Genomic plasticity and catabolic potential of Pseudomonas cepacia

The primary goal of this project was to gain information about the size and organization of the genome of Burkholderia cepacia (formerly Pseudomonas cepacia), a microbe which continues to attract attention because of its extraordinary degradative abilities and potential as an agent of bioremediation. This bacterium is no longer considered to be a member of genus Pseudomonas nor does it belong in the gamma-subclass of the proteobacteria, in which the authentic pseudomonads are grouped. It belongs in the less well characterized beta-subclass of the proteobacteria. Technology for manipulation of large DNA fragments developed by Cantor was used to demonstrate that chromosomal multiplicity, a characteristic yet to be observed in a gamma-subclass bacterium, is common among B. cepacia strains. A derivative of Tn5 suitable for determining the chromosomal locations of various B. cepacia genes was also constructed

Genomic plasticity and catabolic potential of Pseudomonas cepacia

The primary goal of this project was to gain information about the size and organization of the genome of Burkholderia cepacia (formerly Pseudomonas cepacia), a microbe which continues to attract attention because of its extraordinary degradative abilities and potential as an agent of bioremediation. This bacterium is no longer considered to be a member of genus Pseudomonas nor does it belong in the gamma-subclass of the proteobacteria, in which the authentic pseudomonads are grouped. It belongs in the less well characterized beta-subclass of the proteobacteria. Technology for manipulation of large DNA fragments developed by Cantor was used to demonstrate that chromosomal multiplicity, a characteristic yet to be observed in a gamma-subclass bacterium, is common among B. cepacia strains. A derivative of Tn5 suitable for determining the chromosomal locations of various B. cepacia genes was also constructed

The CbrA-CbrB two-component regulatory system controls the utilization of multiple carbon and nitrogen sources in Pseudomonas aeruginosa.

A novel two-component system, CbrA-CbrB, was discovered in Pseudomonas aeruginosa; cbrA and cbrB mutants of strain PAO were found to be unable to use several amino acids (such as arginine, histidine and proline), polyamines and agmatine as sole carbon and nitrogen sources. These mutants were also unable to use, or used poorly, many other carbon sources, including mannitol, glucose, pyruvate and citrate. A 7 kb EcoRI fragment carrying the cbrA and cbrB genes was cloned and sequenced. The cbrA and cbrB genes encode a sensor/histidine kinase (Mr 108 379, 983 residues) and a cognate response regulator (Mr 52 254, 478 residues) respectively. The amino-terminal half (490 residues) of CbrA appears to be a sensor membrane domain, as predicted by 12 possible transmembrane helices, whereas the carboxy-terminal part shares homology with the histidine kinases of the NtrB family. The CbrB response regulator shows similarity to the NtrC family members. Complementation and primer extension experiments indicated that cbrA and cbrB are transcribed from separate promoters. In cbrA or cbrB mutants, as well as in the allelic argR9901 and argR9902 mutants, the aot-argR operon was not induced by arginine, indicating an essential role for this two-component system in the expression of the ArgR-dependent catabolic pathways, including the aruCFGDB operon specifying the major aerobic arginine catabolic pathway. The histidine catabolic enzyme histidase was not expressed in cbrAB mutants, even in the presence of histidine. In contrast, proline dehydrogenase, responsible for proline utilization (Pru), was expressed in a cbrB mutant at a level comparable with that of the wild-type strain. When succinate or other C4-dicarboxylates were added to proline medium at 1 mM, the cbrB mutant was restored to a Pru+ phenotype. Such a succinate-dependent Pru+ property was almost abolished by 20 mM ammonia. In conclusion, the CbrA-CbrB system controls the expression of several catabolic pathways and, perhaps together with the NtrB-NtrC system, appears to ensure the intracellular carbon: nitrogen balance in P. aeruginosa