Showing papers by "University of Konstanz published in 1993"

Ferrous iron oxidation by anoxygenic phototrophic bacteria

Abstract: NATURAL oxidation of ferrous to ferric iron by bacteria such as Thiobacillus ferrooxidans or Gallionella ferruginea1, or by chemical oxidation2,3 has previously been thought always to involve molecular oxygen as the electron acceptor. Anoxic photochemical reactions4–6 or a photobiological process involving two photosystems7–9 have also been discussed as mechanisms of ferrous iron oxidation. The knowledge of such processes has implications that bear on our understanding of the origin of Precambrian banded iron formations10–14. The reducing power of ferrous iron increases dramatically at pH values higher than 2–3 owing to the formation of ferric hydroxy and oxyhydroxy compounds1,2,15 (Fig. 1). The standard redox potential of Fe3+/Fe2+ (E0 = +0.77 V) is relevant only under acidic conditions. At pH 7.0, the couples Fe(OH)3/Fe2+ (E′0 = -0.236V) or Fe(OH)3 + HCO−3FeCO3 (E′0 = +0.200 V) prevail, matching redox potentials measured in natural sediments9,16,17. It should thus be possible for Fe(n) around pH 7.0 to function as an electron donor for anoxygenic photosynthesis. The midpoint potential of the reaction centre in purple bacteria is around +0.45 V (ref. 18). Here we describe purple, non-sulphur bacteria that can indeed oxidize colourless Fe(u) to brown Fe(in) and reduce CO2 to cell material, implying that oxygen-independent biological iron oxidation was possible before the evolution of oxygenic photosynthesis.

The histochemical profiles of fast fiber types IIB, IID, and IIA in skeletal muscles of mouse, rat, and rabbit.:

Abstract: This study characterized histochemically three fast fiber types (IIB, IID, IIA) in skeletal muscles of mouse, rat, and rabbit, with special reference to fiber types IIB and IID The results are complemented by biochemical analyses of myosin heavy chain composition in these muscles Fiber type delineation is based on various methods for mATPase staining with pre-incubations and assays under different conditions In rat and mouse, IIB and IID fibers can be best distinguished according to their different mATPase stabilities towards formaldehyde and alkaline pH In rabbit, the method of Matoba and Gollnick using acid pre-incubation provided best and most reproducible results In addition to their different mATPase stabilities, the three fast fiber types differ with regard to their oxidative capacities and cross-sectional fiber areas in the three species In general, Type IIB fibers are the largest and least oxidative, Type IIA fibers the smallest and most oxidative, and Type IID fibers intermediate In rabbit, Type IID fibers are the predominant fast fiber population in extensor digitorum longus, psoas, and tibialis anterior muscles As judged from histochemistry, these muscles of rabbit do not contain pure Type IIB fibers This is in accordance with biochemical results that show the HCIId to form the majority of the myosin heavy chain complement expressed in these muscles On the other hand, IIB fibers are numerous in rabbit adductor magnus, gastrocnemius, and vastus lateralis muscles Similarly, appreciable amounts of myosin heavy chain HCIIb are found in the three latter muscles of rabbit

Disagreement and concession in disputes: On the context sensitivity of preference structures

Abstract: This article discusses disagreement sequences in German and Anglo-American disputes. It is argued that the context sensitivity of preference for agreement with assessments that Pomerantz 1984 found in her data has to be elaborated and extended. My findings suggest that the preference structure can change once a dissent-turn-sequence has been displayed; in this case, opponents are expected to defend their positions. The reduction of reluctance markers creates a new preference structure which itself has to be accomplished by all participants. Concessions, defined as a participant's agreeing to the central issue after his or her prior disagreement, show reluctance markers which are viewed as indicators of the dispreferred status in other types of talk. Concessions can be distinguished from partially agreeing presequences of dissent turns. Speakers move toward concessions stepwise. Unprepared position shifts can be regarded by the interlocutors as the inability to defend an opinion. Concessions, being an interactional achievement, reframe the dispute. (Conversation analysis, dispute, context studies, expectation management)

Ocular artifacts in EEG and event-related potentials. I: Scalp topography.

