to injured cavernous nerves is constrained by poor cell colonization. In this study, poly-L-lactic acid (PLLA)/gelatin electrospun membranes (PGEM) were fabricated to load bone marrow-derived mesenchymal stem cells (BM-MSCs) as a patch to be placed on injured nerves to alleviate ED. This study aimed to establish a promising and innovative approach to mitigate neurogenic ED post-RP and lay the foundation for modifying surgical procedures. Electrospinning and molecular biotechnology were performed in vitro and in vivo, respectively. It was observed that PGEM enhanced the performance of BM-MSCs and Schwann cells due to their excellent mechanical properties and biocompatibility. The transplanted PGEM and loaded BM-MSCs synergistically improved bilateral cavernous nerve injury-related ED and the corresponding histopathological changes. Nevertheless, transplantation of BM-MSCs alone has been verified to be ineffective. Overall, PGEM can serve as an ideal carrier to supply a more suitable survival environment for BM-MSCs and Schwann cells, thereby promoting the recovery of injured cavernous nerves and erectile function.

Seedling microbiota engineering using bacterial synthetic community inoculation on seeds.

Synthetic Communities (SynComs) are being developed and tested to manipulate plant microbiota and improve plant health. To date, only few studies proposed the use of SynCom on seed despite its potential for plant microbiota engineering. We developed and presented a simple and effective seedling microbiota engineering method using SynCom inoculation on seeds. The method was successful using a wide diversity of SynCom compositions and bacterial strains that are representative of the common bean seed microbiota. First, this method enables the modulation of seed microbiota composition and community size. Then, SynComs strongly outcompeted native seed and potting soil microbiota and contributed on average to 80% of the seedling microbiota. We showed that strain abundance on seed was a main driver of an effective seedling microbiota colonization. Also, selection was partly involved in seed and seedling colonization capacities since strains affiliated to Enterobacteriaceae and Erwiniaceae were good colonizers while Bacillaceae and Microbacteriaceae were poor colonizers. Additionally, the engineered seed microbiota modified the recruitment and assembly of seedling and rhizosphere microbiota through priority effects. This study shows that SynCom inoculation on seeds represents a promising approach to study plant microbiota assembly and its consequence on plant fitness.

Effects of COVID-19-Associated Infection Control on the Pattern of Infections Imported by German Soldiers and Police Officers Returning from Predominantly Tropical Deployment Sites.

In response to the COVID-19 pandemic, German public health authorities launched various infection control procedures. In line with this, anti-pandemic infection control was also implemented for German military and police deployments. The presented study assessed the impact of this increased infection control effort on deployment-associated infections in a holistic approach. To do so, the results of post-deployment assessments offered to German soldiers and police officers at the Department of Tropical Medicine and Infectious Diseases of the Bundeswehr Hospital Hamburg obtained during the pandemic period were compared to the results recorded during the pre-pandemic period in an exploratory, hypothesis-forming comparative study. In total, data from 1010 military deployments and 134 police deployments, predominantly to the African or the Eastern Mediterranean WHO regions, were included in the analyses. In the main results, a significant decrease in gastroenteritis in deployed soldiers (20.1% versus 61.3%, p < 0.0001) and at least a trend in the same direction in deployed police officers (25.7% versus 35.4%, p = 0.4026) were shown for the pandemic period, while no consistent tendency into the one or the other direction was detectable for febrile illness on deployment. In contrast to the finding of less frequently reported deployment-associated gastroenteritis, the detection rates of enteric microorganisms after deployment, including poor hygiene-related colonization with apathogenic protozoa, remained unchanged. Regarding non-enteric infections, the numbers of serologically confirmed malaria cases on deployment and as expected, due to increased airway protection, Mycobacterium tuberculosis-specific immune-conversion dropped significantly with p = 0.0037 and p = 0.009, respectively. As a side finding, soldiers and police officers with post-deployment medical assessments were more likely to be older and male during the pandemic compared to the pre-pandemic period. In summary, only minor changes in deployment-associated infection and colonization rates were seen in response to the increased infection control procedures during the pandemic period, apart from respiratory infections. In particular, the clinical finding of less gastroenteritis on deployment was not matched by a concordant decline in poor hygiene-related enteric colonization with apathogenic protozoa in the soldiers' guts, indicating that the fecal-oral transmission risk remained basically the same.

