Fungi are used as model organisms in laboratory studies

Much of what we know about many basic aspects of cell and molecular biology comes from the study of model organisms. Among the eukaryotes, some fungi have numerous advantages over model plant and animal systems for laboratory investigations.

Of particular importance as model organisms are several species of sac fungi: Aspergillus nidulans (a brown mold), Neurospora crassa (a red bread mold), Saccharomyces cerevisiae (baker’s, or brewer’s, yeast), and Schizosaccharomyces pombe (fission yeast). These species can be cultured in large numbers in small spaces, and they have short generation times, so that genetic investigations can be conducted in days rather than years. Furthermore, their genomes are relatively small and encode relatively few genes compared with those of most plants and animals, so it is easier to elucidate the functions of the fungal genes responsible for basic biological functions.

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investigating life

Using Fungi to Study Environmental Contamination

experiment

Original Paper: Flegal, A. R., C. Gallon, S. Hibdon, Z. E. Kuspa and L. F. Laporte. 2010. Declining—but persistent—atmospheric contamination in central California from the resuspension of historic leaded gasoline emissions as recorded in the lace lichen (Ramalina menziesii Taylor) from 1892 to 2006. Environmental Science and Technology 44: 5613–5618.

A. Russell Flegal and his colleagues analyzed museum samples of lace lichens (Ramalina menziesii) collected between 1892 and 2006 near San Francisco, California. Their goals were to determine the sources of lead contamination and to evaluate the effectiveness of efforts to reduce this contamination.

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work with the data

From the data below, plot lead concentration in the lichen samples against year of sample collection. Make a second plot, this one of 206Pb/207Pb ratio against year of sample collection.

Sample Year
collected		 Lead concentration
(µg of Pb/g lichen)		 206Pb/207Pb ratio
1 1892 11.9 1.165
2 1894 4.0 1.155
3 1906 13.7 1.154
4 1907 22.9 1.157
5 1945 49.9 1.187
6 1957 34.2 1.185
7 1978 50.9 1.221
8 1982 10.0 1.215
9 1983 4.6 1.224
10 1987 1.0 1.198
11 1988 1.3 1.199
12 1995 1.9 1.202
13 2000 0.4 1.184
14 2006 1.8 1.184

QUESTIONS

Question 1

Calculate trend lines for your plots by plotting the average for the each adjacent pair of observations, from 1894 to 2006. (In other words, plot the average for sample 1 and 2, then the average for sample 2 and 3, and so on, to produce a trend line for the data.)


Question 2

Do your analyses support the conclusions of the study? How do you think you could improve the analysis?

Yes, the levels of environmental lead contamination and the ratios of lead isotopes are consistent with the identified sources. The closure of the lead smelter was offset by the use of leaded gasoline, but there was a marked drop-off of environmental lead contamination after the elimination of both of these sources. The trend lines show a peak in environmental lead contamination around the 1960s to 1980s, and then a rapid drop after the end of leaded gasoline use in the early 1980s. The measured ratios of 206Pb/207Pb are consistent with the suspected sources of lead contamination through time. One way to extend the analysis would be to analyze additional lichen samples collected during the relatively poorly sampled period between 1907 and 1978 (from which period only two samples are included). Note, however, that such an analysis would depend on the existence of appropriate samples, such as museum collections made during this time.

A similar work with the data exercise may be assigned in LaunchPad.