TY  - THES
A1  - Lehenberger, Maximilian
T1  - Ecology and Evolution of symbiotic microbial communities in fungus farming ambrosia beetles
T1  - Ökologie und Evolution von symbiotischen mikrobiellen Gemeinschaften in Pilzzüchtenden Ambrosiakäfern
N2  - Within my PhD project I gained several novel insights into the poorly investigated 
symbiotic world of fungus farming ambrosia beetles and their bark beetle ancestors, 
where I especially focused on physiological interactions and capabilities of 
associated fungal symbionts. Here, (i) I could confirm the association of mutualistic 
Phialophoropsis fungi with the ambrosia beetle genus Trypodendron and found hints 
for a possible new Phialophoropsis species in T. signatum and T. domesticum. 
Moreover, I could show that mutualistic fungi of Trypodendron ambrosia beetles are 
able to decompose major woody polysaccharides such as cellulose and xylan. 
Additionally, (ii) I provided the first images using micro-computed tomography (µCT) 
of the formerly unknown structure of the mycetangium of Trypodendron leave. (iii) I 
could confirm a general tolerance towards ethanol in mutualistic ambrosia beetle 
fungi, while antagonistic fungi as well as most examined fungal bark beetle 
associates (e.g. possibly tree-defense detoxifying species) were highly sensitive to 
even low concentrations of ethanol. Further, (iv) I found that natural galleries of 
ambrosia beetles are highly enriched with several biologically important elements 
(such as N, P, S, K, Mg) compared to the surrounding woody tissue and suggest that 
mutualistic fungi are translocating and concentrating elements from the immediate
surrounding xylem to the beetles galleries. Furthermore, (v) I could show that various 
fungi associated with bark and ambrosia beetles (mutualists, possibly beneficial 
symbionts) are emitting several volatile organic compounds mostly within aliphatic 
and aromatic alcohols and esters, while non-mutualistic and free living species were 
generally emitting a lower number and amount of volatiles. Finally, especially bark 
and ambrosia beetle fungi were found to incorporate several amino acids, from which 
some are especially important for the production of certain volatile organic
compounds. Amino acid content also indicated a higher nutritional value for certain 
species. Here, I propose that especially volatile organic compounds are widespread 
key players in maintaining various symbioses between fungi and beetles, as already 
proven by a recent study on the bark beetle Ips typographus (as well as for some 
other bark beetle-fungus symbioses, see summary in Kandasamy et al. 2016) and 
also suggested for ambrosia beetles.
N2  - Im Rahmen meiner Promotion konnte ich einige neue Einblicke in die symbiotische 
Welt von Pilz-züchtenden Ambrosiakäfern sowie ihren direkten Vorfahren den 
Borkenkäfern, mit speziellen Fokus auf physiologische Interaktionen und 
Besonderheiten der assoziierten Pilzen, erlangen. Hier konnte ich (i) die Assoziation 
der europäischen Trypodendron Arten mit mutualistischen Pilzen in der Gattung 
Phialophoropsis generell bestätigen und fand des weiteren Hinweise auf eine 
vermutlich neue Phialophoropsis Art in den beiden Ambrosiakäfern T. domesticum
und T. signatum. Außerdem konnte ich zeigen, dass mutualistische Pilze, welche mit 
Ambrosiakäfern der Gattung Trypodendron assoziiert sind, wesentliche 
Polysaccharide im Holz (Cellulose und Xylan) abbauen können. Zusätzlich war es 
mir möglich, (ii) erstmals die Pilzsporen übertragende Struktur „Mycetangium“ des 
Ambrosiakäfers Trypodendron laeve zu untersuchen und durch den Einsatz von 
Mikro-Computertomographie (µCT) somit die ersten detaillierten Aufnahmen bereit 
zu stellen. Außerdem bestätigten und ergänzten meine Studien, (iii) das Ethanol� Toleranz unter Ambrosiakäfer-Pilzen eine wohl sehr weit verbreitete Besonderheit ist, 
