[L&O Featured Article]L&O Vol. 46, No. 3 (May 2001): Featured Article now available

[lo-feature-admin@aslo.org]

The featured article in the May 2001 issue of L&O is:

Urbach, Ena, Kevin L. Vergin, Lei Young, Ariel Morse, Gary L. Larson, and 
Stephen J. Giovannoni. 2001. Unusual bacterioplankton community structure 
in ultra-oligotrophic Crater Lake. Limnol. Oceanogr. 46: 557-572.

This article is freely available on the Web at

          http://aslo.org/lo/toc/vol_46/issue_3/0557.pdf

Instructions for reading PDF files are located on the ASLO web page:

          http://aslo.org/help/loonline.html

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Introductory comments by Jon Zehr (the L&O Associate Editor who handled 
this paper):

Historically, one of the major differences between the study of macro- and 
micro-organisms in aquatic systems was the inability to visualize and 
analyze microbial communities qualitatively. For decades, microbial ecology 
was limited to quantifying their metabolic processes or studying isolates. 
The introduction of molecular biological techniques into microbial ecology 
studies fractured this "black box" constraint. Information on genetic 
sequences, as well as a suite of other molecular and immunological 
techniques, now make it possible to obtain qualitative information for 
microbes that is equivalent to the taxonomic information that is relatively 
easily gleaned for macro-organisms. That is, we can now unambiguously 
identify micro-organisms that had previously been unidentifiable 
microscopic blobs. Early rewards of this approach were the recognition that 
the organisms in natural assemblages were not closely related to previously 
cultivated microorganisms (Giovannoni et al. 1990). Soon thereafter, it was 
recognized that open ocean habitats contain specific clades, including 
previously undescribed groups in the Archaea (DeLong et al.1992, Fuhrman et 
al. 1992). This discovery took a new twist when the first freshwater 
studies were overlain upon the oceanic databases (Bahr et al. 1996, Hiorns 
et al. 1997, Methe et al. 1998, Zwart et al. 1998). Freshwater 
microorganisms were found to be amazingly similar to each other in habitats 
ranging from Antarctica to Lake Baikal (Semenova and Kuznedelov 1998, 
Priscu et al.1999). Some freshwater groups mimicked, but were distinct 
from, open ocean assemblages. In particular, the b proteobacteria, a group 
relatively closely related to the g proteobacteria but without any obvious 
unifying physiological characteristics, were ubiquitous in freshwater. b 
proteobacteria do not occur in oceanic habitats (they have been found in 
coastal waters, however).

Exceptions to patterns provide clues to underlying controlling mechanisms. 
In this month's Featured L&O article, Urbach et al. (2001) describe the 
microbial flora of ultra-oligotrophic Crater Lake, California, which is 
located in a volcanic crater in the Cascade Mountain range. This lake's 
microbial flora proved to be quite different from that seen in other lakes. 
Specifically, in Crater Lake the b proteobacteria were much rarer than in 
other lakes, and the microbial assemblages were dominated by a new group of 
Verrucomicrobiales and actinomycetes that had previously been found in 
Adirondack Lakes (Hiorns et al. 1997). Group I Crenarchaeota and green 
nonsulfur bacteria, previously reported in oceanic environments, were also 
found. This unusual result suggests that microbial community composition 
may be controlled by factors that are unusual in this lake, such as high UV 
(Crater Lake has unusually clear waters, with Secchi disk depths reported 
in excess of 40 meters), or perhaps trace metal or dissolved organic matter 
concentrations and composition.

This new information on microbial assemblages provides a framework for 
comparing rates of processes in different environments, and relationships 
between habitat and microbial community structure. As we move into the era 
of post-genomics for the human genome, we approach the crest of the wave of 
microbial genomics, which has already begun to link the functions of 
uncultivated microbes to their phylogenetic identities (Beja et al. 2000). 
With these new tools, limnologists and oceanographers can begin to ask 
ecological questions about microbes and biogeochemical cycles that are 
firmly based on the identities and characteristics of the organisms 
involved, in the same way that macroecologists have for centuries.

References

Bahr, M., J. E. Hobbie, and M. L. Sogin. 1996. Bacterial diversity in an 
arctic lake: a freshwater SAR 11 cluster. Aquat. Micr. Ecol. 11: 271-277.

Beja, O., L. Aravind, E. V. Koonin, M. T. Suzuki, A. Hadd, L. P. Nguyen, S. 
Jovanovich, C. M. Gates, R. A. Feldman, J. L. Spudich, E. N. Spudich, and 
E. F. DeLong. 2000. Bacterial rhodopsin: Evidence for a new type of 
phototrophy in the sea. Science 289: 1902-1906.

DeLong, E. F. 1992. Archaea in coastal marine environments. Proceedings of 
the National Academy of Sciences USA 89: 5685-5689.

Fuhrman, J. A., K. McCallum, and A. A. Davis. 1992. Novel major 
archaebacterial group from marine plankton. Nature 356: 148-149.

Giovannoni, S. J., T. B. Britschgi, C. L. Moyer, and K. G. Field. 1990. 
Genetic diversity in Sargasso Sea bacterioplankton. Nature 344: 60-63.

Hiorns, W. D., B. A. Methé, S. A. Nierzwicki-Bauer, and J. P. Zehr. 
1997. Bacterial diversity in Adirondack mountain lakes as revealed by 16S 
rRNA gene sequences. Appl. Environ. Microbiol. 63: 2957-2960.

Methe, B. A., W. D. Hiorns, and J. P. Zehr. 1998. Contrasts between marine 
and freshwater bacterial community composition: analyses of communities in 
Lake George, NY and six other Adirondack lakes. Limnol. Oceanogr. 43: 368-374.

Priscu, J. C., E. E. Adams, W. B. Lyons, M. A. Voytek, D. W. Mogk, R. L. 
Brown, C. P. McKay, C. D. Takacs, K. A. Welch, C. F. Wolf, J. D. Kirshtein, 
and R. Avci. 1999. Geomicrobiology of subglacial ice above Lake Vostok, 
Antarctica. Science 286: 2141-2144.

Semenova, E. A., and K. D. Kuznedelov. 1998. A study of the biodiversity of 
Baikal picoplankton by comparative analysis of 16S rRNA gene 5'-terminal 
regions. Mol. Biol. 32: 754-760.

Urbach, E., K. L. Vergin, L. Young, A. Morse, G. L. Larson, and S. J. 
Giovannoni. 2001. Unusual bacterioplankton community structure in 
ultra-oligotrophic Crater Lake. Limnol. Oceanogr. 46: 557-572.

Zwart, G., W. D. Hiorns, B. A. Methe, M. P. Agterveld, R. Huismans, S. C. 
Nold, J. P. Zehr, and H. J. Laanbroek. 1998. Near-identical 16S rRNA 
sequences recovered from lakes in North America and Europe indicate the 
existence of clades of freshwater bacteria with global distribution. 
Systematic and Applied Microbiology 21: 546-556.