An H-2 haplotype possibly derived by crossing-over between the (A α A β ) duplex and the E βlocus

The B10.STA62 strain carries the H-2 ^w27 haplotype derived from a wild mouse captured in the vicinity of Ann Arbor, Michigan. Products of two class II loci composing this haplotype, A and A , are serologically, biochemically (by tryptic peptide mapping), and functionally indistinguishable from products controlled by the A ^b and A ^/b genes of the B10.A(5R) strain. In contrast, the polypeptide chain controlled by the third class II locus, E , is different from that controlled by the E ^/b gene. This E ^/w27 chain lacks an antigenic determinant present on the E^b molecule and carries determinants lacking on the E^b molecule, the E ^/b and E ^/w27 peptide maps differ in at least six peptides, and cytotoxic T cells specific for the E ^b chains do not react with B10.STA62 target cells. This great difference between the E ^/b and E ^/w27 chains suggests that the corresponding genes have not been derived from one another by a direct mutational conversion; instead, H-2 ^w27 appears to be a recombinant haplotype derived by crossing-over between the A A duplex and the E locus. This is the first recombinant discovered separating these class II loci.     

Integration of bacteriophages lambda and phi 80 in wild-type Escherichia coli at secondary attachment sites. I. Formation of secondary lysogens

Summary The family of lambdoid phages displays a varying specificity of integration into the host chromosome. The phage DNA failed to get inserted at the secondary site(s) of the gal operon (frequency <2.6x10^-8) in the presence of the primary (normal) att site. By contrast, 80 and the att80 hybrid (x80) became integrated into wild-type Escherichia coli at at least two secondary att sites of the btuB locus, and the latter near purE and purC as well (frequency 2x10^-3-10^-4). The integration of 80 and att80 into btuB occurred with about the same frequency as in cells in which the normal insertion site had been deleted (0.7-4.0x10^-6). An analysis of the secondary lysogens with the prophage in btuB showed them to be polylysogens; the additional prophage(s) was found at the primary att site. We also failed to observe the integration into other loci of 80 and att80 with the formation of secondary monolysogens (frequency <0.0035 at MOI-10^-3 or 10). It is presumed that these prophages become integrated at secondary att sites only if the primary site is occupied.Abbreviations MOI multiplicity of infection (PFU/cell) - PFU plaque-forming unit - TP transducing phage - P1/HfrH P1vir multiplied on HfrH - Rif-R rifampin-resistance - Int int protein     

Analysis of ligand-binding to the kringle 4 fragment from human plasminogen

The interaction of the isolated human plasminogen kringle 4 with the four -amino acid ligands -aminocaproic acid (ACA), N-acetyl-l-lysine (AcLys), trans-aminomethyl(cyclohexane)carboxylic acid (AMCHA) and p-benzylaminesulfonic acid (BASA) has been further characterized by ¹H-NMR spectroscopy at 300 and 600 MHz. Pronounced high-field shifts, reaching 3 ppm, are observed for AMCHA resonances upon binding to kringle 4, which underscores the relevance of ligand lipophilic interactions with aromatic side chains at the binding site. Ligand titration curves for the nine His and Trp singlets found in the kringle 4 aromatic spectrum reveal a striking uniformity in the kringle response to the various ligands. The average binding curves exhibit a clear Langmuir absorption isotherm saturation profile and the data were analyzed under the assumption of one (high affinity) binding site per kringle. Equilibrium association constants (K _a ) and first order dissociation rate constants (k _off) were derived from linearized expressions of the Langmuir isotherm and of the spectral line-shapes, respectively. The results for the four ligands, at 295 K, pH^* 7.2, indicate that: (a) AMCHA exhibits the strongest binding (K _a =159 mM ^-1) and ACA the weakest (K _a =21 mM ^–1) with AcLys and BASA falling in between; (b) ACA dissociates readily (k _off = 5.3 × 10³ s^–1) and AMCHA associates the fastest (k _off = 2.0 × 10⁸ M ^–1 s^–1) while the kinetics for BASA exchange is relatively slow (k _off = 0.8 × 10³ s^–1, k _on = 0.6 × 10⁸ M ^–1s^–1); (c) the ligand-binding kinetics is close to diffussion-controlled.Abbreviations ACA -aminocaproic acid - AcLys N-acetyl-l-lysine - AMCHA t-aminomethyl(cyclohexane)carboxylic acid - BASA p-benzylaminesulfonic acid - K4 kringle 4 - NOE nuclear Overhauser effect - ppm parts-per-million - pH^* glass electrode pH reading uncorrected for deuterium isotope effects - K _a ligand-kringle 4 equilibrium association constant - k _off ligand-kringle 4 dissociation rate constant - k _on ligand-kringle 4 association rate constant     

