A recently discovered unicellular chlorophytic alga

Info icon This preview shows pages 9–11. Sign up to view the full content.

, a recently discovered unicellular chlorophytic alga, with respect to geo- chemical gradients. The increase in chlorophyll fluorescence at the depth of 15–20m, where light intensity and oxygen concentration are relatively low, was attributed to Picocystis cells that have colonized this unique ecological zone. OGU11 8/14/04 11:52 AM Page 233
Image of page 9

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

234 PART II Principles and applications BOX 11.2 Mono Lake (a) in central California provides an excellent opportunity for microbiologists investigating the adaptation of microbial diversity to changing environmental conditions within a manageable geographical scale. The lake is a natural laboratory where the interactions between hydrological parameters and biogeochemical processes can be examined as a model system for understanding broad-ranging topics in microbial diversity and ecology. The salt concentration in the lake (84 to 94 grams per liter) makes it a hypersaline ecosystem. The lake is also home to alkalinophiles (pH 9.8); although it receives freshwater from the environment, it is not subject to the kinds of mixing reactions that characterize estuaries. Therefore, the lake exhibits strong gradients in physicochemical conditions according to depth (Humayoun et al ., 2003). Being anoxic at the bottom, reduced compounds such as sulfides accumulate to levels that may affect the biochemistry of metals ions, thereby exerting major influences on the structure of microbial communities along the lake’s depth. The photograph in (a) shows the lake’s characteristic mineral encrusted tufa towers. Photograph by courtesy of NASA (credit: Tony Phillips). 40 15 5 25 0 Depth (m) 0 20 35 30 10 Light ( m E/m 2 /s) 400 800 1200 0 4 8 12 2 6 10 Temperature or fluorescence Chemocline Oxycline Fluorescence Chlorophyll Temperature ( ° C) Light, PAR µ E/m 2 /s DGGE profiles, 16S rRNA gene, v3 region Standard Standard Standard Standard Standard Standard (b) Picocystis (a) (b) (left): Graph showing the distribution of physical properties at a location near the deepest part of the lake, southeast of Paoha Island, on May 17, 2000. The data were collected by lowering a Self-Contained Autonomous MicroProfiler (SCAMP; Precision Measuring Engineering, Carlsbad, CA), a portable, lightweight microstructure profiler designed to measure extremely small-scale (~1mm) fluctuations of electrical conductivity, temperature, and oxygen concentration in lakes, reservoirs, estuaries, and the oceans. SCAMP records at 0.1 second intervals showing water temperature; light intensity; chlorophyll fluorescence. The map also shows the depth below the lake surface at which the other measurements were taken. The data in the panel on the right were generated by analyzing samples of water collected at the depths indicated by the arrows. (b) (right): Results of a DGGE experiment used to resolve the microbial diversity of a Mono Lake sample site according to depth. The arrows point to examples of places where there is a shift in the composition of the microbial community. Most shifts coincide with the chemocline and the oxycline. The dark band in the middle of the lanes continuing across all lanes is from the chloroplast of
Image of page 10
Image of page 11
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern