Rapidgene-sequencing methods have made possible the new field of metagenetics, wherebulk DNA is extracted from the environment and analysed for the diversityof life forms within it. Everywhere one looks, many thousands of previouslyunknown species of bacteria, archaea and fungi are found. Our past work hasmostly concentrated on prokaryotes. Work so far has concentrated in Asia,including Korea, Japan, Malaysia, China and Mongolia. See our publications pageon this website for more details.
Recent findings byour group include:
l The leaves of each species of tropical tree has its owndistinctive community of thousands of species of bacteria, adapted to thephysical and chemical conditions of the leaf surface. It is not yet known ifthese are mutualists, commensals or parasites of the host tree. Tree speciesmore closely related by evolution tend to have more similar communities of leafbacteria.
l In the tropics, maximum diversity of soil bacteria isreached around neutral pH, with a decline in diversity towards more acidic andmore alkaline soils. Individual phyla of bacteria also peak in diversity aroundneutral pH, even those groups (e.g. acidobacteria) that are most abundantnumerically in acidic soils. This work was carried out in Malaysia.
l On Mount Fuji, Japan, the diversity of both soil bacteriaand soil archaea shows a mid-elevation maximum. Explanations may include theintermediate levels of soil disturbance affecting the mid elevations of themountain, promoting coexistence of many microbial species.
l The root surfaces of tropical trees in Malaysia have adistinctive community of bacteria, unique to each tree species, that differsfrom the surrounding forest soil. Distinctive components of the communityinclude host-specific clusters of the nitrogen-fixing genus Burkholderia, pointing a novelmutualistic nitrogen source for tropical trees.
l The soil bacterial communities from summit to base ofMount Halla, on Jeju Island of Korea, are distinctive by the lava substratetype that they originally formed over – rather than being controlled by climateand vegetation type. This suggests that the soil bacterial community isdominated by distinctive aspects of soil mineralogy and chemistry.
l Laboratory-based soil disturbance experiments show thatdisturbance to a soil decreases overall species diversity of the soilcommunity. Nevertheless, at each disturbance level, certain predictable soilcommunities form, dominated by certain species and phyla. At the highestlevels of disturbance, community composition becomes much less predictable – suggestinga role of ‘lottery’ colonization and competition from small founderpopulations.
l A study of soil bacterial communities in semi-aridMongolia revealed the existence of several completely new phyla of bacteria.The study also revealed that salinity and soil texture, rather than pH orvegetation cover, determine differences in bacterial community composition inthis environment.