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Abstracts
of Recent Publications |
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001-
Etienne Yergeau, Mélanie Arbour, Roland
Brousseau, David Juck, John R. Lawrence, Luke Masson,
Lyle G. Whyte, and Charles W. Greer. Biotechnology
Research Institute, National Research Council of Canada,
Montréal, QC, Canada. Microarray and Real-Time PCR
analyses of the responses of high-Arctic soil bacteria to
hydrocarbon pollution and bioremediation treatments. Applied and Environmental Microbiology, Vol. 75(19)
2009, 6258-6267.
High-Arctic soils have low nutrient availability,
low moisture content, and very low temperatures and, as
such, they pose a particular problem in terms of
hydrocarbon bioremediation. An in-depth knowledge of the
microbiology involved in this process is likely to be crucial
to understand and optimize the factors most influencing
bioremediation. Here, we compared two distinct large-scale
field bioremediation experiments, located at the Canadian high-Arctic stations of Alert (ex situ approach) and Eureka
(in situ approach). Bacterial community structure and
function were assessed using microarrays targeting the 16S
rRNA genes of bacteria found in cold environments and
hydrocarbon degradation genes as well as quantitative
reverse transcriptase PCR targeting key functional genes.
The results indicated a large difference between sampling
sites in terms of both soil microbiology and
decontamination rates. A rapid reorganization of the
bacterial community structure and functional potential as
well as rapid increases in the expression of alkane
monooxygenases and polyaromatic hydrocarbon-ringhydroxylating
dioxygenases were observed 1 month after
the bioremediation treatment commenced in the Alert soils.
In contrast, no clear changes in community structure were
observed in Eureka soils, while key gene expression
increased after a relatively long lag period (1 year). Such
discrepancies are likely caused by differences in
bioremediation treatments (i.e., ex situ versus in situ),
weathering of the hydrocarbons, indigenous microbial communities, and environmental factors such as soil humidity
and temperature. In addition, this study demonstrates the value of
molecular tools for the monitoring of polar bacteria and their
associated functions during bioremediation.
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002-L Wang, B Liu, and Z Zhou. TEDA School of
Biological Sciences and Biotechnology, Nankai University,
Tianjin, 300457, China. wanglei@nankai.edu.cn. Research
progress in genomics of environmental and industrial
microorganisms. Science in China Series C – Life Science,
Microbes contribute to geochemical cycles in the
ecosystem. They also play important roles in biodegradation and
bioremediation of contaminated environments, and have great
potential in energy conversion and regeneration. Up to date, at
least 150 genomes of non-pathogenic microbes have been
sequenced, of which, the majority are bacteria from various
environments or of industrial uses. The emerging field
'metagenomics' in combination with the high-throughput
sequencing technology offers opportunities to discover new
functions of microbes in the environment on a large scale, and
has become the 'hot spot' in the field of environmental
microbiology. Seven genomes of bacteria from various extreme environments, including high temperature, high and low pressure,
and extreme acidic regions, have been sequenced by researchers
in China, leading to the discovery of metabolic pathways, genetic
functions and new enzymes, which are related to the niches those
bacteria occupy. These results were published in Nature, PNAS,
Genome Research and other top international journals. In the
meantime, several groups in China have started metagenomics'
programs. The outcomes of these researches are expected to
generate a considerable number of novel findings, taking Chinese
researchers to the frontier of genomics for environmental and
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003-
H. A. L. Rowland, C. Boothman, R. Pancost, A. G.
Gault, D. A. Polya and J. R. Lloyd. School of Earth, Atmospheric
and Environmental Sciences and Williamson Research Centre for
Molecular Environmental Science, The Univ. of Manchester,
M13 9PL, UK. jon.lloyd@manchester.ac.uk. The role of
indigenous microorganisms in the biodegradation of naturally
occurring petroleum, the reduction of iron, and the
mobilization of arsenite from West bengal aquifer sediments. Journal of Environmental Quality, 38, 2009, 1598-1607.
High levels of naturally occurring arsenic are
found in the shallow reducing aquifers of West Bengal,
Bangladesh, and other areas of Southeast Asia. These
aquifers are used extensively for drinking water and
irrigation by the local population. Mechanisms for its
release are unclear, although increasing evidence points to
a microbial control. The type of organic matter present is of
vital importance because it has a direct impact on the rate
of microbial activity and on the amount of arsenic released
into the ground water. The discovery of naturally occurring
hydrocarbons in an arsenic-rich aquifer from West Bengal
provides a source of potential electron donors for this
process. Using microcosm-based techniques, seven
sediments from a site containing naturally occurring
hydrocarbons in West Bengal were incubated with
synthetic ground water for 28 d under anaerobic conditions
without the addition of an external electron donor. Arsenic
release and Fe(III) reduction appeared to be microbially
mediated, with variable rates of arsenic mobilization in
comparison to Fe(III) reduction, suggesting that multiple
processes are involved.All sediments showed a preferential
loss of petroleum-sourced n-alkanes over terrestrially sourced sedimentary hydrocarbons n-alkanes during the
incubation, implying that the use of petroleum-sourced nalkanes
could support, directly or indirectly the microbial
Fe(III) reduction. Samples undergoing maximal release of
As(III) contained a significant population of
Sulfurospirillum sp. a known As(V)-reducing bacterium,
providing the first evidence that such organisms may
mediate arsenic release from West Bengal aquifers.