Composition and ecology of the human intestinal flora

Longitudinal quantitative cultures of fecal flora of 20 newborns, 4 older babies and 10 healthy adults were carried out to study the composition and development of the intestinal flora. In all newborns the same sequence of colonization was observed. The numbers of aerobic and anaerobic bacteria fluctuated and reached finally numbers of 10¹⁰/g wet weight. In adults the flora was in balance with 10⁵–10⁷ aerobic and 10¹⁰–10¹¹ anaerobic bacteria/g wet weight. Interaction experiments in vitro showed growth inhibition of Bacteroides fragilis by all intestinal species isolated. Bifidobacteria were not inhibited. The assumption was made that this type of interaction could be one of the mechanisms involved in the intestinal micro-ecology. Three of the Bacteroides fragilis strains tested were able to grow on natural intestinal substrates as gastric mucin, glycogen and a variety of plant polysaccharides. Acetic, lactic, propionic and succinic acids were detected as fermentation products.     

High frequency transformation of Alcaligenes eutrophus producing poly-β-hydroxybutyric acid by electroporation

Summary A strain of Alcaligenes eutrophus producing poly--hydroxybutyric acid was successfully transformed by the electroporation. The plasmid used was a broad host range plasmid pKT230 conferring kanamycin resistance. The optimum yield of transformant was 0.8×10²/g DNA when 50 l competent cells at 10¹⁰/ml were pulsed by 11.5 kV/cm for 5 ms with 1 g DNA. Plasmid DNA in the A. eutrophus transformant was stably maintained as a monomeric structure.     

A Tcra congenic mouse: Vα epitope expression is influenced by both Tcra haplotypes and background genes

A T-cell receptor alpha chain locus (Tcra) congenic mouse is described. The Tcra ^a haplotype of BALB/c (donor strain) was bred on to B10.D2 (background strain, Tcra ^b haplotype) by using a Bgl I Tcra-C restriction fragment length polymorphism. Tcra ^a/b heterozygous offspring from the eleventh backross generation were brother-sister mated to obtain Tcra-C ^a homozygous animals. The resulting congenic line, B10.D2.C-Tcra ^a /Bo carries a recombination between the Tcra and the hr loci; thus, the transferred differential segment is the centromeric 18–27 cM of the BALB/c chromosome 14. Analysis with a multitude of Tcra-V and Tcrd-V probes demonstrates that the complete Tcra ^a haplotype is contained within this differential segment. Lymph node T cells of BALB/c (Tcra ^a ) B10.D2 (Tcra ^b ) and B10.D2.C-Tcra ^a were stained with anti-V8 (KT50, KT65), anti-V3.2 (RR3-16) and anti-V11.1 and 2 (RR8-1) monoclonal antibodies. We find that the frequencies of V epitope expression are highly Tcra haplotype-dependent even though an influence of background genes is also observed. Thus, Tcra-V germline differences may possibly influence the T cell repertoire, in addition to the already well known positive and negative thymic selections. Tcra haplotype does not influence the frequencies of V utilization. However, BALB/c mice have fewer V11⁺ T cells than B10.D2 and B10.D2-Tcra ^a , therefore, the BALB/c genome must harbor a V11 deleting gene(s) in addition to those described so far.     

