scispace - formally typeset
Search or ask a question
Topic

Pseudomonas putida

About: Pseudomonas putida is a research topic. Over the lifetime, 6854 publications have been published within this topic receiving 230572 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: The results indicate that, depending on the reaction conditions, product formation could be directed to one specific product.
Abstract: During the last few decades, the microbial degradation pathways of aromatic and aliphatic hydrocarbons have received a lot of scientific interest because of the high potential of the enzyme systems involved for environmental (43) and preparative applications (38, 59). These pathways are usually initiated by an oxygenase-catalyzed chemo-, regio-, and stereoselective hydroxylation of the hydrocarbons, a reaction for which often no organic chemical counterpart is known (9, 13). The xylene degradation pathway of Pseudomonas putida mt-2 and its initiating oxygenase, the xylene monooxygenase (XMO), are among the best-studied examples of aromatic hydrocarbon degradation (5, 36, 57, 61). The enzymes for xylene degradation are encoded on a catabolic plasmid, the TOL plasmid pWW0. XMO is the first enzyme in the upper degradation pathway for toluene and xylenes, in which a carboxylic acid is formed (1, 16, 58). The upper pathway also involves benzyl alcohol dehydrogenase and benzaldehyde dehydrogenase, which catalyze the oxidation of benzyl alcohols via benzaldehydes to benzoic acids (46-48). The carboxylic acid is then transformed to substrates of the Krebs cycle through the meta cleavage pathway (10, 14, 36, 55). XMO consists of two polypeptide subunits, encoded by xylM and xylA (16, 52). XylA, the NADH:acceptor reductase component, is an electron transport protein transferring reducing equivalents from NADH to XylM (45). XylM, the hydroxylase component, is located in the membrane, and its activity depends on phospholipids and ferrous ion, with a pH optimum of 7 (44, 62). The substrate spectrum of XMO was investigated, with focus on preparative applications. XMO expressed in Escherichia coli oxidizes toluene and xylenes but also m- and p-ethyl-, methoxy-, nitro-, and chloro-substituted toluenes, as well as m-bromo-substituted toluene, to the corresponding benzyl alcohol derivatives (21, 65). Furthermore, styrene is transformed into S-styrene oxide with an enantiomeric excess (ee) of 95% (64, 65). The one-step oxygenation of styrene catalyzed by recombinant XMO in growing cells of E. coli was applied to produce S-styrene oxide on a 2-liter scale with hexadecane as the second organic phase (30). The wild-type strain P. putida mt-2 was used to oxidize methyl groups on aromatic heterocyclics to the corresponding carboxylic acids (20). In large-scale fermentations, a 5-methyl-2-pyrazinecarboxylic acid titer up to 20 g liter−1 was reached. This system exploits the inability of the wild-type strain to further degrade heteroaromatic carboxylic acids. In P. putida mt-2, all three enzyme activities of the upper xylene degradation pathway are responsible for the three-step oxidation. Early reports suggested that XMO also catalyzes alcohol and aldehyde oxidations (15, 16). Later, such activities were attributed to dehydrogenases present in the E. coli host (16, 44). Recently, we verified by in vivo experiments that XMO indeed catalyzes the oxidation of benzyl alcohols and benzaldehydes, both via a monooxygenation type of reaction (4). E. coli cells expressing XMO genes under the control of the alk regulatory system (12, 51, 62, 67) were used for these experiments. Potential preparative in vivo applications of XMO are hampered by low water solubilities and high toxicities of possible substrates and products, limiting the performance of aqueous systems. Nonconventional reaction media such as an aqueous-organic two-liquid-phase system are promising alternatives (8, 40). A second immiscible phase can act as a reservoir for substrate and products, regulating the concentration of such compounds in the biocatalyst microenvironment, minimizing toxicity and simplifying product recovery (24, 60, 63). In the present study, we characterized the multistep oxidation of substrates such as pseudocumene and toluene by whole cells of E. coli containing XMO with the aims of clarifying the natural role of such a multistep catalysis and identifying possible applications. The biotechnological conversion of pseudocumene is of special interest because a controlled regio- and chemospecific multistep oxidation of only one methyl group is difficult to achieve by purely chemical methods. We determined the kinetics of the one-enzyme multistep reaction and analyzed the whole-cell biocatalyst in a two-liquid-phase biotransformation on a 2-liter scale. Our results indicate that, depending on the reaction conditions, product formation may be directed to one specific product, either benzylic alcohols, aldehydes, or acids.

