Studies of the subsurface microbiology of the Äspö Hard Rock Laboratory, Sweden have revealed the presence of many different bacteria in the deep groundwaters which appear to maintain reducing conditions. Experiments were conducted to study the rock-water and microbial interactions. These used crushed Äspö diorite, Äspö groundwater and iron- and sulphate-reducing bacteria in flowing systems under anaerobic conditions. In column experiments, there was evidence of loss and mobilization of fine-grained crushed material (<5 μm) which had originally adhered to grain surfaces in the starting material. The mobilized fines were trapped between grains. The degree of mineralogical alteration was greater in the experiments when bacteria were present. In both column and continuously stirred reactor experiments, there is evidence for the formation of a secondary clay. These experiments have shown that microbial activity can influence rock-water interactions even in nutrient-poor conditions.

Understanding the biogeochemical behaviour of actinides in the environment is essential for the longterm stewardship of radionuclide contaminated land. Plutonium is of particular concern due its high radiotoxicity, long half-life and complex chemistry, with these factors contributing to the limited literature available on its environmental behaviour. Here, we investigate the biogeochemistry of Pu in contaminated soil as microbial processes have the potential to mobilize Pu through numerous mechanisms including the reduction of Pu(IV) to the potentially more mobile Pu(III). After the addition of glucose to stimulate microbial activities, there was a substantial shift in the 16S rRNA gene profile of the extant microbial communities between days 0 and 44 with an increase in Clostridium species, known glucose fermenters which have been reported to facilitate the reduction of Pu(IV) to Pu(III). A minor increase in Pu mobility was observed at day 44, returning to initial levels by day 118. The negligible change in Pu mobility, despite the onset of reducing conditions and changing mineralogy, would suggest the Pu is highly refractory. This information is important for developing remediation options for Pu-contaminated soils, suggesting that managing legacy Pu in situ may be preferred to mobilization via the stimulation of metal-reducing bacteria.

By interactions with other microbes, free-living amoebae play a significant role in microbiology, environmental biology, physiology, cellular interactions, ecology and evolution. Here, we discuss astonishing interactions of bacteria and amoebae, in the light of evolution and functional aspects impacting human health. In favourable environmental conditions, the interaction of Acanthamoeba with non-virulent bacteria results in lysis of the bacteria. However, the interaction with weak-virulent bacteria results in a symbiotic relationship or amoebal lysis may occur. The microbial survival of amoebae in harsh environments, ability to interact with bacteria, and their ability to aid transmission to susceptible hosts is of great concern to human, animal and ecosystem health.

The effects of mycorrhizal fungi have traditionally been considered within the rather narrow perspective of their effects on the mineral nutrition of individual plants. Most biologists are familiar with the idea that these symbiotic fungi may improve plant uptake of dissolved mineral nutrients. What other effects do these symbionts have? Research during the past 20 years has increasingly viewed symbiotic mycorrhizal associations between plants and fungi within a wider, multifunctional perspective. New molecular methods have been applied to investigate mycorrhizal fungal communities (Bruns & Bidartondo, 2002) and greater attention has been paid to their possible effects at the level of the plant community. As we have acquired greater knowledge about fungal species diversity, so we have become more aware of the potential functional diversity of mycorrhizal fungi. The new multifunctional perspective includes mobilisation of N and P from organic polymers, possible release of nutrients from mineral particles or rock surfaces via weathering, effects on carbon cycling, interactions with myco-heterotrophic plants, mediation of plant responses to stress factors such as drought, soil acidification, toxic metals and plant pathogens, as well as a range of possible interactions with groups of other soil microorganisms.

The exquisite preservation of organisms in the Early Devonian Rhynie chert ecosystem has permitted the documentation of the morphology and life history biology of fungi belonging to several major taxonomic groups (e.g., Chytridiomycota, Ascomycota, Glomeromycota). The Rhynie chert also provides the first unequivocal evidence in the fossil record of fungal interactions that can in turn be compared with those in modern ecosystems. These interactions in the Rhynie chert involve both green algae and macroplants, with examples of saprophytism, parasitism, and mutualism, including the earliest mycorrhizal associations and lichen symbiosis known to date in the fossil record. Especially significant are several types of specific host responses to fungal infection that indicate that these plants had already evolved methods of defence similar and perhaps analogous to those of extant plants. This suggests that mechanisms underlying the establishment and sustenance of associations of fungi with land plants were well in place prior to the Early Devonian. In addition, a more complete understanding of the microbial organisms involved in this complex ecosystem can also provide calibration points for phylogenies based on molecular data analysis. The richness of the microbial community in the Rhynie chert holds tremendous potential for documenting additional fungal groups, which permits speculation about further interactions with abiotic and biotic components of the environment.