Abstract: The ocular artifacts that contaminate the EEG derive from the potential difference between the cornea and the fundus of the eye. This corneofundal or corneoretinal potential can be considered as an equivalent dipole with its positive pole directed toward the cornea. The cornea shows a steady DC potential of approximately +13 mV relative to the forehead. Blink potentials are caused by the eyelids sliding down over the positively charged cornea. The artifacts from eye-movements result from changes in orientation of the corneo-fundal potential. The scalp-distribution of the ocular artifacts can be described in terms of propagation factors--the fraction of the EOG signal at periocular electrodes that is recorded at a particular scalp location. These factors vary with the location of the scalp electrode. Propagation factors for blinks and upward eye-movements are significantly different.

Cohomological methods in transformation groups

Abstract: Preface 1. Equivalent cohomology of G-CW-complexes and the Borel construction 2. Summary of some aspects of rational homotopy theory 3. Localisation 4. General results on torus and p-torus actions 5. Actions on Poincare duality spaces Appendices References Indexes.

p53-catalyzed annealing of complementary single-stranded nucleic acids.

Abstract: p53 has been reported to inhibit the DNA helicase intrinsic to simian virus 40 large tumor antigen (T antigen). We found that inhibition is not restricted to T antigen, but also affects several other DNA and RNA helicases. Complexing of the helicases by the p53 protein as a possible inactivation mechanism could be excluded. Instead, the anti-helicase activity can be explained by our finding that p53 binds with high affinity to single-stranded nucleic acids and has a strong DNA.DNA and RNA.RNA annealing activity. We could also show that p53 is able to alter the secondary structure of RNA and/or to influence dynamic RNA-RNA interactions. These results, and the fact that the affinity of p53 to RNA is about one order of magnitude higher than to single-stranded DNA, imply an RNA-specific function of p53 in vivo.

Osmotic regulation of rpoS-dependent genes in Escherichia coli.

Abstract: The rpoS gene, which encodes a putative alternative sigma factor (sigma S), is essential for the expression of a variety of stationary-phase-induced genes as well as for stationary-phase-specific multiple-stress resistance. As previously shown for the otsA and otsB genes (R. Hengge-Aronis, W. Klein, R. Lange, M. Rimmele, and W. Boos, J. Bacteriol. 173:7918-7924, 1991), we demonstrate here that additional rpoS-controlled genes (bolA, csi-5) as well as at least 18 proteins on two-dimensional O'Farrell gels could be induced in growing cells by osmotic upshift via an rpoS-dependent mechanism. Also, rpoS-dependent thermotolerance and resistance against hydrogen peroxide could be osmotically stimulated. In contrast, the expression of glgS, while exhibiting strong stationary-phase induction, was only weakly increased by elevated osmolarity, and several rpoS-dependent proteins previously identified on two-dimensional gels were not osmotically induced. During osmotic induction of rpoS-dependent genes, rpoS transcription and the level of sigma S remained unchanged. We conclude that osmotically regulated genes represent a subfamily within the rpoS regulon that requires differential regulation in addition to that provided by sigma S.

Infection structures of fungal plant pathogens – a cytological and physiological evaluation

Abstract: SUMMARY Many fungi differentiate specific infection structures in order to infect the host plant. The spore attaches to the host surface, the cuticle, and the germ tube may recognize suitable penetration sites, over which an appressorium is formed. Additional wall layers in appressoria of many fungi suggest that this structure supports increasing pressure during the penetration process. During appressorium formation, synthesis of polymer-degrading enzymes is often initiated. Cutinases, cellulases and pectin-degrading enzymes can be formed in a developmentally controlled or adaptive, i.e. substrate-dependent, fashion. The penetration hypha develops below the appressorium. This hypha has a new wall structure and exhibits features which serve to breach the plant cell wall. However, at present it is not clear whether penetration hyphae arising from appressoria are more efficient in penetration or induce less damage than hyphae which penetrate without detectable special adaptations. The infection hypha differentiates within the host. During differentiation a characteristic set of enzymes is synthesized to enable successful establishment of the host-pathogen relationship. If, as in most cases, multiple forms of cell wall-degrading enzymes are formed by the pathogen, mutagenesis or deletion of a gene encoding one of these enzymes very often has no effect on pathogenicity or even virulence. Proof is missing very often that an enzyme is needed at the right time and at the right site of infection. Events occurring during differentiation of fungal infection structures are reviewed with special emphasis on Magnaporthe grisea, Colletotrichum spp., and rust fungi, and common features which may be of importance to the success of infection are discussed.