99 citations

Journal ArticleDOI
TL;DR: The present results offer insight on Plant Growth Promoting Rhizobacteria (PGPR), such as P. putida, for the potential to enhance the plant growth by inhibiting the adverse effects of Ni in E. sativa.

99 citations

Journal ArticleDOI
TL;DR: Evidence is presented that proteins with GGDEF and EAL domains are involved in the regulation of biofilm formation and biofilm dispersion in Pseudomonas putida, which supports the emerging theme that GGDEF-domain and Eal-domain proteins areinvolved in regulating the transition of bacteria between a roaming lifestyle and a sessile biofilm lifestyle.
Abstract: Microbial biofilm formation often causes problems in medical and industrial settings, and knowledge about the factors that are involved in biofilm development and dispersion is useful for creating strategies to control the processes. In this report, we present evidence that proteins with GGDEF and EAL domains are involved in the regulation of biofilm formation and biofilm dispersion in Pseudomonas putida. Overexpression in P. putida of the Escherichia coli YedQ protein, which contains a GGDEF domain, resulted in increased biofilm formation. Overexpression in P. putida of the E. coli YhjH protein, which contains an EAL domain, strongly inhibited biofilm formation. Induction of YhjH expression in P. putida cells situated in established biofilms led to rapid dispersion of the biofilms. These results support the emerging theme that GGDEF-domain and EAL-domain proteins are involved in regulating the transition of bacteria between a roaming lifestyle and a sessile biofilm lifestyle.

99 citations

Journal ArticleDOI
TL;DR: It is possible to produce PHA block copolymers of various kinds using the recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum, and the PHB-b-PHHx showed improved structural related mechanical properties.
Abstract: Block polyhydroxyalkanoates (PHA) were reported to be resistant against polymer aging that negatively affects polymer properties. Recently, more and more attempts have been directed to make PHA block copolymers. Diblock copolymers PHB-b-PHHx consisting of poly-3-hydroxybutyrate (PHB) block covalently bonded with poly-3-hydroxyhexanoate (PHHx) block were for the first time produced successfully by a recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. The chloroform extracted polymers were characterized by nuclear magnetic resonance (NMR), thermo- and mechanical analysis. NMR confirmed the existence of diblock copolymers consisting of 58 mol% PHB as the short chain length block with 42 mol% PHHx as the medium chain length block. The block copolymers had two glass transition temperatures (T g ) at 2.7°C and −16.4°C, one melting temperature (T m ) at 172.1°C and one cool crystallization temperature (T c ) at 69.1°C as revealed by differential scanning calorimetry (DSC), respectively. This is the first microbial short-chain-length (scl) and medium-chain-length (mcl) PHA block copolymer reported. It is possible to produce PHA block copolymers of various kinds using the recombinant Pseudomonas putida KT2442 with its β-oxidation cycle deleted to its maximum. In comparison to a random copolymer poly-3-hydroxybutyrate-co-3-hydroxyhexanoate (P(HB-co-HHx)) and a blend sample of PHB and PHHx, the PHB-b-PHHx showed improved structural related mechanical properties.

99 citations

Journal ArticleDOI
TL;DR: A more detailed view of the effect of toluene on the intracellular energy management of P. putida S12 is yielded and several novel leads have been obtained for further targeted investigations.
Abstract: The aim of this study was to assess the cellular response of the solvent-tolerant Pseudomonas putida S12 to toluene as the single effector. Proteomic analysis (two-dimensional difference-in-gel-electrophoresis) was used to assess the response of P. putida S12 cultured in chemostats. This approach ensures constant growth conditions, both in the presence and absence of toluene. A considerable negative effect of toluene on the cell yield was found. The need for energy in the defence against toluene was reflected by differentially expressed proteins for cell energy management. In toluene-stressed cells the balance between proton motive force (PMF) enforcing and dissipating systems was shifted. NAD(P)H generating systems were upregulated whereas the major proton-driven system, ATP synthase, was downregulated. Other differentially expressed proteins were identified: outer membrane proteins, transport proteins, stress-related proteins and translation-related proteins. In addition, a protein with no assigned function was found. This study yielded a more detailed view of the effect of toluene on the intracellular energy management of P. putida S12 and several novel leads have been obtained for further targeted investigations. © 2006 The Authors.

99 citations


Network Information
Related Topics (5)
Bacillus subtilis
19.6K papers, 539.4K citations
89% related
Bacteria
23.6K papers, 715.9K citations
88% related
Operon
14.6K papers, 768.6K citations
88% related
Yeast
31.7K papers, 868.9K citations
88% related
Escherichia coli
59K papers, 2M citations
87% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023184
2022345
2021182
2020246
2019226
2018206