Bart Lievens

KU Leuven | ku leuven · Department of Microbial and Molecular Systems (M²S)

Microorganisms living in and on macroorganisms may produce microbial volatile compounds (mVOCs) that characterise organismal odours. The mVOCs might thereby provide a reliable cue to carnivorous enemies in locating their host or prey. Parasitism by parasitoid wasps might alter the microbiome of their caterpillar host, affecting organismal odours an...

The genus Rosenbergiella is one of the most frequent bacterial inhabitants of flowers and a usual member of the insect microbiota worldwide. To date, there is only one publicly available Rosenbergiella genome, corresponding to the type strain of Rosenbergiella nectarea (8N4T), which precludes a detailed analysis of intra-genus phylogenetic relation...

Insect communities consist of species from several trophic levels that have to forage for suitable resources among and within larger patches of non‐resources. To locate their resources, insects use diverse stimuli, including olfactory, visual, acoustic, tactile and gustatory cues. While most research has focused on cues derived from plants and othe...

Although microbial communities of insects from larval to adult stage have been increasingly investigated in recent years, little is still known about the diversity and composition of egg‐associated microbiomes. In this study, we used high‐throughput amplicon sequencing and quantitative PCR to get a better understanding of the microbiome of insect e...

Ethiopian Arabica coffee is produced in different agroforestry systems which differ in forest management intensity. In forest coffee systems (FC), coffee shrubs grow naturally in the understory of Afromontane forests with little human intervention, whereas in semi-forest coffee systems (SFC) thinning of the canopy and removal of the understory is a...

Entomopathogenic fungi can adopt an endophytic lifestyle and provide protection against insect herbivores and plant pathogens. So far, most studies have focused on Beauveria bassiana to increase plant resistance against abiotic and biotic stresses, while only little is known for other entomopathogenic fungi. In this study, we investigated whether r...

Black soldier fly larvae (BSFL) belong to the most widely reared insects as an alternative protein source at industrial scale. Bacteria in the larval gut can provide benefits for the animal, though some bacteria can also be pathogenic for the insect. Accurate characterization of the BSFL microbiota is important for the production of BSFL in terms o...

The floral nectar of angiosperms harbors a variety of microorganisms that depend predominantly on animal visitors for their dispersal. Although some members of the genus Acinetobacter and all currently known species of Rosenbergiella are thought to be adapted to thrive in nectar, there is limited information about the response of these bacteria to...

Floral nectar is ubiquitously colonized by a variety of microorganisms among which yeasts and bacteria are the most common. Microorganisms inhabiting floral nectar can alter several nectar traits, including nectar odor by producing microbial volatile organic compounds (mVOCs). Evidence showing that mVOCs can affect the foraging behavior of insect p...

Sour beers produced by barrel-aging of conventionally fermented beers are becoming increasingly popular. However, as the intricate interactions between the wood, the microbes and the beer are still unclear, wood maturation often leads to inconsistent end products with undesired sensory properties. Previous research on industrial barrel-aging of bee...

Wood-ageing of conventionally fermented beers is gaining increased attention in the production of sour beers with a noteworthy balance between sourness, wood aroma and flavour complexity. Besides the extraction of wood-derived compounds into the beer, wood-aged sours owe their layered flavour profile to the activity of a variety of wild microorgani...

Insect communities consist of several trophic levels that have to forage for suitable resources among and within larger patches of non-resources. To locate their resources, insects use diverse stimuli, including olfactory, visual, acoustic, tactile and gustatory cues. While most research has focused on cues derived from plants and other insects, th...

Sour beers produced by barrel-aging of conventionally fermented beers are becoming increasingly popular. However, as the intricate interactions between the wood, the microbes and the beer are still unclear, wood maturation often leads to inconsistent end products with undesired sensory properties. Previous research on industrial barrel-aging of bee...

Black soldier fly larvae (BSFL) belong to the most widely reared insect species as an alternative protein source at industrial scale. Bacteria in the larval gut can provide benefits for the animal, though some bacteria can also be pathogenic for the insect. Accurate characterization of the BSFL microbiota is important for the production of BSFL in...

A correction to this paper has been published: https://doi.org/10.1007/s00248-021-01755-2

Barrel‐ageing of conventionally fermented beers is becoming increasingly popular in recent years, but only very little is known about the underlying process. In this study, we show that wood species significantly affects the bacterial community composition, beer chemistry and sensory characteristics throughout 38 weeks of barrel‐ageing. Whereas the...

The rhizosphere is a complex ecosystem consisting of microbes in the interface between growth medium and plant roots, which affects plant productivity and health. This is one of the few studies analysing bacterial communities present in the rhizosphere of hydroponically grown plants. Tomato grown under hydroponic conditions is prone to hairy root d...