Pigment-dispersing hormone-immunoreactive neurons in the nervous system of wild-type Drosophila melanogaster and of several mutants with altered circadian rhythmicity

Abstract: Antisera against the crustacean pigment-dispersing hormone (p-PDH) were used in immunocytochemical preparations to investigate the anatomy of PDH-immunorea ctive neu­ rons in the nervous system of wild-type Drosophila melanogaster and in that of several brain mutants of this species, some of which express altered circadian rhythmicity. In the wild-type and in all rhythmic mutants (small optic lobes, sine oculis, small optic lobes;sine oculis), eight cell bodies at the anterior base of the medulla (PDFMe neurons) exhibit intense PDH-like immunoreactivity. Four of the eight somata are large and four are smaller. The four large PDFMe neurons have wide tangential arborizations in the medulla and send axons via the posterior optic tract to the contralateral medulla. Fibers from the four small PDFMe neurons ramify in the median protocerebrum dorsal to the calyces of the mushroom bodies. Their terminals are adjacent to other PDH-immunoreactive somata (PDFCa neurons) which send axons via the median bundle into the tritocerebrum. The results suggest a possible involvement of the PDFMe neurons in the circadian pacemaking system of Drosophila. The location and size of the PDFMe neurons are identical with those of neurons containing the period protein which is essential for circadian rhythmicity. Changes in the arborizations of the PDFMe neurons in small optic lobes;sine oculis mutants are suited to explain the splitting in the locomotor rhythm of these flies. In the arrhythmic mutant, disconnected, the PDFMe neurons are absent. The arrhythmic mutant per0, however, shows normal PDH immunoreactivity and therefore, does not prevent the expression of PDH-like peptides in these neurons. 1993 Wiley-Lias, Inc.

Ocular artifacts in recording EEGs and event-related potentials II: Source dipoles and source components

Abstract: The source dipoles for blinks point radially whereas the source dipoles for saccades point tangentially, in the direction of the eye movement. This indicates that blink potentials are not generated by eye movements but by the eyelid sliding down over the positively charged cornea. Dipole source dipole analysis shows that the “rider artifact” at the onset of upward and lateral saccades is caused by the eyelid as it lags a little behind the eyes at the beginning of the movement. Dipole source analysis allows both the EEG and the EOG to be modeled simultaneously and EOG generators to be distinguished from nearby EEG generators. Ocular source components can be calculated from a principal component analysis of EEG and EOG recordings during blinks and saccades. The effectiveness of propagation factors, source dipoles and source components in removing ocular artifacts from EEG samples was assessed. The most effective correction procedure uses source components.

Muon spin rotation study of the correlation between Tc and ns/m* in overdoped Tl2Ba2CuO6+ delta.

Abstract: The muon spin depolarization rate \ensuremath{\sigma} was measured in overdoped ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{3}$${\mathrm{CuO}}_{6+\mathrm{\ensuremath{\delta}}}$. \ensuremath{\sigma}(T\ensuremath{\rightarrow}0) was found to decrease proportional to the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ as doping \ensuremath{\delta} is increased. In the framework of the clean-limit London model, \ensuremath{\sigma}(0)\ensuremath{\sim}${\ensuremath{\lambda}}^{\mathrm{\ensuremath{-}}2}$\ensuremath{\sim}${\mathit{n}}_{\mathit{s}}$/${\mathit{m}}^{\mathrm{*}}$, this implies that the depression of ${\mathit{T}}_{\mathit{c}}$ by overdoping is associated with a decrease of the superconducting condensate density ${\mathit{n}}_{\mathit{s}}$ in spite of the increasing normal-state carrier density. This can be largely accounted for in terms of strong pair breaking, which depresses both the condensate density and ${\mathit{T}}_{\mathit{c}}$ with increased doping.

