Last judgment: the visionary biology of J.B.S. Haldane

This paper seeks to reinterpret the life and work of J. B. S. Haldane by focusing on an illuminating but largely ignored essay he published in1927, “The Last Judgment” – the sequel to his better known work, Daedalus (1924). This astonishing essay expresses a vision of the human future over the next 40,000,000 years, one that revises and updates Wellsian futurism with the long range implications of the “new biology” for human destiny. That vision served as a kind of lifelong credo, one that infused and informed his diverse scientific work, political activities, and popular writing, and that gave unity and coherence to his remarkable career. This revised version was published online in July 2006 with corrections to the Cover Date.     

Relations between biochemical thermodynamics and biochemical kinetics

The parameters in steady-state or rapid-equilibrium rate equations for enzyme-catalyzed reactions depend on the temperature, pH, and ionic strength, and may depend on the concentrations of specific species in the buffer. When the complete rate equation (i.e. the equation with parameters for the reverse reaction as well as the forward reaction) is determined, there are one or more Haldane relations between some of the kinetic parameters and the apparent equilibrium constant for the reaction that is catalyzed. When the apparent equilibrium constant can be calculated from the kinetic parameters, the equilibrium composition can be calculated. This is remarkable because the kinetic parameters all depend on the properties of the enzymatic site, but the apparent equilibrium constant and the equilibrium composition do not. The effects of ionic strength and pH on the unoccupied enzymatic site and the occupied enzymatic site have to cancel in the Haldane relation or in the calculation of the apparent equilibrium constant using the rate constants for the steps in the mechanism. Several simple enzymatic mechanisms and their complete rate equations are discussed.     

Natural selection along an environmental gradient: a classic cline in mouse pigmentation

We revisited a classic study of morphological variation in the oldfield mouse ( Peromyscus polionotus ) to estimate the strength of selection acting on pigmentation patterns and to identify the underlying genes. We measured 215 specimens collected by Francis Sumner in the 1920s from eight populations across a 155-km, environmentally variable transect from the white sands of Florida's Gulf coast to the dark, loamy soil of southeastern Alabama. Like Sumner, we found significant variation among populations: mice inhabiting coastal sand dunes had larger feet, longer tails, and lighter pigmentation than inland populations. Most striking, all seven pigmentation traits examined showed a sharp decrease in reflectance about 55 km from the coast, with most of the phenotypic change occurring over less than 10 km. The largest change in soil reflectance occurred just south of this break in pigmentation. Geographic analysis of microsatellite markers shows little interpopulation differentiation, so the abrupt change in pigmentation is not associated with recent secondary contact or reduced gene flow between adjacent populations. Using these genetic data, we estimated that the strength of selection needed to maintain the observed distribution of pigment traits ranged from 0.0004 to 21%, depending on the trait and model used. We also examined changes in allele frequency of SNPs in two pigmentation genes, Mc1r and Agouti , and show that mutations in the cis -regulatory region of Agouti may contribute to this cline in pigmentation. The concordance between environmental variation and pigmentation in the face of high levels of interpopulation gene flow strongly implies that natural selection is maintaining a steep cline in pigmentation and the genes underlying it.     

Growth Kinetics of Microbacterium lacticum and Nitrate-Dependent Degradation of Ethylbenzene under Anaerobic Conditions

A pure strain of Microbacterium lacticum DJ-1 capable of anaer-obic biodegradation of ethylbenzene was isolated from soil contaminated with gasoline. Growth of the strain and biodegradation of ethylbenzene in batch cultures led to stoichiometric reduction of nitrate. M. lacticum DJ-1 could degrade 100 mg L^?1 of ethylbenzene completely, with a maximum degradation rate of 15.02 ± 1.14 mg L^?1 day^?1. Increasing the initial concentration of ethy-lbenzene resulted in decreased degradative ability. The cell-specific growth rates on ethylbenzene conformed to the Haldane–Andrew model in the substrate level range of 10–150 mg L^?1. Kinetic parameters were determined by nonlinear regression on specific growth rates and various initial substrate concentrat-ions, and the values of the maximum specific growth rate, half saturation constant, and inhibition constant were 0.71 day^?1, 34.3 mg L^?1, and 183.5 mg L^?1, respectively. This is the first report of ethylbenzene biodegradation by a bacterium of Microbacterium lacticum under nitrate-reducing conditions.     