wohingegen für die Käfer bzw. für die Ambrosiapilze schädliche Pilze stark durch 
schon geringe Ethanol-Konzentrationen gehemmt werden. Interessanterweise 
wurden auch nahezu alle mit Borkenkäfern assoziierten Pilze stark durch Ethanol 
gehemmt. Des Weiteren konnte ich zeigen, (iv) das natürliche Brutsysteme von 
Ambrosiakäfern, im Gegensatz zu unbesiedeltem Splintholz, sehr stark mit 
verschiedenen essentiellen Elementen (wie etwa N, P, S, K und Mg) angereichert 
sind. Sehr wahrscheinlich ist es den Pilzsymbionten möglich, Elemente aus 
unmittelbar umliegendem Splintholz abzuziehen und diese in den Brutsystemen der 
Käfer entsprechend anzureichern. Außerdem konnte ich zeigen, (v) das nahezu alle 
untersuchten Borken- und Ambrosiakäfer-Pilze (Mutualisten sowie möglicherweise 
begünstigende Symbionten) eine Vielzahl an flüchtigen Inhaltsstoffen produzieren, 
welche sich hier vor allem in die Gruppe der aliphatischen und aromatischen 
Alkohole und Ester eingliedern. Nicht mutualistische Pilze sowie freilebende Arten 
produzierten im Vergleich eine geringere Anzahl an unterschiedlichen flüchtigen 
Inhaltsstoffen und emittierten zumeist geringere Mengen davon. Schließlich konnte 
ich zeigen, dass vor allem Pilze welche mit Borken- und Ambrosiakäfern assoziiert 
sind, größere Mengen an verschiedenen Aminosäuren in ihrer Biomasse einbauen, 
von welchen einige besonders wichtig sind um bestimmte flüchtige Inhaltsstoffe zu 
bilden. Dazu kann durch den Anteil der gefundenen Aminosäuren in der 
Pilzbiomasse auf den nährstoffreichen Charakter der Pilze geschlossen werden.
Diese flüchtigen Inhaltsstoffe haben mit sehr hoher Wahrscheinlichkeit eine 
essenzielle Rolle innerhalb einer Vielzahl an Käfer-Pilz Symbiosen und sind 
vermutlich maßgeblich an dem Erfolg und Bestand solcher Symbiosen beteiligt. Dies 
wurde bereits in jüngster Vergangenheit bei dem Borkenkäfer Ips typographus mit 
seinen assoziierten Pilzen gezeigt (aber auch bei einigen weiteren Borkenkäfern, 
siehe Zusammenfassung von Kandasamy et al., 2016), während es bei 
Ambrosiakäfern bisher nur vermutet wurde.
KW  - Ambrosia beetles
KW  - Ambrosiakäfer
KW  - bark beetles
KW  - fungi
KW  - symbiosis
KW  - mutualism
KW  - Borkenkäfer
KW  - Pilze
KW  - Symbiose
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-241546
PB  - Fungal Ecology, Frontiers in Microbiology, Deutsche Gesellschaft für allgemeine und angewandte Entomologie
ER  - 
TY  - JOUR
A1  - Chilaka, Cynthia Adaku
A1  - Obidiegwu, Jude Ejikeme
A1  - Chilaka, Augusta Chinenye
A1  - Atanda, Olusegun Oladimeji
A1  - Mally, Angela
T1  - Mycotoxin regulatory status in Africa: a decade of weak institutional efforts
JF  - Toxins
N2  - Food safety problems are a major hindrance to achieving food security, trade, and healthy living in Africa. Fungi and their secondary metabolites, known as mycotoxins, represent an important concern in this regard. Attempts such as agricultural, storage, and processing practices, and creation of awareness to tackle the menace of fungi and mycotoxins have yielded measurable outcomes especially in developed countries, where there are comprehensive mycotoxin legislations and enforcement schemes. Conversely, most African countries do not have mycotoxin regulatory limits and even when available, are only applied for international trade. Factors such as food insecurity, public ignorance, climate change, poor infrastructure, poor research funding, incorrect prioritization of resources, and nonchalant attitudes that exist among governmental organisations and other stakeholders further complicate the situation. In the present review, we discuss the status of mycotoxin regulation in Africa, with emphasis on the impact of weak mycotoxin legislations and enforcement on African trade, agriculture, and health. Furthermore, we discuss the factors limiting the establishment and control of mycotoxins in the region.