Influence of oxygen on sulfate reduction and growth of sulfate-reducing bacteria

Abstract: The ambivalent relations of sulfate-reducing bacteria to molecular O2 have been studied with ten freshwater and marine strains. Generally, O2 was reduced prior to sulfur compounds and suppressed the reduction of sulfate, sulfite or thiosulfate to sulfide. Three strains slowly formed sulfide at O2 concentrations of below 15 μM (6% air saturation). In homogeneously aerated cultures, two out of seven strains tested, Desulfovibrio desulfuricans and Desulfobacterium autotrophicum, revealed weak growth with O2 as electron acceptor (up to one doubling of protein). However, O2 was concomitantly toxic. Depending on its concentration cell viability and motility decreased with time. In artificial oxygen-sulfide gradients with sulfide-containing agar medium and also in sulfide-free agar medium under an oxygen-containing gas phase, sulfate reducers grew in bands close to the oxic/anoxic interface. The specific O2 tolerance and respiration capacity of different strains led to characteristically stratified gradients. The maximum O2 concentration at the surface of a bacterial band (determined by means of microelectrodes) was 9 μM. The specific rates of O2 uptake per cell were in the same order of magnitude as the sulfate reduction rates in pure cultures. The bacteria stabilized the gradients, which were rapidly oxidized in the absence of cells or after killing the cells by formaldehyde. The motile strain Desulfovibrio desulfuricans CSN slowly migrated in the gradients in response to changing O2 concentrations in the gas phase.

Functional expression of the Erwinia uredovora carotenoid biosynthesis gene crtl in transgenic plants showing an increase of beta-carotene biosynthesis activity and resistance to the bleaching herbicide norflurazon.

Abstract: Among the enzymes involved in carotenoid biosynthesis, phytoene desaturase is considered to be a rate-limiting enzyme in this pathway and is also the target of many bleaching herbicides. This enzyme shows diversity concerning its function and amino acid homology among various organisms. The phytoene desaturase gene crtl of Erwinia uredovora was expressed, the 5'-region of which was fused to the sequence for the transit peptide of a pea Rubisco small subunit, in tobacco plants under the control of the CaMV 35S promoter. This chimeric gene product was targeted into chloroplasts and processed in the transgenic plants. The production and processing of the corresponding protein could be demonstrated by Western blotting. Immunogold localization showed that the location of the gene product Crtl was preferentially in the thylakoids. A radioactive labeling study using the leaves demonstrated enhanced activity for the synthesis of beta-carotene. In addition, the transgenic tobacco acquired elevated resistance to the bleaching herbicide norflurazon.

Biomass and production of heterotrophic bacterioplankton in the oceanic subarctic Pacific

Abstract: As part of the Subarctic Pacific Ecosystem Research (SUPER) program, we measured the abundance and biomass production of heterotrophic bacterioplankton in the subarctic Pacific and compared these parameters with those of phytoplankton during four cruises in 1987 and 1988. Bacterial biomass was about equal to phytoplankton biomass during all cruises. Based on rates of bacterial biomass production and assuming a growth efficiency of 50%, we estimate that heterotrophic bacteria consumed 10% (June 1987) to 24% (August 1988) of primary production in the euphotic zone. These percentages are low compared with other aquatic ecosystems, apparently due to low bacterial growth rates ( −1 ) iin the subarctic Pacific. In contrast, phytoplankton growth rates were much higher (0.1–8.8 day −1 ). Bacterial growth rates were limited by the supply of dissolved organic matter and temperature. Even with these low growth rates, however, bacterial biomass and rates of biomass production increased by 2–5-fold in May and August 1988, changes that were not obviously related to corresponding changes in phytoplankton biomass nor primary production. Heterotrophic bacterioplankton constitutes a large reservoir of carbon and nitrogen that needs to be considered in modelling ecosystem dynamics of the subarctic Pacific.