Scytalidium cuboideum Inhibits Shiitake Mycelial Growth and Causes Pink Staining in Shiitake Billets (Quercus griffithii) in Bhutan

Pink staining in shiitake (Lentinula edodes (Berk.) Pegler) billets (Quercus griffithii Hook.f. and Thomson ex Miq.) causing the inhibition of shiitake mycelium and a reduction in shiitake production was observed throughout Bhutan in 2017–2018. Completion of Koch’s postulates confirmed the causal agent to be Scytalidium cuboideum, a first record of this disease in shiitake billets in Bhutan. In failed billets, it was observed that there was no growth of shiitake mycelium from the spawn. Trials suggest that S. cuboideum is responsible for the occurrences of poor colonisation by shiitake spawn—even when pink staining is not evident. Warm temperatures favour S. cuboideum, with shiitake able to sometimes overcome low rates of infection when incubated at low temperatures.

Pathogen-induced dormancy in liquid limits gastrointestinal colonization of Caenorhabditis elegans

ABSTRACT Colonization is generally considered a prerequisite for infection, but this event is context-dependent, as evidenced by the differing ability of the human pathogen Pseudomonas aeruginosa to efficiently colonize Caenorhabditis elegans on agar but not in liquid . In this study, we examined the impact of the environment, pathogen, host, and their interactions on host colonization. We found that the transition to a liquid environment reduces food uptake by about two-fold. Also expression of specific adhesins was significantly altered in liquid-based assays for P. aeruginosa, suggesting that it may be one factor driving diminished colonization. Unexpectedly, host immune pathways did not appear to play a significant role in decreased colonization in liquid. Although knocking down key immune pathways (e.g. daf-16 or zip-2), either alone or in combination, significantly reduced survival, the changes in colonization were very small. In spite of the limited bacterial accumulation in the liquid setting, pathogenic colonization was still required for the virulence of Enterococcus faecalis. In addition, we found that a pathogen-induced dormancy was displayed by C. elegans in liquid medium after pathogen exposure, resulting in cessation of pharyngeal pumping and a decrease in bacterial intake. We conclude that poor colonization in liquid is likely due to a combination of environmental factors and host-pathogen interactions. These results provide new insights into mechanisms for colonization in different models, enabling pathogenesis models to be fine-tuned to more accurately represent the conditions seen in human infections so that new tools for curbing bacterial and fungal infections can be developed.

Screening the maize rhizobiome for consortia that improve Azospirillum brasilense root colonization and plant growth outcomes

Plant growth-promoting bacteria (PGPB) are valuable for supporting sustainable food production and may alleviate the negative impacts of chemical fertilizers on human health and the environment. While single-strain inoculations have proven unreliable due to poor survival and colonization in the rhizosphere, application of PGPB in multispecies consortia has the potential to improve these outcomes. Here, we describe a new approach for screening and identifying bacterial consortia that improve the growth of corn relative to plants inoculated with a single strain. The method uses the microwell recovery array (MRA), a microfabricated high-throughput screening device, to rapidly explore the maize (Zea mays L.) rhizobiome for higher-order combinations of bacteria that promote the growth and colonization of the nitrogen-fixing PGPB, Azospirillum brasilense. The device simultaneously generates thousands of random, unique combinations of bacteria that include A. brasilense and members of the maize rhizobiome, then tracks A. brasilense growth in each combination during co-culture. Bacteria that show the highest levels of A. brasilense growth promotion are then recovered from the device using a patterned light extraction technique and are identified. With this approach, the screen uncovered growth-promoting consortia consisting primarily of bacteria from the Acinetobacter-Enterobacter-Serratia genera, which were then co-inoculated with A. brasilense on axenic maize seedlings that were monitored inside a plant growth chamber. Compared to maize plants inoculated with A. brasilense alone, plants that were co-inoculated with these consortia showed accelerated growth after 15 days. Follow-up root colonization assays revealed that A. brasilense colonized at higher levels on roots from the co-inoculated seedlings. These findings demonstrate a new method for rapid bioprospecting of root and soil communities for complementary PGPB and for developing multispecies consortia with potential use as next-generation biofertilizers.