Phenol degradation performance by isolated Bacillus cereus immobilized in alginate

Phenol degradation by Bacillus cereus AKG1 MTCC9817 and AKG2 MTCC 9818 was investigated and degradation kinetics are reported for the free and Ca-alginate gel-immobilized systems. The optimal pH for maximum phenol degradation by immobilized AKG1 and AKG2 was found to be 6.7 and 6.9, respectively, while 3% alginate was optimum for both the strains. The degradation of phenol by free as well as immobilized cells was comparable at lower concentrations of phenol (100–1000 mg l⁻¹). However, the degradation efficiency of the immobilized strains was higher than that of the free strains at higher phenol concentrations (1500–2000 mg l⁻¹), indicating the improved tolerance of the immobilized cells toward phenol toxicity. More than 50% of 2000 mg l⁻¹ phenol was degraded by immobilized AKG1 and AKG2 within 26 and 36 days, respectively. Degradation kinetics of phenol by free and immobilized cells are well represented by the Haldane and Yano model.     

Science,philosophy, and politics in the work of J. B. S. Haldane, 1922–1937

This paper analyzes the interaction between science, philosophy and politics (including ideology) in the early work of J. B. S. Haldane (from 1922 to 1937). This period is particularly important, not only because it is the period of Haldane's most significant biological work (both in biochemistry and genetics), but also because it is during this period that his philosophical and political views underwent their most significant transformation. His philosophical stance first changed from a radical organicism to a position far more compatible with mechanical materialism. The primary intellectual influence that was responsible for this shift was that of F. G. Hopkins. Later, Haldane came to accept Marxism and its official metaphysics, dialectical materialism, a move that let him accept the materialist conception of the world while still maintaining a resolute distance from mechanism. Throughout all these changes, what is most obvious is the influence of science on Haldane's philosophical views. An influence in the opposite direction is far less apparent.Parts of this paper are extracted from a longer work which concerns the interactions between philosophy and science throughout Haldane's scientific career (Sarkar forthcoming). The general conclusions reached here, from a consideration of Haldane's work only from 1922 to 1937 (see Section 6), remain the same for the rest of his life, as is detailed in the longer work. Thanks are due to R. S. Cohen, J. F. Crow, A. R. Fersht, J. Maynard Smith, R. C. Olby, D. Paul, M. Ruse, J. Stachel and S. Sturdy for helpful discussions and comments and criticism of the positions outlined in this paper. This is Contribution No. BTBG-92-4 from the Theoretical Biology Group, Boston University.     

Biodegradation of acetonitrile by adapted biofilm in a membrane-aerated biofilm reactor

