Use of the λ Red-recombineering method for genetic engineering of Pantoea ananatis

<p>Abstract</p> <p>Background</p> <p><it>Pantoea ananatis</it>, a member of the <it>Enterobacteriacea </it>family, is a new and promising subject for biotechnological research. Over recent years, impressive progress in its application to L-glutamate production has been achieved. Nevertheless, genetic and biotechnological studies of <it>Pantoea ananatis </it>have been impeded because of the absence of genetic tools for rapid construction of direct mutations in this bacterium. The λ Red-recombineering technique previously developed in <it>E. coli </it>and used for gene inactivation in several other bacteria is a high-performance tool for rapid construction of precise genome modifications.</p> <p>Results</p> <p>In this study, the expression of λ Red genes in <it>P. ananatis </it>was found to be highly toxic. A screening was performed to select mutants of <it>P. ananatis </it>that were resistant to the toxic affects of λ Red. A mutant strain, SC17(0) was identified that grew well under conditions of simultaneous expression of λ <it>gam</it>, <it>bet</it>, and <it>exo </it>genes. Using this strain, procedures for fast introduction of multiple rearrangements to the <it>Pantoea ananatis </it>genome based on the λ Red-dependent integration of the PCR-generated DNA fragments with as short as 40 bp flanking homologies have been demonstrated.</p> <p>Conclusion</p> <p>The λ Red-recombineering technology was successfully used for rapid generation of chromosomal modifications in the specially selected <it>P. ananatis </it>recipient strain. The procedure of electro-transformation with chromosomal DNA has been developed for transfer of the marked mutation between different <it>P. ananatis </it>strains. Combination of these techniques with λ Int/Xis-dependent excision of selective markers significantly accelerates basic research and construction of producing strains.</p

Construction of stably maintained non-mobilizable derivatives of RSF1010 lacking all known elements essential for mobilization

<p>Abstract</p> <p>Background</p> <p>RSF1010 is a well-studied broad-host-range plasmid able to be mobilized to different bacteria and plants. RSF1010-derived plasmid vectors are widely used in both basic research and industrial applications. In the latter case, exploiting of mobilizable plasmids or even the plasmids possessing negligible mobilization frequency, but containing DNA fragments that could promote conjugal transfer, is undesirable because of biosafety considerations. Previously, several mutations significantly decreasing efficiency of RSF1010 mobilization have been selected. Nevertheless, construction of the RSF1010 derivative lacking all known loci involved in the conjugal transfer has not been reported yet.</p> <p>Results</p> <p>Novel non-mobilizable derivatives of RSF1010 lacking all known DNA sequences involved in the mobilization process have been obtained due to the exploiting of λRed-driven recombination between the plasmid and a constructed <it>in vitro </it>linear DNA fragment. To provide auto-regulated transcription of the essential replication gene, <it>repB</it>, the plasmid loci <it>oriT</it>, <it>mobC </it>and <it>mobA </it>were substituted by the DNA fragment containing P_{<it>lac</it>UV5}→<it>lacI</it>. Mobilization of the obtained RSFmob plasmid was not detected in standard tests. The derivative of RSFmob with increased copy number has been obtained after <it>lacI </it>elimination. High stability of both constructed plasmids has been demonstrated in <it>Escherichia coli </it>and <it>Pantoea ananatis</it>. Design of RSFmob allows easy substitution of P_{<it>lac</it>UV5}by any desirable promoter for construction of novel derivatives with changed copy number or host range.</p> <p>Conclusion</p> <p>Novel non-mobilizable derivatives of RSF1010 lacking all known DNA sequences involved in the mobilization process and stably maintained at least in <it>E. coli </it>and <it>P. ananatis </it>have been constructed. The obtained plasmids became the progenitors of new cloning vectors answering all biosafety requirements of genetically modified organisms used in scale-up production.</p

The complete genome sequence of Pantoea ananatis AJ13355, an organism with great biotechnological potential

Pantoea ananatis AJ13355 is a newly identified member of the Enterobacteriaceae family with promising biotechnological applications. This bacterium is able to grow at an acidic pH and is resistant to saturating concentrations of L-glutamic acid, making this organism a suitable host for the production of L-glutamate. In the current study, the complete genomic sequence of P. ananatis AJ13355 was determined. The genome was found to consist of a single circular chromosome consisting of 4,555,536 bp [DDBJ: AP012032] and a circular plasmid, pEA320, of 321,744 bp [DDBJ: AP012033]. After automated annotation, 4,071 protein-coding sequences were identified in the P. ananatis AJ13355 genome. For 4,025 of these genes, functions were assigned based on homologies to known proteins. A high level of nucleotide sequence identity (99%) was revealed between the genome of P. ananatis AJ13355 and the previously published genome of P. ananatis LMG 20103. Short colinear regions, which are identical to DNA sequences in the Escherichia coli MG1655 chromosome, were found to be widely dispersed along the P. ananatis AJ13355 genome. Conjugal gene transfer from E. coli to P. ananatis, mediated by homologous recombination between short identical sequences, was also experimentally demonstrated. The determination of the genome sequence has paved the way for the directed metabolic engineering of P. ananatis to produce biotechnologically relevant compounds

Construction of stably maintained non-mobilizable derivatives of RSF1010 lacking all known elements essential for mobilization-1

<p><b>Copyright information:</b></p><p>Taken from "Construction of stably maintained non-mobilizable derivatives of RSF1010 lacking all known elements essential for mobilization"</p><p>http://www.biomedcentral.com/1472-6750/7/80</p><p>BMC Biotechnology 2007;7():80-80.</p><p>Published online 21 Nov 2007</p><p>PMCID:PMC2200642.</p><p></p>e were analyzed. 1, 2, 3 – 0.5, 2.0 and 5.0 μl of the DNA probe isolated from clone 1 of MG1655/RSF1010; 4, 5 – 2.0 μl of the DNA probes isolated from clones 2 and 3 of MG1655/RSF1010; 6, 7, 8 – 2.0 μl of the DNA probes isolated from 3 independent clones of MG1655/RSFmob; 9, 10, 11 – 2.0 μl of the DNA probes isolated from 3 independent clones of MG1655/RSFmob-I. Relative copy number was calculated as the ratio of the DNA amounts in the upper bands (5.9 kb EcoRV-EcoRV fragment). Electrophoretic patterns for stationary phase are represented as an example