bakermans bakermans
Currently, I am working with Dr. Mark Skidmore of Montana State University to examine microbial activity in glacial ices. We are examining activity both in model laboratory ices and in situ in glacial systems.
OTHER PROJECTS:
Low-temperature adaptations of bacteria isolated from Siberian permafrost
Characterization of microorganisms from the cold, deep subsurface of the Canadian Arctic
Low-temperature adaptations of bacteria isolated from Siberian permafrost
Despite the plethora of low-temperature habitats
on Earth and the predominance of microorganisms within them, microbiologists have only recently begun to realize the potential for bacteria to actively survive, and even reproduce, in cold environments. Microorganisms that live at subzero temperatures must evolve mechanisms to deal with the accompanying thermodynamic constraints. My research examines the effect of temperature on the growth and physiology of cold-adapted bacteria in the genus Psychrobacter that were isolated from Siberian permafrost. One of these isolates, Psychrobacter cryohalolentis K5, reproduces at 22°C with a generation time of 2.7 hours and reproduces at -10°C with a generation time of 39 days.
I employ physiological, proteomic and genetic approaches in my examination of growth at subzero temperatures. I have applied proteomics to the examination of microbial growth in Psychrobacter cryohalolentis K5 at subzero temperatures (to -6°C) . I have created the first site-specific deletion mutants in Psychrobacter arcticus 273-4, participated in the annotation of the genome of P. arcticus 273-4, and completed the description of two novel species of Psychrobacter.
Most microorganisms isolated from low temperature environments (below 4°C) are eury-, not steno-, psychrophiles. While psychrophiles maximize or maintain growth yield at low temperatures to compensate for low growth rate, the mechanisms involved remain unknown; as does the strategy used by eurypsychrophiles to survive wide ranges of temperatures that include subzero temperatures. I examined the temperature dependence of growth rate, growth yield, and macromolecular (DNA, RNA, and protein) synthesis rates for the eurypsychrophile Psychrobacter cryohalolentis K5. Below 22°C, the growth of P. cryohalolentis was separated into two domains at the critical temperature (Tcritical = 4°C). RNA-, protein-, and DNA-synthesis rates decreased exponentially with decreasing temperatures. Only the temperature dependence of DNA-synthesis rate changed at Tcritical. When normalized to growth rate, RNA and protein synthesis reached a minimum at Tcritical, while DNA synthesis remained constant over the entire temperature range. Growth yield peaked at about Tcritical and declined rapidly as temperature decreased further. Similar to some stenopsychrophiles, P. cryohalolentis maximized growth yield at low temperatures and did so by streamlining growth processes at Tcritical. Identifying the specific processes which cause Tcritical will be vital to understanding both low-temperature growth and growth over a wide range of temperatures.
It is crucial to examine the physiological processes of psychrophiles at temperatures below 4°C, particularly to facilitate extrapolation of laboratory results to in situ activity. Using two dimensional electrophoresis, I examined patterns of protein abundance during growth at 16, 4, and -4°C of the eurypsychrophile Psychrobacter cryohalolentis K5 and reported the first identification of cold inducible proteins (CIPs) present during growth at subzero temperatures. Growth temperature substantially reprogrammed the proteome; the relative abundance of 303 of the 618 protein spots detected (~31% of the proteins at each growth temperature) varied significantly with temperature. Five CIPs were detected specifically at -4°C; their identities (AtpF, EF-Ts, TolC, Pcryo_1988, and FecA) suggested specific stress on energy production, protein synthesis, and transport during growth at subzero temperatures. The need for continual relief of low-temperature stress on these cellular processes was confirmed via identification of 22 additional CIPs whose abundance increased during growth at -4°C (relative to higher temperatures). My data suggested that iron may be limiting during growth at subzero temperatures and that a cold-adapted allele was employed at -4°C for transport of iron. In summary, these data suggest that low-temperature stresses continue to intensify as growth temperatures decrease to -4°C.
Characterization of microorganisms from the cold, deep subsurface of the Canadian Arctic
In collaboration with Tullis Onstott 
(Princeton University) and Lisa Pratt (Indianna University), I have been examining some of the microroganisms living in cold deep-subsurface environments. In conjunction with Wolfden Resourcese, we have worked at two locations within the Canadian Arctic: Lupin and High Lake. In this area of Canada the permafrost is continuous and approximately 500 meters thick.
At the Lupin Mine, we are examining fracture waters collected at depths of 900 and 1100 meters. We have isolated a variety of psychrotolerant aerobic heterotrophs from these waters. An undergraduate at MSU, Rudy Sloup, has been responsible for characterizing these microorganisms.
At High Lake, we obtained cores of the permamently frozen rocks for analysis. Again I am looking for psychrophilic aerobic heterotrophs, while other researchers involved in the project are attempting to isolate anerobes, extracting DNA, extracting lipids and determining the chemical makeup of these rocks.