A membrane-aerated biofilm reactor (MABR) was developed to degrade acetonitrile (ACN) in aqueous solutions. The reactor was seeded with an adapted activated sludge consortium as the inoculum and operated under step increases in ACN loading rate through increasing ACN concentrations in the influent. Initially, the MABR started at a moderate selection pressure, with a hydraulic retention time of 16 h, a recirculation rate of 8 cm/s and a starting ACN concentration of 250 mg/l to boost the growth of the biofilm mass on the membrane and to avoid its loss by hydraulic washout. The step increase in the influent ACN concentration was implemented once ACN concentration in the effluent showed almost complete removal in each stage. The specific ACN degradation rate achieved the highest at the loading rate of 101.1 mg ACN/g-VSS h (VSS, volatile suspended solids) and then declined with the further increases in the influent ACN concentration, attributed to the substrate inhibition effect. The adapted membrane-aerated biofilm was capable of completely removing ACN at the removal capacity of up to 21.1 g ACN/m² day, and generated negligible amount of suspended sludge in the effluent. Batch incubation experiments also demonstrated that the ACN-degrading biofilm can degrade other organonitriles, such as acrylonitrile and benzonitrile as well. Denaturing gradient gel electrophoresis studies showed that the ACN-degrading biofilms contained a stable microbial population with a low diversity of sequence of community 16S rRNA gene fragments. Specific oxygen utilization rates were found to increase with the increases in the biofilm thickness, suggesting that the biofilm formation process can enhance the metabolic degradation efficiency towards ACN in the MABR. The study contributes to a better understanding in microbial adaptation in a MABR for biodegradation of ACN. It also highlights the potential benefits in using MABRs for biodegradation of organonitrile contaminants in industrial wastewater.     

Kinetics and modeling of reductive dechlorination at high PCE and TCE concentrations

Two biokinetic models employing the Michaelis-Menten equation for anaerobic reductive dechlorination of tetrachloroethylene (PCE) and trichloroethylene (TCE) were developed. The models were compared with results from batch kinetic tests conducted over a wide range of PCE and TCE concentrations with two different dechlorinating cultures. One model applies Michaelis-Menten kinetics with competitive inhibition among chlorinated aliphatic hydrocarbons (CAHs), while the other model includes both competitive inhibition and Haldane inhibition at high CAH concentrations. Model simulations with competitive inhibition simulated the experimental results well for PCE concentrations lower than 300 microM. However, simulations deviated from the experimental observations for PCE or TCE concentrations greater than 300-400 microM. The kinetic model that incorporated both competitive and Haldane inhibitions better simulated experimental data for PCE concentrations near the solubility limit (1000 microM), and TCE concentrations at half its solubility limit (4000 microM). Based on the modeling analysis of the experimental results, the PM culture (Point Mugu, CA) had very high Haldane inhibition constants for cis-1,2-dichlororethylene (c-DCE) and vinyl chloride (VC) (6000 and 7000 microM, respectively), indicating very weak Haldane inhibition, while the EV culture (the Evanite site in Corvallis, OR) had lower Haldane inhibition constants for TCE, c-DCE, and VC of 900, 750, and 750 microM, respectively. The BM culture (a binary mixed culture of the PM and EV cultures) had transformation abilities that represented the mixture of the EV and PM cultures. Model simulations of the BM culture transformation abilities were well represented by separate rate equations and model parameters for the two independent cultures that were simultaneously solved. Modeling results indicated that a combination of competitive and Haldane inhibition kinetics is required to simulate dechlorination over a broad range of concentrations up to the solubility limit of PCE and half the solubility limit of TCE.     

Instinct in the '50s: the British reception of Konrad Lorenz's theory of instinctive behavior<Superscript>*</Superscript>

At the beginning of the 1950s most students of animal behavior in Britain saw the instinct concept developed by Konrad Lorenz in the 1930s as the central theoretical construct of the new ethology. In the mid 1950s J.B.S. Haldane made substantial efforts to undermine Lorenz's status as the founder of the new discipline, challenging his priority on key ethological concepts. Haldane was also critical of Lorenz's sharp distinction between instinctive and learnt behavior. This was inconsistent with Haldane's account of the evolution of language, and, according to Haldane, inconsistent with elementary genetics. British attitudes to the instinct concept changed dramatically in the wake of Daniel S. Lehraman's 1953 critique of Lorenz, and by the 1960s Lorenz drew a clear distinction between his own views and those of the English-speaking ethologists. The inconsistencies between Lorenz's ideas and the trends in contemporary evolutionary genetics that are reflected in Haldane's critiques may help to explain why the Lorenzian instinct concept was unable to maintain itself in Britian.