DegS protease regulates the motility, chemotaxis, and colonization of Vibrio cholerae.

In bacteria, DegS protease functions as an activating factor of the σE envelope stress response system, which ultimately activates the transcription of stress response genes in the cytoplasm. On the basis of high-throughput RNA sequencing, we have previously found that degS knockout inhibits the expression of flagellum synthesis- and chemotaxis-related genes, thereby indicating that DegS may be involved in the regulation of V. cholerae motility. In this study, we examined the relationships between DegS and motility in V. cholerae. Swimming motility and chemotaxis assays revealed that degS or rpoE deletion promotes a substantial reduction in the motility and chemotaxis of V. cholerae, whereas these activities were restored in ΔdegS::degS and ΔdegSΔrseA strains, indicating that DegS is partially dependent on σE to positively regulate V. cholerae activity. Gene-act network analysis revealed that the cAMP-CRP-RpoS signaling pathway, which plays an important role in flagellar synthesis, is significantly inhibited in ΔdegS mutants, whereas in response to the overexpression of cyaA/crp and rpoS in the ΔdegS strain, the motility and chemotaxis of the ΔdegS + cyaA/crp and ΔdegS + rpoS strains were partially restored compared with the ΔdegS strain. We further demonstrated that transcription levels of the flagellar regulatory gene flhF are regulated by DegS via the cAMP-CRP-RpoS signaling pathway. Overexpression of the flhF gene in the ΔdegS strain partially restored motility and chemotaxis. In addition, suckling mouse intestinal colonization experiments indicated that the ΔdegS and ΔrpoE strains were characterized by the poor colonization of mouse intestines, whereas colonization efficacy was restored in the ΔdegSΔrseA, ΔdegS + cyaA/crp, ΔdegS + rpoS, and ΔdegS + flhF strains. Collectively, our findings indicate that DegS regulates the motility and chemotaxis of V. cholerae via the cAMP-CRP-RpoS-FlhF pathway, thereby influencing the colonization of suckling mouse intestines.

OmpC-Dependent Bile Tolerance Contributes to E. coli Colonization of the Mammalian Intestine.

Escherichia coli persistently colonizes the mammalian intestine by mechanisms that are not fully understood. Previously, we found when streptomycin-treated mice were fed E. coli MG1655, the intestine selected for envZ missense mutants that outcompeted the wild type. The better-colonizing envZ mutants had a higher level of OmpC and reduced OmpF. This suggested the EnvZ/OmpR two-component system and outer membrane proteins play a role in colonization. In this study, we show that wild-type E. coli MG1655 outcompetes an envZ-ompR knockout mutant. Moreover, ompA and ompC knockout mutants are outcompeted by the wild type, while an ompF knockout mutant colonizes better than the wild type. Outer membrane protein gels show the ompF mutant overproduces OmpC. An ompC mutant is more sensitive to bile salts than the wild type and ompF mutant. The ompC mutant initiates colonization slowly because it is sensitive to physiological concentrations of bile salts in the intestine. Overexpression of ompC under the control of a constitutive promoter confers a colonization advantage only when ompF is deleted. These results indicate that fine-tuning of OmpC and OmpF levels is needed to maximize competitive fitness in the intestine. RNA sequencing reveals the EnvZ/OmpR two-component system is active in the intestine: ompC is upregulated and ompF is downregulated. While other factors could also contribute to the advantage provided by OmpC, we provide evidence that OmpC is important for E. coli to colonize the intestine because its smaller pore size excludes bile salts or other unknown toxic substances, while OmpF is deleterious because its larger pore size allows bile salts or other unknown toxic substances to enter the periplasm. IMPORTANCE Every mammalian intestine is colonized with Escherichia coli. Although E. coli is one of the most studied model organisms, how it colonizes the intestine is not fully understood. Here, we investigated the role of the EnvZ/OmpR two-component system and outer membrane proteins in colonization of the mouse intestine by E. coli. We report that an ompC mutant is a poor colonizer, while an ompF mutant, which overproduces OmpC, outcompetes the wild type. OmpF has a larger pore size that allows toxic bile salts or other toxic compounds into the cell and is deleterious for colonization of the intestine. OmpC has a smaller pore size and excludes bile salts. Our findings provide insights into why E. coli fine-tunes the levels of OmpC and OmpF during colonization via the EnvZ/OmpR two-component system.