Background The microbiome of many insects consists of a diverse community of microorganisms that can play critical roles in the functioning and overall health of their hosts. Although the microbial communities of insects have been studied thoroughly over the past decade, little is still known about how biotic interactions affect the microbial commu...

There is increasing evidence that microorganisms, particularly fungi and bacteria, emit volatile compounds that mediate the foraging behaviour of insects and therefore have the potential to affect key ecological relationships. However, to what extent microbial volatiles affect the olfactory response of insects across different trophic levels remain...

Aims: This study evaluated pH reduction and microbial growth during fermentation of maize stover (MS) mixed with banana pseudostem (BPS) under South Ethiopian conditions. Materials and results: The MS and BPS were chopped and mixed into six treatments (T): 80% BPS plus 20% DMS (T1), 70% BPS plus 30% DMS (T2), 40% BPS plus 60% FMS (fresh MS) (T3)...

A detailed evaluation of eight bacterial isolates from floral nectar and animal visitors to flowers shows evidence that they represent three novel species in the genus Acinetobacter . Phylogenomic analysis shows the closest relatives of these new isolates are Acinetobacter apis , Acinetobacter boissieri and Acinetobacter nectaris , previously descr...

Floral nectar is commonly colonized by yeasts and bacteria, whose growth largely depends on their capacity to assimilate nutrient resources, withstand high osmotic pressures, and cope with unbalanced carbon-to-nitrogen ratios. Although the basis of the ecological success of these microbes in the harsh environment of nectar is still poorly understoo...

AimsArbuscular Mycorrhizal Fungi (AMF) are ubiquitous soil microorganisms playing a vital role in the functioning of agricultural ecosystems. Although AMF are generally considered to have a low host specificity, it has been suggested that modern plant breeding has selected crop genotypes that are more selectively associated with AMF, possibly resul...

The use of wooden barrels is a traditional technique for fermentation and maturation of beer, most prominently present in the production of traditional sour beers like Belgian lambic beer and red-brown acidic ales. In recent years, barrel ageing of beer is also gaining an increased interest to add notes of wood or aromas from the previously matured...

Currently, one of the most important challenges is to provide sufficient and affordable food and energy for a fast-growing world population, alongside preserving natural habitats and maintaining biodiversity. About 35% of the global food production depends on animals for pollination. In recent years, an alarming worldwide decline in pollinators has...

Hairy root disease (HRD) caused by rhizogenic Agrobacterium biovar 1 strains affect tomato, cucumber, eggplant, and bell pepper grown in hydroponic greenhouses and can cause considerable yield losses worldwide. Recently, Paenibacillus xylanexedens strains (ST15.15/027 and AD117) with antagonistic activity against rhizogenic agrobacteria were identi...

In this study, we report on the development of two quantitative PCR assays for the detection and quantification of the soilborne plant pathogen Phytophthora cactorum causing root and crown rot of strawberry. The assays rely on the use of SYBR Green I chemistry and use the internal transcribed spacer region 2 (ITS2) and the Ras-related protein gene...

Background: Recent studies have shown that microorganisms emit volatile compounds that affect insect behaviour. However, it remains largely unclear whether microbes can be exploited as a source of attractants to improve biological control of insect pests. In this study, we used a combination of coupled gas chromatography-electroantennography (GC-E...

Currently, there is a strong interest in barrel ageing of finished, conventionally fermented beers, as a novel way to produce sour beers with a rich and complex flavour profile. The production process, however, remains largely a process of trial and error, often resulting in profit losses and inconsistency in quality. To improve product quality and...

About 90% of all flowering plant species are pollinated by animals. Animals are attracted to flowers because they often provide food in the form of nectar and pollen. While floral nectar is assumed to be initially sterile, it commonly becomes colonized by yeasts after animals have visited the flowers. Although yeast communities in floral nectar app...

Understanding the relationship between population genetic structure and phenotypic diversity is a fundamental question in evolutionary biology. Yeasts display wide genetic diversity and exhibit remarkably diverse heterotrophic metabolisms that allow a variety of niche occupations. However, little is known about how intra-species genetic population...

Flowers produce an array of nutrient-rich exudates in which microbes can thrive, making them hotspots for microbial abundance and diversity. During a diversity study of yeasts inhabiting the flowers of Metrosideros polymorpha (Myrtaceae) in the Hawai'i Volcanoes National Park (HI, USA), five isolates were found to represent two novel species. Morph...

n Ethiopia, conservation of hay and crop residues are typically practised in an open space, where the sunlight, rainfall and deterioration might cause leaching of nutrients. This study was conducted to evaluate the fermentation and microbial quality of dry and fresh maize stovers mixed with banana pseudostem in different proportions. The dry maize...

