It is generally accepted that planktonic bacteria in dilute suspensions are not mechanically coupled and do not show correlated motion. The mechanical coupling of cells is a trait that develops upon transition into a biofilm, a microbial community of self-aggregated bacterial cells. Here we employ optical tweezers to show that bacteria in dilute suspensions are mechanically coupled and show long-range correlated motion. The strength of the coupling increases with the growth of liquid bacterial culture. The matrix responsible for the mechanical coupling is composed of cell debris and extracellular polymer material. The fragile network connecting cells behaves as viscoelastic liquid of entangled extracellular polymers. Our findings point to physical connections between bacteria in dilute bacterial suspensions that may provide a mechanistic framework for understanding of biofilm formation, osmotic flow of nutrients, diffusion of signal molecules in quorum sensing, or different efficacy of antibiotic treatments at low and high bacterial densities. Paper represents scientific outreach in the filed of bacterial biofilms. It exhibits methodological expertise and technological possibilities of program group members in the field of microscopy.
COBISS.SI-ID: 33363673
Amoebae serve as hosts for various intracellular bacteria, including human pathogens. These microbes are able to overcome amoebal defense mechanisms and successfully establish a niche for replication, which is usually the cytoplasm. Here, we report on the discovery of a bacterial symbiont that is located inside the nucleus of its Hartmannella sp. host. This symbiont, tentatively named ‘Candidatus Nucleicultrix amoebiphila’, is only moderately related to known bacteria (B90% 16S and 23S rRNA sequence similarity) and member of a novel clade of protist symbionts affiliated with the Rickettsiales and Rhodospirillales. Screening of 16S rRNA amplicon data sets revealed a broad distribution of these bacteria in freshwater and soil habitats. ‘Candidatus Nucleicultrix amoebiphila’ traffics within 6 h post infection to the host nucleus. Maximum infection levels are reached after 96–120 h, at which time point the nucleus is pronouncedly enlarged and filled with bacteria. Transmission of the symbionts occurs vertically upon host cell division but may also occur horizontally through host cell lysis. Although we observed no impact on the fitness of the original Hartmannella sp. host, the bacteria are rather lytic for Acanthamoeba castellanii. Intranuclear symbiosis is an exceptional phenomenon, and amoebae represent an ideal model system to further investigate evolution and underlying molecular mechanisms of these unique microbial associations. The article covers two expertise of the program, namely microbe-invertebrate symbiosis and electron microscopy; it paws the way towards new understanding of microbe-eucariont symbiosis.
COBISS.SI-ID: 3043407
Identifying drivers of geographic variation in range size is one of main challenges in macroecology. It has been observed in many taxonomic groups that species ranges increase toward the north. The main broad mechanisms that have been proposed to explain geographic variation in species range size are: habitat area/heterogeneity, climate seasonality and longterm climate variability. So far, it has been difficult to disentangle their relative role, particularly as temperature seasonality often covaries with the amplitude of long-term temperature oscillations. Here subterranean species offer unique study systems, as they live in habitats with absence of temperature seasonality. In this contribution, we were able to shed new light onto this debate by providing the first continental-scale analysis of range size and beta diversity in groundwater habitats. We compiled occurrence data for 1570 groundwater crustacean species in Europe, and used various statistical approaches to study the patterns of present day ranges, as well as relative importance of different components of betadiversity. Median range size increased with latitude above 43° N. Range size of individual species was positively correlated to latitude, even after accounting for phylogenetic effects. Long-term temperature variability accounted for a substantially higher variation in median range size of groundwater crustaceans across Europe than precipitation seasonality and habitat heterogeneity. Spatial turnover contributes significantly more to beta diversity in southern regions characterized by stable historic climates than it does in northern Europe. These findings support the historic climate hypothesis which suggests that patterns of increasing range size and decreasing species turnover at higher latitudes in the Palaearctic region are primarily driven by long-term temperature oscillations. The study present one of the basic research fields in the scope of the research programme, in which we study patterns of species distributions and the drivers that form and sustain them. Moreover, the study illustrates the importance of the study systems we rely on, as well as our data-management capabilities.
COBISS.SI-ID: 3154767
We generated the first genomic map for quantitative trait loci in Asellus and showed how loci for eye and pigment loss are distributed. We found that two tightly linked pairs of loci are responsible for both types of losses and that several different loss-mutations are superimposed on each other. A similar genomic architecture for two different double mechanisms of loss indicates that we might be dealing with a mechanism favored by naturel selection, like pleiotropy. The article tackles one of the central topics of the proposed program. The research was conducted on Dinaric species that is a candidate for model organism. It is an important starting point for our further studies on evolution in caves.