Influence of Hive Cover Modifications and Ambient Microclimate on Colonization of African Honeybees in Awka, Nigeria

Poor colonization of hives by African honeybees is one of the constraints facing the beekeeping sector. This study aimed to determine the influence of some hive cover modifications on the colonization of African honeybees in Awka. The hive covers of top bar hives were modified by insulating them with different materials and grouped into four treatments, namely: T1 (plywood), T2 (warped boards), T3 (polyvinyl chloride ceiling material), and T4 (foam). At various months, data on the ambient microclimate (temperature and relative humidity) and the number of hives colonized per treatment were collected. The colonization rate was highest in treatment 1 (100%), followed by treatment 2 (33.33%) while treatments 3 and 4 (0.00%) had the least. Hive treatments did not significantly affect the colonization of honeybees (p = 0.09). Treatment 1 colonized in the months of July, October, and November, while that of Treatment 2 occurred in December. Months had significant effect on the mean colonization of African honeybees (p&lt;0.05). The mean colonization of hives and ambient temperature had a negative correlation while there was a positive correlation between the mean colonization of hives and ambient relative humidity. Hive covers insulated with ply wood were recommended since they achieved earlier colonization than other treatments.

Construction of a Novel MYC-Associated ceRNA Regulatory Network to Identify Prognostic Biomarkers in Colon Adenocarcinoma.

Colorectal cancer (CRC) includes colon adenocarcinoma (COAD) and rectal adenocarcinoma (READ). Competitive endogenous RNA (ceRNA) is crucial for cancer pathogenesis. Abnormal expression of MYC is generally associated with a poor colon adenocarcinoma prognosis. The present study aimed to identify a novel MYC-associated ceRNA regulatory network and identify potential prognostic markers associated with COAD. We obtained the transcriptome sequencing profiles of 462 COAD cases from the TCGA database and analyzed differentially expressed genes (DEGs) in MYC high expression (MYChigh) and MYC low expression (Myclow) tumors. We identified an important lncRNA, LINC00114, which effectively predicts overall survival and plays a protective role in COAD. Moreover, the LINC00114/miR-216a-5p axis was identified as a clinical prognostic model. The predicted target genes of the LINC00114/miR-216a-5p axis include uromodulin Like 1 (UMODL1) and oncoprotein induced transcript 3 (OIT3), which are closely related to the survival and prognosis of COAD patients. In summary, we constructed a novel ceRNA regulatory network and identified potential biomarkers for the targeted therapy and prognosis of COAD.