There is increasing evidence that microorganisms emit a wide range of volatile compounds (mVOCs, microbial volatile organic compounds) that act as insect semiochemicals, and therefore play an important role in insect behaviour. Although it is generally believed that phylogenetically closely related microbes tend to have similar phenotypic character...

Integrated pest management (IPM) is today a widely accepted pest management strategy to select and use the most efficient control tactics and at the same time reduce over-dependence on chemical insecticides and their potentially negative environmental effects. One of the main pillars of IPM is biological control. While biological control programs o...

With edible insects being increasingly produced, food safety authorities have called for the determination of microbiological challenges posed to human health. Here, we find that the bacterial endospore fraction in industrially reared mealworm and cricket samples is largely comprised of Bacillus cereus group members that can pose insect or human he...

Edible insects are characterised by high microbial numbers of which the bacterial endospores fraction can survive (thermal) processing. It is unknown, however, which bacterial species occur as endospore in edible insects and what impact they have on food safety. Additionally, edible insects have never been explored for the presence of foodborne vir...

1.To locate mating partners and essential resources such as food, oviposition sites and shelter, insects rely to a large extent on chemical cues. While most research has focused on cues derived from plants and insects, there is mounting evidence that indicates that microorganisms emit volatile compounds that may play an important role in insect beh...

Flowers offer a wide variety of substrates suitable for fungal growth. However, the mycological study of flowers has only recently begun to be systematically addressed from an ecological point of view. Most research on the topic carried out during the last decade has focused on studying the prevalence and diversity of flower-inhabiting yeasts, desc...

Hairy root disease (HRD), also known as “crazy roots”, caused by rhizogenic agrobacteria has in recent years become a serious problem in greenhouse hydroponic cultivation of tomato, eggplant and cucumber in many European countries. The typical symptoms include excessive development of roots, which leads to a more pronounced vegetative growth of the...

Production of many agricultural crops and fruits strongly depends on pollinators. For instance, pome fruits such as apple and pear are highly dependent on pollination for fruit set, fruit quality, and yield. Nectar is often inhabited by microbes, most often yeasts and bacteria, which may change nectar quality and therefore also affect plant-pollina...

House flies (Musca domestica) are widespread, synanthropic filth flies commonly found on decaying matter, garbage, and feces as well as human food. They have been shown to vector microbes, including clinically relevant pathogens. Previous studies have demonstrated that house flies carry a complex and variable prokaryotic microbiota, but the main dr...

During long-term extra-terrestrial missions, food is limited and waste is generated. By recycling valuable nutrients from this waste via regenerative life support systems, food can be produced in space. Astronauts' urine can, for instance, be nitrified by micro-organisms into a liquid nitrate fertilizer for plant growth in space. Due to stringent c...

We describe the isolation and characterization of three bacterial isolates from the common house fly, Musca domestica, caught in Londerzeel, Belgium and Huye District, Rwanda. Although isolated from distinct geographical locations, the strains show >99 % identical 16S rRNA gene sequences and are <95 % identical to type strains of Apibacter species....

Our aim was to quantify the extent to which nutrient pollution explains arbuscular mycorrhizal fungal community richness and composition. Europe. 2014–2016. Arbuscular mycorrhizal fungi. We sampled soils of calcareous and acidic grasslands and roots of 34 host plant species across a large geographical gradient of atmospheric nitrogen deposition and...

The genus Lactobacillus is known to be extremely diverse and consists of different phylogenetic groups that show a diversity that is roughly equal to the expected diversity of a typical bacterial genus. One of the most prominent phylogenetic groups within this genus is the Lactobacillus plantarum group, which contains the understudied Lactobacillus...

Understanding how animals learn is crucial to interpreting animal behaviour. Flower-visiting insects, such as bees and parasitoids, are excellent animal models to study visual and olfactory learning, including memory phenomena. The diversity of resources flower-visiting insects exploit predisposes them to learn and remember the colours, shapes and...

In this study, lactic acid bacteria strains were screened for the development of (a) starter culture(s) specific for enset (Ensete ventricosum) fermentation. To this end, 158 isolates grown on de Man, Rogosa and Sharpe agar were obtained from fermenting enset and traditional starter material. They were screened based on their biochemical characteri...

Rice is an essential food crop that nourishes more than 50% of the world population. In many regions of Bangladesh rice production is constrained by high soil salinity and heavy metal contamination due to irrigation practices. Plants may naturally overcome such stress through mutualistic interactions with arbuscular mycorrhizal fungi (AMF). Yet, li...

