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Aufbauend auf einer pflanzensoziologischen Analyse werden die Lebensformen und die wasserleitenden und wasserspeichernden Strukturen epiphytischer Bryophyten entlang eines Transektes vom östlichen Kongobecken (Tieflandstufe) zum zentralafrikanischen Grabenrand (tropischsubalpine/ alpine Stufe; BRYOTROP III-Transekt) analysiert und in Beziehung zu den Moosgesellschaften und dem ökologischen Höhenstufengradienten gesetzt. Grundlage für die Interpretation ist der mittlere Gruppenmengenanteil. In der tropischen Tieflandstufe dominiert die Lebensform Decke, die eine auffallende Korrelation zu dem Strukturmerkmal Wassertasche und Wassersack sowie Sippen der Verwandtschaftskreise Jubulaceae, Lejeuneaceae und Radulaceae zeigt. In der sich anschließenden humiden Bergwaldstufe kommt es zu einem deutlichen Wechsel im Lebensformen- und Anpassungsspektrum. Wedelbildende Plagiochila- Arten bestimmen die Physiognomie der primären Regenwälder, deren abstehendes, planares Sproßsystem sich sowohl zum Nebelkämmen (Wasserdampfkondensation) eignet als auch als Anpassung an die lichtarmen Bedingungen interpretiert wird. Sonderfälle stellen in der oberen Bergwaldstufe die Epiphyten der Bergbambuswälder, mit ähnlichen Anpassungssyndromen wie die der Tieflandstufe, und die der offeneren, anthropogenen Bergwälder dar, deren laubmoosreiche Gesellschaften ökomorphologisch reicher strukturiert sind (Korrelation von Filz und Hochrasen mit Hyalozyten, Rhizoidenfilz und Zentralstrang). In der durch starke Klimaschwankungen gekennzeichneten tropisch-subalpinen Stufe dominieren Decke, Filz und posterförmige Hochrasen, die durch wasserspeichernde Strukturen (Alarzellen, Hyalozyten, Rhizoidenfilz, Zentralstrang) auf die bereits xerischen Bedingungen (Trockenstress) hindeuten. Hohe Anteile im Spektrum erreichen hier aber auch Strukturen zum Nebelkämmen (Nutzung der aus der Bergwaldstufe häufig aufsteigenden Treibnebel) und die Rinnenbildung.
Life strategies of epiphytic bryophytes are studied along an altitudinal gradient from the eastern Congo basin (tropical lowland zone) to the mountains of the East-African graben (tropical subalpine/alpine Zone; BRYOTROP III-transect). Three strategies, Colonists, Perennial shuttle species and Perennial stayers can be observed, which are further subdivided according to their reproduction tactic (high sexual reproductive effort, high asexual reproductive effort, moderately or low sexual and asexual reproductive effort). Of these, only taxa with a long life span (perennials) are of importance, indicating the unchanging and constant ecological conditions and long-lasting microsites, provided by the epiphytic habitats. The basis for the life strategy pattern analysis along the altitudinal gradient were plant sociological investigations and the determination of the mean percentage cover values for the different life strategy categories. By this, the distribution and occurrence of the different strategies within the communities and the altitudinal zones can be shown.
Incidence of an intracellular multiplication niche amongst Acinetobacter baumannii clinical isolates
(2021)
The spread of antibiotic resistant Acinetobacter baumannii poses a significant threat to public health worldwide. This nosocomial bacterial pathogen can be associated with life-threatening infections, particularly in intensive care units. A. baumannii is mainly described as an extracellular pathogen with restricted survival within cells. This study shows that a subset of A. baumannii clinical isolates extensively multiply within non-phagocytic immortalized and primary cells, without the induction of apoptosis, and with bacterial clusters visible up to 48 hours after infection. This phenotype was observed for the A. baumannii C4 strain associated with high mortality in a hospital outbreak, and the A. baumannii ABC141 strain which wasn’t isolated from an infection site but was found to be hyperinvasive. Intracellular multiplication of these A. baumannii strains occurred within spacious single membrane-bound vacuoles, labeled with the lysosomal associate membrane protein (LAMP1). However, these compartments excluded lysotracker, an indicator of acidic pH, suggesting that A. baumannii can divert its trafficking away from the lysosomal degradative pathway. These compartments were also devoid of autophagy features. A high-content microscopy screen of 43 additional A. baumannii clinical strains highlighted various phenotypes: (1) the majority of strains remained extracellular, (2) a significant proportion was capable of invasion and limited persistence, and (3) two strains efficiently multiplied within LAMP1-positive vacuoles, one of which was also hyperinvasive. These data identify an intracellular niche for specific A. baumannii clinical strains that enables extensive multiplication in an environment protected from host immune responses and out of reach from many antibiotics.