KW  - fungi
KW  - mycotoxin
KW  - legislation
KW  - food safety
KW  - food security
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-278941
SN  - 2072-6651
VL  - 14
IS  - 7
ER  - 
TY  - JOUR
A1  - Götz, Ralph
A1  - Panzer, Sabine
A1  - Trinks, Nora
A1  - Eilts, Janna
A1  - Wagener, Johannes
A1  - Turrà, David
A1  - Di Pietro, Antonio
A1  - Sauer, Markus
A1  - Terpitz, Ulrich
T1  - Expansion Microscopy for Cell Biology Analysis in Fungi
JF  - Frontiers in Microbiology
N2  - Super-resolution microscopy has evolved as a powerful method for subdiffraction-resolution fluorescence imaging of cells and cellular organelles, but requires sophisticated and expensive installations. Expansion microscopy (ExM), which is based on the physical expansion of the cellular structure of interest, provides a cheap alternative to bypass the diffraction limit and enable super-resolution imaging on a conventional fluorescence microscope. While ExM has shown impressive results for the magnified visualization of proteins and RNAs in cells and tissues, it has not yet been applied in fungi, mainly due to their complex cell wall. Here we developed a method that enables reliable isotropic expansion of ascomycetes and basidiomycetes upon treatment with cell wall degrading enzymes. Confocal laser scanning microscopy (CLSM) and structured illumination microscopy (SIM) images of 4.5-fold expanded sporidia of Ustilago maydis expressing fluorescent fungal rhodopsins and hyphae of Fusarium oxysporum or Aspergillus fumigatus expressing either histone H1-mCherry together with Lifeact-sGFP or mRFP targeted to mitochondria, revealed details of subcellular structures with an estimated spatial resolution of around 30 nm. ExM is thus well suited for cell biology studies in fungi on conventional fluorescence microscopes.
KW  - Expansion microscopy
KW  - fluorescence microscopy
KW  - fungi
KW  - sporidia
KW  - hyphae
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-202569
SN  - 1664-302X
VL  - 11
ER  - 
TY  - JOUR
A1  - Böhm, Lena
A1  - Torsin, Sanda
A1  - Tint, Su Hlaing
A1  - Eckstein, Marie Therese
A1  - Ludwig, Tobias
A1  - Pérez, J. Christian
T1  - The yeast form of the fungus Candida albicans promotes persistence in the gut of gnotobiotic mice
JF  - PLoS Pathogens
N2  - Many microorganisms that cause systemic, life-threatening infections in humans reside as harmless commensals in our digestive tract. Yet little is known about the biology of these microbes in the gut. Here, we visualize the interface between the human commensal and pathogenic fungus Candida albicans and the intestine of mice, a surrogate host. Because the indigenous mouse microbiota restricts C. albicans settlement, we compared the patterns of colonization in the gut of germ free and antibiotic-treated conventionally raised mice. In contrast to the heterogeneous morphologies found in the latter, we establish that in germ free animals the fungus almost uniformly adopts the yeast cell form, a proxy of its commensal state. By screening a collection of C. albicans transcription regulator deletion mutants in gnotobiotic mice, we identify several genes previously unknown to contribute to in vivo fitness. We investigate three of these regulators—ZCF8, ZFU2 and TRY4—and show that indeed they favor the yeast form over other morphologies. Consistent with this finding, we demonstrate that genetically inducing non-yeast cell morphologies is detrimental to the fitness of C. albicans in the gut. Furthermore, the identified regulators promote adherence of the fungus to a surface covered with mucin and to mucus-producing intestinal epithelial cells. In agreement with this result, histology sections indicate that C. albicans dwells in the murine gut in close proximity to the mucus layer. Thus, our findings reveal a set of regulators that endows C. albicans with the ability to endure in the intestine through multiple mechanisms.
