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Rhizobium leguminosarum bv. viciae contains a second fnr/fixK-like gene and an unusual fixL homologue (1996)

Patschkowski, Thomas ; Schlüter, Andreas ; Priefer, Ursula B.

Oxford BSL : Blackwell Science Ltd

Molecular microbiology 21 (1996), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: Genes of Rhizobium leguminosarum bv. viciae VF39 coding for the regulatory elements NifA, FixL and FixK were isolated, sequenced and genetically analysed. The fixK–fixL region is located upstream of the fixNOQP operon on the non-nodulation plasmid pRleVF39c. The deduced amino acid sequence of FixL revealed an unusual structure in that it contains a receiver module (homologous to the N-terminal domain of response regulators) fused to its transmitter domain. An oxygen-sensing haem-binding domain, found in other FixL proteins, is conserved in R. leguminosarum bv. viciae FixL. R. leguminosarum bv. viciae possesses a second fnr-like gene, designated fixK, whose encoded gene product is very similar to Rhizobium meliloti and Azorhizobium caulinodans FixK. Individual R. leguminosarum bv. viciae fixK and fixL insertion mutants displayed a Fix+ phenotype. A reduced nitrogen-fixation activity was found for a R. leguminosarum bv. viciae fnrN-deletion mutant, whereas no nitrogen-fixation activity was detectable for a fixK/fnrN double mutant. The R. leguminosarum bv. viciae nifA gene is expressed independently of FixL and FixK under aerobic and microaerobic conditions, whereas fixL gene expression is induced under microaerobiosis. Another orf was identified downstream of fixK–fixL and encodes a product which has homology to pseudoazurins from different species. Mutation of this azu gene showed that it is dispensable for nitrogen fixation.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2958.1996.6321348.x

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A theory of rules for enumerated classes of functions (1995)

Schlüter, Andreas

Springer

Archive for mathematical logic 34 (1995), S. 47-63

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ISSN: 1432-0665

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract We define an applicative theoryCL 2 similar to combinatory logic which can be interpreted in classes of functions possessing an enumerating function. In contrast to the models of classical combinatory logic, it is not necessarily assumed that the enumerating function itself belongs to that function class. Thereby we get a variety of possible models including e. g. the classes of primitive recursive, recursive, elementary, polynomial-time comptable ofɛ 0-recursive functions. We show that inCL 2 a major part of the metatheory of enumerated classes of functions can be developed. Namely, a kind of λ-abstraction can be defined and abstract versions of theS n m - and (Primitive) Recursion Theorems are proved. Thereby, a closer analysis of the phenomenon of the different recursion theorems is achieved. A theory closely related toCL 2 can be used to replace the applicative part of Feferman's theories for explicit mathematics. So this work can be seen as an answer to Feferman's question to formulate a theory for explicit mathematics in which operations can be interpreted as primitive recursive or even more feasible ones. Finally it is shown that the proof-theoretical strength of various theoreies for explicit mathematics is preserved when replacing the applicative part of the theories by our theory together with an operation for primitive recursion.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01269876

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Electronic Resource

A theory of rules for enumerated classes of functions (1995)

Schlüter, Andreas

Springer

Archive for mathematical logic 34 (1995), S. 47-63

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Details

ISSN: 1432-0665

Source: Springer Online Journal Archives 1860-2000

Topics: Mathematics

Notes: Abstract. We define an applicative theory $\mbox{{\boldmath\bf CL$_2$}} similar to combinatory logic which can be interpreted in classes of functions possessing an enumerating function. In contrast to the models of classical combinatory logic, it is not necessarily assumed that the enumerating function itself belongs to that function class. Thereby we get a variety of possible models including e. g. the classes of primitive recursive, recursive, elementary, polynomial-time computable or $\varepsilon_0$ -recursive functions. We show that in $\mbox{{\boldmath\bf CL$_2$}}$ a major part of the metatheory of enumerated classes of functions can be developed. Namely, a kind of $\lambda$ -abstraction can be defined and abstract versions of the $S^m_n$ - and (Primitive) Recursion Theorems are proved. Thereby, a closer analysis of the phenomenon of the different recursion theorems is achieved. A theory closely related to $\mbox{{\boldmath\bf CL$_2$}}$ can be used to replace the applicative part of Feferman's theories for explicit mathematics. So this work can be seen as an answer to Feferman's question to formulate a theory for explicit mathematics in which operations can be interpreted as primitive recursive or even more feasible ones. Finally it is shown that the proof-theoretical strength of various theories for explicit mathematics is preserved when replacing the applicative part of the theories by our theory together with an operation for primitive recursion.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01269876

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