Arsenic concentrations in water and fish from Chautauqua Lake,New York

Synopsis Arsenic persists in Chautauqua Lake, New York waters 13 years after cessation of herbicide (sodium arsenite) application and continues to cycle within the lake. Arsenic concentrations in lake water ranged from 22.4–114.81 g l^–1, = 49.0 ag l^–1. Well water samples generally contained less than 10 g l^–1 arsenic. Arsenic concentrations in lake water exceeded U.S. Public Health Service recommended maximum concentrations (10 g l^–1) and many samples exceeded the maximum permissible limit (50 g l^–1). Fish accumulated arsenic from water but did not magnify it. Fish to water arsenic ratios ranged from 0.4–41.6. Black crappie (Pomoxis nigromaculatus) contained the highest arsenic concentrations (0.14–2.04 g g^–1 ), X = 0.7 g g^–1) while perch (Perca flavescens), muskellunge (Esox masquinongy) and largemouth bass (Micropterus salmoides) contained the lowest concentrations (0.02–0.13 g g^–1). Arsenic concentrations in fish do not appear to pose a health hazard for human consumers.     

Changes of fluorescence lifetime and rotational correlation time of bovine serum albumin labeled with 1-dimethylaminonaphthalene-5-sulfonyl chloride in guanidine and thermal denaturations

The nanosecond fluorescence depolarization method was applied to measure the fluorescence lifetime () and the rotational correlation time () of bovine serum albumin (BSA) labeled with 1-dimethylaminonaphthalene-5-sulfonyl chloride (dansyl-Cl). Changes of and of dansyl BSA in the guanidine denaturation and in the thermal denaturation were examined. In parallel, the secondary structural change of dansyl BSA was followed by circular dichroism measurements. The magnitude of was almost unchanged between 1 and 2 M guanidine, where the secondary structure of the protein was predominantly disrupted; whereas that of began to increase before the disruption of secondary structure in the guanidine denaturation. In the thermal denaturation, in contrast, changes of both and occurred in a temperature range where the secondary structure was predominantly disrupted. The volume of equivalent sphere (V _e ) and the axial ratio () for the BSA were 3.6–3.8×10^–19 cm³ and 3.6 at 2M guanidine as against 2.1×10^–19 cm³ and 2.2 in the absence of guanidine (25°C), respectively. The magnitudes ofV _e and were 4.9×10^–19 cm³ and 4.5 at 65°C, respectively. Although the secondary structural change of dansyl BSA was irreversible in the thermal denaturation,V _e and were reversible.     

Development of an electro-transformation system for Escherichia coli DH10B

Summary Escherichia coli can be transformed to high efficiencies by subjecting a mixture of cells and DNA to a brief but intense electrical field. Factors that affect the transformation efficiency of E.coli strain DH10B were analysed. Optimal conditions gave an efficiency of 10⁸ to 10⁹ transformants/g DNA with E.coli strains K803 and DH10B, and plasmids pB1221.23 and pBSK+. The use of ligated DNA resulted in 10⁶ transformants/g DNA. Detailed protocols for these systems are given.     

Genetical studies on the heterocyst and nitrogen fixation of the blue-green alga Nostoc muscorum

Summary The short-trichome-forming, non-heterocystous and non-nitrogen-fixing (het ^– nif^–) mutant of the nitrogen-fixing blue-green alga Nostoc muscorum was isolated by N-methyl-N-nitro-N-nitrosoguanidine (NTG)-mutagenesis after penicillin enrichment technique and characterized. The mutant did not grow and fix nitrogen in combined-nitrogen-free medium while in nitrate-containing medium it grew well (K=0.112/day, G=64.27 h), although its growth was comparatively poor than the parent alga (K=0.128/day; G=56.14 h). The mutant was stable and both the het ^– and nif ^– characters reverted to wild type (het ⁺ nif⁺) with the reversion frequency of 2.62×10^-7.The het ^– nif^– mutant tolerated 0.5 g/ml of streptomycin sulphate on the agar medium and its streptomycin resistant mutant capable of growing in presence of 10g/ml of streptomycin was isolated spontaneously with a frequency of 1.45×10^-8. These streptomycin resistant isolates (het ^– nif^– str^R) resisted 100 g/ml of streptomycin sulphate on the agar medium and 200 g/ml in liquid medium. Spontaneous virus-resistant mutant of het ^– nif^– str^R was isolated with a mutation frequency of 4.02×10^-4.The data of genetic recombination experiments suggested that there is transfer of both het and nif genes to het ^– nif^– strain with the frequency of 2×10^-6 to 2×10^-5 simultaneously. There was increase in recombination frequency with increasing the incubation period. The virus-resistance marker is also transferred to the sensitive recipient.Abbreviations CFU colony forming units - C–N Chu-10 medium without combined nitrogen - C+N Chu-10 medium with 0.232 g/l calcium nitrate - G generation time - het heterocyst differentiating genes - K specific growth rate constant - MOI multiplicity of infection - nif nitrogen-fixing genes - NTG N-methyl-N-nitro-N-nitrosoguanidine - PFU plaque forming units - str ^R streptomycin resistance - str ^R streptomycin sensitive     