Response of Chinese mitten crab (Eriocheir sinensis) intestinal microbiota to commercial probiotic application

Probiotics have emerged as promising alternatives to antibiotics for maintaining the health of the Chinese mitten crab (CMC, Eriocheir sinensis). However, the efficacy of probiotic application in CMC culture ecosystems remains uncertain. Intestinal microbiota is often as comprehensive indicators of aquatic animal health, but the effects of probiotics on CMC intestinal microbiota remain poorly understood. In this study, we used 16S rRNA gene amplicon sequencing to investigate the mechanisms underlying the changes of the intestinal microbial communities following short-term probiotic application in CMC culture. Our data showed there was poor probiotic colonization in the intestines of pond-cultured CMCs. The short-term application of probiotics had no significant impact on the alpha-diversity for the microbial communities; however, it significantly changed the beta-diversity. Remarkably, the probiotics promoted butanoate metabolism of the CMC intestinal microbiota. According to network analysis, the microbiome of the CMC intestine manifested rapid responses to probiotic application, and cooperation between intestinal microbial communities may have been enhanced. Taken together, our results provide preliminary insights into the roles of probiotics in the CMC intestinal microbial ecosystem.

Ex Vivo Human and Porcine Skin Effectively Model Candida auris Colonization, Differentiating Robust and Poor Fungal Colonizers.

Candida auris proliferates and persists on the skin of patients, often leading to health care-associated infections with high mortality. Here, we describe 2 clinically relevant skin models and show that C. auris grows similarly on human and porcine skin. Additionally, we demonstrate that other Candida spp., including those with phylogenetic similarity to C. auris, do not display high growth in the skin microenvironment. These studies highlight the utility of 2 ex vivo models of C. auris colonization that allow reproducible differentiation among Candida spp., which should be a useful tool for comparison of C. auris clinical isolates and genetically mutated strains.

Regeneration from seed in herbaceous understorey of ancient woodlands of temperate Europe.

European ancient woodlands are subject to land use change, and the distribution of herbaceous understorey species may be threatened because of their poor ability to colonize isolated forest patches. The regeneration niche can determine the species assembly of a community, and seed germination traits may be important descriptors of this niche. We analysed ecological records for 208 herbaceous species regarded as indicators of ancient woodlands in Europe and, where possible, collated data on seed germination traits, reviewed plant regeneration strategies and measured seed internal morphology traits. The relationship between plant regeneration strategies and ecological requirements was explored for 57 species using ordination and classification analysis. Three regeneration strategies were identified. Species growing in closed-canopy areas tend to have morphological seed dormancy, often requiring darkness and low temperatures for germination, and their shoots emerge in early spring, thus avoiding the competition for light from canopy species. These species are separated into two groups: autumn and late winter germinators. The third strategy is defined by open-forest plants with a preference for gaps, forest edges and riparian forests. They tend to have physiological seed dormancy and germinate in light and at higher temperatures, so their seedlings emerge in spring or summer. Seed germination traits are fundamental to which species are good or poor colonizers of the temperate forest understorey and could provide a finer explanation than adult plant traits of species distribution patterns. Seed dormancy type, temperature stratification and light requirements for seed germination are important drivers of forest floor colonization patterns and should be taken in account when planning successful ecological recovery of temperate woodland understories.

Phage co-transport with hyphal-riding bacteria fuels bacterial invasion in a water-unsaturated microbial model system

Nonmotile microorganisms often enter new habitats by co-transport with motile microorganisms. Here, we report that also lytic phages can co-transport with hyphal-riding bacteria and facilitate bacterial colonization of a new habitat. This is comparable to the concept of biological invasions in macroecology. In analogy to invasion frameworks in plant and animal ecology, we tailored spatially organized, water-unsaturated model microcosms using hyphae of Pythium ultimum as invasion paths and flagellated soil-bacterium Pseudomonas putida KT2440 as carrier for co-transport of Escherichia virus T4. P. putida KT2440 efficiently dispersed along P. ultimum to new habitats and dispatched T4 phages across air gaps transporting ≈0.6 phages bacteria−1. No T4 displacement along hyphae was observed in the absence of carrier bacteria. If E. coli occupied the new habitat, T4 co-transport fueled the fitness of invading P. putida KT2440, while the absence of phage co-transport led to poor colonization followed by extinction. Our data emphasize the importance of hyphal transport of bacteria and associated phages in regulating fitness and composition of microbial populations in water-unsaturated systems. As such co-transport seems analogous to macroecological invasion processes, hyphosphere systems with motile bacteria and co-transported phages could be useful models for testing hypotheses in invasion ecology.