KW  - Candida albicans
KW  - deletion mutagenesis
KW  - gastrointestinal tract
KW  - fungi
KW  - regulator genes
KW  - gene regulation
KW  - mouse models
KW  - fungal genetics
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159120
VL  - 13
IS  - 10
ER  - 
TY  - JOUR
A1  - Arenas, Andrés
A1  - Roces, Flavio
T1  - Avoidance of plants unsuitable for the symbiotic fungus in leaf-cutting ants: Learning can take place entirely at the colony dump
JF  - PLoS ONE
N2  - Plants initially accepted by foraging leaf-cutting ants are later avoided if they prove unsuitable for their symbiotic fungus. Plant avoidance is mediated by the waste produced in the fungus garden soon after the incorporation of the unsuitable leaves, as foragers can learn plant odors and cues from the damaged fungus that are both present in the recently produced waste particles. We asked whether avoidance learning of plants unsuitable for the symbiotic fungus can take place entirely at the colony dump. In order to investigate whether cues available in the waste chamber induce plant avoidance in naïve subcolonies, we exchanged the waste produced by subcolonies fed either fungicide-treated privet leaves or untreated leaves and measured the acceptance of untreated privet leaves before and after the exchange of waste. Second, we evaluated whether foragers could perceive the avoidance cues directly at the dump by quantifying the visits of labeled foragers to the waste chamber. Finally, we asked whether foragers learn to specifically avoid untreated leaves of a plant after a confinement over 3 hours in the dump of subcolonies that were previously fed fungicide-treated leaves of that species. After the exchange of the waste chambers, workers from subcolonies that had access to waste from fungicide-treated privet leaves learned to avoid that plant. One-third of the labeled foragers visited the dump. Furthermore, naïve foragers learned to avoid a specific, previously unsuitable plant if exposed solely to cues of the dump during confinement. We suggest that cues at the dump enable foragers to predict the unsuitable effects of plants even if they had never been experienced in the fungus garden.
KW  - leaves
KW  - ants
KW  - fungi
KW  - foraging
KW  - animal sociality
KW  - social systems
KW  - learning
KW  - symbiosis
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-157559
VL  - 12
IS  - 3
ER  - 
TY  - JOUR
A1  - Römer, Daniela
A1  - Bollazzi, Martin
A1  - Roces, Flavio
T1  - Carbon dioxide sensing in an obligate insect-fungus symbiosis: CO\(_{2}\) preferences of leaf-cutting ants to rear their mutualistic fungus
JF  - PLoS ONE
N2  - Defense against biotic or abiotic stresses is one of the benefits of living in symbiosis. Leaf-cutting ants, which live in an obligate mutualism with a fungus, attenuate thermal and desiccation stress of their partner through behavioral responses, by choosing suitable places for fungus-rearing across the soil profile. The underground environment also presents hypoxic (low oxygen) and hypercapnic (high carbon dioxide) conditions, which can negatively influence the symbiont. Here, we investigated whether workers of the leaf-cutting ant Acromyrmex lundii use the CO\(_{2}\) concentration as an orientation cue when selecting a place to locate their fungus garden, and whether they show preferences for specific CO\(_{2}\) concentrations. We also evaluated whether levels preferred by workers for fungus-rearing differ from those selected for themselves. In the laboratory, CO\(_{2}\) preferences were assessed in binary choices between chambers with different CO\(_{2}\) concentrations, by quantifying number of workers in each chamber and amount of relocated fungus. Leaf-cutting ants used the CO\(_{2}\) concentration as a spatial cue when selecting places for fungus-rearing. A. lundii preferred intermediate CO\(_{2}\) levels, between 1 and 3%, as they would encounter at soil depths where their nest chambers are located. In addition, workers avoided both atmospheric and high CO\(_{2}\) levels as they would occur outside the nest and at deeper soil layers, respectively. In order to prevent fungus desiccation, however, workers relocated fungus to high CO\(_{2}\) levels, which were otherwise avoided. Workers’ CO\(_{2}\) preferences for themselves showed no clear-cut pattern. We suggest that workers avoid both atmospheric and high CO\(_{2}\) concentrations not because they are detrimental for themselves, but because of their consequences for the symbiotic partner. Whether the preferred CO\(_{2}\) concentrations are beneficial for symbiont growth remains to be investigated, as well as whether the observed preferences for fungus-rearing influences the ants’ decisions where to excavate new chambers across the soil profile.
