ACTA CARSOLOGICA 37/2-3 – 2008 349
REVIEWS AND REPORTS / POROč ILA
ISSM 2008
7
th
 International Symposium for Subsurface Microbiology
November 16-21, 2008, Shizuoka, Japan
From the first naive recognition in the early 1980’s 
of microbial life in the subsurface, subsurface microbiol-
ogy in recent years is no longer important only in aca-
demic debates, but is becoming more relevant to societal 
issues, such as the construction of safe nuclear waste 
sites. 
The 7
th
 International Symposium for Subsurface 
Microbiology (ISSM) in Shizuoka, Japan, offered eleven 
lecture and three poster sessions for 230 participants 
from 22 countries. Topics presented spanned the range 
of microbial interactions in subsurface habitats (deep 
igneous aquifers, mines, caves, submarine hydrothermal 
vent systems, soils, and water bodies), the evolution of 
geochemical and microbiological systems through time, 
life in extreme environments, the application of metage-
nomics, and issues and technologies concerning biore-
mediation and even the safety of “microbially resistant” 
radioactive waste disposal sites.
Several recurring themes focused on trying to an-
swer key questions, including where does the biosphere 
end and the geosphere start, and how can we apply our 
technological advances from the shallow subsurface set-
tings, like soils and caves, to explore the deeper, hotter 
biosphere, including from submarine settings? 
The emergence of life on Earth and other planetary 
bodies is a topic that attracts broader audiences, and the 
participants also explored and debated various evolution-
ary possibilities. For instance, the minimum temperature 
for modern metabolic processes is about -20°C. But, if 
we take into account that the average temperature in 
the universe is -270.5 °C, is it possible that life can exist 
at lower temperatures or that life evolved at lower tem-
peratures? Life survival strategies were also discussed, 
including how microbes deal with environmental stress 
like high oxygen concentrations and desiccation. 
One common topic for discussion was that there 
are many emerging, new techniques to study the inter-
actions between subsurface microbes and their environ-
ments, including technologies that enable the identifica-
tion of biosignature molecules and new genes that can 
confer metabolic capacity under various conditions and 
even stress responses. These discoveries lead to the de-
scription of new organisms, but also an understanding of 
evolution due to the frequency of horizontal gene trans-
fer from one microbial species to another. 
In the past, microbiology was not significantly 
justified in the context of environmental intervention. 
However, nowadays as many places are becoming in-
creasingly contaminated with heavy metals, chlorinated 
compounds, and other pollutants, there is a need to 
understand successful bioremediation processes, and 
cometabolic and intermicrobial reactions. For example, 
research that was presented on this topic described how 
microbes can immobilize uranium compounds or accu-
mulate toxic arsenic molecules, and how cyanobacteria 
can remediate polluted areas. 
The interest in subsurface microbiology to waste 
disposal has resulted in a number of studies that have 
been conducted by research groups from multiple coun-
tries. Their results reveal relatively high numbers of mi-
crobial taxa from various rocks that are capable of living 
in biofilms that depend on a flux of energetically favour-
able compounds in water, and sometimes even from sur-
face-derived organic matter. As a consequence of their 
metabolism, the indigenous microbiota can corrode 
concrete or metal shields around nuclear wastes. 
The participants in the symposium did not avoid 
very urgent issues, such as climate change. Although re-
sponses to climate change can be observed in higher ani-
mals and plants, recent research indicates that microbial 
communities are also affected. For instance, experiments 
show that microbes metabolize more polymers preferen-
tially at lower temperature, but they use more carboxylic 
acids at higher temperatures. Other issues, such as how 
to deal with greenhouse gases, were also presented, in-
cluding the introduction of CO
2
 into the underground.
Because caves in karst are natural windows to the 
underground, the topic of caves was brought up on sev-
eral occasions by speakers, in posters, and from plenary 
lectures. More microbiologists who study caves and karst 
were encouraged to participate in future symposia.
The next ISSM conference will be held in Munich, 
Germany, in 2011.
Janez mulec