Composition of epiphytic bacterial communities differs on petals and leaves.

The epiphytic bacterial communities colonising roots and leaves have been described for many plant species. In contrast, microbiologists have rarely considered flowers of naturally growing plants. We identified bacteria isolated from the surface of petals and leaves of two plant species, Saponaria officinalis (Caryophyllaceae) and Lotus corniculatus (Fabaceae). The bacterial diversity was much lower on petals than on leaves of the same plants. Moreover, the bacterial communities differed strongly in composition: while Pseudomonadaceae and Microbacteriaceae were the most abundant families on leaves, Enterobacteriaceae dominated the floral communities. We hypothesise that antibacterial floral volatiles trigger the low diversity on petals, which is supported by agar diffusion assays using substances emitted by flowers and leaves of S. officinalis. These results suggest that bacteria should be included in the interpretation of floral traits, and possible effects of bacteria on pollination are proposed and discussed.

Stingless bees use terpenes as olfactory cues to find resin sources.

Insects largely rely on olfactory cues when seeking and judging information on nests, partners, or resources. Bees are known to use volatile compounds-besides visual cues-to find flowers suitable for pollen and nectar collection. Tropical stingless bees additionally collect large amounts of plant resins for nest construction, nest maintenance, nest defense, and to derive chemical constituents for their cuticular profiles. We here demonstrate that stingless bees of Borneo also use olfactory cues to find tree resins. They rely on volatile mono- and sesquiterpenes to locate or recognize known resin sources. Moreover, by modifying resin extracts, we found that stingless bees do not use the entire resin bouquet but relative proportions of several terpenes. In doing so, the bees are able to learn specific tree resin profiles and distinguish between tree species and partly even tree individuals.

Parabiotic associations between tropical ants: equal partnership or parasitic exploitation?

1. The huge diversity of symbiotic associations among animals and/or plants comprises both mutualisms and parasitisms. Most symbioses between social insect species, however, involve social parasites, while mutual benefits have been only suspected for some parabiotic associations - two colonies that share a nest. 2. In the rainforest of Borneo, we studied parabiotic associations between the ants Crematogaster modiglianii and Camponotus rufifemur. Parabiotic nests were regularly found inside hollow tree trunks, most likely initiated by Cr. modiglianii. This species frequently nested without its partner, whereas we never found non-parabiotic Ca. rufifemur nests. We experimentally investigated potential benefits, potential interference competition for food (as a probable cost), and foraging niches of both species. 3. The two species never showed aggressive interactions and amicably shared food resources. However, Cr. modiglianii had a wider temporal and spatial foraging range than Ca. rufifemur, always found baits before Ca. rufifemur and recruited more efficiently. Camponotus rufifemur probably benefited from following pheromone trails of Cr. modiglianii. In turn, Ca. rufifemur was significantly more successful in defending the nest against alien ants. Crematogaster modiglianii hence may profit from its partner's defensive abilities. 4. In neotropical parabioses, epiphytes grown in 'ant-gardens' play a crucial role in the association, e.g. by stabilization of nests. Hemiepiphytic Poikilospermum cordifolium (Cecropiaceae) seedlings and saplings frequently grew in the entrances of parabiotic nests in Borneo, obviously dispersed by the ants. In cafeteria experiments, both parabiotic ants carried its elaiosome-bearing seeds into the nest. However, P. cordifolium does not provide additional nest space, contrasting with neotropical ant-gardens. 5. The parabiotic association appears beneficial for both ant species, the main benefits being nest initiation by Cr. modiglianii and interspecific trail-following (for Ca. rufifemur), and, in turn, nest defence by Ca. rufifemur (for Cr. modiglianii). However, Ca. rufifemur seems to be more dependent on its partner than vice versa.

SysBioMed report: advancing systems biology for medical applications.

The following report selects and summarises some of the conclusions and recommendations generated throughout a series of workshops and discussions that have lead to the publication of the Science Policy Briefing (SPB) Nr. 35, published by the European Science Foundation. (Large parts of the present text are directly based on the ESF SPB. Detailed recommendations with regard to specific application areas are not given here but can be found in the SPB. Issues related to mathematical modelling, including training and the need for an infrastructure supporting modelling are discussed in greater detail in the present text.)The numerous reports and publications about the advances within the rapidly growing field of systems biology have led to a plethora of alternative definitions for key concepts. Here, with 'mathematical modelling' the authors refer to the modelling and simulation of subcellular, cellular and macro-scale phenomena, using primarily methods from dynamical systems theory. The aim of such models is encoding and testing hypotheses about mechanisms underlying the functioning of cells. Typical examples are models for molecular networks, where the behaviour of cells is expressed in terms of quantitative changes in the levels of transcripts and gene products. Bioinformatics provides essential complementary tools, including procedures for pattern recognition, machine learning, statistical modelling (testing for differences, searching for associations and correlations) and secondary data extracted from databases.Dynamical systems theory is the natural language to investigate complex biological systems demonstrating nonlinear spatio-temporal behaviour. However, the generation of experimental data suitable to parameterise, calibrate and validate such models is often time consuming and expensive or not even possible with the technology available today. In our report, we use the term 'computational model' when mathematical models are complemented with information generated from bioinformatics resources. Hence, 'the model' is, in reality, an integrated collection of data and models from various (possibly heterogeneous) sources. The present report focuses on a selection of topics, which were identified as appropriate case studies for medical systems biology, and adopts a particular perspective which the authors consider important. We strongly believe that mathematical modelling represents a natural language with which to integrate data at various levels and, in doing so, to provide insight into complex diseases: 1. Modelling necessitates the statement of explicit hypotheses, a process which often enhances comprehension of the biological system and can uncover critical points where understanding is lacking. 2. Simulations can reveal hidden patterns and/or counter-intuitive mechanisms in complex systems. 3. Theoretical thinking and mathematical modelling constitute powerful tools to integrate and make sense of the biological and clinical information being generated and, more importantly, to generate new hypotheses that can then be tested in the laboratory.Medical Systems Biology projects carried out recently across Europe have revealed a need for action: 4. While the need for mathematical modelling and interdisciplinary collaborations is becoming widely recognised in the biological sciences, with substantial implications for the training and research funding mechanisms within this area, the medical sciences have yet to follow this lead. 5. To achieve major breakthroughs in Medical Systems Biology, existing academic funding schemes for large-scale projects need to be reconsidered. 6. The hesitant stance of the pharmaceutical industry towards major investment in systems biology research has to be addressed. 7. Leading medical journals should be encouraged to promote mathematical modelling.