Dynamical criterion for freezing of colloidal liquids.

Abstract: A simple dynamical criterion for crystallization of a colloidal fluid which undergoes Brownian motion is proposed, similar in spirit to the classic Lindemann melting rule. It states that the ratio of the long-time and short-time self-diffusion coefficients is a universal number very close to 0.1 along the freezing line. This phenomenological crystallization rule is confirmed both by Brownian dynamics simulations of a Yukawa liquid and by forced Rayleigh scattering experiments on charge-stabilized colloidal suspensions.

Synthesis of the Escherichia coli K-12 nucleoid-associated DNA-binding protein H-NS is subjected to growth-phase control and autoregulation.

Abstract: Mutations in the structural gene (hns) for the Escherichia coli nucleoid-associated DNA-binding protein H-NS cause highly pleiotropic effects on gene expression, site-specific recombination, transposition of phage Mu, the stability of the genetic material and the topological state of the DNA. We have investigated the regulation of hns expression and found that hns transcription is subjected to stationary phase induction and negative autoregulation. A set of hns-lacZ protein and operon fusions was constructed in vitro and integrated in single copy into the attB site of the bacterial genome. Quantification of beta-galactosidase activity along the bacterial growth curve showed that hns expression increases approximately 10-fold in stationary phase compared with exponentially growing cells. Immunological detection of the H-NS protein in growing and stationary phase cells supported the genetic data and showed that H-NS synthesis varies with growth phase. In addition, primer extension experiments demonstrated that the amount of hns mRNA is elevated in stationary phase cultures and that hns transcription is directed by a unique promoter functioning in both log and stationary phase. Disruption of the hns gene by an insertion mutation led to the derepression (approximately fourfold) of the expression of an hns-lacZ operon fusion integrated at the attB site, showing that hns transcription is subjected to negative regulation by its own gene product. Autoregulation of hns expression is particularly pronounced in log phase. Both stationary phase control and autoregulation of hns transcription are associated with a 130 bp fragment that contains the hns promoter. In order to study the interaction of H-NS with its own regulatory region, we developed an efficient overproduction procedure and a simple purification scheme for H-NS. DNA gel retardation assays showed that the H-NS protein can preferentially interact with a restriction fragment carrying the hns promoter. This restriction fragment showed features of curved DNA as judged by two-dimensional polyacrylamide gel electrophoresis performed at 4 degrees C and 60 degrees C.

English speech rhythm

Abstract: This monograph reconsiders the question of speech isochrony, the regular recurrence of (stressed) syllables in time, from an empirical point of view It proposes a methodology for discovering isochrony auditorily in speech and for verifying it instrumentally in the acoustic laboratory In a small-scale study of an English conversational extract, the gestalt -like rhythmic structures which isochrony creates are shown to have a hierarchical organization Then in a large-scale study of a corpus of British and American radio phone-in programs and family table conversations, the function of speech rhythm at turn transitions is investigated It is argued that speech rhythm serves as a metric for the timing of turn transitions in casual English conversation The articular rhythmic configuration of a transition can be said to contextualize the next turn as, generally speaking, affiliative or disaffiliative with the prior turn The empirical investigation suggests that speech rhythm patterns at turn transitions in everyday English conversation are not random occurrences or the result of a social-psychological adaptation process but are contextualization cues which figure systematically in the creation and interpretation of linguistic meaning in communication

Nonlinear optics of Bessel beams

Abstract: We investigated the frequency-doubling properties of light beams whose transverse profile is given by the zero-order Bessel function ${\mathit{J}}_{0}$(r), Bessel beams. Phase-matched second-harmonic generation in a KDP crystal was observed at angles usually not suited for phase matching. It is thereby demonstrated that under certain circumstances, Bessel beams can be viewed as light beams with tunable wavelength. A variety of applications in the field of nonlinear optics is expected.

