Abstract:
In this study, the active microbial component in the Dry Valleys system was characterized using newly developed molecular techniques with the aid of in situ augmentation and cloches (wind protection) which dampen the effects of the extreme weather conditions unique to the ecosystem. The aim was to ascertain those bacteria that are truly functional and to understand the environmental factors
... driving the incredible microbial diversity in this system. 152 mineral soil samples and 145 hypolith samples were collected from the Miers Valley. Two mummified seal tissue samples were also collected. Mineral soil samples were collected from Battleship Promontory and from the Upper Wright Valley. Some rock samples were also collected from Battleship Promontory, Marble Point and the Upper Wright Valley. Soil samples were also used for in situ augmentation and stable isotope probing (SIP) experiments in conjunction with cloches. Specific experiments include: 1) Microbial biomass was determined by in situ ATP analysis. 2) The drivers for microbial diversity were identified from collected soil samples subjected to in situ incubation after augmentation of carbon (glucose), nitrogen (NH4Cl), water (deionized and sterile) or combinations of these potential drivers. ATP levels and CO2 flux were measured for augmented samples over time to monitor the effect of those augmentations on overall biomass and activity and then analysed further using molecular techniques. 3) SIP analysis was used to augment microbial communities in soil, followed by extraction of total DNA. Organisms that are alive and active and respond to the addition of the isotope incorporate it into their DNA. 4) Cloches were used to trap heat from solar radiation and provide shelter from cooling winds. In situ soil augmentation and SIP experiments were placed in cloches to dampen the effects of extreme weather on the samples and to maximize solar gain. 5) DNA and RNA were extracted to provide zero-time controls. 6) The quality of water present in the soil was determined by measuring water activity and water potential. 7) The flux of CO2 out of the augmented (under seal or hypolith) soil compared to an unaugmented control was measured. 8) Replicate hypolith samples of structurally different classes were sampled and subsequently weighed for carbon and nitrogen analysis. Data loggers measured temperature, soil humidity and incident light over a 7 day period. Sensors were deployed for long term measurments. Collected samples (comprising DNA extracts, soil samples, mummified seal tissue samples, RNALater-stabilised soil samples, rock samples, hypolith samples) were returned to the University of Waikato. 
