Specialized Laboratories
Microfossil Separation Lab
The microfossil separation lab was set up, and is operated, by
Dr. Reed Scherer
to support his research involving diatoms and the
ice sheets of Antarctica. Diatoms are single-celled plants which
inhabit both fresh and salt water. They secrete a frustule
of silica the shape of which is diagnostic of the species, so
they can be identified in the fossil record. ( A frustule
can be thought of as being like the shell secreted by larger
life forms, e.g. sea shells. ) Because diatom populations
are very sensitive to climate and other environmental factors,
they can be used to investigate conditions that may have existed
in the area of interest at some time in the past. Dr. Scherer
is interested in the extent of ice sheet coverage as it has changed
with time. If diatoms are found in sediments beneath grounded
ice sheets ( ice sheets which are sufficiently thick that
they rest on the bottom of the sea ) then this suggests
the ice was absent from that area, or was at least sufficiently
thinner that it was floating, at some time in the past.
The age of the event can be estimated from a knowledge of the species
of diatoms present and of their evolutionary history, which has
been previously established.
Diatoms are very tiny objects, ranging in size between 6 and 200 micrometers in long dimension. Because of that they are very easily moved about with air currents or on clothing, or can be tracked about on shoes, and the lab is therefore designed as a "clean" lab. This means that a lab coat is worn over street clothing, there are special disposable blue "booties" worn over street shoes, and that special practices are observed in the lab to prevent contamination of samples. Air in the lab is continuously filtered, and a positive pressure is maintained so that all leaks are from within the lab to the outside world, never the reverse. In the first photograph, Ph.D. student Jochen Baier is in the clean lab, demonstrating equipment he uses to prepare permanent microscope slides from sediment cores for his research.
As stated above, diatoms are very tiny objects. There are therefore special problems which attend separating them not only from the sediment in which they are found, but from one another. The second photograph, taken during an open house to inaugurate the new lab, shows Ph.D. student Jessica Olney inspecting a micro sieve machine, which can help accomplish this. The device employs sieves, some of which may have openings on the order of 5 micrometers across, to separate microfossils according to size. ( Imagine a sieve with square, tapered, smoothed openings that are 5 micrometers on a side, all cut with exquisite precision! )
Another problem which can develop is that the host material, whether it be sediment or ice, can hold a great many or very few microfossils. Diatom-rich sediment may contain on the order of 500 million diatoms per gram, whereas ice or glacial sediments may have something like a few thousand per gram. How, then, does one concentrate the few diatoms in an ice core so that they can be collected and examined?
Jochen explains that the answer has to do
with these long plastic cones he's showing us. A section of ice
core is placed in the cone and allowed to melt. The liquid is
drawn off the bottom and passed
through a micropore filter to recover the fossils. The ancient
water is saved and sent to another lab for chemical analysis.
Diatoms in the ice show that these tiny fossils can be carried
by the wind for thousands of miles across the Antarctic wasteland.
The research carried out in the microfossil separation lab, and the associated ESEM, relate directly to the very important question of climate stability, colloquially referred to as "global warming." Are the ice sheets stable over time, or have they broken up before? If they have broken up in the past, what was the extent of the breakup, the time scale of it, and what were the causes? Evidence currently suggests, for instance, that there was at least one major disintegration of the West Antarctic Ice Sheet within the last 500,000 years -- long before man would have had a significant impact on the global ecosystem. These are the sorts of questions the microfossil separation lab is equipped to investigate.
Organic Geochemistry Lab
The nature and extent of human impact on the environment is an important field of enquiry. Current and past practices in agriculture, manufacturing, and other activities, have introduced substances into the environment which are actually or potentially harmful to life. Study of these materials as they exist in and interact with rock, soil, and biological agents is necessary in order to understand how best to prevent adverse effects, and to find remedies for problems that already exist. The organic geochemistry lab, operated by Dr. Melissa Lenczewski is used to identify and study the contaminants themselves, including such things as gasoline and its additives, organic solvents, and pesticides.
