High pressure and deep subsurface habitats as extremes for many organisms

Transcription

1 High pressure and deep subsurface habitats as extremes for many organisms Hydrostatic pressure increases 1 atm with every 10 m of depth Lithostatic pressure increases 2 atm with every 10 m of depth

2 Barophiles (piezophiles) =organisms which live in high pressure environments. Environments: on oceans floors and deep lakes (hydrostatic pressures), in subsurface rocks (lithostatic pressures) Barotolerants - able to survive at high pressures, but can grow in less extreme environments as well. Usually don't grow at pressures higher than ~ 500 atm. Obligate barophiles (extreme)- cannot grow (or survive?) outside of such environments. Barophiles are generally psychrophilic (below 100m depth the temprature is ~2-3 C) Barophiles grow in darkness -> are very UV sensitive, lacking sufficient mechanisms of DNA repair. Oceans average depth = 3,800m -> pressure of 380 atm Maximal depth = 11,000 m -> maximum pressure of 1100 atm (10 atm = 1 MPa)

3 Obligate barophiles grow better as pressure increases. Obligate barophilic bacteria cannot grow at pressures lower than about 500 atms, but grow best at about 800 atms. E. coli can withstand. high pressures and still retain viability. Under very high pressure E. coli does not grow well, i.e., the cell elongates, but cell division is impaired..

4 What happens at high pressures? High pressure affects cell processes in similar way to low temperatures. High pressure decreases volumes and compresses cell content. A) Decreased cell membrane fluidity. B) Decreased binding capacity of enzymes C) The 3-dimensional structures of DNA and proteins distort and become nonfunctional (D) Motility (bacterial flagellum) is affected (F) Ribosomes are negatively affected

5 Adaptation A1) higher percentages of (poly)unsaturated fatty acids A2) the outer membranes of barophiles tend to have a different protein composition compared to regular microbes. The porins (diffusion channels in membranes) of a barophile can be made up by a specific outer membrane protein (caused by a specific gene which is switched on by high pressure). B) The enzymes of extreme barophiles are often folded differently, in a way so that the pressure has less effect on them. High-pressure genes were found not only in deep-sea adapted microorganisms, but also in bacteria growing at atmospheric pressure; so life emerged from a deep sea environment?

6 Mariana Trench - the deepest sea floor at 10,897 m. In 1996 the Japanese submersible Kaiko scooped out some mud from the Mariana trench sea floor and about180 species of microorganisms were isolated. Many were obligate barophiles and their growth rates were much lower than those of barotolerant microbes.

7 amphipod bacterium Mariana Trench

8 Temperatures are incorrect

9

10 0.403 in

11

12

13

14

15 Deep Subsurface Microbiology i.e. below the surface of the terrestrial earth, or below the ocean seafloor

16 THE DEEP SUBSURFACE BIOSPHERE A new field of study, mostly unexplored Great hoopla at first (in late 1980s & early 90s); enormous biomass? Great difficulties and expense for research: Drilling through various types of rock to depths of hundreds of meters (up to 4 km), sometimes below the seafloor (to 110 C). Who finances the work? Questions: How great a biomass exists? How much of it is viable and growing? What types of microorganisms live there? What is the source of their nutrition and energy? What influence does the type of rock have? Are the microbes ancient or frequently introduced? Could such ecosystems exist on other planets?

17 Examples of thermal gradients * E. of Japan W. Colorado km

18 INEL-1 deep borehole, Idaho vadose zone acoustic velocity temperature

19 Types of subsurface communities investigated 1-10 km J = hydrothermal vent A = highly permeable sediments, South Carolina B = saline, low-permeability sedimentary rock, Virginia C = igneous rocks (granite) and metamorphic rocks, Sweden D = vadose zone (dry), Columbia Basin, Washington E = low-permeability sediments, Colorado F = low-permeability sediments & volcanic tuffs (Nevada test site) G = fractured basalt, Columbia Basin, Washington H = sedimentary rock with volcanic intrusions, Mexico I = low permeability marine sediments, Pacific Ocean

20 Subsurface subjects to think about: First, how do you drill through a few kilometers of rock? 1. How to collect samples without outside contamination 2. Chemistry of the subsurface crack or pore waters 3. Origins of the chemical constituents 4. Chemical reactions occurring in various rocks and sediments (biological or abiological transformations) 5. What types of microorganisms are present (identities based on genetic information and culturing). 6. How are they making a living in various subsurface habitats? 7. How great is the biomass, and how rapidly are the microbes growing or metabolizing? 8. What combination of extremophilic adaptations are involved? Barophily/barotolerance? Thermophily/thermotolerance? Oligotrophic competence?

21

22 Sub-seafloor distribution of prokaryotes near hydrothermal vents Meters below seafloor (mbsf)

23 Examples of deep sub-surface ions and other compounds: (H 2 O assumed) The Usual Suspects (what origins?) H 2, CH 4, H 2 S or HS, Fe(II), Mn(II), NH 4+, N 2, NO 3, O 2, CO 2, HCO 3, SO 4 2-, Fe(III), Mn(IV) Organic C compounds (origins from surface recharge or from reactions of some of the above)

24 Near Pervuvian Trench, drilling to Basaltic basement- 420 mbsf What s wrong with this equation? 6CO H 2 O C 6 H 12 O 6 + 6O 2 + 6H 2 O SO 4 2- from deep brines & NO O 2 from basaltic aquifers?????? DeLong, E.F. (2004) Science 306:

25 Pristine Petroleum or landfill leachate methanogenic SO4reducing Fe(III)-reducing

26 The hydrogen (H 2 ) based ecosystem theory for deep subsurface basalt (Idaho & Nankai Trough) 95% Archaea (mainly thermophilic methanogens) 4 H 2 + CO 2 CH H 2 O [energy] CO 2 (CH 2 O) [cell carbon] H 2 from H 2 O through the heat of radioactive decay of uranium (Chapelle et al. 2002) Or iron in the basalt reduces the H in H 2 O to H 2 gas Thus, in this particular habitat, autotrophic methanogens serve as the base of the food chain However, in most other deep subsurface rocks, methanogens represent only 3-5% of the microbial community. (see Newberry et al Nankai Trough)

27 Newberry, C.J. et al. (2004) Environ. Microbiol. 6: E. of Japan

28 Swedish deep igneous and metamorphic rock sites varying from 100 to 1700 m

29 Log of rates- High Low

30 The deep subsurface biomass of Bacteria and Archaea may (?) exceed the biomass of that above the surface, but the growth and metabolic rates are probably 1/100 to <1/1000 the rates of microorganisms in surface soils and shallow aquatic habitats