Increased taxane accumulation in callus cultures of Taxus cuspidata and Taxus × media by some elicitors and precursors

In Taxus cuspidata callus, vanadyl sulfate (10 mg l^–1) induced a high (146 g g^–1 dry wt) production of 10-deacetylbaccatin III in comparison to 7 g g^–1 dry wt of the control. The content of paclitaxel in this species increased from 16 g g^–1 to 74 g g^–1 dry wt when 20 mg phenylalanine l^–1 was used. In T. media, p-aminobenzoic acid induced the highest content of 10-deacetylbaccatin III (481 g g^–1 dry wt) versus 181 g g^–1 in the control. Paclitaxel increased from 89 to 139 g g^–1 dry wt after adding chitosan (20 mg l^–1) to the cultures.     

Measurement of diameters of estuarine bacteria and particulates in natural water samples by use of a submicron particle analyzer

Desulfovibrio vulgaris strain Madison outcompetedMethanobacterium strain ivanov for hydrogen when sulfate was in excess because of higher cell yield and growth rate and a greater affinity for hydrogen as a consequence of a lower Km and higher Vmax for in vivo hydrogenase activity.Desulfovibrio vulgaris displayed a growth yield of 1.1 g/mol H₂, a Km for tritium exchange of 4 M, and a specific in vivo hydrogenase activity of 2.17 DPM³H₂O×10³/g cell protein/h; whereasMethanobacterium strain ivanov had a yield of 0.6 g/mol H₂, a Km for tritium exchange of 14 M, and a specific in vivo hydrogenase activity of 0.38 DPM³H₂O×10³/g cell protein/h. Under these physiological conditions, the Gibbs free-energy change associated with methanogenesis and sulfidogenesis from H₂ was calculated to be-47.4 kJ/mol and-62.9 kJ/mol, respectively. When sulfidogenesis was limited by sulfate concentration, the methanogen was able to successfully compete with the sulfidogen for hydrogen. Competition between methanogens and sulfidogens for hydrogen is explained in terms of thermodynamic, kinetic, and other important considerations not discussed in the previous literature.     

Electrotransformation of intact cells ofBrevibacterium flavum MJ-233

Summary Electroporation allowed transformation of intact cells ofBrevibacterium flavum MJ-233. The two plasmids used for electroporation were pCRY2 (6.3 kilobases) and pCRY3 (8.2 kilobases). Both plasmids contain the chloramphenicol-resistance gene and the autonomous replication origin inB. flavum MJ-233. The efficiency of electrotransformation was optimal with cells harvested at the middle log phase of growth, and was imporved by the addition of 1.0U/ml of penicillin G to the culture medium. The optimum yield of transformants per g DNA was 5×10⁴ when the cell suspension was pulsed at a cell density of 1×10¹⁰/ml and at a DNA amount of 1.0g.     

Flight of the honey bee VI: energetics of wind tunnel exhaustion flights at defined fuel content,speed adaptation and aerodynamics