Fast myosin heavy chain diversity in skeletal muscles of the rabbit: heavy chain IId, not IIb predominates

Abstract: The myosin heavy chain (HC) composition of various rabbit muscles was analysed at both the mRNA and the protein level. S1-nuclease mapping was performed with a cDNA probe specific for myosin HCIIa, yielding a fully protected sequence for HCIIa, a partially protected sequence for HCIIb, and an additional signal putatively assigned to HCIId. At the protein level, three fast myosin HC isoforms, HCIIa, HCIIb and HCIId, were separated by gradient PAGE. The results obtained at the protein level were in agreement with the findings at the mRNA level. The expression of appreciable amounts of myosin HCIIb, the predominating isoform of fast-twitch muscles in rat and mouse, was restricted in the rabbit to only a few muscles, i.e. adductor magnus, gastrocnemius, latissimus dorsi and vastus lateralis. Typical fast-twitch muscles such as extensor digitorum longus, tibialis anterior and psoas contained only minute amounts of HCIIb. The HCIId isoform, demonstrated in the present study for the first time in rabbit, is the predominating fast myosin HC isoform in this species. Electrophoretic analyses of myosin HC in histochemically defined single fibers confirmed the lack of fibers expressing only HCIIb in tibialis anterior, whereas such fibers were found in the adductor magnus. In addition to fiber types IIB, IID, and IIA expressing HCIIb HCIId, and HCIIa, respectively, an appreciable amount of hybrid fibers coexpressing two HC isoforms at various ratios were found: HCIIb > HCIId; HCIId > HCIIb; HCIId > HCIIa; HCIIa > HCIId; HCIIa > HCI; HCI > HCIIa. This fiber-type spectrum indicates possible fiber-type transitions in the order IIB ↫ IIBD ↫ IIDB ↫ IID ↫ IIDA ↫ IIAD ↫ IIA ↫ IIC ↫ IC ↫ I.

Temperature dependence of nitrification, denitrification, and turnover of nitric oxide in different soils

Abstract: The temperature dependence of the NO production rate and the NO consumption rate constant was measured in an Egyptian soil, a soil from the Bavarian Forest, and a soil from the Donau valley, together with the temperature dependence of the potential rates of ammonium oxidation, nitrite oxidation, and denitrification, and the temperature dependence of the growth of NH inf4 sup+ -oxidizing, NO inf2 sup- -oxidizing, and NO inf3 sup- -reducing bacteria in most probable number assays. In the acidic Bavarian Forest soil, NO production was only stimulated by the addition of NO inf3 sup- but not NH inf4 sup+ . However, NO production showed no temperature optimum, indicating that it was due to chemical processes. Most probable numbers and potential activities of nitrifiers were very low. NO consumption, in contrast, showed a temperature optimum at 25°C, demonstrating that consumption and production of NO were regulated individually by the soil temperature. In the neutral, subtropical Egyptian soil, NO production was stimulated only by the addition of NH inf4 sup+ but not NO inf3 sup- . All activities and most probable numbers showed a temperature optimum at 25° or 30°C and exhibited apparent activation energies between 61 and 202 kJ mol-1. However, a few nitrifiers and denitrifiers were also able to grow at 8° or 50°C. Similar temperature characteristics were observed in the Donau valley soil, although it originated from a temperate region. In this soil NO production was stimulated by the addition of NH inf4 sup+ or of NO inf3 sup- . Both NO production and consumption were stimulated by drying and rewetting.

Nucleation and growth of a flux instability in superconducting YBa2Cu3O7-x films.

Abstract: Using a high speed magneto-optic technique we have investigated the dynamics of a new flux instability in thin superconducting ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{x}}$ films exposed to an external magnetic field of several ${10}^{\mathrm{\ensuremath{-}}2}$ T. The instability was nucleated by a 5 ns laser pulse, which heated a small spot of the sample in a region of high shielding currents. Two subsequent regimes in the development of the instability are discovered, which give rise to strikingly different flux distributions. The formation of flux branches, which are characteristic for the second stage, occurs on a time scale of a hundred nanoseconds.

