Phosphatase activities of endolithic communities in rocks of the Antarctic Dry Valleys

• Published in: Microbial Ecology
• Main Authors: Banerjee, M., Whitton, B.A., Wynn-Williams, D.D.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer 2000
• Subjects: Antarctic; The Antarctic; McMurdo Dry Valleys; Antarc*; Antarctica
• Online Access: http://nora.nerc.ac.uk/id/eprint/20403/; https://doi.org/10.1007/s002489900188

Phosphorus is scarce in Beacon Sandstone of the McMurdo Dry Valleys, Antarctica, and any input from precipitation is minimal. In endolithic microbial communities recycling of P by the action of phosphatases may therefore be important. The phosphatase activities of three different types of endolithic communities in the McMurdo Dry Valley, Antarctica, were studied in the laboratory. The dominant phototrophs were Chroococcidiopsis, mixed Gloeocapsa and Trebouxia, and Trebouxia. Bacteria were also visually conspicuous in the latter two communities, and the Trebouxia in both cases formed a lichenized association with fungal hyphae. In each case marked phosphomonoesterase (PMEase) activity was found in assays with 4-methylumbelliferyl phosphate (MUP) or p-nitrophenyl phosphate as substrate, and phosphodiesterase activity with bis-p-nitrophenyl phosphate as substrate. The pH optimum of PMEase (assayed at 0.5 pH intervals) of the Chroococcidiopsis, Gloeocapsa–Trebouxia, and Trebouxia communities was 9.5, 5.5, and 8.0, respectively. These values are similar for aqueous extracts of the respective rocks (pH 9.2, 6.2, 7.5). All three communities showed significantly higher PMEase activity at 5° than 1°C, and the first two also showed much higher activity at 5° than 10°C. All three communities also showed slightly lower activity in the light (7 μmol photon m-2 s-1) than the dark; this was found with all substrates and substrate concentrations. Prior exposure of a moistened sample to light for 2 h led to a reduction in activity even when the subsequent assay was done in the dark. The rate of PMEase activity (using 100 μM MUP) in the Gloeocapsa–Trebouxia and Trebouxia communities was approximately linear with time up to 24 h, whereas the Chroococcidiopsis community showed a marked decrease after 6 h. At least part of this was due to retention of the 4-methylumbelliferone (MU) hydrolysis product. In spite of the assays being conducted on a whole community, the activity–substrate relationship in each case quite closely resembled ...