The principal piece of equipment used in this research is a Varian Saturn 2100 T GC/MS, pictured here with Ph.D. student Rosa Leal-Bautista loading the sample carousel. As implied in the name, it actually consists of two distinct instruments coupled together, a gas chromatograph ( the "GC" part ) and a mass spectrometer ( the "MS" part ). The gas chromatograph is used to separate organic molecules according to their mass, and the separated concentrations are then introduced into the mass spectrometer where they can be identified on the basis of their molecular weight. Once the molecular species present are known, a simple study might involve determination of the distribution of a particular contaminant or contaminants in groundwater as it flows away from the site of introduction carrying a so-called contaminant plume. A more complex effort would perhaps involve the difficult business of working out what reactions, if any, may be taking place in an environment, and how they are taking place. It is not uncommon for the products of chemical reactions to be more harmful than the original substances they are derived from, and this can complicate clean-up, or remediation, programs immensely.
A project currently in progress in the lab serves to illustrate the method. It involves a chemical called "methyl tert-butyl ether," or MTBE for short. It has been used as an additive for gasoline to make it burn more cleanly, and it is required by law to be used in some areas as a pollution-abatement measure. Unfortunately, it is both mildly toxic and now very widespread in the environment because of its use in motor fuels since the 1970s ( US EPA1 ). The effects of long-term human exposure are not known ( US EPA2 ).
A source of uncontaminated water is needed in an industrialized area of Mexico, where MTBE contamination is believed to be commonplace. It is possible that near-surface lacustrine clays may adsorb the MTBE and prevent it from reaching the deeper groundwater, or that any MTBE present may be biodegraded within the sedimentary column and destroyed, removing the threat. Samples of the clay sediment were taken from the area using core drills and returned to the lab for analysis. The organic fraction is to be extracted by warming the sample and collecting the vapors. These will be analyzed in the GC/MS to see where MTBE is located spatially ( the map locations of the drilling sites ) and in the sedimentary sequence ( how far down or exactly where in the core it is found ). It is hoped that the deeper groundwater reservoirs, protected by the clay layer, will prove to be MTBE-free.
Geomicrobiology Lab
The microbiology lab is closely associated with the organic geochemistry lab, and Dr. Lenczewski oversees both.
A very significant fraction of the living things on earth cannot be seen with the naked eye, and these micro-organisms are the objects of interest in this lab. Microbes can serve two very useful research purposes, as remediators and as indicators. As remediators, some have been found that can use a contaminant ( oil, for instance ) as food, and thereby destroy it. As indicators, they have much to say about the health of an ecosystem, or, viewed another way, how changing use patterns, pollution, or the like, may be affecting it. This can be of particular interest in cases where pesticides are involved, but it is also very useful to establish what "normal," or unstressed, ecosystems look like.
In conducting such research, the important
thing is to be able to identify the micro-organisms present,
and there are two possible ways of doing it. One is to make a
"culture" of them and identify them by
observing what sorts of things
they prefer for food, what sorts of things they excrete, and
what sort of living conditions ( e.g. temperature, light
or the absence of it, etc. ) encourage their growth. It
develops that only a small fraction of the microbes which may
be of interest in an ecosystem can be identified in this way,
however, and so it becomes necessary to identify them on the
basis of their DNA signatures. This is what the microbiology
lab is designed to do, isolate and replicate microbial DNA.
The picture shows a part of the lab, with undergraduate student Noe Velazquez using an automatic pipette to charge a sample block. The white objects in front of him and in the near background are part of the apparatus used to study microbial DNA. The lab is equipped to do two different procedures. One, ( pictured here ) reveals the presence or absence of a particular kind of DNA, hence the organism of which it is a part. The other ( not shown ) is used to discover how much of a kind of DNA is present in a sample, and therefore allows estimation of microbial populations. Further back, in front of the window, is a Fischer Hamilton SafeAire Class II biological safety cabinet. When working with microbes it is well to remember that not a few are dangerous to humans, and that therefore all precautions must be taken.
Electronics Shop
While not an analytical lab itself, the electronics shop run by Jianwen "Jay" Zhu is a most valuable resource available to those who use our labs and other analytical facilities. Jay, who is an electronics engineer, spends his time maintaining electronic instruments and fixing them when they break. He also designs and builds custom pieces of equipment when needed for specific projects.
Jay is no stranger to Northern Illinois University, having obtained his M.S. in electronics here, and we are very glad to have him with us.
This page was made by Neil Dickey. If you have questions or comments, feel free to e-mail me.
Last updated 12/02/05