KW  - fungi
KW  - nesting habits
KW  - carbon dioxide
KW  - ants
KW  - social systems
KW  - humidity
KW  - symbiosis
KW  - fungal physiology
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159561
VL  - 12
IS  - 4
ER  - 
TY  - JOUR
A1  - Halboth, Florian
A1  - Roces, Flavio
T1  - The construction of ventilation turrets in Atta vollenweideri leaf-cutting ants: Carbon dioxide levels in the nest tunnels, but not airflow or air humidity, influence turret structure
JF  - PLoS ONE
N2  - Nest ventilation in the leaf-cutting ant Atta vollenweideri is driven via a wind-induced mechanism. On their nests, workers construct small turrets that are expected to facilitate nest ventilation. We hypothesized that the construction and structural features of the turrets would depend on the colony’s current demands for ventilation and thus might be influenced by the prevailing environmental conditions inside the nest. Therefore, we tested whether climate-related parameters, namely airflow, air humidity and CO\(_{2}\) levels in the outflowing nest air influenced turret construction in Atta vollenweideri. In the laboratory, we simulated a semi-natural nest arrangement with fungus chambers, a central ventilation tunnel providing outflow of air and an aboveground building arena for turret construction. In independent series, different climatic conditions inside the ventilation tunnel were experimentally generated, and after 24 hours, several features of the built turret were quantified, i.e., mass, height, number and surface area (aperture) of turret openings. Turret mass and height were similar in all experiments even when no airflow was provided in the ventilation tunnel. However, elevated CO\(_{2}\) levels led to the construction of a turret with several minor openings and a larger total aperture. This effect was statistically significant at higher CO\(_{2}\) levels of 5% and 10% but not at 1% CO\(_{2}\). The construction of a turret with several minor openings did not depend on the strong differences in CO\(_{2}\) levels between the outflowing and the outside air, since workers also built permeated turrets even when the CO\(_{2}\) levels inside and outside were both similarly high. We propose that the construction of turrets with several openings and larger opening surface area might facilitate the removal of CO\(_{2}\) from the underground nest structure and could therefore be involved in the control of nest climate in leaf-cutting ants.
KW  - carbon dioxide
KW  - animal sociality
KW  - ants
KW  - fungi
KW  - humidity
KW  - social systems
KW  - nesting habits
KW  - fungal structure
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159133
VL  - 12
IS  - 11
ER  - 
TY  - JOUR
A1  - Römer, Daniela
A1  - Roces, Flavio
T1  - Nest Enlargement in Leaf-Cutting Ants: Relocated Brood and Fungus Trigger the Excavation of New Chambers
N2  - During colony growth, leaf-cutting ants enlarge their nests by excavating tunnels and chambers housing their fungus gardens and brood. Workers are expected to excavate new nest chambers at locations across the soil profile that offer suitable environmental conditions for brood and fungus rearing. It is an open question whether new chambers are excavated in advance, or will emerge around brood or fungus initially relocated to a suitable site in a previously-excavated tunnel. In the laboratory, we investigated the mechanisms underlying the excavation of new nest chambers in the leaf-cutting ant Acromyrmex lundi. Specifically, we asked whether workers relocate brood and fungus to suitable nest locations, and to what extent the relocated items trigger the excavation of a nest chamber and influence its shape. When brood and fungus were exposed to unfavorable environmental conditions, either low temperatures or low humidity, both were relocated, but ants clearly preferred to relocate the brood first. Workers relocated fungus to places containing brood, demonstrating that subsequent fungus relocation spatially follows the brood deposition. In addition, more ants aggregated at sites containing brood. When presented with a choice between two otherwise identical digging sites, but one containing brood, ants' excavation activity was higher at this site, and the shape of the excavated cavity was more rounded and chamber-like. The presence of fungus also led to the excavation of rounder shapes, with higher excavation activity at the site that also contained brood. We argue that during colony growth, workers preferentially relocate brood to suitable locations along a tunnel, and that relocated brood spatially guides fungus relocation and leads to increased digging activity around them. We suggest that nest chambers are not excavated in advance, but emerge through a self-organized process resulting from the aggregation of workers and their density-dependent digging behavior around the relocated brood and fungus.