This study aimed to gain insight into the microbial quality, safety and bacterial community composition of black soldier fly larvae (Hermetia illucens) reared at different facilities on a variety of organic waste streams. For seven rearing cycles, both on laboratory-scale and in large-scale facilities at several locations, the microbiota of the lar...

Currently, there is a strong interest in sour beers, with more breweries producing sour styles and sales continuing to increase. There are many different ways for producing sour beer, offering breweries a variety of opportunities to pursue new beverages and diversify their portfolio. These methods range from modern kettle souring and short term mix...

Enset (Ensete ventricosum) is a drought tolerant food crop consumed in Ethiopia after fermentation into 'kocho'. In most enset growing regions of Ethiopia, traditional starters are prepared in local households and added to the scraped enset mash to aid the fermentation. The preparation of the starters differs among ethnic groups. The aim of this st...

The genus Lactobacillus is known to be extremely diverse and consists of different phylogenetic groups that show a diversity roughly equal to the expected diversity of a typical bacterial genus. One of the most prominent phylogenetic groups within this genus is the Lactobacillus plantarum group which contains the understudied Lactobacillus mudanjia...

Coffea arabica is native to the Afromontane forests of southwestern Ethiopia, the leading African country in Arabica coffee production. The intensity of coffee leaf rust (CLR), a fungal disease of growing concern to coffee farmers, was assessed in eight coffee berry disease-resistant C. arabica varieties planted at three different altitudes. Diseas...

Aims The present study was conducted to assess the effect of three different fermentation systems on fermentation of enset into kocho. Methods and Results Nine enset plants were processed, mixed and fermented in either a pit, a bamboo basket or a Sauerkraut jar. Samples were taken on days 1, 7, 15, 31, 60 and 90. Moisture content and pH generally...

Many reptiles, amphibians, mammals, and insects practice some form of hibernation during which their metabolic rate is drastically reduced. This allows them to conserve energy and survive the harsh winter conditions with little or no food. While it can be expected that a reduction in host metabolism has a substantial influence on the gut microbial...

Gut microbial communities are critical for the health of many insect species. However, little is known about how gut microbial communities respond to anthropogenic changes and how such changes affect host-pathogen interactions. In this study, we used deep sequencing to investigate and compare the composition of gut microbial communities within the...

Relative abundance (%) of bacterial families in the guts (midgut and ileum) of bumblebee queens (Bombus terrestris) from five different locations. Sampled locations represent two habitat types, including forest (S1-F and S2-F) and urbanized habitats (S3-U, S4-U and S5-U). (TIF)

Maximum-likelihood tree derived from the V4 region of the 16S rRNA gene sequence (250 bp) of Bifidobacteriaceae occurring in the digestive tract of Bombus, showing the phylogenetic position of the bifidobacteria found in this study (OTU24, 38 and 786). Type strains of the closest relatives were also included in the tree. (PDF)

Fungal community composition at the level of operational taxonomic units (OTUs) within the midgut and ileum in bumblebee queens (Bombus terrestris) having fungi. Specimens with fungi were caught in the forest habitats S1-F and S2-F (18 specimens) and the urbanized habitat S3-U (2 specimens). All other investigated bumblebees were negative for fungi...

Identification of fungal operational taxonomic units (OTUs) according to the RDP Warcup fungal ITS training set (v2) and distribution over the investigated samples. (XLSX)

Relative abundance (%) of the bacterial phyla found in the guts (midgut and ileum) of bumblebee queens (Bombus terrestris) from five different locations. Sampled locations represent two habitat types, including forest (S1-F and S2-F) and urbanized habitats (S3-U, S4-U and S5-U). (TIF)

Overview of samples (Bombus terrestris queens) investigated in this study, including sampling information and diversity measures. (XLSX)

Primer design and sample-specific barcodes. (XLSX)

Rarefaction curves showing the number of gut bacterial (A) and fungal (B) operational taxonomic units (OTUs) per bumblebee queen (Bombus terrestris) from five different locations. Sampled locations represent two habitat types, including forest (S1-F (yellow) and S2-F (orange)) and urbanized habitats (S3-U (purple), S4-U (dark blue) and S5-U (light...

Identification of bacterial operational taxonomic units (OTUs) according to the Silva v1.23 database and distribution over the investigated samples. (XLSX)

Maximum-likelihood tree derived from the V4 region of the 16S rRNA gene sequence (250 bp) of Lactobacillaceae occurring in the digestive tract of Bombus and Apis, showing the phylogenetic position of the lactobacilli found in this study (OTU6, 20, 23, 37, 136, 189, 194, 282, 729, 1304, 1601 and 1697). Type strains of the closest relatives were also...