To gain information on extended flight energetics, quasi-natural flight conditions imitating steady horizontal flight were set by combining the tetheredflight wind-tunnel method with the exhaustion-flight method. The bees were suspended from a two-component aerodynamic balance at different, near optimum body angle of attack and were allowed to choose their own speed: their body mass and body weight was determined before and after a flight; their speed, lift, wingbeat frequency and total flight time were measured throughout a flight. These values were used to determine thrust, resultant aerodynamic force (magnitude and tilting angle), Reynolds number, total flight distance and total flight impulse. Flights in which lift was body weight were mostly obtained. Bees, flown to complete exhausion, were refed with 5, 10, 15 or 20 l of a 1.28-mol·l^-1 glucose solution (energy content w=18.5, 37.0, 55.5 or 74.0 J) and again flown to complete exhaustion at an ambient temperature of 25±1.5°C by a flight of known duration such that the calculation of absolute and relative metabolic power was possible. Mean body mass after exhaustion was 76.49±3.52 mg. During long term flights of 7.47–31.30 min similar changes in flight velocity, lift, thrust, aerodynamic force, wingbeat frequency and tilting angle took place, independent of the volume of feeding solution. After increasing rapidly within 15 s a more or less steady phase of 60–80% of total flight time, showing only a slight decrease, was followed by a steeper, more irregular decrease, finally reaching 0 within 20–30 s. In steady phases lift was nearly equal to resultant aerodynamic force; tilting angle was 79.8±4.0°, thrust to lift radio did not vary, thrust was 18.0±7.4% of lift, lift was somewhat higher/equal/lower than body mass in 61.3%, 16.1%, 22.6% of all totally analysable flights (n=31). The following parameters were varied as functions of volume of feeding solution (5–20 l in steps of 5 l) and energy content. (18.5–74.0 J in steps of 18.5 J): total flight time, velocity, total flight distance, mean lift, thrust, mean resultant aerodynamic force, tilting angle, total flight impulse, wingbeat frequency, metabolic power and metabolic power related to body mass, the latter related to empty, full and mean (=100 mg) body mass. The following positive correlations were found: L=1.069·10^-9 f ^2.538; R=1.629·10^-9 f ^2.464; P _m=7.079·10^-8 f ^2.456; P _m=0.008v+0.008; P _m=18.996L+0.022; P _m=19.782R+0.021; P _m=82.143T+0.028; P _m=1.245·bm _f ^1.424 ; P _{mrel e}=6.471·bm _f ^1.040 ; =83.248+0.385. The following negative correlations were found: V=3.939–0.032; T=1.324·10^-4–0.038·10^-4. Statistically significant correlations were not found in T(f), L(), R(), f(), P _m(bm _e), P _{m rel e}(bm _e), P _{m rel f}(bm _e), P _{m rel f}(bm _f).Abbreviations A(m²) frontal area - bl(m) body length - bm(mg) body mass - c(mol·1^-1) glucose concentration of feeding solution - c _D (dimensionless) drag coefficient, related to A - D(N) drag - F _w(N) body weight - F _wp weight of paper fragment lost at flight start - f wingbeat frequency (s^-1) - g(=9.81 m·s^-2) gravitational acceleration - I(Ns)=R(t) dt total impulse of a flight - L(N) lift vertical sustaining force component - P _m(J·s^-1=W) metabolic power - P_{m ret} (W·g^-1) metabolic power, related to body mass - R(N) resultant aerodynamic force - Re v·bl·v ^-1 (dimensionless) Reynolds number, related to body length - s(m) v(t) dt virtual flight distance of a flight - s(km) total virtual flight distance - T (N) thrust horizontal force component of horizontal flight - T _a (°C) ambient temperature - t(s) time - t _tot (s or min) total flight time - v(m·s^-1) flight velocity - v(l) volume of feeding solution - W (J) energy and energy content of V - ( °) body angle of attack between body longitudinal axis and flow direction - ( °) tilting angle ( 90°) between R and the horizont in horizontal flight v(=1.53·10^-5m²·s^-1 for air at 25°) kinematic viscosity - (=1.2 kg·m^-3 at 25°C) air density     

Opioid receptor binding in rat spinal cord

The interaction of various radioligands with spinal opioid receptors has been characterized under variable experimental conditions. Binding to , , and sites was measured in all (cervical, thoracic, lumbar) segments. The apparent affinity constant (K) of [³H]Ethylketocyclazocine (EKC) was similar in Tris, 2.09 (±1.06)×10⁸ M^–1, and phosphate buffer, 2.16 (±0.02)×10⁸ M^–1, when its interaction with and sites was blocked. Without blocking ligands, EKC binding was resolved in two components:K ₁=1.01 (±0.21)×10⁹ M^–1 andK ₂=0.95 (±0.61)×10⁷ M^–1. Likewise, the binding of [D-Ala², MePhe⁴, Gly(ol)⁵]enkephalin (DAGO) or [D-Ala², D-Leu⁵]-enkephalin (DADLE) alone was represented by a 2-site model. By adjusting the radioligand and receptor concentration or by the addition of blocking ligands, binding was represented by a 1-site model for DAGO,K=4.35 (±1.41)×10⁸ M^–1, and DADLE,K=2.44 (±0.08)×10⁸ M^–1.The abbreviations used are DADLE [D-Ala², D-Leu⁵]enkephalin - DAGO [D-Ala², MePhe⁴, Gly(ol)⁵]enkephalin - EKC ethylketocyclazocine - DYN dynorphin (1–17)     