Poor Biointegration of Porcine Acellular Dermal Matrix Associated with Unfavorable Gingival Healing: A Report of Three Cases

The aim of the present work was to explain the poor biointegration of acellular dermal xenogeneic matrix, leading to an unfavorable gingival healing following a grafting procedure for the treatment of soft tissue deficiencies. Numerous works have demonstrated the successful use of acellular dermal matrix (ADM) in soft tissue augmentation procedures. However, spare human investigations reported adverse healing outcomes at microscopic level. Three patients showing various soft tissue deficiencies (recession, gingival thickening) requiring a gingival augmentation were grafted using an ADM porcine acellular dermal matrices (pADM) as a soft tissue substitute. For this purpose, appropriate soft tissue augmentation surgeries were performed and the grafted pADM was left for proper healing. Biopsies were harvested from two out of the three patients, respectively, at 11 and 27 weeks in order to conduct a histological evaluation of the pADM's doubtful biointegration. Moreover, the ultrastructural analysis of pADM was performed using scanning electron microscopy, and additional histological procedures were used to assess its ability to support human gingival fibroblast cultures. Signs of gingival inflammation persisted several months postoperatively. Histologically, numerous inflammatory cells characterized the grafted site. Indeed, the high number of foreign body giant cell granulomas and the very densified newly formed collagen fibers highlighted a fibrotic process within gingival connective tissue. The ultrastructural and histological analysis showed that pADM was characterized by very thick and dense collagen bundles demonstrating a nonphysiological collagen network organization. Cell culture experiments showed fibroblasts proliferating on the matrix surface, sparing its deeper part, even though the collagen matrix degradation seemed to occur following a gradient from the pADM surface inward. The unfavorable clinical results may be caused by the poor colonization of matrix cells and poor angiogenesis leading to the inadequate biointegration of pADM. Hence, the pADM structure in terms of porosity and degradability should be further investigated. The present cases highlighted a poor integration of pADM following soft tissue grafting procedures, which was caused by the inadequate ultrastructure of the used pADM. Therefore, despite the utility of such tissue substitutes, their manufacturing improvement could be required to obtain a better biointegration.

Extinction risk is linked to lifestyle in freshwater gastropods

AbstractAimFreshwater ecosystems and their biota are severely endangered by global change today, and predicted extinction levels are skyrocketing for many taxa. Most studies have focused on entire clades, while approaches testing for selective extinction risk with respect to ecological traits are rare. As studies are typically based on modern faunas, the generality of the detected patterns in the context of the current biodiversity crisis remains uncertain. We use a dataset of fossil and modern freshwater gastropods to investigate extinction probability in dependence of lifestyle and geographic distribution.LocationEurope, Miocene to present‐day.MethodsWe performed generalized linear mixed modelling to test for a relationship between extinction probability and taxonomic group (Caenogastropoda vs. Hygrophila, reflecting different lifestyles) and range size, while using time as random effect. Extinction and survival of modern representatives was predicted based on IUCN conservation status. To identify the types of faunas with elevated extinction risk with respect to lifestyle, we tested for a relationship between the proportion of Caenogastropoda and lake surface area and geological duration using generalized linear models.ResultsWe found a clear relationship between extinction likelihood and lifestyle, which is linked to differences in range sizes and is independent of geological time. Caenogastropoda are more prone to go extinct. A strong positive relationship between the proportion of Caenogastropoda and geological duration was found, showing that Caenogastropoda are more dominant in long‐lived lakes.Main conclusionsThe elevated extinction risk of caenogastropods is linked to their smaller geographic ranges, which reflects their comparably poor colonization ability, and urges enhanced conservation efforts. Their high diversity and high degree of endemism in long‐lived lakes render, especially these archives of evolution important conservators of biodiversity. As most of these lakes are under severe anthropogenic pressure, concerted conservation measures are needed to ensure the survival of their unique biota.