COBISS.SI-ID: 2373199
Current theory predicts that a shift to a new habitat would increase the rate of diversification, while as lineages evolve into multiple species, intensified competition would decrease the rate of diversification. We used Holarctic amphipods of the genus Gammarus to test this hypothesis. We sequenced four genes (5,088 bp) for 289 samples representing 115 Gammarus species. A phylogenetic analysis showed that Gammarus originated from the Tethyan region with a saline ancestry in the Paleocene, and later colonized the freshwater habitat in the Middle Eocene. Ancestral range reconstruction and diversification mode analysis combined with paleogeological and paleoclimatic evidence suggested that the habitat shift from saline to freshwater led to an increased diversification rate. The saline lineage of Gammarus dispersed to both sides of the Atlantic at 55 million years ago (Ma), because of the few barriers between the Tethys and the Atlantic, and diversified throughout its evolutionary history with a constant diversification rate [0.04 species per million years (sp/My)]. The freshwater Gammarus, however, underwent a rapid diversification phase (0.11 sp/My) until the Middle Miocene, and lineages successively diversified across Eurasia via vicariance process likely driven by changes of the Tethys and landmass. In particular, the freshwater Gammarus lacustris and Gammarus balcanicus lineages had a relatively high diversification shift, corresponding to the regression of the Paratethys Sea and the continentalization of Eurasian lands during the Miocene period. Subsequently (14 Ma), the diversification rate of the freshwater Gammarus decreased to 0.05 and again to 0.01 sp/My. The genus Gammarus provides an excellent aquatic case supporting. The study analyzed a process of diversification using taxon that is central to the program. The article uses similar methodology as we use now. Understanding of historical evolutionary processes is important for interpretation of recent distribution patterns and nature conservation.
COBISS.SI-ID: 2424399
We articulated a problem that essentially impedes development of web databases. While relational databases depend on unambiguous identifiers, the nature of taxonomy permanently modifies the central identifier, i.e. species name. As the taxonomy develops, the work for database curation increases exponentially. We propose that the problem might be diminished if databasing would be included into taxonomic process. Both, databasing and taxonomy are important parts of the program. The article builds on our own experience from database curation and taxonomic expertise. It is an opinion and a suggestion for smoother curation of international database curation.
COBISS.SI-ID: 4937807
This study is the first to report the effects of cerium (IV) oxide nanoparticles (nCeO2) on honeybees. These nanomaterials are added as fuel catalysts and therefore a great probability of their atmospheric deposition on plants exists. We showed that ingestion of food that contains nCeO2 is not lethal to honeybees, but it induces a number of sublethal alterations observed at the biochemical level. The most prominent was the induction of detoxification processes and the effect on the enzyme involved in cholinergic transmission of nerve signal. The latter plays a role in honeybee learning and orientation. Work is directly connected to the content of this program proposal. It is addressing the a question relevant for the program, and uses to complementary methodology. As the first study on that topic, it prompted related research on this issue.
COBISS.SI-ID: 4482127
Although it is common knowledge in 2019 that nanomaterials release toxic metal ions, this was not considered so even 5 years ago. This study was one of the first showing that nanomaterials can transform inside the organism and release metal ions. The release of toxic metals from nanomaterials inside the gut significantly contributes to their assimilation and increases their toxic potential. A combination of techniques to analyze the dissolution in various aquatic media was used in this multi-laboratory study. Part of this study was also aimed to develop an efficient metal assimilation test system with terrestrial isopods (Porcelio scaber) which has been used regularly ever since. We consider this paper as very important in terms of laying down basic concepts for further research in this field. Knowledge regarding nanomaterial transformation is important to plan future research on the fate of aged nanomaterials in the complex environmental samples, such as wastewater sludge. Also the same established test model, Porcellio scaber, will be employed in the program.
COBISS.SI-ID: 2658127
The ongoing refugee crisis in Europe has seen many countries rush to construct border security fencing to divert or control the flow of people. This follows a trend of border fence construction across Eurasia during the post-9/11 era. This development has gone largely unnoticed by conservation biologists during an era in which, ironically, transboundary cooperation has emerged as a conservation paradigm. These fences represent a major threat to wildlife because they can cause mortality, obstruct access to seasonally important resources, and reduce effective population size. We summarise the extent of the issue and propose concrete mitigation measures. The article addresses protection of large mammals, which is one of the main topics of the program. It demonstrates how nature conservation depends on a broader social context, with constructive suggestions for mitigation.
COBISS.SI-ID: 3923279
The conservation of large carnivores is a formidable challenge for biodiversity conservation. Using a data set on the past and current status of brown bears (Ursus arctos), Eurasian lynx (Lynx lynx), gray wolves (Canis lupus), and wolverines (Gulo gulo) in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible. The European situation reveals that large carnivores and people can share the same landscape. The article deals with a topic central to the program. It is an outcome of transboundary collaboration and demonstrates that our local conservation activities are visible in Europe and represent an active part of European nature conservation. An overall positive message is a signal to decision makers to continue with efforts for protection of these species.
COBISS.SI-ID: 3996838