Effect of exogenous cytokinins,auxins and adenine on cytokinin <Emphasis Type="Italic">N</Emphasis>-glucosylation and cytokinin oxidase/dehydrogenase activity in de-rooted radish seedlings

The role of cytokinin N-glucosylation and degradation by cytokinin oxidase/dehydrogenase (CKX, EC 1.5.99.12) in response to application of exogenous auxins (2,4-dichlorophenoxyacetic acid [2,4-D] and -naphthaleneacetic acid [NAA]) and cytokinins (N ⁶-benzyladenine [BA] and trans-zeatin [Z]) was investigated in de-rooted seedlings of Raphanus sativus L. cv. Rampouch. Both auxins applied for 24 h at 1 and 10 M concentration increased N-glucosylation of exogenously applied [³H]dihydrozeatin (DHZ) by up to 20%. The level of endogenous 7N-glucosides (of Z, isopentenyladenine [iP] and DHZ) was increased by 2,4-D and NAA at 10 M concentration by 28 and 23%, respectively, the level of Z being decreased by 90 and 59%, respectively. 2,4-D and NAA suppressed CKX activity ca. by half. Exogenous cytokinins Z and BA applied at 1 and 10 M concentration stimulated 7N-glucosylation of [³H]DHZ (by up to 40%). BA both at 1 and 10 M, increased the level of endogenous Z by up to 35% and that of 7N-glucosides by up to 27%. BA application also strongly stimulated CKX activity (by up to 180%). Feeding with 1 and 10 M Z resulted in ca. 100-fold and 2000-fold increase of Z level, respectively. The main metabolite, Z7G, was increased ca. 6-fold and 60-fold, respectively. Levels of Z 9-glucoside (Z9G), trans-zeatin riboside (ZR) and Z O-glucoside (ZOG) were elevated to lesser extent. As compared to BA, Z had only negligible effect on CKX activity. Adenine (1–500 M) was preferentially 7N-glucosylated inhibiting competitively 7N-glucosylation of [³H]DHZ. At high concentrations (100–500 M) it increased endogenous levels of active cytokinins, especially of Z, however, it had no effect on CKX activity. Cytokinin N-glucosylation proved to be involved in down-regulation of active cytokinins in response to auxin and in the re-establishment of cytokinin homeostasis following application of exogenous cytokinins.     

Production studies on protozoa

Summary In the river Saale and in the terrestrial moss Mnium cuspidatum Leyss. in 1974/75 the annual production of Testacea and loricate ciliated protozoa were investigated.The production was estimated in the Saale-Aufwuchs on a -meso ... oligosaprobic (Kaulsdorf, Thuringia, GDR) and on a -mesosaprobic (Rothenstein, Thuringia, GDR) area of the river. The mosses were investigated in a forest near Jena.The production was estimated on slides and in special productionchambers; the time of exposure was 2 weeks. Investigations concerned annual production of individuals and biomass, the ratio of annual production/standing crop (P/B), numbers of generations per year (G) and mortality (M%/d). In the mosses, the rainfall modified the production and dislocation of the protozoa.The values for production are: Aufwuchs Saale (-meso... oligosaprobic): 24·10⁶ i/m²·a (=1,0 g/m²·a=79·10³ i/m²·d); P/B: 12.6. Aufwuchs Saale (-mesosaprobic): 3.2·10⁶ i/m²·a (=0.35 g/m²·a=81·10³ i/m²·d); P/B: 34.9; G: 22; M: 5%/d. Moss: 145·10⁶ i/m²·a (=0.11 g/m²·a=40.6·10³ i/m²·d); P/B: 8.1; G: 16.5; M: 3.0%/d.     

