Chlorobenzoate inhibits growth and induces stress proteins in the PCB-degrading bacterium Burkholderia xenovorans LB400
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ORIGINAL PAPER
Chlorobenzoate inhibits growth and induces stress proteins in the PCB-degrading bacterium Burkholderia xenovorans LB400 Paula Martínez · Loreine Agulló · Marcela Hernández · Michael Seeger
Received: 23 November 2006 / Revised: 5 March 2007 / Accepted: 12 April 2007 / Published online: 24 May 2007 © Springer-Verlag 2007
Abstract Aerobic bacteria, such as Burkholderia xenovorans LB400, are able to degrade a wide range of polychlorobiphenyls (PCBs). Generally, these bacteria are not able to transform chlorobenzoates (CBAs), which accumulate during PCB degradation. In this study, the eVects of CBAs on the growth, the morphology and the proteome of Burkholderia xenovorans LB400 were analysed. 4-CBA and 2-CBA were observed to inhibit the growth of strain LB400 on glucose. Strain LB400 exposed to 4-CBA exhibited increased number and size of electron-dense granules in the cytoplasm, which could be polyphosphates. Twodimensional (2-D) polyacrylamide gel electrophoresis was used to characterise the molecular response of strain LB400 to 4-CBA. This compound induced the enzymes BenD and CatA of benzoate and catechol catabolic pathways. The induction of molecular chaperones DnaK and HtpG by 4-CBA indicated that the exposure to this compound constitutes a stressful condition for this bacterium. Additionally, the induction of some Krebs cycle enzymes was observed, probably as response to cellular energy requirements. This study contributes to the knowledge on
P. Martínez · L. Agulló · M. Hernández · M. Seeger (&) Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Departamento de Química, Millennium Nucleus of Microbial Ecology and Environmental Microbiology and Biotechnology, Universidad Técnica Federico Santa María, Av. España 1680, Valparaíso, Chile e-mail: [email protected] Present Address: P. Martínez Department of Bioremediation, Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318 Leipzig, Germany
the eVects of CBA on the PCB-degrader Burkholderia xenovorans LB400. Keywords Chlorobenzoate · Proteome · Burkholderia xenovorans · Stress Abbreviations CBAs Chlorobenzoates PCBs Polychlorobiphenyls 2-D Two-dimensional DNP 2,4-Dinitrophenol 2,4-D 2,4-Dichlorophenoxyacetic acid CFU Colony-forming units
Introduction CBAs are present in the environment mainly due to their production during partial biodegradation of chlorinated aromatic compounds, such as PCBs. Strain LB400 is able to convert diverse chlorinated biphenyls into CBAs (Bedard 1990; Seeger et al. 1995, 1997, 1999). Additionally, CBAs like 2,3,6-trichlorobenzoate or 2,5-dichloro-3-aminobenzoate have been used as pesticides (Swanson et al. 1969). Aerobic PCB-degrading bacteria generally are unable to transform CBAs, leading to accumulation of these metabolites. It has been observed that CBAs aVect the growth and PCB degradation rates in bacteria, like Comamonas testosteroni and Pseudomonas stutzeri (Sondossi et al. 1992; Vrana et al. 1996). Bacterial degradation of CBAs has been studied extensively (Pieper 2005). C
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