The continuum of pure and hybrid myosin heavy chain-based fibre types in rat skeletal muscle

Abstract: The myosin heavy chain (MHC)-based fibre composition of adult rat adductor magnus (AM) and tibialis anterior (TA) muscles was investigated using single fibre analysis. Microelectrophoresis performed on single fibre fragments demonstrated a predominance of pure fast MHC-based fibre types (expressing only one fast MHC). Most of the fibres analysed from both the AM (72%) and TA (50%) were pure type IIB (expressing only MHCIId). Pure type IID fibres (expressing only MHCIId) were also abundant in AM (20%) and TA (18%). In addition, hybrid fibres coexpressing MHCIIb and MHCIId in varying proportions (fibre types IIBD and IIDB) were found, as well as fibres coexpressing MHCIId and MHCIIa with a predominance of MHCIId (type IIDA) and some C fibres (coexpressing MHCI and MHCIIa in varying proportions). Considered altogether, these data reflect the dynamic nature of adult skeletal muscle fibres and indicate a continuum of MHC-based fibre types in normal rat muscle with transitions in the order IIB IIBD IIDB IID IIDA IIAD II A IIC IC I.

Identification and characterization of stationary phase inducible genes in Escherichia coli

Abstract: During transition into stationary phase a large set of proteins is induced in Escherichia coli. Only a minority of the corresponding genes has been identified so far. Using the lambda placMu system and a plate screen for carbon starvation-induced fusion activity, a series of chromosomal lacZ fusions (csi::lacZ) was isolated. In complex medium these fusions were induced either during late exponential phase or during entry into stationary phase. csi::lacZ expression in minimal media in response to starvation for carbon, nitrogen and phosphate sources and the roles of global regulators such as the alternative sigma factor sigma s (encoded by rpoS), cAMP/CRP and the relA gene product were investigated. The results show that almost every fusion exhibits its own characteristic pattern of expression, suggesting a complex control of stationary phase-inducible genes that involves various combinations of regulatory mechanisms for different genes. All fusions were mapped to the E. coli chromosome. Using fine mapping by Southern hybridization, cloning, sequencing and/or phenotypic analysis, csi-5, csi-17, and csi-18 could be localized in osmY (encoding a periplasmic protein), glpD (aerobic glycerol-3-phosphate dehydrogenase) and glgA (glycogen synthase), respectively. The other fusions seem to specify novel genes now designated csiA through to csiF. csi-17(glpD)::lacZ was shown to produce its own glucose-starvation induction, thus illustrating the intricacies of gene-fusion technology when applied to the study of gene regulation.

Complex transcriptional control of the sigma s-dependent stationary-phase-induced and osmotically regulated osmY (csi-5) gene suggests novel roles for Lrp, cyclic AMP (cAMP) receptor protein-cAMP complex, and integration host factor in the stationary-phase response of Escherichia coli.

Abstract: osmY (csi-5) is a representative of a large group of sigma s-dependent genes in Escherichia coli that exhibit both stationary-phase induction and osmotic regulation. A chromosomal transcriptional lacZ fusion (csi-5::lacZ) was used to study the regulation of osmY. We show here that in addition to sigma s, the global regulators Lrp, cyclic AMP (cAMP) receptor protein-cAMP complex (cAMP-CRP), and integration host factor (IHF) are involved in the control of osmY. All three regulators negatively modulate the expression of osmY, and they act independently from sigma s. Stationary-phase induction of osmY in minimal medium can be explained by stimulation by sigma s combined with a relief of Lrp repression. Stationary-phase induction of osmY in rich medium is mediated by the combined action of sigma s, Lrp, cAMP-CRP, and IHF, with the latter three proteins acting as transition state regulators. The transcriptional start site of osmY was determined and revealed an mRNA with an unusual long nontranslated leader of 244 nucleotides. The regulatory region is characterized by a sigma 70-like -10 promoter region and contains potential binding sites for Lrp, CRP, and IHF. Whereas sigma s, Lrp, CRP, and IHF are clearly involved in stationary-phase induction, none of these regulators is essential for osmotic regulation of osmY.