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004-DS Fraser, K O'Halloran, and MR van den
Heuvel. University of Waikato, Private Bag 3105,
Hamilton, New Zealand. Toxicity of pulp and paper solid
organic waste constituents to soil organisms. Chemosphere, 74(5), 2009, 660-8.
This study examined the potential biological
hazard of pulp and paper waste solids. The solids examined
were chosen on the basis of the range of wood-related
organic extractives and were either primary solids screened
from the effluent stream before secondary treatment, or
biosolids from aerated stabilisation lagoons. Acute effects
were tested at the level of plants, invertebrates and soil microbes using an oat germination and growth test,
earthworm survival and reproduction test, an enchytraeid worm
survival and reproduction test, and standard measures of
microbial respiration. This was further benchmarked against a
marine bacteria toxicity test using extract of the waste solids.
Resin acids and resin acid neutrals made up the greatest
proportion of organic extractives measured in biosolids whereas
resin acids and fatty acids were the main constituents detected in
primary solids. Examination of the tissue of earthworms from the
tests revealed no net bioconcentration of the organic extractives.
The waste solids were not acutely toxic to any of the soil
organisms as tested without any dilution. Conversely, extracts of
the waste solids demonstrated toxicity in the marine bacteria. In
some cases, the solid waste material enhanced the growth of
plants, earthworm reproduction and microbial respiration. The
only adverse affect was that reproduction of enchytraeids was
reduced by some of the waste solid treatments. However these
effects did not appear to be associated with concentrations of
resin acid neutrals and resin acids in these materials. Overall pulp
and paper wastes were relatively benign in terms of toxicity to
the soil organisms tested.
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005-Peter S. Kourtev, Cindy H. Nakatsu, and Allan Konopka . Department of Biology, Central Michigan University,
228 Brooks Hall, Mt. Pleasant, MI 48858. Phone: (989) 774-
2388. Fax: (989) 774-3462. kourt1ps@cmich.edu. Inhibition of
nitrate reduction by chromium (VI) in anaerobic soil
microcosms. Applied and Environmental Microbiology,
Vol.75(19), 2009, 6249-6257.
Chromium is often found as a contaminant at sites
polluted with organic compounds. For nitrate-respiring microbes,
Cr(VI) may be not only directly toxic but may also specifically
interfere with N reduction. In soil microcosms amended with
organic electron donors, Cr(VI), and nitrate, bacteria oxidized
added carbon, but relatively low doses of Cr(VI) caused a lag and
then lower rates of CO2 accumulation. Cr(VI) strongly inhibited
nitrate reduction; it occurred only after soluble Cr(VI) could not
be detected. However, Cr(VI) additions did not eliminate Crsensitive
populations; after a second dose of Cr(VI), bacterial
activity was strongly inhibited. Differences in microbial
community composition (assayed by PCR-denaturing gradient gel
electrophoresis) driven by different organic substrates (glucose
and protein) were smaller than when other electron acceptors had
been used. However, the selection of bacterial phylotypes was modified by Cr(VI). Nine isolated clades of
facultatively anaerobic Cr(VI)-resistant bacteria were
closely related to cultivated members of the phylum
Actinobacteria or Firmicutes. In Bacillus cereus GNCR-4,
the nature of the electron donor (fermentable or
nonfermentable) affected Cr(VI) resistance level and
anaerobic nitrate metabolism. Our results indicate that
carbon utilization and nitrate reduction in these soils were
contingent upon the reduction of added Cr(VI). The amount
of Cr(VI) required to inhibit nitrate reduction was 10-fold
less than for aerobic catabolism of the same organic substrate. We
speculate that the resistance level of a microbial process is directly
related to the diversity of microbes capable of conducting it.
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006-Takuji Ishikawa. Department of Bioengineering
and Robotics, Tohoku University, 6-6-01, Aoba, Aramaki, Aobaku,
Sendai 980-8579, Japan. Suspension biomechanics of
swimming microbes. Journal of the Royal Society Interface (rsif)
2009.
Microorganisms play a vital role in many biological,
medical and engineering phenomena. Some recent research efforts
have demonstrated the importance of biomechanics in
understanding certain aspects of microorganism behavior such as
locomotion and collective motion of cells. In particular, spatio spatiotemporal
coherent structures found in a bacterial suspension have
been the focus of many research studies over the last few years.
Recent studies have shown that macroscopic properties of a
suspension, such as rheology and diffusion, are strongly affected
by meso-scale flow structures generated by swimming microbes.
Since the meso-scale flow structures are strongly affected by the
interactions between microbes, a bottom - up strategy, i.e. from a
cellular level to a continuum suspension level, represents the
natural approach to the study of a suspension of swimming
microbes. In this paper, we first provide a summary of existing
biomechanical research on interactions between a pair of
swimming microorganisms, as a two-body interaction is the
simplest many-body interaction. We show that interactions
between two nearby swimming microorganisms are described
well by existing mathematical models. Then, collective motions
formed by a group of swimming microorganisms are discussed.
We show that some collective motions of microorganisms, such
as coherent structures of bacterial suspensions, are satisfactorily
explained by fluid dynamics. Lastly, we discuss how macroscopic
suspension properties are changed by the microscopic
characteristics of the cell suspension. The fundamental knowledge
we present will be useful in obtaining a better understanding of
the behavior of microorganisms.
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| ENVIS
CENTRE Newsletter Vol.7, No 4 October 2009 |
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