The effect of a Variable Yield Function on the profitability of an integrated ABE fermentation product recovery system

A published process for the fermentative production and recovery of acetone-butanol-ethanol (ABE) has been modelled and analysed. Postulation of a Variable Yield Function has led to an unexpected Value Function. Given a desired ABE production range of 1.6×10⁶ kg per year to 32×10⁶ kg per year, and a typical fixed (or variable) cost term, , of $0.4 per kg ABE, the process has been shown to be unprofitable in the range 2×10⁶ kg per year to 18 × 10⁶ kg per year. Profitability is achieved at low production values (less than 2×10⁶ kg per year), and at high production values (greater than 18×10⁶ kg per year). Conversely, profitability is achieved for the comparable fixed yield case, for=$0.4 per kg ABE, for all production values, with the profitability increasing linearly with production.List of Symbols N ABE production, kg/yr,N ₁ andN ₂ for capacity 1 and 2, respectively - N _min Minimum value ofN. ABE production, kg/yr - P ABE concentration in a batch fermentation system, kg/l - p ABE price, $/kg - p ¹ p-, $/kg - S Amount of raw material, kg or kg/yr - S ¹ Substrate concentration in a batch fermentation system, kg/l - s Price of raw material, $/kg - V Value function, $/yr - V(N) Value function for production capacityN, $/yr - Y Continuous/fed batch fermentation yield, kg ABE/Kg whey permeate lactose.Y ₁ andY ₂ refer to yield for capacity 1 and 2, respectively - y Batch fermentation traditional yield, kg ABE/Kg whey permeate lactose - Average value ofY, kg ABE/Kg whey permeate lactose - Y _min Minimum Yield for continuous/fed batch fermentation, kg ABE/Kg whey permeate lactose - Y(N) Continuous/fed batch fermentation yield function, kg ABE/Kg whey permeate lactose Greek Letters Proportionality constant, yr/kg ABE - Proportionality constant, kg ABE/yr - Fixed costs (fermentation equipment, reverse osmosis and pervaporation equipment) + variable costs (energy, steam and labour + pervaporation membrane cost to remove ABE and recycle unused sugar), $/kg ABE - Exponent ofN in a generalized yield function We thank Tricia A. Doak (Department of Chemical Engineering, Vanderbilt University) for generating Figs. 2–5 on the computer.     

Colonization by Salmonella typhimurium and Shigella flexneri III of the gastrointestinal tract of mice treated with β-2-thienylalanine and streptomycin

Mice fed -2-thienylalanine (-2-T) by oesophageal tube were no more susceptible to gastrointestinal tract colonization by Salmonella typhimurium or Shigella flexneri III than control mice fed water. In both -2-T-fed and water-fed groups, the increasing dosage of S. typhimurium, in logarithmic increments to groups of mice, resulted in increasing numbers of these bacteria detectable on dilution plates from organ homogenates. Colonization by S. flexneri III only occurred at a dosage of 10⁸ bacteria for both groups. Pretreatment with 50 mg streptomycin allowed 10³ Salmonella or 10⁴ Shigella to colonize both -2-T- and water-fed groups.Coliforms, inhibited by -2-T under certain conditions in vitro, were found in equal numbers in both groups. No obvious differences were noted in either types of other bacteria detected or numbers recovered from the two groups.No gross behavioural changes were noted in mice fed -2-T and not challenged with pathogenic bacteria, and no pathological changes were noted in hepatic or splenic tissues. With increasing Salmonella dosage, collections of polymorpho-nuclear leucocytes, which were almost focal, and increased numbers of giant cells were noted in splenic red pulp areas, in both groups.This research was partially supported by grants from the National Children's Health Research Foundation (N.Z.), and the Auckland Medical Research Foundation.     

Increased poly-β-hydroxybutyrate (PHB) chain length by the modulation of PHA synthase activity in recombinant Escherichia coli

A second promoter (P1) was inserted to the PHA (poly--hydroxyalkanoate) operon (pSP2) of Esherichia coli DH5 with an optimal E. coli ribosome binding site and a trc strong promoter (pSJS1) to obtain poly--hydroxybutyrate (PHB) with long chain length. When the inducer, IPTG was added to the culture at 0.4 mM, the average molecular weight was 1.1 × 10⁶ Da. However, an even greater increase of the PHB average molecular weight to 2.5 × 10⁷ Da was observed without IPTG being added.