Importance Multidrug resistant Acinetobacter baumannii strains are associated with significant morbidity and mortality in hospitals world-wide. Understanding their pathogenicity is critical for improving therapeutics. Although A. baumannii can steadily adhere to surfaces and host cells, most bacteria remain extracellular. Recent studies have shown that a small proportion of bacteria can invade cells but present limited survival. We have found that some A. baumannii clinical isolates can establish a specialized intracellular niche that sustains extensive intracellular multiplication for a prolonged time without induction of cell death. We propose that this intracellular compartment allows A. baumannii to escape the cell’s normal degradative pathway, protecting bacteria from host immune responses and potentially hindering antibiotic accessibility. This may contribute to A. baumannii persistence, relapsing infections and enhanced mortality in susceptible patients. A high-content microscopy-based screen confirmed this pathogenicity trait is present in other clinical isolates. There is an urgent need for new antibiotics or alternative antimicrobial approaches, particularly to combat carbapenem-resistant A. baumannii. The discovery of an intracellular niche for this pathogen as well as hyperinvasive isolates may help guide the development of antimicrobial therapies and diagnostics in the future.
Mobile genetic elements (MGEs), especially multidrug-resistance plasmids, are major vehicles for the dissemination of antimicrobial resistance determinants. Herein, we analyse the MGEs in three extensively drug-resistant (XDR) Klebsiella pneumoniae isolates from Germany. Whole genome sequencing (WGS) is performed using Illumina and MinION platforms followed by core-genome multi-locus sequence typing (MLST). The plasmid content is analysed by conjugation, S1-pulsed-field gel electrophoresis (S1-PFGE) and Southern blot experiments. The K. pneumoniae isolates belong to the international high-risk clone ST147 and form a cluster of closely related isolates. They harbour the blaOXA-181 carbapenemase on a ColKP3 plasmid, and 12 antibiotic resistance determinants on an multidrug-resistant (MDR) IncR plasmid with a recombinogenic nature and encoding a large number of insertion elements. The IncR plasmids within the three isolates share a high degree of homology, but present also genetic variations, such as inversion or deletion of genetic regions in close proximity to MGEs. In addition, six plasmids not harbouring any antibiotic resistance determinants are present in each isolate. Our study indicates that genetic variations can be observed within a cluster of closely related isolates, due to the dynamic nature of MGEs. The mobilome of the K. pneumoniae isolates combined with the emergence of the XDR ST147 high-risk clone have the potential to become a major challenge for global healthcare.
Incidence of an intracellular multiplication niche among Acinetobacter baumannii clinical isolates
(2022)
The spread of antibiotic-resistant Acinetobacter baumannii poses a significant threat to public health worldwide. This nosocomial bacterial pathogen can be associated with life-threatening infections, particularly in intensive care units. A. baumannii is mainly described as an extracellular pathogen with restricted survival within cells. This study shows that a subset of A. baumannii clinical isolates extensively multiply within nonphagocytic immortalized and primary cells without the induction of apoptosis and with bacterial clusters visible up to 48 h after infection. This phenotype was observed for the A. baumannii C4 strain associated with high mortality in a hospital outbreak and the A. baumannii ABC141 strain, which was isolated from the skin but was found to be hyperinvasive. Intracellular multiplication of these A. baumannii strains occurred within spacious single membrane-bound vacuoles, labeled with the lysosomal associate membrane protein (LAMP1). However, these compartments excluded lysotracker, an indicator of acidic pH, suggesting that A. baumannii can divert its trafficking away from the lysosomal degradative pathway. These compartments were also devoid of autophagy features. A high-content microscopy screen of 43 additional A. baumannii clinical isolates highlighted various phenotypes, and (i) the majority of isolates remained extracellular, (ii) a significant proportion was capable of invasion and limited persistence, and (iii) three more isolates efficiently multiplied within LAMP1-positive vacuoles, one of which was also hyperinvasive. These data identify an intracellular niche for specific A. baumannii clinical isolates that enables extensive multiplication in an environment protected from host immune responses and out of reach of many antibiotics.