KW  - fungi
KW  - ants
KW  - fungal structure
KW  - fungal pathogens
KW  - foraging
KW  - humidity
KW  - pupae
KW  - fungal diseases
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-112860
ER  - 
TY  - JOUR
A1  - Roces, Flavio
A1  - Pielström, Steffen
T1  - Soil Moisture and  Excavation Behaviour in the Chaco Leaf-Cutting Ant (Atta vollenweideri): Digging Performance and Prevention of Water Inflow into the Nest
N2  - The Chaco leaf-cutting ant Atta vollenweideri is native to the clay-heavy soils of the Gran Chaco region in South America. Because of seasonal floods, colonies are regularly exposed to varying moisture across the soil profile, a factor that not only strongly influences workers' digging performance during nest building, but also determines the suitability of the soil for the rearing of the colony's symbiotic fungus. In this study, we investigated the effects of varying soil moisture on behaviours associated with underground nest building in A. vollenweideri. This was done in a series of laboratory experiments using standardised, plastic clay-water mixtures with gravimetric water contents ranging from relatively brittle material to mixtures close to the liquid limit. Our experiments showed that preference and group-level digging rate increased with increasing water content, but then dropped considerably for extremely moist materials. The production of vibrational recruitment signals during digging showed, on the contrary, a slightly negative linear correlation with soil moisture. Workers formed and carried clay pellets at higher rates in moist clay, even at the highest water content tested. Hence, their weak preference and low group-level excavation rate observed for that mixture cannot be explained by any inability to work with the material. More likely, extremely high moistures may indicate locations unsuitable for nest building. To test this hypothesis, we simulated a situation in which workers excavated an upward tunnel below accumulated surface water. The ants stopped digging about 12 mm below the interface soil/water, a behaviour representing a possible adaptation to the threat of water inflow field colonies are exposed to while digging under seasonally flooded soils. Possible roles of soil water in the temporal and spatial pattern of nest growth are discussed.
KW  - ants
KW  - fungi
KW  - surface water
KW  - vibration
KW  - acoustic signals
KW  - physical properties
KW  - analysis of variance
KW  - fungal structure
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-111298
ER  - 
TY  - JOUR
A1  - Fuji, Shigeo
A1  - Kapp, Markus
A1  - Einsele, Hermann
T1  - Monitoring of Pathogen-Specific T-Cell Immune Reconstitution after Allogeneic Hematopoietic Stem Cell Transplantation
JF  - Frontiers in Immunology
N2  - The clinical outcome after allogeneic hematopoietic stem cell transplantation (HSCT) has been significantly improved during the last decades with regard to the reduction in organ failure, infection, and severe acute graft-versus-host disease. However, severe complications due to infectious diseases are still one of the major causes of morbidity and mortality after allogeneic HSCT, in particular in patients receiving haploidentical HSCT or cord blood transplant due to a slow and often incomplete immune reconstitution. In order to improve the immune control of pathogens without an increased risk of alloreactivity, adoptive immunotherapy using highly enriched pathogen-specificT cells offers a promising approach. In order to identify patients who are at high risk for infectious diseases, several monitoring assays have been developed with potential for the guidance of immunosuppressive drugs and adoptive immunotherapy in clinical practice. In this article, we aim to give a comprehensive overview regarding current developments of T-cell monitoring techniques focusing on T cells against viruses and fungi. In particular, we will focus on rather simple, fast, non-labor-intensive, cellular assays which could be integrated in routine clinical screening approaches.
KW  - immune reconstitution
KW  - virus
KW  - fungi
KW  - T cell
KW  - allogeneic stem cell transplantation
Y1  - 2013
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-129250
VL  - 4
IS  - 276
ER  -