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Applied and Environmental Microbiology (1)
Journal of the Experimental Analysis of Behavior (1)
Clark, Douglas S. (1)
Gollub, Lewis R. (1)
Ludlow, Jan M. (1)
Merigan, William H. (1)
Miller, Jay F. (1)
Miller, Jay S. (1)
Nelson, Chad M. (1)
Shah, Nilesh N. (1)
Year of Publication
Pressure and Temperature Effects on Growth and Methane Production of the Extreme Thermophile Methanococcus jannaschii
Shah, Nilesh N.
Nelson, Chad M.
Ludlow, Jan M.
Clark, Douglas S.
Applied and Environmental Microbiology
The marine archaebacterium Methanococcus jannaschii was studied at high temperatures and hyperbaric pressures of helium to investigate the effect of pressure on the behavior of a deep-sea thermophile. Methanogenesis and growth (as measured by protein production) at both 86 and 90°C were accelerated by pressure up to 750 atm (1 atm = 101.29kPa), but growth was not observed above 90°C at either 7.8 or 250 atm. However, growth and methanogenesis were uncoupled above 90°C, and the high-temperature limit for methanogenesis was increased by pressure. Substantial methane formation was evident at 98°C and 250 atm, whereas no methane formation was observed at 94°C and 7.8 atm. In contrast, when argon was substituted for helium as the pressurizing gas at 250 atm, no methane was produced at 86°C. Methanogenesis was also suppressed at 86°C and 250 atm when the culture was pressurized with a 4:1 mix of H2 and CO2, although limited methanogenesis did occur when the culture was pressurized with H2.
Short-component multiple schedules: effects of relative reinforcement duration1
Merigan, William H.
Gollub, Lewis R.
Journal of the Experimental Analysis of Behavior
Pigeons were exposed to multiple variable-interval 2-min variable-interval 2-min schedules of food presentation in which relative duration of food presentation was manipulated. When components alternated every 5 sec and were scheduled on separate response keys, relative response rates closely matched relative reinforcement duration in three of four pigeons. On the other hand, relative response rates were insensitive to relative reinforcement duration when components scheduled on a single response key alternated every 5 sec, and when components scheduled on separate response keys alternated every 2 min. Thus, both rapid alternation and spatial separation of components were necessary to produce approximate matching of relative responding to relative reinforcement duration. This finding contrasts with previous findings that only rapid component alternation is necessary for matching when relative rate of reinforcement is manipulated.
reinforcement duration; component duration; relative response rates; multiple schedules; key peck; pigeons
Results 1-2 (2)
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