Synthesis of Rhodobacter sphaeroides cytochrome c2 in Escherichia coli

The cytochrome c2 structural gene, cycA, from Rhodobacter sphaeroides was expressed in Escherichia coli. CycA-specific mRNA was detected in E. coli both under aerobic and anaerobic conditions with trimethylamine-N-oxide as electron acceptor. However mature holocytochrome c2 was only detected in anaerobically-grown cells. The mature form of cytochrome c2 (Mr = 12,500) was secreted into the periplasm of E. coli suggesting that the signal polypeptide was processed. The cytochrome c2 synthesized in E. coli exhibited absorbance maxima in the reduced form at 550 nm (alpha-band) and 521 nm (beta-band) and contained covalently attached haem c. The results indicate that a foreign c-type cytochrome can be secreted and assembled in E. coli under anaerobic conditions.     

Synthesis of the Rhodopseudomonas viridis holo-cytochrome c2 in Paracoccus denitrificans

Abstract The gene encoding the Rhodopseudomonas viridis cytochrome c ₂ (cycA) has been introduced on a broad host range vector into Paracoccus denitrificans , leading to high-level expression of the holo-cytochrome with the heme moiety covalently attached to the apoprotein. The cytochrome was demonstrated to reside in the periplasmic space of the host cell. In contrast to R. viridis , aerobic rather than anaerobic growth conditions led to higher production levels of the holo-cytochrome in P. denitrificans . This heterologous expression system provides a suitable genetic background for the functional expression and mutagenesis of polypeptides involved in bacterial photosynthesis, offering the possibility of detailed structural and functional investigation.     

Role of Bradyrhizobium japonicum cytochrome c550 in nitrite and nitrate respiration

Bradyrhizobium japonicum cytochrome c ₅₅₀, encoded by cycA , has been previously suggested to play a role in denitrification, the respiratory reduction of nitrate to dinitrogen. However, the exact role of this cytochrome in the denitrification process is unknown. This study shows that cytochrome c ₅₅₀ is involved in electron transfer to the copper-containing nitrite reductase of B. japonicum , as revealed by the inability of a cycA mutant strain to consume nitrite and, consequently, to grow under denitrifying conditions with nitrite as the electron acceptor. Mutation of cycA had no apparent effect on methylviologen-dependent nitrite reductase activity. However, succinate-dependent nitrite reduction was largely inhibited, suggesting that c ₅₅₀ is the in vivo electron donor to copper-containing nitrite reductase. In addition, this study demonstrates that a cytochrome c ₅₅₀ mutation has a negative effect on expression of the periplasmic nitrate reductase. This phenotype can be rescued by extending the growth period of the cells. A model is proposed whereby a mutation in cycA reduces expression of the cbb ₃-type oxidase, affecting oxygen consumption rate by the cells and consequently preventing maximal expression of the periplasmic nitrate reductase during the first days of the growth period.     

DIE WIRKUNG VON PHYTOHORMONEN AUF KEIMUNG UND ENTWICKLUNG VON FARNPROTHALLIEN IV. DIE WIRKUNG VON UNTERSCHIEDLICHEN GIBBERELLINE UND VON ALLO-GIBBERINSAURE AUF DIE AUSLOSUNG DER ANTHERIDIENBILDUNG BEI ANEMIA PHYLLITIDIS L. UND EINIGEN POLYPODIACEEN

The relative activities of seven gibberellins have been testedin their ability to induce antheridia in prothallia of Anemiaphyllitidis. The spectrum of activities differs from the spectradescribed for other gibberellin reactions. Allogibberic acidproved to be highly active in the Anemia test. Additionallyit causes a change in the polarity of the germinating spore.Under the influence of this compound the primary rhizoid istransformed into an additional chloronema. In high concentrationsof allogibberic acid more than 80% of the prothallia developinto those "twins". Out of the polypodiaceous ferns only fewspecies respond to gibberellin application. The relations between chemical structure and activity of differentgibberellins are discussed. (Received January 17, 1966; )     

Cloning, sequencing and mutational analysis of the cytochrome c552 gene (cycB) from Bradyrhizobium japonicum strain 110

We report the cloning and nucleotide sequence analysis of the cytochrome c552 gene (cycB) of Bradyrhizobium japonicum strain 110. The gene was identified with help of an oligonucleotide that was designed on the basis of the amino acid sequence determined for purified cytochrome c552 of B. japonicum strain CC705. The cycB gene product has an N-terminal 23-amino acid signal peptide that is missing in the mature cytochrome c552 protein. A B. japonicum cycB insertion mutant was constructed which had no observable phenotypic defects in denitrification and symbiotic nitrogen fixation. Thus, the function of c552 remains unknown.     

BILDUNG UND GEBRAUCH VON BEGRIFFEN IN DER PALÄOÖKOLOGIE

During the past 20 years, palaeoecology has established itself as a concept in palaeontology and geology. As in other interdisciplinary sciences, the interchange of methods and terminology between the branches involved has led to changes in the meaning of the terms, and changes or confusion in the corresponding scientific concepts. This calls for stricter adherence to the original definition of the terms in many cases and for their redefinition in others. Starting with a critical review of the scientific and methodological range of palaeoecology, this paper presents a reconsideration of its basic concepts, with proposals concerning the conservation or redefinition of terms and with special regard to terms coined in German literature. It is desirable that similar revisions be undertaken in other language areas in order to attain a stricter, internationalized terminology, preferably substantiated in a dictionary.