IMPORTANCE Multidrug-resistant Acinetobacter baumannii isolates are associated with significant morbidity and mortality in hospitals worldwide. Understanding their pathogenicity is critical for improving therapeutic management. Although A. baumannii can steadily adhere to surfaces and host cells, most bacteria remain extracellular. Recent studies have shown that a small proportion of bacteria can invade cells but present limited survival. We have found that some A. baumannii clinical isolates can establish a specialized intracellular niche that sustains extensive intracellular multiplication for a prolonged time without induction of cell death. We propose that this intracellular compartment allows A. baumannii to escape the cell’s normal degradative pathway, protecting bacteria from host immune responses and potentially hindering antibiotic accessibility. This may contribute to A. baumannii persistence, relapsing infections, and enhanced mortality in susceptible patients. A high-content microscopy-based screen confirmed that this pathogenicity trait is present in other clinical A. baumannii isolates. There is an urgent need for new antibiotics or alternative antimicrobial approaches, particularly to combat carbapenem-resistant A. baumannii. The discovery of an intracellular niche for this pathogen, as well as hyperinvasive isolates, may help guide the development of antimicrobial therapies and diagnostics in the future.
Temperate forests are increasingly subject to natural disturbance by stand replacing windthrows or bark-beetle attacks. Forests are commonly salvage logged after disturbance, whereby substantial parts of biological legacies, such as surviving trees and deadwood, are removed. Despite increasing concerns about the ecological consequences of salvage logging operations, our knowledge on the effects on the soil microbiome and associated functioning remains limited.
Here, we studied soil fungal communities, decomposition processes, and soil organic matter dynamics in 21 intact or disturbed, temperate Norway spruce stands about one decade after they were damaged by windthrow or bark-beetle attacks. Disturbed stands comprised different post-disturbance management, i.e. deadwood retention and salvage logged plots. We used high-throughput sequencing and ergosterol measurements to explore fungal communities and biomass, and enzyme assays to study decomposition processes.
Disturbance shifted soil fungal communities from ectomycorrhizal to saprotrophic dominated assemblages. Fungal biomass declined with decreasing tree abundance after disturbance. Activities of organic matter degrading enzymes declined by ca. 30–80% after disturbance. The relative abundance of ectomycorrhizal fungi was positively related to enzymatic activities. Tree biomass parameters and amounts of deadwood retained were positively related to fungal biomass, certain ectomycorrhizal taxa, and relative ectomycorrhizal fungal abundance among disturbed stands, which, in turn, was associated with higher enzymatic activities.
Our findings demonstrate a significant response of soil fungal communities to natural forest disturbance and salvage logging, with consequences for decomposition and soil organic matter dynamics. We conclude that the retention of surviving trees and deadwood as biological legacies attenuated associated changes to a significant extent, highlighting their importance for the preservation of ectomycorrhizal fungi and the maintenance of decomposition processes after disturbance.
Background: Alterations in the DNA methylation pattern are a hallmark of leukemias and lymphomas. However, most epigenetic studies in hematologic neoplasms (HNs) have focused either on the analysis of few candidate genes or many genes and few HN entities, and comprehensive studies are required. Methodology/Principal Findings: Here, we report for the first time a microarray-based DNA methylation study of 767 genes in 367 HNs diagnosed with 16 of the most representative B-cell (n = 203), T-cell (n = 30), and myeloid (n = 134) neoplasias, as well as 37 samples from different cell types of the hematopoietic system. Using appropriate controls of B-, T-, or myeloid cellular origin, we identified a total of 220 genes hypermethylated in at least one HN entity. In general, promoter hypermethylation was more frequent in lymphoid malignancies than in myeloid malignancies, being germinal center mature B-cell lymphomas as well as B and T precursor lymphoid neoplasias those entities with highest frequency of gene-associated DNA hypermethylation. We also observed a significant correlation between the number of hypermethylated and hypomethylated genes in several mature B-cell neoplasias, but not in precursor B- and T-cell leukemias. Most of the genes becoming hypermethylated contained promoters with high CpG content, and a significant fraction of them are targets of the polycomb repressor complex. Interestingly, T-cell prolymphocytic leukemias show low levels of DNA hypermethylation and a comparatively large number of hypomethylated genes, many of them showing an increased gene expression. Conclusions/Significance: We have characterized the DNA methylation profile of a wide range of different HNs entities. As well as identifying genes showing aberrant DNA methylation in certain HN subtypes, we also detected six genes—DBC1, DIO3, FZD9, HS3ST2, MOS, and MYOD1—that were significantly hypermethylated in B-cell, T-cell, and myeloid malignancies. These might therefore play an important role in the development of different HNs.